Microbolometer

A microbolometer is the uncooled detector that makes practical thermal imaging possible. It is a focal plane array — a grid of microscopic bridges, one per pixel, made of a material whose electrical resistance changes with temperature, typically vanadium oxide or amorphous silicon. Infrared radiation from the scene, focused by a germanium lens, lands on each bridge and warms it slightly; readout electronics measure the resulting resistance change per pixel and map it to brightness, producing the familiar heat picture. Because the array operates at ambient temperature, it needs no cryogenic cooler — the pump that made earlier thermal imagers bulky, power-hungry, and maintenance-heavy.

Uncooled operation is the entire value proposition: thermal cameras became small, rugged, relatively cheap, and instant-on, which is why they now sit in rifle sights, vehicle drivers' viewers, drone gimbals, and helmet monoculars. The trade is sensitivity. Cooled detectors using exotic semiconductors distinguish far smaller temperature differences at longer range and remain the choice for strategic and long-range targeting systems.

Key quality figures are pixel pitch, array format, and noise-equivalent temperature difference — the smallest temperature step the sensor can resolve, with values under 50 millikelvin considered good. Uncooled physics keeps improving, steadily eroding missions that once demanded cooled sensors.