How does Microsoft Surface work? A projector underneath the surface projects an image onto its underside, while cameras in the machine's housing record reflections of infrared light from human fingertips. The cameras can also recognise objects placed on the surface if those objects have specially-designed. Fingers are visible through the diffuser by series of infrared–sensitive cameras, positioned underneath the surface of the tabletop. An image processing system processes the camera images to detect fingers and custom tags.