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Finite element simulation of light transfer in turbid media under structured illumination

APPLIED OPTICS 2017年第21期56卷 6035-6042页

作者： Hu, Dong Lu, Renfu Ying, Yibin Zhejiang Univ Coll Biosyst Engn & Food Sci 866 Yuhangtang Rd Hangzhou 310058 Zhejiang Peoples R China ARS USDA 524 S Shaw Lane E Lansing MI 48824 USA Michigan State Univ Biosyst & Agr Engn 524 S Shaw Lane E Lansing MI 48824 USA Zhejiang A&F Univ Coll Engn 88 Huanchengbei RdHangzhou Rdngzhou 311300 Zhejiang Peoples R China

The spatial-frequency domain (SFD) imaging technique allows us to estimate the optical properties of biological tissues in a wide field of view. The technique is, however, prone to error in measurement because the two crucial assumptions used for deriving the analytical solution to the diffusion approximation cannot be met perfectly in practical applications. This research mainly focused on modeling light transfer in turbid media under the normal incidence of structured illumination using the finite element method ( FEM). Finite element simulations were performed for 50 simulation samples with different combinations of optical absorption and scattering coefficients for varying spatial frequencies, and the results were then compared with the analytical method and Monte Carlo simulation. Relationships between diffuse reflectance and dimensionless absorption and dimensionless scattering coefficients were investigated. The results indicated that the FEM provided reasonable results for diffuse reflectance, compared with the analytical method. Both the FEM and the analytical method overestimated the reflectance for mu(tr)/f(x) values of greater than 2 and underestimated the reflectance for mu(tr)/f(x) values of smaller than 2. Larger values of mu(s)'/mu(a) yielded better diffuse reflectance estimations than did those of smaller than 10. The reflectance increased nonlinearly with the dimensionless scattering, whereas the reflectance decreased linearly with the dimensionless absorption. It was also observed that diffuse reflectance was relatively stable and insensitive to mu(s)' when the dimensionless scattering was larger than 50. Overall results demonstrate that the FEM is effective for modeling light transfer in turbid media and can be used to explore the effects of crucial parameters for the SFD imaging technique. (C) 2017 Optical Society of America

关键词： computation methods Diffuse reflectance Multiple scattering Spatial frequency Tissue optical properties Turbid media

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3D reconstruction of cystoscopy videos for comprehensive bladder records

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BIOMEDICAL OPTICS EXPRESS 2017年第4期8卷 2106-2123页

作者： Lurie, Kristen L. Angst, Roland Zlatev, Dimitar V. Liao, Joseph C. Bowden, Audrey K. Ellerbee Stanford Univ Dept Elect Engn Stanford CA 94305 USA Stanford Univ Dept Urol Stanford CA 94305 USA Max Planck Inst Saarbracecken Germany

White light endoscopy is widely used for diagnostic imaging of the interior of organs and body cavities, but the inability to correlate individual 2D images with 3D organ morphology limits its utility for quantitative or longitudinal studies of disease physiology or cancer surveillance. As a result, most endoscopy videos, which carry enormous data potential, are used only for real-time guidance and are discarded after collection. We present a computational method to reconstruct and visualize a 3D model of organs from an endoscopic video that captures the shape and surface appearance of the organ. A key aspect of our strategy is the use of advanced computer vision techniques and unmodified, clinical-grade endoscopy hardware with few constraints on the image acquisition protocol, which presents a low barrier to clinical translation. We validate the accuracy and robustness of our reconstruction and co-registration method using cystoscopy videos from tissue-mimicking bladder phantoms and show clinical utility during cystoscopy in the operating room for bladder cancer evaluation. As our method can powerfully augment the visual medical record of the appearance of internal organs, it is broadly applicable to endoscopy and represents a significant advance in cancer surveillance opportunities for big-data cancer research. (C) 2017 Optical Society of America

关键词： computation methods Image quality Machine vision Medical image processing Optical coherence tomography White light

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3D cost aggregation with multiple minimum spanning trees for stereo matching

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APPLIED OPTICS 2017年第12期56卷 3411-3420页

作者： Li, Lincheng Yu, Xin Zhang, Shunli Zhao, Xiaolin Zhang, Li Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China Australian Natl Univ Coll Engg & Comp Sci Canberra ACT 2601 Australia Beijing Jiaotong Univ Sch Software Engn Beijing 100044 Peoples R China Airforce Engn Univ Sch Aeronaut & Astronaut Engn Xian 710038 Peoples R China

Cost aggregation is one of the key steps in the stereo matching problem. In order to improve aggregation accuracy, we propose a cost-aggregation method that can embed minimum spanning tree (MST)-based support region filtering into PatchMatch 3D label search rather than aggregating on fixed size patches. However, directly combining PatchMatch label search and MST filtering is not straightforward, due to the extremely high complexity. Thus, we develop multiple MST structures for cost aggregation on plenty of 3D labels, and design the tree-level random search strategy to find possible 3D labels of each pixel. Extensive experiments show that our method reaches higher accuracy than the other existing cost-aggregation and global-optimization methods such as the 1D MST, the PatchMatch and the PatchMatch Filter, and currently ranks first on the Middlebury 3.0 benchmark. (C) 2017 Optical Society of America

关键词： computation methods Image processing Machine vision Neural networks Segmentation Stereo matching

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Extending capture range for piston retrieval in segmented systems

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APPLIED OPTICS 2017年第33期56卷 9186-9192页

作者： Paine, Scott W. Fienup, James R. Univ Rochester Inst Opt Rochester NY 14627 USA

Image-based wavefront sensing is a powerful technique for measuring the aberrations of optical systems and surfaces. It often fails for segmented systems with large piston errors per segment. We propose a method for finding these errors using broadband light and a specialized grid search as part of a more global search. We show that this method has a high rate of success for a case where nonlinear optimization gets stuck in local minima. We also explore points of failure. (C) 2017 Optical Society of America

关键词： computation methods Optical aberrations Optical surfaces Phase retrieval Space telescopes Wave front sensing

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Parameterization of the deterministic Mueller matrix: application to a uniform medium

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2017年第4期34卷 602-608页

作者： Sheppard, Colin J. R. Ist Italiano Tecnol Nanoscopy Grp Dept Nanophys I-16163 Genoa Italy

The extraction of the elementary polarization properties of a uniform medium from a deterministic Mueller matrix has been considered by several researchers. The relationship between a parameterization of the deterministic Mueller matrix that we described recently and the elementary polarization properties for a uniform medium is investigated. The elementary polarization properties can be calculated exactly from the Mueller matrix parameters. Simplified forms for the Mueller matrix parameters in terms of the elementary polarization properties are presented. The effect on the Mueller matrix of varying the ratio of the total diattenuation to the total retardance is investigated. Approximate forms for the elementary polarization properties in terms of the Mueller matrix parameters, valid for weak optical media, are given. (C) 2017 Optical Society of America

关键词： computation methods Inverse problems Mueller matrices Optical media Polarization Wave propagation

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computational color prediction versus least-dissimilar matching

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2018年第4期35卷 B292-B298页

作者： Roshan, Emitis Funt, Brian Simon Fraser Univ Sch Comp Sci Vancouver BC V5A 1S6 Canada

The performance of color prediction methods CIECAM02, KSM2, Waypoint, Best Linear, Metamer Mismatch Volume Center, and Relit color signal are compared in terms of how well they explain Logvinenko and Tokunaga's asymmetric color matching results [Seeing Perceiving 24, 407 (2011)]. In their experiment, four observers were asked to determine (three repeats) for a given Munsell paper under a test illuminant which of 22 other Munsell papers was the least-dissimilar under a match illuminant. Their use of "least-dissimilar" as opposed to "matching" is an important aspect of their experiment. Their results raise several questions. Question 1: Are observers choosing the original Munsell paper under the match illuminant? If they are, then the average (over 12 matches) color signal (i.e., cone LMS or CIE XYZ) made under a given illuminant condition should correspond to that of the test paper's color signal under the match illuminant. computation shows that the mean color signal of the matched papers is close to the color signal of the physically identical paper under the match illuminant. Question 2: Which color prediction method most closely predicts the observers' average least-dissimilar match? Question 3: Given the variability between observers, how do individual observers compare to the computational methods in predicting the average observer matches? A leave-one-observer-out comparison shows that individual observers, somewhat surprisingly, predict the average matches of the remaining observers better than any of the above color prediction methods. (c) 2018 Optical Society of America

关键词： Color computation methods Computer simulation Illuminants Illumination Laser pointers

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Binary classification of Mueller matrix images from an optimization of Poincare coordinates

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2017年第6期34卷 983-990页

作者： Kupinski, Meredith K. Bankhead, Jaden Stohn, Adriana Chipman, Russell Univ Arizona Coll Opt Sci Tucson AZ 85721 USA

A new binary classification method for Mueller matrix images is presented which optimizes the polarization state analyzer (PSA) and the polarization state generator (PSG) using a statistical divergence between pixel values in two regions of an image. This optimization generalizes to multiple PSA/PSG pairs so that the classification performance as a function of number of polarimetric measurements can be considered. Optimizing PSA/PSG pairs gives insight into which polarimetric measurements are most useful for the binary classification. For example, in scenes with strong diattenuation, retardance, or depolarization certain PSA/PSG pairs would make two regions in an image look very similar and other pairs would make the regions look very different. The method presented in this paper provides a quantitative method for ensuring the images acquired can be classified optimally. (C) 2017 Optical Society of America

关键词： computation methods Medical imaging Mueller matrices Optical elements Optical testing Phase sensitive amplifiers

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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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Material point method for simulating nonequilibrium thermal transport in metals irradiated by ultrafast lasers

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2017年第11期34卷 2334-2342页

作者： Gan, Yong Lei, Chunxia Sun, Zheng Zhejiang Univ Fac Engn Hangzhou 310027 Zhejiang Peoples R China Beijing Inst Technol State Key Lab Explos Sci & Technol Beijing 100081 Peoples R China

A material point method (MPM) for the analysis of two-step heating of metals subjected to ultrafast laser irradiation is developed based on the weak formulation of the two-temperature model (TTM). The electron and lattice subsystems in the metallic targets are both represented by a finite number of Lagrangian material points to discretize the TTM equations, while a background Eulerian grid mesh is used to solve the spatially discrete TTM equations for the electron and lattice temperatures carried by the material points. The verification, convergence, and robustness of the proposed MPM method are demonstrated using representative examples for femto/picosecond laser heating of a gold thin film. In addition to avoiding the numerical difficulties due to the mesh distortion and entanglement in the mesh-based method, the presented MPM algorithm automatically handles the adiabatic boundary condition without requiring additional boundary treatments and could achieve higher computational efficiency than the mesh-based approaches at a comparable level of accuracy, showing its advantage over the mesh-based methods for modeling energy transfer in metals irradiated by ultrafast lasers. (C) 2017 Optical Society of America

关键词： computation methods Energy transfer Frequency division multiplexing Laser energy Laser irradiation Ultrafast lasers

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Spectral element boundary integral method with periodic layered medium dyadic Green's function for multiscale nano-optical scattering analysis

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OPTICS EXPRESS 2017年第20期25卷 24199-24214页

作者： Niu, Jun Ren, Yi Liu, Qing Huo Duke Univ Dept Elect & Comp Engn Durham NC 27708 USA Chongqing Univ Posts & Telecommun Sch Elect Engn Chongqing 400065 Peoples R China

In this work, we propose a numerical solver combining the spectral element - boundary integral (SEBI) method with the periodic layered medium dyadic Green's function. The periodic layered medium dyadic Green's function is formulated under matrix representation. The surface integral equations (SIEs) are then implemented as the radiation boundary condition to truncate the top and bottom computation domain. After describing the interior computation domain with the vector wave equations, and treating the lateral boundaries with Bloch periodic boundary conditions, the whole computation domains are discretized with mixed-order Gauss-Lobatto-Legendre basis functions in the SEBI method. This method avoids the discretization of the top and bottom layered media, so it can be much more efficient than conventional methods. Numerical results validate the proposed solver with fast convergence throughout the whole computation domain and good performance for typical multiscale nano-optical applications. (C) 2017 Optical Society of America

关键词： computation methods Electric fields Electromagnetic scattering Extreme ultraviolet lithography Finite difference time domain Finite element method

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