| There has being widespread interest in the development of the Uncooled Infrared Focal Plane Array (UFPA) because that the system based on it has the advantages of lightweight, compact volume, quick preheat, low power consumption and cost. Therefore UFPA is one of the main directions of Infrared Focal Plane Array (IRFPA), and has good prospects in military and civil applications. The uncooled microbolometer (UMB), one kind of UFPAs, was developed rapidly, and many compelling achievements have been achived. As a natural result of the manufacturing process and material, the nonuniformity (NU) of UMB array is large (far more than 10%). Nonuniformity of output signal requires interface circuit with wider dynamic range (DR), and deteriorates the imaging quality. At present, nonuniformity correction (NUC) technology must be implemented to improve the uniformity of array. But the traditional two-point (gain and offset) correction is sensitive to the change of substrate temperature. Even after correction, the nonuniformity increase sharply as the sink temperature changes. Therefore a thermoelectric cooler (TEC) and temperature control circuit with high precision are used to stabilize the chip temperature within a small range (0.005~0.025K). Supported by NSFC (No.60377036), this paper researched a kind of nonuniformity correction circuit to work at wider substrate temperature range, getting rid of complicated temperature stabilization device, and benefitting miniaturization. By computer simulation and electrical CAD technology, the author studied the nonuniformity of UMB and its readout circuit with NUC. Firstly, this paper described and analyzed the detecting mechanism, structure, parameters and merit of figure of UMB cell. Theoretic analysis and computer simulation were thoroughly implemented on the model of microbolometer. Then this dissertation emphasized on the research of the nonuniformity and its correction technology of UMB. The definition and origin of nonuniformity and temporal noise are introduced, and impact of parameters'nonuniformity of UMB cell on the array output was simulated. Next, the readout configuration and signal converter circuit is studied. The paper investigated the operational principle of readout circuit of Capacitive Transimpendance Amplifier (CTIA), and deduced the responsivity of UMB read out by CTIA. At last, the figure of merits, such as Noise Equivalent Power (NEP), Noise Equivalent Temperature Difference (NETD) and detectivity D*, and nonuniformity are analyzed. After the simulation of fixed coefficient two-point correction procedure, the influence of substrate temperature on the output and nonunioformity correction was explained in detail. Based on the linear model of detector, a new correction method was proposed to wider the operational uniform substrate temperature by making all the pixels'responsivity ratios both for light and substrate temperature equal. The simulation result seems that this method can work on a uniform temperature of substrate within about 4 Kelvin degree. At last a readout scheme based on the new nonuniformity correction method is put forward. The static current is reduced by dummy pixel. DAC transfers correction coefficient data to the gate of MOS transistor, to control bias current. Multi-column shared CTIA and DAC make trade-off between the complexity of circuit and output frame frequency. A PSPICE model of microbolometer cell was constructed based on the thermal-electrical analogy. The readout circuit with multi-column shared CTIA and DAC was simulated in PSPICE.
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