# Explanation of the principle of laser rangefinder and the misunderstanding of purchasing

2021.12.13

Laser rangefinders, do you understand? The classification of laser rangefinders, laser rangefinders are divided into three categories, one is a handheld laser rangefinder, which has a short measurement distance, generally 20-250m, and high measurement accuracy. Generally, it is 1-2mm, which is widely used. Long-distance laser rangefinder, measuring distance is long, generally 500-2000 meters, the accuracy is relatively low, generally 0.5-1 meters, mainly used for electric power, environmental protection, forest, animal and plant protection, field surveys and other field long-distance measurements . The laser ranging sensor has high accuracy and can be integrated with other equipment, mainly used for industrial and online monitoring.

Its principle: the principle of triangulation, the laser beam emitted by a semiconductor laser illuminates the target. The receiver collects the light reflected by the target and focuses it on the photosensitive element. When the distance from the target changes, the angle of the reflected light passing through the receiver lens changes, and the position of the light focused on the photosensitive element is also different.

The principle of time measurement is to measure the distance within the time that the luminous laser illuminates an object and returns. It will not affect the surface condition of the workpiece, and stable detection can be carried out. Check the time t of receiving the reflected laser light in the picture on the right, and calculate the distance Y. Calculation formula: 2Y (round trip distance) = C (speed of light) T (time to receive the reflected light).

The principle of confocal measurement is that there is a lens inside the measurement part. The lens has a fixed focal length, and the focal length of the lens is set to f. When the lens is used for focusing, when the height is f, the focus will overlap and the light will converge to 1 point. When the height deviates from f, the light gradually becomes blurred. The focal position is a position where the amount of reflected light passing through the pinhole is strong. Determine the height of the tuning fork (lens) when the amount of reflected light is strong, and you can see at a glance whether the target object is located at the focal length f away from it. The internal sensor reads the position of the tuning fork (lens) with high precision at this time, and the distance to the target can be measured. Because it measures the focus height, it can achieve accurate measurement without being affected by the target's material, color, and inclination.

Factors that need to be considered when choosing a laser rangefinder: measurement accuracy (how much error); place of use (indoor or outdoor, for forestry, surveying or fishery, etc.); range of the measured distance (regardless of the measured distance is a few meters or a few 100 meters, a few kilometers).

Three misunderstandings in choosing a laser rangefinder: blindly consider the price; there is an old Chinese saying that "a penny for the goods" may not be entirely correct, but it still makes sense. In recent years, Chinese manufacturers of rangefinders have sprung up like bamboo shoots after a rain, and many brands have emerged. The quality of rangefinders varies from good to bad, and the country has not issued relevant national standards. Therefore, the market is very chaotic, so we should not only consider price when choosing products. There must be a reason for the low price, depending on whether the product has a certificate, whether the product design is reasonable, and whether it is anti-drop; the laser grade of the product, some products cannot let children look directly into the eyes, which may hurt the eyes.

Blindly pursuing high prices, the price of laser rangefinders is very confusing in the market. Many users may think that high-priced products are good when buying, and blindly pursue high prices. In fact, it is necessary to consider the ranging range, ranging accuracy, measurement distance, function, laser, etc., but the price is not the key. If you are a user, take a look at the product functions of the laser rangefinder first, and then choose a laser rangefinder suitable for engineering use after actual experience.

Blindly pursuing high indicators, any product has its own technical indicators, which of course represents a relatively high performance. In recent years, the accuracy and range of rangefinders have continued to improve. Many surveying and mapping professionals feel that their work must maintain extremely high accuracy, so they desperately pursue high accuracy and high measurement range when purchasing.

At the time of purchase, the user should choose a rangefinder according to actual needs. For example, ordinary individual users can choose a rangefinder with good performance and cheaper price to see how far the range is and whether high accuracy is required. Secondly, see if the ranging range is suitable for your own use. Those with a distance of more than a few kilometers are used by some professional surveying and mapping industries. There is absolutely no need for ordinary users to blindly pursue high positions and cause waste.