Patent GB-1262919-A (GB)
Title: An image storage cathode ray tube and visual monitor tube system
IPC: G09G5/39
Filed: 1969-11-20
Abstract: 1,262,919. Cathode-ray tube operating circuits. TEKTRONIX Inc. 20 Nov., 1969 [6 Dec., 1968], No. 56756/69. Heading H4T. [Also in Division H1] The operation of a direct view image storage cathode-ray tube 10 (Fig. 1) is switched between a store mode in which information is written on the storage electrode 14 by an electron beam gun 12 and a non-store mode in which the beam from gun 12 is empolyed to read-out the stored information, the potential of the back-plate electrode 34 of the target relative to a floodgun 26 being altered by switch 52 from a relatively high value, operative during the storemode and sufficient to cause storage, to a relatively low value, operative during the non- store mode and insufficient to cause storage but sufficient to produce a controlled persistence of the stored information for the duration of the read-out operation (i.e. the non-store mode). Thus, the stored information is effectively erased during alternate modes of operation and "blinking" of the displayed information when the latter changes is prevented so that the display on a monitor tube 118 accurately follows these changes. In the operation of the system ramp waveforms producing a line raster and a suitable beam bias for reading operation (non-store mode) are supplied to the tube via switches 62, 64, 66 which are changed over by a switch-driver 72 during X-deflection retrace intervals to receive alternate X, Y and Z inputs from channels 86, 88, 100 which supply the information for storage the switch 52 being simultaneously changed from NON STORE to STORE. The signals produced during the reading operation are then supplied via amplifier 54 in which they are combined with synch. pulses to a RF generator and modulator 116 to produce a conventional T.V. type waveform for display by the monitor 118 which may be a conventional T.V. receiver. Alternatively the video output of amplifier 54 together with the X and Y ramps from generators 74, 76 may be utilized to control a display tube. During the actual operation of switches 62, 64, 66 a short blanking pulse is supplied from generator 114 to amplifier 40 and complete erasure of the stored information may be produced by a push-button (60) operated erase generator 58 which supplies a positive pulse followed by a negative pulse. The flood gun 26 comprises a plurality of parallel connected guns and instead of using a single gun 12 for reading and writing separate guns may be employed. Figs. 2 and 3 show the construction of the storage target which includes the transparent glass face plate 30 the interior surface of which is etched to provide a plurality of spaced protrusions 32. The whole of this surface including the protrusions is covered by a transparent coating of tin oxide 34 and a layer of phosphor 35 is deposited on the surface of the glass plate around the coated protrusions to provide both the storage dielectric and a fluorescent screen visible through the coating 34 and the glass plate 30. The portion of the coating 34 extending above the phosphor on the protrusions functions as the major collector of secondary electrons.