Many Kinds of industrial robot have been developed for labor saving or emancipation of human labor from simple and dull or dangerous works. But at present the purpose has not been achieved yet. One of the reasons is considered to be that these industrial robots have not sensing system like a human body. For example, in welding or spray painting, a welding rod or a spray gun must hold a constant distance up to the object surface wherever the object is not set at the accurate position, so the robots for such works must have some sensing system to hold a constant distance up to the object.
We have developed one of such systems that can be used for welding, painting and so on. The principle of the distance sensor of this system is as follows. The light beam of a laser is reflected by a rotating mirror and scans on the object surface. There are two photo-receivers to catch the beam. One of them is set near the rotating mirror and receives the scanning laser beam in a fixed direction. This direction is the beginning of scanning. The other one is set on the robot arm, which can move horizontally, and receives the horizontal component of dispersed light from the object surface. The time interval between the outputs of two photo-receivers is a function of vertical distance between the rotating mirror and the arm of the robot, L, and of the horizontal distance from the rotating mirror up to the object surface, X. From some computation with a mini-computer the distance X can be detected. Using this sensor, the system can hold the interval constant from an arm tip up to an object.