It is perforated with millions of tiny tunnels, which have specially coated walls. As light strikes the intensifier's photocathode it emits electrons that flow through the tunnels and ricochet off the walls, causing a cascade of additional electrons. These emerge from the plate and strike a phosphor screen to create an image with greatly enhanced brightness. The photocathode and phosphor screen of the I 3 Piece are both 18 millimeters in diameter, and the device has a resolution of at least 51 line pairs per millimeter. In principle, a generation-three image intensifier is quite simple.
Incoming photons strike a photocathode, releasing electrons that bombard a microchannel plate.
As electrons flow through microscopic tunnels etched in this plate they ricochet off the specially coated tunnel walls, releasing a cascade of additional electrons, which emerge to strike a phosphor screen. In addition to the screen's image being thousands of times brighter than the light falling on the photocathode, its glowing green hue closely matches the human eye's peak response. The image becomes slightly soft only at the very edge of the field. An extremely generous eye relief of 38 mm makes it easy and comfortable to view through the I 3 Piece whether or not you wear glasses while observing. Last fall I spent a number of nights under the stars with an I 3 Piece borrowed from the manufacturer specifically for testing.