Abstract: A shaft is borne in a standard by an intermediate member and a supporting bearing so that the shaft may follow without constraint lateral shifts of the supporting bearing by tilts about a plurality of small angles located in different planes. This effect is achieved by providing one of two guiding rings for the shaft within the intermediate member with two small sliding projections. These projections may be vertically arranged on a diameter of the intermediate member, which in turn is mounted to the standard by two small seat-engaging surfaces which are horizontally arranged on a diameter of the intermediate member. The apparatus is preferably used with shaft angle encoders for theodolites.

Abstract: The apparatus comprises a stable carrier plate for carrying prisms cemented thereto and conducting an optical ray path from its source to a position sensitive photoelectric receiver. A liquid horizon is provided on the carrier plate for shifting the optical ray path if the apparatus is inclined. A design stable against temperature and mechanical stress with a flat and compact shape is achieved in an easily mountable two axes inclinometer.

Abstract: A bearing bush with a side opening is mounted within a telescope barrel. The telescope thus may be easily mounted on a tilting axis by simply inserting an axle into the bush. Mounting and adjustment of the tilting axis within its bearings and of angular measuring systems is thus independent of mounting of the telescope.

Abstract: The supporting body of an instrument is joined to a casing by means of ribs fitting into guideways angularly spaced around a centerline of the supporting body. Thereby, small clearances between the ribs and guideways in a direction parallel to the casing wall surfaces are effective in limiting play at right angles to the casing walls, where much greater clearances must be provided. The casing may expand or shrink freely without exerting strains on the supporting body that could interfere with the proper function of the instrument, due to the large radial clearances between the ribs and guideways.

Abstract: This invention provides an infrared lens system for the wavelength range of 3.5 .mu.m-5 .mu.m of F/1 and having an angle of field of 3.2.degree.. The lens system consists of three lens elements. As viewed from the object side the first element is a positive lens (1) made of silicon (Si), the second element (3) is made of calcium fluoride (CaF.sub.2) and the third is a positive lens (2) made of silicon (Si). This lens system is intended for use in a thermal imaging device, having a scanning mirror (4) and a radiation detector (5) with a sapphire cover (6). Thus a low cost achromatic infrared objective system is provided.