Research On The Imaging Theory And The Key Techniques Of Uncooled Staring Thermal Imager

The uncooled staring infrared technology is one of the high-techs which dual used for both military and civilian. Although it has been made great progress in recent years abroad, there are still two main problems left to be resolved:1. Uncooled staring focal plane detectors are inconvenience for using because of the absence of the complete mathematical model; 2.Because of the restrictions of materials, production processes, as well as diffraction limit of the infrared optical system, temperature resolution and spatial resolution of infrared image are not high. Meanwhile, due to the technology blockade and the late-start research in our country, the theoretical research and the production technology are relatively backward; there are still certain gaps between domestic and abroad in the technology of uncooled staring imaging. Therefore, we have to establish a complete mathematical model of the uncooled staring infrared focal plane array detector based on the theory, come up with a better technology and programs and eventually develop a high-performance thermal imager, which effectively resolve the common problems exist in the uncooled infrared detector, and improve the electronic theory of infrared imaging and the engineering level, and it also contains great significances in speeding up the uncooled infrared imaging technology in China's national defense building and the pace of national economy in various fields of application.In this dissertation, by researching various thermal detection mechanisms of the uncooled staring infrared focal plane array detector and the variety of existing ROIC, I finally established a mathematical model of uncooled staring IRFPA which sets the infrared temperature as the variable, and the FPA analog output voltage of the detector as function value through the derivation of the uncooled FPA theory and the model of ROIC of the ULIS's 320×240 microbolometer. I also proved that microscanning technology played a crucial role in enhancing the spatial resolution of IR images based on the theory of microscanning technology and the simulation results. By studying the major advantages and disadvantages along with the difficulties in microscanning imaging technology between domestic and international programs, I brought up an idea of taking place of the lieu of Archimedes spiral with circular lines and the discrete scanning mode to improve scanning program of the flat-panel elements. Due to the research on the microscanning principle of flat-panel optical components, I established a model of microscanning tilt angle of flat-panel optical components. Under the guidance of the relevant conclusions of uncooled infrared focal plane model, I put forward a low-noise bias voltage and high-precision digital signal processing technology with the concern of the affections on signal integrity. The theory derivation and the simulation results showed that this technology can inhibit the noise of bias voltage and ensure the integrity as well as the stability of the signal. From the characteristic that IR imager has low temperature resolution and high NETD, I raised the IRFPA adaptive digital technology and the adaptive bias voltage technology and IRFPA multi-sampling filtering technique, and proved that this technology really improved the temperature resolution of infrared image through the method of comparing the theoretical calculations and software algorithms such as histogram equalization, meanwhile, the IRFPA multi-sampling filtering technique can reduce random noise of infrared image and infrared images'NETD through the way of multiple sampling the same pixel points under the single-frame condition. Considering the two aspects of either the affection to the microscanning performance or the sensitivity of IR imager, I chose the KIR0472 IR lens manufactured by Kunming North optic-electric co., ascertained the thickness and the best installation angle of Germanium chip from the success rate of production, installation angle and total error brought by the optical system to the microscanning system under the guidance of microscanning theory, scheme as well as the model. Meanwhile, by optimizing the microscanning window size and the shape of microscanning germanium chip, I studied and optimized the design of disc supporting structure of the micro-scanner, and eventually used the slot machine to determine the structure of installation angle of micro-scanner germanium-chip from the consideration of the reduce of the micro-scanner's moment of inertia, conveniently and solidly installed the germanium chip, and stably run the micro-scanner. I put forward a recognition method which suggested that there should be different thin slices with different lengths around the framework's edge of micro-scanners and matched the optical-couple from the convenient and accurate identification of microscanning sub-image starting at different positions. The Faulhaber 3863H024C BLDCM and relevant productions were selected referring to the requirements of the drive motor shaft string momentum and reversing the torque of the micro-scanner. Through the theoretical calculation of the motor's speed up-slow down-uniform microscanning operation mode of microscanning thermal imager was likely to reduce the degree of image rotation, and through the test of the micro-scanner's stability under the driving motor, the rationality of the design of micro-scanner and the choose of driving motor has been established.I did specific verification and assessment about the entire mathematical model, high-performance driving technology, microscanning imaging theory and the realization mentioned in this dissertation. Through the compare of the subjective image and the objective NETD, MRTD, MTF parameters, I concluded that:1) When the black body temperature is 90K above the temperature of the substrate's focal plane, the test figures were anatomized to the theory model; while the temperature went high, the deviation got stronger.2)The low-noise bias voltage and high-precision digital signal processing technology, IRFPA adaptive driving technology, IRFPA multi-sampling filtering technique can increase the temperature resolution of infrared images.3) Microscanning technology can improve the spatial resolution of infrared images. So all the theories and the key techniques will significantly enhance the performance of IR image. At the end of the dissertation, I offered the inadequacies during my research and the prospection of the research in IR imaging.