空间遥感相机的自动检焦技术研究

本文介绍应用图像处理法对推扫成像的线阵CCD空间遥感相机进行检焦研究。以推扫方式成像的线阵CCD遥感相机连续拍摄的两幅图像之间没有重复的部分,这给图像清晰度评价函数的选取增加了难度。本文根据光学传递函数理论建立了基于模糊量估计的粗调焦评价函数,通过两幅离焦位置不同的图像就可以估算出离焦量,从而可直接驱动镜头至准焦位置附近。根据功率谱对于自然景物具有一定的不变性原理,建立了基于功率谱的细调焦评价函数,进一步找到了准焦位置。仿真实验表明,这种粗精相结合的检调焦方法既能保证聚焦精度,又能提高聚焦速度。

Study of Autofocusing Technique for Space Remote Sensing Camera

In this paper,the focus measurement of a linear CCD space remote sensing camera in push-broom mode is studied by using a digital image processing method.Because there is no overlap between two images obtained continuously by the linear CCD space remote sensing camera in push-broom mode,it is difficult to select the evaluation function of image definition.According to the optical transfer function theory,the rough focus adjustment evaluation function based on blur estimation is established. From two images at different defocus positions,the defocus can be estimated and hence the lens can be adjusted directly to the focus range.In light of the principle that most natural scenes have certain invariability in power spectra,the fine focus adjustment evaluation function based on power spectrum is established and the accurate focus is further found.The simulation results have shown that this method which combines rough and fine focus adjustment can ensure the focusing accuracy while improving the focusing speed.