GB434876A - Improvements in and relating to television and the like systems - Google Patents

Abstract

434,876. Television transmitters. BLUMLEIN, A. D., 7, Courtfield Gardens, Ealing, London. Feb. 5, 1934, No. 3776. [Classes 39 (i) and 40 (iii)] The reverse signal current effects due to sudden changes in general brightness of an object 8 projected on a photo-sensitive screen 1, which is scanned by a cathode ray beam, are compensated by the provision of an auxiliary photo-electric cell 13 which receives light from the whole of the object and has its anode 14 connected to a tapping point on the resistance 10. Alternatively, the relative amounts of light falling on the screen and cell 13 may be adjusted by suitable diaphragm stops. If desired, the cell 13 may be mounted in the envelope 2. When transmitting pictures from film with such an arrangement, the film may be moved forward during the scanning cycle and light from a source additional to that used for illuminating the screen 1 may be passed through the film on to the cell 13. In order that the average illumination may be transmitted, the D.C. component of the signal may be established at some convenient point, e.g. as set forth in Specification 422,906, the cathode ray being cut off at the end of each scanning stroke. Specifications 431,207 and 431,258 also are referred to.