Multi-touch detection by an optical touch screen

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 B1(E), . . . , Bn(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 Bi(E, R), of beams Bi(E), for one or more emitters E, when beams Bi(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 Bi(E, R) at least partially blocked by each object, as determined by outputs of said light receivers.

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 B1(E), . . . , Bn(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 Bi(E, R), of beams Bi(E), for one or more emitters E, when beams Bi(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 Bi(E, R) at least partially blocked by each object, as determined by outputs of said light receivers.