ProMetric I-Series

ProMetric® I-Series

Accurate Color and Luminance Measurements

A KONICA MINOLTA Company


2 I Radiant Vision Systems, LLC

IntroductionThe Radiant Vision Systems family of imaging colorimeter products are designed

to provide highly accurate color and luminance data in high volume manufacturing

settings. These products utilize lenses with electronically adjustable focus and aperture

settings. This unique capability provides significant benefits in usability, measurement

flexibility and measurement accuracy.

This note explains the general calibrations required for imaging colorimeters. It also

explains the specific calibrations that enable Radiant Vision Systems ProMetric I-series

imaging colorimeters to provide highly accuracy data in high volume manufacturing

settings.

Calibrations in Imaging ColorimetersTo get accurate color and light measurements, imaging colorimeters rely on two

primary calibrations:

1) A flat-field calibration that is performed at the factory.

2) A luminance and color calibration that is performed by the user for a specific DUT type.

Flat-Field Calibration Flat-field calibration is performed at the factory using a Uniform Light Source. The flat-

field calibration is used to remove any variations in lenses or CCD sensitivity. The lens

characteristics will change at different focal distances and aperture settings, so it is

necessary to create a flat-field calibration for each specific focal distance and

aperture setting.

In past generation products, this was generally performed at one or two specific

distances and one or two specific aperture settings. The impact of this was:

• The colorimeter had a limited number of settings where the calibration was

most accurate.

• It required the user to load specific calibration files (based on the distance and

aperture for the current measurement).

The ProMetric I-series incorporates Smart Technology. This includes:

• Smart Control™ for electronic focus and aperture control

• Smart Touch™ for on imaging colorimeter measurement set-up and control

• Smart Calibration™ for automated, accurate application of calibration settings

Together, these features simplify operation and ensure the best possible measurement

accuracy, because a user does not have perform their own flat-fielding calibration for

every different working distance.

Accurate Color and Luminance Measurements with ProMetric I-Series



With the ProMetric I-Series, the colorimeter and any lenses supplied with it are factory

calibrated over all possible distances and two specific aperture settings (see table below).

This means you can make measurements at any distance with those apertures and be

assured that you are making a calibrated measurement. The colorimeter will automatically

apply the correct flat-field calibration data, at the working distance you specify. With

ProMetric I, you get more flexibility and more accurate measurement results.

Luminance CalibrationTo measure luminance, imaging colorimeters use internal filters, designed so that the overall

spectral response closely matches that of the human eye. At the factory, the colorimeter and the

internal filters are calibrated against a light source that has very broad spectral content, such as

a halogen or fluorescent bulb. Any uncertainties in the filter are calibrated out and you have very

accurate luminance measurements for any light source that has similar spectral content.

For your measurement, you will likely want to measure a DUT that has a different spectral

content than the source used for the factory calibration. As an example, an LED or a Flat Panel

Display with LED backlight has spectral content that is located in very narrow portions of the

visible spectrum. This is quite different than a halogen or fluorescent bulb.

To get the most accurate luminance measurements for your DUT, you’ll want to recalibrate

using your specific DUT type. This calibration is performed by using a reference measurement

device, like a spectrometer, to measure the DUT at the same time you are capturing a

measurement with the colorimeter.

The value from the reference device is entered into the colorimeter control software, and you

now have accurately calibrated luminance measurements for that specific type of DUT at

that specific aperture setting. You can save the calibration value in a calibration file, such as

“Luminance cal for new LCD display,” and recall it whenever you are measuring that specific

type of DUT.

Proper calibration is a critical part

of making accurate measurements.

Understanding and applying the

calibrations correctly will ensure your test

results are accurate and repeatable.

Calibrated Apertures by Lens

Lens

Focal Distance

Minimum Working Distance

FilterThread

Calibrated Apertures Max: Min:

Canon EF 24 mm f/2.8 USM

24 mm 175 mm 58 mm f/4.7f/8

Canon EF 35 mm f/2.0 USM

35 mm 260 mm 67 mm f/2.3f/8

Canon EF 50 mm R f/2.0 USM

50 mm 260 mm 67 mm either f/2.3 or f/4f/8

Canon EF 100 mmf/2.8 Macro USM 100 mm 310 mm 58 mm

f/3.3f/8

Canon EF 200 mmf/2.8 USM 200 mm 1500 mm 72 mm

f/3.3f/8



With the ProMetric I, for accurate luminance measurement, you need only be concerned

with the DUT type, not the aperture settings. Because of the electronically controlled

aperture, the colorimeter knows the current aperture settings and applies appropriate

calibration data that was generated as part of the factory calibration. To get accurate

luminance measurements, you simply do a single luminance calibration on your specific

DUT type, and you can reuse that calibration file for any distance, any aperture and any

similar DUT.

Color CalibrationColor calibration is very similar to the luminance calibration described previously, except

the calibration is for three internal filters instead of just one. Color filters are calibrated at the

factory, but to get the most accurate measurements with your DUT, you’ll want to recalibrate

using a reference that has spectral content that is similar to your specific DUT type.

“Four-color” calibration is used when measuring RGB based devices (like a flat panel

display) that produce a variety of colors using R, G, and B primaries. Monitors use these

primaries to make virtually any color, including black and white.

“One-color” calibration is used when measuring simple devices that produce a single color

of light, like a light bulb, LED, headlamp, laser, etc. All of these devices are either off (not

producing light) or on (producing light).

Other types of advanced color calibrations are also available to accurately measure a wide

variety of color emitting devices.

To perform calibrations, you follow a simple procedure similar to that described for

luminance, except you will be entering multiple values into the control software (not

just one). Just like luminance, you save these values in a calibration file and recall them

whenever you measure a similar type of DUT.

With the new ProMetric I with the electronically adjustable lenses you should continue to

perform a color calibration for your specific DUT type. However, you no longer need to be

concerned with any changes in distance or aperture because these values are not impacted

by spectral content of different DUT types. They are pre-calibrated in the factory and

applied automatically.

SummaryProMetric colorimeters utilize electronically controlled lens and have factory calibrations

for all distances and two specific aperture settings. We also utilize highly accurate flat-

field calibrations and simple luminance and color calibrations. Radiant Vision Systems

colorimeters are the easiest to use, most flexible colorimeters on the market and deliver

the best measurement results.

Previous generation imaging

colorimeters required very close

monitoring of the measurement set up;

the operator needed to confirm correct

calibration data was used whenever a

change was made. With ProMetric I,

the new electronic lens and calibration

method automatically applies correct

calibrations and removes this burden

from the operator.

©2015 Radiant Vision Systems, LLC. Radiant Vision Systems and ProMetric are trademarks of Radiant Vision Systems, LLC. All other marks are the property of their respective owners.770-4004-05 6/2016

Contact Us

Global Corporate Headquarters

Radiant Vision Systems, LLC

22908 NE Alder Crest Drive, Suite 100

Redmond, WA 98053 USA

T. +1 425 844-0152

F. +1 425 844-0153

[email protected]

RadiantVisionSystems.com

Radiant Vision Systems ProMetric I-Series utilize lenses with electronically

adjustable focus and aperture settings, providing significant benefits in usability,

measurement flexibility and measurement accuracy. Calibration is now greatly

simplified. Contact us to find out more.


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ProMetric I-Series