数字型航空相机的光学系统设计和像质评估

Optical system design and image quality appraisal of the digital aerial camera

当前研制的数字型航空相机的成像原理与传统的胶片型相机不同,它是采用大面阵CCD作为摄像敏感器件,在曝光时间内完成对图像的拍摄。分析了数字型航空相机光学系统设计的注意点,即光学系统选型的问题。并对像质评估的问题进行了探讨,介绍了评价数码相机成像质量好坏的方法——采用调制传递函数(MTF)进行严格的量化评估。同时,对影响光学系统MTF的各个因素进行了详细的分析,并给出了相应的计算公式和计算结果。

The imaging principles between digital aerial cameras designed currently and traditional film cameras are different. The digital camera uses a large area of CCDs as sensitive devices for photographing,and images are photographed by the digital camera during exposal. The paper analyses some notice points for designing optical system of digital aerial camera, namely choosing model of the optical system. Meanwhile, image quality appraisal is discussed. The technique of evaluating quality of the images screened by the digital camera is introduced on the paper. Modulated transfer function （MTF） is adopted to evaluate quality of the images strictly and by quantities. Besides,all factors that have different effects on MTF of the optical system are analysed detailedly, as well as the corresponding calculational formulas and results are presented.