bolometrisiin

Bolometers, or bolometric detectors, are devices that measure electromagnetic radiation by absorbing energy and converting it into heat. The absorbed power causes a small rise in temperature of a thermally isolated absorber, and a thermometer attached to the absorber converts that temperature change into an electrical signal. Because the fractional temperature rise is tiny, bolometers typically rely on very low heat capacity and operate at cryogenic temperatures to achieve high sensitivity. Their response is governed by the thermal conductance to the heat sink and the heat capacity of the absorbing element.

In practice, the bolometer’s output is proportional to the incident power over a characteristic time constant, which depends on the detector’s materials and design. There are several implementations: resistive bolometers using thin films or semiconductors, and superconducting bolometers such as transition-edge sensors (TES) and related devices. Uncooled bolometers, including microbolometer arrays, operate at or near room temperature and are widely used in thermal imaging where image formation is more important than ultimate spectroscopy.

Applications of bolometers span astronomy, cosmology, and spectroscopy. They are employed to study infrared, submillimeter, and microwave radiation from astronomical sources, as well as X-ray calorimetry in some experiments. In industry and security, uncooled microbolometer cameras provide thermal imaging for monitoring, surveillance, and diagnostics.

The bolometer was developed in the late 19th century, with Samuel P. Langley contributing early infrared measurements. Since then, advances in cryogenics, materials science, and superconductivity have made bolometric detectors among the most sensitive tools for detecting faint radiant energy. The term bolometric describes measurements related to energy-induced temperature changes; in Finnish, bolometriseen is an inflected form of bolometrinen.