Patent GB-838624-A (GB)
Title: An electrical display device
IPC: G11C19/06
Filed: 1956-05-03
Abstract: 838,624. Monogrammic signs. RADIO CORPORATION OF AMERICA. May 3, 1956 [May 31, 1955], No. 13737/56. Class 118 (2). [Also in Groups XXXIX, XL (a) and XL (b)] An image display device 2, Fig. 1, for pro. ducing a luminous image in accordance with periodically occurring electrical signals, particularly for use in television, radar, computer displays and image reproducers in cinematography operated by tape recordings of the image, comprises an array of individually controllable electroluminescent cells 9, first and second sets of co-ordinate conductor paths j, k, over which the signals are applied for varying the emission of light from the cells, and a plurality of transhysteretic control devices 8 utilizing magnetic material and provided with electrical connections to the cells, the conductor paths being coupled to the control devices and the control devices being coupled to electrical power supplying means, the control devices being each capable of continuingly adopting a setting at any degree of flux density within a given range, and the particular setting adopted by each of the control devices being determined by said signals and stored in the control devices whereby the value of the electrical power transmitted to the cells through the said electrical connections receives a continuing control by the periodically occurring electrical signals. An incoming television signal arriving at 3 is applied to the receiver 4 where it is recovered in the form of a video signal and synchronizing signals. The synchronizing signals are applied to a shift signal generator 5 which actuates the column selector circuit 7 and the row selector circuit 6. The video information is passed to the row selector circuit 6 or to the column selector circuit 7. The selector circuits 6, 7 energize the respective conductors of the image reproducer 2. Power is made available at every intersection of the conductors in amounts controlled by the signals. The electroluminescent cells may employ phosphors of zinc sulphide and zinc sulpho-selenide. In a particular example each cell is 3/8 inch square with <7>/16 inch spacing between cells and the phosphor used is copper activated zinc sulphide mixed in an " Araldite " Registered Trade Mark) dielectric layer 1.5 Î 10<-3> inches thick. The rear electrode consists of deposited silver and the front electrode of a transparent glass coating. The transhysteretic control devices 8 utilizing magnetic material are in the form of the transfluxor, Fig. 2A, which shows an apertured member such as a moulded ceramic ferro-spinel or ferrite which has a rectangular hysteresis loop. The member has two holes 12, 13 which form the three legs I, II and III. The cross-sectional areas of the legs II and III are substantially equal and the sum of their areas is smaller than the area of the leg I. In a specific example each transfluxor is made of two stacked layers, the material of which consists of MgO, MnO and Fe2O3 in the proportions of 3: 3: 4 parts by weight. Each layer is 0.140 inch thick and its diameter is 0.346 inch. The diameter of the large hole 12 is 0.138 inch and the diameter of the small hole is 0.043 inch. The centre of the large hole is located 0.017 inch from the centre of the layer and the small hole is 0.1125 inch off centre in the other direction. The transfluxor has input windings 15, 16, 18 and output winding 19 connected to load 20 whereby it can be put into blocked or unblocked condition. The transfluxor can also be operated in a half-tone mode, i.e. it can be set to any level in a continuous range in response to the amplitude of a single setting pulse through the winding 17. Once set it will produce indefinitely an output proportional to the setting. Fig. 3 shows one of the rows of transfluxors 66, 55, &c., in which a magnetic shift register is employed as the column selector circuit 7 of Fig. 1. The electro-luminescent cells are shown at 61. The register includes a series of magnetic cores 21, 22, 23, 24 each of which may be at remanence in a normal state and in an abnormal state. The line 27 passes through cores 21 and 23 and is coupled to ground through the resistor 29. The line 31 passes through cores 22 and 24 and is coupled to ground through resistor 33. The cores 21 &c. are connected to the transfluxors 66 &c. and to each other through the diodes 45 &c. and each transfluxor can be brought to a threshold of setting, video current pulse setting the flux proportionally to its amplitude. The energizing and switching of the transfluxors can be accomplished by the pulse sequence shown in Fig. 5. At the start of excitation of each line, a clear pulse 63 passes through each of the transfluxors and clears or blocks all of the transfluxors of the row, the clear pulse passing through the line 65 of Fig. 3, also passing through the core 21 to set this core to abnormal state thereby adjusting the transfluxor 66 to the threshold of setting. The shift register will produce a sequence of pulses 51 and 35 until the final core is reached, all the cores being then in a normal state until a time corresponding to the retrace time, at which time the clear pulse 53 is again produced and the cycle repeated. The pulses 67 represent the amplitude of the video information at the time each of the switching pulses are produced and the pulses 67 may be applied to the transfluxor array at a time coincident with the occurrence of the pulses 51 and 35 to adjust the transfluxors to their threshold of setting. The energy for actuating the electroluminescent cells 61 need not be applied to the transfluxors at the same time as the video pulses are applied and may be provided by trains of alternating pulses of opposite polarities, e.g. priming pulses 69 and driving pulses 71 which may occur between the pulses 51 and 35. Fig. 6 shows a circuit for producing the pulses described in connection with Fig. 3 and comprises a master clock oscillator 73 producing a master frequency signal and driving a horizontal scanning oscillator 75 driving a flipflop pulser 77 driving a delay line 79 and a driver circuit 81 for producing the pulses 35 and also driving a delay line 83 and a driver circuit 85 for producing the pulses 51 alternately with respect to the pulses 35. The horizontal scanning oscillator 75 also drives the transfluxor modulator driver 87, utilizing the delay line 89 to delay the video pulses 67, the video modulation which modulates the amplitude of these pulses being applied to the input terminal 91. The oscillator 7 5 also drives the row scanning line oscillator 93 which, by way of delay line 95, drives the clearing pulse generator 97 to provide the clearing pulse 63 at the start of the scanning of a row. The master clock oscillator 73 also drives the drive pulse circuit 101 producing the driving pulses 71, and also drives, by way of the delay line 103, the prime pulse circuit 105 producing the priming pulses 69. Fig. 7 shows several rows and columns of a mural television image reproducer, the column magnetic shift register 120 operating according to the principles described in connection with Fig. 3 to impart switching information to each column of transfluxors successively. The row magnetic shift register 160 selects the row being scanned and imparts video information to this row and utilizes transfluxors, each of which has two apertures, the left-hand aperture being larger than the right-hand aperture. A pair of trains of row scan advance pulses 161 and 162 are generated alternately by a circuit similar to the circuit described for generating the pulses 35 and 51. The line 163 carrying the pulse 161 passes through the large hole 164 of transfluxor 165, through the small hole 167 of transfluxor 169, and so on through each transfluxor of the register. The line 170-carrying the pulse 162 passes through the small hole 175 of transfluxor 165, through the large hole 177 of transfluxor 169 and so on. A composite waveform shown in Fig. 8 illustrates the timing of the various pulses applied to the shift register 160, the pulse 161 being separated from the pulse 162 by an amount sufficient to accommodate the pulse series including the prime pulses 180, and the sampled video pulses 182 of the row being scanned. The row shift register 160 is provided with two cores 221 and 223 which remedy possible malfunction of the register due to imperfect saturation characteristics of the magnetic material of the transfluxors. The magnetic core 241 absorbs pulse induced voltage during the video pulses 182 which would tend to set up improper flux conditions in the transfluxors of the rows in the array which are not selected. The prime pulse 180 passes through the winding 243 which also passes through the magnetic core 241 in a manner which returns the core to the state it was in prior to the application of the video pulse. The video information bearing line contains rectifiers 191 connected in opposite direction from the rectifiers 203 which pass the clearing pulses, the rectifiers 191 preventing the clearing pulse from being dampened by the video-information-bearing circuit and vice versa. Prime pulses 69 and drive pulses 71, referred to in connection with Fig. 5, are applied to all the row transfluxors through two windings as shown. The number of turns used with the various magnetic cores and transfluxors is stated. A mural colour image reproducer is described in which each row comprises three component lines of transfluxors and electroluminescent cells, one line of transfluxors supplying energizing information to electroluminescent cells which emit red light, a second line of transfluxors supplying energizing information to cells emitting green light, and a third line supplying cells emitting blue light. The transfluxors with their associated cells can be positioned in straight lines or can be staggered in any desired pattern. The tranfluxors may be sequentially energized, or they may be utiliz