Laser touch panel reflective surface aberration cancelling

A method and apparatus that distinguish a valid touch from an optical aberration caused by unwanted objects and/or scratches in the light plane of an optical touch panel device is disclosed. During a training mode the device learns the relative position of "aberration dropouts" caused by the unwanted objects. During normal operating mode the relative positions of "touch and aberration dropouts" are generated and compared with the relative position of aberration dropouts to distinguish between aberration dropout signals and touch dropout signals. The touch dropout signals are subjected to further processing to determine the precise location of a touch while the aberration dropout signals are discarded.