Image intensification a technique used to increase the intensity (brightness) of the image while maintaining its sharpness. Used particularly in fluoroscopy and viewing directly or indirectly through a television camera and monitor, cineradiography, videotape or split-film device. The image is said to become “intensified” because the output visible light is brighter than the incoming IR light, and this effect directly relates to the difference in passive and active night vision goggles.

Image intensifier tube is a vacuum tube device for increasing the intensity of available light in an optical system to allow use under low light conditions such as at night, to facilitate visual imaging of low-light processes such as fluorescence of materials to X-rays or gamma rays, or for conversion of non-visible light sources such as near-infrared or short wave infrared to visible.

Image intensifier converts visible light from an image so that a dimly lit scene can be viewed by a camera or the naked eye. While many believe the light is “amplified,” it is not. When light strikes a charged photocathode plate, electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the light that strikes the photocathode, and is on a frequency that the human eye can see. This is much like a CRT television, but instead of color guns the photocathode does the emitting.