GB627983A - Improvements in optical projection systems - Google Patents

Abstract

627,983. Optical projection systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 20, 1946, No. 21725. Convention date, July 20, 1945. [Class 97 (i)] [Also in Group XL (a)] In an optical projection system comprising a cathode-ray tube, a spherical reflector for projecting images formed on the screen of said tube and a correcting plate disposed in the light path from the reflector, a positioning member is provided which contacts the reflecting surface at at least three points so that the centre of curvature of the reflector lies on the optical axis of the correcting plate. As applied to a system for projection of television images comprising a cathode-ray tube 10, a concave mirror 18 and a figured plate 26, the positioning member consists of a cylindrical shell 36, between one end of which and a support 78 the mirror is clamped so that its optical axis is aligned with the cylinder axis. The figured plate 26 is supported on an inwardly projecting flange 44 at the other end of the shell 36, a shoulder 42 on this flange being so positioned that the centre of the plate lies on the cylinder axis; the height of the shell 36 is such that the centre of the plate lies at the centre of curvature of the concave mirror 18. The neck 31 of the cathode-ray tube is accommodated in a central aperture provided in the plate 26 and the tube surface 12 rests on a ring 33 carried by a bracket 51 on a rod 52 which may be axially moved by adjustment of the screw 53 by means of which it is secured to the shell 36. Diametrically opposite the bracket 51 is a bracket 63 having a slot to receive the end 72 of an axially movable rod 74 carried by the shell. Thus, when the shell 36 is held fast, the rods may be adjusted to vary the position of the tube face 12 in relation to the mirror 18 for focusing purposes. Specification 537,738 is referred to.