超分辨数字全息显微定量测试方法的研究

Breakthroughs that have been achieved by super-resolution optical imaging technology in the biological field make it an international cutting-edge research focus. Different from the biological field paying more attention to the lateral resolution, the micro/nano-manufacturing field demands nanometer even sub-nanometer level vertical resolution since the properties of the micro-structures are determined by their surface morphology. Hence, optical microscopic interference technology has been widely used, but its lateral resolution is still restrained by the optical diffraction limit..This project intends to start with orderly regulation of the optical transfer function of the digital holographic microscopy. An oblique illumination system will be established to achieve the related model of high frequency information collection and interference phase correction. Then the optimization method of the oblique illumination conditions that are related to the surface structure features of the measured sample will be formed. Exploration should be executed, like phase calibration, compensation and synthesis method of sub-aperture and noise suppression method of digital image plane microscopic measurement etc. Research on key technology needs to be developed, such as optical system design, system calibration, error analysis and so on. The lateral resolution breaking the optical diffraction limit will be achieved, meanwhile the vertical measurement precision will also be guaranteed. That’s to say, super resolution interference quantitative measurement of micrometer scale surface morphology will be achieved. The research results of this project will not only break through the bottleneck, the lateral resolution limitation of the optical microscopic interference technology, but also achieve sub-micrometer level full field of view and high precision measurement of in-plane surface morphology of micro-structures with featured size.

超分辨光学成像技术在生物领域取得的突破成为了国际前沿研究热点。与生物领域对横向分辨力给予更多关注不同，微纳制造领域中微结构的表面形貌决定其性能，对纵向测量分辨力常要求纳米甚至亚纳米量级，为此光学显微干涉技术得到广泛应用，但是其横向分辨力依然受制于光学衍射。.本项目拟从数字全息显微光学传递函数的有序调控出发，建立倾斜照明实现高频信息收集与干涉相位校正的关联模型，形成与被测表面结构特征相关的倾斜照明条件优化方法，探索子孔径相位标定和补偿合成方法、数字像面全息显微测量噪声抑制方法等，开展倾斜照明条件数字全息显微光路设计、系统标定和误差分析等关键技术研究，实现横向分辨力突破光学衍射极限，且同时保证纵向测量的准确度，即实现微尺度表面形貌的超分辨干涉定量测试。项目的研究成果不仅突破了光学显微干涉技术在横向分辨力受限的技术瓶颈，而且能解决亚微米级平面特征尺寸微结构表面形貌全视场、高精度测量的难题。

随着微纳科学技术和相关产业化领域的发展，微器件中功能结构的特征尺寸不断减少，对精密测量的需求也越加迫切。光学干涉测量因具备全视场、高精度、环境兼容性好等优势而得到了广泛关注，但是受光学衍射的限制，水平分辨力和垂直分辨力相差多个数量级。超分辨成像只能获得微结构的平面信息，而对其表面形貌和相关几何量特性的三维精密测量则是研发新型微器件的关键。本项目针对这一需求和当前测量方法存在的不足，以超分辨数字全息显微术为研究重点，从理论上分析了倾斜多角度照明实现超分辨成像的机理，明确了干涉测量中相位校正的难点，并聚焦表面形貌精密测量，开展了子孔径相位合成与校正方法、参考透镜法校正畸变相位方法和数字全息显微相位测量信噪比提升方法等干涉测试方法的研究，研制了两套数字全息显微测试实验装置（可见光和红外），并给出了主要性能指标的评价方法，明确了标准分辨率正负板在反射式和透射式数字全息显微系统的适用性，实验结果表明水平分辨力提升超过20%，且垂直测量分辨力保持在纳米量级，验证了测试方法在突破光学衍射限制的可行性，开展了表面形貌、微位移和微振动等测量的系列应用研究，为后续相关仪器的工程化和产业化奠定了较好的基础。发表论文13篇，其中SCI检索8篇，EI检索3篇，授权发明专利2项，已毕业研究生6名，其中博士生2名。