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Accepted papers to appear in an upcoming issue

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Reciprocity Theorem and Accuracy Evaluation onScattering Fields by Dielectric Gratings

Hideaki Wakabayashi, Masamitsu Asai, and Jiro Yamakita

Doc ID: 340594 Received 25 Jul 2018; Accepted 21 Sep 2018; Posted 21 Sep 2018  View: PDF

Abstract: In the theory of gratings, a diffraction solution must satisfy the energy balance and the reciprocity. Thispaper the diffraction by multilayered dielectric gratings including lossy layers of which the solutions donot satisfy the energy balance. Applying the shadow theory to the matrix eigenvalues method, the symmetryof scattering factors in the theory and that of diffraction efficiencies are shown in some formulaeand then are validated numerically. In addition, the reciprocity errors for diffraction efficiencies and scatteringfactors are newly considered as an accuracy criterion. It is shown that, on numerical calculations,the reciprocity error for diffraction efficiencies have only to be checked.

Learning Siamese Networks for Laser Vision SeamTracking

Yan Zou, Jinchao Li, Xiangzhi Chen, and Rui Lan

Doc ID: 331192 Received 07 May 2018; Accepted 20 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: To design a stable laser vision seam-tracking system, an advanced weld image processing algorithm based onSiamese networks is investigated and proposed to resist the interference of arc and spatter in the welding process.This special designed neural network, combining with powerful feature expression capabilities of deep learning,takes two welding images with different size as input and generates a target confidence map in a single forwardpass by using the cross-correlation algorithm. To prevent the error accumulation and model drift, an online updatestrategy via local cosine similarity is developed. The use of MIG welding can realize real-time and precious trackingunder the condition that the strong arc continuously shields the welding seam feature points.

Enhanced backscatter in LIDAR systems withretro-reflectors operating through a turbulent ocean

Olga Korotkova

Doc ID: 341319 Received 01 Aug 2018; Accepted 20 Sep 2018; Posted 20 Sep 2018  View: PDF

Abstract: The Enhanced BackScatter (EBS) effect is examined for light propagation through a weakly turbulentocean in a monostatic channel with a retro-reflector. Using the second-order Rytov theory to account forthe turbulent medium perturbations of the optical wave we numerically predict the appearance of theEBS in the average intensity for the incident plane and spherical waves within the first several metersof the channel. The influence of the size of the retro-reflector on the EBS factor is also revealed for bothtypes of waves. Our predictions are instrumental for the development of the LIDARs in turbulent watersfor communications, imaging and sensing.

Three-way decisions based reconstruction frame for fluorescence molecular tomography

Huangjian Yi, Pu Jiao, Xiaonan Li, Jinye Peng, and Xiaowei He

Doc ID: 341043 Received 30 Jul 2018; Accepted 18 Sep 2018; Posted 19 Sep 2018  View: PDF

Abstract: Fluorescence molecular tomography (FMT) has been a promising imaging tool because it allows an accurate localizaton and quantitative analysis of the fluorophore distribution in animals. It, however, is still a challenge since its reconstruction suffers from severe ill-posedness. This paper introduces a reconstruction frame based on three-way decisions (TWD) for the inverse problem of FMT. On the first stage, a reconstruction result on the whole region is obtained by a certain reconstruction algorithm. With TWD, the recovered result has been divided into three regions: fluorescent target region, boundary region and background region. On the second stage, the boundary region and fluorescent target region have been combined into the permissible region of target. Then a new reconstruction on the permissible region has been carried out and a new recovered result is obtained. With TWD again, the new result has been classified into three pariwise disjoint regions. And the new fluorescent target region is the final reconstructed result. Both numerical simulation experiments and real mouse experiment are carried out to validate the feasibility and potential of the presented reconstruction frame. The results indicate that the proposed reconstuction strategy based on TWD can provide a good performance in FMT reconstruction.

Observation of Mie ripples in the synchrotronFTIR spectra of spheroidal pollen grains

Reinhold Blumel, Rozalia Lukacs, Boris Zimmermann, Murat Bagcioglu, and Achim Kohler

Doc ID: 340394 Received 23 Jul 2018; Accepted 13 Sep 2018; Posted 13 Sep 2018  View: PDF

Abstract: Conceptually, biological cells are dielectric, photonic resonators that are expectedto show a rich variety of shape resonances when exposed to electromagnetic radiation. Forspheroidal cells these shape resonances may be predicted and analyzed using the Mie theory ofdielectric spheres, which predicts that a special class of resonances, i.e., Whispering GalleryModes (WGMs), causes ripples in the absorbance spectra of spheroidal cells. Indeed, the firsttentative indication of the presence of Mie ripples in the synchrotron Fourier transform infrared(SFTIR) absorbance spectra of Juniperus chinensis pollen was already reported [Analyst, 2015,140, 3273]. To show that this observation is no isolated incidence, but a generic spectral featurethat can be expected to occur in all spheroidal biological cells, we measured and analyzedthe SFTIR absorbance spectra of Cunninghamia lanceolata, Juniperus chinensis, Juniperuscommunis, and Juniperus excelsa. All four pollen species show Mie ripples. Since the WGMscausing the ripples are surface modes, we propose ripple spectroscopy as a powerful tool forstudying the surface properties of spheroidal biological cells. In addition, our paper drawsattention to the fact that shape resonances need to be taken into account when analyzing (S)FTIRspectra of isolated biological cells since shape resonances may distort the shape or mimic thepresence of chemical absorption bands.

Multiresolution based weighted regularization fordenoised image interpolation from scattered sampleswith application to confocal microscopy

Bibin Francis, manoj mathew, and Muthuvel Arigovindan

Doc ID: 332920 Received 30 May 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: The problem of reconstructing an image from non-uniformly spaced, spatial point measurements is frequentlyencountered in bio-imaging and other scientific disciplines. The most successful class of methodsin handling this problem use the regularization approach involving the minimization of a derivativebasedroughness functional. It has been well demonstrated, in the presence of noise, that non-quadraticroughness functionals such as `1 measure yield better performance compared to the quadratic ones ininverse problems in general, and in deconvolution in particular. However, for the present problem, allwell-evaluated methods use quadratic roughness measures; indeed, `1 performs worse than the quadraticroughness when the sampling density is low. This is due to the fact that the mutual incoherence betweenthe measurement operator (dirac-delta) and the regularization operator (derivative) is low in the presentproblem. Here we develop a new multiresolution based roughness functional that performs better than`1 and quadratic functionals under a wide range of sampling densities. We also propose an efficient iterativemethod for minimizing the resulting cost function. We demonstrate the superiority of the proposedregularization functional in the context of reconstructing full images from non-uniformly under-sampleddata obtained from a confocal microscope.

Maggi-Rubinowicz integral for Fraunhofer diffraction byhexagonal particles. Application to cirrus ice crystals

Olivier Pujol and Gérard Brogniez

Doc ID: 335757 Received 20 Jun 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: This paper is devoted to Fraunhofer diffraction by hexagonal ice crystals like those that can be encoun-tered in cirrus clouds. Such crystals are important, for they are the basic building elements of crystalsof more complex shape. A new alternative based on the Maggi-Rubinowicz transformation is proposed.This technique, whose basic formula is a line integral version of the Kirchhoff integral, is very easy to im-plement and is not time consuming. Diffraction patterns of hexagonal ice crystals with (i) fixed arbitraryorientation, (ii) random orientation, and (iii) preferred orientation are given. The topic is of importancesince the radiative impact of cirrus clouds, which depends directly on ice crystal optical properties, is stilla challenging problem in climate research.

Techniques for Arbitrary Sampling in 2D Fourier Transforms

Alden Jurling, Matthew Bergkoetter, and James Fienup

Doc ID: 326354 Received 15 Jun 2018; Accepted 09 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: In this paper we discuss two effective methods for computing optical propagations using two dimensional discrete Fourier transforms: the matrix triple product (MTP) and the chirp z-transform (CZT) and analyze their performance both in theory and via benchmarks compared to the performance of a traditional padded fast Fourier transform (FFT). We show that, in many regimes of interest for phase retrieval algorithms, the MTP or CZT are comparable to or better than the FFT in terms of run time while offering more flexible control over the sampling. We propose that for many applications the CZT makes a robust general purpose alternative to the padded 2D FFT.

First-order nonparaxial scalar theory of surface and bulk scattering for high-quality optical coatings

Zhang Kepeng, Renshuai Huang, Xiaoxi Tian, Yinhua Zhang, Huang Wei, and Chunlin Guan

Doc ID: 332855 Received 12 Jun 2018; Accepted 07 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: A nonparaxial scalar theory is presented to calculate the angular scattering that is due to interface roughnesses or bulk inhomogeneities in a high-quality multilayer coating. Based on the empirically modified Beckmann-Kirchhoff theory, this theory provides new understanding and insight into multilayer scattering phenomena. It is interesting to note that the theory in surface scattering and bulk scattering predicts similar expressions for the angular scattered intensities and these expressions are in the same form as those given by the typical vector methods. Based on theoretical calculations and comparisons with the corresponding typical models for several multilayer designs, the surface and bulk models that we derive are demonstrated to be valid even for the case of large angles of incidence and scattering.

Photon-efficiency of computational ghost imaging with single-photon detection

Xialin Liu, Yiwei Sun, Jianhong Shi, and Guihua Zeng

Doc ID: 337973 Received 05 Jul 2018; Accepted 06 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: Photon-limited imaging has significant application under extreme environments, in which the photon-efficiency is an important parameter. In this paper, we investigate the photon-efficiency of computational ghost imaging with single-photon detection. By exploiting the Poisson statistical characteristics of single photon counting, the relationships between the photon-efficiency and the signal-to-noise ratio of the retrieved image is theoretically obtained, and both of them are closely related to the distribution characteristics of target and spatial modulation in ghost imaging framework. To verify the availability of the built theoretical model for the photon-efficiency, a specific computational ghost imaging with a binary object and the first-photon imaging algorithm is rigorously demonstrated in theory and in experiment. Our investigation paves a way for the optimization of photon-limited ghost imaging.

Rsp ratio approach for evaluation of scotopic/photopicratios of light sources performance at varying CCTs

Qi Yao and Yi Lin

Doc ID: 332216 Received 21 May 2018; Accepted 05 Sep 2018; Posted 07 Sep 2018  View: PDF

Abstract: Scotopic/photopic ratio (S/P ratio, or Rsp) is an absolute measure of light sources’ performance under the mesopic visionstate. However, there are more potentials for light sources to reach higher mesopic performance at higher correlated colortemperatures (CCTs) and these cannot be evaluated. We proposed a Rsp ratio metric to examine relative performance of S/Pratio at corresponding CCT. Based on an examination of a large set of light sources, we established the Rsp - CCT and Rspratio - CCT relations of different light sources types. On investigating previously reported high S/P ratio light sources withthe proposed metric, it shows high effectiveness in evaluating relative mesopic performance as considering CCT issues.

Cone and melanopsin contributions to humanbrightness estimation: Reply

Andrew Zele, Prakash Adhikari, Beatrix Feigl, and Dingcai Cao

Doc ID: 340852 Received 26 Jul 2018; Accepted 05 Sep 2018; Posted 10 Sep 2018  View: PDF

Abstract: Our analytical description of full-field brightness perception data [J. Opt. Soc. Am. A 35, B19-B25 (2018)] withcontributions from cone luminance and melanopsin expressing intrinsically photosensitive retinal ganglioncells has been extended [J. Opt. Soc. Am. A 35, Bullough Reference details (2018)] to include S-cones through ablue-yellow opponent channel. We welcome this reanalysis and provide a few remarks on the approach.

Fresnel diffraction analysis of Ronchi and reverse Hartmann tests

Francois Henault

Doc ID: 332950 Received 31 May 2018; Accepted 04 Sep 2018; Posted 05 Sep 2018  View: PDF

Abstract: In this paper is presented a Fresnel diffraction analysis of classical Ronchi and reverse Hartmann tests. Simplified analytical expressions of the intensity patterns observed by the camera are established, allowing quantitative measurements of the wavefront slopes of the tested optical system. Wavefront are then reconstructed from their slopes using a double Fourier transform algorithm. The optimization of the operational parameters of the system is discussed in view of different quality criteria, including relative pupil shear and contrast factors in both monochromatic and polychromatic light. Practical examples of applications are studied with the help of numerical simulations, demonstrating that measurement accuracies better than /100 RMS are achievable on properly dimensioned systems. Finally, the technique is also applicable to wavefront sensing in adaptive optics systems

Multiple invisibility regions induced by symmetrybreaking in a trimer of subwavelength graphene-coatednanowires

Volodymyr Fesenko, Vitalii Shcherbinin, and Vladimir Tuz

Doc ID: 336036 Received 25 Jun 2018; Accepted 30 Aug 2018; Posted 31 Aug 2018  View: PDF

Abstract: Electromagnetic response is studied for clusters of subwavelength graphene-coated nanowires illuminatedby a linearly polarized plane wave in the terahertz frequency range. The solution of the scatteringproblem is obtained with the Lorenz-Mie theory and the multiple cylinder scattering formalism. The resultsshow that normalized scattering cross-sections of nanowire clusters can be drastically changed bythe symmetry breaking introduced into the cluster’s design. This effect is due to excitation of dark modesand is observed only for the incident wave of TE-polarization.

X-ray tomography of extended objects: a comparison of data acquisition approaches

Ming Du, Rafael Vescovi, Kamel Fezzaa, Chris Jacobsen, and Doga Gursoy

Doc ID: 331496 Received 11 May 2018; Accepted 03 Aug 2018; Posted 06 Aug 2018  View: PDF

Abstract: The penetration power of x-rays allows one to image large objects. For example, centimeter-sized specimens can be imaged with micron-level resolution using synchrotron sources. In this case, however, the limited beam diameter and detector size preclude the acquisition of the full sample in a single take, necessitating strategies for combining data from multiple regions. Object stitching involves the combination of local tomography data from overlapping regions, while projection stitching involves the collection of projections at multiple offset positions from the rotation axis followed by data merging and reconstruction. We compare these two approaches in terms of radiation dose applied to the specimen, and reconstructed image quality. Object stitching involves an easier data alignment problem, and immediate viewing of subregions before the entire dataset has been acquired. Projection stitching is more dose-efficient, and avoids certain artifacts of local tomography; however, it also involves a more difficult data assembly and alignment procedure, in that it is more sensitive to accumulative registration error.

Cone and melanopsin contributions to human brightness estimation: Comment

John Bullough

Doc ID: 326384 Received 26 Mar 2018; Accepted 15 Jun 2018; Posted 10 Sep 2018  View: PDF

Abstract: A recent study of large-field subjective brightness perception under different narrowband spectra and different luminances revealed distinct contributions of cone photoreceptors and intrinsically-photosensitive retinal ganglion cells (ipRGCs) containing the photopigment melanopsin. The data from this study were analyzed with a recently published model incorporating three primary channels: a luminance (achromatic) channel, a blue-yellow opponent color channel and a melanopsin channel. There was good agreement between the predictions of this model and the recently published brightness perception data.

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