Optical encoder

An incremental optical encoder, comprising:

• a movable element;
• a fixed element;
• at least one pair formed of a luminous emitter and of a luminous detector which are secured to the fixed element, the emitter producing a luminous radiation that the detector can detect;
• at least one mark secured to the movable element, wherein during the motion of the movable element with respect to the fixed element, the mark being able to place itself in the path of the luminous radiation to be detected by the detector;
• a plane printed circuit, secured to the fixed element and on which the pair of emitter and of detector is arranged;
• and
• an opaque mask secured to the printed circuit, the mask making it possible to limit the angular field of the luminous radiation, wherein
• the mask surrounds at least one of the emitter and the detector and comprises a window defining the angular field,
• the mark forms an element reflecting the radiation arising from the emitter towards the detector,
• the mask makes it possible to avoid the establishment of a direct radiation between the emitter and the detector, and
• the encoder comprises a mask that can interrupt the luminous radiation by shutting off the window when the reflecting element does not return the radiation emitted by the emitter.