What do the terms Gen 1, Gen 2 and Gen 3 mean?
Russian and American night vision generations differ significantly. A general rule of thumb is to add one generation to a Russian model to find its American equivalent. Thus a Generation 1 Russian night vision scope would be equal to an American Generation II scope. America Gen 1 equipment was originally developed about four decades ago. Gen 1 night vision equipment is built around image intensifier tubes with a very simple configuration. A Gen 1 image tube is vacuum-sealed and consists out of photocathode and a phosphor screen. Gen1 equipment has lower light amplification (gain) and image quality (resolution), especially on the edges of the screen. It typically uses an S-20 photocathode (with photosensitivity of 180-200mA/lm), electrostatic inversion and electron acceleration to achieve gain. Because of higher photosensitivity, Gen I was the first thoroughly passive image intensifier. Gen I is characterized by geometric distortion, performance at low light levels, and blooming. Gen 2
