相位恢复测量长焦距镜面

针对长焦距光学镜面检测中测量光路长,振动干扰较大,不容易用干涉仪进行面形检测的难题,提出了一种基于相位恢复技术的测量方法.该方法用相干点光源照射被测镜,采集一系列焦点附近的衍射光强图像,然后运用相位恢复算法得到镜面面形误差分布.利用衍射光学理论建立了测量模型,并用基于Gerchberg-Saxton算法的迭代算法求解模型.然后仿真验证了光场传播模型的可靠性和测量算法的有效性,并用该方法测量了一块曲率半径8 700 mm,口径145 mm的球面镜.通过对光强图像位置进行优化,并选择适当离焦位置的图像,最终恢复出了镜面面形.相位恢复测量的结果与动态干涉仪测量结果基本一致,并且测量装置简单,对环境要求低.     

相位恢复测量长焦距镜面(英文)

针对长焦距光学镜面检测中测量光路长,振动干扰较大,不容易用干涉仪进行面形检测的难题,提出了一种基于相位恢复技术的测量方法.该方法用相干点光源照射被测镜,采集一系列焦点附近的衍射光强图像,然后运用相位恢复算法得到镜面面形误差分布.利用衍射光学理论建立了测量模型,并用基于Gerchberg-Saxton算法的迭代算法求解模型.然后仿真验证了光场传播模型的可靠性和测量算法的有效性,并用该方法测量了一块曲率半径8700mm,口径145mm的球面镜.通过对光强图像位置进行优化,并选择适当离焦位置的图像,最终恢复出了镜面面形.相位恢复测量的结果与动态干涉仪测量结果基本一致,并且测量装置简单,对环境要求低.     

Full field deformation measurement of centimeter sized objects using optical phase retrieval

Most papers in the field of optical phase retrieval either consider only the intensity (or amplitude) profile of the object under inspection (or scatterer location in the X-ray version), or a uniform tilt/rotation of the object beam. However, phase retrieval is able to recover the phase profile of the object (beam) as well, which theoretically makes the observable interference of phase retrieved object waves possible. In this paper we demonstrate this principle experimentally on centimeter sized deformable reflective objects (as large as 40 mm by 40 mm) and corresponding simulations are also presented. When the CCD camera is moved along the optical axis in the Fresnel region, the interference fringes of the displacement field have low contrast. On the other hand, when an imaging setup is built, and the camera moves near the image plane, high fringe contrast can be obtained. These fringes however suffer from some phase error. In our work the iterative modulus projection algorithm was used as a simply implementable phase retrieval method.     

频率分辨光学开关法行迹相位还原的时频分析

将小波变换分析光谱相位相干原理应用于频率分辨光学开关(FROG)行迹图的时间-频率分析，不需要传统的迭代算法，从对FROG行迹的脊的分析中，直接得到超短脉冲的相位.对于FROG行迹的脊变化平缓的脉冲得到了精确的相位. 关键词： 超短脉冲 相位重建     

A review of iterative phase retrieval for measurement and encryption

Phase retrieval technique is regarded as one of the most significant tools to solve optical inverse problems. Several phase retrieval algorithms are discussed in this review. The occurrence of ill-posed conditions often makes the calculation difficult. As a synthesis, the multiple-image phase retrieval technology is invented to obtain more accurate convergence result in iterative computation. The multiple-input retrieval scheme can attach new constraints on convergence as a new limitation. As an indirect measuring method, it will make it possible to reconstruct the distribution of intensity and phase in an imaging or measurement system, where data processing is executed by computer. Moreover, the retrieval method has been applied for image encryption successfully. Finally, the development and application of the iterative phase retrieval are overviewed.     

相位恢复算法用于光学面形检测的实验研究

 针对相位恢复测量中遇到的初始相位估计、传播因子和收敛判断等问题,以柱面透镜的光学面形为恢复对象,应用迭代相位恢复算法完成了对柱面透镜的光波波前的相位恢复实验,并对实验结果进行了分析。实验结果表明：根据被测对象的光波形态选择最接近的初始相位能够加快收敛速度,避免局部收敛,是保证结果准确与可靠的重要条件。通过对两个记录面上的光强之和做求比值运算计算传播因子 ,并应用到传播公式中,能够消除激光光束本身稳定性与探测器响应均匀性等因素对计算结果的影响。     

Application of single-beam homodyne SPIDER for the control of complex spectral phase profiles

We investigate the range of application of single-beam homodyne spectral phase interferometry for direct electric field reconstruction (SPIDER) for multiphoton microscopy. Simulations and experimental studies performed on model spectral phase profiles show that the phase reconstruction technique used in this method makes the phase retrieval quality highly sensitive to the complexity of the profile. In addition, we show that the use of iterative processes is likely to deteriorate the phase retrieval quality, especially for strongly varying phase profiles. These effects are illustrated and quantified for sinusoidal and quadratic spectral phase profiles.     

Optimizing calculation of phase screen distribution with minimum condition along an inhomogeneous turbulent path

When building an experimental platform for light propagation along an inhomogeneous turbulent path,it is very essential to set up the reasonable distribution of phase screen.Based on multi-layered model of phase screen,an iterative optimization algorithm of phase screen position is given in this paper.Thereafter,the optimal position of phase screens is calculated under the Hufnagel-Valley5/7 and Hefei-day turbulence profile.The results show that the positions of phase screen calculated by the iterative algorithm can fit well with the turbulence profile rather than mechanically placed phase screens at equal distance.Compared with the uniform distribution of phase screens position,the residual phase error of the iterative algorithm decreases very significantly.The similarity degree between them is minimal when number of layers is equal to two.     

硬x射线同轴相衬成像的相位恢复

基于角谱的概念，分析了硬x射线同轴相衬成像过程，在传统相位恢复算法GS算法的基础上 ，提出了基于角谱传播的相位恢复算法——迭代角谱法（IASA），并利用数值法模拟研究了 相衬成像和相位恢复过程，从理论上验证了这一相位恢复算法. 关键词： 相位恢复 相位衬度 角谱 硬x射线     

Performance analysis of quantitative phase retrieval method in Zernike phase contrast X-ray microscopy

Since the invention of Zernike phase contrast method in 1930,it has been widely used in optical microscopy and more recently in X-ray microscopy.Considering the image contrast is a mixture of absorption and phase information,we recently have proposed and demonstrated a method for quantitative phase retrieval in Zernike phase contrast X-ray microscopy.In this contribution,we analyze the performance of this method at different photon energies.Intensity images of PMMA samples are simulated at 2.5 keV and 6.2 keV,respectively,and phase retrieval is performed using the proposed method.The results demonstrate that the proposed phase retrieval method is applicable over a wide energy range.For weakly absorbing features,the optimal photon energy is 2.5 keV,from the point of view of image contrast and accuracy of phase retrieval.On the other hand,in the case of strong absorption objects,a higher photon energy is preferred to reduce the error of phase retrieval.These results can be used as guidelines to perform quantitative phase retrieval in Zernike phase contrast X-ray microscopy with the proposed method.     

Phase-Shifting Fringe Analysis for Laser Diode Wavelength-Scanning Interferometer

A method for analyzing the fringe patterns obtained from a wavelength-scanning interferometer is proposed. It is based on phase retrieval with the phase-shifting method and derivation of its slope along the wave number axis. The accuracy and the error sources are estimated by experiments, in which a laser diode under small wavelength-modulation (-95pm) is used as the light source. A conventional piezoelectric phase shifter was used for a phase shifter. This technique can be applied to profile measurement of stepped objects located across the zero-path position.     

Asymmetric multiple-image hiding using phase retrieval technique based on amplitude- and phase-truncation in fractional Fourier domain

We propose a multiple-image hiding scheme based on the amplitude- and phase-truncation approach, and phase retrieval iterative algorithm in the fractional Fourier domain. The proposed scheme offers multiple levels of security with asymmetric keys. Multiple input images multiplied with random phase masks are independently fractional Fourier transformed with different orders. The individual keys and common keys are generated by using phase and amplitude truncation of fractional spectrum. After using two fractional Fourier transform, the resultant encrypted image is hided in a host image with phase retrieval iterative algorithm. Using the correct universal keys, individual keys, and fractional orders, one can recover the original image successfully. Computer simulation results with four gray-scale images support the proposed method. To measure the validity of the scheme, we calculated the mean square error between the original and the decrypted images. In this scheme, the encryption process and generation of decryption keys are complicated and should be realized using computer. For decryption, an optoelectronic setup has been suggested.     

Experimental verification of coherent diffractive imaging by a direct phase retrieval method with an aperture-array filter

Recently, we have proposed a coherent diffractive imaging using a noniterative phase retrieval method with the filter of an aperture array. The first (to our knowledge) experimental demonstration of this coherent imaging is presented here, in which a complex-valued object illuminated by a diode laser is reconstructed from the isolated diffraction intensities of the object's wave field, transmitted through an array filter of square apertures by using the phase retrieval method. This imaging method requires only a single measurement of the diffraction intensity and does not need a tight object's support constraint utilized in iterative phase retrieval algorithms or a reference wave used in holographic techniques.     

一种基于图像融合和卷积神经网络的相位恢复方法

相位恢复法利用光波传输中某一(或某些)截面上的光强分布来传感系统波前,其结构简单,不易受震动及环境干扰,被广泛应用于光学遥感和像差检测等领域.传统相位恢复法采用迭代计算,很难满足实时性要求,且在一定程度上依赖于迭代转换或迭代优化初值.为克服上述问题,本文提出了一种基于卷积神经网络的相位恢复方法,该方法采用基于小波变换的图像融合技术对焦面和离焦面图像进行融合处理,可在不损失图像信息的同时简化卷积神经网络的输入.网络模型训练完成后可依据输入的融合图像直接输出表征波前相位的4-9阶Zernike系数,且波前传感精度均方根(root-mean-square,RMS)可达0.015λ,λ=632.8 nm.研究了噪声、离焦量误差和图像采样分辨率等因素对波前传感精度的影响,验证了该方法对噪声具有一定鲁棒性,相对离焦量误差在7.5%内时,波前传感精度RMS仍可达0.05λ,且随着图像采样分辨率的提升,波前传感精度有所改善,但训练时间成本随之增加.此外,分析了实际应用中,当系统像差阶数与网络训练阶数略有差异时,本方法所能实现的传感精度,并给出了解决方案.     

Phase retrieval from double axially displaced holograms for dual-wavelength in-line holography

A phase retrieval method for dual-wavelength in-line digital holography is presented with double axially displaced holograms.A synthetic wavelength is used during iterative propagations to retrieve wrap-free phase distributions with a much extended measurement range.The simulation and experimental results demonstrate a better elimination of the twin image,a faster rate of convergence of the iterative routine and less number of wavelengths are compared with previously reported multiple-wavelength in-line holography.     

A spatial domain constraint iterative phase retrieval method for the propagation based X ray phase contrast imaging

Based on the propagation X ray phase contrast imaging theory, a spatial domain constraint iterative phase retrieval method is described in detail. This algorithm limits the object spatial domain according to the actual sample size firstly, and modify the image plane data with the actual test data, then the iteration can be terminated until iteration precision or the number of iterations meet the preset requirements. Finally the numerical simulation is made to evaluate the rapid phase retrieval algorithm performance, and a real column fiber material experiment is carried out using a micro focus X ray phase contrast imaging experiment platform, the phase distribution image of the column fiber is calculated out by this algorithm. The results show that this phase retrieval algorithm is effective, and the method has a potential stability and accuracy for X ray phase contrast imaging technology.     

中心挡板对扫描相干X射线衍射成像的影响

本文采用重叠关联迭代引擎算法, 系统地模拟研究了扫描相干衍射成像中中心挡板导致的低频信号丢失对重建图像质量的影响. 结果表明, 扫描相干衍射成像对中心挡板的承受能力远大于平面波单次相干衍射成像, 且选择小尺寸入射探针和较高重叠度(≥ 70%)可进一步降低中心丢失信号对扫描相干衍射成像的负面影响. 另外, 光斑扫描位置误差在重叠度较高时将超过中心挡板成为扫描相干衍射成像最主要的负面影响因素. 本文研究结果对扫描相干衍射成像实验中如何应用中心挡光板具有重要的指导意义, 将有助于进一步提高扫描相干衍射成像的分辨率. 关键词： 扫描相干衍射成像 位相恢复算法 低频丢失信号     

Reconstruction of holograms generated by using a combination of an iterative method and an error diffusion method

Two-level quantized phase holograms produced by using a combination of an iterative method and an error diffusion method are presented. By using a previously proposed iterative method, images reconstructed from two-level quantized phase holograms are rapidly improved with small amounts of iterative operations but further improvement of the image quality is difficult even if the iterations are greatly increased. Therefore, in order to exceed the improvement limitation of the image quality, the combination of the iterative method and an error diffusion method was used for the hologram-making process. Experimental results using the combination method showed better images than those obtained by the iterative method alone, when referred to results from synthesized holograms.     

瑞利散射多普勒激光雷达风场反演方法

介绍了瑞利散射多普勒激光雷达的风场探测原理和系统结构. 给出了Fabry-Perot(FP)标准具透过率曲线的校准方法. 指出对透过率采用Lorentz或Voigt拟合会产生较大误差,特别是采用Lorentz拟合最大将引起8%的误差. 提出了采用非线性最小二乘法拟合标准具的透过率函数,该方法可以有效消除拟合误差,提高风速测量精度. 考虑到温度不确定度在风场反演过程中的主导影响,提出了同时反演风速和大气温度的非线性迭代算法. 风场反演仿真试验结果表明:在不考虑米散射信号的影响下,该反演算法与传统的反演方法相 关键词： 激光雷达 瑞利散射 多普勒 风     

基于液面旋转平移法的绝对检验技术研究

绝对检验作为一种光学元件高精度检测方法,其中的两平晶绝对检验无法精确测量平移过程中的倾斜误差,导致恢复的面形中二次项出现偏差.液面在位置变化前后能够保持水平,在旋转平移过程中不会产生倾斜误差.推导了平移过程中倾斜误差和恢复面形中离焦项的关系,并通过仿真分析加以验证,当不存在倾斜误差时,残差面PV值小于1nm.在300m...