为了确定摆臂式轮廓检测大口径离轴非球面采用不同扫描线数时系统检测误差的敏感性, 文中提出采用蒙特卡洛方法, 建立了仿真分析的模型。对母线条数分别为8~120条的模式进行模拟检测, 对系统噪声引入的面形误差进行Zernike多项式项拟合, 统计分析得母线条数为8~39条时, 系统噪声引入的低阶项检测误差随母线条数的增加而迅速降低; 母线条数为40~70条时, 引入低阶项检测误差降低缓慢; 71~120条时, 引入的低阶项检测误差几乎保持不变。结合实例, 对一口径1 500 mm的离轴非球面反射镜进行实验, 分别采用36条、72条和96条母线进行面形检测。36条母线检测误差相对较大, 检测结果为7.73 μm PV和0.68 μm RMS;72条母线和96条母线检测结果十分接近, 分别为5.755 μm PV, 0.568 μm RMS和 5.612 μm PV, 0.569 μm RMS。验证了仿真分析结果的准确性, 为摆臂式轮廓检测大口径离轴非球面中母线条数的优化选择提供了理论指导。

To analyze test errors induced from system noise of swing arm profilometer (SAP) testing large aperture off-axis aspherics with different scan arcs, based on the Monte Carlo method, the simulation test model was built with different scan patterns from 8 arcs to 120 arcs. To evaluate the test sensitivity, test errors induced from system noise was fitted by Zernike polynomial. The low order test errors were reduced rapidly as scan arcs increased from 8 arcs to 39 arcs, and reduced slowly from 40 arcs to 70 arcs, and kept almost the same from 71 arcs to 120 arcs. As an experiment, a Φ1 500 mm off-axis aspheric mirror was tested by SAP scanning in 36 arcs, 72 arcs and 96 arcs respectively. The surface test error of 36 arcs are much larger with result of 7.73 μm in Peak-Valley (PV) and 0.68 μm in Root-Mean-Square(RMS). The surface test error of 72 arcs and 96 arcs are much close with result of 5.755 μm PV, 0.568 μm RMS and 5.612 μm PV, 0.569 μm RMS respectively. So the simulation results were verified and provided a guide for the scan line selection for SAP testing large off-axis aspherics.