US Patent 9791569 Coordinate measurement system and method

A position detection system is able to detect the three dimensional position of at least one target (10). Each target (10) is configured to act as a retro-reflector for light incident from any direction. At least one light emitter illuminates the at least one target (10) and at least one detector (24) is provided for detecting and taking measurements of light retro-reflected from a target (10). There is also provided a processor for processing measurements taken by each detector (24) to determine the three dimensional position of the at least one target (10).