GB1118021A - Improvements in or relating to periscopes - Google Patents

Abstract

1,118,021. Sextants. BARR & STROUD Ltd. June 15, 1953 [Aug. 5, 1952], No. 19635/52. Heading G1F. [Also in Division G2] The periscope-sextant 14 of a submarine is provided with means for measuring the angle between a distant object and a datum mark near the observer, the means comprising coarse mechanical adjustment to bring the object into the field of view and fine relative adjustment between the datum mark (or its image) and the image of the object. The normal view from the periscope is through a window 13 with optical systems 19, 20, 23a and 28, 30, 29 swung aside, angles being measured by view through a second window 21. To bring a star or other distant object into view a prism 24 is rotated in precise steps about an axis perpendicular to the plane of Fig. 2, by means of a Maltese-cross mechanism, Fig. 3, or a stepped cam, Fig. 4 (not shown), to avoid backlash error in the long shaft 33. Fine adjustment between steps is provided by movement of the datum mark, a bubble 29, or of the lens 30, Fig. 9 (not shown) or of an additional prism 46 Fig. 10. To allow for distortion of the periscope, graticules may be included in the upper and lower optical systems, with zero adjustment of the datum mark, Fig. 11 (not shown). The periscope may be arranged with normal view (without system 19, 20, 23a) through the angle measuring window.