Optical proximity sensors

An optical method for identifying locations of objects in a plane, comprising:

• serially projecting light beams, by a plurality of light emitters, along a detection area, from a plurality of locations along an edge of the detection area, wherein the light detectors and the light emitters are alternatingly arranged in an array, and whereby a reflective object inserted into the detection area reflects the projected light beams;
• directing the reflections of said projected light beams arriving at the edge of the detection area onto a plurality of light detectors, in a manner that maximizes amounts of reflected light arriving at the detectors when the reflective object is located at any one of a set of primary positions in the detection area, wherein those primary positions along the path of each projected light beam are associated with that light beam and with a respective one of the detectors;
• and
• calculating two-dimensional coordinates of the object in the detection area based on those of the light beams causing detected reflections, the outputs of the detectors, and the corresponding associated primary positions.