Gated voltage apparatus for high light resolution and bright source protection of image intensifier tube
First Claim
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1. In an image intensifier tube having a photocathode, which draws a current in response to the brightness of input light, the improvement therewith comprising pulsing means, responsive to the magnitude current flowing through said photocathode, for pulsing said photocathode on and off only when said current drawn by said photocathode exceeds a predetermined value, indicative of a clamp level for said tube.
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Abstract
A bright source protection circuit for an image intensifier tube modulates the voltage supplied to the tube'"'"'s photocathode in response to current drawn by the photocathode such that the photocathode is pulsed on and off until the desired photocathode current is achieved.
28 Citations
15 Claims
- 1. In an image intensifier tube having a photocathode, which draws a current in response to the brightness of input light, the improvement therewith comprising pulsing means, responsive to the magnitude current flowing through said photocathode, for pulsing said photocathode on and off only when said current drawn by said photocathode exceeds a predetermined value, indicative of a clamp level for said tube.
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11. In an image intensifier tube having a photocathode which draws a current in response to the brightness of input light and a photocathode voltage at an input terminal of said photocathode, an MCP having its input plane located in proximity of said photocathode, and a first voltage multiplier which provides operating potential to said input terminal of said photocathode, said MCP having a film on said input plane to create a tube clamp voltage, the improvement therewith comprising:
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a resistor, coupled between an output of said first voltage multiplier and said input terminal of said photocathode; and pulse width modulating means, connected to said input terminal of said photocathode, for pulse width modulating said photocathode voltage between a power supply clamp voltage and a secondary voltage when said current drawn by said photocathode crosses a predetermined threshold, said secondary voltage being less than said tube clamp voltage, said power supply clamp voltage being greater than said tube clamp voltage, whereby said pulse width modulating means pulses said photocathode on and off. - View Dependent Claims (12, 13, 14, 15)
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Specification