A touchscreen system for locating an opaque object in a target region, detects interruption of light beams. Each of the touchscreens have one or more optical emitters (10) to create the beams, and one or more optical detectors (30) to provide detection signals arranged to use emission wavelengths which are compatible with night vision apparatus, and having an NVIS radiance smaller than 1.7 10−11 NR.