共查询到20条相似文献,搜索用时 156 毫秒
1.
2.
3.
4.
5.
叠层成像技术是近年来发展快速的相干衍射成像方法,目前已经成为世界上大多数X射线同步加速器和国家实验室不可或缺的成像工具。光学叠层成像是叠层成像技术在可见光波段的应用,分为基于透镜的傅里叶叠层成像与基于无透镜的编码叠层成像。编码叠层成像作为一种新型无透镜片上显微成像技术,具有大视场、高分辨率、无像差、无标记、便携式,以及缓变相位成像等诸多技术优点。本文介绍无透镜编码叠层显微成像的基本原理及最新研究进展,分析了其成像性能,重点介绍了其在生物医学方面的相关应用,并讨论了编码叠层成像技术未来的发展方向。 相似文献
6.
数字全息显微系统的成像分辨率分析 总被引:11,自引:1,他引:11
根据成像理论和全息系统的点扩散函数,研究了数字全息显微系统的成像分辨率,给出了无预放大和有预放大情况下成像分辨率的表达式,指出了只有当CCD的成像分辨率等于或高于显微物镜(MO)的成像分辨率时,预放大数字全息系统的成像分辨率才取决于显微物镜的数值孔径(NA);反之,系统的成像分辨率则取决于CCD的数值孔径。采用无透镜傅里叶变换全息记录光路,对美国空军分辨率测试板进行了实验研究,结果表明再现像在水平和垂直方向的极限分辨率分别为3.91μm和4.38μm,与理论分析相吻合。对条纹物体进行了全息图的模拟记录和再现,结果与理论分析相一致。 相似文献
7.
徐洋满天龙万玉红 《激光与光电子学进展》2017,(9):23-32
光学显微成像技术可以用来观察微小物体的结构细节,但在生物样品的显微成像领域中,像差的存在使得任何显微成像技术的成像质量都无法达到理论预期。为了解决这一问题,自适应光学技术被应用于不同类型的显微成像系统中进行像差的探测和校正。着重总结了自适应宽场高分辨率显微成像技术的研究动态,阐明了数字全息自适应光学技术和非相干数字全息自适应光学技术的特点、优势以及存在的问题。 相似文献
8.
傅里叶叠层显微术(Fourier ptychographic microscopy,FPM)是一极具前景的计算成像技术,它具有高分辨率、大视场、无标记和定量相位等优势。由于它灵活的系统、高对比度的成像结果、无需干涉装置和光源机械扫描部件,在数字病理学、体外细胞无标记观察和实时监测等方面得到了大量的研究和应用。文中主要介绍了FPM技术的系统误差校正方法、基于FPM的高通量显微成像和高速显微成像技术研究的基本原理、研究现状和最新进展,提出了目前面临的问题以及未来的发展趋势。 相似文献
9.
无衍射光束近年来广受关注,其无衍射、自修复和自加速的传播特性在微观成像应用中显示出潜在的优势。无衍射特性可抑制光束在传播过程中的衍射,有助于提升成像的分辨率。自修复特性可使光束在透过强散射介质后快速恢复波前,提高成像景深和信噪比。自加速特性可增加光场信息的有效探测维度,实现多维重构成像。本综述结合几类生物显微成像技术特点,介绍以贝塞尔光束、艾里光束为代表的无衍射光束在高分辨生物显微成像中的应用研究进展。 相似文献
11.
12.
13.
Byeong Gi Lee Seok Chang Kim 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1995,83(10):1399-1428
This paper discusses recent advances in the theory and applications of scrambling techniques for digital lightwave transmission. It introduces the theories of sequence space and shift register generator (SRG) space which enable systematic analysis and mathematical manipulation of the behavior of sequences in general and the related SRG's. It discusses the behavior and realization of frame synchronous scrambling (FSS) and distributed sample scrambling (DSS) with emphasis on parallel sequences and the related parallel SRG's (PSRG). In addition, it describes self synchronous scrambling (SSS). Then the paper applies the theories to today's lightwave transmission systems by demonstrating practical parallel designs of FSS for SDH/SONET transmission, DSS for cell-based ATM transmission, and SSS for SDH-based ATM transmission. It finally considers how DSS can be used for scrambling of mixed isochronous and nonisochronous data in future high-speed data networks. The paper employs various new concepts and terminology, such as PSRG engine, generating vector discrimination matrix, (M,N) PSRG, sampling vector, correction vector, correction matrix, predictable scrambling concurrent sampling, and immediate correction 相似文献
14.
Wavelet footprints: theory, algorithms, and applications 总被引:5,自引:0,他引:5
Wavelet-based algorithms have been successful in different signal processing tasks. The wavelet transform is a powerful tool because it manages to represent both transient and stationary behaviors of a signal with few transform coefficients. Discontinuities often carry relevant signal information, and therefore, they represent a critical part to analyze. We study the dependency across scales of the wavelet coefficients generated by discontinuities. We start by showing that any piecewise smooth signal can be expressed as a sum of a piecewise polynomial signal and a uniformly smooth residual (Theorem 1). We then introduce the notion of footprints, which are scale space vectors that model discontinuities in piecewise polynomial signals exactly. We show that footprints form an overcomplete dictionary and develop efficient and robust algorithms to find the exact representation of a piecewise polynomial function in terms of footprints. This also leads to efficient approximation of piecewise smooth functions. Finally, we focus on applications and show that algorithms based on footprints outperform standard wavelet methods in different applications such as denoising, compression, and (nonblind) deconvolution. In the case of compression, we also prove that at high rates, footprint-based algorithms attain optimal performance (Theorem 3). 相似文献
15.
Jie Song Pengyi Zhang Mohammed Alkubati Yubin Bao Ge Yu 《Digital Communications & Networks》2022,8(4):466-475
Due to the complexity of blockchain technology, it usually costs too much effort to build, maintain and monitor a blockchain system that supports a targeted application. To this end, the emerging “Blockchain as a Service” (BaaS) makes the blockchain and distributed ledgers more accessible, particularly for businesses, by reducing costs and overheads. BaaS combines the high computing power of cloud computing, the pervasiveness of IoT and the decentralization of blockchain, allowing people to build their own applications while ensuring the transparency and openness of the system. This paper surveys the research outputs of both academia and industry. First, it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision, roles, container and virtualization, interfaces, customization and evaluation. The typical applications of BaaS in both academic and practical domains are also introduced. At present, the research on the blockchain is abundant, but research on BaaS is still in its infancy. Six challenges of BaaS are concluded in this paper for further study directions. 相似文献
16.
Se-Joong Lee Kangmin Lee Seong-Jun Song Hoi-Jun Yoo 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2005,52(6):308-312
Increasing complexity of a system-on-chip design demands efficient on-chip interconnection architecture such as on-chip network to overcome limitations of bus architecture. In this brief, we propose a packet-switched on-chip interconnection network architecture, through which multiple processing units of different clock frequencies can communicate with each other without global synchronization. The architecture is analyzed in terms of area and energy consumption, and implementation issues on building blocks are addressed for cost-effective design. A test chip is implemented using 0.38-/spl mu/m CMOS technology, and measured its operation at 800 MHz to demonstrate its feasibility. 相似文献
17.
A novel phase-locked loop scheme is proposed, the main application of which is in on-chip tuning circuits. It involves the use of a variable gain amplifier and also a frequency tunable loop filter, providing infinite hold-in range, a fractionally constant pull-out range and also a fractionally constant ripple 相似文献
18.
Sidles J.A. Garbini J.L. Dougherty W.M. Shih-Hui Chao 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(5):799-816
Thermal fluctuations generate magnetic noise in the vicinity of any conductive and/or magnetically permeable solid. This magnetic noise plays a fundamental role in the design of spintronic devices: namely, it sets the time scale during which electron spins retain their coherence. This paper presents a rigorous classical and quantum analysis of thermal magnetic noise, together with practical engineering examples. Starting with the fluctuation-dissipation theorem and Maxwell's equations, a closed-form expression for the spectral density of thermal magnetic noise is derived. Quantum decoherence, as induced by thermal magnetic noise, is analyzed via the independent oscillator heat bath model of Ford et al. The resulting quantum Langevin equations yield closed-form expressions for the spin relaxation times. For realistic experiments in spintronics, magnetic resonance force microscopy, Bose-Einstein condensates, atomic physics, and solid-state quantum computing, the predicted relaxation rates are rapid enough that substantial experimental care must be taken to minimize them. At zero temperature, the quantum entanglement between a spin state and a thermal reservoir is computed. The same Hamiltonian matrix elements that govern fluctuation and dissipation are shown to also govern entanglement and renormalization, and a specific example of a fluctuation-dissipation-entanglement theorem is constructed. We postulate that this theorem is independent of the detailed structure of thermal reservoirs, and therefore expresses a general thermodynamic principle. 相似文献
19.
Single-event transient (SET) induced soft errors are becoming more and more a threat to the reliability of electronic systems in space. The SET pulse width is an important parameter characterizing the possibility of an SET being latched by a sequential element such as a flip-flop. This paper improves the widely used on-chip self-triggered SET measurement circuit by changing it from a single SET measurement module to a combination of two modules. One module is responsible for measuring narrow SET pulse widths while the other is responsible for measuring modest and wide SET pulse widths. In this way, the range of measurable SET pulse width is increased. Pulsed laser facility is used to simulate single-event transients induced by single-particles. Experimental results demonstrate that the minimum accurately measured SET pulse width is decreased from 166.5 ps to 33.3 ps after adopting the proposed design when compared with the original one. SET pulse width broadening effect was also observed using the measurement system. The broadening factor was measured to be 0.123–0.143 ps/inverter. 相似文献
20.
Eddy currents: theory and applications 总被引:2,自引:0,他引:2
Kriezis E.E. Tsiboukis T.D. Panas S.M. Tegopoulos J.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1992,80(10):1559-1589
The theory and applications of eddy currents induced in conducting materials by time-varying magnetic fields are reviewed. The mathematical methods employed in solving the relevant problems are presented. Both analytical and numerical methods are described. Applications based on effects arising from eddy currents are discussed in detail. These applications are to magnetic levitation, electromagnetic launching, hyperthermia treatment of cancer, and nondestructive testing 相似文献