From the basic principle of ranging, rangefinders can be divided into the following three categories:
1. Laser rangefinder Laser rangefinder is an instrument that uses laser to accurately measure the distance of the target.
When a laser rangefinder works, it fires a very thick laser beam at the target, and the optoelectronic element receives the laser beam reflected by the target. The timer measures the time from emission to reception of the laser beam and calculates the distance from the observer to the target.
Laser
rangefinders are the most commonly used rangefinders. Laser rangefinders can be divided into handheld laser rangefinders (measurement distance of 0-300 meters) and telescope laser rangefinders (measurement distance of 500-20000 meters).
2. Ultrasonic rangefinder Ultrasonic rangefinder is based on the characteristics of ultrasonic reflection when encountering obstacles.
The ultrasonic transmitter emits ultrasonic waves in a certain direction and starts timing at the same time.
As ultrasonic waves travel through the air, they return immediately when they encounter obstacles on their way. When the ultrasonic receiver receives the reflected wave, it immediately interrupts and stops timing.
By continuously detecting the echoes reflected by obstacles after transmitting the generated waves, the time difference t between the transmitted ultrasonic waves and the received echoes is measured, and then the distance L is calculated. Ultrasonic rangefinder, because the ultrasonic wave is little affected by the surrounding environment, usually the measurement distance is relatively long and the measurement accuracy is relatively high. At present, the scope of use is not very large, but the price is relatively high, usually around a few hundred yuan.
3. The infrared rangefinder is an instrument that uses modulated white light for accurate distance measurement, and the measurement range is usually 1-5 kilometers.
It uses the principle of non-diffusion of infrared propagation: because the refractive index of infrared rays is large when passing through other substances, infrared rays are considered in remote measuring instruments. When infrared rays are emitted from the rangefinder and meet the reflector, the propagation of infrared rays takes time, It is received by a rangefinder, which can then calculate the distance based on the time it takes for the infrared to travel from when it is sent to when it is received and how fast the infrared travels.
The advantages of infrared ranging are cheap, easy to control, and safe, but the disadvantages are high accuracy, long distance, and less directivity. Infrared rangefinder and ultrasonic rangefinder technology is relatively advanced. Now generally speaking, infrared rangefinders refer to laser
rangefinders.
