基于DMD序列波前探测的大陡度非球面和自由曲面非零位检测技术

High steep aspheres and freeform shapes are playing an increasingly important role in modern optical system because their abilities of correcting optical aberrations and improving system performance with a more simple system structure. However, due to the strong deviations from sphere and complex surface, the metrology of high steep asphere and freeform shapes is still a challenge during the manufacture process. For high accuracy optical manufacture, there’s hardly no a metrology method that can handle the whole process from grinding to polishing, besides from the precise grinding to polishing a gap for metrology exists. In proposed project, a method for the metrology of high steep aspheres and freeform shapes based on DMD wavefront sensor technique is suggested. Comparing with the existing testing methods, e.g. the profilermetry, this is a contactless and full field way and has a higher accuracy; Comparing with conventional wavefront sensor, this is a method with a flexible resolution; Comparing with interferometry, this is a general non-null method with higher dynamic range; In this project, we will focus on the construction of model of optical metrology and optimization methodology, the calibration of system error and compensation method for retrace error, the retrieve method of freeform surface and the alignment technology of freeform specimen, finally the scanning mode of DMD and the diffraction will be studied. We expect to form a general metrology method for high steep aspheres and freeform shapes from the manufacture process of grinding to polishing.

大陡度非球面及自由曲面较多的设计自由度可以有效校正光学像差，达到简化系统结构并提高性能的目的，因此在现代光学系统中扮演着越来越重要的作用。由于大陡度非球面及自由曲面曲率变化大，并且面形复杂，这对其加工过程中的面形检测提出了挑战。对于高精度光学加工来说，几乎没有一种检测手段可以覆盖从铣磨到抛光阶段的检测，并且存在从精磨到抛光阶段对应检测方法的断层。本项目提出一种基于DMD波前传感技术的大陡度非球面及自由曲面检测方法。与轮廓法相比，本方法测量精度更高，是一种非接触式全口径测量方法；与传统波前探测法比，本方法分辨率更大；与干涉测量相比，本方法动态范围更大，是一种通用的非零位测量法；项目将重点研究光学检测模型的建立与优化方法，系统误差的标定方法和回程误差补偿算法，以及自由曲面面形重构技术和位姿调整技术。通过本项目的实施，以期形成一种大陡度非球面及自由曲面从精磨到抛光阶段对应的一种通用检测方法。

光学元件作为光学系统的基本组成单元，其面形特点很大程度上决定了光学系统的性能。非球面的使用极大提升了光学系统的性能。随着科学技术的发展，人们对光学系统的性能要求越来越高。因此，非球面，甚至是自由曲面的光学元件都将在现代光学系统中扮演重要角色。作为光学系统发展的方向，高精度自由曲面元件的制造己经成为世界精密光学制造行业的一个新焦点，其相应的面形检测方法也已成为目前光学检测领域的热点及难点。开展相应自由曲面的检测方法，特别是通用检测方法的研究对自由曲面的精密制造意义重大。我们提出的一种高精度的新型非接触检测方法，即，基于DMD顺序扫描波前探测的自由曲面非零位检测方法。项目首先研究了DMD波前探测的基本原理，设计了相关图像质心提取算法以及波面复原算法，搭建了一套基于DMD波前扫描的非曲面非零位检测系统实验平台，并对一旋转对称非球面和自由曲面（离轴非球面）进行了实验，实验结果表明，本实验系统无需任何补偿，可完成非球面/自由曲面的非零位测量。最终的面形测量结果相对于Zygo零位测量结果和三坐标测量结果，均满足优于0.1um的设计指标。充分验证了本项目基于DMD序列波前扫描测量非球面的可行性！