Patent ID: 8902196

Claim:
A method of determining a touch coordinate on a touch screen, comprising: providing (i) a display, (ii) a plurality of collimating lenses along two opposite edges of the display, (iii) a plurality of light pulse emitters, denoted E, that transmit light pulses through the collimating lenses of a first of the two edges and over the display, and (iv) a plurality of light pulse receivers, denoted R, that receive the light pulses through the collimating lenses of the opposite of the two edges, and that output values, denoted OUT(E, R), representing the light pulses received by receiver R from emitter E, wherein each emitter-receiver pair (E, R) has an expected receiver output value, denoted EXP(E, R), when light pulses are not blocked, and wherein the collimating lenses are arranged in a shift-aligned fashion such that (a) light pulses emitted by each emitter are detected by at least two of the receivers, and (b) each receiver detects light pulses emitted by at least two emitters; selecting two or more emitter-receiver pairs (E 1 , R 1 ), . . . , (E n , R n ) for which their actual receiver output values, OUT(E 1 , R 1 ), . . . , OUT(E n , R n ), deviate significantly from their expected receiver output values EXP(E 1 , R 1 ), . . . , EXP(E n , R n ), because either (A) light pulses transmitted by each of two emitters are being blocked from reaching a common receiver, or (B) light pulses transmitted by a common emitter are being blocked from reaching each of two receivers; associating respective screen coordinates, denoted X(E 1 , R 1 ), . . . , X(E n , R n ), along a first screen axis with the selected emitter-receiver pairs; and calculating a touch coordinate, denoted XT, by interpolating the associated screen coordinates XT=ΣW i *X ( E i , R i ) with weights W i according to the respective deviations, OUT(E i , R i )−EXP (E i , R i ), between the actual receiver output values and the expected receiver output values.