Thermal imaging system with detector array calibration mode

摘要

A thermal imaging system including an array of photon detectors 14 produces a detector-dependent response to irradiation. Variations in individual detector characteristics produce a fixed pattern noise which degrades the image. The system 10 incorporates a switchable mirror M1 . With the mirror M1 at a calibration positio n P cal , infrared radiation from a light emitting diode 20 is directed on to the detector array 14 . The diode 20 is both a negative and positive luminescent emitter; the flux emitted is current controlled to be equivalent to black body radiation at a range of temperatures both colder and hotter than ambient. Calibration relationships comprising transfer functions relating incident intensity to signal response are derived for each detector. With the mirror M1 at a scene observation position P obs , infrared radiation from a remote scene reaches the detector array 14 . Resulting detector signals are converted into corrected fluxes using individual calibration relationships previously derived and an image with reduced fixed pattern noise is obtained.