针对声光可调谐滤光器(AOTF)多光谱成像系统中存在色差, 使得不同波长下成像清晰所需焦距有所差异, 即使在固定波长下, 由于横向(衍射方向)光谱展宽, 出现横线清楚竖线模糊的现象, 本文对AOTF中的色差做了具体分析, 指出了成像模糊的原因。 根据AOTF多光谱成像系统成像特点, 进一步提出了一种改进的SSIM算法作为图像的清晰度评价函数, 原算法中目标为两幅图像(一幅为参考图像, 一幅为待测图像), 而此算法中将目标设定为一幅图像中的相邻行进行相似度分析, 明暗变化边缘相似度小说明对比度大, 从而图像较为清晰。 使用以此算法为核心的自动聚焦对AOTF多光谱成像系统中由色差引起的图像质量进行补偿, 计算量小, 速度快。 通过实验验证了此补偿策略的可行性和实用性, 结果表明此策略能够有效解决AOTF多光谱成像系统中因色差引起的图像模糊问题, 具有重要的应用价值。

In view of the existing chromatism in the AOTF multispectral imaging system causes different wavelength imaging clarity under different focal length , even under the fixed wavelength, due to the horizontal direction (diffraction) spectral broadening, which leads to clear horizontal lines and blurring vertical lines. This paper made a concrete analysis of the chromatism of AOTF, pointing out the causes of imaging blurring. According to the imaging characteristics of AOTF multispectral imaging system, this paper proposed an improved algorithm based on SSIM, which can be used to evaluate the image sharpness. The target of the original algorithm was two images (one as a reference image, the other one as the test image), while the algorithm proposed in this paper made similarity analysis between the adjacent lines in one target image, small similarity in change edges declares great contrast, thus the image is clearer. The image quality caused by chromatism in the AOTF multispectral imaging system can be compensated by automatic focusing system, which mainly based on this algorithm. It has small calculated amount and fast speed. The feasibility and practicability of the compensation strategy were verified through experiments. The results show that this strategy can effectively solve the image blurring caused by chromatism in the AOTF multispectral imaging system, which has an important application value.