基于面源信息的F/39光路自动调焦技术研究

Research of F/39 Optical System Automatic Focusing Technology Based on Surface Target

自动调焦技术在现代天文望远镜中发挥着重要作用。对于大型的空间望远镜,由于发射和在轨工作环境复杂,且常要求在多波段下工作,从而使得在轨自动调焦成为必不可少的一项关键技术。根据空间太阳望远镜[1](SolarSpaceTelescope,SST)F/39主光路在轨工作的调焦需求,在地面调焦实验系统中,以分辨率板为目标源进行了图像边缘法、图像标准差和图像熵等多种调焦判据的实验研究。结果表明,在所选取判据中,基于Sobel与Prewitt算子的图像边缘法只需加减运算,易于硬件实现且半峰值宽度小,波形陡峭,重复检焦精度达到0.06mm,在选取调焦判据中性能最优。

Automatic focusing （AF） technology plays an important role in modem astronomical telescopes. Because of the complicated launch and on-orbital working condition, and working with multiband, AF technology is a key technology for large space telescopes. Based on the focusing requirement of F/39 subsystem of Solar Space Telescope （SST）, a ground focusing experiment system is set up. With a resolving board as target, we examine focusing criterions based on image edge detection, image variance and entropy. The experiment result shows that the criterion based on Sobel arithmetic operator has narrow peak width and repeat AF accuracy of 0.06 mm. In addition, this criterion is easy to be implemented on hardware because it needs only add ＆ subtract operations.