Optical touch screen systems using reflected light
A touch screen system, including a near-infrared transparent screen including a plurality of reflective elements embedded therein, a circuit board including circuitry for controlled selective activation of electronic components connected thereto, at least one light source connected to the circuit board, for emitting light, and at least one light detector connected to the circuit board, for detecting light emitted by the at least one light source and reflected by the reflective elements.
1. A touch screen system comprising:
a display screen;
a circuit board comprising circuitry for controlled selective activation of electronic components connected thereto;
a plurality of first photo diodes connected to said circuit board, for detecting amounts of light at a first exit side of said display screen;
a plurality of second photo diodes connected to said circuit board, for detecting amounts of light at a second exit side of said display screen, the second exit side being opposite the first exit side;
a plurality of near-infrared LEDs connected to said circuit board, for emitting light at an entrance side of said display screen, the entrance side being adjacent to the first and second exit sides,
wherein an object that touches or hovers above said display screen reflects light emitted by said near-infrared LEDs towards said first and second exit sides, the amount of light detected at each photo diode corresponding to a distance between the object and that photo diode, and wherein said circuitry determines whether the object is nearer to the first exit side or the second exit side based on comparison of amounts of light detected by said first photo diodes and by said second photo diodes, when the light emitted by said near-infrared LEDs is reflected by the object.
2. The touch screen system of claim 1 further comprising at least one optical element for guiding light emitted by said near-infrared LEDs over said display screen.
3. The touch screen system of claim 1 , further comprising a plurality of third photo diodes connected to said circuit board, for detecting amounts of light at a third exit side of said display screen, the third exit side being opposite the entrance side, wherein said circuitry calculates the position of the object based on the amounts of light detected by said first, second and third photo diodes, when the light emitted by said near-infrared LEDs is reflected by the object towards the first and second exit sides, and blocked by the object from reaching the third exit side.