Source: Night Vision Terminology and How to Choose
http://www.opticsgiant.com/nigvisterand.html
Angle or Field of View
The measure of the angle defining the field visible through the Night Vision system at a distance of 100 yards.
Bright Source or Over-Light Protection
An electronic circuit that turns the power to the Night Vision device down or off when it is exposed to bright light (such as automobile headlights). This protects the image intensifier and extends its life. The device will recover and resume normal operation in 1-2 minutes.
Eyepiece Focus
Used to match your Night Vision scope or binocular to your specific eyesight.
Image Intensifier or Intensifier Tube
The active component in a Night Vision System that amplifies light and presents a usable image.
Infrared (IR) Illuminator
Provides a light source for the system to amplify, yielding enhanced images in very low light conditions such as caves where no ambient light is available for amplification.
Night Vision Binocular
Two complete sets of optics and image intensifiers that are connected together and share a common power supply.
Night Vision Monocular
A Night Vision device for use with one eye.
Objective Lens
Collects all available light and focuses it on the image intensifier. It also provides image magnification. The best objective lenses have low magnification (5x or less), are high-speed (f2 or faster) and are coated for maximum efficiency in the near-infrared bandwidth.
Phosphor Screen
Positioned at the back of the intensifier tube, the green phosphor screen renders a visible night vision image. The human eye is most sensitive to green contrasts. Photocathode
Converts light (photon energy) into electrons (electrical energy) which are then amplified in the intensifier. The objective lens focuses available light on the photoelectric surface of the photocathode, which is excited and passes electrons within the tube.
Resolution
A measure of the ability to render and display a detailed image. Image intensifier resolution remains constant and is expressed as the maximum number of line pairs per millimeter (lp/mm) that can be discerned when a black-and-white stripe pattern is focused on the photocathode.
