
chi20181130上海光机所刘诚557459In high power laser system, the quality of laser beam is the key role of inertial confinement fusion, however, the high power laser system contains a lot of optical elements with large diameter, the scale of light path is huge and complicated, the irregularity of excitation beam, nonuniformity of optical device material, the scratches, damage and contamination on the surface of optical elements will affect the quality and amplitude distribution of wavefront in the process of optical transmission, and distort the wavefront of laser beam, degrading the result of experiment. Monitoring the quality of laser beam wavefront in real time and making the compensation adjustment accordingly will improve the output energy, peak power and size of focus point substantially, thus the beam quality diagnostic system has great significance to keep the high power laser system running smoothly and improve its performance. At present the common optical wavefront measurement device in high power laser field includes the interferometers and Hartmann wavefront sensor, both of them have relatively high measurement accuracy and technical stability, they can solve most of the pratical measurement problems in laser driver field, but they also have obvious deficiency. The interferometers occupies large spatial volume and needs a regular reference beam, the interferometers demands high stability of environment, and is not suitable in online diagnostics of pulse beams in high power laser system. The Hartmann sensor does not need a reference beam, the Hartmann sensor has advantages like simple structure and good environmental adaption, however, since the number of mirolens in Hartmann sensor is finite, the measurement resolution is obvious low for large diameter beam in laser driver. To solve the problems of poor performance of measuring tools in laser driver field, the CMI(Coherent Modulation Imaging) method has been applied in the measurement of wavefront of pulse beam in high power laser system and the measurement of suface characteristics of optical element with large diameter, the resolution can reach 2mm. Since the device of CMI is very simple and can be easy operated, the CMI method is suitable for online diagnostics of high power pulse beams. However since the CMI method just use one diffraction pattern, the constrains on the diffraction plane is relative weakly, besides, the step phase palte used in CMI method has large diffactive angle, and there exists phase jumpchanges at the phase boundary, which will lead to high order diffraction patterns and lost of high frequency information in the recorded diffraction pattern, thus the iterative converging speed of CMI method is slow, and the reconstructed result has low signal noise ratio.
Since the phase distribution of weakly scattering continuous object is continuous, there would be no high order diffraction patterns, and the diffractive angle of weakly scattering continuous object is small. This paper combines the ePIE(extended Ptychographty Iterative Engine) imaging method with the CMI imaging method, proposes the Coded Beam Splitting imaging method, realizing singleshot online diagnostic of beam complex amplitude with high resolution and high sinal noise ratio. This method uses a Dammann grating to split the beam to be measured into several same subbeams, these subbeams pass through different parts of a weakly scattering object with known structure, and form an array of diffraction patterns on the big target surface of charged coupled device. By adopting an iterative algorithm analogous to ePIE algorithm, the complex field of beam to be measured can be reconstructed rapidly and quickly from the recorded diffraction patterns. Studying the effect of phase density in weakly scattering continuous phaseplate and the number of diffraction patterns on the precision of iterative algorithm, proposing a singleshot phase retrieval method by using two coaxial located weakly scattering continuous phaseplates to reduce the complexity of light path. This article provides new methods for singleshot phase measurement of optical beam in laser driver, the main contents are as follows:
1. Proposed the beam splitting singleshot phase retrieval. Based on the beam splitting function of grating, the incident beam is split into diffracted beam cluster, and let these beam cluster pass through a weakly scattering plate to be modulated, the diffracted patterns are recorded by a CCD via singleshot, the distribution of incident beam is reconstructed by an iterative algorithm. This method uses beam splitting function of a grating to record many diffraction patterns in one singleshot, and the information used for reconstruction is improved largely compared with one diffraction pattern is used, this method has advantages like fast converging speed, high quality of imaging and high antinoise capacity.
2. Analyzing the influence of different noise, phase error, three dimentional defocus, and the misregistration of weakly scattering plate on the beam splitting iterative algorithm proposed above, then realize the reconstruction of the complex field of biological sample and on line detection of wavefront of incident beam
3. Using two weakly scattering continous phase plate to realize the high precision singleshot phase retrieval. Compared with strongly scattering step phase plate which have disadvantages like information lost in high frequency spectrum in the diffraction pattern and the reconstructed results containing speckles. The beam to be measured passing through weakly scattering continuous phaseplate can retain its high frequency information in diffraction pattern, when two random weakly scattering continuous phaseplates use together, the diffraction pattern will have more speckles, and the modulation ability will be more stronger, the converging precision of singleshot algorithm will be improved effectively.2019atalunwen21911313542646phase retrieval, coherent diffraction imaging, coded beam splitting, singleshotStudy on Phase Retrieval Imaging Based on Weakly Scattering Modulation基于弱散射调制的相位恢复成像技术研究光束质量是衡量高功率激光驱动器性能的重要参数，由于组成激光装置的大口径光学元件数量众多，驱动器光路规模庞大而且复杂，其激励光束的不规整、元件材料的不均匀、元件表面的划痕、损伤和污染等均会影响激光束的最终波前和振幅分布，使激光光束波前发生畸变，降低实验效果。对光束波前进行在线监测并及时补偿，可大幅度改善光束的输出能量、峰值功率、焦斑尺寸等关键参数，因此光束质量检测系统对于保证驱动器的平稳运行和性能提升意义重大。干涉仪和哈特曼传感器目前强激光领域中最常用的两种波前检测仪器，二者都具有较高的测量精度和技术稳定性，能够解决激光驱动器领域中的很多实际测量问题，但同时也存在较为明显的不足。干涉仪一般需要较大的工作空间，同时由于需要高精度的规整参考光，因此对工作环境稳要求较高，很难适应激光驱动器的工程现场测量需求。哈特曼传感器不需要参考光，具有结构简单和环境适用性好等优点，但由于微阵列透镜数量有限，对于驱动器的大口径光束来说，测量分辨率明显过低。为了解决激光驱动器领域光束测量工具性能不理想的问题，相干调制成像CMI（Coherent Modulation Imaging）方法曾经被尝试应用于测量高功率激光脉冲波前和大口径光学元件的面型，实验分辨率可达2mm。由于具有结构简单和操作方便的优点，CMI比较适合用于高功率激光束的在线检测，但由于其只用一幅衍射光斑进行相位恢复，衍射面上限制条件较弱，并且CMI方法中使用的台阶相位板由于其强散射特性和相位边界处存在跃变，衍射斑中会有高阶衍射以及存在高频信息丢失的情况，因此CMI方法迭代收敛速度较慢，且信噪比明显过低。
弱散射连续型物体由于其相位是连续型分布，因此衍射斑中不会存在高阶衍射，且弱散射物体衍射角度较小。本论文将ePIE(extended Ptychography Iternative Engine)成像方法和CMI成像方法相结合，提出分束编码成像技术(Coded Beam Splting）,实现高分辨和高信噪比的单次曝光光束复振幅在线测量。该方法用达曼光栅将待测量光束分成彼此相同的数个子光束，并让它们穿过一个结构已知的弱衍射物体的不同部分，然后在大靶面探测器上形成一个衍射光斑阵列，采用和ePIE相似的方法可以从这些衍射斑快速高精度地迭代出光束的复振幅；研究了弱散射连续型相位板中相位密度和衍射斑个数对于迭代恢复精度的影响，提出利用两块同轴放置的弱散射连续相位板实现单次曝光相位恢复技术，来减小光路结构的复杂度。本论文的研究内容，为实现驱动器光束的单次曝光测量相位提供新思路，具体包括以下几个方面：
1. 提出分束编码实现单次曝光相位恢复。利用光栅分光原理入射光束分为不同方向的光束簇，并让这些光束簇经过一个分布已知的弱衍射物体进行编码调制，由CCD单次曝光记录衍射斑阵列，通过迭代算法恢复出入射光束的复振幅分布。该方法通过光栅分光单次曝光记录多幅衍射斑，来提高迭代恢复中的信息量，具有收敛速度快，成像质量高，抗噪能力强等优点。
2. 分析分束编码实现单次曝光相位恢复中衍射斑中不同大小噪声，弱衍射物体的相位误差，三维离焦量，弱衍射板的偏移对于迭代恢复的影响并实现生物样品振幅和相位的恢复和光束波前的在线测量。
3. 利用两块弱散射的全息散射片实现单次曝光相位恢复。相比于强散射的台阶相位板存在衍射斑中高频信息丢失，恢复结果中带有散斑等缺点，待测光束经过弱散射相位板后其衍射斑中包含较多的高频信息，并且两块弱散射片使衍射斑中散斑更多，调制作用更强，能够有效提高单次曝光迭代过程中的收敛精度。相位恢复，相干衍射成像，分束编码，单次曝光中国科学院上海光学精密机械研究所何西光学工程博士

中文题目:
基于弱散射调制的相位恢复成像技术研究

外文题目:
Study on Phase Retrieval Imaging Based on Weakly Scattering Modulation

作者:
何西

导师姓名:
刘诚

学位授予机构:
中国科学院上海光学精密机械研究所 
答辩时间:
20181130

中文关键词: 
相位恢复，相干衍射成像，分束编码，单次曝光

英文关键词: 
phase retrieval, coherent diffraction imaging, coded beam splitting, singleshot

中文摘要: 
光束质量是衡量高功率激光驱动器性能的重要参数，由于组成激光装置的大口径光学元件数量众多，驱动器光路规模庞大而且复杂，其激励光束的不规整、元件材料的不均匀、元件表面的划痕、损伤和污染等均会影响激光束的最终波前和振幅分布，使激光光束波前发生畸变，降低实验效果。对光束波前进行在线监测并及时补偿，可大幅度改善光束的输出能量、峰值功率、焦斑尺寸等关键参数，因此光束质量检测系统对于保证驱动器的平稳运行和性能提升意义重大。干涉仪和哈特曼传感器目前强激光领域中最常用的两种波前检测仪器，二者都具有较高的测量精度和技术稳定性，能够解决激光驱动器领域中的很多实际测量问题，但同时也存在较为明显的不足。干涉仪一般需要较大的工作空间，同时由于需要高精度的规整参考光，因此对工作环境稳要求较高，很难适应激光驱动器的工程现场测量需求。哈特曼传感器不需要参考光，具有结构简单和环境适用性好等优点，但由于微阵列透镜数量有限，对于驱动器的大口径光束来说，测量分辨率明显过低。为了解决激光驱动器领域光束测量工具性能不理想的问题，相干调制成像CMI（Coherent Modulation Imaging）方法曾经被尝试应用于测量高功率激光脉冲波前和大口径光学元件的面型，实验分辨率可达2mm。由于具有结构简单和操作方便的优点，CMI比较适合用于高功率激光束的在线检测，但由于其只用一幅衍射光斑进行相位恢复，衍射面上限制条件较弱，并且CMI方法中使用的台阶相位板由于其强散射特性和相位边界处存在跃变，衍射斑中会有高阶衍射以及存在高频信息丢失的情况，因此CMI方法迭代收敛速度较慢，且信噪比明显过低。
弱散射连续型物体由于其相位是连续型分布，因此衍射斑中不会存在高阶衍射，且弱散射物体衍射角度较小。本论文将ePIE(extended Ptychography Iternative Engine)成像方法和CMI成像方法相结合，提出分束编码成像技术(Coded Beam Splting）,实现高分辨和高信噪比的单次曝光光束复振幅在线测量。该方法用达曼光栅将待测量光束分成彼此相同的数个子光束，并让它们穿过一个结构已知的弱衍射物体的不同部分，然后在大靶面探测器上形成一个衍射光斑阵列，采用和ePIE相似的方法可以从这些衍射斑快速高精度地迭代出光束的复振幅；研究了弱散射连续型相位板中相位密度和衍射斑个数对于迭代恢复精度的影响，提出利用两块同轴放置的弱散射连续相位板实现单次曝光相位恢复技术，来减小光路结构的复杂度。本论文的研究内容，为实现驱动器光束的单次曝光测量相位提供新思路，具体包括以下几个方面：
1. 提出分束编码实现单次曝光相位恢复。利用光栅分光原理入射光束分为不同方向的光束簇，并让这些光束簇经过一个分布已知的弱衍射物体进行编码调制，由CCD单次曝光记录衍射斑阵列，通过迭代算法恢复出入射光束的复振幅分布。该方法通过光栅分光单次曝光记录多幅衍射斑，来提高迭代恢复中的信息量，具有收敛速度快，成像质量高，抗噪能力强等优点。
2. 分析分束编码实现单次曝光相位恢复中衍射斑中不同大小噪声，弱衍射物体的相位误差，三维离焦量，弱衍射板的偏移对于迭代恢复的影响并实现生物样品振幅和相位的恢复和光束波前的在线测量。
3. 利用两块弱散射的全息散射片实现单次曝光相位恢复。相比于强散射的台阶相位板存在衍射斑中高频信息丢失，恢复结果中带有散斑等缺点，待测光束经过弱散射相位板后其衍射斑中包含较多的高频信息，并且两块弱散射片使衍射斑中散斑更多，调制作用更强，能够有效提高单次曝光迭代过程中的收敛精度。

英文摘要: 
In high power laser system, the quality of laser beam is the key role of inertial confinement fusion, however, the high power laser system contains a lot of optical elements with large diameter, the scale of light path is huge and complicated, the irregularity of excitation beam, nonuniformity of optical device material, the scratches, damage and contamination on the surface of optical elements will affect the quality and amplitude distribution of wavefront in the process of optical transmission, and distort the wavefront of laser beam, degrading the result of experiment. Monitoring the quality of laser beam wavefront in real time and making the compensation adjustment accordingly will improve the output energy, peak power and size of focus point substantially, thus the beam quality diagnostic system has great significance to keep the high power laser system running smoothly and improve its performance. At present the common optical wavefront measurement device in high power laser field includes the interferometers and Hartmann wavefront sensor, both of them have relatively high measurement accuracy and technical stability, they can solve most of the pratical measurement problems in laser driver field, but they also have obvious deficiency. The interferometers occupies large spatial volume and needs a regular reference beam, the interferometers demands high stability of environment, and is not suitable in online diagnostics of pulse beams in high power laser system. The Hartmann sensor does not need a reference beam, the Hartmann sensor has advantages like simple structure and good environmental adaption, however, since the number of mirolens in Hartmann sensor is finite, the measurement resolution is obvious low for large diameter beam in laser driver. To solve the problems of poor performance of measuring tools in laser driver field, the CMI(Coherent Modulation Imaging) method has been applied in the measurement of wavefront of pulse beam in high power laser system and the measurement of suface characteristics of optical element with large diameter, the resolution can reach 2mm. Since the device of CMI is very simple and can be easy operated, the CMI method is suitable for online diagnostics of high power pulse beams. However since the CMI method just use one diffraction pattern, the constrains on the diffraction plane is relative weakly, besides, the step phase palte used in CMI method has large diffactive angle, and there exists phase jumpchanges at the phase boundary, which will lead to high order diffraction patterns and lost of high frequency information in the recorded diffraction pattern, thus the iterative converging speed of CMI method is slow, and the reconstructed result has low signal noise ratio.
Since the phase distribution of weakly scattering continuous object is continuous, there would be no high order diffraction patterns, and the diffractive angle of weakly scattering continuous object is small. This paper combines the ePIE(extended Ptychographty Iterative Engine) imaging method with the CMI imaging method, proposes the Coded Beam Splitting imaging method, realizing singleshot online diagnostic of beam complex amplitude with high resolution and high sinal noise ratio. This method uses a Dammann grating to split the beam to be measured into several same subbeams, these subbeams pass through different parts of a weakly scattering object with known structure, and form an array of diffraction patterns on the big target surface of charged coupled device. By adopting an iterative algorithm analogous to ePIE algorithm, the complex field of beam to be measured can be reconstructed rapidly and quickly from the recorded diffraction patterns. Studying the effect of phase density in weakly scattering continuous phaseplate and the number of diffraction patterns on the precision of iterative algorithm, proposing a singleshot phase retrieval method by using two coaxial located weakly scattering continuous phaseplates to reduce the complexity of light path. This article provides new methods for singleshot phase measurement of optical beam in laser driver, the main contents are as follows:
1. Proposed the beam splitting singleshot phase retrieval. Based on the beam splitting function of grating, the incident beam is split into diffracted beam cluster, and let these beam cluster pass through a weakly scattering plate to be modulated, the diffracted patterns are recorded by a CCD via singleshot, the distribution of incident beam is reconstructed by an iterative algorithm. This method uses beam splitting function of a grating to record many diffraction patterns in one singleshot, and the information used for reconstruction is improved largely compared with one diffraction pattern is used, this method has advantages like fast converging speed, high quality of imaging and high antinoise capacity.
2. Analyzing the influence of different noise, phase error, three dimentional defocus, and the misregistration of weakly scattering plate on the beam splitting iterative algorithm proposed above, then realize the reconstruction of the complex field of biological sample and on line detection of wavefront of incident beam
3. Using two weakly scattering continous phase plate to realize the high precision singleshot phase retrieval. Compared with strongly scattering step phase plate which have disadvantages like information lost in high frequency spectrum in the diffraction pattern and the reconstructed results containing speckles. The beam to be measured passing through weakly scattering continuous phaseplate can retain its high frequency information in diffraction pattern, when two random weakly scattering continuous phaseplates use together, the diffraction pattern will have more speckles, and the modulation ability will be more stronger, the converging precision of singleshot algorithm will be improved effectively.


