Patent GB-757071-A (GB)
Title: Improvements in colour television receivers
IPC: H04N9/26
Filed: 1952-04-02
Abstract: 757,071. Colour television tubes. CHROMATIC TELEVISION LABORATORIES, Inc. April 2, 1952 [April 4, 1951], No. 8353/52. Class 39 (1). A colour television receiver has adjacent the target two electrode structures designed to form a multiplicity of cylindrical electron lenses equal in number to the number of elementary phosphor groups to bring the beam to a line focus on a given phosphor element, and one of the electrode structures comprises two sets of interleaved linear conductors between which potentials can be applied for colour switching. In one form, Figs. 2, 3, the lens structure comprises two sets of interleaved strips 27, 271 set in glass or ceramic bars 29 and connected to leads 33, 331 respectively, and one or more electron permeable electrodes 35, 37 mounted in front of and/or behind the strips 27, 271; 35, 37 may be of fine gauze mesh or thin aluminium foil carried on frames 41. Electron permeable electrodes 35, 37 are at about final anode potential, or 37 may be more positive than 35, and 27, 27<SP>1</SP> are relatively negative, and it is stated that the combination is equivalent to a plurality of cylindrical lenses which focus the beam in a narrow line on the fluorescent screen. For a three-colour system the screen is divided into sets of red, green and blue phosphor-coated areas corresponding to each pair of strips 27, 27<SP>1</SP>. The beam normally impinges on a green area and is shifted to red or blue areas by a potential difference applied between the sets of strips 27, 27<SP>1</SP>. Since the deflections are of opposite sign in adjacent lenses the colour areas must be arranged in reverse order correspondingly. Alternatively a two-colour system or in general a system with any number of colours may be used. As shown, the screen consists of rectangular sectioned glass rods 47 side by side each of which has three phosphor strip coatings and on the phosphors and also between the rods is deposited thin light-reflecting aluminium layer 49, Fig. 4. The viewing surface 51 is ground to make it light diffusing so the apparent source of light does not move relative to the observer. The " red phosphor may be an orange-emitting compound containing beryllium and is provided with a red filter, the other phosphors not having filters. The rods 47 may be composite as indicated by dotted lines 55; the coatings may be deposited on the smaller rods before fusing them together. The deflecting potentials for strips 27, 271 are supplied by a colour control generator arranged to synchronize with field, line, segment or dot sequential systems. Coating 49 may be at the same potential as mesh 37 but is preferably much more positive, e.g. by about 50,000 volts, to increase the image brilliancy. Two gun anodes form a lens focusing the beam to a reduced image which is then refocused by electromagnetic means (not shown) approximately in the plane of the screen. The target 25 may be a separate structure mounted on a frame as shown or may be mounted on the end face of the tube. In a modification, Fig. 6 (not shown), the lens electrodes are 27, 271 and coating 49, electrodes 35, 37 being dispensed with. In further forms, Figs. 7, 8, 9 (not shown), a single positive gauze electrode is placed between two sets of less positive strip electrodes or three sets of strips of successively increasing positive potentials towards the screen are used. The aluminium coating 49 may be dispensed with in these cases. The intermediate set of strips may be positive to both the outer sets of strips. In another form, Fig. 10, narrow strips 63, 631 placed opposite the junctions between the fluorescent strips and all connected together are at a higher potential than strips 27, 271 and form a lens therewith. Coating 49 may have a still higher potential to increase the image brilliancy. In another embodiment, Fig. 11, the lens is formed between strips 27, 271 and 73, 731, the latter strips carrying the red and blue phosphors and the member 25 the green phosphor. Strips 73, 73<SP>1</SP> are all connected together. In a modification, Fig. 12 (not shown), the strips 73, 73<SP>1</SP> are T-shaped in section, the top of the T adjacent the surface 25 being of transparent material and also being phosphor coated. In another modification, Fig. 13 (not shown), the strips 73, 731 are uncoated, the phosphor coatings being all on 25. In another form, Fig. 14, the lens has gauze electrode 35 and narrow strips 79 which alternate with wider strips 27<SP>11</SP>, the latter strips being all at the same potential. Strips 79 if at the same potential as strips 27<SP>11</SP> leave the beam focus undisturbed, as shown, but when negatively biased split the beam into two parts with diaplaced focal points and so change the colour of response. In a modification, Fig. 16 (not shown), the narrow strips 79 are at the lefthand side of the space between strips 27<SP>11</SP> and the second lens electrode is a coating on the screen. In all forms additional electrodes may be provided to make the focus sharper or to increase the post-acceleration, and it is stated that post-acceleration may be replaced by retardation.