What is a Bolometer?

Bolometers are detectors used to measure incident Infrared radiation. They are very sensitive to thermal radiation and are predominantly used in the infrared spectrum between 10 to 5000µm (30THz to 60GHz). The detector element is an extremely sensitive thermistor that is cooled to LHe temperatures in order to decrease the thermal background. Any thermal radiation that impinges upon the detector will cause a temperature change. This will cause a change in resistance which is amplified and measured as a voltage difference.

Because bolometers measure a change in temperature, the incident radiation must be modulated. This allows the bolometer to excite and relax, thus a measurement of the change in resistance is made that corresponds to the energy of the incident radiation. The speed at which the bolometer reacts to this temperature change is dependent upon several factors that can be altered, if desired, at the time the system is ordered.

Basic System

Click on drawing to enlargeAll composite silicon bolometer systems are housed in our HDL-5 model, liquid helium dewar with a liquid nitrogen cooled radiation shield. Standard hold times are greater than 20 hours between fills for 4.2K systems and 10 hours for our 1.6K models. The detector comes with an IR light collecting cone assembly, vacuum-sealed wedged window, field of view baffling, and low noise electronics.

The bolometer system is then outfitted with a single cut-on IR filter or a cold, manually operated, 2 or 3 position filter wheel. We offer a selection of far IR cut-on long pass filters that range from 10 to 285µm.

If your application requires longer hold times, increased work height, dual detectors, or more filter positions are required, please let us know. We are committed to building a custom designed system to meet your individual needs. Special requests for custom designs are always welcome.