ir infrared is Important role in the touch screen  

The 808nm200mw far ir infrared light covered the full touch screen, the laser red outside thickness probably about 2mm, fingers or other objects close to the touch screen,ir infrared form infrared plane are reflected, forming a bright spot, the tip of the finger will be infrared point is displayed. The infrared camera to capture these bright spots, and pass a pictures of screen to the computer, computer processing and analysis of these images, identify the touch event and the position, and then call the corresponding instruction, provide feedback, and produce a new image, and then the new image onto the projection soft screen through the projector projection.