Abstract: It comprises an optical system, two optical fibres on either side of the optical axis of the optical system and longitudinally stagered along said axis and, for each fibre, injecting light into the fibre and detecting the light emerging from the fibre following reflection on an object, the latter being positioned facing the optical system. Electronic processing of the signals supplied by the detector to determine the displacement of the object relative to the optical system and possibly the distance between the object and the optical system.The system has application to the inspection of mechanical parts.