GB1266034A - - Google Patents

Abstract

1,266,034. Television; cathode-ray tube operating circuits. ENGLISH ELECTRIC VALVE CO. Ltd. 9 June, 1969, No. 29094/69. Headings H4F and H4T. [Also in Division H1] An image pick-up tube arrangement, especially for detecting infra-red images, comprises a tube with a pyro-electric (i.e. photovoltaic) target 2 on which the image 9 is projected through interrupting means 10 adapted to block the light for periods S, Fig. 2, of about 0À1 second; and means are provided for scanning the target at a period A of about 0À02 second near one end of the interruption period with a low velocity beam to produce cathode potential stabilization, and at a period B near the other end of the period with a high velocity beam to produce anode potential stabilization and a uniform potential distribution across the target. Preferably, as shown in Fig. 2, the B period is followed by a second A period as this produces better results, but an output signal is obtained only during the first A period. The ON and OFF periods O and S may be opposite to those shown in Fig. 2 (Fig. 3, not shown). The target 2 may be of tryglycine sulphate, lithium niobate, sodium nitrate or strontium barium niobate, and the output may be derived from a signal plate 5, as in a vidicon, or from a returning beam as in an image orthicon. Operating circuit.-Rotation of the shutter disc is controlled by a master timing circuit 13 which controls a further timing unit 14 adapted to produce the pulses A and B. These are fed to the electron gun 3 as " bright-up " pulses, control the gate 20 for the output signals, and also control the potential source 18 which supplies operating potentials to the tube. For the low velocity beam operation, zero potential may be applied to the cathode and target electrode and a pulse of 300 V. to the field mesh 4; alternatively the cathode may be at zero potential, the field mesh at 300 V., and the target is pulsed down to zero potential. For high velocity beam operation zero potential may be applied to the field mesh and target, and the cathode may be pulsed to -300 V.; alternatively, the cathode may be at zero potential and 300 V. may be supplied to the field mesh and to the target.