Virtual touch screen “VIRTOS” implementing virtual touch buttons and virtual sliders using a projector and camera

We propose a large interactive display with virtual touch buttons and sliders on a pale-colored flat wall. Our easy-to-install system consists of a front projector and a single commodity camera. A button touch is detected based on the area of the shadow cast by the user´s hand; this shadow becomes very small when the button is touched. The shadow area is segmented by a brief change of the button to a different color when a large foreground (i.e., the hand and its shadow) covers the button region. Therefore, no time consuming operations, such as morphing or shape analysis, are required. Background subtraction is used to extract the foreground region. The reference image for the background is continuously adjusted to match the ambient light. Our virtual slider is based on this touch-button mechanism. When tested, our scheme proved robust to differences in illumination. The response time for touch detection was about 150 ms. Our virtual slider has a quick response and proved suitable as a controller for a Breakout-style game.