功率谱在高分辨率遥感相机检调焦中的应用

Application of image power spectra in the refocusing of high-resolution remote sensing camera

检调焦是高分辨力遥感相机得到高质量图像的关键技术之一。线阵CCD遥感相机在推扫过程中地面景物不断变化,而一般的图像清晰度评价函数只能在相同的图像内容下作比较来判断系统是否合焦。在介绍了遥感相机离焦原因及常用检调焦方法的基础上,用遥感图像验证了图像的功率谱对自然景物具有一定的不变性,分析了将其用于相机检调焦的可行性。实验表明,在系统合焦时,不同图像的功率谱值基本相同;而系统离焦时,功率谱值随着离焦程度的增加而逐渐减小,以此提出了以两幅不同图像功率谱的比值作为CCD遥感相机调焦的评价函数。

Focusing is one of the key technologies of high-resolution remote sensing camera to receive high quality images.In the process of remote sensing camera pushbroom,the contents of arbitrary random scenes are different,the ordinary definition evaluation functions are effective with the same scene to estimate an camera system focused or not,but the image power spectra have invariance from scene to scene.After introducing defocused reasons and common focusing methods of remote sensing cameras,the invariance of power spectrum is proved with remote sensing images,and the feasibility of using it as the basis of the refocusing is analyzed.The experiments indicat that when the image system is focused,the power spectra values are basically same;but when the system is defocused,the values gradually decrease with the defocused degree being enhanced.And finally an evaluate function is proposed,which is the ratio of power spectra values of two different images,to detect the image system focused or not.1