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The energy focus ability of optics system is defined as the ratio of the energy contained in a pixel to the total energy of the dot diffusion function, which is one of the evaluation indexes of some optical systems. the energy focus ability of the room temperature optical system is usually tested by PSF test equipment. The ground PSF testing equipment works at room temperature and is sensitive to vibration, so it is difficult to carry out stability test in the vacuum and low temperature testing equipment. Therefore, the cryogenic optical system generally uses the point source target imaging method to carry out energy focus ability test. The traditional calculation method starts from the point target image of spot, the energy focus ability is calculated by dividing the gray value of the central pixel of the imaging spot by the sum of the gray value of the surrounding neighborhood pixels. Because the point source target used in the test has a certain size, it will affect the calculation results, so the calculation results are smaller. In addition, the center of central pixel of the detector and the center of the point target dispersion cannot be completely coincided in the actual measurement, and the calculation results are smaller due to the deviation of the center of mass. In this paper, through the establishment of point source target imaging model, the link of error correction is obtained, and a calculation method of the energy focus ability based on sampling correction is designed. This method first calibrates the PSF of the system through the target test image, and then uses the deconvolution algorithm to solve the PSF, and then completes the calculation of the energy focus ability. Because this method eliminates the influence of center offset and target size, it can effectively reduce the calculation error. This algorithm is verified in the room temperature optical system. The results show that compared with the traditional point source method, it is closer to the test results of ground PSF equipment and more accurate.
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