Multi-pixel photon counters (MPPCs) have attracted much attention in low-light detection, andhave been widely used in lidar, high-energy particle physics, nuclear physics, astrophysics, nuclear medicine imaging and spectroscopy. Accurate measuring of MPPC key parameters is the prerequisite for judging its performance level. In this paper, the measuring methods of key parameters of MPPCare studied comprehensively, and relatively simple measuring methods are proposed, mainly including the measuring methods of pulse waveform characteristics, Dark Counting Rate (DCR), Photon DetectionEfficiency (PDE), photon number-resolved spectrum, optical crosstalk probability, gain and reverse volt-ampere characteristics of MPPC. A test measuring system is built. The parameters of typical MPPC devices are measured experimentally. The test results are reasonable, and the measured values of various parameters are basically consistent with the nominal values in the MPPCdevice specification.
For digital images described by 8-bit gray level, background prediction can be applied as the correction algorithm to detect and correct the defective pixels existing in the image, the correction can be completed based on FPGA and d imaging devices such as DVI and VGA. In this paper, we applied an improved background prediction that employs median filter as defective pixels prediction, with the median filter results to correct point defective pixels, while square root analysis is employed to correct block ones with improvements of background reset and iteration. Results show that the proposed background prediction can correct the defective pixels of captured images effectively.
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