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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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How to Compute the Distance
?Frequency = (1/time) = (C/wavelength)
?100KHz = wavelength of 3x10^12 meters
Tr = roundtrip time
? r = phase
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How to Compute the Distance
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