Light-pen coordinate measuring system based on pan-tilt unit

Light-pen coordinate measuring systems are widely used due to their portability. In the traditional optical pen-based measurement system, the measurement range of the system is limited by the size of the field of view of the camera. In order to make up for this defect, this paper designs a new type of optical pen-type measurement system to realize the measurement. The system mounts the camera on pan-tilt unit, and tracks the moving light pen by rotating the unit to drive the camera movement. Aiming at the problem that it is difficult to control the camera when it is continuously tracking in the unit, the motion target tracking control method of the system is studied. Firstly, the background difference method and the inter-frame difference method are integrated to detect the moving target area, then the target object in the area of interest is tracked frame by frame and its moving position and direction are quickly determined, and finally the unit is controlled to turn to a preset angle to track the moving target. The experimental results show that this method is accurate in target localization, simple in control process, and can improve the real-time and reliability of the system target tracking.