Surveying layer

摘要

An object reflector detection system, for example, for use in surveying, comprises a laser beam emitter (3) which is arranged to emit a circularly polarized light beam towards an object reflector (2, 2'). The object reflector has a first reflection area which simply returns the incoming beam with polarization unaltered, and a second reflection area which returns the beam with an altered polarization. First and second detecting means (24, 25) are provided for detecting the altered and unaltered returning beams. The position of the object reflector is then determined based upon a comparison between the respective outputs of the first and second detection means. <IMAGE>