The principle of laser rangefinder is understood. The distance can be calculated by calculating the time taken to receive the reflected laser, but what we don't understand is how to send it back? When a flashlight is used to irradiate a plane mirror three or four meters away, it will reflect back light, but when it is used to irradiate ordinary objects such as tables and stools (especially in the bright outdoor environment), it will not be seen that the light emitted by a flashlight will reflect back. Even the common laser lamp similar to a flashlight can not see the reflected light when it is three or four meters away in this environment, Is the reflection ability of the lunar surface so strong? How does the object reflect back the emitted beam or something else

The principle of laser rangefinder is understood. The distance can be calculated by calculating the time taken to receive the reflected laser, but what we don't understand is how to send it back? When a flashlight is used to irradiate a plane mirror three or four meters away, it will reflect back light, but when it is used to irradiate ordinary objects such as tables and stools (especially in the bright outdoor environment), it will not be seen that the light emitted by a flashlight will reflect back. Even the common laser lamp similar to a flashlight can not see the reflected light when it is three or four meters away in this environment, Is the reflection ability of the lunar surface so strong? How does the object reflect back the emitted beam or something else

You have misunderstood the concept of "reflection". Everyday reflection can be divided into specular reflection and diffuse reflection. Specular reflection is the situation you describe, while diffuse reflection is just the spot that you see laser or flashlight shining on the target. Laser or flashlight shining on the target, reflecting in any direction around, A few of them will enter your pupil and make you see the spot. The laser rangefinder measures the time interval between the laser and the spot
Relatively speaking, it is difficult to measure the distance of a specular object (such as glass or polished metal) because it will emit the incident light strictly according to the normal law. If the incident light is not perpendicular to its reflecting surface, there will be very little light coming back to the light emitting point, Experience the difference between specular reflection and diffuse reflection
Finally, we will explain that the laser method for measuring the distance to the moon is usually the retro reflector method, that is, the mirror composed of numerous triangular cones placed on the lunar surface by Apollo 11, which can reflect the light back in strict accordance with the direction of the light, which can greatly improve the brightness of the reflected light, Even if you don't rely on this mirror, you can shine directly on the moon