The lidar gun clocks the time it takes a burst of infrared light to reach a car, bounce off and return back to the starting point. By multiplying this time by the speed of light, the lidar system determines how far away the object is. Unlike traditional police radar, lidar does not measure change in wave frequency. Instead, it sends out many infrared laser bursts in a short period of time to collect multiple distances. By comparing these different distance samples, the system can calculate how fast the car is moving. These guns may take several hundred samples in less than half a second, so they are extremely quick, accurate.
Police may use handheld lidar systems, just like conventional radar guns, but in many areas, the lidar system is completely automated. The gun shines the laser beam at an angle across the road and registers the speed of any car that passes by (the system makes a mathematical adjustment to account for the angle of view).
Laser Jamming
This works basically the same way as a radar jammer. In addition to
a light-sensitive panel, the detector has its own built-in light-emitting
diodes (LEDs) that produce a light beam of their own. When this beam shines
on the lidar system, the receiver can't recognize any reflected light and
so can't get a clear speed reading.
It's important to note that none of these systems are 100-percent effective; even with a top-of-the-line detection and jamming system, the police still might catch you speeding, and can by other means (Pacing, Vascar/Aircraft). Also, since police periodically introduce new speed-monitoring technology, a detector might suddenly become outdated. Whenever this happens, the fully equipped speeder has to dump everything and pick up all new equipment.
Modern detectors may also include a light-sensitive panel that detects
the beams from lidar guns. These devices are more difficult to evade than
traditional radar because the beam is much more focused and it doesn't
carry well over long distances. By the time a detector recognizes the presence
of the laser beam, the car is most likely in the beam's sights already.
Some speeders try to get around these systems by reducing the reflectivity
of their car. A black, or more so, FLAT Black surface reduces reflectivity
because it absorbs more light. Drivers can also get special infrared absorbing
plastic covers that reduce the reflectivity of license plates, or do defract
the beam completely. These measures only reduce the effective range
of the lidar system, and does not increase the effective range of the driver's
detector. With this extra time by using paint and plastics, a speeder
might be able to slow down before the lidar gun can get an active read
on his or her speed.
For best protection, keep in minde that:
Your vehicles liscense plate, and headlights are the primary targets
of a laser gun. Mounting a detector on the front windshield is the
best position to improve detection at short range.
Do not follow closely behind any other vehicle you can't see through. Chances are, if you can't see through it, neither will your laser detector.
The recieving range of your laser detector will not be near the same
as your radar detector. Laser guns are most often used at short range.