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Introduction to Microbolometers
Calibir GXM640 IR Camera User's Manual
The IR absorbing material is thermally isolated by suspending it within a vacuum,
however it is still sensitive to changes in the camera body temperature.
When the camera operating temperature changes, the Calibir GXM640 shutterless
operation automatically compensates for the corresponding responsivity changes in the
microbolometer pixel array (non-uniformity correction (NUC)). The NUC is factory
calibrated across the working temperature range of the camera in free-running mode at
30fps.
However, if the thermo-mechanical environment of the camera changes from the factory
calibration environment (for example, one side is exposed to heat or surface mounting
fixed pattern noise (FPN) correction
these differences. If the camera temperature changes, or improved image quality is
required, FPN correction can be recalculated to ensure optimal response.
Emissivity
Emissivity is a measure of a material’s ability to emit infrared energy. It is measured on
a scale from 0.00 to 1.00. Typically, the closer a material’s emissivity rating is to 1.00
(that is. 100%), the more that material tends to absorb reflected or ambient infrared
energy and emit only its own infrared radiation. Most organic materials (for example,
plants and animals), have an emissivity rating of 0.95.
Substances with very low emissivity ratings, like highly polished metals, tend to be very
reflective of ambient infrared energy and less effective at emitting their own
electromagnetic waves. For example, an object with an emissivity of 0.5, half the image
pixel value is the result of the ambient temperature of the surrounding environment
being reflected. Therefore an understanding of target environments containing objects
with emissivities of less than 0.7 is required to accurately analyze image scenes.
