Light speed measurement has the following characteristics because the laser beam is basically a ray, and the estimated speed distance is far related to the useful distance of radar speed measurement. It can measure 1000M and the speed measurement accuracy is high, and the error is less than 1 km. In view of the principle of laser speed measurement, the laser beam must be aimed at The plane reflection point between the vertical and the laser beam, and because the measured vehicle is too far away and is in a moving situation, the plane of the vehicle body may not be large, which causes the police officers on duty to work intensively and get tired easily. Now the American Laser Technology Company has produced a laser velocimeter with continuous automatic speed measurement function, which is specially designed to deal with this problem. Dongcheng Brigade of Dongguan Traffic Police Detachment has used this improved speedometer to capture speeding vehicles, and has achieved remarkable results. In view of the principle of laser speed measurement, laser speedometers cannot be used in motion, but only in intermittent situations. Therefore, the general traffic police put the instrument on the patrol car, and the parking interruption uses a type of safety laser, which is currently used in most countries. The laser speedometer is safe for human eyes.

The laser velocimeter is closely linked with the laser rangefinder. The principle is mainly through laser ranging. Laser ranging (that is, electromagnetic waves, with a speed of 300,000 km/s), is to determine the distance between the measured object and the inspection point by emitting a laser beam to the measured object, receiving the reflected wave of the laser beam, and recording the time difference. . Then the laser speed measurement performs two laser ranging on the measured object with a specific time distance, obtains the difference of the distance change of the measured object in this period of time, and then obtains the moving speed of the measured object and the power consumption of the laser velocimeter. The amount is relatively low, two AA batteries can be used continuously for 20 hours. There are many types of optical rangefinders with different functions, but there are only two types of operation methods (or operating principles), namely: pulsed laser ranging and continuous wave laser ranging. The principle of pulsed laser ranging is to explain the principle of pulsed laser ranging. The principle of pulsed laser ranging is to use a pulsed laser to emit a series of very narrow light pulses (pulse width less than 50ns) to the policy, and the light is partially reflected after reaching the surface of the policy. , by measuring the time from the launch of the light pulse to the return to the receiver, the distance between the rangefinder and the policy can be calculated.

Assuming that the measured distance is h, the reciprocating time of the optical pulse is t, and the propagation speed of light in the air is c. The pulse laser ranging function declares a very strong laser. The ranging ability is strong, even for non-cooperative policies, the maximum ranging It can also reach more than 30000m. The ranging accuracy is generally 5 meters, and the Z height can reach 0.15m. Pulsed laser rangefinders can be used in military distance measurement for various non-cooperative policies, and also in climate measurement of visibility and cloud height. It is also used in the fields of precise distance measurement of artificial satellites.