Laser detection (also called "LIDAR") is the latest method used by NYC police for speeding tickets. The Laser gun fires an incredibly short pulse of laser light at your car at the speed of 186,000 miles per second. The gun incorporates a miniature clock and computer which measures the time that the beam takes to reflect back off of your car, and converts this into a measurement of the distance between the gun and your car. Thus the radar gun is being used as a range finder.
The gun will then send another pulse within fractions of a second, and will use that pulse to make a second measurement. The computer then divides the change in distance by the time between pulses to come up with the speed of your car.
Just as in radar speeding cases, the police officer is only required to have taken a recent course which is directed on how to operate, troubleshoot and calibrate the laser gun. He is not expected to be an expert on the gun or the technology.
To be valid in court, the gun must be calibrated by the officer before each shift. Typically the officer will stand on a prepared mark and fire the gun at two different objects which are at pre-measured distances from the mark. This measures the range-finding function. However this calibration does not measure the timing between the pulses which, in my view, makes it flawed.
While the weakness of the radar gun is that the beam diverges too much, covering the entire roadway, the beam of the laser gun is so tight (coherent) that it is possible for the gun to just miss your car by inches and hit another car. Thus the speed reading could be for someone else's car, not yours.
I am available for a no obligation free telephone consultation about your speeding ticket case.
