Improvements in or relating to Optical Instruments specially suitable for use as Gun Sighting Telescopes.

摘要

1511. Grubb, Sir H., Beck, C., and Beck, H. C. Jan. 18. Periscopes.-In a multiple-power periscope, all the optical elements forming the primary image on the graticule are rigidly fixed, and never more than twelve air-glass surfaces are employed. As shown, the graticule is on the face f of the upper prism c, the vertical face of which has a lens front e the curvature of which is such that the rays impinge on the surface c' at less than the critical angle, so that this surface need not be silvered. The radius of curvature of the face e may be equal to the axial thickness of the prism. The two lenses i, j of the ocular are at right - angles to one another with the prism h between them. Rotation of the handle k moves the lenses i, j to give the varying magnification while keeping the ocular in focus on the graticule. There may be two interchangeable lenses so that a higher and lower power eyepiece can be obtained. In a modification, the ocular a is below the prism c, and a solid block with an upper face curved to a radius equal to the thickness of the block is placed in the main tube.