FAQ

There are many considerations when choosing the operating waveband of your thermal infrared camera. The first parameter to consider is what is the estimated temperature range of the objects that you are interested in monitoring.  The Planck emission curve dictates that objects over approximately 150 C will emit in the midwave region and that object closer to room temperature will emit in the longwave region. Consideration must be also given to the spectral requirements of the envisioned application. Many materials can be detected by their infrared spectral signatures via narrowband imaging in both the midwave and longwave regions. Prior knowledge of the spectral signatures of the target material of interest is essential when choosing the spectral range of an infrared imager.

Typically, infrared cameras are calibrated using high-precision blackbody reference sources to implement a non-uniformity correction (NUC) for improved image quality and a radiometric calibration to relate observed detector response (digital counts) to blackbody temperature for a single exposure time. Use of additional exposure times requires the construction of additional calibration data sets.

Telops proprietary permanent radiometric calibration works by considering the electron flux generated by the detector (determined by dividing digital counts by exposure time) as a function of blackbody temperature. The flux generated by the detector is independent of the exposure time and as such, this calibration strategy supports a wide range of operating parameters without the need for recalibration. All Telops high-speed broadband and multispectral imagers are delivered with this permanent calibration fully implemented. We recommend that cameras be factory recalibrated every 2 years.

A thermal infrared camera measures a quantity called radiometric temperature by interpreting the infrared radiation emitted from the surface of objects within the scene. Each object is modeled as a blackbody with a unitary, spectrally flat emissivity profile that emits radiation only according to its temperature. Real objects do not have a unitary emissivity value and in fact, most real materials have spectrally varying emissivity profiles. Additionally, the thermal radiation from objects within the scene entering the camera is modified by the transmission properties of the intervening atmosphere. In order to convert the radiometric temperature measured by an infrared camera to the true thermodynamic temperature of an object, it is necessary to compensate for both the true material emissivity and atmospheric transmission properties.