Image Intensifier

Could we cue the MIT professor again, please? Here's the explanation of how an image intensifier works:

• An image, ultraviolet, visible light, or near infrared, is projected onto the transparent window of a vacuum tube.

• The vacuum side of this window carries a sensitive layer called the photocathode. Light radiation causes the emission of electrons from the photocathode into the vacuum which are then accelerated by an applied DC voltage towards a luminescent screen (phosphor screen) situated opposite the photocathode.

• The screen's phosphor in turn converts high energy electrons back to light (photons), which corresponds to the distribution of the input image radiation but with a flux amplified many times.