Patent GB-723174-A (GB)
Title: Colour television receivers
IPC: H04N11/22
Filed: 1952-10-03
Abstract: 723,174. Cathode-ray tubes. STANDARD TELEPHONES & CABLES, Ltd. Oct. 3, 1952 [Oct. 6, 1951], No. 24848/52. Class 39 (1). [Also in Group XL (b) ]. A cathode-ray tube device is provided with a storage electrode on which one or more chargeimages is/are " laid-on by individual " writing " beams and. read-off either by a separate " reading " beam to produce signals representative of the charge image or, by means of a "flood" beam and suitable light producing phosphors, to produce visible images corresponding to the charge images. Fig. 1 shows one arrangement in which the storage electrode comprises an insulating layer 8 mounted on a back plate electrode 9 the charge image being " written " by means of an electron gun 3 and " read-off " by means of a similar gun 2 to produce signals across impedance 19 representative of the charge image. Three such tubes are employed in a three colour television receiving system of the charge-images on each tube being " laid-on " of colour field rate and continuously " read-off " to provide simultaneous colour component signals Fig. 2 not shown). In a second embodiment employing a single tube (Figs. 3, 4 and 5) the electron gun device provides three separate " writing " beams by means of an indirectly heated elongated cathode 48 and separate perforated control electrodes 49, 50, 51 and also provides a "flooding " beam by means of an indirectly heated electron-emissive disc 52 provided with perforations 81, 82, 83 for the separate writing beams. In this embodiment the storage electrode 42 is provided with a large number of perforations through which electrons from an electron "cloud" established between electrode 42 and a mesh screen 43 from the "flood" beam are continuously attracted by electrodes 44, 44a these electrodes forming images corresponding to the charge images on separate areas 45, 46, 47. These areas may carry phosphors which luminesce in the separate component colours appropriate to the separate charge images and alternatively; the phosphors may luminesce in white light separate colour filters being employed to provide the separate colour images. In this embodiment the "writing" beams are each keyed "on" at colour field rate and the "flood" beam which is continuously effective to produce the luminous images may cover the entire mesh screen 43 without deflection or may be arranged to scan each charge image area at the same or at a higher rate than the "writing" beam. To obtain television signals corresponding to the charge images the " flood" beam may be replaced by three separate "reading" beams and the phosphors 45, 46, 47 replaced by conductive pick-up signal plates. In a modification of the arrangement of Figs. 3, 4, 5, the three charge images on electrode 42 are arranged as shown at 84, 85, 86 (Fig. 7) and focussed by means of electron lenses 87, 88, 89 (Figs. 6 and 7) through openings 90, 91, 92 in a device 94 (which also forms part of the lenses) and then through an apertured screen 95 (forming part of device 94) so as to impinge the different colour phosphors of a " directional " screen 96 at appropriate angles. Screen 96 may alternatively produce white light colour filters being appropriately placed to produce the desired colour images.