Vortex Imaging Research Articles

Imaging and structure analysis of ferroelectric domains, domain walls, and vortices by scanning electron diffraction

Imaging and structure analysis of ferroelectric domains, domain walls, and vortices by scanning electron diffraction

Improving millimeter-wave imaging quality using the vortex phase method

This paper investigates a new vortex wave imaging approach to improve the imaging quality of small metal targets of size less than 1.5 mm. Antennas with different spiral phase plates are designed to efficiently transmit vortex beams with orbital angular momentums (OAMs). By analyzing the OAM spectrum of the target, it was discovered that the predominant reflection contains a particular OAM mode that carries abundant azimuthal information. This can be explained by the OAM selectivity of the target and the guidance of the vortex transmitting beam. A simple reflection vortex imaging system was designed to capture the phase information. Measurement results show that the high image contrast reaches 14.9%, which is twice as high as that of the imaging without OAM. Both of simulations and experiments demonstrate that the vortex phase imaging approach proposed in this paper can effectively improve the imaging quality at 80 GHz. This approach is suitable for other millimeter wave imaging systems and is helpful to improve the resolution in anti-terrorism security checks.

MINDS: JWST/NIRCam imaging of the protoplanetary disk PDS 70

Context. Two protoplanets have recently been discovered within the PDS 70 protoplanetary disk. JWST/NIRCam offers a unique opportunity to characterize them and their birth environment at wavelengths that are difficult to access from the ground. Aims. We image the circumstellar environment of PDS 70 at 1.87 μm and 4.83 μm, assess the presence of Pa-α emission due to accretion onto the protoplanets, and probe any IR excess indicative of heated circumplanetary material. Methods. We obtained noncoronagraphic JWST/NIRCam images of PDS 70 within the MIRI mid-INfrared Disk Survey (MINDS) program. We leveraged the Vortex Image Processing (VIP) package for data reduction, and we developed dedicated routines for optimal stellar point spread function subtraction, unbiased imaging of the disk, and protoplanet flux measurement in this type of dataset. A radiative transfer model of the disk was used to separate the contributions from the disk and the protoplanets. Results. We redetect both protoplanets and identify extended emission after subtracting a disk model, including a large-scale spiral-like feature. We interpret its signal in the direct vicinity of planet c as tracing the accretion stream that feeds its circumplanetary disk, while the outer part of the feature may rather reflect asymmetric illumination of the outer disk. We also report a bright signal that is consistent with a previously proposed protoplanet candidate enshrouded in dust near the 1:2:4 mean-motion resonance with planets b and c. The 1.87 μm flux of planet b is consistent with atmospheric model predictions, but the flux of planet c is not. We discuss potential origins for this discrepancy, including significant Pa-α line emission. The 4.83 μm fluxes of planets b and c suggest enshrouding dust or heated CO emission from their circumplanetary environment. Conclusions. The use of image-processing methods that are optimized for extended disk signals on high-sensitivity and high-stability from JWST can uniquely identify signatures of planet–disk interactions and enable accurate photometry of protoplanets at wavelengths that are difficult to probe from the ground. Our results indicate that more protoplanets can be identified and characterized in other JWST datasets.

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Edge enhancement in three-dimensional vortex imaging based on FINCH by Bessel-like spiral phase modulation.

Edge enhancement, as an important part of image processing, has played an essential role in amplitude-contrast and phase-contrast object imaging. The edge enhancement of three-dimensional (3D) vortex imaging has been successfully implemented by Fresnel incoherent correlation holography (FINCH), but the background noise and image contrast effects are still not satisfactory. To solve these issues, the edge enhancement of FINCH by employing Bessel-like spiral phase modulation is proposed and demonstrated. Compared with the conventional spiral phase modulated FINCH, the proposed technique can achieve high-quality edge enhancement 3D vortex imaging with lower background noise, higher contrast and resolution. The significantly improved imaging quality is mainly attributed to the effective sidelobes' suppression in the generated optical vortices with the Bessel-like modulation technique. Experimental results of the small circular aperture, resolution target, and the Drosophila melanogaster verify its excellent imaging performance. Moreover, we also proposed a new method for selective edge enhancement of 3D vortex imaging by breaking the symmetry of the spiral phase in the algorithmic model of isotropic edge enhancement. The reconstructed images of the circular aperture show that the proposed method is able to enhance the edges of the given objects selectively in any desired direction.

In Vivo Vortex Imaging of Bladder.

In Vivo Vortex Imaging of Bladder.

Monopulse Electromagnetic Vortex Imaging Method by Multiplexing OAM Modes Based on Frequency Diversity

Monopulse Electromagnetic Vortex Imaging Method by Multiplexing OAM Modes Based on Frequency Diversity

Electromagnetic Vortex Imaging Based on OAM Multiplexing Beam With Orthogonal Polyphase Coding

Electromagnetic Vortex Imaging Based on OAM Multiplexing Beam With Orthogonal Polyphase Coding

Data-Driven Discovery of Anomaly-Sensitive Parameters from Uvula Wake Flows Using Wavelet Analyses and Poincaré Maps

This study presents a data-driven approach to identifying anomaly-sensitive parameters through a multiscale, multifaceted analysis of simulated respiratory flows. The anomalies under consideration include a pharyngeal model with three levels of constriction (M1, M2, M3) and a flapping uvula with two types of kinematics (K1, K2). Direct numerical simulations (DNS) were implemented to solve the wake flows induced by a flapping uvula; instantaneous vortex images, as well as pressures and velocities at seven probes, were recorded for twelve cycles. Principal component analysis (PCA), wavelet-based multifractal spectrum and scalogram, and Poincaré mapping were implemented to identify anomaly-sensitive parameters. The PCA results demonstrated a reasonable periodicity of instantaneous vortex images in the leading vector space and revealed distinct patterns between models with varying uvula kinematics (K1, K2). At higher PCA ranks, the periodicity gradually decays, eventually transitioning to a random pattern. The multifractal spectra and scalograms of pressures in the pharynx (P6, P7) show high sensitivity to uvula kinematics, with the pitching mode (K2) having a wider spectrum and a left-skewed peak than the heaving mode (K1). Conversely, the Poincaré maps of velocities and pressures in the pharynx (Vel6, Vel7, P6, P7) exhibit high sensitivity to pharyngeal constriction levels (M1–M3), but not to uvula kinematics. The parameter sensitivity to anomaly also differs with the probe site; thus, synergizing measurements from multiple probes with properly extracted anomaly-sensitive parameters holds the potential to localize the source of snoring and estimate the collapsibility of the pharynx.

Enhanced resolution of edge enhancement in three-dimensional vortex imaging based on a modified Michelson interferometer

Edge enhancement is emerging as an essential technique for object recognition in recent years. The edge detection of three-dimensional (3D) imaging has been successfully demonstrated in Fresnel incoherent correlation holograph (FINCH) system; however, with a relatively low resolution which needs to be further improved to meet practical requirements. In this work, a modified Michelson interferometer system using a spatial light modulator (SLM) is proposed, which realizes 3D vortex imaging with high resolution and low background noise. Compared with the spiral phase modulated polarization multiplexing FINCH system, the resolution of this system has apparently improved from 50.80 lp mm−1 to 57.02 lp mm−1. The improvement is assumed to be ascribed to the inherently high luminous flux utilization configuration of the Michelson interferometer and the precision phase shifts. More importantly, the proposed system exhibits prominently improved performance of edge enhancement for different objects, including the standard resolution target and label-free biological living cells. The experimental results of the small watch parts also demonstrate its ability in 3D vortex imaging with edge detection. These results provide a promising strategy for high-quality 3D vortex imaging and edge enhancement, and might pave the way for future applications in the fields such as edge detection and pattern recognition.

High-resolution optical imaging of single magnetic flux quanta with a solid immersion lens.

Magneto-optical imaging of quantized magnetic flux tubes in superconductors - Abrikosov vortices - is based on Faraday rotation of light polarization within a magneto-optical indicator placed on top of the superconductor. Due to severe aberrations induced by the thick indicator substrate, the spatial resolution of vortices is usually well beyond the optical diffraction limit. Using a high refractive index solid immersion lens placed onto the indicator garnet substrate, we demonstrate wide field optical imaging of single flux quanta in a Niobium film with a resolution better than 600 nm and sub-second acquisition periods, paving the way to high-precision and fast vortex manipulation. Vectorial field simulations are also performed to reproduce and optimize the experimental features of vortex images.

Near-field electromagnetic scattering of Bessel vortex beam by metal target

Bessel vortex beam, as a typical vortex beam, has the characteristics of carrying orbital angular momentum (OAM), no diffraction, and self-reconstruction, which makes it more competitive than plane wave in the field of future vortex beam target detection and imaging. In order to study the near-field electromagnetic scattering of a vortex beam by a metal target, the expression of the near-scattering field of Bessel vortex beam incident on any metal target is obtained by using the physical optics method, triangular surface element modeling, and the plane wave angular spectrum expansion method of vector Bessel vortex beam. The correctness of the proposed method is verified by comparing with the simulation results of FEKO software. The amplitude distribution and phase distribution of electric field, the OAM spectrum distribution and radar cross section (RCS) of the near-scattering field of the Bessel vortex beam incident on the simple target and the combined target are calculated. The effects of beam parameters, receiving distance, target shape and the positions of beam transmitting and receiving surfaces on near-field scattering results are numerically calculated. In addition, the distributions of near-field OAM spectra under different conditions and the near-field RCS distributions of different targets are given. The numerical results show that the near-field results of Bessel vortex beam incident on metal targets are related to the beam parameters, and conform to the law of Bessel beam changing with parameters. The near-field electric amplitude distribution is affected by the distance between the receiving surface and the target, but the phase distribution is hardly affected. The near-field scattering results reflect the changes of target shape. Under normal incidence, when the target is regular and symmetrical, the amplitude distribution and phase distribution are relatively regular, and the main mode is dominant. When the beam is obliquely incident on or does not fully illuminate the target, the amplitude distribution and phase distribution change, which will lead the derived mode to increase. In particular, when the target and the receiving surface both deviate from the incident beam, the OAM disturbance is the most severe. In the near-field RCS distribution, the RCS distributions of different targets are obviously different, and the results of &lt;i&gt;E&lt;/i&gt; plane and &lt;i&gt;H&lt;/i&gt; plane are also different. It can be seen from the numerical calculation results that the near-field scattering of Bessel vortex beam by a metal target contains a variety of information. The application of vortex electromagnetic wave will help improve the information acquisition of electromagnetic wave and target detection capability. The results in this work can provide a reference for target imaging and vortex radar detection.

An Improved Wake Vortex-Based Inversion Method for Submarine Maneuvering State.

As the noise reduction performance of submarines continues to improve, it is difficult to detect and track submarines through acoustic detection techniques. Therefore, nonacoustic submarine detection techniques are becoming more and more important. The submarine movement will leave a wake vortex, and the information of the wake vortex can be used to invert the maneuvering state of the submarine. However, the wake vortex is constantly dissipated in the evolution process, and the strength of the wake vortex is constantly reduced, resulting in the gradual weakening of the characteristics of the wake vortex, which makes the inversion of submarine operating state difficult and less accurate. In order to solve the above problems, this paper proposes an improved wake vortex-based inversion method for submarine maneuvering state. Firstly, a random finite set of submarine wake vortex observation features is established to obtain the feature with the highest correlation degree with submarine maneuvering state in the random finite set. Secondly, the multiscale fusion module and attention mechanism are used to re-encode the weak features of the wake vortex image, and the salient features of the wake vortex image are extracted. Finally, the manipulation state of the wake vortex image is retrieved by the extracted salient features. The experimental results show that the average inversion accuracy of the proposed algorithm is improved by 1.27% in terms of manipulating state inversion of weak feature wake vortex images. The algorithm in this paper can realize the inversion of submarine maneuvering state in the case of weak submarine wake vortex image features and incomplete feature information. It provides the basis for the detection technology based on the submarine wake characteristics.

Autofocusing and imaging algorithm for moving target by vortex electromagnetic wave radar

Electromagnetic (EM) vortex imaging, which combines with spiral wavefront phase modulation and computational imaging concept introduced by orbital angular momentum (OAM), has demonstrated superior performance in target information extraction and two-dimensional (2-D) or even three-dimensional (3-D) imaging capability in forward-looking observation geometry. However, due to the unknowns and complexity of target motion, the translational component will lead to the disturbance of echo phase, which hinders the motion compensation between target echo pulses and causes imaging defocus. In this paper, a high-resolution imaging algorithm based on Fourier ptychography (FP) is proposed for moving target autofocusing imaging by vortex electromagnetic forward-looking radar (VEMFLR). Firstly, based on the spatial geometric model and echo model of VEMFLR, high-order phase terms caused by target motion are derived, which provides a theoretical basis for applying FP phase retrieval to autofocusing imaging; Then, the spectrum information in FP sub-aperture is obtained; Thirdly, the imaging method, based on FP phase retrieval, is exploited to compensate phase error and obtain a well-focused image. Simulation results show that this method can achieve fine imaging performance without estimating target motion parameters.

Experimental and Computational Fluid Dynamics Study of the Flow Field of a Model Pump Turbine

The pumped storage unit has a hump area and S characteristics during operation. The operating conditions of the unit are complex, and it is necessary to switch between working conditions. The unit frequently crosses the hump area and the S characteristic area, thus hindering the unit to connect to the grid. Severe vibration affects the safe and stable operation of a power station. With the joint efforts of the industry, the impact of the hump and S-shaped problems on project commissioning has been fundamentally resolved, but the mechanism of inducing hump and S-shaped problems has not yet been well established. Therefore, in this study, the particle image velocity measurement method based on a full-characteristic test was adopted. According to the operating characteristics of the unit, 32 operating points with four guide-vane opening degrees were selected to test the flow pattern in the vaneless space. After subtracting the average flow velocity, the vortex image of the leafless area was obtained, which provided a reference for the design of the runner of the water pump turbine.

In The Vortex of Institutional Lives

In The Vortex of Institutional Lives

High frame rate blood speckle tracking echocardiography: left ventricle vortex analyisis in healthy children and in congenital heart disease

Abstract Funding Acknowledgements Type of funding sources: None. Background High-frame rate blood speckle tracking (BST) echocardiography is a new method, for the evaluation of intracardiac flow, independent of the insonation angle. Left ventricle, throughout cardiac cycle, creates a vortical flow still poorly analysed in children with congenital heart disease (CHD). Aim of this study is to evaluate the characteristics of left ventricular (LV) vortices in healthy children and in those with CHD. Methods Characteristics of LV vortices were acquired on standard 4-chamber view and BST images from 230 healthy children (median age 5.96 years, range 2.9-10.1 years) and 72 children with CHD (median age 1.33 years, IQR 0.2-7.12 years). Both groups were compared after propensity matching. Multiple linear regression was used to identify factors that independently influence vortex characteristics. Results Feasibility of vortex imaging was 97% for healthy children and 96.7% for CHD. After propensity matching, there were mild significant differences in vortex distance to apex, distance to interventricular septum, height, width, sphericity index. Indexed by BSA Vortex Area (VAi) was significantly higher on CHD patients than healthy subjects (p &amp;lt; 0.0001). However, multiple regression analysis exposed significant associations of LV morphology with vortex characteristics: a VAi &amp;gt;0.98 can predict an abnormal LV morphology (Sensibility 73%, Specificity 83%). Furthermore, CHD involving LV volume or pressure overload were both associated with vortices localized closer to the IVS. Conclusions LV vortex analysis using high-frame rate BST echocardiography is feasible in healthy children and in those with CHD. Since vortices are associated with LV morphology and are altered in some CHDs, vortices might yield diagnostic and prognostic value. Future studies are necessary to further establish applications of vortex imaging in the clinical setting. Abstract Figure. Vortex in healthy children and in CHD

Probing vortex beams based on Talbot effect with two overlapping gratings

In a prior report the optical vortex was characterized using the near-field Talbot effect (Panthong et al 2016 J. Opt. 18 035602; Panthonget al 2018 Appl. Opt. 57 1657). This near-field technique can resolve both order and charge of the orbital angular momentum state of the vortex beam. We have proposed before that a small open fraction of the grating in the Talbot configuration can improve the image contrast (Srisuphaphon et al 2020 J. Opt. Soc. Am. B 37 2021). In this study, we combine these previously reported techniques, i.e. the Talbot effect for probing an optical vortex and overlapping gratings to manipulate the open fraction. Both theoretical simulation and experimental demonstration are presented here. We believe that our technique can be an alternative method for optical vortex imaging, and could be useful in optical applications.

A YOLOv3-Based Rice Vortex Detecting System Using Dual Collaborative UAVs

Highlights Used dual collaborative UAVs to track the rice vortex formed on rice canopy. A trained YOLOv3-tiny model was used to recognize and calculate the rice vortex parameters with high accuracy. Discovered a quantitative relationship between rice vortex parameters and UAV flight parameters. Aligned the time axis of data process to enhance the accuracy of the vortex parameter calculation. Abstract. A rice vortex generated by the downwash airflow of the agricultural UAV has a great connection to pesticide droplet deposition. In this study, an unmanned aircraft system (UAS) was designed to obtain rice vortex parameters including position coordinates, area, and relative distance to the UAV. The system uses the flight control system mounted Beidou RTK positioning system and Manifold onboard computer to localize the spraying UAV and trains a YOLOv3-tiny model to recognize motion images of dynamic rice vortices in real-time, achieving a mean accuracy of 98.15% with 0.9326 IOU. Moreover, to optimize the system, a data time axis alignment method based on the robot operating system (ROS) was proposed to alleviate the transmission delay and image processing time-consumption, which increased the accuracy of the vortex parameter by 3.48%. The rice vortex area acquired by the UAS was highly relevant to UAV flight parameters and the relative distance was just correlated to the UAV height. The instantaneous status of the rice vortex helps to lay a data foundation for adjusting the flight parameters of the plant protection UAV. Keywords: Precision agriculture, Rice vortex, ROS, Spray operation, UAV, YOLOv3-tiny.

Enhanced Resolution of Edge Enhancement in Three-Dimensional Vortex Imaging Based on a Modified Michelson Interferometer

Enhanced Resolution of Edge Enhancement in Three-Dimensional Vortex Imaging Based on a Modified Michelson Interferometer