Menq Presenter, J Pan University of New York at Buffalo Electrical
Table of Content
What is L.I.D.A.R.? Motivation Varies Types/Techniques Other Applications Summary Reference
University of New York at Buffalo Electrical
What is it?
LIDAR acronym for Light Detection and Ranging. Uses laser as light source. Remote sensing, to measure, observe, and monitor without making actual physical contact. Major techniques: Range finding, Differential Absorption (DIAL), and Doppler.
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Motivation
The Clean Air Act Amendments. Capable of obtaining small particle in the air, such as aerosols. Obtain higher spatial resolution, thus better resolution in underwater imaging. Crosswind detection, turbulence sensor.
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Backscattering Method
Simplest Lidar techniques. Detects elastic scattering of laser pulses by aerosols or small particles suspended in the air. A laser pulse is transmitted to the atmosphere and scattered. Profiles of the aerosols can be visualized by collecting the backscattered light with high speed detectors.
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Backscattering method
Doppler Infrared Lidar Sensor
Use 2-m Tm:YAG Clear-Air Turbulence Detect the shift in frequency of the backscattered pulses due to the motion of aircraft. Highly variable velocities along the laser beam indicate the presence of clearair turbulence.
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Backscattering Method
Nd:YAG that can be frequency doubled and tripled, and Qswitched 160-mJ to 500-mJ per pulse. 10-Hz Rep Rate. Photomultiplier tubes and RCA avalanche photodiode.
Altitude-time plot taken by Shuttle Discovery with LITE in a 1994 mission.
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Differential Absorption
Absorption Spectra
Molecules vibrates, spins, and rotates differently. Distinct emission of light in different materials.
Wave Length
Resonant losses
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Differential Absorption
2.0-m Telescope
Sugimoto s high altitude ozone Lidar.
Low-Altitude System Transient recorder PMT
D2 Chopper
308 XeCl 339 351-nm
XeF
Photon Counter
Mini Computer
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Differential Absorption
Tracking Beam 500-mJ - - 50-Hz - 2 CO2 Laser Signal beam Tracking System Retroreflected beam 50-cm Retroreflected Mirror Atomosphere Reference beam
Data System
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Bathymetry
Triangulate the target by illuminating it with a laser, then capture the reflection with a CCD Camera.
Scanner CCD Camera
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Bathymetry
Airborne or underwater. Utilized frequency doubled pulse Nd:YAG (532nm). Blue-green laser minimizes water absorption.
Laser scanner Linescan CCD camera Pixel FOV Laser beam Main housing
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Bathymetry
Each pulse generates a pixel. Operating at repetition rate of several kilohertz.
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Bathymetry
Above taken by US Army Corps of Engineers
Lake Tahoe of Nevada
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Other Applications
Airborne mapping of beach erosion.
Fly over beach at 135-mph with GPS. High rep rate needed.
Protects against biological warfare agents
Consist of a infrared transmitter, receiving telescope, and a detector with an information processor integrated into the frame.
Air cool laser with high energy-perpulse mounted on helicopters.
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Other Applications
Wind profiling Lidar for Air Drops
Mounted on C-130 transport. Provide 3-D maps of wind from altitude to ground. Eye-safe Tm:YAG, 2-m, 12-mJ/pulse at 100Hz. Weight 600-lbs and occupies 45-ft2.
University of New York at Buffalo Electrical
Summary
Capable of real-time data analysis, widearea surveillance and multi-material measurement analysis. Good tool for understanding the environmental changes. Room for improvement. Potential for image recognition.
University of New York at Buffalo Electrical
Reference
N. Sugimoto, Appl. Opt., (1993) 162-70. Joe Leonelli, Photonic Spectra, (June 1995) 97-106. Yasuhiro Sasano, Appl. Opt., (1982) 3166-69. Pat Cross, http://aesd.larc.nasa.gov/GL /tutorial/gallery.htm#lidar Timothy L. Miller, http://wwwghcc.msfc. nasa.gov/sparcle/what_lidar.html Kathleen G. Tatterson, Photonic Spectra, (Feb 1998) 20-21. Karl D. Moore, Jules S. Jaffe, Ben L. Ochoa. Scripps Inst. Oceanography, La Jolla.
University of New York at Buffalo Electrical