3D Topography Measurement Of Micro-nano Array Based On Light Field Microscopy Photography

With the development of the precision machining technology, micro-nano array is welldeveloped. Because of its excellent optical performance over conventional optical components, micro-nano array is widely used in the imaging, optical communication, precise detection and so on, and plays an irreplaceable role. The three-dimensional(3D) topography of micro-nano array has a very important influence on its optical performance. So, the 3D topography measurement of micro-nano array draws more and more attention. Although the existing measurement methods have their own advantages, their measurement speed is generally slow and the measurement efficiency is low. In order to meet the needs of modern industrial production, we proposed a method for 3D topography measurement of micro-nano array with light field microscope(LFM) in this thesis. The method only need one light field image of micro-nano array by one shot, and then the focal stack is obtained by digital refocusing algorithm. Finally, we obtain the depth map and 3D surface topography of micronano array by depth information extraction algorithm from the focal stack.In this thesis, the research work of the proposed method is carried out in the following aspects:1. Scheme of light field imaging is designed. Through analysis and comparison, we choose the 4D light field function and the plane-to-plane parametric method to express the light field. The LFM based on microlens array is chosen to acquire the light field.2. LFM hardware system is designed. According to the measurement performance parameters, such as the detection range and measurement resolution, parameters of the main components of LFM are analyzed and calculated, and the selection of main components is determined based on market investigation.3. The algorithm for 3D topography measurement by processing light field image is further studied, including digital refocusing and depth information extraction.4. The experimental system of LFM is set up and the experiment is carried out. Based on the above system design, a set of experimental system is set up, and the method of installation and adjustment is further studied. We carry out experiments using the experimental system which has been well-adjusted. The experimental results are compared to the results which is obtained by the NT1100 WYKO optical profiler with measurement accuracy of nanometer scale, and the feasibility of 3D topography measurement for micronano array with LFM is verified.5. Analysis of measurement error and improvement method are proposed. We have a comprehensive and detailed analysis of the experimental measurement error sources and the effect of the errors on the measurement results. Also, we propose some methods to reduce the measurement error. Finally, we discuss how to improve the resolution of the system.The research of this thesis has laid a theoretical and experimental basis for the application of light field microscope in the 3D topography measurement of micro-nano arrays with different periods.