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题名	基于迭代算法的快速相位测量技术研究
作者	姚玉东
文献子类	博士
导师	朱健强
关键词	相干衍射成像，相位测量，快速数据采集，光场调制，数字化调制 coherent diffractIve imaging,phase measurement,fast data acquisition, light field modulation, digital modulation
其他题名	Fast phase measurement technology based on iterative algorithm
英文摘要	相位测量技术是光学测量及成像技术领域的重要课题，其在元件检测、波前测量、自适应光学、光束整形、X射线及电子束成像、天文学以及生物医学等领域都具有非常重要的意义。在实际测量过程中，大部分样品都属于相位物体，当光束照射此类样品时反射或透射光振幅分布均匀，而样品内部材料折射率和厚度的不均匀会使光束的相位分布发生变化，所以光场相位往往包含更多的样品结构信息。而人眼或现有的观测设备，如CCD（电荷耦合器件）、感光膜片等，都无法直接对相位进行观测，因此如何对所研究的样品进行相位成像一直是自然科学领域的一个重要研究方向。 相干衍射成像技术（Coherent diffraction imaging，CDI）基于衍射理论和采样定理，通过记录的衍射光斑和某些限制条件，由迭代计算的方式对待测光场（或物体）的振幅和相位同时进行恢复。CDI技术由于不需要参考光束，因此结构简单且对环境稳定性要求低，且作为一种无透镜成像技术，其成像质量不受光学元件质量限制，理论上可以得到衍射极限的分辨率。因此在Ｘ射线成像、光学测量、波前测量、自适应光学、光学相位显微等众多领域具有非常重要的作用。 本论文主要围绕具有快速数据采集的CDI技术展开研究，旨在保留由多次测量带来的高数据冗余量的同时，实现快速或单次数据采集过程。并将提出的方法用于干涉仪和显微镜的改进过程中。 1. 提出了基于数字化调制方式的PIE技术，以提高数据采集速度。PIE技术作为扫描型CDI技术，具有高数据冗余性带来的收敛速度快、精度高等优点，同时也有数据采集时间长的缺点。利用空间光调制器（SLM）对光场的快速调制特性实现PIE技术中照明光和物体的相对位移，从而提高数据采集速度并避免位置误差的影响，适用于工作环境不能够保持稳定或者样品不能被长时间照明的情况。在此基础上，提出将该方法用于平面干涉仪的改进中，利用与传统干涉测量技术完全不同的原理，不需要标准参考平面提供的参考光束即可实现反射镜面型的测量。 2. 提出快速调制照明的相位测量技术，利用SLM对光场的快速调制特性对待测样品的照明光进行快速调制。借鉴Ptychography技术中相互重叠的扫描方式，实现照明光、SLM和待测样品三者的同时恢复，从而从重建的样品图像中去除照明光不均匀性的影响。利用该方法改进了一台商业光学显微镜，实现了定量的显微相位测量。与其他相位显微镜相比，该方法具有结构简单、抗噪声能力强和对光学元件的质量要求低等优点。 3. 提出了编码分束的相位测量技术，该方法采用特殊设计的编码分束板对待测光场进行调制，由探测器记录单幅衍射光斑阵列，通过迭代计算获得待测光束的振幅和相位分布。该方法通过单次曝光记录多幅衍射光斑的方式，在实现单次实时测量的同时还具备了高数据冗余性的特点，因此具有结构简单、收敛速度快、抗噪声干扰能力强等优点。 4. 分析了CDI成像过程中由外界不稳定性导致的照明光部分相干对成像质量的影响，并提出了简单实用的补偿方法。通过理论分析可知，照明光不稳定性导致的部分相干性的影响相当于对记录的衍射光强产生低通滤波，从而使衍射光强的高频信息丢失、对比度下降。在此理论分析的基础上，提出在迭代计算之前对记录的衍射光强进行处理，补偿丢失的高频信息，从而提高重建图像的质量。该方法解决了限制现有CDI技术分辨率的一个重要问题，且由于不需要已知光源的特征，也不需要复杂的数据计算，因此具有易操作性和通用性，尤其在短波长成像领域具有非常重要的意义。; Phase measurement technology is an important topic in the field of optical imaging and measurement, such as the component detection, wavefront measurement, adaptive optics, beam shaping, X-ray and electron beam imaging, astronomy, biomedicine and so on. In the practical measurement, most samples belong to phase objects that have nearly uniform amplitude distribution but varying phase distribution induced by non-uniform refractive index and thickness. So that the phase distribution of the beam tends to contain more structural information than the intensity distribution. And the human eye or other existing observation equipments, such as CCD (Charge-Coupled Device), photosensitive film, etc., can not directly measure the phase distribution, so the phase measurement technology has always been an important field of natural science research. Through the coherent diffraction imaging (CDI) which is based on the diffraction theory and the sampling theorem, the amplitude and phase of the measured light field (or object) can be recovered simultaneously by iteration algorithm through the recorded diffraction intensity or some prior knowledge of the object. CDI technology does not require reference beam, so it has simple structure and low requirement on environmental stability. In addition, as a lensless imaging technology, the reconstruction image quality is not limited by the quality of optical components, and theoretically it can reach the diffraction limited resolution. So it plays a very important role in X-ray imaging, optical measurement, wavefront measurement, adaptive optics, phase microscopy and many other fields. This paper mainly focuses on the CDI technology with fast data acquisition speed, which aims to preserve the high data redundancy introduced by multiple measurements and realize the fast or single data acquisition process. In addition, the proposed method has been used in the modification of the interferometer and the microscope. 1. A modified PIE method based on digital modulation was proposed. As the scanning version of CDI method, the PIE method has high data redundancy and accordingly fast convergence speed and noise immunity ability, however it still suffers from long data acquisition time. Based on the fast modulation ability of spatial light modulator (SLM), the mechanical scanning of the object relative to the illumination beam in conventional ptychographic technique is replaced. So the data collecting speed is considerably raised and the backlash error and the hysteresis of the stages can be avoided. This method can find applications in situations where the sample or the working environment can't keep stable for long time. In addition, this method has been used to modify the commercial planar interferometer. Without changing the basic structure of existing interferometer, a SLM is integrated into the interfermetor to realize the fast modulation on the refrection light beam of the measured mirror. The method does not require a high quality reference beam and has a completely different principle from conventional interferometric techniques. 2. A new CDI method is proposed by displaying a moving pattern on the SLM to form a changing illumination on the sample. Based on the overlapping scanning similar to ptychography method, the complex amplitudes of the illumination field, the SLM and the sample can be simultaneously recovered, so the defects in the illumination beam can be removed from the reconstructed image. A kind of ptychographic phase microscopy is proposed by integrating a SLM into a commercial microscope. In comparison with other kinds of phase microscopes, the developed microscope has advantages of simple structure, high coherent noise immunity and low requirement on the quality of optics. 3. A coded splitting imaging method is proposed to reconstruct the complex amplitude of the transmission function of the specimen with single shot measurement. In this technique, a specially designed coded splitting plate (CSP) is adopted to modulate the measured light field. From the diffraction patterns array recorded on the detector plane, both the modulus and phase distributions of the incident beam can be reconstructed iteratively using the known modulation functions of different orders of the CSP. This proposed method has very simple experimental setup and can realize phase retrieval with single shot measurement. On the other hand, since multiple diffraction patterns recorded with one time of exposure are used to make the reconstruction, this proposed method has high data redundancy and accordingly fast convergence speed and high noise immunity capability. 4. The high frequency vibration of the radiation beam will influence the coherence of the light source to degrade the quality of the reconstruction of the Ptychography Iterative Engine (PIE) by acting as a low-pass filter on the ideal diffraction intensities recorded with stable illumination. It is demonstrated that by modifying the recorded intensities before the conventional iterative computation, the lost high frequency by the vibration of the illumination can be obviously recovered, and then the image quality can be distinctly improved. The proposed compensation method presents an effective way to suppress the influence of the setup instability which is one of the biggest barrier for ptychography to reach the theoretical diffraction-limited resolution. And since no prior knowledge on the radiation source is needed, the proposed method is quite general and simple, and accordingly can find many applications in lots of research fields, especially in imaging with short-wavelength irradiation, such as free electrons or X-ray imaging.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/30992]
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	姚玉东. 基于迭代算法的快速相位测量技术研究[D].

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