Key Techniques Of Cooled Long Wave Thermal Infrared Imaging System’s Data Processing

Long wave infrared (LWIR,8~14μm) spectral range, also known as thermal infraredspectral range in physics, covers most of the thermal radiation of objects on the earthat room temperature (300K). Thermal radiation energy of an object is directly relatedto its surface temperature so that we can calculate temperature and emissivity rate ofthe object according to the received radiation signals. Located in the atmosphericwindow, thermal infrared band has excellent anti-interference performance and canwork all day and night. So it is widely used in both civil and military fields.Based on the "863Program" of thermal infrared hyper spectral imager engineeringprototype, this thesis has for the first time introduced into China the320×256HgCdTelong wave infrared focal plane detector MARS VLW RM4, whose spectral responseranges from7.7μm to12μm. Based on a high-rate and low-noise informationacquisition system, a thermal infrared imaging system whose dynamic range is250~330K and NETD is less than50mK is realized. Key techniques of the imagingsystem’s data processing such as non-uniformity correction, blind pixel detection andquantification method are studied.LWIR FPA performs worse than medium and short wave devices in many aspects,including non-uniformity and blind pixel condition. Common used non-uniformityand blind pixel correction algorithms are studied. Response characteristics of theimaging system are analyzed, according to which blind pixels and non-uniformitymethods suitable for the thermal infrared imaging system are studied. Anon-uniformity and blind pixel correction method based on radiation calibration wasput forward, which achieved better than the two-point method, while easy toimplement in project.Including not only target radiation, but also background radiation, detector darkcurrent and other signals, response of thermal infrared imaging system is verysensitive to changes of factors such as the detector operating temperature, imagingsystem body temperature. In order to improve temperature inversion accuracy of theimaging system, accurate quantification the imaging system is needed. This thesisstudied quantification of thermal infrared imaging system and proposed a radiometriccalibration model and temperature inversion method considering body temperature ofthe imaging system.