光学偏折子孔径拼接面形检测技术

Sub-aperture stitching deflectometric testing technology for optical surfaces

针对大口径的高斜率动态范围光学元件的测量需求,提出了基于光学偏折技术的子孔径拼接测量方法。利用所搭建的条纹投影光学偏折测量系统,结合子孔径划分拼接方法,对各子孔径分别进行测量,并根据实际测量结果与测量系统模型光线追迹结果的偏差,高精度测得各个子孔径的面形数据,由此对各子孔径进行拼接来实现全口径面形测量。光学偏折测量技术相对干涉法具有很大的测量动态范围和视场,可极大降低所需的子孔径数量,由此大大提高了检测效率。同时提出了针对重叠区域的加权融合算法来实现拼接面形的平滑过渡。为验证所提出方案的可行性,分别进行了仿真分析以及实验验证。对一高斜率反光灯罩进行拼接测量实验,并将拼接测量与全口径测量结果进行对比。结果表明,利用所提出测量方法获得的拼接面形连续光滑,且与全口径测量面形RMS值偏差为0.095 7μm,优于微米量级。该测量具有较高的测量精度和大动态测量范围,并且系统结构简单,为各类复杂光学反射元件提供了一种有效可行的检测方法。

Aiming at the measurement needs of large-aperture optical elements with ultra-large dynamic range,a sub-aperture stitching testing method based on optical deflectometry was proposed.According to the surface feature,the sub-apertures were divided and sequentially measured with the proposed fringe-illumination deflectometric testing system.Based on the slope data measured with actual testing system and ray-tracing result in the system model,the tested surface in each sub-aperture could be reconstructed with high accuracy and be stitched for full-field testing.Compared with the interferometric testing method,the optical deflectometry testing was larger in dynamic range and field of view,which could greatly reduce the number of subapertures required,thus greatly improving the measurement efficiency.Additionally,a weighted-fusion algorithm based on overlapped regions was proposed to obtain the smooth stitching result.To demonstrate the feasibility of the proposed method,both the numerical analysis and experimental verification were carried out.The high accuracy and large dynamic range were validated in the reflective lampshade testing.The result shows that the stitched surface obtained by the proposed method is consistent and smooth,and its surface deviation RMS compared with the full-aperture measurement result is 0.095 7 μm,which is smaller than microns.The proposed method is high in measurement accuracy,large in dynamic range and also simple in system configuration,providing an effective and feasible testing method for various optical elements with complex reflective surfaces.