Radar Detectors and Lidar Laser Gun
Police have been using the conventional radar guns since the 1950s. A large number of police departments have started making use of laser speed guns, rather than the conventional radar devices. Concentrated light is the basic element in a laser speed-measuring device, also known as a lidar gun, for light detection and ranging.
The lidar gun measures the time taken by a burst of infrared light to get to a vehicle, to get reflected and return back to the starting point. The lidar system determines the distance from the object, by multiplying the speed of light by this time. Lidar does not take into account the change in wave frequency, unlike traditional police radar. Instead, it collects multiple distances by sending out numerous infrared laser bursts within a short period of time. The system can calculate the speed of the car, by comparing these different distance samples. These guns are extremely accurate as it is possible to take several hundred samples in less than half a second, while using these.
Similar to conventional radar guns, police may use handheld lidar systems. However, in many areas, the lidar system is completely automated. The gun registers the speed of any car that passes by, by pointing the laser beam at an angle across the road. The angle of view is accounted for by the system, by making a mathematical adjustment.
The system activates a small camera when a speeding car is detected. It takes a photograph of the car's license plate and the driver's face. The central office simply issues a ticket for a speeding fine and sends it in the mail to the concerned driver, since the automated system has collected all of the evidence required by the police.
Detector devices can and do help speedsters avoid radar and lidar speed traps. However, the police can also, at times, figure out who is using a radar detector.
Detecting Signals
Conventional radar is relatively easier to detect. A small electronic device used by some drivers to forewarn them of the presence of police radar units is called a radar detector. The simplest radar detector is somewhat like the one used for receiving broadcasts from FM and AM radio stations, and is just a basic radio receiver.
What is actually detected by a radar detector depends on the make and model of the radar gun used by law enforcement. A radio signal is a sent at a specific frequency by a very basic radar gun.
As there are numerous uses for radio signals ranging from television broadcasts to garage door openers, the air is full of these. So a receiver must pick up only signals in a certain range for it to be useful at all. The receiver in a radar detector is tuned to the frequency range used by police radar guns, just as the receiver in a radio is built to catch signals in the AM and FM frequency spectrum. In an ideal situation, the radar detector picks up the radar gun's signal before the driver goes past the police officer using it. Periodically, however, the police expand the frequency range used in radar and lidar speed guns and hence speedsters everywhere have to invest in new detection equipment.
Tolerated is the best way to describe the use of a radar detector, if not strictly legal in certain jurisdictions. The radar detector is generally attached to the visor or another inconspicuous area.
A basic radar detector is not likely to be very useful if a police officer were to drive up behind a fast moving vehicle and turn on the radar gun. The officer will already have all the information required, by the time the detector will alert the driver. In many cases, however, when the police have left their radar guns turned on for a long period of time, instead of activating these after sneaking up behind a car, the detectors do pick up the signal before the speeding car is tracked.
The electromagnetic wave produced by a radar gun rapidly spreads over a broad area, even as its cone- or dish-shaped focuses the radio signal. The radar gun is not configured to monitor everything in the vicinity; it only monitors the speed of a particular target. So, a radar detector is likely to pick up the radio signal much earlier than the radar gun identifies the car.
However, if the police officer targets a car before any other, it will be trapped. Modern detectors provide much more extensive protection for speedsters.
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