GB1262548A - Indicator system for angle-measuring instruments including an altitude circle - Google Patents

Abstract

1,262,548. Theodolites. CARL ZEISS JENA VEB. May 6, 1969, No.23074/69. Heading GIF. [Also in Division G2] An indicator system for angle measuring instruments e.g. theodolites, having an altitude circle 1 with only one scale, diametrically opposite points 3, 4 on the scale being used to provide a reading, by means of an optical system arranged so that an image of one point 3 is produced in a plane 7 different from that containing the other point 4, prisms 10, 11 for combining light from the image of the first point 3 and the second point 4 itself being located between the plane 7 and the plane containing the point 4. The image in the plane 7 of the point 3 is produced by an optical system comprising a ridge prism 8 which produces lateral inversion, lenses 6 in a mount 5, and a pentaprism 9. The mount 5 is suspended on cross-tapes 16 to compensate for tilting of the device about the plane containing the circle 1, but may be fixed if compensation is not required. The prisms 10, 11 are arranged to reflect light from the image plane 7 and the point 4 along the optical axis O-O of a viewing system 15 an opaque cover 14 being provided on part of the lens 10. In an alternative embodiment one of the prisms 10, 11 may be a ridge prism to produce lateral inversion of its associated image, and these two prisms may be pendulously suspended to compensate for tilt in place of the lenses 6 in the mount 5.