långtIR

LångtIR, or long-wavelength infrared, denotes the portion of the infrared spectrum roughly between 8 and 14 micrometres. In this band, thermal radiation from objects at typical environmental temperatures is strong enough to be detected, allowing passive imaging without external illumination. Using Planck’s law, the peak emission for an object near room temperature (~300 kelvin) lies near 9–10 μm.

Imaging in this region is typically performed with thermal cameras based on cooled detectors such as mercury cadmium telluride (MCT) or on uncooled microbolometer focal plane arrays. Microbolometers respond to temperature-dependent changes in incident radiation and are widely used for portable and affordable LWIR cameras, while cooled detectors offer higher sensitivity and faster response for scientific or industrial applications.

Atmosphere: The 8–14 μm range corresponds to a relatively transparent window in dry air, but absorption bands from water vapor and carbon dioxide reduce transmission under certain conditions and at longer ranges. Weather, humidity, and aerosols can degrade image quality.

Applications: LångtIR imaging is used in security and surveillance, firefighting, building inspection and energy auditing, electrical and mechanical maintenance, and some astronomical instruments. It enables temperature mapping, leak detection, and non-contact heat sensing in settings where visible light imaging is insufficient.

Limitations: Image contrast depends on surface emissivity; reflective or shiny materials may appear anomalous. Spatial resolution is limited by detector size and optics. Smoke, fog, or heavy particulates can obscure scenes; camera performance improves with higher detector quality and appropriate optics.