拼接镜新型粗共相检测方法

Coarse co-phasing detection of segmented mirrors

为了实现拼接镜平移误差的大量程、快速检测,提出了一种利用白光(400～700nm)远场光斑相干性来检测拼接镜piston误差的方法。该方法以两半圆孔间的非相干衍射图案为模板,利用互相关算法求解实际衍射图案与模板图案间的互相关系数,通过设定0.85阈值,实现拼接镜piston误差的粗共相检测。搭建了一套室内拼接镜的主动共相检测实验光路系统,其中拼接镜是由4块对边长为100mm,曲率半径为2 000mm的正六边形球面反射镜组成,利用白光(400～700nm)远场光斑相干性测量拼接主镜各子镜间平移误差的方法进行了理论与仿真分析。利用波前探测器和主动光学技术实现了拼接镜精共焦误差的检测与调节,通过远场光斑相干性和主动光学技术实现了粗共相的检测和调节。实验表明:该方法耗时短、能量利用率高,可实现无限量程、±250nm精度的检测和调节,适合拼接镜的粗共相检测和调节。

To realize a time-efficient and wider range of measurements of piston errors of segmented mirror,a method based on the coherence of the Fraunhofer diffraction pattern of two half circles in visible light was proposed to detect the piston errors of the segmented mirror.In this method,the noncoherent diffraction pattern of the two half circulars was used as a template,and the cross-correlation algorithm was used to calculate the cross-correlation coefficient between the template pattern and the actual diffraction pattern.To achieve coarse co-phasing detection of piston errors of the segmented mirror,the threshold value of the cross correlation coefficient was set as0.85.The proposed method has advantages such as time-efficiency,better energy usage ratio,infinite detection range,and a better measurement accuracy.The method was validated by theoretical,analytical,and numerical simulations.An active optics and co-phasing experimental system of the segmented mirror was built to measure and adjust the piston errors of the segmented mirror.The segmented mirror consists of four hexagonal segments whose edge to edge length is100mm and the curvature radius is2000mm.Initially,to fine co-focus the segmented mirror,a shack-Hartmann sensor and active optics technology were used.Then,the coherence of the Fraunhofer diffraction pattern of the two half circulars in visible light was used to detect the piston errors of the segmented mirror,which can be adjusted using active optics technology.The experimental results show that the detection range is infinite and the measurement accuracy is better than±250nm.Theoretical,analytical,and experimental results demonstrated that the proposed method is suitable for segmented mirror coarse co-phasing measurement and adjustment.