GB279457A - - Google Patents

Abstract

279,457. British Thomson-Houston Co., Ltd., (Assignees of Alexanderson, E. F. TV.). Oct. 19, 1926, [Convention date]. Television apparatus; copying - telegraphs.- Four or more adjacent elements of a picture simultaneously affect an equal number of light-sensitive cells in a television transmitter, and a corresponding arrangement is adopted at the receiver, a single scanning device being used ir. each case. In the receiving apparatus shown in Fig. 3, signals corresponding to four adjacent elements of the transmitted picture are received by four aerials 26 which control four oscillagraphs 18 so as to vary the intensity of four light pencils which pass to the screen 12 by way of lenses 22, mutually inclined mirrors 16, and a common lens in the spiral series of lenses 14 which is carried by a rotating cylinder 13. The pencils therefore trace out four adjacent vertical lines of illumination 23, and as successive lenses 14 come into action successive bands each comprising four component lines of the picture are traced out. The arrangement at the transmitter (Fig. 1, not shown) is similar : four optical images of the picture are projected by lenses and by four mutually inclined mirrors upon four light-sensitive cells, so that each cell coincides with one of four adjacent picture elements. The pencils forming the four optical images all pass through a lens 14 and are traversed thereby. In modifications (Figs. 4 and 5, not shown) the spiral series of lenses 14 may be replaced by a series of plane mirrors inclined to the axis of the cylinders at slightly different angles. In the modified receiver shown in Fig. 6 seven adjacent light pencils proceeding from a constant source of illumination 40 pass through a polarizer 42 and between seven pairs of plates 48 in a Kerr cell 43, so that the planes of polarization of the pencils are rotarily displaced under the control of received signals applied through the leads 49. The pencils then pass through an analyzer 44 and are projected by a lens 45 and mutually inclined rotating mirrors 32 on to the screen 12. The advantages of the system are that strong illumination is obtained since several pencils are used simultaneously and large lenses can be used since the lenses can be rotated at a slower speed than usual. The invention is applicable to vibrating- mirror or other systems as well as to those employing rotating spirals; it is also applicable to copying, telegraphs, and the invisible parts of the spectrum may be utilized in the transmitter or in a photographic receiver. Wireless or line signals may be used.