New laser rangefinder two ways to measure distance: pulse method and phase method principle
A rangefinder is a tool for measuring length or distance, and can also be combined with goniometric devices or modules to measure out angles, areas, and other parameters. Rangefinders come in many forms, usually a long cylinder consisting of an objective lens, an eyepiece, a display unit (which can be built in), a battery, and other components.
Laser rangefinders can also emit multiple laser pulses to determine whether an object is moving away from or approaching a light source through the Doppler effect.
Rangefinder Principles
Laser rangefinders generally use two methods to measure distance: the pulse method and the phase method. The process of pulse method distance measurement is like this: the laser light emitted by the rangefinder is reflected by the measured object and then received by the rangefinder, which records the round trip time of the laser light at the same time. Half of the product of the speed of light and the round-trip time is the distance between the rangefinder and the object being measured. The accuracy of the pulse method of distance measurement is generally about +/-1 meter. In addition, the measurement blind spot of this type of rangefinder is generally about 15 meters.
Laser rangefinding is a distance measurement method in the light wave rangefinding, if the light propagates in the air with a speed c in the A, B two points between the round trip once the time required for t, then the distance D between A, B two points can be expressed as follows.
D=ct/2
Where.
D - distance between points A and B at the measurement site;
c - the speed of light traveling through the atmosphere;
t - the time required for the light to travel to and from A and B once.
As can be seen from the above formula, to measure A, B distance is actually to measure the light propagation time t. According to the different methods of measuring time, laser rangefinders can usually be divided into two forms of measurement of pulse-type and phase-type.
Phase-type laser rangefinder
Phase-type laser rangefinder is a radio frequency, the laser beam amplitude modulation and determination of modulated light to and from the measurement line once the phase delay, and then according to the wavelength of the modulated light, the conversion of the phase delay represented by the distance. That is, the indirect method of determining the time required by the light by round-trip line measurement, as shown in the figure.
Phase-type laser rangefinder is generally used in precision ranging. Because of its high accuracy, generally millimeter-scale, in order to effectively reflect the signal, and make the determination of the target is limited to a specific point commensurate with the accuracy of the instrument, such rangefinders are configured with a reflector known as the cooperative target.
