Research on optical three-dimensional profilometry using Dammann grating

微光学是研究特征尺寸在微米量级上的光学功能器件、光学表面微结构，以及集成微光学系统的现代光学学科。作为微光学重要分支的二元光学基于光波衍射理论，利用计算机辅助设计，兼容超大规模集成电路制作工艺，实现性能卓越的功能器件。达曼光栅作为典型的二元光学元件，具有效率高、体积小、易于复制的优点。达曼光栅可以有效提高能量利用率，提供高质量的结构光源。在光学三维测量领域，使用达曼光栅可以产生新的三维测量技术。本论文旨在研究达曼光栅元件在光学三维测量领域的应用，以及微光学光栅在三维内窥测量领域的应用。主要内容如下： 1.研究了基于达曼光栅的傅里叶变换轮廓术的条纹产生机制以及三维测量系统结构。提出了基于达曼光栅和柱面镜的投影条纹产生方法，并利用该结构提出了新型的三维形貌测量系统。利用达曼光栅的衍射特性，结合柱面镜的扩展能力，产生的投影条纹具有高亮度、高对比度和高线条压缩比的优点。这种条纹产生机制在一定程度上克服了物体表面反射散射严重、对比度低和条纹混叠带来的测量误差和错误，对于重构表面结构复杂的微小物体特别合适。独立完成了测量系统的软件构架和代码实现，编写了应用程序，完成了系统硬件设计，搭建了实验原型装置，实现了低对比度物体表面三维形貌的准确重构。该系统具有效率高、结构简单和测量速度快的特点。 2.研究了基于振幅光栅投影的三维内窥测量方法和装置。提出了基于光纤导像束和微小透镜组的两种图像传递方案。重点研究了基于振幅型光栅投影、微透镜组导像的三维内窥测量方案。完成了系统设计、软件编写、振幅光栅参数优化、微小透镜组的设计参数优化和测量系统的线性标定，并搭建了相应的实验原型。对实验物体表面和人体组织表面进行了准确的三维重构，证明了该方案的有效性。该三维内窥成像系统具有结构简单、测量速度快的特点。经过优化的光栅参数和设计尺寸，可以满足内窥测量的要求，为三维内窥测量研究提供了重要的方法和装置，有望在医学成像和生物形貌测量领域获得应用。Micro-optics is a modern science that investigates micro-scale optical elements, micro-scale surface structures, and micro-scale integrated optical systems. As a major branch of micro-optics, using binary-optics techniques, we can fabricate functional devices of high performance through computer-aided design based on diffractive principles with LSI technology. Dammann grating is a typical binary-optics element, which has the advantages of high efficiency, small size, and easy fabrication. Dammann grating can provide structured illumination of high quality with high energy efficiency. Employing Dammann grating in three-dimensional (3D) profilometry is a new measuring technique. This thesis concentrates on the applications of Dammann grating in optical 3D imaging field, and the applications of micro-optical gratings in miniaturized 3D endoscopy. The main contents are as follows: 1.Research on fringe-generation technique and 3D reconstruction system in Fourier transform profilometry (FTP) with the employment of Dammann grating. We proposed a novel fringe-generation method using Dammann grating and cylinder lens, and furthermore reported a new 3D profilometry. Based on the diffractive properties of Dammann grating and the capacity of cylinder lens, the produced projection fringe pattern is of high brightness, high contrast and compression ratios. The proposed fringe generator solves the problems of low surface contrast ratio and fringe overlapping due to surface reflection and scattering effects. It would be of high interest in 3D reconstruction of a small-sized object with complex surface geometry. I have accomplished the profiling algorithm and hardware system, coded the software package, built up the experimental prototype, and realized the 3D reconstructions of experimental objects. The proposed 3D profilometry using Dammann grating has the advantages of high effieciency, simple system frame, and high 3D reconstruction speed. 2.Research on miniaturized 3D endoscopic imaging system with the employment of an amplitude grating. We proposed two image-transferring methods using fiber bundle and micro-lens arrays in the endoscope, respectively. An investigation was carried out to study the endoscopy using an amplitude grating and micro-lens. I have accomplished the endoscopic architecture, coded the software package, optimized the design of the amplitude grating and micro-lens, calibrated the height coordinate, and built up the experimental prototype. The experiments on experimental objects and human tissues verified the effectiveness of this technical approach. The proposed 3D imaging endoscope has the advantages of simple architecture and fast reconstruction speed. With optimized grating and micro-lens arrays, it provides a new tool for 3D endoscopic measurement, and has potential applications in clinical and biomedical researches