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Laser Defence – How does it work?

First a brief basic explanation on how LIDAR (Laser) guns and LIDAR (Laser) Cameras operate. LIDAR (Light Detection And Ranging) devices are often used determine vehicle speed, these devices are generally in the form of hand held or tripod mounted LIDAR 'gun' and increasingly LIDAR cameras which can be mounted in parked vehicles, on tripods or from fixed mounting positions, note LIDAR can only operate when stationary. These units operate by sending out a very narrow beam (similar to a Laser pointer) of high power but very short pulses of infra-red laser light (904~905nm), this infra-red light is not viable and is similar to the infra-red light used by most television remote controls. The pulsed light is reflected off the vehicle back to the LIDAR units receiver, variations in the time and phase between the transmitted and the received pulses can then be used to determine vehicle speed and distance.
The vehicle registration plate is generally used as the primary target for the hand held unit as registration plates are normally flat and coated with a surface which highly reflective to infra-red light, other flat panels and headlights can also provide a good target, hand held units are normally only transmitting a signal when the LIDAR operator takes aim and pulls a switch.

LIDAR cameras operate buy sending a swept laser beam across the road, these units can work across multiple traffic lanes in both directions and depending on the set up can determine vehicle speed from the front or rear of a vehicle. These units can even be set up to determine vehicle size with variable speed enforcement for different size vehicles. These cameras are constantly transmitting Laser pulses while in operation. LIDAR speed measurement equipment can often obtain an accurate vehicle speed in well under a second.

Laser Jammers are devices designed to try and stop LIDAR guns and cameras from getting a valid speed reading from a vehicle. The jammer has an infra-red receiver and infra-red transmitter using the same 904~905nm wavelength as the LIDAR Gun or Camera. When the Laser jammer receiver detects a LIDAR system in operation it will start transmitting infra-red pulses to try and confuse the receiver in the LIDAR system. Each make and model of LIDAR gun or camera may have a unique pulse rate and pattern, the better laser jamming systems can determine very quickly the make and model of the LIDAR device by this pattern and then transmit back a signal which exactly matches the transmitted pulse rate and pattern expected from the LIDAR gun or camera, stopping the unit from getting a valid reading. When operating the Laser jammer will also give an audible and possibly visual alert to the driver.

The type of Laser jammer is very important to its effectiveness, depending on the make and model of jammer the transmitters can either be a Laser diode based unit (similar to or the same as the Laser diode used in the LIDAR Gun or Camera) or less expensive infra-red LED's (similar to what is used in a TV remote control). The Laser diode based systems are much higher power and are generally much more effective at stopping the LIDAR gun or camera from getting a valid speed, the higher power signal will be much more effective at swamping any reflected light coming from the LIDAR gun or camera. A good quality Laser jammer is also very important in stopping the operator of a LIDAR gun from knowing a Laser jammer is in operation, most LIDAR guns can detect if it is receiving an invalid pulse pattern and will notify the operator via a jam code. Laser jammers which shut themselves off after a set time period can also help avoid suspicion of its operation. Some Laser jammers will also include a parking sensor mode for added value.