基于同步双波长干涉的微观表面抗振动测量方法

Phase-shifting interferometry (PSI) has achieved widespread use in surface topography. The sensitivity of interferometry to vibration impairs the applications to on-machine and in-situ surface measurement, which are required in ultra-precision manufacturing and scientific research. Simultaneous dual-wavelength interferometry (SDWI) is proposed to accommodate the vibration-resistant surface topography and provides the capability of measuring step up to several micrometers in height. In SDWI, dichroic beam splitter is employed to separate interference signal of two adjacent wavelengths and band-pass filter to purify interferograms of individual wavelength. Iteration with nonlinear optimization is used to retrieve surface topography and realize the vibration-resistant capability. The interferograms of two wavelengths are captured simultaneously to enhance the vibration resistance. The optical configuration of SDWI is simple and cost-effective. And SDWI preserves the two main advantages of PSI, high spatial resolution and high phase sensitivity. Combining the numerical simulations and experiments, we will study on high-pureness spectrum division and efficient method of solving nonlinear interference equation. Parameter optimization and resistance test are included as well. The study predicts a reliable and effective solution of interferometry for surface topography in the presence of vibration. And we could seed potential of developing new surface topography instrument as well.

加工制造和科学研究领域对微观表面的现场和原位测量具有强烈的需求。作为表面测量的主要手段之一，移相式干涉测量应用于现场和原位测量的最主要障碍是环境振动。针对此问题，本项目提出了一种抗振动干扰的同步双波长干涉测量的新方法，并可测量数微米高度的突变结构。首先采用二向色分光和带通滤波的方法对相近波长的干涉信号进行光谱分光和波长纯化，同步采集双波长干涉图，然后通过联合非线性优化的迭代计算从分立的双波长干涉图序列中提取表面高度，实现抗振动功能。该方法光路简单、成本低，且可保持移相式干涉的两大优势——高空间分辨率和高位相灵敏度。以数值仿真和实验相结合，研究高纯净度的光谱分光方法和多未知量的非线性方程组高效求解方法，优化系统参数，测试方法的抗振动干扰能力。通过本项目的研究，可望实现振动环境中微观表面的高精度干涉测量，满足现场和原位测量需求，为开发新型表面测量仪器奠定理论和技术基础。

围绕超精密加工与光学加工过程中对表面形貌的高精度测量需求，针对干涉测量面临的垂直测量范围受限、对振动非常敏感等难题，提出了双波长同步干涉测量的方法。针对干涉垂直测量范围小于1/4波长的缺点，采用双波长干涉方法，得到约12μm的合成波长，将测量范围从0.15μm扩展到了3μm，并提出相位融合方法解决了双波长合成中的误差放大问题。针对干涉对振动敏感的问题，利用双波长干涉图光程差相同的特点，提出了联合迭代的相位求解算法，能够消除振动导致的测量误差，并且快速收敛。开发了一台在位测量干涉显微镜原理样机，在0-20Hz频段、0.4μm幅度振动下测量超精密加工表面粗糙度误差小于0.5nm，标准差小于0.6nm，可满足超精密加工中的表面形貌测量需求。本项目发展的一系列方法与技术，能够为超精密加工过程中的表面微观形貌的测量提供过一种潜在的有效解决手段，也可单独为其他技术（如显微成像、数字全息、条纹投影轮廓术，等）提供有意义的参考或直接使用，具备良好的应用前景。