Introduction of Types and Functions of Range Finder
Photoelectric distance meter
According to the ranging method, photoelectric rangefinder can be divided into phase rangefinder and pulse rangefinder.
Pulse rangefinder uses a beam of light to the target object to measure the time when the target object reflects the light back, so as to calculate the distance between the instrument and the target object. Because laser has good directivity and single wavelength, photoelectric rangefinder generally uses laser as the modulation object, so pulse rangefinder is also commonly known as laser rangefinder.
The laser rangefinder using pulse method can reach a wide ranging range, which can be used for indoor and outdoor measurement. Its typical ranging range is 3.5 meters to 2000 meters, and the laser rangefinder with high range can reach 5000 meters. The laser rangefinder for military use can reach a longer range. Because it has the ability to measure long-distance measurement targets, in order to visually observe the ranging targets by users, laser rangefinders generally have a telescopic system, which is also called laser rangefinder telescope. Figure 1 is a typical diagram of a three-tube laser rangefinder telescope.
The accuracy of laser rangefinder mainly depends on the accuracy of calculating the time between laser sending and receiving. According to the technology and application, laser rangefinder can be divided into conventional laser rangefinder with accuracy of about 1 meter (mainly used in outdoor sports, hunting, etc.) and high-precision laser rangefinder used in surveying and mapping, land measurement, architecture, engineering application, military and other occasions with high accuracy requirements.
Phase rangefinder is a rangefinder that modulates the phase of laser light and obtains the distance by measuring the phase difference of reflected laser light. Because the reflected laser phase needs to be detected, the received signal needs to have strong intensity. Considering the safety of human eyes, the telescopic system like pulse laser rangefinder cannot be adopted, and the range is small. The typical range of ranging is 0.5mm to 150 meters. The general phase laser rangefinder uses 635 nm (red in vision) laser as the debugging object, also known as infrared rangefinder. But in fact, the definition of laser is not defined by color, and if the 635 nm laser rangefinder is used to directly illuminate the human eye, it will cause irreversible damage. Please use it correctly and protect it.
Acoustic distance meter
Acoustic ranging is an instrument that uses the reflection characteristics of acoustic waves to measure. Generally, ultrasonic wave is used as the modulation object, that is, ultrasonic range finder. The ultrasonic transmitter emits ultrasonic waves in a certain direction, and starts timing at the same time. The ultrasonic waves propagate in the air and return immediately when they encounter obstacles on the way. The ultrasonic receiver immediately stops timing when it receives reflected waves. By continuously detecting the echo reflected by obstacles after the generated wave is emitted, the time difference T between transmitting the ultrasonic wave and receiving the echo is measured, and then the distance L is calculated.
Because the speed of ultrasonic wave propagation in the air is greatly influenced by temperature, humidity, air pressure, etc., the measurement error is large, and because of the long wavelength of ultrasonic wave, the propagation distance is short, so the measurement distance of general ultrasonic range finder is short and the measurement accuracy is low. However, due to the fan-shaped propagation of ultrasonic wave, its detection range is larger than that of photoelectric rangefinder, and it is widely used in safety protection, cable height measurement, obstacle detection and other fields in practical engineering.
