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(a) The CPP used in the experiment. The diameter is 31 cm, shown by the adjacent scale, (b) the designed phase distribution of CPP, and (c) the measurement of CPP by Zygo interferometer
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Wavefront control is a significant parameter in inertial confinement fusion (ICF). The complex transmittance of large optical elements which are often used in ICF is obtained by computing the phase difference of the illuminating and transmitting fields using Ptychographical Iterative Engine (PIE). This can accurately and effectively measure the tra...
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Accurate measurements of the transmittance of large optical elements are essential to improve the energy density in inertial confinement fusion (ICF). The required complex transmittance of such optical elements used in ICF is obtained by computing the phase difference between the illuminating and transmitting fields using modulation coherent imagin...
Citations
... Compared to other CDI techniques, it has achieved a qualitative improvement in convergence speed and imaging quality, with the advantages of fast convergence, strong anti-noise interference ability, and scalable imaging range [9]. As a result, it has found widespread applications in various fields, including electron beam imaging [10], biomedical imaging [11], super-resolution imaging [12], and optical component detection [13]. ...
The ptychographic iterative engine (PIE) is a lensless coherent diffraction imaging algorithm known for its simplicity, easy to use, scalability, and fast convergence. However, practical applications often encounter interference in imaging results caused by non-static scattering media, such as dense fog, seawater target detection and medical biology diagnosis. To address this challenge, we propose a novel approach using computational deep learning for dynamic scattering medium image reconstruction, enabling lens-free coherent diffraction imaging through dynamic scattering media. Through extensive analysis, we evaluate the effectiveness of the neural network for PIE image recovery under varying scattering medium concentration conditions. We also test scattering images obtained by hybrid training with different concentrations of scattering medium to assess the generalisation ability of the neural network. The experimental results demonstrate that our proposed method achieve PIE lens-free imaging under non-static scattering media interference. This coherent diffraction imaging method, based on transmission through dynamic scattering media, opens up new possibilities for practical applications of PIE and fosters its development in complex environments. Its significance extends to fields like atmospheric pollution, seawater target detection and medical biology diagnosis, providing valuable references for research in these domains.
... 去除编码板的调制， 更新编码板面入射光的分布 Fig. 15 Schematic of iterative process for BSEA coherent diffraction imaging [43] , f 1 , f 2 , f 3 , and f 4 represent the focal points of four subbeams, d m represents the translation vector, and the top right illustration is the recorded diffraction spot Fig. 16 Schematic of lightpath in the BSEA experiment [43] Fig. 17 Reconstruction capability comparison between BSEA and traditional CMI [43] . Fig. 18 Application of CDI in phase measurement of large aperture optical elements [23,50] . Fig. 24 Focal spots recorded by Hardman sensor [38] . ...
... 10 After decades of development, diverse variants of CDI have emerged, e.g., CDI by modulating the light beam scattered from the sample [coherent modulation imaging (CMI)], [11][12][13] CDI by recording several diffraction patterns from overlapping areas of the sample (ptychography), [14][15][16][17] and CDI by recording the volume speckle field from a sample at different planes. [18][19][20] These CDI technologies offer a high imaging resolution, wide field of view, and high accuracy, and have been useful in the field of metrology, such as for optical element measurement [21][22][23] and laser beam diagnosis. [24][25][26] However, in CDI, the detector records only the intensity information of the far-field diffraction of the object. ...
A linear model for coherent diffractive imaging (CDI) is proposed herein. In this model, CDI is expressed as a system of linear equations in the frequency domain of an object and illumination. The linear system can be directly determined to provide a unique solution for complex samples. The method is analytical and straightforward and does not require any approximation. The simulation results demonstrate that the proposed method is valid for all CDI-related imaging methods, such as traditional CDI, ptychography, coherent modulation imaging, and multiple-plane phase retrieval. The relationship between the method and the convergence of iterative phase retrieval is discussed. This mathematical model provides a direct method for analyzing the underlying physics of CDI and can be used to predict the accuracy and error in CDI applications, such as measurement and metrology.
... Ptychographic iterative engine (PIE) [1][2][3][4][5][6][7][8][9][10][11][12] can retrieve the complex amplitude of an object from a series of diffraction patterns, where field-of-view (FOV) is expanded and resolution is improved. In ptychography methods [1][2][3][4][5][6], the object or the probe must be moved by two-dimensional (2-D) device and the information of translation positions is essential to obtain a high-quality image. ...
... Ptychographic iterative engine (PIE) [1][2][3][4][5][6][7][8][9][10][11][12] can retrieve the complex amplitude of an object from a series of diffraction patterns, where field-of-view (FOV) is expanded and resolution is improved. In ptychography methods [1][2][3][4][5][6], the object or the probe must be moved by two-dimensional (2-D) device and the information of translation positions is essential to obtain a high-quality image. Cross-correlation was widely used for position correction in ptychography [13][14][15]. ...
It is beneficial to improve the resolution by a diffuser in imaging systems, because higher frequency information could be involved into the captured patterns via scattering effect. In this paper, a lensless imaging method is designed by 1-D scanning. A diffuser is placed upstream of the object, which is translated in a one-dimensional path and corresponding positions are corrected by cross-correlation. Our method requires a diffraction pattern of the object without a diffuser to speed up convergence and improve resolution. In field reconstruction, the amplitude constraint is added into the iterative phase retrieval algorithm. The high-quality complex-valued images can be obtained with ∼15 patterns. As a ptychography, the proposed method only needs a 1-D device, which could simplify the experimental equipment for reducing costs and measurement time.
... In CDI [1], the field of view (FOV) is limited by the wavelength and the numerical aperture of optical system [2]. The ptychographic iterative engine (PIE) [3][4][5][6] was proposed for expanding FOV. The concept of PIE is that the object was illuminated by an optical probe and is moved on the plane perpendicular to the optical axis. ...
... The influence of spatial frequency transfer characteristics on the accuracy of quality assessment for optics must also be considered [8,9]. Recently a phase-retrieval method based on ptychography has been introduced as an alternative method for some physical measurements, such as component measurements [10][11][12] and wavefield characterizations [13][14][15], and has attracted much attention in the field of high power lasers [15][16][17]. Through the extended ptychographical iterative engine (ePIE) algorithm, the probe, containing the wavefront structure of the tested optical component, and the object are reconstructed from multiple diffraction patterns with overlapping illuminated regions. ...
In a high power laser system, the wavefront quality of large optical components in the mid spatial frequency band plays a critical role in system performance and safe operation. A simple and efficient method based on ptychography is used to measure mid-frequency wavefront error, which has the advantages of simple structure, strong anti-interference ability, flexible frequency-range selection, and low cost. It has excellent frequency response in the entire mid-frequency region. The transfer function is demonstrated to be greater than 0.7 at 1/2 Nyquist frequencies ( 8.33 mm − 1 ) for 60 mm field-of-view experimentally. The method has been successfully applied to the wedged focused lens (WFL) to achieve high-fidelity measurement. Without any auxiliary lens, the power spectrum of the WFL at the frequency of interest is obtained through large-aperture measurement. This technique is especially suitable for optical components difficult to be measured using interferometers and opens up a new perspective for measuring mid-frequency wavefronts.
... A typical FP employs an angle-varied plane wave generated by a light-emitting diode (LED) matrix illuminating the sample and records the corresponding low-resolution (LR) image at each angle. The FP method originated from ptychography [11][12][13][14][15][16][17][18], a type of scanning lensless coherent diffraction imaging (CDI) [19][20][21][22][23][24] technique for high-resolution complex image recovery, which laterally scans a sample at several points with respect to a localized illumination beam. In FP, angle-varied illumination, which is equivalent to the scanning of the two-dimensional (2D) Fourier spectrum of the sample with respect to the coherent transform function (CTF) of the employed objective lens, is combined with a Fourier ptychographic phase retrieval algorithm [5][6][7][8] to recover the complex expanded Fourier spectrum, resulting in reconstructed images with a resolution higher than the resolution limit of the objective lens. ...
Aperture-scanning Fourier ptychography [Opt. Express 22, 13586 (2014)] is a promising non-interferometric wavefront measurement technique. It eliminates the thin-sample requirement in typical Fourier ptychography employing angle-varying illumination. However, as aperture-scanning Fourier ptychography is based on step-by-step scanning, it requires long data acquisition time and a high-stability optical system. In this paper, we propose a single-shot aperture-scanning Fourier ptychography method. In our method, multiple low-resolution images are collected in a single shot by inserting a Dammann grating at a certain distance before the aperture, and the images are subsequently converted to a high-resolution complex wavefront. Compared with scanning-based aperture-scanning Fourier ptychography, the total acquisition time of the proposed method is dramatically reduced. The feasibility of our proposed method is demonstrated by proof-of-concept experiments.
... To break through the limitation of the traditional CDI, Rodenburg et al. proposed the Ptychographic Iterative Engine (PIE) method [31][32][33][34][35][36], which records all the diffraction patterns by transversely scanning the object relative to the fixed local illumination beam to a set of positions, and uses a Wigner filter like updating formula for sample information reconstruction iteratively. The shifting of the object relative to the illumination generates huge data redundancy and drastically increases the possibility of escaping the local minimum and ambiguous models, therefore, PIE can generate highquality images rapidly and has been widely adopted in imaging with visible light, X-ray and electron beam imaging [37][38][39][40]. ...
Though ptychographic iterative engine (PIE) has been widely adopted in the quantitative micro-imaging with various illuminations as visible light, X-ray and electron beam, the mechanical inaccuracy in the raster scanning of the sample relative to the illumination always degrades the reconstruction quality seriously and makes the resolution reached much lower than that determined by the numerical aperture of the optical system. To overcome this disadvantage, the sub-aperture switching based PIE method is proposed: the mechanical scanning in the common PIE is replaced by the sub-aperture switching, and the reconstruction error related to the positioning inaccuracy is completely avoided. The proposed technique remarkably improves the reconstruction quality, reduces the complexity of the experimental setup and fundamentally accelerates the data acquisition and reconstruction.
... For the optical metrology of imaging systems [7,9,10,[14][15][16], the generalized exit pupil function [17], rather than an object, is the unknown complex field of interest. A subaperture or mask is introduced in a plane ideally conjugate to the pupil. ...
We introduce unknown-transverse translation diversity phase retrieval: a ptychographic algorithm for optical metrology when a subaperture is translating through a plane conjugate to the exit pupil in a very poorly known fashion. The algorithm estimates the direction of translation and the distance traveled by the subaperture from one point spread function (PSF) to the next. It also estimates unknown point target motion and rotations of the subaperture between PSF acquisitions from the PSF data.
... In this paper we will demonstrate that MCI method can be used to measure the complex transmittance of large-aperture elements of an ICF system. A continuous phase plate (CPP), which is a key device used for smoothing the focal spot of the high-power laser beam and having a highly irregular surface profile [15][16][17], is used as an example to demonstrate the feasibility of this method. It only needs to record a diffraction pattern and then the transmittance of the large-diameter component can be retrieved by certain iterative calculations that may last only a few minutes. ...
Accurate measurements of the transmittance of large optical elements are essential to improve the energy density in inertial confinement fusion (ICF). The required complex transmittance of such optical elements used in ICF is obtained by computing the phase difference between the illuminating and transmitting fields using modulation coherent imaging (MCI). A phase plate designed as a modulator has a known transmission function in this technique. It presents a simple and quick method to measure the transmittance of large optical elements with irregular surface profiles by retrieving it from only two diffraction patterns recorded by a CCD camera. The complex transmittance of a continuous phase plate (CPP) with a large aperture used in ICF is measured experimentally, and the results are found to agree with the designed value.
