Light speed measurement has the following characteristics. Because the laser beam is basically a ray, the estimated speed distance is related to the useful distance of radar speed measurement. It can measure 1000M outside speed measurement with high accuracy, and the fault is less than 1 km. In view of the principle of laser speed measurement, the laser beam must be aimed. The reflection point perpendicular to the plane of the laser beam, and because the vehicle under test is too far away and in a moving situation, perhaps the plane of the vehicle body is not large, which causes the police officers on duty to work hard and get tired easily. Now the American Laser Technology Company has produced a laser speedometer with continuous automatic speed measurement function, which is specially used to deal with this problem. The Dongcheng Brigade of the Traffic Police Detachment of Dongguan City 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 may not be used in sports, but can only be used in intermittent situations. ; Therefore, the general traffic police put the instrument on the inspection vehicle, and the laser speedometer selected by most countries now uses a type of safety laser, which is safe for human eyes.
There is a close connection between laser speedometer and laser rangefinder. The principle is to first measure the distance by laser. Laser ranging (ie, 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 distance measurement with a specific time distance on the measured object, and obtains the distance change difference of the measured object within the period of time, and then obtains the moving speed of the measured object and the power consumption of the laser speedometer The quantity is relatively low, and two AA batteries can be used continuously for 20 hours. There are many types of optical rangefinders, and their functions are very different, but from the operating method (perhaps the operating principle), there are only two types, namely: pulsed laser ranging and continuous wave laser ranging. The principle and characteristics of the two rangefinders are explained below. The principle of pulsed laser ranging is to use a pulsed laser to send a very narrow light pulse (pulse width less than 50ns) to the policy, and part of the light is reflected after reaching the surface of the policy. , By measuring the time from the light pulse to the receiver, the distance between the rangefinder and the policy can be calculated.
Suppose that the measured distance is h, the light pulse reciprocating time 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 talent is strong, even for the non-cooperative policy, the maximum ranging is also It can reach more than 30000m. Its ranging accuracy is generally 5 meters, and the highest can reach 0.15m. Pulsed laser rangefinders can be used in the military to measure the range of various non-cooperative policies, and can also be used to determine the visibility and cloud height in the climate. It is also used in the field of precision distance measurement of artificial satellites.