Generation
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There are 3 main generations of image intensifier tubes, generation 1, 2 and 3 but there also are generation 0 tubes that essentially are first generation tubes but with a different photocathode type.
General propertys of image intensifier tubes
All image intensifiers are vacuum tubes with a photocathode at the front and a phosphor screen at the back.
A brightness gain is generated by accelerating electrons that are knocked out of the photocathode by the photoelectric effect into the phosphor screen, generation 2 and higher tubes also rely on a secondary electron emitter called microchannel plate.
Generation 0
Generation 0 tubes commonly rely on S-1 photocathodes which offer a very low quantum efficieny of under 1% ie aren't very sensitive and therefore rely on active illumination, they don't include a microchannel plate and the image is commonly inverted electrostatically.
Generation 1
Generation 1 tubes rely on multialkali based photocathodes such as S-20 and S-25, also don't have a microchannel plate and the image also usually is inverted electrostatically. They reach significantly higher sensitivitys than generation 0 tubes
Cascade generation 1
Cascade generation 1 tubes essentially are multiple (commonly 3) tubes fiberoptically coupled together to reach higher gain levels
Generation 2
generation 2 tubes also rely on a multialkali based photocathode but rely on a
Generation 3
Filmless Gen 3
Filmless_Gen3_illustration.png
