Multi-touch detection by an optical touch screen

Abstract

A light-based touch-sensitive surface, including a housing, a surface attached to the housing for receiving touch input, a plurality of light sources in the housing for emitting light that crosses the surface, a plurality of light receivers in the housing for detecting the light emitted by the light sources, a curved lens adjacent to the surface through which the light emitted by the light sources passes, including two substantially similarly curved exterior panels, one of which forms a curved rim for the surface, and a calculating unit in said housing, connected to the light receivers, for calculating a touch location based on an absence of light expected to be received by the receivers.

1 - 14 . (canceled) 
     
     
         15 . An optical touch screen, comprising:
 a display area;   a plurality of light emitters and corresponding lenses, mounted along edges of said display area, emitting light over said display area, such that each emitter, denoted E, emits light that is refracted through its lens to a number, n, of light beams, denoted B 1 (E), . . . , B n (E), in different directions, where n is greater than one;   a plurality of light receivers, mounted along edges of said display area, receiving emitted light and outputting indications of amounts of light received, such that each receiver, denoted R, receives one or more portions, denoted B i (E, R), of beams B i (E), for one or more emitters E, when beams B i (E) travel over said display area to receiver R without being blocked; and
 a calculating unit coupled with said receivers, determining respective coordinates of multiple objects touching said display area based on light beam portions B i (E, R) at least partially blocked by each object, as determined by outputs of said light receivers. 
   
     
     
         16 . The optical touch screen of  claim 15 , wherein each emitter is situated along an edge of said display area directly across from a corresponding emitter along the opposite edge. 
     
     
         17 . The optical touch screen of  claim 15 , wherein said display area is rectangular, and wherein said light emitters and light receivers are arranged in an alternating equi-spaced fashion along edges of said display area such that the equi-spacing between neighboring light emitters and light receivers is the same size along both short and long edges of said display area. 
     
     
         18 . The optical touch screen of  claim 15 , wherein said display area is rectangular, and wherein said light emitters and light receivers are arranged in an alternating equi-spaced fashion along edges of said display area such that the equi-spacing between neighboring light emitters and light receivers along the longer edges of said display area is greater than the equi-spacing between neighboring light emitters and light receivers along the shorter edges of said display area. 
     
     
         19 . The optical touch screen of  claim 15 , wherein said calculating unit distinguishes between real and ghost touches, based on outputs of said light receivers. 
     
     
         20 . A method of identifying coordinates of multiple objects touching a display screen, comprising:
 causing light emitters to emit light over a display area, such that light emitted by each emitter, denoted E, is refracted through a corresponding lens to a number, n, of light beams, denoted B 1 (E), . . . , B n (E), in different directions, where n is greater than one;   measuring amounts of emitted light received by a plurality of light receivers, wherein each receiver, denoted R, is arranged so as to receive one or more portions, denoted B i (E, R), of beams B i (E), for one or more emitters E, when beams B i (E) travel over the display area to receiver R without being blocked; and   determining respective coordinates of multiple objects touching said display area, based on light beam portions B i (E, R) at least partially blocked by each object, as determined by outputs of said light receivers.   
     
     
         21 . The method of  claim 20 , wherein said determining comprises:
 assigning, for each object, denoted Obj, respective coordinates, denoted X(Obj, B i (E, R)), to each light beam portion B i (E, R) at least partially blocked by Obj; and   calculating a weighted average of the coordinates X(Obj, B i (E, R)).   
     
     
         22 . The method of  claim 21 , wherein the weight of X(Obj, B i (E, R)) in the average corresponds to the portion of light beam B i (E, R) blocked by Obj from arriving at receiver R, as determined from outputs of receiver R.