IRlicht

IRlicht is a term used in optics to denote infrared light, a portion of the electromagnetic spectrum with wavelengths longer than those of visible red light. In practice, IRlicht encompasses near-infrared (about 700 nm to 2500 nm), mid-infrared (2.5 to 25 μm), and far-infrared (25 to 1000 μm). The term is common in German technical literature and is used in international contexts as infrared light.

It is not visible to the human eye. Its photons have lower energy than visible photons, but can carry thermal information and be absorbed or transmitted by materials differently from visible light. It is emitted by hot objects, semiconductor LEDs, and laser sources, and detected with specialized sensors such as photodiodes, microbolometers, or indium gallium arsenide detectors.

IR imaging devices, infrared cameras, and night-vision systems rely on IRlicht. Some wavelengths penetrate fog, smoke, and certain materials better than visible light, enabling applications in surveillance, industrial inspection, and astronomy. In fiber optics, near-infrared light around 850–1550 nm is commonly used for communications due to low loss in silica fibers.

Common consumer uses include IR remote controls and heating systems. Thermal imaging uses mid- to far-infrared wavelengths to map temperature distributions in engineering, medical, and building contexts.

While low-power IR sources pose minimal hazard, high-power infrared lasers can injure eyes or skin; appropriate safety measures and standards from bodies such as IEC and ITU govern emission limits and labeling.