What is the ranging principle of an optical rangefinder

This is called triangulation. Each end of the rangefinder has a "periscope," and the distance between the two objectives is called the baseline length, which is fixed. When two periscopes reach the same target, they will be at an angle to the baseline.

Given the bottom edge and two bottom corners, find the triangle.

height. If the bottom angle is fixed at 90, it is easier to calculate. Optical rangefinders (non-photoelectric rangefinders) are mainly two types based on triangulation.

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The principle is simple: there is a "periscope" at each end of the rangefinder, and the distance between the two objectives (called the baseline length) is naturally fixed. When two periscopes reach the same target, they will be at an angle to the baseline.

Given the base edge and two base corners, find the height of the triangle, which is a standard secondary geometry problem. If one of them is a right angle, it is easier to calculate. The accuracy of a rangefinder depends on a number of factors, such as the level of the optical components and the accuracy of the regulator.

But the main thing is that the theoretical accuracy also depends on the baseline length. For targets at the same distance, the longer the baseline, the smaller the measurement angle, and the smaller the error as a function of triangulation. (Please refer to the function table for information) can calculate the theoretical error.

In a nutshell, optical rangefinders (such as 1-meter optical rangefinders and meter rangefinders) are often referred to as baseline lengths. The two eyepieces of the stereo rangefinder are imaged separately, and the rangefinder uses two eyes to look at the left and right eyepieces, respectively. When the eyes of the rangefinder look up, they will see a double image.

When the adjustment cursor coincides with the target image, the exact range can be read out. The stereo rangefinder has relatively good distance accuracy, stereo vision, small parallax.

and the advantages of a powerful ability to capture moving objects at high speeds.

InWorld War IIIn the later period, stereo rangefinders became the main force. With the radar andLaser rangefinderWith the advent of the optical rangefinder, it is no longer as useful as it used to be, but unlike radar and laser rangefinders, which do not require a power source or a battery and are passive rangefinders that do not emit radio or lasers, they are not easy to find, and optical observation also has a good intuitive feeling, so it is still in use.

Principle: According to the way of measuring time t, the photoelectric rangefinder is divided into pulse ranging method for direct time measurement and phase ranging method for indirect time measurement. High-precision rangefinders, generally phased.

The ranging principle of the phased photoelectric rangefinder is: after the light emitted by the light source passes through the modulator, it becomes the modulated light whose light intensity changes with the high-frequency signal. The distance is solved by measuring the phase difference of the modulated light propagating back and forth over the distance to be measured.

The phase method is equivalent to using a "light ruler" instead of a steel ruler to measure the distance, and 2 is the length of the light ruler.

In a phase rangefinder, the phase meter can only measure the mantissa δn of the phase difference, but not the whole period n, so the distance greater than the light gauge cannot be measured. In order to extend the range, a longer light ruler should be chosen. In order to solve the contradiction between expanding the range and ensuring the accuracy, two modulation frequencies are generally used on the short-range rangefinder, that is, two kinds of light rulers.

For example: a long light ruler (called a rough ruler) f1 = 150 kHz, 1 2 = 1 000 m, which is used to expand the range and measure 100 meters, 10 meters and meters; The short light ruler (called the precision ruler) f2 = 15MHz, 2 2 = 10m, is used to ensure accuracy, and measure meters, decimeters, centimeters and millimeters.

There are three methods of distance measurement: direct measurement by steel ruler, instrument line-of-sight measurement and photoelectric measurement.

The principle of the photoelectric rangefinder: the instrument emits the light source to the proposed ranging position of the light target, measures the return time of the light, and measures the distance at the speed of light.

Photoelectric rangefinder, also known as light-speed rangefinder, is an instrument that uses modulated light waves for precise ranging, with a range of about 25 kilometers, and can also be used for night operations.

Direct measurement with a steel ruler refers to the direct measurement of distances with a steel ruler. Instrument line-of-sight measurement is a method of using the line-of-sight wire on the cross-wire reticle in the telescope of the theodolite and level to read on the line-of-sight ruler, and according to the principles of optics and geometry, the horizontal distance and height difference between the instrument and the ground point are measured at the same time. Photoelectric measurement refers to the use of optical fiber communication and optoelectronic devices to measure and transmit various physical quantities at high potential.

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Problem description: What is the principle of infrared ranging or laser ranging? Does the plane of the object to be measured have to be perpendicular to the light? Is it okay if the plane of the object to be measured is diffuse? If ultrasonic ranging is used instead, can the object move along a wall and measure the distance from the opposite wall?

Lots of questions, thank you very much!

Analysis: 1What is the principle of infrared ranging or laser ranging?

The principle of ranging can be basically boiled down to measuring the time it takes for light to travel to and from a target, and then calculating the distance d from the speed of light c = m s and the atmospheric refractive coefficient n. Due to the difficulty of measuring time directly, it is common to determine the phase of a continuous wave, which is called a phase-measuring rangefinder. Of course, there are also pulsed rangefinders, typical of the Wild DI-3000

It is important to note that phase measurement does not measure the phase of the infrared or laser, but measures the phase of the signal modulated on the infrared or laser.

There is a hand-held rangefinder in the construction industry that works on the same principle as it works for house surveying.

2.Does the plane of the object to be measured have to be perpendicular to the light?

Usually, precision ranging requires the cooperation of total reflection prism, and the rangefinder used for house measurement is directly measured by the reflection of the wall surface of the light and sun, mainly because the distance is relatively close, and the signal strength reflected back by the light is large enough. With which grip you can know, it must be vertical, otherwise the return signal is too weak and you will not be able to get the exact distance.

3.Is it okay if the plane of the object to be measured is diffuse?

Usually it is possible, but in practice, thin plastic sheets will be used as reflective surfaces to solve the problem of severe diffuse reflection.

4.If ultrasonic ranging is used instead, can the object move along a wall and measure the distance from the opposite wall?

This problem does not understand your intentions, ultrasonic ranging accuracy is relatively low, and it is rarely used now. What does it mean to stretch the wall? Hee-hee.

The working principle of the optical rangefinder is to use the phase displacement of high-frequency modulated light to go back and forth on the distance to be measured to calculate the beam degree over time t, so as to obtain the distance d according to d c t 2.

The strobe method is to use a light source that flickers at a certain frequency, compares the synchronization characteristics of the initial light and the reflected light, and calculates the distance according to the speed of light through the period of the strobe. The geometric method is to calculate the distance by the angle between the two measurement points and the punctuation point by two measurement points separated by a certain distance.

The principle of laser measurement "distance" The laser is emitted from the emitting lens of the instrument, hits the laser returned by the measured target, and is then received by the receiving lens of the instrument, so that the product of the speed of light and time in the measurement process can be calculated by dividing by 2. The formula is s=v t 2 (s distance, v velocity, t time).

There are many principles of laser ranging, and there are two main types of handheld:

1. Pulse type. Transmit a pulse, start the timer, receive the pulse, stop the timer.

2. Phase. To transmit continuous pulses and measure the phase difference between the transmitted and received pulses, at least two frequency pulse frequencies are generally required.