GB456728A - Improvements relating to the pictorial reproduction of stationary or moving objects - Google Patents

Abstract

456,728. Photo - electric apparatus. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. May 8, 1935, No. 13579. Convention date, May 8, 1934. [Classes 39 (i) and 40 (iii)] [See also Group XX] An object 1 is projected optically on a surface 5 which emits electrons, in accordance with the incident radiation, to produce an electron image of the object. The electrons are focused on a fluorescent screen 9 by perforated diaphragms which are so charged as to act as an electron lens. The optical image may be projected on the side of the cathode 51, Fig. 5, adjacent the vacuum with the aid of a concave mirror diaphragm 50. The electrons are focused by the combined actions of the diaphragm and a coil 53. According to a modification, the electrons are focused by a series of equally spaced perforated diaphragms charged to potentials proportional to their distances from the cathode, Figs. 3 and 4 (not shown). Photography, Fig. 5. A projectile 45 is illuminated by a spark discharge 43, and its image projected on the cathode. The electron image is moved over the fluorescent screen 54 by deflecting plates 58 so that images produced by successive discharge of the spark occupy different parts of the fluorescent screen. The images are photographed by a camera 59. Filters 46, 60 are complementary to prevent direct action on the camera by the light from the spark. Television transmitter, Fig. 6. The electron image is moved over the screen 61 by the deflecting plates 63 so that the image is scanned by an aperture in the screen. The electrons passing through the apertures are picked up by an insulated interceptor 62, which is directly connected to the grid of an amplifier 66. The Specification as open to inspection under Sect. 91 comprises also velocity modulation, Fig. 9, (Cancelled). When using velocity modulation, in order to keep constant the period of scanning the picture, the scanning- speed is made proportional to the total brightness of the picture, in addition to inversely proportional to the luminosity of the point being scanned. The voltage on the interceptor 76 is passed through an amplifier with a hyperbolic characteristic, to apply to the grid of variable-mu valve 82 a voltage inversely proportional to the current received by the interceptor. The grid-bias of the valve 82 is controlled through an amplifier 79 by the electron current reaching the screen 75. The output of the valve 82, after amplification, modulates the rate of charge of a condenser 85 across the deflecting plates in the cell 87 which produce the line-scanning. Each time the condenser 85 is discharged by a gasdischarge tube 88, an impulse is obtained to unblock a low-amplification screen-grid valve, which charges the condenser from which are obtained the voltages for the other component of scanning. This subject-matter does not appear in the Specification as accepted. Reference has been directed by the Comptroller to Specifications 368,309 and 368,721.