Image intensifier tube
The heart of traditional night vision. It takes the faint light from stars or moon and amplifies it thousands of times into a visible green or white picture.
What it means
An image intensifier tube is a sealed vacuum device, usually about the size of a shot glass, that sits behind the front lens. Light from the scene hits a coating called the photocathode, which releases electrons. In most modern tubes those electrons pass through a microchannel plate, a thin disk of tiny channels that multiplies them many times over. They then strike a phosphor screen, which glows to make the picture you see through the eyepiece.
The result is direct and analog: no pixels and no screen lag. Tubes are sold inside a housing, such as a monocular, binocular or scope, and a seller often offers one housing with several tube grades at different prices.
What it changes in the field
A good tube shows a scene by starlight that the naked eye sees as black, often with a wide view of about 40 degrees, and lets you walk, watch and identify animals at close to middle ranges. It sees reflected light, not heat, so it shows details thermal misses: eyes, terrain, markings. It can also see an infrared laser.
It needs some light. On a cloudy, moonless night under trees, an IR illuminator helps. Tubes can be harmed by long exposure to bright light while switched on, although modern tubes with autogating handle it better.
What to look for
Tube specs are where night vision buyers spend the most time:
- Figure of merit, resolution and signal-to-noise ratio, and whether those figures are guaranteed minimums or typical values.
- Phosphor color, autogating and film.
- Whether the seller provides a tube data sheet.
Generation labels like Gen 2+ or Gen 3 are a starting point, not a full answer. See tube generations.