GB451297A - Improvements in devices for the decomposition or recomposition of pictures, particularly for purposes of television - Google Patents

Abstract

451,297. Television. TRAUB, E., 34, Dartmouth Road, Cricklewood, London. March 30, 1935, No. 9970. Drawings to Specification. [Class 40 (iii)] Relates to a device for the decomposition or recomposition of pictures, particularly for purposes of television, comprising a rotating polygonal member each face of which carries a reflecting surface set at an angle to the axis of rotation different from that at which the corresponding surfaces of the outer faces are set. According to the invention, a part only of the required angular spacing between the beams reflected from these surfaces is obtained by their varying inclinations to the axis of rotation while prisms of varying angles are mounted in front of the reflecting surfaces to effect the remainder of the required spacing. The arrangement is preferably such that approximately 60 per cent of the total angular divergence between beams of light reflected from the various faces of the rotating member is produced by the prisms, the remaining 40 per cent being produced by the varying inclinations of the reflecting surfaces. The rotating polygonal member may be an ordinary Weiller mirror drum or it may be of the kind described in Specifications 425,552 and 440,055. The prisms may be cemented to reflecting surfaces secured upon the rotating member or the reflecting surfaces may be formed by silvering the rear faces of the prisms. In order to avoid the production of ghost images on the screen, the prisms are preferably tilted so that their rear surfaces lie at a small angle to the reflecting surfaces. Various arrangements of the prisms are described when the invention is applied to the devices described in Specifications 425,552 and 440,055. Thus, where each face of the rotating member comprises a single reflecting surface, the prisms may extend over the whole or a part only of the faces whilst in the case in which each face comprises two reflecting surfaces either or both surfaces may be provided with a prism. Further, when each face comprises two reflecting surfaces, the surfaces of one set being all at the same angle to the axis of rotation whilst the surfaces of the other set are all at different angles to the axis, the prisms are preferably applied only to the latter set of surfaces. With such an arrangement it is also preferable to give all the reflecting surfaces an equal inclination (additional to the differential inclinations already given to some of the surfaces), such that the mean position of the beam of light leaving the device is substantially perpendicular to the axis.