The structure of the imaging system of the contact image sensor(CIS) line array camera is different from that of the ordinary camera. The sensors in the camera are generally bound and encapsulated by multiple independent imaging sensors. The problem of camera non-uniformity exists not only in the independent sensor, but also between each group of sensors. Therefore, in order to solve the problem of non-uniformity in the imaging of the line array camera of contact image sensor, especially the problem of non-uniformity mutation near the stitching gap of each imaging unit of the line array camera, an optimized stretch imaging correction method based on the traditional two-point correction method was proposed in this paper. In this method, multiple images with different exposure times are taken as sample sets and the least square method is used to find the best correction black and white template. Experiments show that the relative error offset of the optimized algorithm is smaller than that of the traditional two-point correction method under different exposure time, and the overall image uniformity is improved by about 40% compared with the traditional two-point correction method in the whole response range. Response near stitching gap transition is more uniform, stitching gap near relative to the traditional two-point method NU most about 50% drop in value, and analyzed the optimization calculation of two-point method is easy to convert the FPGA logic implementation. In the high real-time and wide swath image processing architecture of the large area contact linear array camera, the correction effect can be improved only by modifying the black and white templates of the traditional two-point correction method.
Contact image sensor(CIS) line array camera is mainly used in the field of wide-amplitude imaging, which is composed of multiple groups of imaging unit. In practical engineering application, it is found that the response output mutation phenomenon exists between each group of imaging units. Most of the correction method based on plane array camera, without considering the response differences among groups of imaging unit, does not apply to calibration of contact image sensor line array camera. In this paper, the least square method and polynomial fitting method are used to get the optimal coefficient of polynomial, and the non-uniformity correction among among groups of imaging unit and the imaging unit itself are realized. The results show that, compared with the two-point correction algorithm, the proposed algorithm has significantly improved the image contrast and uniformity, and the response of each sensor unit tends to be uniform, the mutation phenomenon is effectively improved, and the output image is close to the correction expectation, which is suitable for the calibration of the wide swath camera imaging of the line array contact image sensors.
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