Journal of The Optical Society of America A-optics Image Science and Vision最新文献

This paper proposes a methodology for the design of freeform reflectors with scattering surfaces. We use microfacets, which are small, tilted mirrors superimposed on a smooth surface. We form a simple model of surface roughness and light scattering based on the orientations of the microfacets. Using a least-squares solver to compute the smooth reflector as a starting point, we can subsequently alter the surface using an optimization procedure to account for the scattering. After optimization, the resulting reflector surface produces the desired scattered light distribution. We verify the resulting reflector using raytracing. This study focuses on freeform systems with a collimated incident beam and a far-field target intensity.

Tungsten inert gas (TIG) welding is the main welding process in the production of stainless steel welded pipe. According to the morphological characteristics of the welding molten pool image during the TIG welding process of stainless steel welded pipes, the exact position of the tungsten needle tip is calculated using image moments. Extract the weld region in the contour of the molten pool, interpolate the contour curve based on the cubic B-spline curve interpolation method, utilize the characteristics of the S-G filter, remove the interference coordinates in the contour curve through the detrending of the contour curve, extract the weld feature points, and realize the accurate identification of weld seams. The experimental results show that the method can accurately calculate the welding deviation in the welding process.

In a previous study [J. Opt.19, 0905603 (2017)JOOPDB0150-536X10.1088/2040-8986/aa7cac], we revealed that the complete second-order statistics of narrowband polarized waves are characterized by 13 parameters, in contrast to the four parameters of the traditional Stokes vector description of the statistics of partially polarized light. In this study, we analyzed the second-order statistics of the field of a randomly rotating source of electromagnetic radiation and showed that it includes covariance of the right- and left-circular polarizations that are not captured by the Stokes vector formalism. We illustrate this finding using simple examples of rotating quadrupoles and dipole pairs.

Uniform laser beams with controllable patterns are crucial for various applications, including laser processing and inertial confinement fusion. While some methods have been proposed to generate flattop beams, they often require complex optical systems that can become ineffective because of the misalignment of the system or the imperfection of optical elements. To overcome these issues, we utilized feedback-based wavefront shaping (FWS) technology to generate flattop beams with desired patterns from a disordered light. To solve the multi-goal optimization problem, we propose some modifications based on the Non-dominated Sorting Genetic Algorithm II (NSGA2) and successfully generate focal beams with a uniform intensity distribution and controllable beam shape from the disordered light field.

This paper proposes a staircase joint optimization scheme (SJOS) with alternating diagonal interference cancellation and power allocation in an underwater wireless optical communication system based on nonorthogonal multiple access (UWOC-NOMA) with the multi-user paired. The scheme employs the directional iteration to alternatively optimize the subproblems of the interference cancellation and the power allocation. Furthermore, a one-way sorting algorithm based on the alternating diagonal interference cancellation and power allocation subalgorithm based on the conjugate gradient method are presented to solve the two subproblems, respectively. Simulation results show that the algorithm effectively reduces the average outage probability of the system with fast convergence, even with an increase in the number of paired users.

Rigorous coupled-wave analysis (RCWA) has become one of the most efficient electromagnetic solvers to cope with the diffractions of large-scale periodic nanostructures. Conventional RCWAs focus on planar diffractions and their iterative stabilities. Conical diffractions, as more general incidence cases, are paid little attention in developing their universal and stable implementations for multilayered gratings. Here, we reformulate RCWA algorithms step by step for conical diffractions in a global Cartesian coordinate system. By applying some mathematics tricks, it is found that boundary conditions in conical diffractions can be reduced to the same forms as that of planar diffractions. Conventional stable algorithms including enhanced transmittance matrices and scattering matrices can be directly implemented to attain robust diffraction efficiencies as well as electromagnetic fields for multilayered gratings. An exemplary application in diffractive-waveguide-based augmented reality verified our algorithms.

We consider the three-dimensional (3D) polarimetric properties of an evanescent optical field excited in the gap of a double-prism system by a random plane wave. The analysis covers the case of frustrated total internal reflection (FTIR), i.e., optical tunneling, and relies on the characteristic decomposition of the 3×3 polarization matrix. We find in particular that, for any incident partially polarized plane wave, the evanescent field inside the gap is necessarily in a nonregular, genuine 3D polarization state. We also show that the 3D polarimetric properties of the field at the second boundary are sensitive to the changes of the gap width and that the relevant effects occur for the smaller widths when the angle of incidence of the plane wave becomes larger. The results of this work uncover new aspects of the polarimetric structure of genuine 3D evanescent fields and may find applications in near-field optics and surface nanophotonics.

This work presents a thorough investigation of the focusing characteristic of chirped phase modulated Lorentz-Gaussian (LG) vortex beams based on the vector diffraction theory. The results show that changing the first-order chirp parameter c ₁ can effectively adjust the size of the focusing spot, and the distance between focusing spots can also be controlled. The second-order chirp parameter c ₂ can control the up-and-down movement of the optical chain in the focusing region. Simultaneously, the length of the focusing spots can be accurately changed by modulating the waist width ω. In addition, the influence of integer topological charge number m on controlling the size of an optical dark trap is discussed in detail. And fractional topological charge number m can control the rotation of focus peak and the number of optical dark traps. Potential applications of these findings include optical shape and capture, optical particle transmission, and contemporary medical care.

To address problems such as the lack of accuracy in acquiring depth maps for dynamic fish 3D measurements by usual binocular vision or a time-of-flight (TOF) depth camera, a TOF-assisted binocular vision depth acquisition algorithm is used to obtain high-quality depth maps. The TOF depth energy function is designed to guide the binocular stereo matching process, which improves the correct matching rate of binocular matching in low-texture regions; the TOF and binocular stereo matching confidence weighting functions are designed to achieve the fusion of the two at pixel level to improve the matching quality of fish in the occluded overlapping regions. The experimental results show that the TOF-assisted binocular vision system improves the accuracy of fish size measurement compared to single binocular vision while reducing the measurement error when the fish body has a significant inclination along the depth axis.

The wrapped phase patterns of objects with varying materials exhibit uneven gray values. Phase unwrapping is a tricky problem from a single wrapped phase pattern in electronic speckle pattern interferometry (ESPI) due to the gray unevenness and noise. In this paper, we propose a convolutional neural network (CNN) model named UN-PUNet for phase unwrapping from a single wrapped phase pattern with uneven grayscale and noise. UN-PUNet leverages the benefits of a dual-branch encoder structure, a multi-scale feature fusion structure, a convolutional block attention module, and skip connections. Additionally, we have created an abundant dataset for phase unwrapping with varying degrees of unevenness, fringe density, and noise levels. We also propose a mixed loss function MS_SSIM + L2. Employing the proposed dataset and loss function, we can successfully train the UN-PUNet, ultimately realizing effective and robust phase unwrapping from a single uneven and noisy wrapped phase pattern. We evaluate the performance of our method on both simulated and experimental ESPI wrapped phase patterns, comparing it with DLPU, VUR-Net, and PU-M-Net. The unwrapping performance is assessed quantitatively and qualitatively. Furthermore, we conduct ablation experiments to evaluate the impact of different loss functions and the attention module utilized in our method. The results demonstrate that our proposed method outperforms the compared methods, eliminating the need for pre-processing, post-processing procedures, and parameter fine-tuning. Moreover, our method effectively solves the phase unwrapping problem while preserving the structure and shape, eliminating speckle noise, and addressing uneven grayscale.