Image intensifier with additional power supply

Abstract

An image intensifier with an internal power supply that produces 20,000-25,000 Hz. noise in the output screen voltage is provided with an additional power supply coupled to the output screen through an R-C filter which removes that noise. The additional power supply produces the screen voltage at a current that is a large multiple of the current produced by the output screen voltage of the internal power supply, so that the screen voltage from the additional power supply prevails over the screen voltage from the internal power supply. The additional power supply is regulated by an optical coupler which responds to the light input level to the image intensifier, as follows: at light inputs above about 5.times.10.sup.-5 footcandle, the screen voltage from the additional power supply is less than the usual screen voltage from the internal power supply; at light levels higher than that the screen voltage from the additional power supply increases with decreasing light input and it is higher than the usual screen voltage from the internal power supply throughout the light input range below about 10.sup.-5 footcandle.

Dependencies are inferred from the claim text.