Development of Laser Ranging Sensors

Lasers are widely used in the detection field, with rich technical content and obvious impact on social production and life. Laser ranging is one of the applications of lasers. This is because the laser has many advantages such as strong directionality, high brightness, and good monochromaticity. In 1965, the Soviet Union used a laser to measure the distance between the earth and the moon (384,401km) with an error of only 250m. In 1969, when the Americans landed on the moon, they placed a reflector on the lunar surface, and also used a laser to measure the distance between the earth and the moon, with an error of only 15cm.

The basic principle of using laser transit time to measure distance is to determine the target distance by measuring the time it takes for the laser to travel to and from the target. which is:.

Although laser ranging is simple in principle and simple in structure, it was mainly used in military and scientific research in the past, but it is rare in industrial automation. Because the price of laser ranging sensors is too high, generally in the thousands of dollars. Virtually all industrial users are looking for a sensor that enables precise distance detection at longer distances. Because in many cases sensors installed in close proximity are limited by physical location and production environment, today's laser ranging sensors will help engineers in these situations.

Working principle of laser distance sensor:

When working, the laser diode is first aimed at the target to emit laser pulses. After being reflected by the target, the laser light is scattered in all directions. Part of the scattered light returns to the sensor receiver, where it is picked up by the optical system and imaged onto the avalanche photodiode. The avalanche photodiode is an optical sensor with an internal amplification function, so it can detect very weak light signals. The distance to the target can be determined by recording and processing the time elapsed from when the light pulse is sent to when it is received back. Laser sensors need to accurately measure transit times because the speed of light is so fast.

For example, the speed of light is about 3X10^8m/s. To achieve a resolution of 1mm, the electronic circuit of the ranging sensor needs to be able to distinguish the following extremely short time: 0.001m(3X10^8m/s)=3ps

To distinguish the time of 3ps, this is a high requirement for electronic technology, and the cost is too high to realize. But today's cheap laser sensors neatly circumvent this obstacle, using a simple statistical principle, the averaging rule, to achieve a resolution of 1mm with guaranteed responsiveness.

* Solve problems that other technologies cannot solve:

Laser distance sensors can be used where other technologies cannot. For example, when the target is very close, ordinary photosensors that calculate the reflected light from the target can also perform a large number of precise position detection tasks. However, when the target is far away or the color of the target changes, it is difficult for ordinary photoelectric sensors to deal with it.