Laser Distance and Speed

8/12/2019 Laser Distance and Speed

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Laser Distance and Speed Detection

Daniel Kaputa

EE 494 Dr. Cartwright

Feb 14th, 2001


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Overview

?Motivation

?

History?Theory

?Applications

?

Future


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Motivation

?Many applications

?

Hope to implement laserranging into my robot

?Easy concepts and very

versatile

?There are many different

applications to laser ranging


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History of Laser Ranging

? 1840s, First remote

sensing used with

pigeons

? 1969, the first lunar

laser ranging done by

using reflectors placed

on the moon by Apollo11


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Theory?There are 3 types of laser distance measurements

1)Pulsed2)Continuous wave

3)Interferometer Method

?Laser ranging is called LIDAR which stands for

Light Detection and Ranging


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Non-cooperative Targets


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Cooperative Targets

? Typical retro-reflective device used in satellitesand on the moon


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How to Compute the Distance

2R = C*Tr

R = distanceC = speed of light

Tr = total travel time

30 cm over kilometers precision


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Continuous Wave

? 1)Light travels in straight lines

? 2)Laser light is coherent

? 3)We know the speed of light

?Frequency modulated laser ranging

We know that:

Therefore we can compute the exact distance

that the light has traveled


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Beam-modulation Telemetry


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?Frequency = (1/time) = (C/wavelength)

?100KHz = wavelength of 3x10^12 meters

Tr = roundtrip time

? r = phase


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2R = C*Tr

R = distanceC = speed of light

Tr = total travel time

1 cm over kilometers precision


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Factors affecting accuracy

1. Frequency of the tone or modulation.

2. Accuracy of the phase-measurement loop. This depends on

signal strength, noise, and so on.

3. Stability of the modulation oscillator.

4. Number of cycles (or measurements) that can be averaged

together for a range. measurement.

5. Turbulence in the air through which the. measurement is

made.

6. Variations in the index of refraction of the air.

Taken from http://cord.org/cm/leot/Module6/module6.htm


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Triangulation

? Triangulation is a

method of determining

distance by usingangles and

trigonometry.

? There are many

different types oftriangulation.


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Applications of LIDAR

?There are countless applications for this

new emerging technology.?Anything previously measured by hand can

be measured by lasers with much more

accuracy.

?Examples.


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Sensing of Surface Elevations


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Rangefinders

? Uses pulses of infrared

light? Based on time difference

from transmission to

reception

? Bushnell's Page


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Speed Traps

?pulsed light is used and 2 or 3 readings are taken to

determining the velocity of the moving object


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3D Body Scanning


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GPS(Global Positioning System)? GPS uses several

satellites and the concept

of triangulation.? For this example there are

3 satellites that are used

to pinpoint the location of

the transmitting vehicleon earth


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Step 1

? The vehicle

determines how far

away the first satelliteis from it. Either

pulsed or CW

techniques can be

used.


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Step 2

? The vehicle determines how far away a second satellite isfrom it.


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Step 3

? The vehicle determines how far away a third satellite isfrom it. Then it can combine all of the information anddetermine where on Earth it is located.


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LITE Lidar-in-space-technology-experiment

Used to measure

clouds,

atmospheric

conditions,

asteroids, and

topography


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Improved Accuracy


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Bibliography? Slide 2,26,27,28,29 Trimble How GPS Works Step 1

? Slide 3 EyeWire

? Slide 4 Remote Sensing Tutorial Overview

?

Slide 8,9,12,13 Module 6: Laser Distance Measurement? Slide 20,21,33 http://ilrs.gsfc.nasa.gov/slrover.pdf

? Slide 16 Better Optical Triangulation through Spacetime Analysis

? Slide 17 Technology

? Slide 18 Laser vs. LED vs. Superluminescent LED

? Slide 22,23 Bushnell Sports Optics Worldwide? Slide 24 Laser

? Slide 25 http://www.tc2.com/RD/RDBody.htm

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Laser Distance and Speed