Abstract: In order to eliminate the influence of temperature on the focus of an IR optical imaging system, radiation from an auxiliary heat source is deflected through the IR optical imaging system such that said radiation impinges on an autocollimating reflector from where it is reflected back into said IR optical imaging system and then impinges on detector elements which are arranged in a detector image plane. Electrical signals generated by the affected detectors are analyzed, digitized, and then compared in a computer whose output signals control a motor for adjusting the axial position of at least one of the optical lens elements of the IR system such that the autocollimating condition between the auxiliary heat source and its image in the detector plane is maintained at all times.

Abstract: The presence of an operating helicopter within a given field of view is remotely and passively monitored by optically imaging the field of view at a focal surface, using an infrared detector to produce an electrical signal. The electrical signal is filtered with a narrow pass-band having a center frequency which is adjustable over a range which spans the respective modulation frequencies of characteristic infrared radiation emitted by the rotating blades of each of a plurality of helicopters of different type. Provision is made to indicate such component of the electrical signal as survives the filtering step.

Abstract: In a device for the transmission of information between two apparatus parts which rotate relative to each other with the use of a modulated luminous flux and a photosensitive receiving means, it is seen to it, by the introduction of diaphragms within the ray path that the modulated luminous flux does not strike the receiving means directly. In this way the radiation flow received with constant transmission signal by the receiving means is prevented from experiencing modulation upon rotation of the two apparatus parts with respect to each other.

Abstract: An Nd:YAG laser of small size with a passive quality switch is combined with a slit-lamp instrument, to form an ophthalmological combination instrument for diagnosis and treatment. By a plurality of pulses within a pulse train, which succeed each other within the .mu. sec range, particularly good therapeutic effects are obtained. A second laser, emitting continuous visible radiation, has its beam aligned with the beam of invisible radiation from the first laser, and shows the user at all times the location of the beam of invisible radiation. The visible beam of radiation is split into two beams separated from each other by a light-free zone, and there is provision for blocking and unblocking these two beams alternately, which produces an effect which greatly aids the user in accurate focusing. This combination instrument affords the user the possibility of making a diagnosis and following it immediately by treatment.

Abstract: The invention contemplates circuit arrangements to protect the target of an image-producing tube from injuriously high local current densities, wherein detector means is responsive to produce an electrical pulse at onset of an unacceptably high local-illumination intensity condition at the cathode. The target-cathode excitation circuit includes switch means with a resistance-changing characteristic, and so connected to respond to the electrical pulse as to rapidly reduce electron flow between the cathode and target of the tube, upon occurrence of such electrical pulse output.