Huang Yuanhao, Janabi-Sharifi Farrokh, Liu Yusheng, Hung Y Y
State Key Laboratory of CAD&CG, Zhejiang University, Hangzhou, China.
Opt Express. 2011 Jan 17;19(2):606-15. doi: 10.1364/OE.19.000606.
Quantitative phase extraction is a key step in optical measurement. While phase shifting technique is widely employed for static or semi-static phase measurement, it requires several images with known phase shifts at each deformed stage, thus is not suitable for dynamic phase measurement. Fourier transform offer a solution to extract phase information from a single fringe pattern. However, a high frequency spatial carrier which is sometimes not easy to generate is required to solve the phase ambiguity problem. In this paper, we aim to propose an ideal solution for dynamic phase measurement. Four images with known phase shift are captured at the reference stage to analyze the initial phase information. After the object starts continuous deformation, only one image is captured at each deformed stage. A clustering phase extraction method is then applied for deformation phase extraction utilizing the phase clustering effect within a small region. This method works well for speckle image with low and medium fringe density. When the fringe density is high, especially in the case of shearographic fringe, information insufficiency inherent with merely one deformed speckle image often results in poor quality wrapped phase map with plenty of phase residues, which make phase unwrapping a difficult task. In the light of this limitation, a Fourier transform based phase filtering method is proposed for fringe frequency analysis and adaptive filtering, and effectively removes most of the phase residues to reconstruct a high quality wrapped phase map. Several real experiments based on shearography are presented. Comparison between the proposed solution and standard phase evaluation methods is also given. The results demonstrate the effectiveness of the proposed integrated dynamic phase extraction method.
定量相位提取是光学测量中的关键步骤。虽然相移技术广泛应用于静态或半静态相位测量，但它在每个变形阶段都需要几张具有已知相移的图像，因此不适用于动态相位测量。傅里叶变换提供了一种从单个条纹图案中提取相位信息的解决方案。然而，为了解决相位模糊问题，需要一个有时不容易生成的高频空间载波。在本文中，我们旨在提出一种用于动态相位测量的理想解决方案。在参考阶段捕获四张具有已知相移的图像，以分析初始相位信息。在物体开始连续变形后，在每个变形阶段仅捕获一张图像。然后应用聚类相位提取方法，利用小区域内的相位聚类效应来提取变形相位。该方法对于低、中条纹密度的散斑图像效果良好。当条纹密度较高时，特别是在剪切条纹的情况下，仅一张变形散斑图像固有的信息不足常常导致包裹相位图质量较差，存在大量相位残余，这使得相位解缠成为一项艰巨的任务。鉴于此限制，提出了一种基于傅里叶变换的相位滤波方法用于条纹频率分析和自适应滤波，并有效地去除了大部分相位残余，以重建高质量的包裹相位图。给出了基于剪切术的几个实际实验。还给出了所提出的解决方案与标准相位评估方法之间的比较。结果证明了所提出的集成动态相位提取方法的有效性。
