Patent ID: 8587562

Claim:
A touch screen comprising: a housing; a display mounted in said housing; a plurality of light pulse emitters mounted in said housing below said display; a plurality of light pulse receivers mounted in said housing below said display; a first light guide, mounted in said housing along a first edge of said display, comprising: a first substantially parabolic reflective surface for reflecting light pulses transmitted by said emitters; and a first substantially elliptical refractive surface, positioned substantially above said first substantially parabolic reflective surface, for refracting the reflected light pulses over said display; a second light guide, mounted in said housing along an opposite edge of said display, comprising: a second substantially elliptical refractive surface for further refracting the light pulses refracted by the first substantially elliptical refractive surface; and a second substantially parabolic reflective surface, positioned substantially below said second substantially elliptical refractive surface, for reflecting the further refracted light pulses to said receivers; and a calculating unit, mounted in said housing and connected to said receivers, to determine a location of a pointer on said display that partially blocks the light pulses refracted by said first light guide, based on outputs of said receivers corresponding to light pulses refracted by said second light guide.