Claims
- 1. A night vision device having an objective lens receiving light from a scene being viewed and directing this light to an image intensifier tube, said image intensifier tube providing a visible image of the scene being viewed, and an eyepiece lens providing this visible image to a user of the night vision device; said image intensifier tube including a photocathode receiving photons from the scene and releasing photoelectrons in a pattern replicating the scene, a microchannel plate receiving the photoelectrons and providing a shower of secondary emission electrons in a pattern replicating the scene, and a screen receiving the shower of secondary emission electrons and producing a visible image replicating the scene; said night vision device including a source of electrical power at a selected voltage level, and a power supply circuit receiving said electrical power at said selected voltage level to responsively provide electrical power at higher voltage levels to said photocathode, to opposite faces of said microchannel plate, and to said screen, wherein said power supply circuit Her includes means for supplying said higher voltage level to said photocathode substantially as a half-wave rectified sine wave.
- 2. The device of claim 1 wherein said power supply circuit includes means for supplying said half-wave rectified sine wave voltage level to said photocathode during periods when scene light is above a selected level in average intensity and a reduction in the current to the photocathode is needed to compensate.
- 3. The device of claim 2 wherein said power supply circuit includes a clamping circuit having an alternating current source.
- 4. The device of claim 3 wherein said clamping circuit includes a low-voltage source and a high-voltage source, and a diode connected to a connection intermediate of said low-voltage source and said high-voltage source and to said photocathode.
- 5. The device of claim 4 wherein said clamping circuit includes two diodes connected in series to said photocathode and to a connection intermediate of said low-voltage source and said high-voltage source.
- 6. A power supply for delivering a high voltage to the photocathode of a night vision device; said power supply circuit including means for supplying said high voltage to said photocathode substantially as a half-wave rectified sine wave.
- 7. The power supply of claim 6 wherein said power supply circuit includes means for supplying said high voltage to said photocathode substantially as a half-wave rectified sine wave during periods when scene brightness is above a determined level on average and a reduction in the current to the photocathode is needed to compensate.
- 8. The power supply of claim 7 wherein said power supply circuit includes a clamping circuit having an alternating current source.
- 9. The power supply of claim 8 wherein said clamping circuit includes a low-voltage source and a high-voltage source, and a diode connected to a connection intermediate of said low-voltage source and said high voltage source and to said photocathode.
- 10. The power supply of claim 9 wherein said clamping circuit includes two diodes connected in series to said photocathode and to a connection intermediate of said low-voltage source arid said high-voltage source.
- 11. In a night vision device having a photocathode on which light from a scene is directed and a power supply circuit providing voltage and current flow to the photocathode, said photocatwode responsively liberating photoelectron as a function of both light intensity incident upon the photocathode from said scene and voltage level effective upon said photocathode from said power supply circuit, a method of reducing the current delivered to the photocathode when the photocathode is receiving light from the scene which in average intensity is at or above a certain value, said method including the step of applying a time-varying voltage having a voltage wave form which is substantially a rectified half-wave sine wave to the photocathode.
- 12. The method of claim 11 wherein said step of applying a time-varying voltage having a voltage wave form which is substantially a rectified half-wave sine wave to the photocathode is conducted by including in said power supply circuit a pair of voltage sources, of which one of said pair of voltage sources is a low-voltage source and the other of said pair of voltage sources is a high-voltage source.
- 13. The method of claim 12 wherein said step of applying a time-varying voltage having a voltage wave form which is substantially a rectified half-wave sine wave to the photocathode is conducted by connecting said one of said pair of voltage sources and said another of said pair of voltage sources in series, and connecting a diode between a connection intermediate of said pair of series connected voltage sources and said photocathode.
- 14. The method of claim 11 wherein said step of applying a time-varying voltage having a voltage wave form which is substantially a rectified half-wave sine wave to the photocathode is conducted by limiting filtering capacitance effective between said photocathode and a microchannel plate of said night vision device to substantially only that inherent capacitance presented by the juxtaposed photocathode and microchannel plate themselves, and substantially without any added separate filter capacitor.
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to the following other applications:
The entire content of each of these related applications is incorporated herein by reference.
US Referenced Citations (4)