Patent GB-816109-A (GB)
Title: Electrostatic recording and reproducing apparatus
IPC: H01J29/39
Filed: 1955-09-20
Abstract: 816,109. Ferro-electric devices. PULVARI, C. F. Sept. 20, 1955, No. 26848/55. Class 37. [Also in Groups XIX, XXXIX and XL (a)] A binary information store comprising an array of ferroelectric capacitors is located in a cathode-ray tube, and information is selectively recorded in the capacitors by suitably modulating the cathode beam during scanning operations. In one arrangement, Fig. 1, the array 11 is formed by a stack of multi-condenser units each consisting of a barium titanate layer 16 located between a common metal electrode 17 and a number of small foil electrodes 13 forming separate condensers. Spacing of the multi-condenser units is effected by moulded sheets of insulating material 12 in which are embedded conductors 14 joining the separate electrodes 13 to targets 15. The electrodes 13 and 17 may be applied to the insulating material 12 and titanate layer 16 respectively by spraying, evaporating or printing. The array is located within a cathode-ray tube 10 comprising an electron gun 27, electrostatic vertical and horizontal deflec. tion plates 29, 28 and an earthed secondary-emission collector ring 31. Prior to recording, the array is uniformly polarized in an unspecified manner. When scanning is commenced, the cathode beam is modulated by high-frequency, pulsed high-frequency or D.C. pulses and a binary one is recorded in a condenser by reversal of its polarization. As each layer of multi-condensers is scanned in turn, the associated common electrode 17 is connected to earth by a synchronously-operating rotary switch 23 either directly over switch 25 or through a matching impedance 26. Scanning without modulation is repeated for reading-out, the complement of the stored information being detected by an amplifier 36 with switch 25 open as the unpolarized condensers registering binary zero are reversed in turn. An alternative arrav construction is shown in Fig. 2 in which each multi-condenser unit comprises a ferro-electric layer 46 located between conductive strips 44, 45, the strips being arranged at right-angles to form separate condensers between their intersections. Each unit is separated by an insulating layer 47 and the ends of strips 44 constitute the targets. The ends of strips 45 in the same vertical plane are connected over metallic strips 48 to the rotary switch 23 which operates in synchronism with complete scanning cycles. In this arrangement each condenser along a strip 44 is subjected to the cathode beam in turn in successive scanning cycles. Information storage and read-out operations are otherwise the same as previously described. In a modification, the array comprises a lattice arrangement of conductive strips 68, 69, Fig. 4, which may be deposited on thin insulating strips 66, 67 by coating, vaporizing or printing, the strips being separated by an intermediate ferro-electric layer 70 in the form of a plastic incorporating a ferroelectric substance as a filler. Alternatively the conductive strips may be deposited on the layer 70 or may be individually insulated and interlaced. The conductors are covered by thin paper insulating layers (not shown) which may also incorporate a ferro-electric filler. The completed sheet structure is folded as shown and arranged in the tube with the ends of strips 69 forming the targets. In a further embodiment, Fig. 3, the array comprises a single multicondenser layer 51 formed by a ferro-electric layer 56 having combined targets and condenser electrodes 53 consisting of a large number of uniformly-distributed small metal pieces supplied by spraying, vaporizing or printing. It is suggested that the electrode 53 may be omitted, in which case the surface of the ferro-electric constitutes discrete condenser electrodes. The layer 56 is backed by a common metal electrode 57. It is suggested in the Fig. 1 and 2 arrangements that the rotary switch 23 may be replaced by a light-ray which successively scans resistors 20 made of light-sensitive resistance material, such as lead sulphide or selenium, coated on the side of the array. In this arrangement the conductivity of each resistor 20 is temporarily increased in turn in synchronism with the cathode beam scanning so as to provide sequential ground connections.