Circuit for gating an image intensifier

Abstract

The gating circuit includes a low voltage section and a high voltage section with a fast and a slow switch in the high voltage section for providing the gating pulses to the photocathode (PC) of the image intensifier. A high voltage isolated DC/DC power supply referenced to the MCPin terminal of the integral wrap around power supply of the image intensifier provides, to the fast and slow switches, positive and negative potentials referenced to MCPin. The negative potential is sufficient to turn the PC on and the positive potential is sufficient to turn the PC off and to clear burned in PC images. The high voltage isolated power supply provides high voltage isolation between the low voltage section and the reference input and outputs thereof in the high voltage section. A driver included in the high voltage section for driving the fast switch receives operating potentials from a low voltage isolated DC/DC power supply referenced to the high voltage supply. The elements of the driver therefore only experience low voltages thereacross. High speed gating pulses and low speed gating pulses are conveyed between the low voltage section and the high voltage section across respective high and low speed isolation barriers to drive the fast and slow switches, respectively. The high speed barrier comprises a high voltage capacitor and the low speed barrier comprises an opto-isolator. The high speed pulses include narrow, low repetition rate pulses for clearing burned in images from the PC.