Abstract: Disclosed is a single lens reflex still or motion picture camera of the type having an active infrared rangefinder. In order to obtain a compact construction of the camera, the receiver of the rangefinder includes an infrared image plate which is located in close proximity to the viewfinder plane and includes a small-area infrared light reflecting surface embedded in the body of the infrared image plate and being inclined at an angle thereto, so as to direct infrared light rays to an infrared sensor which adjoins a lateral end face of the infrared image plate.

Abstract: To detect an intrusion the apparatus projects one or, better, two beams of infrared rays in a direction selected by the user. A lens collects part of the radiation diffused back by the surface on which the beam impinges (whose distance must be in the range covered by the apparatus) and concentrates the collected radiation to form an image, almost pin point, of the "illuminated" surface. The position of said image depends on the distance of the surface impinged on by the beam. A photodetector provided with a slit placed in front is displaced until it detects the radiation forming the image. When the intruder intercepts the beam, the image of the "illuminated" surface, which is now on the intruder, will shift sideways enough to prevent the rays from passing through the slit and therefore from reaching the photodetector. The absence of the photodetector output signal indicates that an intrusion is occuring.

Abstract: To measure the distance to a selected object, the range finder transmits infrared light in a beam having a straight limiting edge on one side. The object reflects light back from the illuminated region and a lens receives part of the light and creates an image of the illuminated region including the straight limiting edge on a plane inclined at an angle to the optical axis of the lens. A detector, including a photoelectric transducer part of which is masked by a mask having a straight edge, is moved along the plane until the edge of the mask and the edge of the image are aligned as closely as possible. The position of the detector when this alignment takes place is indicative of the distance of the object from the range finder.

Abstract: The suspension of movable system instruments, for example, a galvanometer, introduces elastic reset torques upon deflection. To compensate for such torques and render the apparatus essentially independent of the deflection torques, an opto-electronic device provides an output signal representative of the deflection which is combined with the deflection voltage applied to the galvanometer to at least in part compensate for the reset torque introduced by the moving system suspension.