短焦深空间光学相机的快速寻焦方法

Fast Auto-focus Method for Short Focal Depth Space Imaging System

摘要:

短焦深空间光学系统受发射和工作环境的影响,易出现随机的离焦误差,导致成像质量严重下降。针对传统的寻焦方法速度慢、抗噪声干扰能力差的问题,提出一种可用于遥感图像的离焦深度探测法。该方法在仅通过不同位置获取两幅离焦图像的基础上,通过卷积、反卷积变换,较为准确的估计系统的离焦量。在无噪声和具有11.5dB随机噪声的情况下,17倍焦深范围内,估计离焦量的误差均值分别优于7%和10%。可以使成像探测器快速定位到准焦位置附近,然后在附近精确搜索。实验结果表明,相比于传统对焦深度法,几帧图像较几十帧图像的分析计算,大幅度降低了计算量,提高了寻焦速度。同时,该方法对遥感图像具有更准确的离焦量估计结果和更好的抗噪声能力。

Abstract:

Space optical system with short focal depth is affected by the launch and working environment, and it is prone to random defocus errors, resulting in a serious decline in image quality. To solve the problems that refer to slow speed and poor anti-noise performance in traditional auto-focus method, a auto-focusing method based on depth from defocus that can be used for remote sensing images is proposed. This method only obtains two defocused images from different positions, and through Spatial-Domain Convolution/Deconvolution transform, the defocus of the system can be estimated. In the case of no noise and 11.5dB noise within 17 times the focal depth, the average error of the estimated defocus amount is 7% and 10%, respectively. The imaging detector can be quickly positioned near in-focus position, and then accurately search. The result of experiment shows that, compared with the traditional depth-from-focus method, calculation of several frames of images compared with dozens of frames of images greatly improves the focusing speed. At the same time, this method has more accurate defocus estimation results and better anti-noise ability for remote sensing images.