复合面阵CCD摄影相机的实验室辐射定标

Radiometric calibration of photographic camera with a composite plane array CCD in laboratory

为消除复合面阵CCD摄影相机全像面辐射定标时存在的严重渐晕现象和解决多片CCD之间相对定标目标值选取困难的问题,提出了一种适用于多片CCD的实验室辐射定标方法。该方法对每个像素进行暗信号标定后,修正渐晕区的像素灰度值,通过选取合适的全像面相对定标目标灰度值,最终实现对复合面阵CCD摄影相机的辐射定标。通过分析渐晕区的灰度分布特征,提出了适用于所有曝光时间和辐亮度下的灰度修正方法。分别计算每片CCD灰度值与输入辐亮度之间的多项式拟合系数,选取全局拟合误差最小的一组系数计算对应辐亮度下相对定标目标的灰度值。通过本方法辐射定标后,复合面阵CCD摄影相机的全像面非均匀性由大于20%降至优于2%,绝对定标精度为4.23%。该结果表明本文提出的辐射定标方法适用于多片面阵CCD的辐射定标,定标精度满足航空相机的辐射定标需求。

To eliminate the serious vignetting phenomenon and to solve the difficulty of choosing a relatively positioning target value problems among CCDs during the radiometric calibration of the whole image plane of the photographic camera with a composite plane array CCD,a method for radiometric calibration of multi-CCDs was proposed.After the dark signal calibration on each pixel,the gray value of the pixel in the vignetting area was revised,and by choosing the appropriate relative calibration target gray value of the whole image plane,the radiometric calibration of the photographic camera with a composite plane array CCD was eventually completed.Through analysis of the gray distribution characteristics of vignetting area,the gray correction method for all kinds of explosion time and radiance was proposed.With calculation of fitting coefficient between each CCD gray value and the input radiance respectively,the coefficient with global minimum fitting error was chosen to calculate the relative calibration target gray value corresponding to radiance.After the radiometric calibration using this method,the non-uniformity of the whole image plane of the photographic camera with a composite plane array CCD is reduced from above 20 ％ to better than 2 ％,and the accuracy of the absolute calibration is 4.23％.The result indicates that the proposed calibration method is appropriate for the calibration of composite planes array CCD.The accuracy of the calibration satisfies the radiometric calibration requirement of aerial cameras.