Optical proximity sensor for touch screen and associated calibration tool

A method for calibrating parameters of a proximity sensor strip featuring a plurality of emitters E and detectors D, wherein the emitters and detectors are arranged such that the emitters project light out of the strip along a detection plane and the detectors detect light entering the strip along the detection plane, and for each emitter-detector pair (E, D), when the object is located at a target position p(E, D) in the detection plane, corresponding to the pair (E, D), then the light emitted by emitter E is scattered by the object and is expected to be maximally detected by detector D, the method comprising:

• providing a reflective object spanning the length of the proximity sensor parallel to the proximity sensor strip in the detection plane;
• incrementally moving the reflective object towards or away from the proximity sensor along the detection plane;
• at each incremental move of the object, activating a plurality of the emitter-detector pairs (E, D) to measure detections at detectors D;
• and
• calibrating the target positions p(E, D) in the detection plane according to the distances between the sensor strip and the reflective object at which maximum detections are measured.

A proximity sensor for identifying a location of a proximal object, comprising:

• a housing;
• a plurality of light emitters, denoted E, mounted in said housing for projecting light out of said housing along a detection plane;
• a plurality of light detectors, denoted D, mounted in said housing, operable when activated to detect amounts of light entering the housing along the detection plane, whereby for each emitter-detector pair (E, D), when an object is located at a target position p(E, D) in the detection plane, corresponding to the pair (E, D), then the light emitted by emitter E is scattered by the object and is expected to be maximally detected by detector D;
• and
• a processor connected to said emitters and to said detectors, operable to synchronously activate emitter-detector pairs, to read the detected amounts of light from the detectors, and to calculate a location of the object in the detection plane from the detected amounts of light, in accordance with a detection-location relationship, denoted D→L, that relates detections from emitter-detector pairs to object locations between neighboring target positions in the detection plane.