The operating principle of the interactive projection system is first to capture the target image (such as the participant) through the capture device (sensor)，It is then analyzed by the image analysis system，The light projected by the projector is the visible part，The infrared part of it is filtered out by the membrane inside it，So for the camera it can't see what the projector is projecting，If the infrared is strong，The camera can see the body。How do you enhance the image of the object the camera sees，Fortunately, such infrared active emission technology is already well established on the market，For example, the kind of night vision cameras sold in the surveillance market can emit near infrared (850 nm)., More powerful have a special remote infrared light，However, the night vision camera can reach a distance of 5 meters，So no need。The night vision camera actively emits infrared, and then the ccd sensor accepts infrared, then the most difficult part of the interactive projection, the division of the human body and the background virtual object is solved, and the camera gets a black-and-white monochrome background image including people。 The next step is to detect the movement of the human body, using the image difference technology, the difference is to subtract the two consecutive frames of the image obtained by the camera, then what is obtained, the moving part, so that as long as the person is moving, the difference will intercept the moving part。The next step is to analyze the data, and then project the virtual part。Of course, complex interactive projection is not only these technologies, these are just the most basic principles, which also involves the camera calibration, optical flow method to find the direction of motion, performance optimization processing, special effects。