液晶与显示, 2014, 29 (6): 1057, 网络出版: 2014-09-15
反射式拼接CCD相机非均匀性定标与校正
Non uniformity calibration and correction of reflectorbased mosaic CCD camera
反射式拼接相机 辐射定标 非均匀性校正 渐晕 reflectorbased mosaic camera radiometric calibration non uniformity correction vignetting
摘要
依据实验室辐射定标实验,校正反射式拼接CCD相机由渐晕现象引起的图像非均匀性。通过分析反射式拼接CCD相机成像非均匀性产生机理,明确焦平面辐照度非均匀性是造成相机图像非均匀性的主要原因[分别进行“单片CCD辐照度响应度定标”和“整机均匀性定标”实验[依据定标结果所得出的入射辐射亮度和在该亮度下每个像元实际接收到的辐射照度之间的关系,设计校正算法,得出每个像元的渐晕校正因子,实现渐晕图像非均匀性校正。校正结果显示: 在一定入射辐射亮度范围内,原始积分球定标渐晕图像的非均匀性大于16%,用校正因子校正后,输出图像非均匀性下降到1%以内。经过非均匀性定标和校正的相机用于外场成像也取得了符合工程需要的满意效果。
Abstract
According to the radiometric calibration experiments in laboratory, the reflectorbased mosaic CCD camera’s image nonuniformity caused by vignetting phenomenon was corrected. Firstly, the image ununiformity reasons of reflectorbased mosaic CCD camera are analyzed, and the irradiance deviation received by different CCD pixels in focal plane is the essential reason for images’ nonuniformity. Then, the CCD pixels’ irradiance responsivity calibration experiment and the whole camera’s nonuniformity calibration experiment were carried out in the laboratory, and the relationship between each pixel’s receiving irradiance and camera’s incident radiance was built. Lastly, a correction algorithm is put forward based on the above relationship to calculate CCD pixels’ correction factors, and the correction factors were used to correct the vignetting image. The correct experiment indicates that, within a certain range of incident radiance, the nonuniformity of original calibration images are above 16%, and after correction, the values decreased to 1% or less. Besides, the correction factors were used to correct the images of outdoor experiments and it works very well.
李晓杰, 任建伟, 李宪圣, 孙景旭, 万志, 刘洪兴. 反射式拼接CCD相机非均匀性定标与校正[J]. 液晶与显示, 2014, 29(6): 1057. LI Xiaojie, REN Jianwei, LI Xiangsheng, SUN Jingxun, WAN Zhi, LIU Hongxing. Non uniformity calibration and correction of reflectorbased mosaic CCD camera[J]. Chinese Journal of Liquid Crystals and Displays, 2014, 29(6): 1057.