GB438903A - Improvements in or relating to television, and like systems - Google Patents

Abstract

438,903. Television. BAIRD, J. L., and BAIRD TELEVISION, Ltd., 58, Victoria Street, Westminster. June 14, 1934, Nos. 17662, 22928, 23569, 28185, and 28186. [Class 40 (iii)] Relates to scanning systems in which a mirror drum performs a plurality of revolutions in scanning the image. According to one aspect of the invention, the light incident upon and reflected from a mirror drum 3, Fig. 1, passes through a single projector lens 2. According to another aspect, the scanning aperture 1, Fig. 2, or its equivalent, e.g. an image of the aperture 1 on a mirror 6, is located on the centre line of the solid angle bounding the light rays between the screen 4 and the drum 3, and a lens 2 is also positioned on this centre line. Optical stops 14, Fig. 3, may be placed in the plane of the aperture 6 so that the scanning ray has the same intensity in its extreme positions as in its central position. According to a further aspect, the effective aperture is moved to provide an interlaced scanning. An aperture 1, Fig. 4, illuminates an oscillatory mirror 7 which provides the interlacing and an image of the aperture is formed on mirrors 10 spaced round a rotating disc 9. The disc 9 rotates so that the light reflected from the drum 3 passes between the mirrors on the disc. At a receiver the disc may have a matt surface and the image be formed on the disc. An oscillating mirror 11, Fig. 5, may produce a moving image of an aperture 1 on a mirror 12 to provide one component of scanning, the other component being provided by the drum 3. The mirror 11 may be replaced by two mirrors at right angles, oscillated by a cam, so that the beam is always incident on the mirror 12 at the same angle. Specifications 328,616, [Class 40 (iii)], 381,898, 430,570, 433,720, and 434,527 are referred to.