LIDAR Systems presented by Paul Gelsinger

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LIDAR Systemspresented by Paul Gelsinger
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What is it?

• LIDAR stands for Light Detection and Ranging
• Also known as Laser Radar, Optical Radar, and
  LADAR

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What is LIDAR used for?

• LIDAR is a tool that is used for
• Measuring Distances
• Measuring Velocity
• Determining Atmospheric Composition

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What Does a LIDAR System Consist of?

• Laser
• Light collection device (telescope)
• Electronic Detector
• High Speed Electronic Counter

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Three Main Types of LIDAR

• Range finders
• - Measures distances
• DIAL (Differential Absorption LIDAR)
• - Measures concentrations of different chemicals
  in the atmosphere (ozone, water vapor,
  pollutants)
• Doppler LIDARS
• Measures velocity

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How Does Ranging LIDAR work?

• An optical pulse is generated by a laser
• The pulse is reflected off of an object and
  detected by a receiver
• The round trip time of the pulse is measured by a
  high speed counter
• Time is converted to a distance using the
  equation
• d (ct)/2

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What Does a Ranging LIDAR System Look Like?

• This particular system uses
• ? 532nm
• Pulse length 15ns
• Pulse rate 30 Hz
• 20-cm refracting telescope
• 10-nm interference filter
• photomultiplier tube
• beam divergence 62 mrad

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The Actual System
Detector
Laser
Telescope
Optics
Detector
Electronics
Photos courtesy of National Oceanic and
Atmospheric Administration
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Another Application of Ranging LIDAR
A new victim!
LIDAR
Oh no! Im late for Opti 422!
Police
Pulsed LIDAR Beam
Pulsed Return Beam
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How Does DIAL Work?

• Differential Absorption LIDAR
• Uses two lasers with different wavelengths
• - One wavelength is absorbed by the molecule of
  interest
• - The other is not absorbed
• The intensity of the two return signals can be
  used to deduce the concentration of the molecule
  of interest

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DIAL
I1,2
I1,2
DIAL
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How Does Doppler LIDAR Work?

• Uses the Doppler effect to measure velocity
• - The wavelength of light is changed upon
  reflection from a moving object
• - Object moves toward observer blue shift
  (shorter ?)
• - Object moves away from observer red shift
  (longer ?)
• Mainly used for determining wind velocities

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Doppler LIDAR
Direction of wind
Original LIDAR Beam
LIDAR
Red-shifted Beam
Wind with dust
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Questions?

• Email pgelsing_at_email.arizona.edu