Study On Uncooled Infrared Focal Plane Detector Testing And Imaging Technology

The invention and development of the uncooled IRFPA (Infrared focal plane array)is a massive innovation of the infrared technology field. It has the advantages such assmall volume, low power consumption, low cost, and superior reliability. For the brightfuture, so many worldwide developments of the uncooled IRFPA and its applicationtechnologies are under progress.In this dissertation, the testing and verification technologies for uncooled IRFPAhave been described in details. The fully parametric test system for the microbolometerand uncooled IRFPA detectors have been established, a variety of key technologies wasbroken through, and a high-speed, high-precision test bench adapt to the differentspecific uncooled IRFPA detectors was designed and realized. Meanwhile amulti-function, high-performance infrared thermal imaging system based on320×240uncooled IRFPA detectors was designed and realized. The research contents and resultsin this dissertation are summarized as follows:(1) For microbolometer testing techniques: Microbolometer working mechanismwas deeply researched, and the microbolometer optical, thermal and electricalmathematical model was established. Based on the mathematical model, the keyparameters of microbolometer was refined, and the lock-in amplifier (LOCK-IN AMP)technique was applied to test the microbolometer response and noise, Through this way,the technical problems of small signal extraction were overcome. For testing thermalparameters of microbolometer, a method was introduced for thermal conductivity testbased on I-V measurement, and it was found that the effective thermal conductivity andtotal thermal conductivity error can be ignored by reducing the bias current, while thefrequency-conversion lock-in amplifier technology was used to test the thermal timeconstant. Through the comparion between the test results and the simulation results, theaccuracy and validity of the test method can be confirmed.(2) For uncooled IRFPA detector test techniques: A test bench for uncooled IRFPAdetector has been developed, in this paper, the test bench is reported from design toverification, such as the structure of the composition, working principles, board level system design details, the parameter of each module and the key technology solutions,according to the results of a standard detector test, the error could be less than1%. Inthis bench, the bias voltage source module was designed by network feedback controlstructure and the digital potentiometer technology, in order to meet low-noise,high-precision adjustment and wide temperature adaptability requirements. Meanwhilein the acquisition module of the bench, PCIE bus technology and DMA mode is used tosolve the multi-specifications, large-scale, real-time acquisition of high frame rateinfrared image acquisition problem, and the data loss problem during the acquisitionprocess due to the CPU speed limitation was overcome.(3) For uncooled IRFPA imaging techniques: An imaging system based on320×240uncooled IRFPA was designed, the system uses the latest hardware structureof FPGA+ARM, correction parameter calculation and real-time imaging function wereintegrated by the integration design concept. In the nonuniformity correction algorithmpart, an improved neural networks NUC algorithm is introduced. The edge detectiontechnique is applied to the neural network algorithm, to overcome the lack of smearingand target degradation in traditional neural network algorithm. The improved binaryheap algorithm was also applied to calculate the enhancement parameters for theimaging enhancement, it can greatly improves the calculation efficiency, and couldsolve the imaging enhancement distortion problem due to the detector working statechanges. At last, a new infrared image digital detail enhancement(DDE) technologybased on gradient information weight adaptive adjustment was introduced, by the stepof removing noise, calculating image gradient information, correcting this gradientinformation, calculating detail image histogram for image enhancement was applied forimaging detail enhancement. By the test, NETD of the thermal imaging system is98mK.