Patent GB-493043-A (GB)
Title: Methods of and arrangements for television transmission with an electronic tube as image disintegrator
IPC: H04N3/10
Filed: 1937-01-29
Abstract: 493,043. Cathode-ray tubes ; electron multipliers. RADIOAKT.-GES. D. S. LOEWE. Jan. 29, 1937, Nos. 2675 and 2677. Convention dates. Jan. 29, 1936 and April 4, 1936. [Class 39 (i)] An optical image to be transmitted is projected on a coherent photo-electric layer and the electron image thus produced is focused on a sensitive mosaic surface which is then scanned by a light-ray; the liberated electrons are multiplied by secondary emission and employed to produce an image-signal. In the arrangement shown in Fig. 1, an image of the object 3 is projected by a lens 2 and a mirror 4 situated within the tube, as described in Specification 489,362, on to the photo-electric screen 1. The photo-electric image produced is focused by cylinders 5, 6 on to a mosaic screen 8, backed by an earthed plate 37, the electron stream being turned through an angle of 45 by a magnetic field 10 and retarded by a cylinder 45 until its speed is insufficient to liberate secondary electrons from the mosaic screen 8. The screen 8 is then scanned by a light-ray, and the liberated electrons multiplied at secondary emissive surfaces 15, 17, the magnetic field 10 and anode plates 14, 18 accelerating and directing them. In the arrangement shown in Fig. 2, the image is projected on to a perforated photo-electric screen 23 through openings in the mosaic screen 24. The liberated electrons pass to the mosaic screen 24 and are there stored, being again liberated by a scanning light-ray passing through the openings in the screen 23. The electrons thus liberated are drawn through the openings in the screen 23 and focused on to a secondarily emissive surface 15 by cylinders 30, 31. The electrons emitted from the electrode 15 are focused by cylinders 33, 34 on to a collecting anode 17. The electrons passing between the screens 23, 24 may be accelerated by a net electrode 26. In the arrangement shown in Fig. 4, an electrode 27 is placed in front of the screen 24 and an electrode 27a behind the screen 23. These electrodes and the screen 23 are connected in the manner shown to a source of alternating current, the frequency of which is at least twice the maximum video current frequency and may be used for a carrier wave. Fig. 6 shows an arrangement in which the electron image from the screen 1 is focused by the electrodes on to the screen 8, being suitably retarded by electrodes 83, or by a high-resistance helical conductor on the surface of the tube. A magnetic field 10 deflects the electron stream as shown and also deflects the stream emitted from the screen 8 into an electron multiplier consisting of tubular electrodes 30, 34 and a bent tube 31 at the angle of which is a secondarily emissive surface 59. The Specification as open to inspection under Sect. 91 also includes the subjectmatter now described in Specifications 491,247, 491,443, 492,961, and 2679/37, also the arrangement shown in Fig. 5 (Cancelled), according to which a ray from a cathode 36 scans a mosaic screen 7a on which the image to be transmitted is projected. The electrons liberated are collected by an anode 42 and transmitted to an amplifier 44. This subjectmatter does not appear in the Specification as accepted.