Download Laser Distance and Speed Detection

Laser Distance and Speed Detection
Daniel Kaputa
EE 494 Dr. Cartwright
Feb 14th, 2001
Overview
? Motivation
? History
? Theory
? Applications
? Future
Motivation
? Many
applications
? Hope to implement laser
ranging into my robot
? Easy concepts and very
versatile
? There are many different
applications to laser ranging
History of Laser Ranging
1840’s, First remote
sensing used with
pigeons
? 1969, the first lunar
laser ranging done by
using reflectors placed
on the moon by Apollo
11
?
Theory
? There
are 3 types of laser distance measurements
1)Pulsed
2)Continuous wave
3)Interferometer Method
? Laser ranging is called LIDAR which stands for
Light Detection and Ranging
Pulsed Laser Ranging
? Short
duration and high power
1)Transmit pulse
? 2)Detect reflection
? 3)Measure time difference
? 4)Compute distance from speed of light
? Demo of Pulsed Laser
?
Pulsed Laser System
Non-cooperative Targets
Cooperative Targets
?
Typical retro-reflective device used in satellites
and on the moon
How to Compute the Distance
2R = C*Tr
R = distance
C = speed of light
Tr = total travel time
30 cm over kilometers precision
Continuous Wave
? Frequency
modulated laser ranging
We know that:
? 1)Light
travels in straight lines
? 2)Laser light is coherent
? 3)We know the speed of light
Therefore we can compute the exact distance
that the light has traveled
Beam-modulation Telemetry
How to Compute the Distance
? Frequency
= (1/time) = (C/wavelength)
? 100KHz = wavelength of 3x10^12 meters
Tr = roundtrip time
? r = phase
How to Compute the Distance
2R = C*Tr
R = distance
C = speed of light
Tr = total travel time
1 cm over kilometers precision
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
Triangulation
Triangulation is a
method of determining
distance by using
angles and
trigonometry.
? There are many
different types of
triangulation.
?
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.
Satellite Systems (SLR)
Determine position of
Earth’s satellites
? Topography
? Oceanography
? Gravity Waves
? Plate Tectonics
?
Sensing of Surface Elevations
Rangefinders
Uses pulses of infrared
light
? Based on time difference
from transmission to
reception
? Bushnell's Page
?
Many Uses for Rangefinders
Golf
Hunting
Architecture
Ranging Video
Speed Traps
?
pulsed light is used and 2 or 3 readings are taken to
determining the velocity of the moving object
3D Body Scanning
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 vehicle
on earth
?
Step 1
?
The vehicle
determines how far
away the first satellite
is from it. Either
pulsed or CW
techniques can be
used.
Step 2
?
The vehicle determines how far away a second satellite is
from it.
Step 3
?
The vehicle determines how far away a third satellite is
from it. Then it can combine all of the information and
determine where on Earth it is located.
The Future of LIDAR
? In
the future laser
ranging will
become more
precise and
cheaper, and many
new applications
will be
implemented
LITE
Lidar-in-space-technology-experiment
Used to measure
clouds,
atmospheric
conditions,
asteroids, and
topography
Improved Accuracy
Bibliography
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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