| 题名 | 高精度三维相位检测及成像技术研究 |
| 作者 | 蒋志龙 |
| 文献子类 | 博士 |
| 导师 | 刘诚 |
| 关键词 | 光学检测 optical inspection 相位恢复 phase recovery 全息成像 holography imaging 强度传输方程 transport-of-intensity equation 三维成像 three dimensional imaging |
| 其他题名 | Research on high-precision based three-dimensional phase detection and imaging technique |
| 英文摘要 | 在高功率激光驱动装置中，装置稳定性的一个关键是光学元件的损伤及缺陷检测。由于强激光束的非线性自聚焦效应，光学元件长期在强激光的辐照下其表面及内部会产生激光损伤，引起光学元件表面膜层被破坏、内部形成丝状裂纹等。更为严重的是，激光损伤中的“相位损伤”还会对强激光束做进一步调制，使得照射在光路下游的光学元件表面的光强分布不均匀，光强较强的区域容易达到光学元件的损伤阈值，从而对光路下游的光学元件造成更为严重的激光损伤。此外，光学元件在加工、运输等环节中也不可避免会在其表面产生划痕等缺陷。因此对光学元件进行损伤或者缺陷的精密检测及修复处理是项非常重要的工作，可以用于指导光学元件进行修复或是替换处理。 光学元件的很多损伤或者缺陷并不改变元件的光强透过率，不能通过观测强度透过率来对它们进行定位和量化检测，通常只能利用侧面照明的暗场成像法，在暗背景下将出现光点的位置认定为存在损伤或者缺陷。暗场成像能够确定损伤或缺陷的大体位置而很难对其大小等其它特性做出定量判断；比较准确的方法是直接测量元件的复振幅透射函数，并从波前相位的改变情况直接测量损伤或缺陷对光束质量的影响。实际上，哈特曼（Shack-Hartmann）波前传感器和干涉仪等都可以测量波前相位变化。但是对于大口径光学元件来说哈特曼传感器的分辨率过低，对于小尺寸的缺陷或者损伤难以分辨，而干涉仪由于体积过大和对环境要求高而不适用于所有的光学元件检测。 在光学元件的损伤或者缺陷检测中，比较理想的是将不同深度位置的损伤结构信息逐层提取出来，即采用层析成像的方法检测光学元件。目前在全息成像领域已经可以实现三维层析成像，主要是基于多波长照明的数字全息三维层析成像，但是这种方法对光源的稳定性要求较高，实验过程相对复杂。若要将全息成像用于光学检测领域，需要在全息三维层析成像理论、实验方案等方面做一系列探究。基于非相干光或者部分相干光照明的强度传输方程（Transport-of-intensity equation，TIE）法，可以通过两幅强度图恢复出全孔径光束的相位分布，同时由于不使用激光照明，因此不会有散斑噪声等影响，可以实现较高的分辨率。TIE方法原用于波前轮廓的定性测量，若将其用于损伤或者缺陷等高分辨率的定量测量，需要在光路安排、数据记录、图像处理及优化、图像重聚焦等方面进行系列研究。本论文基于数字全息和TIE这两种高精度相位检测技术，对光学元件损伤或者缺陷方面的检测问题进行了研究，主要研究内容如下： 1、单波长数字全息三维层析成像。数字全息重构获取的图像其实是由在物体聚焦位置的清晰图像和物体其他位置的模糊图像组成的复合图像，用于光学元件检测时不能辨别出光学元件内部不同区域的损伤或者缺陷信息。为解决这个问题，本论文在多波长照明数字全息三维层析成像的基础上提出了单波长数字全息三维层析成像，利用空间光调制器连续改变照射在样品表面的照明光波前曲率，获取相位连续变化的反射照明光信息，再通过相应的算法实现全息三维层析成像，为光学元件的内部损伤或者缺陷检测提供了方案。 2、提出了合成孔径TIE成像技术，理论上可以利用小数值孔径的光学系统得到高分辨率的图像，提高TIE相位成像的分辨率。对合成孔径TIE成像的实验技术难点进行了分析。指出TIE成像的低频相位包络丢失是所面临的主要困难，为此提出结合GS迭代算法对低频相位包络恢复，从而实际实现相位匹配和孔径合成。所提出的合成孔径TIE成像本质上是一种非相干光合成孔径技术，可以为远程监控和图像遥感等利用自然光成像技术进行真正的合成孔径成像提供了一个可行的技术方案。 3、基于PIE的光场矩成像。光场矩成像（LMI）为TIE在几何形态下的表征。在光学成像与检测中，LMI利用微弱差别的两幅强度图像通过高斯光场能流假设能够重构出不同视角的光场图像，重构的4D光场图像具有高分辨率，将这些不同视角的光场图像合成进动画可以得到立体显示的效果，适用于快速三维成像。PIE领域的三维成像通常在数据采集和数据计算上需要花费大量的时间，本论文成功将LMI拓展用于PIE成像领域，得到了具有动态效果的立体显示，为实现PIE领域的快速三维成像提供了方案。此外，基于4D几何光场传输，本论文探究了将LMI重构的光场用于高分辨率的离焦重构，并在相干照明和非相干照明成像系统下验证了可行性。; In high power laser system, one of the key factor in system’s stability is the damage and defect inspection of optical components. Due to the nonlinear self-focusing effect of intense laser beam, the damage on the surface or in the internal were generated when the optical components is under strong laser irradiation for a long time, leading to the result that the surface membrane layer were destroyed or the filamentous crack in the internal were formed. More seriously, the light beam were nonuniformly illuminated on the components in the downstream with the modulation of ‘the phase damage’, and the strong light irradiation area were easily to achieve the damage threshold of optical component and result in a more severe damage on the optical component. Further more, the defects such as scratches were inevitably occured in the process of manufacture and transportation. Thus, it is important to carry out precise inspection and repairation of optical component which can be used to guide the repair or replace the optical component in high power laser system. The transmittance of a light beam may not changed by the optical component with damages or defects, thus the positioning and quantitative inspection can not be implemented through the observation of transmittance. A dark field imaging method is proposed with side illumination to positioning damages or defects with bright spots on a dark background. Only the approximate position of damages or defects can be found out with this method, while the quantitative information can be hardly measured. An accurate method to inspect an optical component is measuring the complex-amplitude transmittance function, the damages and defects were directly measured by phase variation. Generally, Shack-Hartmann wavefront sensor and interferometer can either be used to measure the variation of wavefront. However, the small sized damages or defects can be hardly distinguished with Shack-Hartmann wavefront sensor when measuring a large apertured optical component, while the large volume and high demands on the environments has limited the interferometer applied to online measurement of optical component. Tomographic imaging is expected to measuring the damage and defect of an optical component with each layer measured separately. In holographic imaging, a multi-wavelength scanning digital holography method is suggested to realize a depth resolved imaging. High requirements on the stability of light source is demanded with this method, and the experimental process is often complicated. To measuring the damage and defect of an optical component with holography, researches on the holographic tomography theory and the experimental scheme will further be explored. Based on the partial coherent or incoherent illumination, the transport-of-intensity equation (TIE) can recover the phase distribution with two intensity images. The TIE method does not depend on the laser illumination, thus no speckle noise will appeared and a high-resolution reconstructed phase image can be obtained with this method. Originally, the TIE method is applied to measuring the profile of wavefront qualitatively. If applied to quantitative measuring the damages or defects with high resolution, researches on the experimental arranging, data recording, image processing and optimization and others will further needed. In this paper, the research is carried out to measuring the damage and defect of an optical component with high-resolution phase measurement technology of digital holography and TIE, and the main contents are summarized as follows: 1.Depth resolved imaging by a single wavelength digital holography. In digital holography, the final reconstruction is an interference of the clear image from the focused part of the object and a blurred image from the unfocused part, thus no clear image of damages or defects at a certain position can be distinguished clearly when measuring an optical component with digital holography. To solve this problem, a new depth resolved imaging by a single wavelength digital holography is proposed in this paper. In this method, a spatial light modulator is used to adjust the wavefront curvature illuminated on the sample and then with corresponding method to realize a depth resolved imaging, providing a solution for the inspection of optical component with damage or defect in the internal. 2.Phase measurement based on TIE. A polynomial fitting method and an iterative method were used to improve the accuracy of phase solved by TIE. In this paper, we exploring to apply the TIE to quantitative measuring the damages or defects of an optical component with high resolution, and researches on the experimental arranging, data recording, image processing and optimization has also been explored. Experiments of optical inspection, measurement of a microlens array, synthetic refocusing form a defocused image were implemented to verify our proposed method. 3.LMI based optical inspection and three dimensional imaging. With two tiny differenced intensity images, LMI can be used to reconstruct the light field images of object with high resolution. With different viewing angles, these high-resolution light field images can be used to stereo display and suitable for fast three-dimensional imaging. Based on 4D light field propagation, we have applied LMI to the light field refocusing and has been verified in the coherent and incoherent illumination. Further more, LMI has successfully applied in the field of PIE with a dynamic stereo imaging, and providing a method for fast three-dimensional imaging in PIE which often suffers from time consuming in data recording and computing. |
| 学科主题 | 光学工程 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30975]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 蒋志龙. 高精度三维相位检测及成像技术研究[D]. |
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