Abstract: A touchscreen system for locating an opaque object in a target region, detects interruption of light beams, using two or more independent touchscreens (TS1, TS2), arranged to provide redundancy, each of the touchscreens having one or more optical emitters (10) to create the beams, and one or more optical detectors (30) to provide detection signals, and circuitry (90) to determine location coordinates of the opaque object from the detection signals. Detection circuitry or software integrates (470) an output of a switching inverter (440, 450), which switches between outputting an inverted or not inverted version of each detection signal, in phase with the modulation of the corresponding emitters. It can use wavelengths compatible with night vision equipment.

Abstract: A touchscreen system for locating an opaque object in a target region, detects interruption of light beams, using two or more independent touchscreens (TS1, TS2), arranged to provide redundancy, each of the touchscreens having one or more optical emitters (10) to create the beams, and one or more optical detectors (30) to provide detection signals, and circuitry (90) to determine location coordinates of the opaque object from the detection signals. Detection circuitry or software integrates (470) an output of a switching inverter (440, 450), which switches between outputting an inverted or not inverted version of each detection signal, in phase with the modulation of the corresponding emitters. It can use wavelengths compatible with night vision equipment.