Patent attributes
In an optical touch display system, light from a primary source can be retroreflected to a detector in the absence of an object in the detection area. When an object is present, its position can be triangulated based on the direction of its shadows at the detectors. Accuracy can be improved with a secondary light source positioned off-axis from the primary light sources so that minimal light from the secondary source is retroreflected to the detectors. Instead, when an object is present, light from the secondary source may be reflected directly from the object. Each detector signal representing light due to the primary light source can be corrected to remove light reflected directly from the object based on identifying and removing a signal component representing light from the secondary light source. In some embodiments, this is facilitated by phasing the primary and secondary light sources.
