LIDAR Light Detection and Ranging

1
LIDARLight Detection and Ranging

• Kate Whalen
• PHY 3903
• Nov. 25, 2005

2
Outline

• Some applications
• How lidar works
• Examples of current lidar projects
• Purple Crow Lidar
• Dalhousie Raman Lidar

3
Applications

• Distance measurements
• Atmospheric composition
• Weather
• Mapping
• Speed measurements

4
Lidar Basics

• Active remote sensing
• Light is emitted, scattered, and detected.
• Since we know the speed of light, we can measure
  the distance travelled!

5
Details

• 3 main parts
• Transmitter
• Example Pulsed NdYAG laser (532 nm)
• Low beam divergence
• Narrow spectral width
• Receiver
• Optical telescope
• Detector
• PMT
• Chopper
• Eliminates near-field returns

6
Purple Crow Lidar (UWO)

• Detector consists of a 2.65 m mercury mirror,
  rotating at 10 rpm
• Parabolic mirror
• 532 nm NdYAG laser used for Rayleigh scattering
• Elastic scattering at 30-90 km
• Obtain T(z) from density profile
• Assumptions
• Hydrostatic equilibrium
• Ideal gas

7
PCL Projects
8
Dalhousie Raman Lidar

• CABOT Observatory
• Canadian Atmosphere-Biosphere Observations
  Trailer
• 607 nm NdYAG laser
• Raman scattering
• Inelastic scattering (change in rotational or
  vibrational energy)
• Frequency of scattered photon depends on
  temperature, type of molecule
• Investigates atmospheric aerosols clouds
• Transboundary pollution transport

9
CABOT Projects
10
In Conclusion

• Lidar is an example of physics for the benefit of
  the planet!

11
References

• Thanks to Dr. Bob Sica and the PCL group at UWO!
• Argall, P. S. R. J. Sica, Lidar (Laser Radar).
  In The Encyclopedia of Optics, Vol. 2, Ed. T. G.
  Brown et al., Wiley-VCH, Weinheim, 2005.
• Duck, T. J. et al., Lidar measurements of
  atmospheres. Physics in Canada 61 (5) 247-252,
  2005.
• Sica, R. J. et al., Lidar measurements taken with
  a large-aperture liquid mirror. 1.
  Rayleigh-scatter system. Applied Optics 34 (30)
  6925-6936, 1995.
• Environment Canada Air Quality Processes
  Research Division Online. http//www.msc.ec.gc.c
  a/arqp/index_e.cfm Nov. 24, 2005.
• Purple Crow Lidar Online. http//pcl.physics.uwo
  .ca/ Nov. 24, 2005.
• REALM Regional East Atmospheric Lidar Mesonet
  Online. http//alg.umbc.edu/REALM/ Nov. 24,
  2005.
• The Atmospheric Optics Laboratory Online.
  http//aolab.phys.dal.ca Nov. 24, 2005.