Optik最新文献

{"title":"Enhancing FSO SISO links performance under adverse atmospheric conditions using CPPM-based DS-OCDMA: Simulation and experimental validation","authors":"Mohammed Amine Benbouzid,&nbsp;Nabil Belghachem,&nbsp;Abdelwahid Boutemejet,&nbsp;Djamal Teguig","doi":"10.1016/j.ijleo.2025.172318","DOIUrl":"10.1016/j.ijleo.2025.172318","url":null,"abstract":"<div><div>Free Space Optical (FSO) communication systems are a cost-effective solution for high-speed, secure data transmission with extensive bandwidth capabilities. However, their performance is significantly affected by atmospheric conditions, leading to challenges such as scintillation and transmission disruptions due to the inherent characteristics of photons. Recent research has focused on identifying modulation techniques that are resistant to scintillation to ensure reliable data transmission while maximizing user capacity per channel. This paper examines the use of Direct Sequence Optical Code Division Multiple Access (DS-OCDMA) in FSO links. We introduce Chaotic Pulse Position Modulation (CPPM) as a novel approach for generating DS-OCDMA sequences to enhance FSO link performance under adverse atmospheric conditions. Using Monte Carlo simulations for FSO Single Input Single Output (SISO) links, modeled with the Gamma-Gamma distribution to account for scintillation, we demonstrate that CPPM-modulated DS-OCDMA significantly outperforms conventional codes in terms of resilience to atmospheric turbulence, as evidenced by improvements in Bit Error Rate (BER). This paper also presents experimental results obtained from a fully functional, custom-built testbed designed to emulate an FSO SISO DS-OCDMA link in foggy conditions. These experimental findings not only validate the simulation results but also underscore the practical effectiveness of the proposed CPPM-modulated DS-OCDMA approach.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172318"},"PeriodicalIF":3.1,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metasurface reflector-inspired directional bow-tie antenna for IoT and wireless applications","authors":"Tejaswita Kumari,&nbsp;Anupama Senapati,&nbsp;Abu Nasar Ghazali","doi":"10.1016/j.ijleo.2025.172309","DOIUrl":"10.1016/j.ijleo.2025.172309","url":null,"abstract":"<div><div>The present paper deals with design and realization of the metasurface-reflector, high-gain directional ultra-wideband (UWB) bowtie antenna for the applications of IoT and wireless communication. There will be a modified patch along with a symmetrical hexagonal-shaped metasurface (MTS) reflector that has a design 3 × 6 array and is loaded on the back and top sides. First, the proposed design features an ultra-wideband bowtie antenna with a superellipse-shaped bow along with staircase structures. Then, the antenna becomes directional due to the metasurface loading on its backside, after that placing same metasurface on the front side enhances the directional gain. The dimension of the antenna is <span><math><mrow><mn>2</mn><mo>.</mo><mn>44</mn><msub><mrow><mi>λ</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>×</mo><mn>1</mn><mo>.</mo><mn>12</mn><msub><mrow><mi>λ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span> and the fractional bandwidth is 97.44%. The maximum gain achieved by the antenna is 10.1 dBi, and the efficiency of the proposed antenna is 95.5%. This proposed compact antenna optimizes both gain and bandwidth for the requirements of IoT, UWB wireless operation, and 6G complementary networks.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172309"},"PeriodicalIF":3.1,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-precision liquid crystal cell gap estimation via machine learning","authors":"Chi-Yen Huang ,&nbsp;Bo-Lin Huang ,&nbsp;Su-Yu Liao ,&nbsp;Yu-Yun Huang ,&nbsp;Yu-Ling Ma ,&nbsp;Pei-Te Lin ,&nbsp;Jiann-Heng Chen ,&nbsp;Che-Ju Hsu ,&nbsp;Chun-Ying Huang","doi":"10.1016/j.ijleo.2025.172314","DOIUrl":"10.1016/j.ijleo.2025.172314","url":null,"abstract":"<div><div>Liquid crystal (LC) cell gap measurement is crucial for determining key electro-optical properties, but traditional methods are often time-consuming and complex. In this study, we present the application of a multilayer perceptron (MLP) model for predicting empty LC cell gaps using spectral data. The proposed MLP model achieves high predictive accuracy, with correlation coefficients exceeding 0.99 and a mean squared error (MSE) of approximately 0.6 across various conditions. Different training algorithms, activation functions, and weight decay parameters were systematically tested to optimize performance. Experimental results showed that the MLP model achieved low MSE values while maintaining robustness under varying random seeds and train-test split ratios, confirming its strong generalization capability. This approach simplifies the cell gap measurement process and highlights the potential of machine learning for advancing LC device characterization, offering a reliable and efficient alternative to conventional methods.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172314"},"PeriodicalIF":3.1,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic modulation of terahertz photonic orbital angular momentum superposition states based on vanadium dioxide metasurface","authors":"Rongrui Shi,&nbsp;Dongdong Wei,&nbsp;Fuguo Wang,&nbsp;Hang Xu,&nbsp;Xin Ding,&nbsp;Jianquan Yao","doi":"10.1016/j.ijleo.2025.172312","DOIUrl":"10.1016/j.ijleo.2025.172312","url":null,"abstract":"<div><div>The combined state of photonic orbital angular momentum (OAM) offers more degrees of freedom compared to an OAM state, revealing rich physical implications and significant engineering potential. In this paper, we propose a dynamic control scheme employing a VO₂ metasurface to generate two polarization-dependent OAM channels, enabling multiplexed terahertz OAM superposition states. This design doubles channel capacity and supports dynamic switching between superposition and single OAM states via VO₂ phase transitions. We designed and simulated two types of OAM-superposition metasurface generators. The first design features a VO₂-Au hybrid array structure, capable of flexibly switching between various OAM superposition states and a single OAM state. The second design consisted of a metasurface array composed of VO₂ units, allowing for dynamic control over the activation and deactivation of multiple OAM superposition states. Furthermore, the proposed metasurfaces enable the generation of longitudinal electric field components and the dynamic control of OAM superposition states. The proposed scheme employs a single metasurface to achieve multifunctional dynamic control, and offers a novel approach and methodology for photonic OAM manipulation.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172312"},"PeriodicalIF":3.1,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unveiling the potential of Ca₃PBr₃ perovskite for solar applications: A study of structural, mechanical, electronic and optical properties","authors":"Chakshu Malan ,&nbsp;Krishna Kumar Mishra ,&nbsp;Rajnish Sharma","doi":"10.1016/j.ijleo.2025.172310","DOIUrl":"10.1016/j.ijleo.2025.172310","url":null,"abstract":"<div><div>Perovskite materials have garnered significant interest because of their remarkable structural, electronic and optical properties which make them highly suitable choice for various applications. This work provides a thorough analysis of the Ca₃PBr₃ perovskite using Quantum ATK tool while employing density functional theory (DFT) approximations. The results from this study provide the electronic characteristics of the material, particularly its ability to conduct electricity. The calculated lattice constant of the material is 5.96 Å. The objective of the research is to investigate the impact of Ca₃PBr₃'s structural, mechanical, electronic, and optical properties using first-principles density functional theory. Ca₃PBr₃ has been found to possesses direct band gap of 1.682 eV. The LCAO calculator was employed to analyse the characteristics using the GGA (Generalized Gradient Approximation) and PBE (Perdew–Burke–Ernzerhof) functionals. In order to evaluate the structural characteristics, it is essential to determine the lattice parameter (a), atomic locations and density of states (DOS), elastic constants (C₁₁, C₁₂, and C₄₄), together with the bulk, shear and Young's moduli. The Ca₃PBr₃ material has been found to exhibit optical properties, with a calculated reflectivity of 0.044. Furthermore, the material's susceptibility is 2.2831. In addition to its capability to alter optical properties, this makes Ca₃PBr₃ an additional possibility that is interesting for use in optical systems.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172310"},"PeriodicalIF":3.1,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Double Hilbert transform based nonlinear harmonics correction for fringe projection profilometry","authors":"Beibei Wang ,&nbsp;Huanghe sun ,&nbsp;Chaoguang Huang ,&nbsp;Wenbin Huang ,&nbsp;Haijian Wang ,&nbsp;Wenjie Li","doi":"10.1016/j.ijleo.2025.172287","DOIUrl":"10.1016/j.ijleo.2025.172287","url":null,"abstract":"<div><div>Fringe projection profilometry (FPP) has the advantages of large field of view, high precision and resolution, and is widely used in industrial inspection, medical treatment, aerospace and other fields. The nonlinear response between the camera and the projector in the system will affect the sinusoidal intensity of the captured fringe images, produce periodic phase errors, and affect the final reconstruction accuracy. Traditional double N-step phase shift (NPS) and Hilbert transform (HT) methods only correct the fundamental harmonic part of the phase nonlinear errors, and ignore the rest of the higher harmonic. Therefore, a double HTs based nonlinear phase error correction method is proposed, taking the higher order nonlinear harmonics into account. The artificial sinusoidal fringe images without background term are constructed using the wrapped phase calculated by captured fringe images. Then the HT is performed to convert the phase error to multiplication from addition, which can realize error balance in phase calculation. After obtaining the new phase, reoperation of artificial fringe generation and HT (AHT) is carried out to effectively remove the high order harmonic part of nonlinear harmonics. In proposed method, the wrapped phase calculated by captured fringe images is directly used to generate the artificial fringe images, which does not require additional projection patterns and realize real-time correction of phase nonlinear errors with high accuracy. Furthermore, direct artificial fringe generation also can efficiently avoids the effect of background intensity to the HT. Theoretical analysis, simulation analysis and experimental verification all prove the feasibility and superiority of the proposed method.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172287"},"PeriodicalIF":3.1,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143644355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced image security through chaotic system-based encryption and fisher-yates matrix shuffling","authors":"Shubham Jain ,&nbsp;Arpita Samal ,&nbsp;Ananya Sharma ,&nbsp;Mehak Khurana ,&nbsp;Bhavana Sharma","doi":"10.1016/j.ijleo.2025.172304","DOIUrl":"10.1016/j.ijleo.2025.172304","url":null,"abstract":"<div><div>Traditional encryption approaches often exhibit vulnerabilities to differential, noise, and statistical attacks, and may expose patterns in encrypted images, compromising confidentiality and promoting unauthorized access. With rapid development of technology and inevitable rise of security challenges, it becomes important to secure sensitive image data against unauthorized access and sophisticated attacks, ensuring confidentiality, integrity, and resilience in high-security applications. This paper aims to provide a robust, efficient, and secure solution for protecting sensitive image data against attacks. The proposed asymmetric image encryption technique introduces a fusion of innovative methods, including the utilization of the chaotic behavior of the Lorenz and Logistic maps, along with pixel permutation and shuffling using fisher yates shuffling algorithm. This approach not only harnesses the power of chaotic systems for generating robust non periodic encryption keys but also leverages a pseudo-random manner of matrix shuffling techniques to enhance the confidentiality of image data. The algorithm divides the image into 16 horizontal bits and applies Lorenz encryption on 8 bits and logistic encryption on the remaining 8 bits. Then fisher-yate’s algorithm is applied on them along with vertical division of image into 16 bits. The algorithm uses 4 decryption keys without which the attacker cannot recover the original image. The effectiveness of the proposed encryption algorithm is evaluated through extensive simulation experiments, which demonstrate its superior performance in terms of various attacks like differential attack, noise attack, blocking attack, etc. The proposed encryption technique focuses on enhanced security, unpredictable robust key generation, advanced pixel shuffling and multi key protection to provide a reliable and efficient approach for securing image data, which can be useful in various applications such as military, medical, and financial imaging systems and many more.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172304"},"PeriodicalIF":3.1,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An infrared image enhancement method based on Multi-Channel Feature Fusion Network","authors":"Boyuan Chen ,&nbsp;Yumeng Song ,&nbsp;Gang Yang ,&nbsp;Xiaoyong Lyu ,&nbsp;Yuliang Zhao","doi":"10.1016/j.ijleo.2025.172306","DOIUrl":"10.1016/j.ijleo.2025.172306","url":null,"abstract":"<div><div>With the rise of computer vision, there is an urgent demand for high-quality infrared images in various fields, characterized by appropriate contrast, high brightness, and detailed texture. However, the challenge in acquiring infrared images of high quality lies in how to effectively improve contour and detail information while eliminating noise interference. Therefore, an infrared image enhancement method is proposed and based on Multi-Channel Feature Fusion Network (MCFFNet), which consists of three channels and two fusion modules. First, the contour enhancement channel extracts foreground information from the original infrared images to separate the contour from the background. Second, the detail enhancement channel is designed to extract intrinsic information from the input, enriching texture details. Third, the noise processing channel is utilized to restrain background noise and improve brightness and contrast. Finally, the enhanced infrared image is obtained through two fusion modules, which integrate the information obtained by the three channels. Extensive subjective and objective comparative experiments have demonstrated significant improvements in contrast, brightness, and texture details of the infrared images processed by this method. Compared to original image, standard deviation (STD) and average gradient(AG) produced by the proposed method are up to 53.4645 and 14.2594, increased by 37.27% and 105.42% respectively, which shows its efficiency for infrared image enhancement.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172306"},"PeriodicalIF":3.1,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143628250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hybrid image encryption algorithm based on Galois fields and chaotic structures","authors":"Tanveer Qayyum,&nbsp;Tariq Shah","doi":"10.1016/j.ijleo.2025.172302","DOIUrl":"10.1016/j.ijleo.2025.172302","url":null,"abstract":"<div><div>Almost every industry relies heavily on images, including the medical field, video conferencing, weather forecasting, the military, and most social media applications. Attackers can hack and obtain sensitive data that is not encrypted or has inadequate security due to the widespread use of modern technology. Securely transmitting secret images through an unreliable network necessitates using a solid image cryptosystem. This paper presents a novel image encryption algorithm that synergistically combines the mathematical robustness of Galois fields with the dynamic complexity of Allee’s effect-influenced logistic maps. The proposed method leverages the properties of Galois fields to enhance cryptographic security and operational efficiency. At the same time, the Allee’s effect, integrated into logistic maps, introduces a new dimension of chaotic behaviour that intensifies encryption unpredictability. Our approach begins with an image preprocessing phase using Galois field transformations to disperse pixel values uniformly. Elements of <span><math><mrow><mi>G</mi><mi>F</mi><mrow><mo>(</mo><msup><mrow><mn>2</mn></mrow><mrow><mn>8</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> are applied to Allee’s effect with a logistic map to obtain substitution boxes of high non-linearity. These boxes are used for substitution and permutation purposes. A two-dimensional logistic map generates the key for the bitwise XOR operation. Comparative analyses with existing encryption techniques demonstrate that our algorithm offers superior resistance to common cryptographic attacks, including statistical, differential, and brute-force attacks. Experimental results highlight the algorithm’s capability to maintain image quality and integrity post-decryption, making it a viable solution for secure image transmission in diverse applications. Integrating Galois fields and Allee’s effect in logistic maps establishes a robust framework for advancing image encryption methodologies.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"327 ","pages":"Article 172302"},"PeriodicalIF":3.1,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ensemble knowledge distillation for collaborative pseudo-label refinement in unsupervised domain adaptation for person re-identification","authors":"Sidharth Samanta ,&nbsp;Debasish Jena ,&nbsp;Suvendu Rup","doi":"10.1016/j.ijleo.2025.172303","DOIUrl":"10.1016/j.ijleo.2025.172303","url":null,"abstract":"<div><div>In open-world person re-identification, obtaining annotated ground truth for every deployment environment is infeasible which necessitates the exploration of unsupervised domain adaptation methods. The Pseudo-label guided approaches leverage clustering methodologies for the generation of pseudo-labels to facilitate model retraining on the unlabeled target domain. However, the robustness of these methodological approaches is vulnerable in the presence of label noise, which is generated due to the domain shift, specifically, the interplay of intra-domain similarity within the source domain and the inter-domain dissimilarity between the source and target domains. This study introduces a novel learning scheme to enhance the robustness of such cross-domain re-identification models by minimizing the label noise through collaborative refinement utilizing the amalgamation of multiple teacher outputs and subsequent network training with the refined pseudo-labels. To obtain diverse perspectives, domain-adapted teacher networks of varying types and sizes are employed, and subsequently, their outcomes are amalgamated through a dynamic averaging method to yield a refined representation. A comprehensive set of ablation studies systematically analyzes the contributions of each component, highlighting the vital roles of clustering, knowledge distillation, collaborative refinement, and optimal ensemble size. Furthermore, the proposed model undergoes rigorous evaluation on widely used datasets, such as Market1501, DukeMTMC, and MSMT17, demonstrating superior performance compared to existing state-of-the-art methods. The mean Average Precision (mAP) and Rank-1 (R1) scores showcase notable improvements, with results indicating an enhanced performance in Duke to Market (mAP: 81.04, R1: 90.84) and Market to Duke (mAP: 76.24, R1: 86.27) scenarios.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"328 ","pages":"Article 172303"},"PeriodicalIF":3.1,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143759045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}