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Making the link between ADF and 4D STEM:Resolution,transfer and coherence

Chinese Physics B 2024年第11期33卷 26-33页

作者： Peter D.Nellist Timothy J.Pennycook Department of Materials University of OxfordOxfordUK EMAT University of AntwerpGroenenborgerlaan 1712020 AntwerpBelgium

Steve Pennycook is a pioneer in the application of high-resolution scanning transmission electron microscopy(STEM)and in particular the use of annular dark-field(ADF)*** we show how a general framework for 4D STEM allows clear links to be made between ADF imaging and the emerging methods for reconstructing images from 4D STEM data *** show that both ADF imaging and ptychographical reconstruction can be thought of in terms of integrating over the overlap regions of diffracted discs in the detector *** approach allows the similarities in parts of their transfer functions to be understood,though we note that the transfer functions for ptychographic imaging cannot be used as a measure of information *** also show that conditions of partial spatial and temporal coherence affect ADF imaging and ptychography similarly,showing that achromatic interference can always contribute to the image in both cases,leading to a robustness to partial temporal coherence that has enabled high-resolution imaging.

关键词： image forming and processing phase retrieval electron microscopy scanning transmission electron microscope(STEM)

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Scalar and vectorial vortex filtering based on geometric phase modulation with a Q-plate

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JOURNAL OF OPTICS 2019年第6期21卷

作者： Li, Delin Feng, Shaotong Nie, Shouping Ma, Jun Yuan, Caojin Nanjing Normal Univ Key Lab Optoelect Technol Jiangsu Prov Nanjing 210023 Jiangsu Peoples R China Nanjing Univ Sci & Technol Sch Elect Engn & Optoelect Tech Nanjing 210094 Jiangsu Peoples R China

We propose a method of scalar and vectorial vortex filtering to achieve edge enhancement by using a Q-plate. The Q-plate provides geometric phase which acts in a different way depending on the polarization state of the illuminating beam. It is shown from theoretical analysis that the scalar and vectorial vortex filtering can be changed with different illuminating polarization states. The filtering property of the system is vectorial under linear polarized illumination, while the filtering is scalar one under circularly polarized illumination. We also found that the above theory is also suitable when the center of the Q-plate is off-axis. The shadow effect caused by off-axis Q-plate can be eliminated by rotating the analyzer. In addition, we compare autofocusing Airy beam (AAB) and Gaussian beam in the theoretical and experiment sections. Higher contrast and less noise can be achieved under AAB illumination. The experimental results agree well with the theoretical expectations.

关键词： image forming and processing polarization optical vortices edge enhancement

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Spatio-temporal correlation super-resolution optical fluctuation imaging

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EPL 2019年第2期125卷

作者： Purohit, A. Vandenberg, W. Dertinger, T. Woell, D. Dedecker, P. Enderlein, J. Rhein Westfal TH Aachen Inst Phys Chem Landoltweg 2 D-52074 Aachen Germany Katholieke Univ Leuven Dept Chem Celestijnenlaan 200G B-3001 Heverlee Belgium Georg August Univ Inst Phys Biophys 3 D-37077 Gottingen Germany

We describe a new concept of multimodal super-resolution imaging which combines the cumulant analysis from Super-resolution Optical Fluctuation Imaging (SOFT) with the imprinting of three-dimensional, spectral or other information into peculiar Point-Spread Function (PSF) patterns. This concept allows for encoding multidimensional or multimodal information into a single image plane and to extract this information by an appropriate spatio-temporal correlation analysis of emitter fluctuations. Here, we develop the general theory of this concept, and present proof-of-principle experiments of three-dimensional super-resolution imaging. Copyright (C) EPLA, 2019

关键词： Conventional optical microscopes image forming and processing Optical microscopy

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Modified Sagnac imaging spectropolarimeter for full linear Stokes parameters

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EPL 2018年第5期124卷

作者： Gao, Peng Hu, Xiaochen Guo, Guanghai Kang, Yongqiang Ai, Jingjing Wang, Xia Qingdao Univ Sci & Technol Shandong Adv Optoelect Mat & Technol Engn Lab Coll Math & Phys Sci Qingdao 266061 Peoples R China Shanxi Datong Univ Inst Solid State Phys Datong 037009 Peoples R China Xi An Jiao Tong Univ Sch Elect & Informat Engn Inst Space Opt Xian 710049 Shaanxi Peoples R China

A modified Sagnac imaging spectropolarimeter is conceptually described. It consists of a spectral-polarimetric modulator, a modified Sagnac interferometer with large optical path difference, and a CCD camera. This design modulates the Stokes components of the input light into different wave numbers and obtains the modulated interferogram in snapshot mode, and the spectra or the Stokes components can be separated awl demodulated from the interferogram. The performance of the system is demonstrated through a numerical simulation, and a novel method is proposed to detect the polarization parameters including the degree of polarization and polarization direction for eliminating the aliasing effects between linear Stokes parameters. Compared with the existing imaging spectrometers, the modified Sagnac imaging spectropolarimeter can acquire one-dimensional spatial information and its full linear spectropolarimetric information in one exposure, and sonic other spatial information can be obtained by push-broom mode.

关键词： Imaging and optical processing Modulation and optical transfer functions image forming and processing

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Design and fabrication of different types of holographic lenses, with analysis of their imagery and aberration

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MEASUREMENT SCIENCE AND TECHNOLOGY 2017年第12期28卷 125402-125402页

作者： Ghosh, Abhijit Nirala, A. K. Indian Sch Mines Indian Inst Technol Dept Appl Phys Biomed Opt Lab Dhanbad 826004 Jharkhand India

In this communication we have experimentally investigated and realized the following for the first time to the best of our information: two new types of hololenses;three compact two hololens imaging systems consisting of one each of the first and second type, one each of the second and first type, and two of the second type for coherent one to one imagery;and three compact four hololens imaging systems consisting of two of each of the first and second types, two of each of the second and first type, and four of the second type to form low f-number imaging systems. In addition, problems with the existing two hololens and four hololens imaging systems are discussed in the present study and a modified geometry is proposed with supporting mathematical analysis and experimental evidence. To reduce the problems of alignment difficulty, degrees of freedom and bulkiness associated with two hololens imaging systems, a third type of hololens is also reported, which can perform coherent one to one imagery by itself. All the imaging systems consisting of hololenses can perform imaging free from almost all monochromatic aberration for the conditions under which they were recorded. Complete analyses of recording, playback, imagery and aberration for all the hololenses and the compact two and four hololens imaging systems are performed. The resolution of all three types of hololenses is found to be 57 lines mm(-1), whereas the resolution of the compact two hololens imaging systems is 32 lines mm(-1). The average diameter of the focused spots of the first, second and third type of hololens are experimentally found to be 344.45 mu m, 339.75 mu m and 190.22 mu m respectively.

关键词： holographic optical element optical system design image forming and processing diffraction efficiency resolution

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Vectorial optical vortex filtering for edge enhancement

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JOURNAL OF OPTICS 2016年第3期18卷

作者： Zhang, Baoxian Chen, Zhaozhong Sun, Hao Xia, Jianpei Ding, Jianping Nanjing Univ Natl Lab Solid State Microstruct Nanjing 210093 Jiangsu Peoples R China Nanjing Univ Sch Phys Nanjing 210093 Jiangsu Peoples R China

We propose to use a super-structured waveplate (called an S-waveplate) for vectorial optical vortex filtering, and experimentally demonstrate the radial Hilbert transform and selective edge enhancement. Based on the Jones calculus of polarization states and Fourier analysis, we calculate and analyze the point spread function of an optical 4-f system including an S-waveplate filter having the vectorial vortex of topological charge 1 (TC = 1). Numerical simulations and optical experiments demonstrate that a vectorial optical vortex filter can be used to implement selective edge enhancement with an analyzer before the output plane. The edge enhancement can be obtained even when the center of the filter is off-axis or the illuminating light is non-monochromatic.

关键词： image forming and processing polarization optical vortices

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Second-order self-imaging with parametric amplification four-wave mixing

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LASER PHYSICS LETTERS 2016年第7期13卷

作者： Wen, Feng Zhang, Zhaoyang Ahmed, Irfan Li, Zepei Wang, Hongxing Liu, Zongchen Gao, Hong Zhang, Yanpeng Xi An Jiao Tong Univ Minist Educ Key Lab Phys Elect & Devices Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Sci Xian 710049 Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Informat Photon Tech Xian 710049 Peoples R China Sukkur IBA Dept Elect Engn Sukkur 65200 Pakistan Xi An Jiao Tong Univ Sch Elect & Informat Engn Inst Wide Bandgap Semicond Xian 710049 Peoples R China

By modulating the emission characteristics of a twin-correlated bright beam in a parametric amplification of the four-wave mixing process, a nondestructive and lensless imaging scheme to image ultra-cold atoms or molecules is proposed. The optical lattice state, which is induced via the coupling between ultra-cold atoms and a standing wave, is used to effectively modulate the dressing-suppressed/enhanced nonlinear susceptibility, and an emission-intensity-modulated grating of a correlated bright beam is formed. The intensity fluctuations of the correlated bright beam are taken as the imaging light to implement second-order coincidence measurement. As an important complementary scheme to a previous self-imaging scheme with spontaneous parametric down-conversion, our scheme has the characteristic of an efficient generation and detection rate. In addition, the visibility of the imaging can be significantly improved by enhanced nonlinear susceptibility. Our work may offer a nondestructive and lensless way to image ultra-cold atoms or molecules.

关键词： image forming and processing quantum fluctuations electromagnetically induced transparency optical parametric amplifiers

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Ghost imaging based on Pearson correlation coefficients

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Chinese Physics B 2015年第5期24卷 340-345页

作者：俞文凯姚旭日刘雪峰李龙珍翟光杰 Key Laboratory of Electronics and Information Technology for Space System Center for Space Science and Applied ResearchChinese Academy of Sciences University of Chinese Academy of Sciences

Correspondence imaging is a new modality of ghost imaging, which can retrieve a positive/negative image by simple conditional averaging of the reference frames that correspond to relatively large/small values of the total intensity measured at the bucket detector. Here we propose and experimentally demonstrate a more rigorous and general approach in which a ghost image is retrieved by calculating a Pearson correlation coefficient between the bucket detector intensity and the brightness at a given pixel of the reference frames, and at the next pixel, and so on. Furthermore, we theoretically provide a statistical interpretation of these two imaging phenomena, and explain how the error depends on the sample size and what kind of distribution the error obeys. According to our analysis, the image signal-to-noise ratio can be greatly improved and the sampling number reduced by means of our new method.

关键词： coherence image forming and processing probability theory

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Sub-Rayleigh limit imaging via intensity correlation measurements

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Chinese Physics B 2015年第4期24卷 211-214页

作者：姚旭日李龙珍刘雪峰俞文凯翟光杰 Key Laboratory of Electronics and Information Technology for Space System Center for Space Science and Applied ResearchChinese Academy of Sciences University of Chinese Academy of Sciences

We demonstrate sub-Rayleigh limit imaging of an object via intensity correlation measurements. The image com- pletely unaffected by the disturbance of diffraction-limit is achieved under the condition that the imaging system has an appropriate field of view. The resolution of this sub-Rayleigh limit imaging system is only tied to the lateral resolution of the illumination light.

关键词： image forming and processing speckle

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Extended focused imaging in digital holography by spatial-domain mask method

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JOURNAL OF OPTICS 2015年第12期17卷

作者： Mori, Yutaka Fukuoka, Takahiko Nomura, Takanori Kagawa Univ Fac Engn Takamatsu Kagawa 7610396 Japan Wakayama Univ Grad Sch Syst Engn Wakayama 6408510 Japan Wakayama Univ Fac Syst Engn Wakayama 6408510 Japan

In a digital holographic reconstruction, only images located at the reconstruction distance are in focus. A speckle reduction technique is proposed to improve digital holographic in-focus imaging. The extended focused image is obtained from a depth map created by evaluating the edge sharpness of object images. In order to show the performance and effectiveness of the proposed technique for extended focused imaging, we conducted the demonstration experiments using two objects, which are a resolution chart and two screws.

关键词： interference image forming and processing holography beam trapping self-focusing and defocusing self-phase modulation

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