Introduction to the types and functions of rangefinders
Photoelectric distance meter
According to the distance measurement method, photoelectric distance measuring instruments are further divided into two types: phase method distance measuring instruments and pulse distance measuring instruments.
Pulse rangefinders use a beam of light emitted from a target object to determine the time it takes for the light to reflect back, thereby calculating the distance between the instrument and the target object. Due to the good directionality and single wavelength of the laser, it is commonly used as a modulation object in optoelectronic rangefinders. Therefore, pulse rangefinders are commonly known as laser rangefinders.
Laser rangefinders using pulse method can achieve a wide range and can be used for indoor and outdoor measurements. Their typical range is 3.5 to 2000 meters, while high range laser rangefinders can reach 5000 meters. Laser rangefinders for military purposes can reach even longer ranges. Due to the ability to measure long-range measurement targets, laser rangefinders generally have a telescopic system, also known as a laser rangefinder telescope, in order to visually observe the ranging target by users. Figure 1 is a typical image of a three cylinder laser rangefinder telescope.
The accuracy of laser rangefinders mainly depends on the accuracy of the instrument in calculating the time between laser emission and reception. According to the technology and application used, laser rangefinders can be divided into conventional laser rangefinders with an accuracy of about 1 meter (mainly used for outdoor sports, hunting, etc.) and high-precision laser rangefinders used in surveying, land measurement, construction, engineering applications, military, and other occasions with high accuracy requirements.
Phase method rangefinder is a rangefinder that modulates the phase of the laser and obtains distance by measuring the phase difference of the reflected laser. Due to the need to detect the phase of the reflected laser, it is necessary to receive a signal with strong intensity. Considering the safety of the human eye, a telescopic system similar to a pulse laser rangefinder cannot be used, and the range is small. The typical range of the rangefinder is 0.5mm to 150 meters. Generally, a phase laser rangefinder uses a 635 nanometer (visually red) laser as the debugging object, also known as an infrared rangefinder, But in fact, the definition of laser is not based on color, and using a 635 nanometer laser rangefinder can cause irreversible damage to the human eye if directly irradiated. Readers are advised to use and protect it correctly.
