FieldSpec HandHeld 2 - User Manual

ASD Document 600860 Rev. A 1 FieldSpec® HandHeld2 User Manual ©2010 ASD Inc.

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FieldSpec® HandHeld 2™ Spectroradiometer User’s Manual

ASD Document 600860 Rev. A©2010 by ASD Inc.

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ASD Document 600860 Rev. A 2 FieldSpec® HandHeld 2™ User Manual ©2010 ASD Inc.

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Copyright Information

This document contains proprietary information protected by copyright law and may not be reproduced in any manner without the express written approval of ASD Inc.

Trademark Information ASD Inc. 2555 55th Street Suite 100 Boulder, CO 80301 USA Phone: (303) 444-6522 www.asdi.com Trademarks FieldSpec® HandHeld 2™ and RS3™ are registered the intellectual property of Analytical Spectral Devices, Inc. (ASD Inc.). All trademarks used or displayed in this material are the property of ASD, its affiliates, or third party owners. Unauthorized use of these trademarks is illegal and punishable by law. Nothing contained herein is to be construed as granting, by implication, estoppel, or otherwise, any license or right of use of any such trademark without the prior and express written permission of ASD, or such third party owner.

Disclaimer The information and specifications contained in this manual are subject to change without notice. ASD Inc. shall not be held liable for technical errors, editorial omissions, or errors made herein; nor for incidental or consequential damages resulting from furnishing, performance, or use of this material.


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Declaration of Conformity

According to IEC guide 22 and EN45014,

Manufacturers Name: ASD Inc.

Manufacturer’s Address: 2555 55th St, Suite 100, Boulder, CO 80301 USA

Declares that the product:

Product Name: FieldSpec® HandHeld 2™, FieldSpec® HandHeld 2™ Pro

Product Number: A103200, A103220

Product Options: None

Conforms to the following EU Directives:

Safety: Low Voltage Directive, 72/23/EEC, as amended by 93/68/EEC

EMC: Electromagnetic Compatibility Directive, 2004/108/EC

Supplementary Information:

The product complies with the requirements of the following Harmonized Product Standards and carries the CE-Marking accordingly:

EN61010-1: 1993, plus Amendment A2: 1995

Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory use

EN61326: 1997; plus Amendment A1:1998

Class A, Electrical Equipment for Measurement, control and Laboratory use-EMC Requirements

Signatures:

Name: Robert J. Faus

Title: Vice President of Engineering

Date: 01-26-2010

For compliance information ONLY, contact:

European Contact: The local ASD Representative

USA Contact: Product Regulations Manager, ASD Inc. 2555 55th St., Ste. 100, Boulder, CO 80301 USA Phone: (303) 444-6522


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Symbols – Definitions

CAUTION: Risk of danger. This is a personal danger warning. Documentation must be consulted in all cases where this symbol is marked. Failure to acknowledge these warnings could result in personal injury to the user.

CAUTION: Risk of Electric Shock. This is a personal danger warning. Documentation must be consulted in all cases where this symbol is marked. Failure to acknowledge these warnings could result in personal injury to the user.

CAUTION: Hot Surface. This is a personal danger warning. Documentation must be consulted in all cases where this symbol is marked. Failure to acknowledge these warnings could result in personal injury to the user.

RECYCLE: Items with this symbol indicate that the item should be recycled and not disposed of as general waste.

Warnings and cautions are placed throughout this manual for the convenience of the reader. However, the absence of warnings and cautions do not preclude the use of proper caution and handling. Usual precautions are recommended to be taken at all times, either written or otherwise, to avoid personal injury or damage to ASD equipment.


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Table of Contents

Copyright Information ............................................................................................................... 2

Trademark Information ............................................................................................................. 2

Disclaimer ............................................................................................................................... 2

Declaration of Conformity ......................................................................................................... 3

1. Getting Started ................................................................................................................. 9

1.1 Unpacking the Instrument ........................................................................................................ 9

1.2 Standard Accessories ........................................................................................................... 10

1.3 FieldSpec® HandHeld 2 Instrument Components .................................................................... 11

1.4 Holding and Mounting ........................................................................................................... 12

1.5 Install the Batteries or Attach the Power Supply ...................................................................... 13

2. Basic Operation .............................................................................................................. 16

2.1 Control and Display Panel ..................................................................................................... 16

2.2 Power On ............................................................................................................................ 17

2.3 Spectrum Display ................................................................................................................. 17

2.4 Choose Test Sample Illumination ........................................................................................... 18

2.5 View White Reference Panel .................................................................................................. 18

2.6 Saturation Alert .................................................................................................................... 19

2.7 Optimization ......................................................................................................................... 19

2.8 Dark Current and White Reference ......................................................................................... 21

2.9 Viewing a Reflectance Spectrum from the Sample ................................................................... 23

2.10 Viewing in Spectral Radiance or Irradiance .............................................................................. 24

2.11 Storing a Spectrum .............................................................................................................. 24

2.12 Laser Pointer ....................................................................................................................... 24

2.13 Data Export ......................................................................................................................... 25

2.14 Main Menu ........................................................................................................................... 25

2.14.1 System Presets ................................................................................................................ 26

2.14.2 Foreoptic Menu ................................................................................................................ 27

2.14.3 Integration Time Menu....................................................................................................... 29

2.14.4 Spectrum Counts Averaging Menu ..................................................................................... 31

2.14.5 File Save Menu ................................................................................................................. 34

3. External Computer Access & Control (Tethered Mode) ............................................................ 48


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3.1 Connect Computer to the FieldSpec® HandHeld 2 Instrument .................................................. 48

3.2 ASD Application Software Installation ..................................................................................... 49

3.3 ASD Application Software/Hardware Combinations ................................................................. 52

3.4 Running the RS3 Software ..................................................................................................... 53

3.5 RS3 GPS .............................................................................................................................. 55

3.6 RS3 Foreoptics ..................................................................................................................... 55

3.7 RS3 Saturation Alert .............................................................................................................. 55

3.8 RS3 Optimization ................................................................................................................... 56

3.9 RS3 White Reference ............................................................................................................. 57

3.10 RS3 Dark Current .................................................................................................................. 58

3.11 RS3 Pull-down menus ............................................................................................................. 59

3.12 RS3 Display Pull-down Menu ................................................................................................... 59

3.12.1 RS3 Axis Settings .............................................................................................................. 60

3.12.2 RS3 Cursor Settings .......................................................................................................... 61

3.12.3 RS3 Grid Settings .............................................................................................................. 63

3.12.4 RS3 Graph Line Properties Settings .................................................................................... 64

3.12.5 RS3 View Files Settings ...................................................................................................... 65

3.12.6 RS3 Freeze Display Settings ............................................................................................... 66

3.12.7 RS3 Quit Command ........................................................................................................... 67

3.13 RS3 Control Pull-Down Menu ................................................................................................... 67

3.13.1 RS3 Radiometric Measurement Command ........................................................................... 67

3.13.2 RS3 Adjust Configuration Settings ....................................................................................... 68

3.13.3 RS3 Absolute Reflectance Settings ...................................................................................... 69

3.13.4 RS3 Saving Spectra ........................................................................................................... 70

3.14 ViewSpec Pro Post Processing Application Software ............................................................... 71

3.15 HH2 Sync Application Software ............................................................................................. 72

3.15.1 Import Data Files From HandHeld 2 Instrument To Computer................................................ 76

3.15.2 HandHeld 2 Instrument Presets and Filenames .................................................................... 78

3.15.3 Export Calibration Files to HandHeld 2 Instrument ............................................................... 84

4. White Reference Details ................................................................................................... 85

4.1 Reflectance White Reference ................................................................................................. 85

4.2 Spectralon® ........................................................................................................................ 86

4.3 Transmittance White Reference ............................................................................................. 87


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5. Optional Accessories ....................................................................................................... 88

5.1 Fiber Optic Jumper Cables and Pistol Grip .............................................................................. 88

5.2 Foreoptics ........................................................................................................................... 90

5.3 Foreoptics for Irradiance Measurements ................................................................................ 91

5.4 Illumination Sources ............................................................................................................. 92

5.5 Contact Probes .................................................................................................................... 92

5.6 Integrating Sphere ................................................................................................................ 93

5.7 GPS .................................................................................................................................... 93

6. Theory and Measurements ............................................................................................... 94

6.1 Light ................................................................................................................................... 94

6.2 Light and Matter Interaction................................................................................................... 96

6.3 Light Energy ........................................................................................................................ 97

6.4 HandHeld 2 instrument Detection ......................................................................................... 100

6.5 Radiance, Irradiance and Wavelength Calibrations ................................................................. 101

6.6 Illumination Geometry ......................................................................................................... 103

6.7 Illumination Energy Characteristics ....................................................................................... 106

6.8 Field-of-View ....................................................................................................................... 107

6.9 Reflectance Calculations ..................................................................................................... 110

6.10 Reflectance Measurements ................................................................................................. 110

6.11 Reflectance Measurement Devices ...................................................................................... 113

6.12 Transmittance Calculations ................................................................................................. 114

6.13 Transmittance Measurements.............................................................................................. 115

6.14 Transmittance Measurement Devices ................................................................................... 116

6.15 Solar Illumination Measurements .......................................................................................... 118

6.16 Spectral Measurements ...................................................................................................... 119

6.17 Terminology ....................................................................................................................... 119

7. Maintenance & Trouble Shooting .................................................................................... 127

7.1 AC/DC Power Supply, Batteries and Charger ........................................................................ 127

7.2 Care and Cleaning of Spectralon® ....................................................................................... 127

7.3 Care and Cleaning of HandHeld 2 Instrument ........................................................................ 128

7.4 Care and Cleaning of HandHeld 2 Optical Input and Foreoptics ............................................... 129

7.5 Care and Cleaning of the Laser Pointer ................................................................................ 129

7.6 Care and Cleaning of Optional Fiber Optic Jumper Cables ...................................................... 130


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7.7 Care of Optional Light Sources ............................................................................................ 131

7.8 Temperature Effects ........................................................................................................... 131

7.9 W.E.E.E. Compliance .......................................................................................................... 131

7.10 Annual Factory Maintenance ................................................................................................ 131

7.11 Sending Instrument to ASD for Service ................................................................................. 132

7.12 Technical Support .............................................................................................................. 132

7.13 Trouble Shooting ................................................................................................................ 132

8. Specifications for Instrument, Computer, and Accessories ................................................ 135

8.1 FieldSpec® HandHeld 2 Specifications ................................................................................ 135

8.2 Optional External Controller Computer Specifications ............................................................ 136

8.3 Optional GPS Specifications ................................................................................................ 136

8.4 Non-ASD Software .............................................................................................................. 137

8.5 Artificial Light Sources ........................................................................................................ 137

Appendix A .......................................................................................................................... 138


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1. Getting Started

This section covers:

• Procedures and precautions for unpacking the instrument • Checking the included standard accessories • Identifying components of the instrument • Holding and mounting the instrument • Installing the batteries or power supply

1.1 Unpacking the Instrument

Inspect the shipping container and take photographs and careful notes regarding any damage that might have occurred during shipping (Figure 1).

Note: Save all packing materials, foam spacers, and paperwork for possible future use.

Step 1: Prepare a clear space on a sturdy bench or counter, ideally, a space near a wall-current receptacle.

Step 2: Remove the Pelican high-impact travel case from the shipping box.

Step 3: Open the Pelican high-impact case and remove the instrument and accessories, making note of the locations where the items are located in the case.

Figure 1: Unpack the items


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1.2 Standard Accessories

Check that all the items are included before using the FieldSpec® HandHeld 2 instrument (Figure 2).

1

2

3

4

5

6

7

8

9

Figure 2: HandHeld 2 and Standard Accessories

1. HandHeld 2 instrument 2. Handle 3. 4 rechargeable NiMH AA Batteries 4. 2 GB (min.) USB Flash Drive which includes electronic copies of the following

documents and software: User Manual, RS3 Software, ViewSpec Pro Software, and HH2 Sync Software

5. 3.6" Round White Reference Panel 6. AC/DC Power Supply 7. USB cable 8. Case with foam cut-outs (meets airline carry-on baggage specifications) 9. Battery Charger

If an optional fiber optic cable was purchased, please be careful unpacking and re-packing the cable. See details on handling a fiber optic jumper cable in the Section 7.6 Care and Cleaning of Optional Fiber Optic Jumper Cables.

Note: Optional fiber optic jumper cable should never be stored for long periods of time with a bend diameter of less than five inches. The cable can become damaged with undetectable fractures that can cause decreased signal.


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1.3 FieldSpec® HandHeld 2 Instrument Components

1 Optical input 8 Jack for optional remote trigger 2 Laser pointer 9 5 Volt DC Power Input* 3 Threads for handle or optional tripod 10 Display Panel (Swivel Hinged) 4 Trigger connection (for the Handle) 11 Battery compartment for 4 AA

Rechargeable Batteries 5 USB Mini-B for tethered mode only,

controlled by optional computer 12 Mounting threads for optional

spotting scope 6 USB A (female) 13 Thumb trigger button (red) 7 USB A (female) 14 Hand strap

*Switches power from batteries to AC/DC when connected to AC/DC power supply

10

13

14

12

Figure 3: Front, side and bottom

Figure 4: Back


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1.4 Holding and Mounting The HandHeld 2 instrument can be held using the hand strap, handle or an optional tripod.

• To use the hand strap insert hand (Figure 5) and adjust the strap (Figure 6).

Figure 5: Hand strap Figure 6: Adjust strap

• The handle can be attached in either of two orientations (Figure 7).

Figure 7: HandHeld 2 instrument handle attachment orientations

The connector cover attaches to the handle and must be installed to complete the circuit which allows the trigger on the handle to be used instead of the thumb trigger button. When the handle is in use, the cover also maintains the condition of the unused contacts. The HandHeld 2 instrument can also be mounted on a tripod using the 1/4-20 threaded hole on the underside of the instrument (Figure 8). The tripods are optional accessories available from ASD, Inc.

Handle

Connector Cover


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Figure 8: HandHeld 2 instruments mounted on tripods

1.5 Install the Batteries or Attach the Power Supply

Note: Before using the AC/DC Power Supply, batteries, or battery charger, read all following precautions.

AC/DC Power Supply: To reduce risk of burns, fire, electric shock or injury to persons or animals:

1. The AC/DC power supply is intended for Indoor Use Only. Do not use outdoors. 2. A power supply should never be left unattended when plugged in. Always unplug

the power supply from the main socket immediately after using. 3. Do not allow to be used as a toy. Pay close attention when this power supply is

used by, or near to, children. 4. Use only attachments recommended by the manufacturer. 5. Never operate the power supply if it has a damaged cord or plug, if it has been

dropped or damaged or if it has fallen into water. In such cases return the power supply to an authorized dealer or service center for examination or repair.

6. Never drop or insert an object into any openings. 7. Do not operate where aerosol (spray) products are being used or where oxygen

is being administered. 8. The power supply should be used near to a convenient and easily accessible main

socket.


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Step 1 Open the battery door by pushing down on the latch (Figure 9).

Step 2 Follow the polarity instructions stamped in the housing (Figure 10) and insert the

four AA batteries. If using rechargeable batteries, fully charge the batteries before using them the first time.

Step 3 Close the battery door.

Note: Once replacement becomes necessary, be sure to turn off the HandHeld 2 instrument before removing the batteries.

Figure 10: Battery polarity

An AC/DC Power Supply is included with the HandHeld 2 system (Figure 11). This power supply may be used instead of batteries to power the HandHeld 2 instrument from an AC outlet. Plug the AC/DC Power Supply into an AC outlet and connect the cable from the power supply into the socket on the instrument. Notice that the notches in the instrument power plug socket must receive the posts of the power plug in a specific orientation (Figure 12).

Note: Use only ASD approved power supplies and connectors to power the instrument.

Battery compartment with latch

Figure 9: Battery door


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Figure 11: AC/DC power supply

Figure 12: Notched power plug socket and posts on power plug


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2. Basic Operation There are two ways to control the FieldSpec® HandHeld 2 instrument and collect data:

Standalone Mode— This mode uses only the internal control and data collection capabilities of the HandHeld 2.

Tethered Mode— This mode combines the capabilities of the HandHeld 2 with the power of an optional external controller computer.

If using the HandHeld 2 instrument for the first time, start with the standalone mode. This mode is the fastest and easiest way to make measurements. In this first run, all settings will be defined by the default system preset, mentioned in sections 2.13 and 3.5.

2.1 Control and Display Panel

HandHeld 2 Display

1 Power Indicator LED 2 ON/OFF Button 3 LCD Display 4 Laser Pointer ON/OFF 5-8 Menu Buttons 9 Thumb Trigger Button (red)

1 2

3

4

5 6 7 8

9


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2.2 Power On Before powering on the HandHeld 2 instrument, ensure that the batteries are fully charged and installed or that the AC/DC Power Supply is connected to the instrument and plugged into a working outlet.

To power on the HandHeld 2 instrument, press the on/off button (Figure 13). The small LED above the on/off button will illuminate when powered on. After a few seconds, the ASD logo will appear and it will stay on for about 30 seconds while the system boots.

2.3 Spectrum Display After about 30 seconds the spectrum display mode should appear (Figure 14). When the HandHeld 2 is aimed at a lamp or brightly illuminated surface, the curve will move on the display screen. If the light is too bright for the present settings, the curve will go above the display scale and SATURATION ALERT will be displayed. Saturation alert is described in Section 2.6.

If the menu button is hit by accident and icons appear, press the EXIT button to return to the spectrum display view (Figure 15).

Figure 13: On/off button

Figure 14: Spectrum display


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2.4 Choose Test Sample Illumination If the HandHeld 2 is being used for the first time, start with measurements outdoors, using the solar illumination. Do not attach any foreoptics (just use the bare optical input of the HandHeld 2). This scenario is the fastest and easiest way to make measurements. If foreoptics are used later on, be sure to set the Foreoptic menu to the correct foreoptic before taking any measurements (Section 2.15 Foreoptic Menu).

If the sky is cloudy, it is night time, or if working indoors, set up a suitable DC-powered tungsten quartz halogen lamp, such as ASD’s Pro Lamp system.

2.5 View White Reference Panel Choose a suitable white reference panel, such as the three inch round white reference panel which comes standard with the HandHeld 2 instrument or the five inch square panel (sold separately). Hold or mount the panel so that it is level and fully illuminated.

Aim the HandHeld 2 instrument so that optical input is viewing—but not shading—the white reference panel and is still close enough to ensure the field-of-view is filled by the panel (Figure 16). For a five inch square panel, keep the distance within nine inches. For a three inch round panel, keep the distance within four inches. Dark clothing helps minimize light reflected from the operator. (See section 6.10 for more information on white reference.)

Note: The diameter of the spot size is approximately half of the height.

Figure 16: Aim the HandHeld 2 instrument at the white reference panel

Figure 15: Exit to return to Spectrum Display


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With the HandHeld 2 instrument viewing the white reference panel, a curve—called a raw DN spectrum—is displayed, signified by D on the Y axis (Figure 17). Raw DN is the raw output of the detector converted to digital numbers.

This display updates in real-time. As the HandHeld 2 instrument views different illumination levels or different surfaces, the curve on the display will change.

2.6 Saturation Alert If the light is too bright for the present settings, the curve will go above the display scale and SATURATION ALERT will be displayed (Figure 18). If this warning appears, the model must be optimized as discussed in Section 2.7 Optimization.

2.7 Optimization Optimization should be updated when illumination changes significantly or when the instrument software gives a saturation alert. If the relative reflectance of the reference panel is greater than one, optimization is recommended. Optimization has no effect on the results unless the data has drifted towards saturation, in which case optimization is mandatory.

A well-optimized instrument will display between 20,000 and 35,000 raw digital numbers. Ideally, the peak of the raw digital numbers curve should be three quarters of full scale while the HandHeld 2 instrument is viewing the white reference panel. If the peak of the raw digital

Figure 17: Raw DN spectrum

Figure 18: Saturation alert


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numbers curve is too high (saturated) or too low, press the OPT (optimization) button (Figure 19). This function will help find the ideal integration time in order to maximize the signal-to-noise ratio without saturation.

• Refer to 2.17 Integration Time Menu to perform this task manually.

When prompted by the “Push trigger to optimize” message (Figure 20), point the HandHeld 2 instrument at the white reference panel—carefully following all directions and precautions listed in Section 2.5—and press the thumb trigger button (Figure 21).

Figure 21: Press thumb trigger to optimize

Figure 19: OPT button

Figure 20: Optimization prompt


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Keep pointing the HandHeld 2 instrument at the panel until the process is completed, which is indicated by an updated raw DN spectrum.

2.8 Dark Current and White Reference In order to collect reflectance spectra, the HandHeld 2 instrument must first establish a baseline measurement by calculating both the dark current (DC) and white reference (WR). Step 1 Follow the same protocol as listed in 2.5 for viewing a white reference panel

(Figure 22).

Step 2 While the HandHeld 2 instrument is viewing the white reference panel, press the DC/WR button (Figure 23).

Step 3 When prompted by the “Push trigger to collect white” message, (Figure 24) point the HandHeld 2 at the white reference panel—so that the field-of-view is within the panel area.—and press the thumb trigger button (Figure 25).

Field-of-view

Figure 23: DC/WR button

Figure 22: View of white reference panel


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Figure 25: Push thumb trigger button for white reference

Step 4 The “Performing Baseline” message indicates that the dark current and white reference are being measured and recorded (Figure 26). A clicking sound indicates that the internal shutter has closed to collect dark current. Another click indicates it is opening to collect the white reference measurement. Keep the HandHeld 2 instrument steady and pointed at the white reference panel during the entire time that the “Performing Baseline” message is displayed.

When this process is finished, the HandHeld 2 display will switch to reflectance.

Figure 24: White reference prompt

Figure 26: Performing baseline


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The spectrum on the display screen should be a straight line at a value of 1 across the wavelength range (Figure 27).

There may be a little noise at the low end due to low energy from the sun or illumination source in this region, as well as a loss of energy absorbed in the atmosphere.

2.9 Viewing a Reflectance Spectrum from the Sample Similarly to the white reference setup, aim the HandHeld 2 to view a sample and ensure that it is close enough to fill the field-of-view with the sample. Avoid shadowing the viewed surface (Figure 28).

Figure 28: View of sample

The screen now displays a reflectance spectrum of the sample (Figure 29).

Note: While aiming at the sample, the spectrum is displayed, but not stored. See 2.10 in order to store the spectrum.

Figure 27: White reference baseline spectrum


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2.10 Viewing in Spectral Radiance or Irradiance If a radiance calibration was purchased, the display may be switched to viewing in radiance by pressing the Y-Mode button until the Y axis shows E for energy. If an optional cosine collector foreoptic was purchased, attach the foreoptic and switch the Y-Mode to E.

2.11 Storing a Spectrum

Depress the red thumb button (to the right of the screen) to store a spectrum to the internal memory of the HandHeld 2 instrument. Each spectrum file is about 30 kilobytes, and the HandHeld 2 instrument can store up to 2,000 files.

2.12 Laser Pointer Press the Laser button to turn on the laser pointer just below the instrument optical input (Figure 30).

The laser will come on for approximately five seconds and then go off—the laser on time can configure in order to fit specific needs. The laser will turn off as soon as the thumb trigger

Figure 29: Sample spectrum

Figure 30: Laser pointer


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button is pressed. The laser must be off during spectrum collection to prevent the intense laser light from becoming a source of noise in the spectrum.

2.13 Data Export A computer is used to import and process the stored data files from the HandHeld 2 instrument (optional notebook computers are available from ASD). Refer to section 3 External Computer Access & Control (Tethered Mode) for instructions on connecting the HandHeld 2 instrument to a computer and installing the ASD Application software, which is located on the USB flash drive included with the HandHeld 2 instrument.

2.14 Main Menu To access the Main Menu screen, press the MENU button (Figure 31).

The Main Menu screen is displayed (Figure 32).

Figure 32: Main Menu

Figure 31: Menu button


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The main menu contains five icons:

System Presets – Allows selection of a system preset group.

Foreoptics – Allows selection of a foreoptic.

File Save – Enables access to the File Save menu.

Integration Time – Allows selection of system integration time.

Spectrum Counts – Allows user to select white reference, dark current and spectrum sample counts.

The selection of an icon is indicated by a black box around the icon (Figure 33). Use the left and right navigation keys to change icon selection. Navigate to System Presets.

2.14.1 System Presets Step 1 Press the SEL (select) button to open the System Presets Menu (Figure 34).

Figure 33: Move selection box with arrow button

Figure 34: Press SEL button for System Presets


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Step 2 Press the up and down arrow buttons to select the Preset Group labeled DefaultSet (Figure 35). Other user defined settings will be discussed in Chapter 3 External Computer Access & Control (Tethered Mode).

Step 3 Press the SEL button (Figure 36). (Or cancel out of the screen with no changes by pressing the CANC button.)

2.14.2 Foreoptic Menu The HandHeld 2 bare optical input has a 25 degree full conical angle field-of-view. Optional foreoptics are available for limiting the field-of-view to smaller angles and for collecting full hemispherical irradiance. These optional foreoptics screw onto the front of the bare optical input. Before making any measurements, it is essential to follow the directions below and select the foreoptic presently in use on the HandHeld 2 instrument, or to select “Bare Fiber” for no attached foreoptic. Step 1 Press the left and right arrow buttons to move the Main Menu selection box to the

Foreoptic icon (Figure 37).

Figure 35: Use up and down arrow buttons

Figure 36: Press SEL button for DefaultSet


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Step 2 Press the SEL select button to open the Foreoptic menu (Figure 38).

Step 3 For the first time using the HandHeld 2, press the up or down arrow buttons to select the Bare Fiber configuration, which means that no foreoptic is attached (Figure 39).

Figure 39: Choose foreoptic

Figure 37: Press arrow buttons to move selection box to foreoptic menu

Figure 38: Press SEL button to open foreoptic menu


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Step 4 Press the SEL button (Figure 40). (Or cancel out of the screen with no changes by pressing the CANC button.)

2.14.3 Integration Time Menu

Integration time is the set time interval for detector build-up of electric signal converted from the incoming light. After each build-up, the electric signal is read and cleared-out for the next build-up.

The optimization function automatically selects the integration time. However, the integration time can be set manually. In some instances, this may improve the signal-to-noise ratio. Step 1 Press the left and right arrow buttons to move the selection box to the Integration

Time menu icon (Figure 41).

Step 2 Press the SEL button. The file save menu is shown with its submenu icons (Figure 42).

Figure 40: Select Bare Fiber

Figure 41: Integration Time menu icon


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Step 3 Press the up and down arrow buttons to move the selection box to the integration time (Figure 43).

Note: The peak of the raw DN curve should be three quarters of full scale while the HandHeld 2 instrument is viewing the white reference panel. If the peak DN is too low, adjust the integration time for a slower setting. If the peak DN is too high (saturated), adjust the integration time for a faster setting.

Step 4 Press the SEL button (Figure 44).

Figure 42: Integration time manual selection

Figure 43: Choose an integration time

Figure 44: Press SEL button to set integration time


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2.14.4 Spectrum Counts Averaging Menu

The signal-to-noise ratio improves with the square root of the number of scans used in the averaging.

• When outside, it is usually sufficient to use 30 scans in the spectrum averaging for the sample and 60 scans for the white reference and dark current. The white reference and dark current are not taken as often as the sample measurement, so one should increase their averaging to optimize signal-to-noise.

• When inside using artificial illumination, one can use lower averaging to achieve similar signal-to-noise results.

The actual spectrum average will be a compromise between noise reduction through spectra averaging and the time required for each spectra collection. For instance, if the instrument is being used in the field to measure a large number of samples, a smaller number of spectra are desirable in the average in order to decrease the collection time required. If collecting spectra in the lab, increase the number of spectra in the averaging to obtain the cleanest spectra possible.

If signal levels are low, the only way to increase the signal-to-noise ratio is by reducing noise through spectrum averaging. However, spectrum averaging takes more time per spectrum. The drawback to this is that the resultant data can be compromised by introducing low-frequency noise factors, such as varying cloud conditions or sudden gusts of wind changing the color of the tree canopy. To reduce the effects of low-frequency noise conditions—like those found outdoors—we recommend taking multiple spectra with spectrum averaging set to 10-25, then further average those spectra in post-processing using the ViewSpec program. ViewSpec also permits viewing large groups of files.

Step 1 Press the left and right arrow buttons to move the selection box to the Spectrum Counts menu icon (Figure 45).

Figure 45: Move selection box to Spectrum Counts menu icon


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Step 3 Press the left or right arrow buttons to move the selection box to the icons: White

for white reference averaging count, Dark for dark current averaging count, or Sample for sample averaging count (Figure 47).

Note: In the quotients below, s is sample, d is dark current, and w is white reference. The quotients are menu labels which demonstrate the calculation of each of the spectrum averages. For example, in order to compute the white reference averaging count, the equation is (sample minus dark current) divided by (white reference minus dark current). To simplify this, the letter representing the proper spectrum averaging count is highlighted in red, making it is clear that the first equation refers to the white reference averaging count, etc.

Figure 47: Move selection box to White, Dark, or Sample


Note: The default settings are from the System Presets (Section 3). However, these presets can be overridden from this menu.

Figure 46: Select Spectrum Counts menu icon


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Step 5 Press the left pointing arrow to move to the desired number position. If it is necessary to return to the first character position, press the right arrow button repeatedly (Figure 49).

Step 6 Press the up or down arrow buttons to change the numbers (Figure 50). Ten spectrum averaging is convenient in terms of measurement speed, however a higher number might be called for depending upon illumination and target reflectance.

Figure 48: Select White, Dark, or Sample counts

Figure 49: Move selection box to number position

Figure 50: Set the count numbers


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Step 7 When finished, press the SEL button (Figure 51) to return to the Spectrum Counts submenu.

Step 8 Press the EXIT button to return to the main menu (Figure 52).

2.14.5 File Save Menu Step 1 Press the left or right arrow buttons to move the Main Menu selection box to the

File Save Menu icon (Figure 53).

Figure 51: Return to the Spectrum Counts submenu

Figure 52: Exit to Main Menu

Figure 53: Move selection box to File Save menu


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Step 2 Press the SEL button to select the File Save Menu (Figure 54).

The File Save Menu display shows various submenus (Figure 55).

The File Save Menu contains five submenu icons:

Base Name – Allows selection of a base name for sequential spectrum saves. The number suffix will automatically increment with each spectrum save so each spectral file has a unique file name. For example, using the base name, “Spectrum”: Spectrum00000 Spectrum00001, Spectrum00002, etc.

Start Index – Allows the selection of starting index number for spectrum saves. In the above examples, the index numbers are the numerals following the base names.

Number to Save – Allows the selection of the number of spectra to save each time the red collect button is depressed.

Save Interval – Allows the selection of the spectrum save interval.

System – Enables access to the System Menu.

Figure 55: File Save submenus

Figure 54: Select the File Save Menu


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Open an Existing Base name Step 1 Press the left or right arrow buttons to move the selection box to the desired

submenu, for example, start with the Base Name submenu (Figure 56).

• Refer to Section 3.28 HandHeld 2 Instrument Presets and Filenames for an easier way to customize base names.

Step 2 To open an existing base name, press the SEL button (Figure 57).

Step 3 Press the up or down arrow keys to move the selection box. If this is the instrument’s first time in use, select a default name, for example, “Spectrum” (Figure 58).

Note: To create a new base name, skip to the next sequence of steps.

Figure 56: Move selection box to the Base Name icon

Figure 57: Select the Base Name icon

Figure 58: Move box to Spectrum


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Step 4 Press the SEL button to select the name (Figure 59).

Create a New Base Name Step 1 To create a new base name, select Base Name from the File Save submenu and

press the up or down arrow keys to move the selection box to <NEW> (Figure 60).


Figure 59: Select 'Spectrum'

Figure 60: Move selection box to <NEW>

Figure 61: Select <NEW>


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Step 3 A filename may be up to eight characters long and it may not contain spaces. Press the up or down arrow buttons for changing the first character (Figure 62).

Step 4 Press the right arrow button to move to the next character position (Figure 63).

Step 5 Press the right arrow button to the subsequent character positions and enter the characters with the up or down arrows (Figure 64).

Step 6 If it is necessary to return to the first character position, press the right arrow button repeatedly.

Figure 62: Set first character of filename

Figure 63: Move to next letter position

Figure 64: Enter the other letters


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Step 7 Press the SEL button when finished entering the name (Figure 65).

Step 8 Press the SEL button to set the new name as the filename for the spectral files (Figure 66). This step will also return the File Save submenus.

Starting ID Step 1 Press the left or right arrow buttons to move the selection box to the Starting ID

icon (Figure 67).

Figure 65: Press SEL button when name is complete

Figure 66: Press SEL to select new name

Figure 67: Move selection to Starting ID


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Step 3 Press the left pointing arrow to move to the desired number position. If it is necessary to return to the first character position, press the right arrow button repeatedly (Figure 69).

Step 4 Press the up or down arrow buttons to set the numbers (Figure 70).

Figure 68: Starting ID

Figure 69: Start index number adjustment

Figure 70: Set starting index number


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Step 5 When finished, press the SEL button to go back to the File Save submenus menu (Figure 71).

Number to Save

Step 1 Press the left and right arrow buttons to move the selection box to the Number To Save icon, which sets the number of files that are to be saved each time the thumb trigger button is pressed (Figure 72).


Figure 71: Press SEL to finish starting index

Figure 72: Move selection to Number to Save

Figure 73: Press SEL button for Number to Save


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Step 3 Press the left pointing arrow to move to the desired number position and press the up and down arrows to change the number (Figure 74).

Note: For most situations, this should be set to one. If collecting measurements automatically, adjust both this and the save interval—see section 2.16.4 If manually calculating the spectrum average, this can also be set to a value greater than one.

Step 4 When finished, press the SEL button (Figure 75), which will bring up the File Save submenu.

Save Interval

Step 1 Press the left and right arrow buttons to move the selection box to the Save Interval icon—which sets the time interval between saves for the previous Number to Save setting—and press the SEL button (Figure 76).

Figure 75: Press SEL for Number to Save

Figure 74: Adjust Number to Save


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Step 2 Although this should initially be set at 0, the number can be changed pressing the left pointing arrow to move to the desired number position, use the up and down arrow buttons to set the numbers. If it is necessary to return to the first character position, press the right arrow button repeatedly (Figure 77).

Step 3 When finished, press the SEL button to go back to the File Save submenus (Figure 78).

Figure 76: Save interval

Figure 78: Adjust Save interval and SEL

Figure 77: Adjust Save interval numbers


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System Menu

Press the left and right arrow buttons to move the selection box to the System Menu icon and press the SEL button (Figure 79).

The System Menu contains three submenu icons:

Set Clock – Allows the user to set the internal system clock.

Software Version – Displays the current software version.

Update Software – Updates the HandHeld 2 software upon command.

Set Clock

Step 1 Press the left and right arrow buttons to move the selection box to the Set Clock icon and press the SEL button (Figure 80).

Figure 79: System menu

Figure 80: Set clock


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Step 3 Press the SET button to set the time (Figure 81).

Step 4 Press the up and down arrow buttons to move the selection box to the current month and press the SEL button (Figure 82).

Step 5 Press the up and down arrow buttons to move the selection box to the current date and press the SEL button (Figure 83).

Figure 83: Set date

Step 6 Press the up and down arrow buttons to move the selection box to the current

year and press the SEL button (Figure 84).

Figure 81: Set system time

Figure 82: Set month


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Step 7 Press the up and down arrow buttons to move the selection box to the current hour and press the SEL button.

Step 8 Press the up and down arrow buttons to move the selection box to the current minute and press the SEL button (Figure 85). (To cancel with no changes press the CANC button.)

Software Version

Step 1 Press the left and right arrow buttons to move the selection box to the Software Version icon and press the SEL button to view the software version (Figure 86). Press OK to exit the screen.

Figure 84: Set year

Figure 85: Set minute

Figure 86: Inquire software version


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Update Software

Step 1 Download the software update from the ASD Support site and save it at the root directory level onto a (four GB or less) flash drive.

Note: If the update is saved within a folder, it will be inaccessible to the HandHeld 2.

Step 2 Plug the flash drive into the HandHeld 2 USB port.

Step 3 Press the left and right arrow buttons to move the selection box to the Update Software icon and press the SEL button (Figure 87).

Step 4 When prompted, press the OK button for the update to occur (Figure 88).

Figure 87: Update Software

Figure 88: Firmware Update prompt


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3. External Computer Access & Control (Tethered Mode) A computer is used to import and process the data files stored on the FieldSpec® HandHeld 2 instrument, to create system presets, and to export instrument control files. The HandHeld 2 can be operated with an external computer to take advantage of the large screen, keyboard and data storage directly to the computer hard drive (optional notebook computers are available from ASD at additional cost). When using the software with the included USB drive and USB cable, the HandHeld 2 can be operated in “Tethered Mode”.

• Refer to Section 8.2 for computer specifications

3.1 Connect Computer to the FieldSpec® HandHeld 2 Instrument

Ensure that both the HandHeld 2 instrument and the computer are powered from either fully charged batteries or AC/DC power supplies. Connect the USB cable, supplied with the HandHeld 2, between the instrument and computer by inserting the Mini-USB connector in the UBS input on the HandHeld 2 and inserting the standard USB connector to a computer (Figures 89 and 90).

Figure 89: Mini USB plug connects to the instrument

Figure 90: Standard USB plug connects to a computer


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3.2 ASD Application Software Installation If there are any previous versions of ASD software on the computer, remove those versions with the Add or Remove Programs tool in the control panel. (If necessary, save all data and instrument configuration files to an archive for later use.)

3.2.1 Windows 7 Setup Step 1 Insert the USB flash drive that came with the HandHeld 2 into a USB port on the

computer. View the contents of the USB flash drive, which should include various software installation files (Figure 91). Double click on the file ProductInstall.exe.

Figure 91: Files on USB drive

Step 2 The introduction screen lists several files to be installed on the computer (Figure 92). Install RS3 by following the prompts of the installer (Figure 93).

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3.2.2 Windows 7 User Setup RS3 requires a user to have read, write and execute permissions to operate the software. Permissions can be accomplished in two ways: Create a user with Administrator rights or create a standard user and provide read, write and execute permissions to the c:\Program Files\ASD folder and subfolders. The following are steps on how to create a standard user and provide read, write and execute permissions.

Note: These steps also require Administrator rights to perform.

Step 1 Turn off the User Account Control (UAC). Start Button Control Panels User Accounts. Select Turn User Account Control on or off. Uncheck Use User Account Control (UAC) to help protect the computer. Select OK.

Step 2 Create a standard user. Start Button Control Panels Administrative Tools Computer Management Expand Local Users and Groups. Right click Users. Select New User... Create a new user. Select Close.

Step 3 Give Users group Full Control permission for the c:\Program Files\ASD folder and subfolders. Right-click Start Button. Select Explore. Right-click c:\Program Files\ASD folder. Select Properties. Select Security Tab. Select Edit button Select Users Group. Check Full control, Modify, Read and execute, List folder contents, Read, Write Select OK to close Permissions for ASD. Select OK to close ASD properties.

When all of the installations are finished, the following shortcuts will be on the desktop:

RS3 for controlling the HandHeld 2 instrument from an external controller computer.

RS3 with high contrast black and white screen for outdoor use.

HH2 Sync for importing data files from the HandHeld 2 instrument, managing the system presets and base file names, and exporting calibration files to the HandHeld 2 instrument.

ViewSpec™ Pro for post-processing spectra files saved using the HandHeld 2 instrument.


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3.3 ASD Application Software/Hardware Combinations The mode, communications, control and data collection capabilities of the different ASD applications software allow a variety of software and hardware combinations. The following table outlines the various software and their impact on communication modes, control functions and data management. (Figure 95).

Software Mode/Communication Control and data HandHeld 2 Standalone/all-internal

Control commands are sent from the HandHeld 2 instrument. Data is stored on internal HandHeld 2 storage. Spectrum and control screens show on built-in display.

RS3 Tethered/both directions

Control commands are sent from computer to HandHeld 2. Data sent from the HandHeld 2 to computer for display and storage (Data is not stored on HandHeld 2). Control buttons are in RS3 software, as well as the thumb trigger button on the HandHeld 2.

ViewSpec Pro Tethered/one direction, then computer only

Data must already be imported to the computer using HH2 Sync or saved using RS3. ViewSpec Pro imports ASD files from a folder on the computer, converts files to other formats and exports them to a folder on the computer.

HH2 Sync Import Spectrum Data Files from Instrument

Tethered/one direction Only imports spectral data files from the HandHeld 2 instrument to computer hard drive.

HH2 Sync Manage Instrument Presets and Base Filenames

Tethered/one direction Exports presets from the computer to the HandHeld 2 instrument and links asdcfg.ini files from RS3 folder on computer.

HH2 Sync Export Calibration Files To Instrument

Tethered/one direction Only exports radiometric calibration files from computer to the HandHeld instrument.

HH2 Sync Copy Configuration Files

Computer only, then Tethered/one direction

For copying updated configuration file asdcfg.ini from a USB flash drive to the RS3 folder on computer. Then, export asdcfg.ini to HandHeld 2 instrument using HH2 Sync.

Figure 95: Application Software/Hardware Matrix


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3.4 Running the RS3 Software Step 1 Turn on the computer and the HandHeld 2.

Step 2 Once Windows is running, connect the USB cable to the computer and the HandHeld 2. The Tethered Mode message will appear on the display (Figure 96).

Step 3a Start the RS3 application by clicking on either of the shortcuts for RS3 or RS3 High Contrast on the computer desktop (Figure 97).

Figure 97: RS3 shortcuts

Step 3b Or, from the Start menu select All Programs ASD Programs RS3 (Figure 98).

Figure 98: RS3 from Start menu

Step 3c Or, from navigating through the hard disk and its default location, launch the executable file: C:\Program Files\ASD\RS3\RS3.exe

If the system is configured properly, the RS3 spectrum display will appear within 30 seconds (Figure 99).

Tethered Mode

Figure 96: Instrument Tethered Mode display


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Figure 99: RS3 spectrum display

If any communication issues occur, an error message will appear at the bottom-right corner of the spectrum display (Figure 100).

Figure 100: RS3 connection error

Wait approximately ten seconds while the RS3 software makes repeated attempts to find a good connection (Figure 101).

Figure 101: RS3 searching for connection

Step 3 If a good connection cannot be found after a minute, first disconnect and re-connect the USB cable. If this does not result in a good connection, next exit out of RS3 by clicking on the X button in the upper-right hand corner, or if necessary enter Ctrl-Alt-Del to quit the program through the “Task Manager”.

Once a good connection is made, the error message will change to a Connecting message (Figure 102).

Figure 102: Connecting message

The main RS3 application window contains a graph region in the middle, a menu and toolbar at the top, GPS data at the bottom and data collection and status boxes on the left. Use the scroll bar to see all of the different data collection and status boxes. The main application window is sizable and can be controlled by window buttons in the upper right hand corner of the window.


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Move the mouse cursor over the green status dot at the bottom-right corner to see the connection status message (Figure 103).

Figure 103: Connection status

3.5 RS3 GPS If an optional GPS receiver is attached to the computer, verify the GPS Status. The GPS Status is located at the bottom of the main window. The status displays the latitude, longitude and elevation of fixed GPS data (Figure 104).

Figure 104: GPS coordinates

When the GPS data is not fixed, these fields will be blank. The GPS status also contains a status icon which displays the state of the GPS fixed data—right-click on this icon to enable or disable reading the GPS devices. When active, the wave in the lower-left will scroll.

• Refer to Section 8.3 for instructions on installing the GPS receiver for compatibility with RS3.

3.6 RS3 Foreoptics If a foreoptic is attached to the optical input of the HandHeld 2 instrument, ensure that the correct foreoptic is selected in the toolbar foreoptic pull-down menu before taking any measurements (Figure 105).

Use the following procedures from the previous sections on the standalone mode:

• Refer to Section 2.4 Choose A Test Sample

• Refer to Section 2.5 View White Reference Panel

3.7 RS3 Saturation Alert

• Refer to Section 2.6 Saturation Alert (with the following differences for RS3):

Figure 105: RS3 Foreoptic choice in toolbar


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RS3 provides a saturation alarm feature. When saturation occurs an audible beep will sound and the Spectrum Avg progress control will display “Saturation” (Figures 106 and 107).

Figure 106: RS3 saturation alert

Figure 107: RS3 saturation in DN mode

3.8 RS3 Optimization

• Refer to Section 2.7 Optimization (with the following differences for RS3): Use the cursor to click on the OPT button in the tool bar (Figure 108).

Or use the keyboard command [Ctrl+O]. Or select “Optimize instrument settings” from the Control pull-down menu (Figure 109).

After optimization the display will show a raw DN spectrum (Figure 110).

Figure 108: RS3 optimization

Figure 109: Optimization in pull-down menu


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Figure 110: RS3 Raw DN optimized

3.9 RS3 White Reference

• Refer to Section 2.8 Dark Current and White Reference (with the following differences for RS3):

For the White Reference, click on the WR button (Figure 111).

Or use the keyboard command [Alt+C, W], or F4 hotkey. Or select “Take White Reference measurement” from the Control pull-down menu (Figure 112).

After the white reference routine is complete, the display will show a reflectance spectrum of 1 across the entire wavelength range (Figure 113).

Figure 111: RS3 White reference

Figure 112: Pull down menu white reference


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Figure 113: RS3 white reference reflectance spectrum

3.10 RS3 Dark Current For a separate dark current update (without updating white reference), use the cursor to click on the DC button in the tool bar (Figure 114).

Or use the keyboard command [Alt+C, D] or F3 hotkey. Or select “Take Dark Current measurement” from the Control pull-down menu (Figure 115).

• Refer to Section 2.9 Viewing a Reflectance Spectrum from the Sample with the following differences for RS3 (Figure 116):

Figure 114: RS3 dark current

Figure 115: RS3 dark current pull-down menu


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Figure 116: RS3 display of sample reflectance spectrum

3.11 RS3 Pull-down menus RS3 has a small number of pull-down menus, which can all be accessed with the mouse or the keyboard (Figure 117):

Figure 117: RS3 pull-down menus

• Display • Control • GPS • Help

When using the keyboard, press the ALT key and the key corresponding to the underlined letter in the menu name, such as Alt+D for Display.

Once the pull-down menu is open, further operations can be launched by pressing the key corresponding to the underlined letter in the desired pull-down menu item.

In addition, many RS3 operations are available directly through function keys (e.g., F1 through F12), other hot-key combinations, and icons within the application’s toolbar. The items listed in a given pull-down menus typically show their designated hot-key to the right.

3.12 RS3 Display Pull-down Menu The Display pull-down menu can be reached using the mouse or Alt+D (Figure 118).


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Figure 118: Display pull-down menu

This menu includes:

• Axes • Cursor • Grid • Line Properties • View Files • Freeze • Quit

3.12.1 RS3 Axis Settings Select Axes... (Figure 119).

Or use keyboard command [Alt+D, A]. This command allows for configuration of both the X and Y axes (Figure 120).

Figure 119: Axis menu


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Figure 120: The Axes... item [Alt+D, A] to configure the display axes.

Both the minimum and maximum levels can be set. If the viewable range is changed, this dialog box can also be used to restore the default ranges. While the X-axis remains in wavelengths (nm), the Y-axis type can be changed to:

• Raw DN (Digital Number coming from the instrument) • Transmission • Reflectance • Radiance • Irradiance • Absorption

Note: In order to change the Y-axis type from this dialog box, a white reference must first be initiated for the desired type. Refer to Take White Reference measurement [F4]. With the exception of the axis type, these same XY range parameters can be changed using the options from Cursor... [Alt+D, C] or the toolbar buttons, such as Pan, Zm, or XY.

3.12.2 RS3 Cursor Settings Select Cursor... (Figure 121)

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Figure 121: Cursor menu


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Or use keyboard command [Alt+D, C]. The Cursor Mode dialog box shows check boxes to assist in viewing an appropriate range of the spectrum (Figure 122).

Figure 122: Cursor mode

The operations available from this dialog box are also available from the toolbar (Figure 123).

Pan button (or Pan Mode setting) moves the zoom viewing rectangle through the use of the horizontal and vertical scroll bars, or the left/right up/down arrow keys of the keyboard. The Ctrl+arrow keys move the viewing rectangle in larger steps.

Zm button (or Zoom Mode setting) Click & drag a rectangle with the cursor in the graphing area, thereby zooming the viewing area and the XY-axis scaling to that range. The left/right up/down arrow keys of the keyboard can also be used to zoom in the image. The Ctrl+arrow keys zoom the viewing rectangle in larger steps. The right-mouse button has an option to Undo Zoom.

XY button (or Coordinate Mode setting) Move the cursor to a specific point in the spectrum and have its XY coordinates displayed in the lower left-hand corner of the main RS3

display (Figure 124). The point can be specified with the mouse or with the left/right up/down arrow keys of the keyboard.

Figure 124: Coordinates display box

OP button (or Optimize Parameters Mode) displays in the lower left-hand corner of the main RS3 display (Figure 125). For HandHeld 2, the only pertinent parameter is the V IT

Figure 123: Cursor toolbar buttons


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parameter for Visible-Near-Infrared integration time (the S1 and S2 parameters that may appear are not applicable to the HandHeld 2 and have null values of zero).

Figure 125: Optimization Parameters display box

3.12.3 RS3 Grid Settings Select Grid... (Figure 126).

Or use keyboard command [Alt+D, G]. The Display Grid dialog box shows radio buttons to help subdivide and mark up the graphed spectrum for ease of viewing (Figure 127).

Figure 127: Display grid buttons

The settings apply to the X and Y axes independently. Options include:

• No Grid: Turns off the grid in order to override the previous settings. • Tick Marks: Turns on tick marks along the respective X and/or Y axis to help

distinguish the range.

Figure 126: Select Grid


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• Major Lines Only: Turns on graph lines for major division that extend across the graph from the selected axis. The interval used for the major line depends on the zoom scaling.

• Major Lines and Minor Lines: Turns on graph lines for all divisions that extend across the graph from the selected axis. The interval for the grid markings depends on the zoom scaling.

3.12.4 RS3 Graph Line Properties Settings Select Line Properties... (Figure 128).

Or use keyboard command [Alt+D, G]. The Line Properties dialog box allows for changes to the line properties of the displayed spectra for better viewing (Figure 129). The line thickness and color can be modified.

Figure 129: Line Properties dialog box

To change a line’s style:

Step 1 Ensure that RS3 is displaying an active spectrum from the instrument or one or more spectra retrieved from a file.

Step 2 Open the “Line Properties” dialog box using one of the available methods:

Display Line Properties..., or [Alt+D, L], or right-click Line Properties...

Figure 128: Select Line Properties


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Step 3 Select the line desired to change within the dialog box. Step 4 Select its type and color.

3.12.5 RS3 View Files Settings RS3 can display up to five different spectra in the graph region while collecting a current spectrum of the target sample. The previously captured spectra must be of the same data type as the spectra being viewed in real-time.

Step 1 Select View Files... (Figure 130). Or use keyboard command [Alt+D, V].

Figure 130: Select View Files

Step 2 Click on the Select Spectrum Files button to specify files to display (Figure 131).

Figure 131: Dialog box to view several spectra at once

Step 3 Select up to five files to view or click on the Select All check box, then press the OK button (Figure 132).


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Note: To change the files to view type, remove all the files in the “View Files” dialog box and then change the Y Axis type. For better viewing and differentiating of the spectra, change the line properties of the graphs.

Refer to Section 3.16 RS3 Graph Line Properties Settings

3.12.6 RS3 Freeze Display Settings The Freeze function is a toggle to allow the current spectra to be held in place or released to real-time viewing. At this point, the spectra can be compared with other stored spectra files.

Select Freeze [F6] (Figure 133) or use keyboard command [Alt+D, F].

The Freeze function is also activated with the F6 hotkey or from the toolbar (Figure 134).

Even though the display has been frozen, the HandHeld 2 instrument is still reading new spectra. If a Spectrum Save [Alt+S] operation is still being carried out based on the number of files to save and the saving time interval, these operations will continue to happen in the background regardless of the frozen spectral display.

Figure 132: Select files to view

Figure 133: Select Freeze

Figure 134: Freeze button on toolbar


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3.12.7 RS3 Quit Command Select Quit....(Figure 135), use keyboard command [Alt+Q], or click on the X button in the upper right-hand corner of the application (standard Windows functionality) using the mouse.

Figure 135: Select Quit

3.13 RS3 Control Pull-Down Menu The Control pull-down menu can be reached using the mouse or Alt+C (Figure 136).

Figure 136: Control Pull-down Menu

This menu includes:

• Take Dark Current measurement • Initialize Radiometric measurement • Take White Reference measurement • Adjust Configuration • Optimize instrument settings • Abort Spectrum Collection • Parabolic Correction measurement (does not apply to Handheld 2) • Spectrum Save • ViewSpec Pro

Take Dark Current measurement, Take White Reference measurement, and Optimize instrument settings are covered previously in sections 3.8, 3.9 and 3.10.

3.13.1 RS3 Radiometric Measurement Command

• Refer to Section 6.5 Radiance, Irradiance and Wavelength Calibrations for more detail on radiometric measurements.

Select Initialize Radiometric measurement (Figure 137).


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Or use keyboard command [Alt+C, R]. This control activates the radiometric calibration for the foreoptic configuration specified in the toolbar (Figure 138).

The radiometric measurement may also be activated with the F9 hotkey.

3.13.2 RS3 Adjust Configuration Settings Step 1 Select Adjust Configuration... (Figure 139) or use keyboard command [Alt+C, C].

Step 2 In the “Instrument Configuration” settings box, set the number of samples to

average for the sample spectrum, dark current and white reference (Figure 140).

Foreoptic configuration

Figure 137: Select Initialize Radiometric Measurement

Figure 138: Foreoptic configuration in toolbar

Figure 139: Select Adjust Configuration


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Figure 140: Set averaging

Step 3 Click on OK.

3.13.3 RS3 Absolute Reflectance Settings The Absolute Reflectance option can also be activated from this “Instrument Configuration” settings box (Figure 141). Absolute reflectance installs the white reference panel reflectance factors for inclusion in the real-time reflectance calculation.

Step 1 Contact ASD Technical Support so that an Absolute Reflectance file specific to the white reference panel in use can be provided (see Section 7.12 Technical Support for contact information).

Step 2 Copy and paste the absolute reflectance file into C:\Program Files\ RS3 on the computer.

Step 3 Place a check mark in the Absolute Reflectance box (Figure 142).

Figure 141: Absolute reflectance


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3.13.4 RS3 Saving Spectra Before starting the spectrum save commands, it is recommended to create a folder in a convenient location on the computer hard drive. This folder is where all spectral files will be saved so that they will be easy to find later. Otherwise, by default, all of the spectral files will be stored to the RS3 folder where it might difficult to sort them from all the other files in the folder.

• For additional information, refer to Section 2.10 Storing a Spectrum (with the following differences for RS3):

Step 1 Select “Spectrum Save” (Figure 143) or use keyboard command [Alt+S].

Figure 142: Click on the Absolute Reflectance check box

Figure 143: Select Spectrum Save


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Step 2 Enter the information in the Spectrum Save settings box (Figure 144).

Figure 144: Spectrum Save settings

Step 3 Use the browse button to find the folder previously set up for the spectral files and create this path.

Step 4 Saving spectra can now be performed by clicking on the Begin Save button. It can also be done by clicking on OK to go back to the spectral display and using Save commands from that window.

Note: To store a spectrum to the computer hard drive, press the Spacebar key on the computer or the thumb trigger button on the HandHeld 2 instrument.

3.14 ViewSpec Pro Post Processing Application Software Click on the ViewSpec Pro shortcut to open the ViewSpec Pro post-processing application (Figure 145).

Figure 145: ViewSpec Pro shortcut

Or from the Start menu select All Programs ASD Programs ViewSpecPro (Figure 146).

Figure 146: ViewSpec Pro from Start menu

The ViewSpec Pro working window will appear. Select the Help pull-down menu (Figure 147).

Browse button


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A PDF format document of the ViewSpec Pro manual gives complete instructions on using the ViewSpec Pro post-processing software on ASD spectral data files (Figure 148).

Figure 148: ViewSpec Pro manual

3.15 HH2 Sync Application Software The HH2 Sync application imports data files from the HandHeld 2 instrument, manages the system presets and base file names, and exports calibration files to the HandHeld 2. Ensure that the HandHeld 2 is connected to the computer with the USB mini to standard USB cable, as described in section 3.1.

Step 1 Turn on the computer and completely boot up first then turn on the HandHeld 2 instrument. When the HandHeld 2 instrument is ready, the Tethered Mode message will appear on the display (Figure 149).

Tethered Mode

Figure 147: ViewSpec Pro window and Users Guide

Figure 149: Instrument Tethered Mode display


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Step 2 Click on the HH2 Sync shortcut on the computer desktop (Figure 150).

Figure 150: HandHeld2 Sync shortcut

The HH2 Sync introductory screen will appear for a few seconds (Figure 151).

Figure 151: HandHeld Sync introduction

After a few seconds, the Select Action screen will appear (Figure 152).

Figure 152: HH2 Sync Select Action screen


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Step 3 Click on the Connect button to initiate communications with the HandHeld 2 instrument (Figure 153).

Step 4 If this is the first time connecting HH2 Sync to the instrument, a message requesting COM port selection may appear. If so, type in a COM port of 16 or less, for example COM16, and then click OK (Figure 154).

Step 5 If a good connection is not found after a minute, exit out of HH2 Sync by clicking on the X button in the upper-right hand corner, or if necessary enter Ctrl-Alt-Del to quit the program through the Task Manager. Turn off the handHeld 2 instrument.

Step 6 On the computer desktop, right-click on My Computer and select Properties (Figure 155).

Figure 155: My Computer Properties

Figure 153: Connect to HandHeld 2 instrument

Figure 154: Com Port prompt


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Step 7 Under the Hardware tab, select Device Manager and click on Ports (COM & LPT) to view the list of ports (Figure 156).

Step 8 Make a note of which COM ports are available, and then close these hardware windows.

Step 9 Turn on the HandHeld 2 instrument, start-up HH2 Sync again, and click on the Connect button. Enter an open COM port, based upon the investigation above. If the system is configured properly, a status window will appear for roughly 20 seconds while the connection is made (Figure 157).

Figure 157: Connection status

Figure 156: Check COM ports

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3.15.2 HandHeld 2 Instrument Presets and Filenames

Section 2.14 referred to the system presets, which can be created in order to program the device’s most commonly used instrument configurations--including basic instrument control settings and file base name options. Step 1 To adjust these presets, click on Manage Instrument Presets and Base Filenames

(Figure 165).

Step 2 A warning will indicate the need to select the correct asdcfg.ini file. Click on the OK button (Figure 166).

Figure 166: asdcfg.ini warning

Step 3 Unless the default folder was changed when installing RS3, navigate to the asdcfg.ini file located in folder C:\Documents and Settings\All Users\Application Data\ASD\RS3 (Figure 167).

Figure 165: Presets button


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Figure 167: Folder for asdcfg.ini

Step 4 Select the asdcfg.ini file in the RS3 folder and click Open (Figure 168).

Step 5 A warning message will indicate the need to select the File pull-down menu and either open an existing preset or start a new one in the next window (Figure 169). Click OK.

Step 6 If this is the first time entering presets, click on New (Figure 170).

Note: When the ASD Applications Software on the computer is first installed, no pre-existing presets are programmed on the computer. However, when first

Figure 168: Select the asdcfg.ini file

Figure 169: Existing or new file warning

Figure 170: New preset


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started in standalone mode, the HandHeld 2 instrument creates its own initial-internal preset. This preset is stored in the HandHeld 2 instrument and is not available to the external computer. The export of new presets—of which there can be many—is one-way process from the computer to the HandHeld 2 instrument. When a new preset is exported to the HandHeld 2, it will replace the “default” preset already on the HandHeld 2.

Step 7 Click on the Add/Copy button (Figure 171).

Step 8 Create a default Preset by typing in any new name with either letters and/or numerals for the preset (Figure 172). Then click on the OK button.

Figure 172: Make individualized default preset

Figure 171: Add new preset


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The new preset is created and most typical settings are automatically filled into the fields (Figure 173).

Figure 173: New default preset is created

Step 9 To add a new base filename option for this preset, click on the Add button (Figure 174).

Figure 174: Add base filename


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Step 10 Type in a base filename for this default preset, such as “Sample” (Figure 175). Select OK.

Step 11 Click on the Absolute Reflectance check box (Figure 176).

• See Section 3.23 for more information on absolute reflectance.

Step 12 Under the “File” pull-down menu, select Save or Save As… (Figure 177).

Step 13 When prompted, go down the tree to the ASD folder created when the ASD Applications Software was installed— C:\Documents and Settings\All Users\Application Data\ASD (Figure 178).

Figure 175: New base filename

Figure 177: Save the new default preset

Figure 178: ASD Folder

Figure 176: Absolute Reflectance check box


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Step 14 Click on the ASD folder to open it and save the new default preset to this folder.

Also enter the new name for this file (Figure 179).

Step 15 The final step for the new preset is to export it to the HandHeld 2 instrument. Under the File pull-down menu, click on Export (Figure 180).

A status message appears for a few seconds during the export (Figure 181).

Figure 181: Export status

A Export Successful message appears when the export is completed (Figure 182).

Figure 182: Export successful

Figure 179: Name the preset file and save

Figure 180: Export

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4. White Reference Details

4.1 Reflectance White Reference

One way to collect the light incident on the sample is to use a white reference panel, which is also called a white reference standard. White means the panel reflects nearly 100% of the incident light throughout the spectral range. In other words, the reflectance values of the white reference panel are nearly 1 at every wavelength. These white reference panels are constructed so that all incident illumination is reflected diffusely away from the panel. ASD application software can store the incident illumination from the white reference panel, which we call the white reference or WR. Then the software can calculate the reflectance of a sample using the measured light reflected from the sample.

A white reference should be collected approximately every ten minutes—with this interval varied depending upon the rate of changes within illumination conditions. Also update the white reference whenever there are changes to foreoptics or accessories (like switching probes). The white reference panel should be used when optimizing and taking a white reference measurement. For best results when using artificial illumination, the white reference panel should be at the same distance from the HandHeld 2’s optical input as the sample will be during measurements. If the illumination level changes significantly, the stored white reference might no longer be valid. Check the illumination level by aiming the HandHeld 2 instrument at the white reference panel between every few sample measurements.

Note: If the reflectance spectrum of the white reference panel has deviated significantly from 1, a new white reference measurement may be needed. If it is significantly greater than 1, re-optimization is also recommended.

4.1.2 Outdoors White Reference

When using solar illumination collect a new white reference more frequently for: solar changes, like the sun’s angle in the sky where 10 minutes can represent a change in the measurement; atmospheric changes, like blue sky, cloud cover, humidity, or water vapor; significant temperature changes. An experiment to perform when outside is to continue to take measurements of the white reference panel and observe the stability of the white reference line. This will give an idea of how the current fluctuations in weather affects measurements.

Cosine response changes are smallest when the illumination is directly above or at normal to the sample plane, for example, when the sun is at high noon. These effects include both changes due to motion as well as changes due to


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the sun rising or setting. For example, the cosine of the angle changes less than 2% going from 5° to 10° from the surface normal. However, the change is nearly 10% when going from 50° to 55°.

4.2 Spectralon® Spectralon is a popular white reference material manufactured from a sintered polytetrafluoroethylene based material (PTFE). Spectralon is manufactured by and is a registered trademark of:

LabSphere, Inc., www.labsphere.com.

The average reflectance data for 300 to 1100 nm for uncalibrated SRM-990 Spectralon is published by LabSphere and listed within the chart below (Figure 185).

Wavelength (nm) SRM-990 Spectralon® Uncalibrated Reflectance (plus/minus 0.5 percent)

300 0.985 400 0.990 500 0.991 600 0.992 700 0.992 800 0.991 900 0.991 1000 0.993 1100 0.993

Figure 185: White Spectralon Average Reflectance data A calibrated Spectralon is also available, which includes a certificate of measured reflectance values for the specific panel. The HandHeld 2 instrument’s standalone mode software and tethered mode RS3 software assumes that the white reference panel is 100% reflecting (reflectance values of 1 at each wavelength). However, the actual reflectance values are less than 1. These small discrepancies are systematic uncertainties, which can be accounted for during post-processing on ASD’s ViewSpec Pro software. Or if using tethered mode RS3 software, the measured reflectance values of a calibrated Spectralon panel can be used with the Absolute Reflectance setting.


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4.3 Transmittance White Reference

• Transmittance = Light passing through sample/light incident on sample Sometimes the term white reference—often referred to as a blank—is also used for transmittance measurements. The blank is calculated by measuring the incident light directly, or in the case of liquids, by measuring the light passing through an empty glass container. In ASD application software, such as RS3, the scale can be changed to show transmittance. Unlike reflectance, transmittance is the collection of light through the sample instead of reflected from the sample. Please see the ASD Accessories manual and the ASD web page for optional accessories configured specifically for transmittance measurements.


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5. Optional Accessories ASD offers a variety of fiber optic jumper cables for more convenient measurement within various applications. ASD also offers optional foreoptic accessories that attach to the front of the FieldSpec® HandHeld 2 or the optional pistol grip for fiber optic jumper cables.

5.1 Fiber Optic Jumper Cables and Pistol Grip These optional fiber optic cables can be used for reflectance, transmittance, radiance, or irradiance measurements when configured with the proper foreoptic or optional contact probe. When using an optional fiber optic jumper cable, the input signal will be attenuated at the jumper cable connection to the HandHeld 2 instrument.

Note: The glass fibers used in fiber optic jumper cables are easily damaged if the cable is exposed to excessive forces. Please study the maintenance chapter of this manual for the proper care and cleaning of fiber optic jumper cables.

When using the optional fiber optic cable, first screw on the SMA adapter to the bare head of the HandHeld 2 instrument. Do not over-tighten, finger tightening is sufficient (do not use tools). Uncoil the fiber optic cable and mount the SMA end to the adapter securely. ASD also offers a pistol grip for convenient holding of the fiber optic jumper cable (Figure 186).

Pistol grip

Fiber optic jumper cable

SMA adapter

Figure 186: SMA adapter, fiber optic jumper cable and HandHeld 2 type pistol grip


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The fiber optic cable feeds into the rear of the pistol grip. Ensure that the fiber optic tip is fully seated into the nose of the pistol grip (Figure 187).

Figure 187: HandHeld 2 type pistol grip

The fiber optic cable will click into the housing. The end of the fiber optic cable should be flush with the end of the threaded collet on the pistol grip (Figure 188).

There is a set screw at the top of the pistol grip that is pre-adjusted for good seating of the fiber optic cable, as well as easy insertion and removal of the fiber optic cable. However, if the application requires a more snug setting use a 1/8” flat blade screwdriver to tighten the setting after installing the fiber optic cable into the pistol grip (Figure 189).

Note: Under the plastic cap at the base of the pistol grip barrel there is another set screw which is installed at the factory. Do not attempt to adjust this factory set screw on base of the barrel (Figure 189).

Threaded collet Fiber optic jumper cableinput end

Figure 188: Seating of fiber optic jumper input end in HandHeld 2 type pistol grip


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Do not pull hard on the cable once the set screw is tightened. Pulling hard on the cable could potentially break the cable fibers. Once tightened, the set screw must be loosened in order to remove the fiber optic cable from the pistol grip.

5.2 Foreoptics The main input of the HandHeld 2 instrument has a 25° field-of-view and this configuration is the bare fiber input (Figure 190).

ASD also offers a selection of foreoptics for limiting the field-of-view to a smaller angle. The foreoptic may be secured (with the use of fingers only—no tools) onto the main optical input or onto a pistol grip with a fiber optic jumper cable (Figure 191).

• Refer to section 6.8 for information on calculating the proper spot size for measurements. This will ensure that a foreoptic with the most appropriate field-of-view will be used for measurements.

25°

Do not tamper with factory set screw

Adjustable set screw

Figure 190: Bare input field-of-view

Figure 189: Pistol grip set screws


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Figure 191: Field-of-view limiting foreoptic attached to instrument or pistol grip with fiber optic jumper cable

These field-of-view limiting foreoptics also allow for greater distance from the surface under observation, thereby minimizing shadowing and reflected light from the instrument and user.

5.3 Foreoptics for Irradiance Measurements

ASD also offers an optional foreoptics for irradiance measurements. These foreoptics include:

• In-air cosine receptors for measurement of total irradiance (Figure 192). This foreoptic is typically used looking up at the sky to collect full-sky downwelling irradiance. The white bubble level adjacent to the input is used to help orient and mount the HandHeld 2 so that the cosine collector is always level with the horizon.

Figure 192: HandHeld 2 type full sky irradiance cosine receptor attaches to instrument

• Accessories for measurement of direct irradiance

• Underwater cosine receptors for measurement of underwater up and down welling

irradiance.


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5.4 Illumination Sources If the sky is cloudy, it is night time, or if making measurements indoors, ASD offers optional DC powered tungsten quartz halogen lamp light sources and probes with built-in illumination. Some light sources require AC wall current for power and others are powered by battery packs.

ASD offers the Pro Lamp for general illumination in a variety of applications (Figure 193).

Figure 193: ASD Pro Lamp

This device is powered by an AC/DC power adapter that plugs into a wall receptacle. The focusing knob on the side of lamp can be adjusted for more intense or more diffuse light. An average spot size of reasonable homogeneity is roughly 10 cm at a 50 cm lamp distance. Two lamps improve this geometry significantly, especially for large samples.

5.5 Contact Probes ASD also offers contact probes with built-in illumination that can be attached to optional fiber optic jumper cables (Figure 194).

Figure 194: ASD High Intensity Contact Probe, High Intensity Mug-Light, and Plant Probe with Leaf Clip.

These devices are powered either by a battery pack or an AC/DC power supply.


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5.6 Integrating Sphere ASD offers the RTS-3ZC Integrating Sphere to collect all light reflected from, or transmitted through, a sample (Figure 195).

Figure 195: ASD RTS-3ZC Reflectance/Transmittance Integrating Sphere

The sphere, by nature of its internal diffuse (Lambertian) reflection and integration of the energy from all directions from the sample surface, gives a very repeatable measurement. Sample placement and incidence beam/collection alignment are less critical to the measurement results because the integrating sphere looks at representative averaged energy from all angles at the same time.

5.7 GPS ASD offers some GPS receiver options, or the customer may provide their own GPS receiver that meets ASD specifications. Presently, only RS3 software in tethered mode can store and merge GPS data with spectral data in real-time.

RS3 software requires the output of the GPS device to be in the National Marine Electronics Association (NMEA) standard 0183, RS232 serial port format. Check the GPS device documentation for output and port settings. Please see the section 8.3 Optional GPS Specifications for additional information on using a GPS receiver with the HandHeld 2 instrument.


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6. Theory and Measurements This section contains basic background and measurement information.

6.1 Light Light is electromagnetic radiation, which is the propagation of energy through space by changing electric fields inducing magnetic fields and vice versa. A mathematical model that describes this process is a sinusoidal wave (Figure 196).

Figure 196: Wavelength

Wavelength λ is the distance traversed by one period of an electromagnetic wave. λ = c/f, where c is the velocity of light and f is the frequency.

Various names are used to identify wavelength regions of electromagnetic radiation (Figure 197).

Optical means controllable by lenses, mirrors, prisms, diffraction gratings and fiber optics.

By most formal definitions, light is only electromagnetic radiation that our human eyes can detect, in other words, visible. However, in general the term light is often used to describe all optical electromagnetic radiation.

There are other models to describe electromagnetic radiation such as the particle model of quantum physics. These other models go beyond the scope of this document. It suffices to say that all the models agree with one another in the major aspects and that the wave model is the one with which we are most familiar.

λ

Distance

Electric field amplitude

Magnetic fieldamplitude


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Electromagnetic Radiation

Region Names Wavelength, λ nanometers (nm) or microns (µ)

Cosmic Ray Gamma Ray < 1 nm X Ray Ultra- Violet

(UV) Far Ultra-Violet 1 - 200 nm

Ultra Violet C (UVC) 200 - 280 nm Ultra Violet B (UVB) 280 - 315 nm Ultra Violet A (UVA) 315 - 400 nm Visible (VIS) Photosynthetically Blue Light 400 - 525 nm Active Green Light 525 - 605 nm Radiation Yellow Light 605 - 655 nm (PAR) Red Light 655 - 725 nm Far Red 725 - 750 nm Infrared (IR) Near-Infrared (Near-IR) Short Wave Near Infrared (SW-NIR) 750 - 1100 nm Optical Typical 1st NIR region detector

(NIR1) or (SWIR1) 1000 - 1800 nm

Typical 2nd NIR region detector (NIR2) or (SWIR2)

1800 - 2500 nm

“Conventional” Near Infrared (NIR)

1000 - 2500 nm or 1.0 - 2.5 µ

Mid Infrared (Mid-IR) 2.5 - 50 µ Thermal (emitted) 8 - 15 µ Far Infrared (Far-IR) 50 - 1000 µ Micro wave & Radar

UHF TV VHF TV & FM Radio

>1,000 µ

AM Radio

VHF TV & FM Radio

AM Radio

Figure 197: Electromagnetic Radiation


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6.2 Light and Matter Interaction When light interacts with matter, some of the energy is transferred to the matter by the alternating fields pushing and pulling atomic and molecular charge carriers. Light leaves the matter as energy released from the moving atomic and molecular charge carriers. There are several processes of light/matter interaction (Figure 198).

Figure 198: Light/matter interaction processes

For light of incident energy Ei the different interaction processes are as follows:

Absorption: Portion of incident light converted to electrical current or heat energy (molecular vibrations) inside the sample. Absorption cannot be measured directly. Reflection: Portion of incident illumination instantaneously absorbed and then emitted back from the sample surface with no energy loss. (Specular Reflection (θr ≈ θi) and Diffuse Reflection (θr ≠ θi)) There is no absorption at the specular angle, which is also wavelength dependent. The specular component is very intense and it is often desirable to avoid this component. Light and matter interact with a mixture of diffuse and specular components. Some materials are mostly specular, such as mirrors. Other materials, including most natural samples, are mostly diffuse. Transmission: Direct: Portion of the incident illumination passes directly through the sample without any interactions. Diffuse: Portion absorbed and re-emitted over and over again. Emission: From internal chemical reaction, incident light converted to heat energy, direct external heat energy, or external electrical energy. Luminescence: Portion of incident light (Excitation Source) converted to longer wavelength. Fluorescence and phosphorescence distinguished by their ground and excited states. Luminescence is different from other processes such as reflection and transmission. Under broadband illumination—such as solar or tungsten filament bulb—luminescence usually appears as a narrow feature on top of a broader reflectance or transmittance spectral feature. If the reflectance or transmittance is near 1, then the luminescence feature may exceed 1. A narrow illumination source—called an excitation source—is required for isolating the luminescence feature from the other processes.


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Raman Scattering: Highly polarized narrow band incident illumination, such as how a laser reacts with molecules of polarization that vary as a function of interatomic distance. The light leaving the sample is of a lower or higher wavelength from incident illumination depending upon the interaction. Raman Scattering is different from other processes such as reflection, transmission and luminescence. Raman energy is usually thousands of times less than the luminescent energy and occurs in the visible to mid-infrared regions.

Conservation of Energy: Conservation of energy requires the following relationship for all of these processes:

Ei = EReflection + ETransmission + EAbsorption + ELuminescence + EEmmision + ERaman

Dividing through by Ei gives:

1 = (EReflection / Ei) + (ETransmission / Ei) + (EAbsorption / Ei) + (ELuminescence / Ei) +

(EEmmision / Ei) + (ERaman / Ei)

Some of the quotients above are also known as follows:

Reflectance (R) = EReflection / Ei

Transmittance (T) = ETransmission / Ei

Absorptance (A) = EAbsorption / Ei

When (ELuminescence / Ei), (EEmmision / Ei) ,(ERaman / Ei) are negligible:

A = 1 – R – T

When T is negligible: A = 1 – R

When R is negligible: A = 1 – T

6.3 Light Energy

A fundamental convention in light energy measurement uses the units:

Radiance (Watts/m2/steradiand/nm) and Irradiance Radiance (Watts/m2/nm)

Radiant Flux, F (Figure 199):

The amount of light energy that crosses a defined surface in a unit time (light energy represent by many vectors or a single summed vector). In the figure shown above, the radiant flux is pointing in towards the surface; however it could also be pointing outward away from the surface.

Figure 199: Radiant Flux


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Radiance, L (Figure 200):

Radiance is the Radiant Flux ∆F per unit projected area ∆Aproj per unit solid angle ∆Ω. So, Radiance is an energy density within the solid angle. (Solid angles can be any geometry with a point subtending out to a surface like a cone, or pyramid.)

L = ∆F

∆Aproj∆Ω=

∆F

∆A cosθ ∆Ω

The units of radiance are Watts/meter2/steradian. In this quantity the projected area may be that of a detector surface, a source surface, or an imaginary surface in space. The flux may be that falling on a detector or being emitted by a source. In other words, the vector along the radius arm D may point into or away from the surface. See Appendix A, which shows how this equation can be re-written as:

L cosθ dΩ

Ω∫ =

dFdA

Irradiance, E: Irradiance is defined as dFdA and has units of Watts/meter2 and so, Irradiance

is an energy density within the area. Spectral Irradiance also integrates over the wavelength interval and so,

Da

b

c

dθ

e

∆A

Projected Area ∆A proj

Radiant Flux, ∆F

xy

z

D

x

y

z

∆A

θ

∆Ω

∆Ω

Surface

D

φ

4π Steradians

Sphere

θ

∆Aproj

φ

∆A

Figure 200: Radiance


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Spectral Irradiance, Eλ: Spectral irradiance has the units Watts/meter2/nanometer.

Spectral Radiance, Lλ: Spectral radiance has the units Watts/meter2/steradian/nanometer.

There are two cases for the above integral equation that are useful in practice applications.

CASE CONDITIONS: For both cases, consider only the radiant flux present in the hemi-sphere, and let the radiant flux within the solid angle dΩ have the same magnitude anywhere within the hemisphere. In other words, let radiance L be constant regardless of what direction from which it travels.

Let the vector dF represents the radiant flux that is both within the solid angle and also falls on dA (Figure 201).

CASE 1. Let dΩ be integrated over a very small interval forming a narrow “beam” of radiance. Then the radiance of the beam results in irradiance on the area dA as follows: Ebeam = Lbeam Ω cosθ

Therefore, E(at θ ≠ 0)beam = E(at θ = 0)beam cosθ, which is commonly known as the cosine response.

A real example of the cosine response would be a large beam of light consisting of the sum of many small narrow beams, parallel to each other in other words, “collimated light” (Figure 202).

Figure 202: Cosine response

CASE 2. All of the irradiance on dA is related to all of the radiance in the hemisphere as follows (see Appendix A for integration details):

E = π Lhemisphere

Same beam of radiant flux lines, but at greater angle to surface normal.

Same number of flux lines, but spread over larger area (large circle). Ie., lower energy per unit area. Ie., lower irradiance. Surface

Sur

face

Nor

mal

Beam of radiant flux lines projects small gray circle.

Unit Area (small box)

dF

dΩ

θ

dA

Figure 201: Radiant Flux in Hemisphere


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A real example of the hemispherical case is sky radiance and the irradiance measured at a point on the ground. This measurement is commonly known as “full-sky irradiance”, which is the sum of irradiance contribution from the sky plus the direct irradiance from the sun.

6.4 HandHeld 2 instrument Detection Using the bare input of the HandHeld 2 instrument or telescopic foreoptic, the total integrated solid angle Ω is set by the field-of-view. The HandHeld 2 instrument detector measures the radiant flux on its area from within the field-of-view. This geometry maps best to the definition of radiance. Therefore, at its most basic level, the HandHeld 2 instrument detects radiance (Figure 203).

However, there is one condition for a perfect mapping to a real measurement. The detector cannot “know” how dF varies as dΩ integrates throughout the field-of-view. In real measurements, the smaller the field-of-view, and/or the smaller (closer) the projected area Aproj is, the more likely the radiant flux is constant. So, we either need to limit the field-of-view and distance or we need to limit the measurement to fields of nearly constant radiant flux. (Constant radiant flux is the same condition as the aforementioned special cases.)

In fact, both conditions of field-of-view and radiant flux are optimized depending upon the application, desired measurement and uncertainty budget.

For source radiance measurements, a diffuse reflector is used in front of the detector field-of-view to measure reflected radiance. This diffuse reflector “scrambles” the radiant flux so that the detector field-of-view will detect the same magnitude of radiant flux throughout the projected area Aproj, no matter the angle of the detector field-of-view to the reflector (Figure 204).

Reflectors with these properties are called “Lambertian”. Some Lambertian reflectors are nearly 100% reflecting throughout a wide spectral region and these are used to measure source radiance.

Incident source radiance

Lambertian (diffuse) reflector

Detector sees same radiant flux at any angle

dΩ

Ω HandHeld 2 instrumentdetector

dF

Aproj

Figure 203: Detector measures radiance

Figure 204: Diffuse reflector


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For samples, reflected or transmitted radiance measurements may be limited to samples and/or views that are nearly Lambertian or diffuse.

For irradiance measurements, a transmissive diffuser foreoptic may be used in front of the field-of-view. This diffuser serves two purposes: first, it “scrambles” the radiant flux such that the detector field-of-view will “see” the same magnitude of radiant flux throughout the projected area Aproj; and secondly, it should have a design that gives a cosine response under ideal CASE 1 conditions previously mentioned in Section 6.3 Light Energy under Spectral Radiance. ASD offers such a foreoptic as an option and it is called the Remote Cosine Receptor (Figure 205).

6.5 Radiance, Irradiance and Wavelength Calibrations For electro-optical systems, such as ASD HandHeld 2 instruments, the response is based on the electrical current produced by a photodetector. In its most basic form, a photodetector produces electric current in a linear relationship to the amount of radiant flux incident on the detector. Therefore, if we have a source that produces some known levels of radiance or irradiance, we can relate the detector electrical current produced from those sources to the known radiance or irradiance levels. This process is called radiometric calibration.

An example of a light source that produces known radiance values, which is very well characterized and controlled, is a tungsten quartz halogen lamp traceable to NIST (Figure 206).

Detector field-of-view

Diffusor

Figure 205: Diffusor type Cosine Collector


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Figure 206: NIST Traceable filament lamp (this graph includes energy outside HandHeld 2 spectral range

A second form of calibration is relating light sources of known wavelengths to the position of the dispersion optics that break the light into the individual wavelength components. This process is called wavelength calibration. An example of a light source that produces well known wavelength positions is mercury-argon low pressure lamp (Figure 207).

Figure 207: Mercury-argon low pressure lamp spectrum

ASD HandHeld 2 instruments use concave reflective diffraction gratings to disperse and focus the light onto the photodetectors. In the HandHeld 2 instrument the gratings are fixed and they reflect the dispersed light onto an array of fixed detectors called a photodiode array (Figure 208).

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Figure 208: HandHeld 2 uses fixed grating and array

The HandHeld 2 instrument covers some of the ultra-violet region, all of the visible region and some near infrared region, and we call this coverage VNIR.

6.6 Illumination Geometry

Measurements can be made very close up, under well-controlled laboratory conditions. Or, measurements can be made at far or close distances, outdoors using solar illumination. In all cases the most important measurement conditions are illumination source, geometry and conditions.

One common illumination geometry is a point source. An ideal point source radiates flux equally in all directions (Figure 209).

Figure 209: Point source

A real example of a point source is a tungsten filament light bulb with a very small filament. “Very small” means the filament dimensions are insignificant relative to the distance to the sample. The sun may also be considered a point source due to its very far distance from the earth.

Radiant flux density for a unit area drops off as that area moves farther away from a point source, assuming angular orientation of the area stays the same. In other words, there are fewer flux lines on the area the farther away it is from the point source (Figure 210). This drop in radiant flux density is sometimes referred to as r-squared effects since the density drops off as the square of the distance. R-squared effects are reduced the farther away the area is from the point source (Figure 210).

Unit area


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Figure 210: R-squared effects

R-squared effects are insignificant for the sun due to its far distance from Earth. R-squared effects can be mitigated with lenses, mirrors, or baffles that result in collimated light, which is light with parallel radiant flux lines (Figure 211).

Figure 211: Collimation

The reflector approach collimates most of the light (solid lines), however, some of the point source lines radiate directly.

As mentioned previously in this section, the cosine response can also affect radiant flux density for the viewed sample area (Figure 212).

Figure 212: Cosine effect

In the laboratory, lamp positions can be fixed and samples oriented to minimize cosine response differences. For simplicity, the figure above shows only collimated contribution—however, the radially divergent contribution is also a function of the angle. Outside measurements using the sun can be challenging in this regard, since the sun is always

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moving. Also, with outdoor measurements, it may not be possible or desirable to move the sample. Cosine differences are smallest for the smallest angles. So, for solar illumination the best time to minimize cosine response differences is when the sun is at high noon.

In general, diffuse measurements are desired. Therefore, the specular component is to be avoided by setting the sensor input view off of the specular angle (Figures 213 and 214).

Figure 213: Suggested lamp set-up

One should be careful how hot and how close lamps are to a sample. Samples could be “cooked,” (which can cause water loss and chlorophyll degradation in leaves,) thereby significantly changing how they reflect or transmit light.

Another important illumination geometry issue is shadowing, which can leave some areas of the sample with less illumination than others (Figure 215). Large textures can result in shadowing. The operator or instrument can cause shadowing. Source and/or sample orientation should be set to minimize shadowing.

Figure 215: Shadowing effects

Scattered light from surrounding objects such as tripods, the operator, and even the instrument itself can be a problem. One should position or hold the sensor as far as possible

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Figure 214: Position sensor to avoid specular component


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from these objects, while ensuring that the field-of-view is filled with the sample. Avoid light scatter from operator and other objects (Figure 216).

Figure 216: Avoid light scatter from operator and other objects

Another important consideration for outdoor measurements is the effect of wind. If a sample is being blown about by wind, its orientation to the illumination can change significantly during the measurement. These wind effects should either be characterized for recognition/ correction or they should be avoided during the measurement.

6.7 Illumination Energy Characteristics Solar illumination energy is affected when it passes though the Earth’s thick atmosphere. These effects are seen in an energy graph of sun and sky radiance reflected from a white reference panel, as a function of wavelength (Figure 217).

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Figure 217: Solar Radiance (This graph includes information outside of the HandHeld 2 spectral range)


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Various gasses in the Earth’s atmosphere, especially water vapor absorb solar energy at specific regions. Gasses in the sun’s atmosphere also absorb energy, for example “Fraunhofer Lines”.

In contrast, an energy graph for a tungsten lamp very close to the sample shows a smooth curve (Figure). The tiny atmosphere between the lamp and the measurement area has an insignificant effect (Figure 218).

Low pressure gas emitter type lamps, such as fluorescent tubes, have features of high energy at specific wavelengths and almost no energy across broad wavelength regions (Figure 219).

Figure 219: Fluorescent tube energy

6.8 Field-of-View Field-of-view determines the measurement area, known as the spot size. All ASD HandHeld 2 instruments have conical shaped fields-of-view with the main bare input of 25° full conical angle (Figure 220).

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Figure 218: Tungsten lamp irradiance (this graph includes information outside of the HandHeld 2 spectral range)


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The spot size increases with distance from the input to the sample. ASD also offers attachable/detachable lens foreoptics that reduce the field-of-view to cover a smaller spot size at the same distance from the input to the sample. A spot sufficient to cover variation of interest in the sample is desired. However, the spot should also be small enough to avoid background material.

Some pre-measurement calculations are useful to ensure proper spot size (Figures 221 and 222).

Figure 221: Field-of-view calculation (near field and normal to sample)

D = Effective diameter of foreoptic lens A = Foreoptic angular field-of-view X = Distance to viewed surface Y = Diameter of field-of-view

Near Field (less than 1 meter): Y = D + 2 * X * Tan( A/2 ) Far Field (greater than 1 meter): Y = 2 * X * Tan( A/2 )

Values of ‘D’ (in mm) for ASD HandHeld 2 Foreoptics: 1° 8.6 3.5° 3.4 7.5° 2.3 10° 2.0

Spot size at

Field-of-view

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Input

Figure 220: Field-of-view


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Approximating Spot Size (far field >1 m)

arctan(y/x) = α = (FOV full angle)/2 y/x = tan α y = x tan α z + w = h tan (β + α) w = [h tan (β + α)] - z and w = h tan β Therefore: z = h [tan(β + α) - tan(β)], this is actually (w+z) – w. Also w = square root of (x2 + h2 - 2xh cosβ) Diameter of oblique ground sample: Diameter = h [tan(β + α)- tan(β - α)] EXAMPLE: 1 degree FOV Tube at x = 2 meters from perpendicular sample (small ellipse): y = (2 meters) tan (0.5 deg) = 0.0175 meters = 1.75 cm So, for a perpendicular sample the spot has a diameter of 3.5 cm EXAMPLE: Suppose we were limited to a 12.7 x 12.7 cm (.127 x .127 m) oblique sample. So, to be on the safe side we will want z = 0.0635m. For h = 1 meter, β = 45 deg, 1 degree foreoptic: w = [h tan (β + α)] - z = [tan(45.5 deg)] - 0.0635]meters = 1 m

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Figure 222: Field-of-view (far field)

22h wh ′+=′

( ) d12−+=′ zww

Semi-minor axis = ( )o5.12tanh2 ′


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6.9 Reflectance Calculations Reflectance, R : A defined calculation:

R = Energy leaving the sample by reflection / Energy incident on sample

Using radiance:

R = Lr / Li where view Lr is the radiance reflected from the sample and Li is the radiance incident on the sample.

Or, using irradiance:

R = Er / Ei where view Er is the irradiance reflected from the sample and Ei is the irradiance incident on the sample.

These calculations are ratios and the energy units cancel out. So, if all we want to calculate is reflectance, we do not need radiometric calibration. All we really need is the response of the instrument for Lr in some unit of measure and the response of the instrument for Li in the same unit of measure. In the case of our photodetectors, we convert the raw uncalibrated electrical current signal into computer type digital numbers, DN. Therefore,

R = DNr / DNi where view DNr is the raw DN of the energy reflected from the sample and DNi is the raw DN of the energy incident on the sample.

6.10 Reflectance Measurements Reflectance measurements are made using radiance, or irradiance, or a combination of both.

Using Radiance:

A Lambertian reflector is used in the measurement of the incident radiant flux on the sample, a.k.a. incident illumination. This process is known as taking a white reference and the reflector used in this step is called a white reference panel.

Calibrated radiance measurements are ratioed in post-processing. Or, more commonly the raw DN measurements are ratioed as they are recorded in “real-time”. The white reference panel is positioned near the sample and is oriented to receive all of the available incident illumination while at the same time avoiding shadowing and light reflected from surrounding objects. For example, for an outdoor measurement using the sun as the illumination source, the panel would be level and perhaps alongside side and/or above the sample and the operator (Figure 223).

Sample

White reference panel

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Figure 223: White reference collection under solar illumination


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Dark clothing also helps minimize light reflected from the user. The white reference is measured by pointing the HandHeld 2 instrument at the white reference panel so that the detector field-of-view sees only the white reference panel (i.e., the field-of-view is filled with the white reference panel). If necessary use a larger white reference panel or field-of-view limiting foreoptics to allow greater distance between the user or other objects and the panel (Figure 224).

The operator initiates a white reference data collection in the instrument software. This white reference measurement is used in subsequent reflectance calculations until the operator collects an updated white reference.

The HandHeld 2 instrument is moved so that the detector field-of-view is filled with the sample (Figure 225).

Of course, all of the same field-of-view and spot size issues mentioned above for the white reference must also be considered for the sample measurement. The ratio is calculated by the HandHeld 2 instrument software and the result is viewed and, if desired, stored. Using Irradiance: Using two irradiance measurements for reflectance is unusual but it can be done in certain circumstances where the sample area is large and the sample properties are uniform over the area—for example, water body measurements or large fields or canopies. Within the

White reference panel

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Figure 225: sample measurement

Figure 224: Foreoptic and larger white reference panel allow greater distance


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uncertainty associated with the small contribution of the non-sample view at the edges, the reflected irradiance from the sample could be measured (Figure 226).

The incident irradiance is measured by pointing the detector with cosine receptor at the illumination source, such as the sky (Figure 227).

Using both Radiance and Irradiance:

Applying the aforementioned CASE 2 relationship from Section 6.3 Light Energy to full sun and sky irradiance:

Esky = π Lsky where Esky is full sky irradiance is the irradiance incident on the sample and Lsky is the radiance reflected from the sample.

Therefore, Lsky= Esky / π

So, using full sky illumination: R = Lsample / Lsky

Therefore, R = π Lsample / Esky

Lsample , is measured as shown in the aforementioned “Using Radiance”.

Esky , is measured by pointing the detector with cosine receptor up at the sky.

Cosine receptor

Signal from sun and sky

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Figure 226: Cosine receptor looking down

Figure 227: Cosine receptor looking up


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6.11 Reflectance Measurement Devices

In a laboratory environment, it is often convenient to use lamps for making reflectance measurements (Figure 228).

Position the sensor to avoid specular components and shadowing (see Section 6.6 Illumination Geometry). If the measurement data is to be compared to other sensors, such as orbiting hyperspectral imagers at nadir (see Section 6.18 Terminology for definition of nadir), consider the position of those other sensors relative to the samples and compare to the sensor position. For the most representative diffuse measurements, and to ensure filling the field-of-view, avoid positioning the sensor too far from nadir. Use one or two quartz-halogen cycle tungsten filament lamps (~3400°K color temperature) in housings with metal reflectors. The lamps should be powered by stable direct current (DC) power sources such as high quality AC/DC power supplies or batteries. Maintain constant and far enough distance to the sample to mitigate r-squared effects. A stable set-up can also mitigate angular effects (cosine response). Also, the illumination time and distance should be checked to avoid “cooking” samples (which can cause effects like water loss and chlorophyll degradation in leaves). Other more specialized devices, with artificial light sources are useful both in the laboratory and in the field when solar illumination is not available. A device for collecting reflectance at a set angle and distance from direct artificial illumination is called a contact probe (Figure 229). This probe also isolates the illumination to only the internal artificial light source.

Integrating spheres are sometimes used for collecting reflected light from all angles, for a measurement known as full hemispherical reflectance (Figure 230). The sphere, by nature of its internal diffuse (Lambertian) reflection and integration of the energy, is insensitive to directional reflectance features coming from the sample, and therefore, gives a very repeatable “averaged” response to the reflectance of the sample placed in the beam at the sphere port.

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~60

Figure 228: Lamps

Figure 229: Contact probe


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Bi-furcated fiber optic contact probe use one set of fiber optic fibers to illuminate the samples and a second set of fibers to channel the reflected light back to the sensor (Figure 231).

6.12 Transmittance Calculations

Transmittance, T : A defined calculation:

T = Energy passed through a sample by transmission / Energy incident on sample

Using radiance:

T = Lt / Li where view Lt is the radiance passed through the sample and Li is the radiance incident on the sample.

Or, using irradiance:

T = Et / Ei where Et is the irradiance passed through the sample and Ei is the irradiance incident on the sample.

As with reflectance, these calculations are ratios and the energy units cancel out. Therefore,

T = DNt / DNi where view DNt is the signal passed through the sample and Ei is the irradiance incident on the sample.

Bouguer-Lambert-Beer Law (BLB Law, Beer's Law): For dilute analyte solutions, collimated incident illumination, negligible luminescence, and negligible scattering:

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Figure 230: integrating sphere

Figure 231: Fiber optic contact probe


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log(1/T) = αlc, at a given wavelength λ where α is the molar absorption coefficient, l is the path length, and c is the analyte concentration. The quantity log(1/T) is called absorbance. Absorbance is a unitless quantity, however, the term absorbance units (AU) is often used to indicate this type of measurement. This law is valid only for transmittance measurements and much has been written on the mathematics and physics of the law. There is no rigorous derivation of a similar law that relates reflectance to analyte concentration. Absorbance cannot be measured directly since there are no means to directly observe the processes occurring within matter. Instead, what is actually measured is transmittance.

There is no similar rigorous derivation for the expression: log(1/R) = αc

However, the log transform is sometimes used on R to facilitate a linear regression approximation between the concentration of the analyte and the spectral data. Applying log(1/R) can sometimes hurt the regression more than help, especially in classification models where a linear regression may align well in one regression region but align poorly in another regression region.

BLB does not rule out relationships between T or R and concentration in non-BLB conditions. It simply guarantees a linear relationship if the conditions are present.

6.13 Transmittance Measurements Transmittance measurements require different sample presentations than reflectance. The simplest transmittance measurement uses any geometry of light the passes through a sample, including liquids as well as thin solids and films (Figure 232).

The white reference for transmittance is sometimes called the blank, which simply means a measurement of the illumination with an empty sample container, container with non-absorbing sample, or no sample in the path.

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Figure 232: Transmittance


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6.14 Transmittance Measurement Devices More specialized devices with artificial light sources are useful both in the laboratory, and in the field when solar illumination is not available. Sometimes a cuvette is used to hold liquid samples (Figure 233).

ASD offers various optional cuvette holders and other devices for measurements with cuvettes. Sometimes an integrating sphere is used to collect transmitted light from all angles on the transmitted side, which is called full-hemispheric transmittance (Figure 234).

Sometimes a measurement consists of both transmittance and reflectance, which is sometimes called transflectance (Figure 235).

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Figure 233: Transmittance cuvette holder

Figure 234: Integrating sphere for reflectance

Figure 235: Transflectance probe


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Bi-furcated fiber optic immersion probes use some fiber optics to carry light to the samples and some to carry the transmitted light back to the sensor (Figure 236).

The example above shows a single pass through the sample, but sometimes the design uses a dual pass.

Sensor fibers Sensor

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Figure 236: Immersion probe


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6.15 Solar Illumination Measurements Many aspects must be considered for outdoor measurements using solar illumination (Figure 237).

Ex is Exoatmospheric Solar Irradiance just above Atmosphere LP is Path Radiance (a.k.a. “Haze”), (no matter-interaction other than atmosphere). LS is Sky Radiance at the sample ED is Direct Solar Irradiance at the sample Lr is Reflected Radiance near the sample LB is Radiance Reflected from and Back-scattered from Atmosphere LO is Radiance Reflected or Emitted from Surrounding Objects (including the user) LC is Radiance Reflected from or Absorbed by Changing Clouds LR is Apparent Reflected Radiance Measured by the Spectral Imaging Sensor (“Apparent” refers to uncertainty in orientation). LI is Total Radiance Measured by Spectral Imaging Sensor in Raw Digital Numbers (DN) N is Normal to Surface dΩ is the solid angle defining the Direct Solar Radiant Flux reaching the Area. θ is the Solar Zenith Angle (cosine response) σ is the effect of shadowing by surrounding objects LD is Direct Solar Radiance at the sample T↓ is Downward Atmospheric Transmittance T↑ is Upward Atmospheric Transmittance ρ is the Apparent Reflectance of the sample Downwelling refers to all energy directed downward from the sky Upwelling refers to all energy directed upward towards the sky

Ground HandHeld 2 instrument

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Figure 237: Solar Illumination measurements


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6.16 Spectral Measurements So far we’ve discussed many measurement aspects, mostly exclusive of the wavelength. However, all of these aspects do behave as a function of wavelength, which is the real information of value. For example, a graph showing reflectance as a function of wavelength is a graph of spectral reflectance or a reflectance spectrum (Figure 238).

Figure 238: Example of reflectance spectrum

6.17 Terminology This section includes some important terminology that is not discussed in other sections. Absorbance Units: When referring to Absorbance measurements made under the conditions of Beer’s Law, the units are usually indicated by AU for absorbance units (eg. Absorbance = 6 AU).

Absorbance = log(1/Transmittanceλ) = -log(Transmittanceλ) Example: Transmittance = 10–6

⇒ Absorbance = –log (10–6) ⇒ –Absorbance = log (10–6) ⇒ 10–Absorbance = 10–6 ⇒ Absorbance = 6 AU

Accuracy: Accuracy is a measure of how close repeated measurements are around the True Value. Albedo: Total reflectance of a surface integrated over all illumination angles. Diffuse or hemispheric albedo has nearly the same reflectance at all illumination angles (nearly constant BRDF). Albedo is typically limited to wavelengths of the visible spectral region. Albedo ranges from 0 (perfectly black) to 1 (perfect reflector). Albedo is around 0.07 for the total surface of the moon.

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Bidirectional Reflectance Distribution Function (BRDF): Ratio of the reflected radiance at an angle to the incident collimated irradiance at an angle. BRDF graphs are three dimensional plots for a set wavelength showing the vertical axis as the ratio versus the view angles of the other two axis. Chromophore: Some materials absorb energy by electron transition and are called chromophores. Chromophores typically involve covalently bonded unsaturated groups such as, phenyl. Dark Current Measurement (DC): Systematic uncertainty from electrical current that is inherent in the detectors and other electrical components and is an additive to the signal generated by the measured external optical radiation. When the DC measurement is made with an ASD spectrometer, a shutter closes, preventing any ambient light from entering the sensor input. This DC spectral data is stored as the DCC (Dark Current Correction) entry in the instrument's initialization file, asdcfg.ini. The controlling software automatically subtracts all spectra taken with the shutter closed to account for this minor complication. Derivative Spectrum: A spectrum that is the result of applying a derivative transform to the data of the original spectrum. Derivatives of spectra are very useful for two reasons:

1. First and second derivatives may swing with greater amplitude than the primary spectra. For example, a spectrum suddenly changes from a positive slope to a negative slope, such as at the peak of a narrow feature (see the figure below). The more distinguishable derivatives are especially useful for separating out peaks of overlapping bands.

2. In some cases, derivative spectra can be a good noise filter since changes in baseline have a negligible effect on derivatives (Figure 239).

Figure 239: Derivative spectra

Absorbance spectrum

First derivative

Second derivative

Sudden change in the curve


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For example, scattering increases with wavelength for some biologically active macromolecules, causing an increasing slope of the absorbance baseline.

A commonly used approximation of the first derivative is: dα/dλ = [α (λ + ∆λ) - α (λ - ∆λ)] / 2∆λ. Derivative spectra yield good signal-to-noise ratios only if the difference of noise levels at the endpoints of the interval is small enough to yield a noise equivalent ∆dα/dλ calculation much smaller than the absorbance.

Difference Spectrum: A spectrum that is the result of subtracting all the signal channels of one spectrum from another. Digital numbers (DN): The detector converts light energy into an analog electrical signal which is then parsed into discrete values between 0 and 65,535. Each of these discrete values is called a digital number. Digitization: All ASD spectrometers use 16 bit digitization. DriftLock®: An ASD proprietary software and hardware combination that continuously updates the Dark Current (DC) measurement to account for small short term DC changes over time by automatically updating DC for every measurement by measuring the output of a series of masked pixels in the photodiode array. DriftLock works in combination with the standard DC update function. Ground Truthing: Data collected in-situ on the ground to validate, interpret, and calibrate aerial or orbital sensor data. Nadir: Directly above or opposite. Normal (perpendicular) to the surface. Noise: Noise is any signal that is not true signal, or any signal that is useless or disturbing to the true signal. Noise is part of the total uncertainty and can be random or systematic. For example, dark Current is a source of Systematic noise. Stray light is usually systematic noise, although stray light can come from random sources. Internal electronics can also be a source of either random or systematic noise. Sometimes, a low illumination source causes the signal measured to fall far below the sensitivity of the instrument, thus producing a noise which exceeds the true signal. Noise-equivalent-Delta-Radiance (Ne∆L or NeDL or NER): Defined as the radiance at a signal-to-noise ratio of unit. NeDL is the root mean square, or standard deviation of the mean, which produces an S/N of 1, reported in radiance (or irradiance) Units. This assumes that all known systematic errors are first removed. This measurement represents the lowest signal that can be measured by an instrument, just before the signal falls below the level of the Noise. NeDL is measured by viewing a stable, radiance source with the HandHeld 2 instrument. Noise Measurement: Since systematic noise is determinate, it should be removed prior to measuring the random noise signal of the spectrometer. For example, a dark current measurement should be recorded and subtracted from the signal. Then, as far as the


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spectrometer signal is concerned, all that should remain is random noise, including the small random contributions from the systematic errors. Offset: Systematic noise including dark current. Photodiode Array (PDA): A line of contiguous detectors manufactured into a single chip. Photon: There are two models for radiant energy, the particle model and the wave model. In the particle model, radiant energy is comprised of discrete packets called photons. A photon's electromagnetic energy is defined as:

Energy of photon = hf, where h is Planck's constant and f is the frequency of the electromagnetic energy.

The energy amplitude measured at a specific wavelength of frequency f is determined by the number of photons at that wavelength; i.e., amplitude for the wave model is equivalent to numbers of photons for the particle model.

Post-dispersive Spectrophotometers: All ASD spectrometers are “post-dispersive”. Because portable spectrometers are typically used outside the controlled laboratory environment, they are exposed to higher levels of ambient light. In almost all cases, some of this ambient light will stray into the sample being measured. The errors produced by this ambient stray light are much greater for a pre-dispersive spectrometer than they are for a spectrometer that is post-dispersive.

In a pre-dispersive spectrometer, the sample is illuminated with monochromatic light. Light scattered off or transmitted through the sample is then collected and delivered to the instrument’s detector. Ambient light that strays into the sample being measured is also collected. Thus, both the monochromatic illumination from the instrument and all wavelengths of the ambient stray light are delivered to the detector. Because the stray ambient light signal can represent a large fraction of the total light signal measured by the detector, it is a major source of error. While this source or error can be minimized by completely shielding the sample from all sources of ambient illumination, this often precludes the use of most reflectance and transmittance fiber optic probes.

In a post-dispersive spectrometer, the sample is illuminated with white light. Light scattered off or transmitted through the sample is then dispersed and delivered to the instrument’s detector. As with the pre-dispersive spectrometer, ambient light that strays into the sample being measured is also collected. The difference is that in the post-dispersive instrument, only ambient stray light of the same wavelength as that being measured by the detector is added to the signal resulting from the instrument’s illumination of the sample. Thus, the stray ambient light signal represents a small fraction of the total light signal measured by the detector. Precision: Precision is a measure of how close repeated measurements are around a particular value. Random Measurement Values: Even if all sources of systematic error are removed, there are always some remaining non-systematic differences between measurements made the


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same way on the same or equivalent samples. The number of times each of these measurement values occurs versus the measurement values approximately forms a “bellshaped” curve, or normal or Gaussian distribution about the mean or average, and the measurement values are called random. In this case, probability and statistics says that the best possible representative measurement is the calculated mean or average of many of these random measurement values. The difference between a particular measurement value and the average is called the deviation of that particular measurement value. The general spread of the deviations is characterized by the following calculations: Average deviation from the mean, root mean square (RMS) deviation, or standard deviation of the mean. Random Uncertainty (Random Error): The terms random error and random uncertainty are used interchangeably. Random error pertains to any uncertainty that is random. Deviation, standard deviation of the mean, and variance are all terms that are used to describe random error. Remote Sensing: The art and science of obtaining information about an object without being in direct physical contact with the object. Scattering: Sometimes a photon incident on a sample is absorbed by an electron in the sample (see Absorbed Energy). Shortly thereafter, this electron releases a photon. This electron-photon process is called scattering. (See also Raman scattering.) Signal-to-noise ratio (S/N or SNR): Ratio of the radiance measured to the root-mean-square (RMS) noise created by the detector and associated electronics. Parameters such as reflectance, sun angle and others affecting the signal must be defined to make the value meaningful (also see Noise-equivalent-delta-radiance). The standard built-in spectrum averaging function allows up to 31,800 spectra to be averaged, thereby reducing the noise and increasing signal-to-noise. As pointed out earlier, all systematic errors should be removed, then the signal should be measured as the average of several signals from the same or equivalent measurements. Then all that should remain is the sum of all random errors, which is characterized by the standard deviation of the mean and this should be used for N. This is the convention as stated in many texts on S/N calculation where it is often written that N is strictly the random noise. Sampling Interval and Spectral Resolution: Sampling interval is the spacing between sample points in the spectrum. All ASD spectrometers meet the Nyquist Sampling Criteria, that is, at least two sampling points to define a waveform peak or valley. Spectral resolution is another step beyond the Nyquist number and is a characterization defined by Rayleigh, Houston, Full-Width-Half-Maximum (FWHM) or Sparrow criteria. FWHM is the width at half the peak height for the narrowest monochromatic feature that can be detected by the spectrometer, for example the features of low pressure gas lamp emission lines (Figure 240).


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Figure 240: Full-width-half-maximum spectral resolution

FWHM is a convenient characterization; however, it does not provide complete information on the system’s ability to discern two adjacent distinct features. Accordingly, ASD has adopted the Sparrow Criteria, which is the wavelength separation between two monochromatic peaks necessary to identify the two as distinct peaks (Figure 241).

Spectrograph: Originally, the word “spectrograph” meant a device that would disperse light into a spectrum and record that spectrum onto photographic film. Early on, such devices were mostly used for identifying absorption lines in solar spectra and the spectra of burning gasses. Recently the word has also been used to describe devices that use photodetectors instead of film. Spectrometer (optical): From the Latin word specere, meaning image, and the Greek word metron, meaning to measure. A spectrometer is a spectroscope that uses some sort of mechanical or electrical detection device instead of the human eye. The words, “spectrometer” and “spectroscope” are often used interchangeably. Spectrophotometer: From the word “spectrometer” and the Greek phot, meaning light. A spectrophotometer is an optical spectrometer that is designed for computation of the ratio of the radiant energy of two different light beams as a function of wavelength. One of the beams is typically called the “baseline”, “reference”, or “white reference” and is often the

Wavelength

Sampling Interval

SpectralResolution

50%

of p

eak

heig

ht

Spec

trom

eter

offs

et c

orre

cted

raw

DN

Figure 241: Sparrow Criteria spectral resolution


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equivalent of the incident radiation. The output is typically “transmittance”, “reflectance”, or transformations of either. Spectroradiometer: (also see Radiometer) A spectroradiometer is an optical spectrometer that produces electrical signals, which correspond to radiant flux energy falling on its detectors for a series of discrete wavelength intervals. Spectroradiometers use single photoelectric detectors over which a spectrum is scanned and/or an array of detectors aligned in the spectrum path. Photoelectric detector current responds linearly to radiant flux energy while voltage responds logarithmically. Early spectroradiometers produced analogue electrical signals, while more recent spectroradiometers typically have built-in electronics for converting the analogue signal to digital. The signal output of a spectroradiometer may be calibrated to NIST traceable standards to produce measurements with radiance or irradiance units. Spectroscope: From the Latin word specere, meaning image, and the Greek word scopos, meaning to observe. A spectroscope was an early instrument for visually studying dispersed light. These devices included either a prism or diffraction grating for dispersing the light, telescopes for viewing narrow regions of the dispersed light, and protractors or other calibrated scales for measuring the position of a narrow region. Spectroscopy: Originally, the word spectroscopy meant the study of spectra using a spectroscope. Recently, the word has also been used to describe any study of spectra. Spectrum (optical): A spectrum is an image of radiant energy dispersed into its wavelength constituents, a two-dimensional plot of radiant energy or a two-dimensional plot of radiant energy ratio versus wavelength. Systematic Uncertainty (Systematic Error): The terms systematic error and systematic uncertainty are used interchangeably. A systematic error is any uncertainty that is determinate. Determinate means that it should be possible to determine the source of error, characterize it, and filter or subtract it from the signal. In contrast, the source of random errors cannot be determined. In some cases, systematic errors are conveniently linear, adding a constant bias to the signal. An example of a linear systematic error is the absorption of a solid lens on the spectrometer input. Since the concentrations of the chemicals in the lens and the physical structure of the lens does not change with time, absorption and refraction features in the lens can be characterized and subtracted from the signal. On the other hand, some systematic errors vary with time. An example of a time variant systematic error is the minor response drift associated with photo detectors as ambient temperature changes. (These are managed with ASD Driftlock, cooling, and frequent dark current updating). Since the goal is to get as close as possible to the true signal, systematic errors should always be characterized, measured and removed from the signal. Systematic Uncertainty Measurement: As pointed out above, there are always some non-systematic differences between same measurements, i.e. deviations. So, there must be random components associated with measurements of systematic errors. Since it is impossible to determine a measurement perfectly, what is meant by measurement of a systematic error is an average with a significantly smaller standard deviation of the mean


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than any of the other random measurement. In other words, measurement of systematic errors focuses on measuring relative systematic errors. Uncertainty: Any part of the measurement that does not correspond to the actual light energy reaching the spectrometer input. There are two types of uncertainty: Systematic error (or systematic uncertainty) and random error (or random uncertainty). Uncertainty does not include mistakes or goofs, such as bumping the spectrometer input, or calculation and rounding mistakes. Total experimental uncertainty is not limited to the spectrometer signal uncertainties, but includes all the uncertainties associated with the experimental set-up. For example, real-time reflectance measurements using a white reference panel also include the systematic reflectance errors of the panel. Vegetation Index Formulas: (Chistopher D. Elvidge and Zhikang Chen, Comparison of Broad-band and Narrow-band Red Versus Near Infrared Vegetation Indices, Desert Research Institute, June 29, 1994)

Ratio Vegetation Index (RVI) = NIR/Red Normalized Difference Vegetation Index (NDVI) = (NIR - red) / (NIR + Red) Soil Adjusted Vegetation Index (SAVI) = (1 + L)(NIR - red) / (NIR + red + L) Perpendicular Vegetation Index (PVI) = -cos α (red) + sin α (NIR), where α = angle between the soil line and the NIR axis. Difference Vegetation Index (DVI) = NIR - red

Wavenumber and Wavelength:

Wavenumber is the number of wavelength cycles per centimeter. Y (nm) = 107/X(cm-1) where Y = the number of nanometers (nm) and X = number of wavenumbers (cm-1) Resolution in cm-1, (Rcm-1) is dependent upon wavelength position. So, Resolution in nanometers, (Rnm) is calculated as follows: Rnm = +/- [Y - Y'] = +/- [107 / X] - [107 / X'] = +/- 107 * [1 / X] - [1 / (X - Rcm-1)]


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7. Maintenance & Trouble Shooting This chapter includes the following topics:

• AC/DC Power Supply, Batteries and Charger • Care and Cleaning Spectralon • Care and Cleaning HandHeld™2 • Care and Cleaning the Laser Pointer • Care and Cleaning of Optional Fiber Optic Jumper Cables • Care and Cleaning of Optional foreoptics • Care of Light Sources • Temperature Effects • Annual Factory Maintenance • Returning Instrument to ASD for Service • Trouble Shooting

7.1 AC/DC Power Supply, Batteries and Charger The FieldSpec® HandHeld 2 instrument also uses regular non-rechargeable AA batteries or other types of rechargeable AA batteries. However, do NOT use rechargeable Li Ion batteries. The battery specifications are:

• Type: AA Batteries: single use or rechargeable. Do NOT use Li Ion Batteries. • Rating: 1.2 Volts each • Performance: • The HandHeld 2 instruments runtime with a fully charged battery depends on

many variables including: battery age, instrument configuration, and environment

o Approximately 2½ hours for rechargeable nickel-metal-hydride batteries

o Approximately 5 hours for non-rechargeable lithium batteries

Recycle batteries and do not dispose of as general waste.

When installing new battery, first charge it fully before using it, regardless of if it shows full voltage and power.

Please refer to the separate instruction document for the battery charger.

7.2 Care and Cleaning of Spectralon® Spectralon is a product of LabSphere, Inc. North Sutton, New Hampshire USA and the following instructions are based on LabSphere’s instructions.


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Spectralon is an optical standard and should be handled in much the same way as other optical standards. Although the material is very durable, care should be taken to prevent contaminants such as finger oils from contacting the material’s surface. Always wear clean gloves when touching Spectralon.

If the Spectralon is lightly soiled, it may be air brushed with a jet of clean dry air or nitrogen. Do not use any compressed gas where Freon is used as the propellant. Freon will permanently discolor spectralon.

To clean a heavily soiled Spectralon:

Step 1 Remove the reference panel from the reference panel holder. To do so, unscrew the three hex screws (0.035 inch) two and a half turns.

Step 2 Place a flat surface, such as a thick piece of glass into the sink.

Step 3 Place 220 grade wet sandpaper onto the glass.

Step 4 Holding the edges of the sandpaper in place, gently rub the reference panel in a figure-eight motion over the paper until the panel is hydrophobic (water beads and runs off immediately).

Note: Be sure to follow these steps rather than setting the reference panel onto the glass and rubbing the sandpaper onto the panel—doing so will apply uneven pressure to the reference panel’s surface, thus creating areas of unequal reflectance.

Step 5 Use water as needed to wash away the thin layer which is sanded off.

Step 6 Blow dry with air or nitrogen, or allow the material to air dry for a minimum of 4 hours.

Step 7 When returning the reference panel into the reference panel holder, be sure to press down on it near the hex screw location while tightening each screw.

If the material requires high resistance to deep UV radiation, the piece should be prepared as above and then one of the following treatments should be performed:

1. Flush the Spectralon piece with > 18 milli-ohm distilled, deionized water for 24 hours.

2. Vacuum bake the Spectralon piece at 75° C for a 12 hour period at a vacuum of 1 Torr or less. Then purge the vacuum oven with clean dry air or nitrogen.

Note: DO NOT use oils or soaps to clean the Spectralon white reference.

7.3 Care and Cleaning of HandHeld 2 Instrument For safety reasons and to prevent damage to the instrument, please review all safety precautions in this manual.

Do not place objects on the unit or its power supplies. Keep objects and spills from entering or falling onto the instrument, power supplies, and software disks.


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HandHeld 2 is designed to withstand some light splashes of water, although these conditions should always be avoided. If splashing should occur, shut down the instrument, remove the batteries and disconnect the power supplies. Allow the instrument to completely dry for a day. If the AC/DC power supply has been dropped in water, return it to an authorized dealer or service center for examination or repair.

Note: The HandHeld 2 instrument is NOT designed to be submersed.

To clean the instrument:

1. Turn off the unit. 2. Disconnect from all power. 3. Allow the instrument to cool down. 4. Clean the instrument with slightly damp cloth and mild soap. Be sure all soap

residue is removed and all surfaces are dry before use.

7.4 Care and Cleaning of HandHeld 2 Optical Input and Foreoptics The HandHeld 2 instrument optical input is constructed from silica and the foreoptic lenses are made from high quality BK7 glass. As with any optics, protect HandHeld 2 instrument optical input and foreoptic lenses from scratches and dirt. Wipe with a slightly moist, clean cloth if necessary. Small scratches in the lens surface should not affect reflectance measurements significantly (or other unit-less ratio measurements).

Absolute energy radiometric calibrations are invalidated by broken or cloudy lenses as these calibrations are strongly dependent on clear intact optics at the time of calibration. In this case a new replacement and radiance calibration is required.

Keep water, dirt or small objects from getting inside a foreoptic body or sticking to the front of the foreoptic tube. An occasional check is recommended. Repair or replacement and re-calibration may be required if foreign objects get stuck inside.

The irradiance cosine collector may be cleaned like the lenses mentioned above. If the diffuser becomes too scratched or broken, a new replacement and irradiance calibration is required.

7.5 Care and Cleaning of the Laser Pointer

Protect the laser pointer output lens from scratches and dirt. Wipe with a clean cloth if necessary.

As with all high energy light sources, the laser can cause harm to eyes. Do not look directly into the laser output. For additional information on the proper use and safety practices of lasers, see the U.S. Department of Labor Occupational Safety & Health Administration OSHA Technical Manual (OTM) TED 01-00-015 [TED 1-0.15A] section III chapter 6, which includes references to the applicable American National Standards Institute standards for safe laser use: http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_6.html.


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7.6 Care and Cleaning of Optional Fiber Optic Jumper Cables Although the fiber optic jumper cables are designed to withstand a variety of field uses, care should be taken to prevent excessive forces on the fragile glass fibers inside the durable cable jacket. Tips on care for fiber optic jumper cables:

• Fiber optic cables should be loosely coiled and stored in the compartments provided. All accessories should be stored in the designated compartments of the carrier or in a separate protective case.

• The fiber optic jumper cable should never be stored with a bend diameter of less than a 5" diameter for long periods of time, the cable can be damaged with undetectable fractures that can cause decreased signals.

• Do not pull or hang the HandHeld 2 instrument by the fiber optic cable.

• Do not use wires, ties, or clamps to tightly attach the fiber optic cable to objects, this may pinch or penetrate the protective jacket thereby damaging the fibers inside.

• Avoid whipping, twisting, pulling, dropping, or slamming the fiber optic cable into objects. These actions can cause fractures to the glass fibers.

• While the tip of the fiber optic cable is not particularly susceptible to damage, a tip cover is recommended to protect against excessive abrasion and exposure to contamination. Replacement covers can be made by cutting pieces of eighth-inch shrink tubing to about 1.5" lengths and shrinking them onto the fiber optic cable tip. They will slide on and off the cable easily.

• The input end of the fiber optic jumper cable consists of the polished ends of the glass fibers embedded in epoxy potting. Clean the input end with a damp cloth and allow to dry, or blow dry with clean air or nitrogen. A lint-free tissue or lens cleaning cloth may also be used. If necessary, isopropyl alcohol can also be used to clean the tip.

• Small scratches in the input surface should not affect reflectance measurements significantly (or other ratio measurements). However, if the input surface becomes cloudy, the signal could be severely attenuated and a new replacement cable is recommended.

• Broken fibers in the fiber optic bundle will attenuate the signal. The signal loss of one or two broken fibers may be tolerated in reflectance measurements in an emergency (or other unit-less ratio measurements). However, we strongly recommend replacing the cable with a new one as soon as is practical.


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• Broken fibers or cloudy input surfaces are not tolerable in the case of absolute energy radiance or irradiance measurements, as these calibrations are strongly dependent on the clear intact optics at the time of calibration.

7.7 Care of Optional Light Sources We recommend that only light sources supplied by ASD Inc. be used with ASD instruments. Light sources supplied by ASD are designed to provide levels of illumination and stability of output that complement the performance of ASD instrumentation. To maintain the performance of the light sources:

• Prevent dirt and oils from contacting the bulb and reflector. • Do not touch the glass envelope of the bulb. Oils on the hand may transfer to the

glass envelope—this can significantly affect the bulb temperature and corrupt important operating physics of the bulb.

• Never touch the light source’s bulb and avoid contact with hot metal components near the bulb. Heat transfer from the light source may make these metal components uncomfortably warm to the touch.

Please refer to the ASD Accessories Manual for detailed information on specific accessories.

7.8 Temperature Effects The operating temperature range of the HandHeld 2 instrument is 0° to 40° C (32° to 104° F). If the HandHeld 2 instrument is exposed to intense direct sunlight or is exposed to ambient temperature outside the operating range, the internal temperature of the HandHeld 2 instrument may reach a point that could shorten the operating period. If the display fades or flickers or shows obvious errant spectra the system might be failing due to extreme temperature. Shut down and let the instrument cool or warm before operating again.

7.9 W.E.E.E. Compliance

ASD, Inc. supports the Waste Electrical and Electronic Equipment Directive (W.E.E.E.). ASD marks the instruments with the symbol at the left to show that this product has entered the market place after August 13, 2005. When the spectrometer reaches the end of its useful life, please do not discard it as general waste. ASD will accept the return of the instrument for recycling. Contact ASD Customer Service to arrange for return of the instrument.

7.10 Annual Factory Maintenance ASD recommends that the instrument be serviced once a year at the factory (or authorized factory service depot). This will ensure the proper function of the instrument. One


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performance check and re-calibration is covered under ASD's warranty or an optional extended warranty may be purchased.

Note: The customer must send the HandHeld 2 into the ASD factory for service.

7.11 Sending Instrument to ASD for Service For instructions on sending the instrument to ASD for service, please contact the Technical Support Department.

7.12 Technical Support If there are any questions or concerns, please contact ASD Inc. by phone, fax, or email: Phone: 303-444-6522 Ext-144 Fax: 303-444-6825 email: [email protected] Main Web Site: www.asdi.com Support portal: http://support.asdi.com/ Technical support is committed to providing a timely response to all questions. Technical support is available to answer questions Monday through Friday, 8 am to 5 pm Mountain Standard Time. We will respond to e-mail queries as well.

When contacting ASD Technical Support please have the instrument model and serial number, located on a label on the bottom of the HandHeld 2 instrument, available.(Figure 242).

Figure 242: HandHeld 2 instrument model and serial number label

The serial number is also accessible in the ASD applications software from the splash screen or the Help About menu item.

7.13 Trouble Shooting

Communication Errors: To fix many communication errors, power cycle the instrument and/or the instrument controller. The sequence to use will vary depending on the computer manufacturer. Either:


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Leave the computer on. Turn off the instrument. Wait for 10 seconds. Turn the instrument back on.

Or, turn off the computer and the instrument. Turn on the instrument. Then turn on the instrument controller. Unusual or Excessive Noise:

• An alternating current powered lamp can produce a sine wave pattern in the spectra. Noise or large spikes can occur in the data when using a low pressure gas emitter lamp, such as a fluorescent light. When using artificial illumination, always use a direct current (DC) powered lamp. Tungsten quartz halogen is preferred due to the good transmission of the quartz envelope and long term stability of the filament due to the halogen gas inside the envelope.

• If a lamp reflector or cover glass has two parallel, or coated surfaces, interference fringes can occur, appearing as sine waves in the signal. The solution is to remove the glass and/or use a more diffuse reflector.

• If using a fiber optic jumper cable, the signal will be reduced at the jumper junction by as much as 50%. Therefore, the random noise will be higher when using a fiber optic jumper cable compared to the bare input.

• Broken fibers in a fiber optic jumper cable can contribute to noise. Perform a fiber optic check to verify. This can be done by pointing one end of the fiber optic jumper cable at a safe light source so as to not cause damage to the eyes. Count the fibers on the other end by viewing with a magnifying lens. Most ASD VNIR type jumper cables have 19 fibers and all fibers should appear illuminated in a fully functional fiber optic jumper cable.

• An increase in noise can be due to a problem in the instrument, such as an electronic component malfunction or a grounding problem. This may be indicated by a regular pattern to the noise or periodic bursts of noise that are visible over the normal spectra.

• When the spectrum drops to zero after a dark current has been collected, this may indicate a problem with the shutter or dark current collection routine. To verify, optimize the instrument and listen for the click of the shutter activating. If the shutter click cannot be heard, contact technical support and obtain an RMA for sending the instrument in for repair.

• Significant changes in noise level can result from changes in illumination distance and angle. For artificial light sources, check and compare the set-up of the lamp from previous measurements. For solar illumination, check and compare the conditions present during the previous collection such as atmospheric conditions, time of day, seasons, etc.


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Background Interference: If the field-of-view spot size is larger than the sample or white reference panel such that unwanted background is entering the field-of-view, move closer to the sample or white reference panel. The field-of-view is conical-shaped, so moving it closer to the sample produces a smaller spot size.

If closer measurements are not practical, it may be necessary to acquire a larger white reference panel or a foreoptic with a smaller field-of-view.

Software Problems: To assure accuracy in the collection and processing of data, the ASD application software is designed to finish its current operation before moving on to the next routine.

The ASD RS3 software in tethered mode will stack up keystroke entries, and execute them later, in the order they were received. It is important to wait for the collection to finish before entering the commands to launch another operation. Do not rush into new operations or into issuing new commands until the results of the current command can be seen.

Non-ASD applications which can interfere with the ASD software are utility programs, network programs and those working in the background, such as virus checkers. ASD programs, require real-time access to the data that is being streamed from the HandHeld 2 instrument at a high rate of speed. Programs running in the background can cause packets to be lost.


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8. Specifications for Instrument, Computer, and Accessories This section contains the following topics:

• FieldSpec® HandHeld 2 Specifications • Optional External Controller Computer Specifications • Temperature Effects

8.1 FieldSpec® HandHeld 2 Specifications

Wavelength Range 325 - 1075 nm

Spectral Resolution 3 nm at 700 nm.

Sampling Interval 1.5 nm for the spectral region 325-1075 nm.

Spectrum file size Approximately 30 KB

Built-in Display 6.8 cm (2.7 in. diagonal) color a-Si TFT LCD, QVGA (240 (H) x 320 (V)) total pixel count

Power Power source: four AA batteries (Alkaline, Photo Lithium, or rechargeable NiMH) AC/DC Adapter: 100-240 VAC Input 5 VDC, 15 Watts Output

Temperature Range Operating Temperature: 0° to 40° C (32° to 104° F) Storage Temperature: 0°C to 45°C (32° to 113° F) Operating and Storage Humidity: 90% Non-condensing

Storage Internal and Flash memory: 1GB

Interfaces USB type A (2), USB type B, DC input power, Ext. Trigger

Body Dimensions Measurements with handle not attached (width, depth, height): 137 mm (W) by 203 mm (D) by 84 mm (H) (5.4 in by 8.0 in by 3.3 in)

Weight 1.04 Kg (2.3 lbs) without batteries


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8.2 Optional External Controller Computer Specifications The standard HandHeld 2 instrument does not include as standard an external controller computer. An external computer may be purchased separately from ASD or provided by the customer. The minimum requirements for the external controller computer are:

• 1.2 GHz Pentium or better notebook or PC-w/monitor • 256 MB RAM or more • 20 GB of free disk space • 1024 x 768 or better graphics resolution • 24-bit color or better - 32-bit recommended • (Optional) Serial communications port. (USB port) or blue tooth for optional GPS

receiver. Communication port required will be dependent of type of GPS receiver. • (Optional) NMEA compatible GPS receiver

The minimum requirements for the controller computer software are:

• RS3 Software from ASD • Microsoft Windows® XP/Vista/7 Operating System • Microsoft Internet Explorer 6.0 or better • Users need a basic understanding of the Microsoft Windows operating system,

including software installation. • International customers using non-English versions of Windows must alter the

Regional Settings under Start Settings Control Panel. The default language must be set to English (United States) in order for the software to be registered and to operate correctly. The numbering format must also be set to English.

8.3 Optional GPS Specifications ASD RS3 software requires the output of the GPS device to be in the National Marine Electronics Association (NMEA) standard 0183, RS232 serial port format. Check the GPS device documentation for output and port settings.

Install the GPS on the HandHeld 2 instrument or optional external controller computer. A serial-USB converter may be needed depending upon the controller and GPS device. The GPS feature is enabled in the ASD application software.

To configure the GPS select either:

1. GPS Settings... pull-down menu item (Figure 243).

Figure 243: GPS pull-down menu


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2. Or, use the keyboard command [Alt+G, S]. Refer to the GPS manual for further

instructions regarding usage and configuration.

Normally, the Baud rate (4800), Data bits (8), Parity (none), and Stop bits (1) settings will remain the same as what is displayed in the window. The Write to log file is checked by default. When this field is checked and the GPS fixed data is enabled, an entry will be made to a daily log file (i.e. 050302gps.log) when a spectrum is saved.

In the GPS Settings dialog box, enter communication settings appropriate for the computer port, as well as the GPS device.

Connect an appropriate cable between the instrument controller’s port and the GPS device.

8.4 Non-ASD Software The types of non-ASD applications that can interfere with the measurement of data are utility programs, network programs, and those working in the background, such as virus checkers. ASD programs require real-time access to the data that is being streamed from the HandHeld 2 instrument at a high rate of speed. Programs running in the background can cause packets to be lost.

Microsoft Office, image processing programs, and other software applications generally do not interfere with ASD programs, particularly if they are not running and competing for CPU cycles and RAM at the same time that data is being collected from the ASD HandHeld 2 instrument.

8.5 Artificial Light Sources Artificial light sources should use tungsten quartz halogen bulbs powered by stable DC power sources. The reflector should be made of metal and should not have any anodized coatings.


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Appendix A Radiant Flux, F : The amount of light energy that crosses a defined surface in a unit time.

Radiance, L : The Radiant Flux ∆F per unit projected area ∆Aproj per unit solid angle ∆Ω.

Allowing the quantities ∆F, ∆Aproj and, ∆Ω to be infinitely small:

L =

lim∆F → 0∆A → 0∆Ω → 0

∆F∆A cosθ ∆Ω

Using the equivalent second partial derivative form:

L = 1

cosθdF2

dAdΩ

which can be re-written in integral form:

L cosθ dΩ

Ω∫ =

dFdA

Da

b

c

dθ

e

∆A

Projected Area ∆A proj

xy

z

D

x

y

z

∆A

θ

∆Ω

∆Ω

Surface

D

φ

4π Steradians

Sphere

θ

∆Aproj

φ

∆A

Radiant Flux, ∆F


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where the ratio dFdA is known as the Irradiance, E.

Irradiance, E = dFdA . In other words, Irradiance is Radiance integrated over some part of

the sphere area.

Let dAproj = dAD proj ⇒

dΩ =

D2sinθ dθdφD2 = sinθ dθdφ

⎧ ⎨ ⎩

⎫ ⎬ ⎭

Then, the integral can be re-written as:

L cosθ sin θ dθ dφ

θ∫

φ∫ = E

This form is true for any “point-unit-area” on this surface so long as location of the “point-unit-area” is not an influence on the radiant energy.

If L is the same anywhere in this geometry, that is the medium is “isotropic”, the equation can be re-written as:

L

cosθ sin θ dθ dφθ∫

φ∫ = E

Since the integration is over a hemisphere, φ varies from 0 to 2π,

⇒ 2πL

cosθ sinθ dθθ∫ = E

⇒ 2πL

cosθ sinθ dθθ1

θ2

∫ = E

Let cosθ = u. Then, sinθ dθ = – du. And: u1 = cosθ1 , u2 = cosθ2 by chain rule for anti-

derivatives also known as "anti-differentiation by substitution" (see standard calculus texts such as James Hurley, Calculus, Wadsworth Publishing, pp. 211-216).

⇒ 2πL

u duu1

u 2

∫ = E

⇒ 2πL 12

u 22 - u1

2( ) = E

⇒ πL cos2θ2 - cos 2θ1( ) = E

θ varies from 0 to π.

⇒ θ2 = π2

, θ1 = 0

⇒ πL cos2θ2 - cos 2θ1( ) = E ⇒ E = π L

⇒ The amount of total integrated irradiance E falling on the “point-unit-area” is equal to π times the radiance L passing through the hemisphere to the “point-unit-area”.


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