Optical touch sensor

A method for detecting locations of objects in a plane, including emit light beams, one at a time, at locations along a first edge of a detection area, refract each light beam into multiple divergent light beams, direct each of the divergent beams to arrive at a respective pair of focusing lenses mounted along a second edge of the detection area, opposite the first edge, wherein an intensity profile of each divergent beam has maximum intensity along the center of the beam, for each of the focusing lenses, measure an intensity profile of that portion of the divergent beam that enters the focusing lens, for each pair of focusing lenses receiving a single divergent beam, compare the measured intensity profiles for light arriving at each lens, and determine a location of an object that partially blocks at least one of the divergent beams, based on the compares.