Patent ID: 6278104
Filing Date: 2001-08-21
Classification: H01J

Abstract:
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 receiver element for receiving the shower of secondary emission electrons and producing a visible image replicating the scene with a resulting brightness; 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 an input and opposite output faces of said microchannel plate, and to said receiver, said power supply circuit including a pair of voltage converter circuits each providing a differing non-zero voltage level to said photocathode with respect to the input face of the microchannel plate, one of said pair of voltage converter circuits providing a positive voltage with respect to the microchannel input face and the second of said pair of voltage converter circuits providing a negative voltage with respect to the input face of the microchannel plate, a switching network connecting said photocathode alternatingly to one of said pair of voltage converter circuits and to the other of said pair of voltage converter circuits, the photocathode having a duty cycle being connected to the negative voltage converter and being varied based on a receiver current related to the receiver image brightness, and the microchannel plate voltage being reduced prior to a reduction in the duty cycle of the photocathode, whereby the output brightness of the receiver image is regulated.