An
image intensifier or
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 in
x-rays or
gamma rays (
x-ray image intensifier), or for conversion of non-visible light sources, such as near-
infrared or short wave infrared to visible. They operate by converting photons of light into electrons, amplifying the electrons (usually with a
microchannel plate), and then converting the amplified electrons back into photons for viewing. They are used in devices such as
night vision goggles.