Analysis of the principle of temperature and humidity monitoring and distance measuring instrument
Laser rangefinders generally use two methods to measure distance: pulse method and phase method. The process of pulse ranging is as follows: the laser emitted by the rangefinder is reflected by the object being measured and then received by the rangefinder, which simultaneously records the round-trip time of the laser. Half of the product of the speed of light and round-trip time is the distance between the rangefinder and the object being measured. The accuracy of measuring distance using pulse method is generally around+/-1 meter. In addition, the measurement blind spot of such rangefinders is generally around 15 meters.
Laser ranging is a distance measurement method in light wave ranging. If the time required for light to travel back and forth between points A and B at a speed of c in the air is t, then the distance D between points A and B can be expressed as follows.
D=ct/2
In the formula:
D - Distance between measurement stations A and B;
C - the speed at which light propagates in the atmosphere;
T - The time required for light to travel back and forth between A and B.
From the above equation, it can be seen that to measure the distance between A and B, it is actually necessary to measure the time t of light propagation. Depending on the different methods of measuring time, laser rangefinders can usually be divided into two measurement forms: pulse type and phase type.
Phase laser rangefinder
Phase laser rangefinder is a device that modulates the amplitude of a laser beam using radio frequency bands and measures the phase delay generated by the modulated light traveling back and forth to the measurement line once. Based on the wavelength of the modulated light, the distance represented by this phase delay is converted. Measure the time required for light to travel back and forth through the measuring line using indirect methods, as shown in the figure.
Phase laser rangefinders are generally used in precision ranging. Due to its high accuracy, usually in the millimeter range, in order to effectively reflect signals and limit the measured target to a specific point commensurate with the instrument accuracy, this rangefinder is equipped with a mirror called a cooperative target.
