A device and method for detecting the location of an object in a surface employs a first plurality of light sources disposed along a first row adjacent the surface. A first plurality of light detectors is disposed along a second row adjacent the surface and spaced apart from the first row. Each detector...http://www.google.de/patents/US5635724?utm_source=gb-gplus-sharePatent US5635724 - Method and apparatus for detecting the location of an object on a surface
