Wang Wenbin, Zheng Xin, Liu Yuhan, Li Menghan, Zhang Xiaocheng, Qiu Lirong, Zhao Weiqian
Opt Express. 2022 Nov 7;30(23):41804-41820. doi: 10.1364/OE.474700.
A normal transverse laser differential confocal freeform measurement (NTDCFM) method was proposed to address the high-precision measurement difficulty of steep freeform surfaces with large variations in inclination, scattering, and reflectance. Using D-shaped diaphragm technology, the freeform surface under test (FSUT) axial variation transformed into a spot transverse movement on the detection focal plane. Meanwhile, a 2D position sensitive detector (PSD) was used to obtain the normal vector of the sampling points so that the measuring sensor's optical axis could track the FSUT normal direction. The focus tracking method extended the sensor measurement range. Theoretical analysis and experimental results showed that the axial resolution of the NTDCFM was better than 0.5 nm, the direction resolution of the normal vector was 0.1°, the maximum surface inclination could be measured up to 90°, the sensor range was 5 mm, and the measurement repeatability of the FSUT was better than 9 nm. It provides an effective new anti-inclination, anti-scattering, and anti-reflectivity method for accurately measuring steep freeform surfaces.
提出了一种正常横向激光差分共焦自由曲面测量（NTDCFM）方法，以解决倾斜度、散射和反射率变化较大的陡峭自由曲面的高精度测量难题。利用D形光阑技术，将被测自由曲面（FSUT）的轴向变化转化为检测焦平面上光斑的横向移动。同时，使用二维位置敏感探测器（PSD）获取采样点的法向量，使测量传感器的光轴能够跟踪FSUT的法线方向。焦点跟踪方法扩展了传感器的测量范围。理论分析和实验结果表明，NTDCFM的轴向分辨率优于0.5 nm，法向量的方向分辨率为0.1°，最大表面倾斜度可测量至90°，传感器量程为5 mm，FSUT的测量重复性优于9 nm。它为精确测量陡峭自由曲面提供了一种有效的新型抗倾斜、抗散射和抗反射方法。
