Search

In the existing binocular stereo-matching methods for a speckle pattern, the pixel-by-pixel correlation weight calculation across the entire global disparity range is time-consuming. To address this issue, this paper presents a fast stereo-matching method for a speckle pattern based on grid and gradient constraints. The grid pattern is projected onto the measured object. The grid features are extracted to form the local disparity constraints, which narrow the search ranges. Moreover, the image gradient is used in selecting the pixels involved in the correlation weight calculation, which reduces the redundant computations. 3D reconstruction experiments of paper and plaster models were employed to evaluate the matching accuracy and speed of the proposed method. Furthermore, the experiments of measuring displacement were designed to validate the accuracy of our method. In contrast to the existing methods, our approach increased the matching speed by 66% on average while ensuring the matching accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a novel reconstruction method based on multi-refraction to remedy the non-linear refraction, which recovers 3D geometry from 2D images. To simplify calibration, this paper prove that air calibration can replace underwater calibration. Finally, a multi-line rotating structured is designed to improve the measurement efficiency without additional equipment. The results of the clean water experiment show that the measurement accuracy is 1.91 mm within the 1000–2000 mm depth of field. The qualitative analysis demonstrates our method can reconstruct the surface topography of underwater U and N letter boards. In different Nephelometric Turbidity Unit (NTU) (as NTU = 0.156 mg/ml) environment, a circular plate with a diameter of 220 mm is measured, the shape reconstruction error (whether the reconstructed shape is a circular, square, or other) is 1.74 mm; the diameter measurement result is 218 mm, so the size error of the circular plate is 2 mm. [ABSTRACT FROM AUTHOR]

This paper uses a numerical simulation method to evaluate the propagation performance of the partially coherent flat-topped vortex hollow (FTVH) beam and the Gaussian Schell-model (GSM) beam through atmospheric turbulence along slant links. The atmospheric turbulence is simulated by random phase screens, and the performance of the beam models is evaluated by using scintillation index and signal-to-noise (SNR) on the receiver plane with various simulation conditions and parameters. This paper has shown that there is an optimal coherence length for both the partially coherent FTVH beam and the GSM beam. In different parameter settings, the partially coherent FTVH beam has the best propagation performance at N = 1 M = 1. Compared to the GSM beam, the partially coherent FTVH beam obtains an obvious improvement in SNR. The results show that the partially coherent FTVH beam is able to improve the communication efficiency of an FSOC system. [ABSTRACT FROM AUTHOR]

The periodic misalignment of the wrapping phase and fringe order based on the phase-shift + coding method is known to occur easily, leading to jump errors in absolute phase recovery. This paper proposes a two-phase unwrapping method based on shifting-phase coding. This approach encodes the fringe order information and the wrapping phase into the four-step phase shift mode. It generates four composite fringe patterns to directly resolve the wrapping phase and fringe order, thus improving the measurement speed by reducing the number of fringe projections. The interleaved wrapping phases are then constructed by a sequence that changes the initial wrapping phase. The two-phase unwrapping becomes the absolute phase, so the phase error is avoided and the measurement accuracy is improved. The proposed strategy's effectiveness is proved by the comparison experiments of different methods. Similarly, the suggested method's reliability is verified by the measurement experiments of several discontinuous objects. [ABSTRACT FROM AUTHOR]

The article invites papers on the development and potential of next generation free-electron lasers to be published in the journal.

The article invites papers on optics to be published in a special issue of this journal.

The article invites papers on vision science and ophthalmic optics to be published in this journal.

Presents a preface of the papers from the 14th National Quantum Electronics Conference in Manchester, England. Organizer of the conference; Foundation of the Quantum Electronic (QE) conferences; History of the QE conferences.

This paper provides a concise overview of hybrid Free Space Optical (FSO)/Radio Frequency (RF) systems operating under fog and smog channels. With the rapid growth of wireless communication and the emergence of the Internet of Things (IoT) have brought about unprecedented connectivity and transformed various aspects of our daily lives. However, certain environmental conditions pose significant challenges to wireless communication systems like FSO and RF technologies. Fog and smog with its dense moisture-laden atmosphere and presence of particulate matter cause absorption and scattering of light, leading to reduced link quality and limited range for FSO communication system. Whereas, RF systems are although less affected by fog/smog as compared to rain but still have inherent limitations in terms of bandwidth and capacity. To overcome these challenges and ensure reliable communication, researchers have turned their attention to hybrid FSO/RF systems which can combine the strengths of FSO and RF technologies and mitigate the limitations of each technology. This work summarizes and explores the hybrid system architecture and machine learning techniques used to enhance the performance and adaptability of wireless communication systems. Additionally, we present the existing experimental research on hybrid FSO/RF systems, performance evaluation metrics, and future research directions to pave the way for further advancement. Abbreviation FSO: Free Space Optical; RF: Radio Frequency; IoT: Internet-of-Things; OS: Operating Systems; OWC: Optical Wireless Communication; LOS: Line-of-Sight; LPF: Low Pass Filter; AM: Amplitude Modulation; FM: Frequency Modulation; PSK:Phase Shift key; QAM: Quadrature Amplitude Modulation; OFDM: OrthogonalFrequency Division Multiplexing; LF: Low frequency; M-L: Medium frequency; UHF:Ultra High Frequency; SHF: Super High Frequency; EHF: Extremely High frequency; PM: Phase Modulation; QPSK: Quadrature Phase Shift Key; DSSS: Direct SequenceSpread Spectrum; FHSS: Frequency Hopping Spread Spectrum; LAN: Local AreaAccess; D/A: Digital to Analog; LO: Local Oscillator; PA: Power amplifier; A/D:Analog to Digital; LNA: Low Noise Amplifier; FEC: Forward error correction; APC: Automatic Power Control; RSSI: Received Signal Strength Indicator; ML: Machine Learning; RL: Reinforcement Learning; DL: Deep Learning; LR:Logistic Regression; DT: Decision Tree; SVM: Support Vector Machine; KNN:K-Means Neighbour; PCA: Principal Component Analysis; QL: Q-Learning; DQN:Deep Q-NEtwork; R-F: Random Forest; GB: Gradient Boosting; NA: NaiveBayes; ANN: Artificial Neural Network; DTA: Decision Tree with AdaBoost; MIMO: Multiple-Input Multiple-Output; GEO: Geostationary Orbit; NIR: NearInfra-Red; VLC: Visible Light Communication; OP: Optical Communication; BER: Bit Error Rate; ECC: Ergodic Channel Capacity; SNR: Signal-to-NoiseRatio; AO: Adaptive Optics; ATP: Acquisition- Tracking and Pointing; LEO:Low-Altitude Earth Orbit; UAVs: Unmanned Aerial Vehicles; NTN: Non-TerrestrialNetwork; RSSI: Received Signal Strength Indicator; FSPL: Free Space Path Loss; ITU: International Telecommunication Union; GANs: Generative AdversarialNetworks [ABSTRACT FROM AUTHOR]

Optical image encryption technique has become increasingly important. Recently, double-encryption is introduced to enhance security. However, most coherent double-cryptosystems suffer from artefact noise, while the incoherent double-cryptosystem is not stable enough. This paper proposes a method for image double-encryption using speckle decorrelation properties in spatial and spectral domains. The plaintext is disguised as several different fake plaintexts that are separately encrypted through rotated random phase masks under incoherent illumination with different wavelengths. Since the speckle decorrelation properties in spatial and spectral domains, the plaintexts contained in the detected speckle images are multiplexed in a ciphertext. The security is enhanced since correct decryption can be achieved only when all the keys with spatial and spectral domains information are obtained. Simulations, experimental demonstrations and attack resistance tests are implemented with a simple incoherent cryptosystem that is easy to achieve in practical applications. [ABSTRACT FROM AUTHOR]

In multimode interferometers, the interaction between several modes brings a high level of complexity to the interpretation of its light patterns. With recent advances, it is possible to selectively excite only a couple of modes inside the device. This paper presents an analytical method for determining the phase difference between two propagating modes in the multimode interferometer, in an effort to simplify the usage and expand the range of applications for this type of optical devices. [ABSTRACT FROM AUTHOR]

In a recent work, a technique was proposed to recover the absolute phase maps of fringe patterns with two or three selected fringe wavelengths with the aim to improve anti-error capability. To further increase the anti-error capability associated with the phase unwrapping operation, multiple fringe patterns with different wavelengths may also be used. In this paper, we present a general rule to select the wavelengths and the strategy to increase phase error tolerance bound. Based on this rule, it is concluded that to maximize the error tolerance, four-wavelength method should be selected, where the maximum upper bound of the tolerable phase error is π/6. To minimize the required number of fringe patterns, three-wavelength method with three-step PSP should be selected, that is exactly the case the previous paper has demonstrated. These theoretical conclusions are verified by experimental results. [ABSTRACT FROM AUTHOR]

Dark-field microscopic imaging system has high spatial resolution, but small image field. When an optical surface with a large-diameter is tested, the image stitching is necessary to obtain the full-aperture detection results. In this paper, Harris corner detection algorithm is used to achieve the full aperture testing result by stitching multiple detection images. According to the Shannon sampling theorem, how the size of the overlapping area influences the stitching results is analysed in detail. Combined with the spatial scale of surface defects, a method for determining the size of the overlapping area is given. The standard scratch patterns are used to simulate the stitching process. On this basis, an actual stitching processing is carried out on the detection images of surface scratches of four different spatial scales. Both the simulation and experimental results show that it is reasonable to use the scale of the smallest defect to determine the number of sampling points in the stitching area. [ABSTRACT FROM AUTHOR]

In this paper, a high-performance metamaterial sensor with a square split-ring resonator and a double circular split-ring resonator is proposed, which can simultaneously excite broad-band and narrow-band electromagnetically induced transparency-like (EIT-like) effects in the terahertz band. First, the mechanisms of the dual-band EIT-like effects have been revealed by the analyses of the transmission spectra and surface current distributions in the metamaterial. Then, the influences of structural parameters on the dual-band EIT-like are discussed further. Finally, the metamaterial is very sensitive to the change of the refractive index of the surrounding media, and the sensitivity of the dual-band EIT-like resonances can reach 150 GHz/RIU and 237.5 GHz/RIU and the quality factor values are 1.67 and 7.92, respectively. The proposed metamaterial broadens the pathway for the excitation of multi-band EIT-like effects and offers promising applications in multi-frequency sensors, filters and many other aspects. [ABSTRACT FROM AUTHOR]

At present, the co-phasing detection algorithms for segmented mirrors struggle to balance the measurement range and accuracy. This paper proposes a coarse co-phasing measurement method using the incoherent properties of a broadband (400–800 nm) light source combined with the incoherence of two semicircular diffraction patterns of visible light as a template to detect the piston error, and a narrowband algorithm for fine co-phasing measurement. The diversity factors between template patterns and actual diffraction patterns can be calculated by the cross-correlation algorithm. This proposed method addresses long measurement time caused by low target flow rate and is characterized by wide measurement range, high precision and high energy utilization. The method is theoretically researched and simulated and an experimental system which was constructed to verify the effectiveness of this method achieves 15 nm detection accuracy, and the measurement range using the proposed method can match the measurement range of the actuator. [ABSTRACT FROM AUTHOR]

In this paper, we propose a full-Stokes image reconstruction (FIR) network to reconstruct polarization images from a snapshot of random modulated image. The Stokes-Mueller matrix theory demonstrates that a image captured by conventional polarization imaging system is a linear superposition of the four Stokes vectors, thus image decomposition methods can be used for full-Stokes image reconstruction. The network is constructed based on a cycled conditional adversarial network, which is trained utilizing the physical mapping relationships between the Stokes vectors and the modulated images. Simulations and experiments are conducted to demonstrate the network's wavelength independence and modulation independence, proving the effectiveness of proposed FIRnet. To some extent, our method alleviates the contradiction between measurement time and accuracy of polarization, promoting the application of compact snapshot full-Stokes imaging. [ABSTRACT FROM AUTHOR]

This paper describes the development of a common path off-axis quantitative phase microscope (QPM), enabling high-speed quantitative measurements of sub-cellular dynamics in a live cell. The proposed 4f optical system consists of a polarizer, lenses, calcite crystal, pinhole and analyser, attached to the output port of an optical microscope converting it into a temporally stable QPM. The temporal phase stability of this optical configuration is measured to be equal to ∼20 mrad without a vibration isolation table. The utility of the microscope is demonstrated by conducting experiments on a polystyrene sphere (dia. 12 μm) and human red blood cells (RBCs). Furthermore, the developed system is implemented to study temporal membrane fluctuation in human RBCs over ∼30s and mouse embryonic fibroblast cell dynamics over 2 hours. Therefore, the system offers an energy-efficient and simple solution for generating object and reference beams for common-path QPM, making it an attractive alternative to existing approaches. [ABSTRACT FROM AUTHOR]

Blood oxygen content plays an important role in clinical diagnosis and treatment. However, interference signals will be introduced in the process of the signal acquisition, which will affect the accuracy of measurement results. Although the filter can eliminate most of the interference, there will still be a part of the residual interference signal. In order to eliminate these residual interference, this paper proposes a signal denoising method based on ensemble empirical mode decomposition (EEMD), lifting wavelet transform (LWT) and singular spectrum analysis (SSA). Firstly, the measured signal is decomposed by EEMD to obtain multiple modal components (IMF). The high-frequency components are denoised by LWT, and then reconstructed with the low-frequency components. Finally, the SSA is carried out on the reconstructed signal, the appropriate components are selected to reconstruct the signal to obtain the final denoised signal. After testing the EEMD-LWT-SSA method with simulated and measured signals, it can be seen that the method can effectively suppress the residual noise in signals and improve the accuracy of data. [ABSTRACT FROM AUTHOR]

The present paper describes a hyper-spectral polarization imaging system based on a non-collinear, acousto-optic tunable filter (AOTF) and a linear polarizer. The paper begins with an analysis of the equivalent relationship of the AOTF to describe the principle of polarization detection of this system. Appropriate parameters of hardware components are assigned later. This system, being electronically controllable and tunable, can not only ensure the precision of imaging but also obtain hyper-spectral polarization signatures. The prototype has two optional working modes, namely, hyper-spectral polarization imaging and hyper-spectral intensity imaging. Moreover, parameters of this system – such as diffraction efficiency, spectral resolution and modulation precision – are tested using a halogen tungsten lamp and an optical fibre spectrometer. The results indicate that this instrument is compact, vibration-insensitive, robust and precisely controllable. The system designed in this paper has further application in polarization detection techniques in military. [ABSTRACT FROM AUTHOR]

Transmitting a vortex beam (VB) with orbital angular momentum encounters significant aberrations due to atmospheric turbulence (AT) in free-space optical communication systems. Historically, research has focused on adaptive optics (AO) to correct distorted VB intensity distributions by generating phase compensation screens. In this paper, we introduce an image-translation-based machine learning (ML) framework using generative networks to directly produce corrected VB intensity profiles, thus mitigating AT-induced aberrations. Our network was trained with numerical simulation datasets to learn the mapping relationship between distorted and pristine intensity distributions. Subsequently, we evaluated its generalization capabilities using datasets with varied AT conditions and propagation distances. The trained network consistently generated corrected intensity profiles closely matching the desired outcomes, significantly reducing the required training data. Our methodology effectively compensates for distorted VB intensity, achieving a remarkable 40 dB enhancement compared to the distorted profiles. [ABSTRACT FROM AUTHOR]

In this paper, an encryption scheme, based on a double deterministic phase mask and the Yang-Gu algorithm, is proposed. It consists of double random phase encoding and the Yang-Gu algorithm in Fresnel and Fourier transform, respectively. The random phase masks are replaced with deterministic phase masks that are constructed using chaotic logistic and cubic maps. The encrypted image obtained by the scheme in one-way binary modulation is real and more convenient for storage and transmission. The validation of the proposed cryptosystem is carried out using numerical simulations on greyscale images of Man, DICOM and CUH binary images. The proposed scheme is investigated for its robustness through statistical analysis using histograms and correlation plots. The scheme is also tested for its resistance against occlusion, noise and cryptographic attacks. The proposed cryptosystem is found to be highly sensitive to its private key and Fresnel parameters and therefore secure. [ABSTRACT FROM AUTHOR]

Under uneven lighting conditions, power inspection (PI) images captured by drones exhibit low contrast, lost details and severe noise, which affects the efficiency of monitoring. In response to these issues, this paper proposes a new method for enhancing PI images based on discrete fractional wavelet transform (DFRWT). Firstly, according to the image entropy feature, an appropriate fractional order of DFRWT is selected to decompose the PI image. Secondly, we introduce a low-frequency fusion enhancement method based on complex number domain. It employs different mapping functions to enhance the brightness and contrast of PI image, then the results are combined to reconstruct a new low-frequency component. Here, an improved quantum-behaved particle swarm optimization (QPSO) algorithm is proposed to determine the optimal parameters of the functions, preventing over-enhancement. Finally, an adaptive threshold function is applied to handle noise and edge coefficients in high-frequency components. Using 5 quality metrics to evaluate 8 existing algorithms on 9 datasets, the results indicate that the proposed algorithm can effectively enhance the clarity of PI images, performing excellently in noise suppression and edge detail enhancement. [ABSTRACT FROM AUTHOR]

A low-bias operational modified partially depleted absorber photodetector (MPDA-PD) is proposed in this paper. By adopting gradual doping following Gaussian distribution and inserting a buffer layer, the bandwidth-efficiency product and the saturation characteristics of the traditional partially depleted absorber photodetector (PDA-PD) in the low-bias range (0∼1 V) are optimized. When the thickness of the absorption layer is 1200 nm, the 3-dB bandwidth of the MPDA-PD with the diameter of 8 µm reaches 59.1 GHz at 0.6 V. The bandwidth-efficiency product of the MPDA-PD reaches 33.98 GHz, which is 40.6% higher than the traditional PDA-PD in the reference. Meanwhile, the direct-current (DC) saturation current of 121.1 mA and RF output power of −12.2 dBm at 50 GHz are obtained. [ABSTRACT FROM AUTHOR]

In digital holography (DH), the key parameters in the optical path structure, such as diffraction distance, optical path difference and deflection angle, affect greatly the image quality of holographic reconstruction. Thus, it is crucial to determine the appropriate values of parameters. In this paper, the influence of these parameters on the quality of reconstructed images is deeply analysed through the DH principle and numerical simulation. A method to optimize automatically the parameters in the optical path is proposed based on an improved particle swarm optimization algorithm. An experimental setup for reflective off-axis DH is constructed, and coin and optical resolution plate are taken as test samples to perform the experimental research. Experimental results demonstrate that the proposed method can not only effectively enhance the quality of reconstructed images in the light of five indicators but also reduce the complexity and difficulty of adjusting the optical path parameters in the experiments. [ABSTRACT FROM AUTHOR]

Current studies show that binary fringe patterns can be optimized in the phase or intensity domain. The problem with the former is the poor sensitivity to defocusing levels and the problem with the latter is that phase errors can not be restricted efficiently. In this paper, a binary fringe pattern optimization technology, combining intensity similarity and phase similarity, is proposed to improve fringe pattern structure similarity and defocusing robustness. Moreover, a binary patch optimization framework is also proposed to solve the time-consuming problem. Simulation and experiment results show that the proposed optimization can produce binary fringe patterns with high phase quality and defocusing robustness. [ABSTRACT FROM AUTHOR]

Phase measurement profilometry (PMP) is widely used to reconstruct three-dimensional (3D) shape of objects. However, errors are introduced during standard phase unwrapping process, which considerably brings down measurement accuracy and lowers method reliability. This paper proposes a novel method to identify the errors, and subsequently correct these errors through erecting adaptive local windows. Under proposal, two robust algorithms are developed to correct these errors in initial rudimentary correction as well as in subsequent refined error removal. The adaptive local window is designed as such that the fringe order corresponding to each period of the wrapping phase is independent of each other. Therefore, it avoids the error transmission in the correction process. Experiments are carried out on absolute phase error correction and 3D point cloud reconstruction. Experimental results verified the developed method in terms of reducing the stratification of 3D point cloud and improving the quality of 3D measurement. [ABSTRACT FROM AUTHOR]

Traditional multi-view feature extraction methods based on manifold learning frequently overlook the similarity sequence between samples, failing to capture the intrinsic manifold structure of raw nonlinear samples and restricting the recognition performance of multi-view learning. In this paper, we propose a novel similarity-sequenced multi-view discriminant feature extraction method, called Similarity -sequenced Multi-view Discriminant Correlation Analysis (SMDCA), which explicitly considers the sample sequences based on similarity. The method constructs similarity-sequenced discriminant scatters for preserving the sequence structure of within-class samples and develops between-class correlations with the similarity-sequence structure information for further constraining intrinsic manifold structure of cross-view samples. SMDCA can also simultaneously extract low-dimensional sequence features with well-discriminative power from multiple views. Extensive experiments exhibit that SMDCA can provide higher recognition accuracy and stronger robustness in image recognition tasks. [ABSTRACT FROM AUTHOR]

The binary defocusing has been extensively studied in the three-dimensional measurement. But if the projector is slightly defocused, the binary fringes after defocusing still contain high-order harmonics compared with the ideal sinusoidal fringes, so the phase error caused by the nonlinear response is not negligible. In this paper, two models are proposed to calculate and compensate phase error, which include a double-precision iterative compensation model (DPICM) and a dual-domain iterative compensation model (DDICM). These two models obtain accurate phase errors by fusing the phases at different precision and domains. DPICM is composed of the double precision method and the improved iterative algorithm, and DDICM consists of the dual-domain method and the improved iterative algorithm. This improved iterative algorithm is used to compensate phase error, which can improve phase accuracy. DPICM and DDICM reduce the RMS error by 25.5% and 13.5% respectively. [ABSTRACT FROM AUTHOR]

Due to the mismatch between the thermal expansion coefficients of semiconductor laser chip and heat sink, giant thermal stresses will be generated after eutectic bonding. Immoderate thermal stress will cause the devices to produce the smile effect, making the coupling efficiency low. In this paper, we propose an approach to reduce thermal stress and improve the near-field linearity for semiconductor laser arrays. We optimize the eutectic bonding process by controlling the semiconductor laser chip and heat sink in different temperature fields through independent heat sources, to achieve the purpose of matching the shape variables earlier than welding. The heating temperature is determined by Suhir's deformation formula (Suhir E. Stresses in Bi-metal thermostats. J Appl Mech. 1986;53(3):657–660; Suhir E. Stresses in adhesively bonded Bi-material assemblies used in electronic packaging. MRS Proc. 1986;72). Then, finite element Analysis (FEA) was used for simulation verification. [ABSTRACT FROM AUTHOR]

This paper draws arresting conclusions from its analysis of a distinctive, and to the best of my knowledge novel, kinematic construction – an infinite set of inertial coordinate systems that is indexed by a continuous real parameter. It explains how the description of the straight-line trip of a light pulse varies among the members of this infinite set, and also – very importantly – how in my view the trip can be described without referring it to any inertial coordinate system, using coordinate-system-independent kinematic concepts that are implicit in the structure of travelling light. This multitude of comparisons brings out certain features of Einstein's special theory of relativity that are not apparent when kinematic thought is confined to comparing the analytic perspectives of two inertial coordinate systems, as is the custom. It shows that there are reasonable alternatives to the definitions of length, duration, and velocity used by Einstein. It shows that the velocity of light, defined in Einstein's way, varies parabolically over the infinite set of inertial coordinate systems. It provides an attractive coordinate-system-independent explanation of the behaviour of light in Sagnac and modified Sagnac experiments. It elaborates and validates my belief that inertial coordinate systems are commonly misused in a variety of ways. By avoiding these misuses of inertial coordinate systems, physicists can think in less artificial, less arbitrary, more faithful-to-nature ways. [ABSTRACT FROM AUTHOR]

Recently, metal halide perovskite quantum dots (MHPQDs) have attracted considerable interest in sensing activities due to their excellent optoelectronic properties and high surface activity. Here, aiming for heavy metal detection, we proposed an ultrasensitive turn-off fluorescent probe based on MAPbBr3 MHPQDs for the measurement of copper ions in an organic solvent. A low limit of detection (LOD) of 5.6nM was achieved and the test range was recorded from 0nM to 100nM. In order to achieve this high sensitivity, a thin film layer of electrospun polystyrene(PS) nanofibre was introduced for the structural support of MHPQDs, by which the sensitivity increased two orders of magnitude. The quenching mechanism is also discussed in the paper. We believe the electron transfer effect between Cu2+ and perovskite QDs made the main contribution for turn off sensing in our prototype device. [ABSTRACT FROM AUTHOR]

To improve the accuracy of phase recovery in quantitative phase imaging, a novel two-stage synthetic denoising method is proposed in this paper. In this method, to avoid the loss of effective detail information, the mode of fixed attenuation parameter setting is changed into two stages of self-adaptation setting: the first attenuation parameter is defined as the convolution of filtered pixels in the window of interest, the second attenuation parameter is defined as the noise standard deviation of each pixel after filtering in the first stage. Moreover, the Pearson coefficient expression is redefined to get a more accurate similarity evaluation, and the algorithm's operational efficiency has been improved using cross-correlation functions and fast Fourier transform. The comparative results of simulations and experiments show that this method is more effective in reducing speckle noise in quantitative phase imaging and enhancing phase recovery accuracy, providing a new digital image denoizing method for efficient and accurate imaging. [ABSTRACT FROM AUTHOR]

The classification of White blood cells (WBCs) plays an important role. However, the traditional method of blood smear analysis is laborious. This paper presented a classification method of WBCs based on hyperspectral images and Deep learning (DL). The U-net network was proposed to extract spectral features of WBCs region of interest (ROI) under the pseudo-color images with specific hyperspectral images (420.8, 557.2 and 667.4 nm). For spectral features and the pseudo-colour images of hyperspectral data, attention-aided one and two-dimensional convolutional neural networks were applied to establish WBCs classification models, respectively. The overall average accuracy can reach 94.20% and 92.60%, respectively. A fusion network was constructed to make full use of the spectral and image spatial features, and its classification accuracy reached 96.20%. In terms of overall average accuracy, the fusion network model was the optimal, but for individual types of WBCs, each network had its own unique advantages. [ABSTRACT FROM AUTHOR]

Infrared image systems often generate stripe noise because of the non-uniformity of the focal plane array, which significantly reduces the visual quality of the image. To solve this problem, we proposed an effective single-frame denoising method in this paper. First, the wavelet function extracts the approximate and vertical components of the original image containing stripe noise. Then, the approximation component is denoised by parameter estimation, and the vertical component is denoised by guided filtering. Finally, wavelet reconstruction is performed to realize the denoising process of the original image. This method avoids the loss of details of other components of the image and achieves an excellent denoising effect. The experimental results on the public datasets indicate that our proposed method can effectively eliminate the stripe noise of infrared images compared with some advanced methods. [ABSTRACT FROM AUTHOR]

In this paper, we consider a cavity magnomechanical system composed of a microwave (MW) cavity, magnon, and phonon modes, where the magnon is coupled, respectively, to the MW cavity and phonon through both the magnetic-dipole and magnomechanical interactions. We demonstrate that the flux-driven Josephson parametric amplifier with a nonlinear gain is crucial in creating the squeezed states of the magnon and phonon modes. We show that, by the cavity-magnon state-swap interaction, the magnons can be completed in a squeezed state, and that the phonons can also be squeezed by driving the magnons through a strong red-detuned MW field. Essentially, our system reveals a squeezing transfer from cavity photons to magnons and then to phonons. The influence of physical and environmental parameters on the degree of squeezing is widely explored. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a novel kind of periodic helical ultra-long period fiber grating (U-LPFG) for measuring the torsion rate and distinguishing the torsion direction. The sensor was fabricated by spirally deforming a common fiber by local heating for 4 periods. This method of fabrication was not only easy to implement, but also further increased the sensitivity of the grating to the torsion because of the spiral structure. This paper introduced the torsional characteristics of this sensor in detail and drew some relevant conclusions. Experimental results showed that the twist sensitivity of 0.085 nm/(rad/m). Meanwhile, the temperature sensing characteristic of the proposed U-LPFG was also tested as 68 pm/°C within the range of 30 °C ∼210 °C. Therefore, this proposed sensor could achieve good results in simultaneously measuring the torsion rate and distinguishing the torsion direction, and it may have great potential in some practical applications. [ABSTRACT FROM AUTHOR]

Fresnel coefficients are examined for electromagnetic (EM) propagation across an achiral/chiral (ACC) boundary. It is found that upon both transmission and reflection, the incident plane (specifically perpendicularly or s-polarized) wave transforms into two modes (right circular polarization (RCP) and left circular polarization (LCP)), propagating non-collinearly and collinearly for the transmitted and reflected modes respectively. This paper focuses on certain anomalous properties pertinent to the chirality itself which provide novel insights into chiral materials. Thus, it is found that the Brewster effect manifests itself anomalously in this chiral scenario within specific 'bands' of the (dimensionless) chirality coefficient (). Thus, under appropriate chirality, the Brewster angle (θB) and the reflection coefficient profile may be adjusted via tuning, resulting in zero or low reflections under any linear s polarization. The paper also highlights anomalies relative to total internal reflection (TIR), non-complementarity, mode evanescence, and also possible effective negative-index-like behaviour in the chiral material. [ABSTRACT FROM AUTHOR]

This paper addresses the nonlinear Schrödinger equation (NLSE) with Kerr law nonlinearity and perturbation terms in optical fibre. A class of grey and black optical solitary wave solutions of this equation are retrieved by adopting an appropriate solitary wave ansatz solution. These types of solitary waves play a vital role in understanding various physical phenomena in nonlinear systems. This lead to a constraint condition on the solitary wave parameters which must hold for the solitary waves to exist. Moreover, the modulation instability (MI) analysis of the model is studied by employing the concept of linear-stability analysis (LSA) and the MI gain spectrum is got. Physical interpretations of the acquired results are demonstrated. It is hoped that the results reported in this paper can enrich the nonlinear dynamical behaviours of the equation. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the tuning characteristics of a four-layer structure optic fibre Bragg grating (FBG) coated with high refractive index (HRI) overlay. The attention is mainly focused on the analysis of the effects of the mode transition and the mode reorganization on the tuning sensitivity to the overlay HRI of the structure. The cladding diameter of FBG is also considered as a parameter for enhancing the sensitivity of FBG to HRI. Moreover, different cladding modes show different sensitivities. For FBG with negative thermo-optical coefficient coating material, the thermal property of the structure could be effectively suppressed by selecting an optimal fibre cladding diameter. The reported results demonstrate the possibility of this structure can be used as thermal-stable tunable all-fibre photonic device, such as filter, modulator and sensing element. [ABSTRACT FROM AUTHOR]

Photons, i.e. the basic energy quanta of monochromatic waves, are highly non-localized and occupy all available space in one dimension. This non-local property can complicate the modelling of the quantized electromagnetic field in the presence of optical elements that are local objects. Therefore, in this paper, we take an alternative approach and quantize the electromagnetic field in position space. Taking into account the negative- and the positive-frequency solutions of Maxwell's equations, we construct annihilation operators for highly localized field excitations with bosonic commutator relations. These provide natural building blocks of wave packets of light and enable us to construct locally acting interaction Hamiltonians for two-sided semi-transparent mirrors. [ABSTRACT FROM AUTHOR]