Nightvision

Night vision refers to the ability to perceive the environment in low-light conditions. In common use, it denotes devices that enhance faint light or detect infrared radiation to produce an interpretable image. Night vision technologies fall mainly into two families: image intensification devices and thermal imaging systems. Some systems combine both or use digital processing to improve visibility.

Image intensification devices amplify existing light. An objective lens collects photons, which strike a photocathode and release electrons. The electrons are multiplied by a microchannel plate and then strike a phosphor screen to create a visible image. The typical output uses a green phosphor. Performance is categorized by generations; Gen I is older and slower with more distortion, while Gen II and Gen III use more efficient photocathodes and higher gain, producing clearer images with less noise. These devices require at least some ambient light or infrared illumination and can be degraded by bright lights.

Thermal imaging detects infrared radiation emitted by objects as heat, rather than amplifying light. Detectors form images from temperature differences across a scene. This type of night vision works in total darkness and can function through smoke, fog, and light rain, but resolution and contrast depend on detector material, cooling, and scene temperature variation. Uncooled microbolometer cameras are common and affordable, while cooled MWIR (3–5 μm) and LWIR (8–14 μm) systems offer higher sensitivity for specialized applications.

Applications include military and law enforcement, aviation, search and rescue, wildlife observation, and navigation. Limitations include restricted spatial resolution, sensitivity to environmental conditions, power needs, and, in some regions, regulatory restrictions on use and possession.