Night sight with illuminated target cross-wires - controls brightness of LED according to intensity of target image

摘要

A d.c. supply from a battery (1) is fed via an inverter (2) and transformer (3) to a voltage multiplier (4). The multiplier (4) which has a few nano-Amps at a voltage of several kV, is a cascaded circuit of diodes and capacitors. The EHT current flows through the image intensifier tube (5) and a relatively low resistance (6), between the inputs of a differential amplifier (7). The amplifier output is added to a constant current from a fixed source (9) and fed to an LED (8). The light from the LED, which is used to illuminate the crosswires of the night-sight, varies in proportion to the current through, and hence the light input level, of the intensifier tube.