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Wave atoms for digital hologram compression

APPLIED OPTICS 2019年第22期58卷 6193-6203页

作者： Birnbaum, Tobias Ahar, Ayyoub Blinder, David Schretter, Colas Kozacki, Tomasz Schelkens, Peter VUB Dept Elect & Informat ETRO Brussels Belgium VUB IMEC Brussels Belgium Warsaw Univ Technol Inst Micromech & Photon Warsaw Poland

Compression of macroscopic digital holograms is a major research problem, which if unresolved will continue to limit the possible applications of holography in multimedia contexts. The quest of searching for the most suitable representation for compression is still an open problem. In this work, we study sparsification by the wave atom transform, introduced in 2006 by Demanet et al., and experiment on four large-scale representative diffuse macroscopic holograms while testing compressibility in the object plane, Fourier plane, and defocused plane representations, respectively. We demonstrate that it is a suitable nonadaptive, sparsifying transform for Fourier or defocused content, and by integration into the wave atom coding (WAC) method, we sketch a full-fledged codec for the compression of macroscopic holograms. WAC is compared to two variants of JPEG 2000, with equal complexity of coding tools, and the more recent High Efficiency Video Coding (H.265/HEVC). For Fourier and defocused holograms, WAC outperforms the JPEG 2000 variants by 0.9-7.9 dB Biontegaard-Delta peak signal to noise ratio, especially in the former case, while it is as good as or better than even H.265/HEVC for very deep computer-generated holograms, thus improving on existing approaches. (C) 2019 Optical Society of America.

关键词： Bidirectional reflectance distribution function computation methods Digital holographic imaging Fast Fourier transforms Fourier transforms Wavelet transforms

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Derivatives of optical path length: from mathematical formulation to applications

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2015年第5期32卷 710-717页

作者： Lin, Psang Dain Natl Cheng Kung Univ Dept Mech Engn Tainan 70101 Taiwan

The optical path length (OPL) of an optical system is a highly important parameter since it determines the phase of the light passing through the system and governs the interference and diffraction of the rays as they propagate. The Jacobian and Hessian matrices of the OPL are of fundamental importance in tuning the performance of a system. However, the OPL varies as a recursive function of the incoming ray and the boundary variable vector, and hence computing the Jacobian and Hessian matrices is extremely challenging. In an earlier study by the present group, this problem was addressed by deriving the Jacobian matrix of the OPL with respect to all of the independent system variables of a nonaxially symmetric system. In the present study, the proposed method is extended to the Hessian matrix of a nonaxially symmetric optical system. The proposed method facilitates the cross-sensitivity analysis of the OPL with respect to arbitrary system variables and provides an ideal basis for automatic optical system design applications in which the merit function is defined in terms of wavefront aberrations. An illustrative example is given. It is shown that the proposed method requires fewer iterations than that based on the Jacobian matrix and yields a more reliable and precise optimization performance. (C) 2015 Optical Society of America

关键词： Mathematical methods (general) Geometric optical design Lens system design computation methods First-order optics

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Nonvolatile multi-level adjustable optical switch based on the phase change material

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OPTICS EXPRESS 2022年第20期30卷 36096-36109页

作者： Quan, Zhiqiang Wan, Yuanjian Ma, Xiaoxiao Wang, Jian Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Hubei Peoples R China Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Hubei Peoples R China Opt Valley Lab Wuhan 430074 Hubei Peoples R China Huazhong Univ Sci & Technol Sch Software Engn Wuhan 430074 Hubei Peoples R China

For the advantages of the faster computation speed and lower energy consumption, all-optical computation has attracted great attention compared with the traditional electric computation method. Optical switches are the critical elementary units of optical computation devices. However, the traditional optical switches have two shortcomings, expending the outside energy to keep the switch state and the weak multi-level adjustable ability, which greatly restrict the realization of the large-scale photonic integrated circuits and optical spiking neural networks. In this paper, we use a subwavelength grating slot-ridge (SWGSR) waveguides on the silicon platform to design a nonvolatile multi-level adjustable optical switch based on the phase change material Ge2Sb2Te5 (GST). Changing the phase state of GST can modulate the transmission of the optical switch, and the change of the optical transmittance of the optical switch is about 70%, which is much higher than that of previous optical switches. As no static power is required to maintain the phase state, it can find promising applications in optical switch matrices and reconfigurable optical spiking neural networks.(c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： computation methods Optical materials Optical networks Plasmon waveguides Stochastic gradient descent Waveguide modes

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Raman signal extraction from CARS spectra using a learned-matrix representation of the discrete Hilbert transform

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OPTICS EXPRESS 2022年第15期30卷 26057-26071页

作者： Camp, Charles H., Jr. NIST Biosyst & Biomat Div 100 Bur Dr Gaithersburg MD 20899 USA

Removing distortions in coherent anti-Stokes Raman scattering (CARS) spectra due to interference with the nonresonant background (NRB) is vital for quantitative analysis. Popular computational approaches, the Kramers-Kronig relation and the maximum entropy method, have demonstrated success but may generate significant errors due to peaks that extend in any part beyond the recording window. In this work, we present a learned matrix approach to the discrete Hilbert transform that is easy to implement, fast, and dramatically improves accuracy of Raman retrieval using the Kramers-Kronig approach.

关键词： Chemical analysis computation methods Fourier transforms High resolution spectroscopy Interference Raman scattering

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Occlusion-removed scheme using depth-reversed method in computational integral imaging

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APPLIED OPTICS 2010年第14期49卷 2571-2580页

作者： Zhang, Miao Piao, Yongri Kim, Eun-Soo Kwangwoon Univ Dept Elect Engn Display Res Ctr 3D Seoul South Korea

We present a computational scheme for removing an occlusion in a partially occluded, far object in a computational integral imaging (CII) system. In order to obtain the high resolution elemental image array (EIA) with enhanced information of the occluded image for better applying block matching, a smart pixel mapping process and a subimage transform process are adopted. Based on depth maps produced between adjacent subimages, we acquire the expected EIA without occlusion information. Theoretical analysis of the proposed scheme is given. To show the effectiveness of the proposed scheme, we carry out some experiments. As demonstrated using test images, experimental results show that the proposed scheme outperforms Shin's scheme and the CII scheme under the same situations. (C) 2010 Optical Society of America

关键词： Charge coupled devices computation methods Geometric optics Image quality Image sensors Three dimensional imaging

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Non-paraxial idealized polarizer model

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OPTICS EXPRESS 2018年第8期26卷 9840-9849页

作者： Zhang, Site Partanen, Henri Hellmann, Christian Wyrowski, Frank Friedrich Schiller Univ Jena Inst Appl Phys Appl Computat Opt Grp Albert Einstein Str 15 D-07743 Jena Germany LightTrans Int UG Kahlaische Str 4 D-07745 Jena Germany Univ Eastern Finland Yliopistokatu 2 FI-80100 Joensuu Finland Wyrowski Photon UG Kahlaische Str 4 D-07745 Jena Germany

An idealized polarizer model that works without the structural and material information is derived in the spatial frequency domain. The non-paraxial property is fully included and the result takes a simple analytical form, which provides a straight-forward explanation for the crosstalk between field components in non-paraxial cases. The polarizer model, in a 2 X 2-matrix form, can be conveniently used in cooperation with other computational optics methods. Two examples in correspondence with related works are presented to verify our polarizer model. (C) 2018 Optical Society of America

关键词： computation methods Fourier transforms Matrix methods Optical components Polarizers Spatial frequency

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Rapid parameter determination of discrete damped sinusoidal oscillations

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OPTICS EXPRESS 2021年第5期29卷 6863-6878页

作者： Visschers, Jim C. Wilson, Emma Conneely, Thomas Mudrov, Andrey Bougas, Lykourgos Johannes Gutenberg Univ Mainz Inst Phys D-55128 Mainz Germany Univ Leicester Dept Math Leicester LE1 7RH Leics England Photek Ltd St Leonards On Sea TN38 9NS E Sussex England

We present different computational approaches for the rapid extraction of the signal parameters of discretely sampled damped sinusoidal signals. We compare time- and frequency-domain-based computational approaches in terms of their accuracy and precision and computational time required in estimating the frequencies of such signals, and observe a general trade-off between precision and speed. Our motivation is precise and rapid analysis of damped sinusoidal signals as these become relevant in view of the recent experimental developments in cavity-enhanced polarimetry and ellipsometry, where the relevant time scales and frequencies are typically within the similar to 1 - 10 mu s and similar to 1 - 100 MHz ranges, respectively. In such experimental efforts, single-shot analysis with high accuracy and precision becomes important when developing experiments that study dynamical effects and/or when developing portable instrumentations. Our results suggest that online, running-fashion, microsecond-resolved analysis of polarimetric/ellipsometric measurements with fractional uncertainties at the 10(-6) levels, is possible, and using a proof-of-principle experimental demonstration we show that using a frequency-based analysis approach we can monitor and analyze signals at kHz rates and accurately detect signal changes at microsecond time-scales. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

关键词： Analog to digital converters Analytical techniques computation methods Fourier transforms Matrix methods Power spectral density

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Automatic estimation of human blood pressure based on the joint analysis of morphological and spectral parameters of the photoplethysmogram

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JOURNAL OF OPTICAL TECHNOLOGY 2020年第12期87卷 750-755页

作者： Zaluskaya, V. S. Karaseva, E. A. Lutsiv, V. R. ITMO Univ St Petersburg Russia Russian Acad Sci Pavlov Inst Physiol St Petersburg Russia St Petersburg State Univ Aerosp Instrumentat St Petersburg Russia

A method for the automatic assessment of the systolic and diastolic blood pressure of people by means of a joint analysis of spectral and morphological features of the pulse waveform on a photoplethysmogram is proposed. For extraction of the used features, algorithms have been developed for the preliminary processing of the original photoplethysmogram signal, its automatic division into periods corresponding to individual cardiac cycles, and the selection of characteristic features of the pulse waveform in each period. The selected signal periods are used to calculate the spectral characteristics of the photoplethysmogram, and the expediency of using triplets of successive cycles for this purpose is shown experimentally. The parameters calculated from the features of the pulse waveform and its calculated spectral characteristics are automatically analyzed using a specially trained artificial neural network, which forms an estimate of the patient's systolic and diastolic blood pressure at the output. The expediency of automatic determination of blood pressure based on the joint analysis of spectral and morphological characteristics of photoplethysmograms is shown experimentally. (c) 2021 Optical Society of America

关键词： Blood computation methods Electromagnetic radiation Light intensity Microoptical devices Neural networks

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Tapered simplified modal method for analysis of non-rectangular gratings

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APPLIED OPTICS 2017年第1期56卷 120-129页

作者： Li, Shuai Zhou, Changhe Barbastathis, George MIT Dept Mech Engn 77 Massachusetts Ave Cambridge MA 02139 USA Chinese Acad Sci Shanghai Inst Opt & Fine Mech Shanghai 201800 Peoples R China Singapore MIT Alliance Res & Technol SMART Ctr 1 Create Way Singapore 138602 Singapore

The simplifiedmodal method (SMM) [Opt. Quantum Electron. 37, 309 (2005)] provides a quick, intuitive way to analyze the performance of the gratings of rectangular shapes. For non-rectangular shapes, a version of SMM has been developed [Opt. Lett. 33, 1554 (2008)], but it applies only to the Littrow-mounting incidence case and neglects reflection. Here, we use the theory of mode-coupling in a tapered waveguide to improve SMM so that it applies to non-rectangular gratings at arbitrary angles of incidence. Moreover, this new tapered simplified modal method (TSMM) allows us to properly account for reflected light and requires fewer coupled guided modes to compute the correct diffracted field than required plane wave modes in rigorous coupled wave analysis (RCWA). We present here the analytical development of the theory and numerical simulations, demonstrating the validity of the method by comparing it with RCWA and the finite difference time domain method. (C) 2016 Optical Society of America

关键词： Analytical techniques Beam splitters computation methods Effective refractive index Light propagation Numerical simulation

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Dyadic Green's function of a sphere with an eccentric spherical inclusion

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2007年第6期24卷 1695-1703页

作者： Moneda, Angela P. Chrissoulidis, Dimitrios P. Aristotle Univ Thessaloniki Fac Engn Dept Elect & Comp Engn GR-54124 Thessaloniki Greece

An exact, analytical solution to the problem of point-source radiation in the presence of a sphere with an eccentric spherical inclusion has been obtained by combined use of the dyadic Green's function formalism and the indirect mode-matching technique. The end result of the analysis is a set of linear equations for the vector wave amplitudes of the electric Green's dyad. The point source can be anywhere, even within the aforesaid nonspherical body, and there is no restriction with regard to the electrical properties in any part of space. Several checks confirm that this solution obeys the energy conservation and reciprocity principles. Numerical results are presented for an electric Hertz dipole radiating from within an acrylic sphere, which contains an eccentric spherical cavity (C) 2007 Optical Society of America

关键词： Analytical techniques Antennas computation methods Electric fields Microwaves Refractive index

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