大口径光学系统的镜面视宁度检测

Seeing metrology of large aperture mirror of telescope

为了保证大口径光学镜面加工检测的质量和效率,提出了提高大口径光学系统镜面视宁度检测精度的方法。利用电子自准直仪以及平面镜确定波前斜率,推导了基于斜率信息与镜面视宁度之间的关系。为了提高测量精度,突破单台自准直仪精度限制,采用三台自准直仪进行互标校。为了进一步降低误差,使用六自由度平台支撑立方反射体,使精度提高至0.01″量级。另外,结合频响函数的相关理论,估计得到了六自由度平台在检测环境下所引入的误差。最后,引入标准化点源敏感性(PSSn)对结果进行评价,并开展了数值仿真实验。针对模拟镜面视宁度,分别计算两个方向的斜率功率谱以及原始波前功率谱,然后利用之前给出的功率谱与PSSn之间的关系得到了两个方向的PSSn均为0.999。该镜面视宁度测量方法可以在模拟望远镜实际工况下,完成对于系统主镜视宁度的定量预测。

To ensure the quality and efficiency of manufacturing and detecting large aperture optical systems,a method to improve the seeing metrological accuracy was proposed.By determining the wavefront slope with electronic autocollimators and a flat mirror,the relationship between slope information and mirror seeing was deduced.With the purpose to enhance the accuracy and to exceed the limit of only one autocollimator,three autocollimators were used to calibrate each other.To decrease errors,a hexapod platform was adopted to support the cube mirror to improve the accuracy to 0.01″.Moreover,hexapod platform errors induced from the test environment was estimated by the related principle of frequency response function.Finally,the normalized Point Source Sensitivity（PSSn）was deduced to evaluate the testing results.The simulation and experiment were performed.For mirrorseeing,the slope power spectra and original power spectra in two different directions were calculated,and both PSSn in two directions are 0.999 based on the relation between power spectra and PSSn.This method can be used to quantitatively predict the mirror seeing of primary mirrors under actual working conditions of the telescopes.