Abstract: A touch panel system using modulated light beams to enable the system to detect when one or more of the light beams are blocked even in bright ambient light conditions. The system has a "touch sensitive" display surface with a defined perimeter. Surrounding the display surface are a multiplicity of light emitting elements and light receiving elements. These elements are located so that the light paths defined by selected pairs of light emitting and light receiving elements cross the display surface and define a grid of intersecting light paths. A scanning circuit sequentially enables selected pairs of the light emitting and light receiving elements, modulating the amplitude of the light emitted in accordance with a predetermined pattern. A filter generates a blocked path signal if the currently enabled light receiving element is not generating an output signal modulated in accordance with the predetermined pattern.

Abstract: A touch panel assembly includes a filter plate having a recessed outer surface, first and second "L"-shaped supports each including a plurality of light-emitting or detecting elements along edges thereof with the "L"-shaped supports positioned adjacent to the inner surface of the filter plate and about the recessed outer surface whereby light from a lamp passes through the recessed outer surface to a detector element. A display is positioned in alignment with the recessed outer surface. The assembly is compact and facilitates the sealing of the display and electronics within a housing. The "L"-shaped supports for the light sources and detectors facilitate the assembly and servicing of the light elements in the assembly.