Infrared (IR) refers to electromagnetic radiation with wavelengths just beyond the visible red end of the light spectrum, invisible to the human eye but detectable by appropriate sensors. In camera systems, infrared is used in two primary ways: near-infrared illumination powers active night vision cameras by flooding a scene with invisible light that the sensor can capture, and far-infrared or thermal imaging cameras detect the heat energy emitted by all objects and use it to form a temperature-based picture.