The wavelength of the light radiated by the target is dependent on its temperature, with hotter objects generating light at shorter wavelengths. Thermal detectors have the broadest wavelength response with the constraining factor being the transmission of the material used to seal the sensor and housing.
Pyroelectric detectors are well suited for this application with high temperature stability, excellent signal to noise ratio and low cost. A pyroelectric substance is distinguished by having an internal crystallographic structure that will move slightly in response to a variation in temperature, rearranging the electric charge within the solid generating a voltage which can be measured using a set of electrodes deposited on the faces of the lithium tantalate crystal.
