GB460709A - Television transmitter - Google Patents

Abstract

460,709. Television. RADIOAKT.- GES. D. S. LOEWE. July 31, 1935, Nos. 21691 and 21692. Convention. dates, Aug. 4, 1934 and Aug. 11, 1934. [Class 40 (iii)] The area of an optically projected image 24 of an object 3a to be transmitted is illuminated by additional constant light. The film 3 is moved continuously and the line scanned by the circle of apertures in a disc 5 is at the edge of the area which would be illuminated by rays 33 from a source 1. The unused light is removed from the main beam by a reflecting- prism 34 to illuminate a mask 35, which is projected on the area 24 by prisms 36, 39, 40 and lenses 37, 38. The intensity of the auxiliary illumination is controlled by a diaphragm 41. To compensate changes in the intensity of the light source, light falling on a white surround 43 on the mask is reflected to a photoelectric cell 44 which controls the grid bias on a valve 47 in the signal amplifier. The spacing of the scanning apertures is greater than the width of the projected image, and a number of apertures are omitted at the end of each frame, or a rotating diaphragm interrupts the light, Fig. 5 (not shown). The auxiliary illumination is of such intensity as to ensure that the aerial current falls to zero in these intervals, Fig. 2 (not shown), whatever the nature of the picture transmitted. According to modifications, the auxiliary illumination is obtained from a separate source, Fig. 5 (not shown) ; the same lenses 4, 4<1> are used for projecting the film and the mask 35, Fig. 7 (not shown). When using a mosaic-screen type of transmitter, the cathode ray sweeps an area greater than that illuminated by the image and auxiliary lighting.