Laser Range Finder Mech 207 – Advanced Mechatronics I TJ Leising October 23, 2009
Dec 18, 2015
Laser Range FinderMech 207 – Advanced Mechatronics
I
TJ Leising
October 23, 2009
Introduction Laser light basics
– Propagates dominantly in one direction in the form of a beam
– Beam can maintain integrity for very long distances
Lasers are ideal to measure distances– Different methods used to measure different lengths– i.e. Triangulation and Time of Flight
All photos courtesy Acuity
Introduction (cont.) Time of Flight
– Measures the time the laser take to travel the distance and back
– Short pulse fired out and time measured for a reflected portion to come back
– Longer time = farther away– temporal accuracy must be very high – e.g. 1 ns for a
spatial accuracy of 15 cm
Triangulation– Have sensors offset to measure angle of reflectance– Based on geometry, distance can be determined
Courtesy: Sensorland.com
Courtesy: Physorg.com
Laser Physics Laser Light is:
– Monochromatic: it contains one specific wavelength of photons
– Coherent: All the photons have wave fronts that are in unison
– Directional: Propagates generally in one direction in a concentrated
beam
Atoms are excited and release photons that travel down the tube reflecting off mirrors and exciting more atoms untilthey leave the tube through a lens in a concentrated laser beam.
Implementation Laser is installed to additional sensing
circuitry A photo sensor receives the reflected signal
– Triggers “timer stopping” circuitry or “angle valve” input
Data from the time of flight or the angle of impact is used to determine the distance to target
Courtesy: philohome.com
Applications Recreation
– Golf and Hunting
Production Control– Keep a level surface
3-D mapping– For robotics or scouting
High Precision Guidance– Missiles, Targeting Computers
Courtesy: binocularsdirect.com
Courtesy: seattlerobotics.org
Courtesy: foxnews.com
Challenges Issues with lasers
– Tend to be expensive– Dependent on line-of-sight (wall vs. chair)– Can involve complicated circuitry that might not be
necessary– Laser pointing fluctuations– Laser noise issues
Courtesy: Encyclopedia of Laser Physics
References Encyclopedia of Laser Physics and Technology
– http://www.rp-photonics.com/
Acroname Robotics – http://www.acroname.com/
Acuity Laser Measurements– http://www.acuitylaser.com/products.shtml
Sensorland.com– http://www.sensorland.com/HowPage056.html
Encoder: The Newsletter of the Seattle Robotics Society– http://www.seattlerobotics.org/encoder/200110/vision.htm
How Stuff Works– http://www.howstuffworks.com/