用于大口径非球面检测的零位补偿拼接干涉测量技术研究

Precise measurement of large optical aspheric surfaces faces great challenge. A new null sub-aperture stitching interferometry for large aspheric surfaces based on dynamic aspheric wavefront generation with spatial light modulator is put forward herein. The real-time measurement of sub-aperture was realized by using a SLM with holographic dynamic compensation. Then, the binocular vision positioning system is utilized to get the pose transformation parameters. At last, the full aperture results with high accuracy could be acquired by null stitching technique. Combined with the dynamic compensation technology and sub-aperture stitching technology, both the limitation of the measurable aperture of the conventional null method and the limitation of the measurable asphericity of sub-aperture in the sub-aperture stitching method can be overcome. The high accuracy aspheric wavefront reconstruction method of SLM is studied and the null testing results of sub-apertures can be obtained. In order to get a high precision result, a stitching algorithm with stepwise regression is studied. What’s more, the error propagation law of measurement system is studied and the final results are corrected. The method we proposed provides a basic principle for the exploration of the new 3D sensing methods, which not only can be used for measuring large aspheric surfaces, can also provide a promising method for other complicated surfaces(free form surfaces etc.).

大口径非球面镜的高精度检测在先进光学制造领域存在着巨大的挑战。本项目提出一种基于空间光调制器（SLM）实时构建非球面波前的大口径非球面零位子孔径拼接（SAS）干涉测量新技术，用SLM对被测非球面进行全息动态补偿，实现子孔径的实时零位测量；采用双目视觉定位技术获取子孔径的位姿参数，最后通过零位拼接实现大口径非球面的高精度检测。结合动态补偿技术与子孔径拼接技术，突破传统补偿法的口径受限与子孔径拼接法中子孔径可测非球面度受限的问题。主要研究SLM的高精度非球面波前重建方法，获取高精度的单次零位测量数据；研究基于逐步回归的子孔径拼接方法，将所有子孔径零位测量数据进行无缝拼接，得到全口径测量结果；最后研究测量系统误差传递规律，对测量误差进行分析和校正，以实现高精度检测。提出的方法为探索新型三维传感方法提供基础原理，不仅可用于大口径非球面镜的高精度检测，也能为其他复杂面型（自由曲面等）提供检测手段。

传统的非零位拼接测量技术所需子孔径数目较多，导致测量效率较低，拼接误差累积也会逐步放大。本项目提出一种基于空间光调制器（SLM）实时构建非球面波前的大口径非球面零位子孔径拼接（SAS）干涉测量新技术，结合动态补偿技术与子孔径拼接技术，突破传统补偿法的口径受限与子孔径拼接法中子孔径可测非球面度受限的问题，能够实现以最少的子孔径数目完成大口径非球面的拼接干涉测量。重点研究基于SLM的动态波前重建方法，提出基于液晶光栅自干涉的SLM相位响应非线性标定与校准方法，探究入射光角度对SLM相位调制特性的影响，揭示了SLM像素结构参数对波前重建精度的影响规律。研究了干涉条纹高效高精度相位恢复方法，提出一种结合施密特正交化和最小二乘的两帧干涉条纹的高精度相位解调方法以及一种基于统计平均的两帧条纹快速相位解调算法，相位解调的准确性和效率大大提高。提出一系列基于光强传输方程和深度学习的快速鲁棒相位展开算法，以提高相位展开的效率和噪声鲁棒性。完成干涉仪测试臂的光学设计与加工，搭建了SLM位于参考臂的泰曼格林型干涉系统，初步实现了小偏离量非球面的自适应零位干涉测量，为大偏离非球面的零位拼接干涉检测奠定了基础。