Expand this Topic clickable element to expand a topic
OSA Publishing

Early Posting

Accepted papers to appear in an upcoming issue

OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

The structure of quadratic Gauss sums in Talbot effect

Carlos Fernandez-Pousa

Doc ID: 283705 Received 27 Dec 2016; Accepted 23 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: The field diffracted from a one-dimensional, coherently illuminated periodic structure at fractional Talbot distances can be described as a coherent sum of shifted units cells weighted by a set of phases given by quadratic Gauss sums. We report on the computation of these sums by use of the properties of a recently introduced integer s, which is constructed here directly from the two coprime numbers p and q that define the fractional Talbot plane. Using integer s, the computation is reduced, up to a global phase, to the trivial completion of the exponential of the square of a sum. In addition, it is shown that the Gauss sums can be reduced to two cases, depending only on the parity of integer q. Explicit and simpler expressions for the two forms of integer s are also provided. The Gauss sums are presented as a Discrete Fourier Transform pair between periodic sequences of length q showing perfect periodic autocorrelation, and the Talbot weighting factors of orders 1/q and 2/q are reduced to a closed form. Connection with existing characterizations of Talbot weighting phases is provided. The relationship with one-dimensional multilevel phase structures is exemplified by the study of Talbot array illuminators. These results represent a simple means for the design and analysis of systems employing the fractional Talbot effect.

Automatic detection of trichomonads based on an improved Kalman background reconstruction algorithm

Ruqian Hao, Xiangzhou Wang, Jing Zhang, Juanxiu Liu, Guangming Ni, Xiaohui Du, Lin Liu, and Yong Liu

Doc ID: 284111 Received 10 Jan 2017; Accepted 23 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: Automatic detection of trichomonads in leukorrhea provides important information for evaluating gynecological diseases. Traditional manual microscopy, which depends on the operator’s expertise and subjective factors, has high false-positive rates (i.e., low specificity) and low efficiency. To date, there are many detection methods for biological cells based on morphological characteristics. However, the morphology of trichomonads changes, and its size is not fixed; moreover, they are similar to human leukocytes. Therefore, it is difficult to classify trichomonads based on morphological characteristics. In this study, a moving object detection method based on an improved Kalman background reconstruction algorithm is proposed to detect trichomonads automatically considering the dynamic characteristics of trichomonads at room temperature. The experimental results show that the trichomonads can be identified accurately and the phenomena of tailing and ghosts are eliminated. Furthermore, this algorithm easily adapts to continuous or sudden changes in light, focal length variation, and the impact of lens shift, and it has good robustness and only a moderate amount of calculation burden.

Relating Wavefront Error, Apodization and the Optical Transfer Function: General Case

Jim Schwiegerling

Doc ID: 284370 Received 09 Jan 2017; Accepted 23 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: In a previous paper, a technique was developed for decomposing the incoherent Optical Transfer Function (OTF) into a linear combination of basis functions.[1] The expansion coefficients for the OTF are directly related to wavefront error coefficients and apodization factors. This earlier work assumed rotational symmetry, so that only the on-axis wavefront error components, defocus and various orders of spherical aberration, and rotationally symmetric apodization were handled. In this paper, the technique is generalized to handle arbitrary wavefront errors and apodization. Analytic expressions for the basis functions, as well as an example expansion are provided.

Scattering of an electromagnetic plane wave by a sphere embedded in a cylinder

fabio mangini and Nicola Tedeschi

Doc ID: 285982 Received 03 Feb 2017; Accepted 23 Mar 2017; Posted 27 Mar 2017  View: PDF

Abstract: In this paper we face the scattering problem of a plane wave by a sphere embedded in an infinitely long circular cylinder. Both the scattering problems by a sphere and a cylinder are canonical problems in optics. However, the scattering problems involving different objects with different geometries have not been solved analytically in the literature: only asymptotic or approximated solutions are available. The scattering problem by cylinders and spheres concurrently present can be of great importance in several areas: from optical microscopy to biomedical applications, from metamaterials to civil-engineering applications. To solve the problem, the incident wave is expressed as a superposition of cylindrical harmonics. The scattered wave by the cylinder, being a cylindrical wave as well, has been expressed as a superposition of spherical harmonics in order to take into account the interaction with the sphere. The theoretical procedure returns a linear system of equations for the computation of the unknown coefficients of the series. A numerical code is presented to compute the scattered field, where a suitable truncation criterion for the series expansions has been proposed. Comparisons with a Finite-Element method have been presented to validate the results.

Propagation of partially coherent Laguerre Gaussian beams through inhomogeneous turbulent atmosphere

Ting Yang, Yonggen Xu, Huanhuan Tian, Dong Die, quan du, Biling Zhang, and Youquan Dan

Doc ID: 283506 Received 30 Dec 2016; Accepted 20 Mar 2017; Posted 22 Mar 2017  View: PDF

Abstract: Analytical formulae for the root-mean-square (rms) spatial width, the rms angular width and the M2-factor of partially coherent standard Laguerre Gaussian beam (PC-SLGB) and partially coherent elegant Laguerre Gaussian beam (PC-ELGB) in inhomogeneous turbulent atmosphere have been derived. The propagation properties of PC-SLGB and PC-ELGB in inhomogeneous atmospheric turbulence are studied numerically and comparatively. It can be found that the propagation of laser beams in inhomogeneous turbulence is different from that in homogeneous turbulence. It is also shown that the relative rms spatial width and M2-factor of PC-ELGB are more affected by inhomogeneous turbulence than that of PC-SLGB. More over, the relative rms spatial width and M2-factor of PC-SLGB and PC-ELGB in inhomogeneous turbulent atmosphere are closely related with waist width, coherence width, zenith angle, inner scale and beam orders. Furthermore, the saturation propagation distance (SPD) of relative M2-factor and rms angular width with zenith angles of π/6 are 20km and 0.5km.

Human detection in occluded scenes through optically inspired multi-camera image fusion

Maryam Ghaneizad, Zahra Kavehvash, and Hamid Aghajan

Doc ID: 283113 Received 20 Dec 2016; Accepted 20 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: In this paper, a novel approach for foreground extraction has been proposed based on a popular three-dimensional imaging technique in optics, named integral imaging. In this approach, multiple viewpoint images captured from a three-dimensional scene are used to extract range information of the scene, and effectively extract an object or a person, even in the presence of heavy occlusion. The algorithm consists of two parts: depth estimation and reconstruction of the targeted object at the estimated depth distance. Further processing on the resulting reconstructed image can lead to the detection of a face or a pedestrian in the scene, which may not otherwise be detectable due to partial occlusion in each of the views. The validity of our approach has been demonstrated by experimental results in different scenarios.

Multiple-path model of spectral reflectanceof a dyed fabric

Geoffrey Rogers, Nicolas Dalloz, Thierry Fournel, and Mathieu Hébert

Doc ID: 284100 Received 11 Jan 2017; Accepted 16 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: Experimental results are presented of the spectral reflectance of dyed fabric as analyzed by the multiple path model of reflection. The multiple-path model provides simple analytic expressions for reflection and transmission of turbid media by applying the Beer-Lambert law to each path through the medium and summing over all paths, each path weighted by its probability. The path-length probability is determined by a random walk analysis. The experimental results presented here show excellent agreement with predictions made by the model.

Induced axial and lateral color surface contributions

Andrea Berner, Thomas Nobis, and Herbert Gross

Doc ID: 285268 Received 19 Jan 2017; Accepted 16 Mar 2017; Posted 16 Mar 2017  View: PDF

Abstract: Induced aberrations in general are higher-order aberrations caused by ray perturbations of lower order, picked up in the previous optical system. Therefore, in the case of color aberrations, induced influences can already be observed at 2nd-order. They are generated by the preexisting 1st-order axial and lateral color. The analysis of relevant designs surface by surface to identify performance dominating lenses is a key method for understanding and optimizing those systems. Hence, in this paper a formula for the surface contribution of axial and lateral color including 2nd-order terms is derived and discussed differentiating between intrinsic and induced parts. It is also shown how this can be used to deduce a thick lens contribution of 2nd-order. All of the approaches are based on the Seidel concept, which characterizes any arbitrary optical system only by the paraxial marginal and chief ray of the primary wavelength.

Conjugate gradient method for Phase retrieval based on Wirtinger derivative

Zhun Wei, Wen Chen, Chengwei Qiu, and Xudong Chen

Doc ID: 282531 Received 09 Dec 2016; Accepted 16 Mar 2017; Posted 20 Mar 2017  View: PDF

Abstract: A conjugate gradient-Wirtinger flow (CG-WF) algorithm for phase retrieval is proposed in this paper. It is shown that, compared with recently reported Wirtinger flow (WF) and its modified methods, the proposed CG-WF algorithm is able to dramatically accelerate the convergence rate, while keeping the dominant computational cost of each iteration unchanged. We numerically illustrate the effectiveness of our method in recovering 1D Gaussian signals and 2D natural color images under both Gaussian and coded diffraction pattern (CDP) models.

The Partial Light Scattering Cross Section of Spherical Particles

Christopher Sorensen, Justin Maughan, and Amit Chakrabarti

Doc ID: 281354 Received 23 Nov 2016; Accepted 14 Mar 2017; Posted 14 Mar 2017  View: PDF

Abstract: We define the partial scattering cross section and partial efficiencies to demonstrate that the total scattering is the sum of two roughly equal parts; approximately half from the forward scattering lobe due to 2d diffraction by the projected sphere and half from the 2d to 3d diffraction crossover. The first part is at angles such that θ ≲ λ/D, a result previously known, which can be quite small for large particles, an important fact for designing experiments and application of scattering for climate models. The second part is in a new regime we call the “hump” which disappears when the imaginary part of the refractive index is significant.

Digital phase correction of a partially coherent sparse aperture system

Sarah Krug and David Rabb

Doc ID: 275225 Received 05 Sep 2016; Accepted 14 Mar 2017; Posted 16 Mar 2017  View: PDF

Abstract: A digital piston phase correction method is presented for partially coherent synthesis with active or passive illumination. An anamorphic pupil relay causes a linear shift of a two sub-aperture array between the entrance and exit pupil. This shift separates the sub-apertures’ cross- and auto-correlations while retaining their common spatial frequency information. Digital analysis of these common frequencies finds the separation distance and piston phase error of the cross-correlations and enables lossless correction of phase error. Corrected images are diffraction limited. Partial coherence affects the contrast of each spatial frequency, causing optical path difference tolerances to relax as system bandwidth decreases.

Fresnel diffraction from a step in general case

Hamid Salvdari, Mohammad Tavassoly, and Seyed Roohollah Hosseini

Doc ID: 283636 Received 27 Dec 2016; Accepted 12 Mar 2017; Posted 13 Mar 2017  View: PDF

Abstract: Recently Fresnel diffraction from phase steps with parallel plates have been studied in rather details and the subject has led to many interesting metrological applications. In this report we formulate Fresnel diffraction from a physical step with arbitrarily oriented plates in reflection mode. We simulate the diffraction patterns for different orientations of the plates and develop the required procedure for determining the involved angles by analysis of the diffraction pattern. In the experimental part of the report we arrange a setup to form diffraction patterns in different orientations of the step plates and test the derived formulations. Also, we briefly review the application potentials of the subject.

Design of angularly tolerant zero-contrast grating filters for pixelated filtering in the mid-IR range

Léopold Macé, Olivier Gauthier-Lafaye, Antoine Monmayrant, and Henri CAMON

Doc ID: 284097 Received 05 Jan 2017; Accepted 12 Mar 2017; Posted 13 Mar 2017  View: PDF

Abstract: Zero-contrast gratings (ZCG) can be used to implement narrow bandpass transmission filters. However, they suffer from a poor angular tolerance which hinders their use in pixelated applications. Combining ZCG with double-corrugation grating, we increase the resonance width and the angular tolerance of the filter by more than one order of magnitude. Filters tunable around 4.6µm with more than 90% transmission and compatible with 70µm pixel size are demonstrated.

Camera self-calibration from projection silhouettes of an object in double planar mirrors

Yue Zhao and Yuanzhen Li

Doc ID: 276427 Received 26 Sep 2016; Accepted 10 Mar 2017; Posted 16 Mar 2017  View: PDF

Abstract: In double planar mirror omnidirectional imaging systems, camera calibration is a crucial part of the 3D reconstruction process. Based on analysis of the imaging geometric features of double planar mirrors, three types of algorithms for the camera intrinsic parameters are presented by computing the imaged circular points and orthogonal vanishing points. The camera intrinsic parameters can be obtained by the constraints on the imaged circular points and the orthogonal vanishing points to the image of the absolute conic (IAC). Simulation, real data, and 3D reconstruction experiments are presented to show the feasibility and validity of the proposed methods.

SPICA, Stellar Parameters and Images with a Cophased Array: a new 6T visible combiner for the CHARA Array

Denis Mourard, Philippe Berio, Karine Perraut, Jean-Michel Clausse, Orlagh Creevey, Marc-Antoine Martinod, Anthony Meilland, Florentin Millour, and Nicolas Nardetto

Doc ID: 277935 Received 05 Oct 2016; Accepted 10 Mar 2017; Posted 13 Mar 2017  View: PDF

Abstract: High angular resolution studies of stars in the optical domain have highly progressed these last years. After the results obtained with the visible instrument VEGA on the CHARA Array (Mount Wilson Observatory) and the recent developments on adaptive optics and fibered interferometry, we have started the design and study of a new 6-telescope visible combiner with single mode fibers. It is designed as a low spectral resolution instrument for the measurement of the angular diameters of stars with a major step forward in terms of magnitude and precision with respect to the present situation. For a large sample of bright stars, a medium spectral resolution mode will allow unprecedented spectral imaging of stellar surfaces and environments for higher accuracy on the stellar/planetary parameters. To reach the ultimate performance of the instrument in terms of limiting magnitude (Rmag=9, squared visibility V²<0.01), SPICA includes the development of a dedicated fringe tracking system in the H band to reach 'long' (200ms to 30s) exposures of the fringe signals in the visible.

Synthetic Aperture Radar with Dynamic Metasurface Antennas: A Conceptual Development

Michael Boyarsky, Timothy Sleasman, Laura Maria Pulido Mancera, Thomas Fromenteze, Andreas Pedross-Engel, Claire Watts, Mohammadreza F. Imani, Matt Reynolds, and David Smith

Doc ID: 280383 Received 09 Nov 2016; Accepted 09 Mar 2017; Posted 09 Mar 2017  View: PDF

Abstract: We investigate the application of dynamic metasurface antennas (DMAs) to synthetic aperture radar (SAR) systems. Metasurface antennas can generate a multitude of tailored electromagnetic waveforms from a physical platform that is low-cost, lightweight, and planar; characteristics not readily available with traditional SAR technologies such as phased arrays and mechanically-steered systems. We show that electronically-tuned DMAs can generate steerable, directive beams for traditional stripmap and spotlight SAR imaging modes. This capability eliminates the need for mechanical gimbals and phase shifters, simplifying the hardware architecture of a SAR system. Additionally, we discuss alternative imaging modalities, including enhanced resolution stripmap and diverse pattern stripmap, which can achieve resolution on par with spotlight, while maintaining a large region of interest, as possible with stripmap. Further consideration is given to strategies for integrating metasurfaces with chirped pulse RF sources. DMAs are poised to propel SAR systems forward by offering a vast range of capabilities from a significantly improved physical platform.

Cross-Scale Cost Aggregation Integrating Intra-ScaleSmoothness Constraint with WLS in Stereo Matching

Hao Ma, Shunyi Zheng, Chang Li, Yingsong Li, Gui Li, and Rongyong Huang

Doc ID: 279432 Received 01 Nov 2016; Accepted 06 Mar 2017; Posted 06 Mar 2017  View: PDF

Abstract: Cross-scale cost aggregation (CSCA) allows pixelwise multi-scale interaction in the aggregated cost computation.This kind of multi-scale constraint strengths the consistency of inter-scale cost volume and behaves well intextureless region, compared with the single scale cost aggregation. However, the relationship between neighbors’cost is ignored. Based on the prior knowledge that costs should vary smoothly, except at object boundaries, thesmoothness constraint in a neighborhood system is integrated into CSCA model with WLS for reliable matching inthis paper. Our improved algorithm not only has the advantage of CSCA in computational efficiency but alsoperforms more excellently than CSCA, especially on the KITTI datasets. Experimental evidence demonstrates thatthe proposed algorithm outperforms CSCA in textureless and discontinuous regions. Quantitative evaluationsdemonstrate the effectiveness and efficiency of the proposed method for improving disparity estimation accuracy.

Camera calibration based on the principal rays model of imaging optical systems

Toshiaki Matsuzawa

Doc ID: 279558 Received 02 Nov 2016; Accepted 05 Mar 2017; Posted 06 Mar 2017  View: PDF

Abstract: The parametric camera model is newly presented in order to calibrate rotationally non-symmetric and non-centralcameras. This model assumes cameras designed rotationally symmetric and containing manufacturing errors. Forthis purpose, the general expression of the principal rays, which are equivalent to the back projection linescorresponding to the image coordinates, on the object side of imaging optical systems is derived based on theaberration theory, which includes all components of distortion and pupil aberration. Moreover, since it is a linearmodel, the camera parameters to be iteratively optimized are always limited only to three rotation angles in thebundle adjustment. Accordingly, the intrinsic and extrinsic parameters of the camera model can be estimatedsteadily and faster. These properties are verified in experiments using the measurement data prepared bysimulation. As a result, it is concluded that this model is valid as a principal rays model and also functionsappropriately as a camera model.

Evaluation of whiteness formulas for FWA and non-FWA whites

Minchen Wei, Shining Ma, Yuzhao Wang, and Ming Luo

Doc ID: 284214 Received 06 Jan 2017; Accepted 04 Mar 2017; Posted 08 Mar 2017  View: PDF

Abstract: Whiteness is an important colorimetric characteristic for surface colors. Currently, the CIE Whiteness formula is widely used to characterize the whiteness of a surface in industry, whose limitations have been well documented. In this study, the whiteness appearance of 55 samples (43 non-FWA and 12 FWA samples) were evaluated under six lighting conditions, comprising three levels of CCT (i.e., 3000, 4000, and 6500 K) and two levels of UV radiation (i.e., zero and high) by 12 observers with normal color vision. The results indicated that the CIE whiteness formula with the CAT02 and the optimized CIE whiteness formula had the best performance in predicting the whiteness of surface colors, regardless of whether FWAs are contained, among the six formulas.

Revealing Information by Averaging

Sami Arpa, Sabine Susstrunk, and Roger Hersch

Doc ID: 275355 Received 14 Sep 2016; Accepted 03 Mar 2017; Posted 27 Mar 2017  View: PDF

Abstract: We present a method for hiding images in synthetic videos and reveal them by temporal averaging. The main challenge is to develop a visual masking method that hides the input image both spatially and temporally. Our masking approach consists of temporal and spatial pixel by pixel variations of the frequencyband coefficients representing the image to be hidden. These variations ensure that the target image remains invisible both in the spatial and the temporal domains. In addition, by applying a temporal masking function derived from a dither matrix, we allow the video to carry a visible message that isdifferent from the hidden image. The image hidden in the video can be revealed by software averaging, or with a camera, by long exposure photography. The presented work may find applications in the secure transmission of digital information.

Inhomogeneous Poisson Process Rate Function Inference from Dead-Time Limited Observations

Gunjan Verma and Robert Drost

Doc ID: 285187 Received 19 Jan 2017; Accepted 19 Feb 2017; Posted 16 Mar 2017  View: PDF

Abstract: The estimation of an inhomogeneous Poisson process (IHPP) rate function from a set of process observations is an important problem arising in optical communications and a variety of other applications. However, because of practical limitations of detector technology, one is often only able to observe a corrupted version of the original process. In this paper, we consider how inference of the rate function is affected by dead time, a period of time after the detection of an event during which a sensor is insensitive to subsequent IHPP events. We propose a flexible non-parametric Bayesian approach to infer an IHPP rate function given dead-time limited process realizations. Simulation results illustrate the effectiveness of our inference approach and suggest its ability to extend the utility of existing sensor technology by permitting more accurate inference on signals whose observations are severely dead-time limited. We apply our inference algorithm to experimentally collected optical communications data, demonstrating the practical utility of our approach in the context of channel modeling and validation.

Correction of turbulence-degraded underwater images using shift map analysis

Kalyan Halder, Manoranjan Paul, Murat Tahtali, Sreenatha Anavatti, and Manzur Murshed

Doc ID: 278065 Received 03 Oct 2016; Accepted 12 Dec 2016; Posted 13 Dec 2016  View: PDF

Abstract: In underwater imaging, the water waves cause severe geometric distortions and blurring of the acquiredshort-exposure images. Corrections for these distortions have been tackled reasonably well by previousefforts, but still need improvement in the estimation of pixel shift maps to increase the restoration accuracy.This paper presents a new algorithm that efficiently estimates the shift maps from the geometricallydistorted video sequences and uses those maps to restore the sequences. A non-rigid image registrationmethod is employed to estimate the shift maps of the distorted frames against a reference frame. Thesharpest frame of the sequence, determined using a sharpness metric, is chosen as the reference frame.A k-means clustering technique is employed to discard too blurry frames that could result in inaccuracyin the shift maps’ estimation. The estimated pixel shift maps are processed to generate the accurate shiftmap that is used to dewarp the input frames into their non-distorted forms. The proposed method isapplied on several synthetic and real-world video sequences and the obtained results exhibit significantimprovements over the state-of-the-art methods.

Select as filters

    Select Topics Cancel
    © Copyright 2017 | The Optical Society. All Rights Reserved