A method of autofocus for remote sensing camera

Because of the flight of the remote sensing camera in the orbit, the successive images of the scenes captured by the remote sensing camera are different at any time. So it is difficult for the camera to implement autofocus. In this paper, an auto-focusing method in the remote sensing camera is proposed based on successive two images captured in a short time which have an overlapped region where scenes are same. Firstly, the space camera moving in the orbit, shoots one picture every time the camera adjusts its focus, and then we can obtain a sequence of images after several times, from which the displacement and the overlapped regions of two adjacent images can be calculated by image registration algorithm. We can take every two adjacent images as a group. Therefore, every image has a value of focusing accuracy by performing a sharpness evaluation function on the overlapped region of each image. Finally, according to the transfer characteristic of evaluation values of every two partly overlapped images, we can unify the evaluation values in a same merit evaluation system. And then find the maximum value of image evaluation values in a same evaluation system, so we can find the accurate focus. Simulation experiment shows that this method works pretty well in auto focusing when relative motion between the camera and the object is existed. This method can be used in aerial camera and remote sensing camera.