Patent GB-650102-A (GB)
Title: Image-reconstructing system
IPC: H04N3/12
Filed: 1947-09-22
Abstract: 650,102. Television receivers ; thermionic distributers ; light valves. HAZELTINE CORPORATION. Sept. 22, 1947, No. 25747. Convention date, Oct. 4, 1946. [Class 40 (iii)] A television receiving system comprises a plurality, one for each line of the reproduced image, of gas-filled electron-discharge tubes, each of which comprises a plurality of electrode systems, which are coupled via separate channels to respective elements of a display unit, the received video signals being applied in parallel to all the electrode systems and means being provided to initiate a gas-discharge between the electrodes of one electrode system at the commencement of a frame period, the discharge within one electrode system both allowing the instantaneous video signal to pass to the respective element of the display unit and initiating a discharge in the adjacent electrode system whereby a discharge occurs in all the electrode systems in turn and the elements of the display unit are all actuated in turn by the appropriate element of the video signal whereby an image corresponding to the received video signal is synthesized. The video signal is applied to the terminal V, Fig. 2, which is connected to the cathodes 25 of the gas-discharge tubes 20. Each tube also comprises a plurality of anodes 24 and intermediate electrodes 28. The tube structure which may be of the physical form illustrated in Fig. 4 of Specification 645,880, [Group XL (c)], also comprises a plurality of condensers 21 and resistors 22 which are connected as shown. Line and frame synchronizing impulses are applied via terminals L and F to an igniter electrode 26a of the first tube, the combined effects of a line and frame synchronizing impulse being sufficient to initiate discharge between the anode and cathode of the first electrode system. The first intermediate electrode thereupon takes up in the manner described in Specification 639,065, [Group XL (c)], the potential of the cathode, i.e. the then-existing value of the video-signal input. The discharge continues until the corresponding condenser 21 is discharged by which time a discharge has been initated in the succeeding electrode system by means of the spread of the ionized portion of the surrounding gas. The discharge consequently travels down the tube so that the successive. condensers 30 become charged to corresponding successive values of the video signal. The tube is so designed that the last final electrode system discharges at the end of the first line and the impulse applied to the corresponding condenser 30 is applied together with the next line synchronizing impulse to the igniting electrode 26b of the next discharge tube so that a discharge occurs once, in turn, in each electrode system during each frame period and each condenser 30 becomes charged to a corresponding value of the video signal. A delay network may be incorporated into the coupling between the final electrode system of each tube and the igniting electrode of the next tube in order to allow for the " fly-back " intervals between successive line periods. Display arrangements. The display unit, Fig. 3, comprises a uniformly illuminated screen 41 in front of which is mounted an apertured plate 42 (of which a portion is shown enlarged), the apertures being arranged in rows the number of which corresponds to the number of lines in the reproduced image and to the number of discharge tubes 20. The number of apertures in each row corresponds to the number of electrode systems in each tube. Behind each aperture is arranged an electroscope, Fig. 4, the plates 46, 47 of which constitute the plates of the corresponding condenser 30, Fig. 2. Each electrode 46 carries a shutter 49 which regulates the amount of light passing the corresponding aperture in accordance with the potential applied to the electroscope, whereby, when the plate 42 is viewed as a whole, the television image corresponding to the applied video signal is reconstituted. The display unit may be mounted in a transparent housing to protect the electroscope elements from the effects of air currents. The tubes 20 may also be mounted within the housing. The whole display unit, being a shallow structure, is suitable for wall mounting.