How night vision and image enhancement work
The objective lens (1) of a night vision device collects light (visible and IR) that can’t be seen with the naked eye and focuses it on the image intensifier (7). The power supply (4) for the image-intensifier tube receives power from two “AA” batteries. Inside the image intensifier a photocathode (2) absorbs this light energy and converts it to electrons. These electrons are then drawn toward a phosphor screen (5). In 2nd and 3rd generation intensifiers the electrons first pass through a micro-channel plate (3) that further multiplies them thousands of times. When this highly intensified electron image strikes the phosphor screen (5), it causes the screen to emit visible light. Since the phosphor screen emits this light in exactly the same pattern and contrast as collected by the objective lens, the bright night time image seen through the eyepiece (6) corresponds precisely to the observed scene. These phosphors create the green image on the screen that has come to characterize night vision.
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