How often laser guns need to be adjusted

Question

How often laser guns need to be adjusted

Answer 1

These devices measure distances by pulsing an infrared laser diode, measuring the “time of flight” to the target and back as well as the time interval between the distance measurements. Dividing the change in distance by the time interval allows the average speed during that interval to be computed. The problem is, if the laser beam illuminates a different (closer) area of the target between successive pulses, the “distance change” will be greater (if the target is moving toward the gun) than if the two consecutive pulses returned from the same area of the target. This causes the speed calculation to be greater than it would if the two pulses reflected from the same area. These devices are aimed with a telescope from considerable distances, so even a slight motion of the operator can produce erroneous results. For example, since it is change in distance over a known interval of time that is being measured, just moving the aim point can cause a stationary target to be displayed as having some finite speed with respect to the laser gun!

"The basic operation problem is that handheld laser speed guns must take two separate measurements of distance to generate a speed estimate. If, while taking a speed reading, an officer's hand twitches slightly, the laser beam can "slip" from one portion of a vehicle to another. The extra distance measured in the second reading is then added to the calculation that determines the speed readout. For example, if the speed gun's aim point slips from the windshield to the grill, the speed reading will read 8 MPH too high."

Laser guns as weapons are another matter. They do require frequent adjustment and maintenance. And worse, they don’t deliver any appreciable momentum to the target, just energy. So they need to dwell on the target long enough for the target to absorb enough energy to be destroyed, thus requiring constant adjustment in the aim point over a significant (but classified) period of time. On the up-side, the time of flight compared to projectiles is negligible and the range can be enormous. The armed forces of the United States is currently testing and evaluating laser weapons for battlefield deployment in the near future.