Abstract: A holographic resonant system includes a plurality of volume phase holograms superimposed on a single layer of photosensitive film. The volume phase holograms are oriented with respect to one another such that a first volume phase hologram selects an incoming light beam incident upon a surface of the holographic resonant system having a wavelength &lgr;playback and an angle of incidence &thgr;in and internally diffracts the incoming light beam to a second volume phase hologram. The second volume phase hologram then accepts the resulting diffracted light beam from the first volume phase hologram and diffracts the light beam to form an image reflected from the surface of the holographic resonant system at wavelength &lgr;playback and an angle &thgr;out. The result is a holographic resonant system that only permits light beams from a predetermined direction to illuminate the system, thereby reducing the effect of ambient light upon the system and thus increasing the contrast ratio of the image.

Abstract: A touch screen input device and method for use with a rear-mounted video output projection system incorporates a transparent sheet preferably having substantially parallel top and bottom surfaces as the touch screen panel. A rear-mounted light source projects light onto the rear surface of the touch screen panel, on which a diffusing surface is imposed, with the result that some of the light from the light source is totally internally reflected within the touch screen panel and is imaged by a rear-mounted video camera. When the front surface of the touch screen panel is touched by a finger or rubbery object, total internal reflection is interrupted and the video camera images the touch as a dark spot.