Pub Date : 2024-10-01DOI: 10.1016/j.optlaseng.2024.108622
Honeycomb structures have attracted much attention in various engineering fields due to its superiorities in high specific strength, high specific stiffness and excellent energy-absorbing characteristics. Therefore, it is very important to obtain the deformation state of honeycomb structure in the studies of its manufacturing process and mechanical behavior. In this study, a simple and efficient strategy for tracking the deformation of thin-walled honeycomb structure based on image skeletonization and branch points matching is presented. Principle and process of the new proposed strategy are first detailed, including image skeletonization, branch points selection, matching expansion and deformation calculation, etc. Simulations and experiments with compression and tensile deformations are performed to verify the efficiency of the proposed strategy. The results indicate that the displacement measurements based on the proposed strategy are able to provide subpixel-level accuracy, even though some interference branch points are generated during deformation. In addition, the limitations of the proposed strategy are discussed, which points out the train of thought for the subsequent research.
{"title":"Deformation tracking of honeycomb structure based on image skeletonization and branch point matching","authors":"","doi":"10.1016/j.optlaseng.2024.108622","DOIUrl":"10.1016/j.optlaseng.2024.108622","url":null,"abstract":"<div><div>Honeycomb structures have attracted much attention in various engineering fields due to its superiorities in high specific strength, high specific stiffness and excellent energy-absorbing characteristics. Therefore, it is very important to obtain the deformation state of honeycomb structure in the studies of its manufacturing process and mechanical behavior. In this study, a simple and efficient strategy for tracking the deformation of thin-walled honeycomb structure based on image skeletonization and branch points matching is presented. Principle and process of the new proposed strategy are first detailed, including image skeletonization, branch points selection, matching expansion and deformation calculation, etc. Simulations and experiments with compression and tensile deformations are performed to verify the efficiency of the proposed strategy. The results indicate that the displacement measurements based on the proposed strategy are able to provide subpixel-level accuracy, even though some interference branch points are generated during deformation. In addition, the limitations of the proposed strategy are discussed, which points out the train of thought for the subsequent research.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.optlaseng.2024.108612
In this paper, the transmitted digital gradient sensing (DGS) technique is applied to analyze stress singularity at the tip of an arbitrary oriented crack in a cylindrical shell. A thoretical model of the opitcal path near the tip of the inclined crack in a cylindrical shell under mixed-mode fracture is proposed based on the geometric optical imaging principle. An optical governing equation of DGS technique is established to relate the mixed-mode stress intensity fractors (SIFs) at the crack tip to the shell geometry parameters and the inclined crack sizes, and the angular deflection contours are theoretically plotted using this govering equation. Uniaxial tensile tests are carried out on polymethyl methacrylate (PMMA) cylindrical shells containing an edge crack with different inclined angles, and the optimal calculation area for the exaction of SIFs is determined from linear elasitic fracture mechanics. The effects of shell radius, shell thick, crack length, and crack angle on the mixed-mode SIFs are studied, respectively. These results show that the DGS technique is effective and accurate to evalute the stress singulary around an arbitrary oriented cracks in cylindrical shells.
{"title":"Study on stress singularities in cylindrical shells with an arbitrary oriented crack using digital gradient sensing technique","authors":"","doi":"10.1016/j.optlaseng.2024.108612","DOIUrl":"10.1016/j.optlaseng.2024.108612","url":null,"abstract":"<div><div>In this paper, the transmitted digital gradient sensing (DGS) technique is applied to analyze stress singularity at the tip of an arbitrary oriented crack in a cylindrical shell. A thoretical model of the opitcal path near the tip of the inclined crack in a cylindrical shell under mixed-mode fracture is proposed based on the geometric optical imaging principle. An optical governing equation of DGS technique is established to relate the mixed-mode stress intensity fractors (SIFs) at the crack tip to the shell geometry parameters and the inclined crack sizes, and the angular deflection contours are theoretically plotted using this govering equation. Uniaxial tensile tests are carried out on polymethyl methacrylate (PMMA) cylindrical shells containing an edge crack with different inclined angles, and the optimal calculation area for the exaction of SIFs is determined from linear elasitic fracture mechanics. The effects of shell radius, shell thick, crack length, and crack angle on the mixed-mode SIFs are studied, respectively. These results show that the DGS technique is effective and accurate to evalute the stress singulary around an arbitrary oriented cracks in cylindrical shells.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-28DOI: 10.1016/j.optlaseng.2024.108610
Structural light vision sensing is widely applied in online detecting defects of laser processing due to their anti-interference ability for laser beams. However, the existing algorithms cannot extract the characteristics of weld defects with high precision. The computing cost of large-scale point cloud data is high. The balance between them is the main challenge to achieve online detection. To improve accuracy and reduce computation costs, this study uses point cloud data with depth information and proposes a point cloud segmentation method. It is a novelty method based on PointNet framework that has been verified for laser welding defect detection. Specifically, it used the PointNet framework as the backbone. It extracted enough local features of weld defects by multi-scale feature fusion, which concatenated features from different feature extraction layers to learn enough features to improve detection accuracy. The experiments were conducted on the real dataset of welds. The results showed its competitive performance in weld bead measurement and classification segmentation, and the accuracy of this method is 97.4 %. The proposed method improved mean intersection-over-union (mIoU) by 2.1 % compared with its backbone (PointNet), indicating a better segmentation accuracy. In addition, the proposed method improved detection speed compared with PointNet++. It can reach 60 frames per second, 7.5 times faster than PointNet++ and meet the online monitoring requirements. To conclude, the new detection method based on the improved PointNet with higher accuracy and faster speed of detection has a wide application prospect thanks to its novel model.
{"title":"Improved PointNet with accuracy and efficiency trade-off for online detection of defects in laser processing","authors":"","doi":"10.1016/j.optlaseng.2024.108610","DOIUrl":"10.1016/j.optlaseng.2024.108610","url":null,"abstract":"<div><div>Structural light vision sensing is widely applied in online detecting defects of laser processing due to their anti-interference ability for laser beams. However, the existing algorithms cannot extract the characteristics of weld defects with high precision. The computing cost of large-scale point cloud data is high. The balance between them is the main challenge to achieve online detection. To improve accuracy and reduce computation costs, this study uses point cloud data with depth information and proposes a point cloud segmentation method. It is a novelty method based on PointNet framework that has been verified for laser welding defect detection. Specifically, it used the PointNet framework as the backbone. It extracted enough local features of weld defects by multi-scale feature fusion, which concatenated features from different feature extraction layers to learn enough features to improve detection accuracy. The experiments were conducted on the real dataset of welds. The results showed its competitive performance in weld bead measurement and classification segmentation, and the accuracy of this method is 97.4 %. The proposed method improved mean intersection-over-union (mIoU) by 2.1 % compared with its backbone (PointNet), indicating a better segmentation accuracy. In addition, the proposed method improved detection speed compared with PointNet++. It can reach 60 frames per second, 7.5 times faster than PointNet++ and meet the online monitoring requirements. To conclude, the new detection method based on the improved PointNet with higher accuracy and faster speed of detection has a wide application prospect thanks to its novel model.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-27DOI: 10.1016/j.optlaseng.2024.108603
In this paper, a dual-channel dispersive interferometer using femtosecond laser is developed with a reference long optical fiber. The width spectrum of the femtosecond laser is divided into a ranging channel and a monitor channel using a coarse wavelength division multiplexer. The ranging channel uses long fiber to construct an unbalanced interferometer to eliminate measurement dead zone by changing the repetition frequency. The monitor channel can measure the fluctuation of long optical fiber in real-time. The dual-channel interference signal then can be received by one single spectrometer. The optical path drift of the long fiber-based reference path can be synchronously compensated to achieve high-precision ranging. In experiments, a 116 m long optical fiber was compensated to 3 × 10−8 stability for one hour. Compared with a commercial interferometer, the ranging accuracy is better than ±4 μm within a range of 300 mm.
{"title":"Absolute distance measurement without dead zone based on dual-channel dispersive interferometry using the femtosecond laser","authors":"","doi":"10.1016/j.optlaseng.2024.108603","DOIUrl":"10.1016/j.optlaseng.2024.108603","url":null,"abstract":"<div><div>In this paper, a dual-channel dispersive interferometer using femtosecond laser is developed with a reference long optical fiber. The width spectrum of the femtosecond laser is divided into a ranging channel and a monitor channel using a coarse wavelength division multiplexer. The ranging channel uses long fiber to construct an unbalanced interferometer to eliminate measurement dead zone by changing the repetition frequency. The monitor channel can measure the fluctuation of long optical fiber in real-time. The dual-channel interference signal then can be received by one single spectrometer. The optical path drift of the long fiber-based reference path can be synchronously compensated to achieve high-precision ranging. In experiments, a 116 m long optical fiber was compensated to 3 × 10<sup>−8</sup> stability for one hour. Compared with a commercial interferometer, the ranging accuracy is better than ±4 μm within a range of 300 mm.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-26DOI: 10.1016/j.optlaseng.2024.108597
Lensless imaging systems have gained significant attention recently due to their advantages in terms of reduced size and weight compared to traditional lens-based systems. However, like other imaging methods, lensless imaging encounters challenges in resolving scenes with more details. In this article, we propose a novel four-frame super-resolution method specifically tailored for lensless imaging systems. Our approach shares similarities with previous lensless imaging systems, involving a sensor and a modulation device placed in front of the image sensor. We develop an explicit degradation downsampling model with sub-pixel shifts and provide the solution to corresponding inverse problem, may offering valuable guidance for other super-resolution imaging algorithms based on spatial displacements. By applying random lateral sub-pixel shifts, acquiring four low-resolution (LR) images, and fusing their spatial information, we achieve high-resolution (HR) sensor recordings, enabling super-resolution reconstruction of the imaging scene. Numerical simulations demonstrate approximately an improvement in spatial resolution compared to single-measurement methods. Furthermore, we evaluate the performance of our method across various lensless imaging systems utilizing different masks, validating its versatility and effectiveness in achieving higher resolution outcomes. Experimental results also support our proposed scheme's ability to achieve higher spatial resolution reconstruction in a real system.
{"title":"Four-frame pixel super-resolution method for lensless imaging systems","authors":"","doi":"10.1016/j.optlaseng.2024.108597","DOIUrl":"10.1016/j.optlaseng.2024.108597","url":null,"abstract":"<div><div>Lensless imaging systems have gained significant attention recently due to their advantages in terms of reduced size and weight compared to traditional lens-based systems. However, like other imaging methods, lensless imaging encounters challenges in resolving scenes with more details. In this article, we propose a novel four-frame super-resolution method specifically tailored for lensless imaging systems. Our approach shares similarities with previous lensless imaging systems, involving a sensor and a modulation device placed in front of the image sensor. We develop an explicit degradation downsampling model with sub-pixel shifts and provide the solution to corresponding inverse problem, may offering valuable guidance for other super-resolution imaging algorithms based on spatial displacements. By applying random lateral sub-pixel shifts, acquiring four low-resolution (LR) images, and fusing their spatial information, we achieve high-resolution (HR) sensor recordings, enabling super-resolution reconstruction of the imaging scene. Numerical simulations demonstrate approximately an improvement in spatial resolution compared to single-measurement methods. Furthermore, we evaluate the performance of our method across various lensless imaging systems utilizing different masks, validating its versatility and effectiveness in achieving higher resolution outcomes. Experimental results also support our proposed scheme's ability to achieve higher spatial resolution reconstruction in a real system.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-26DOI: 10.1016/j.optlaseng.2024.108598
This study introduces a novel method for decomposing polarization aberrations. It uses two sets of reduction matrices to decompose the diattenuation and retardance Mueller matrix into five independent reduction coefficients. And then, it uses Zernike polynomials to decompose these coefficients at the exit pupil, thereby providing a method for quantitatively analyzing the polarization aberrations. This method also gives the constraint values of the Zernike term of polarization aberrations during astronomical telescope design. Finally, the effectiveness and correctness of the process are verified by simulation of the actual optical system, pointing out that the D1, D2, D3, and R5 terms need to be calibrated and optimized to ensure polarization accuracy. This method offers a valuable tool and theoretical guidance for the polarization design of high-precision optical systems.
{"title":"The Mueller pupils Reduction-Zernike polynomial decomposition and polarization design criteria for the astronomical telescope system","authors":"","doi":"10.1016/j.optlaseng.2024.108598","DOIUrl":"10.1016/j.optlaseng.2024.108598","url":null,"abstract":"<div><div>This study introduces a novel method for decomposing polarization aberrations. It uses two sets of reduction matrices to decompose the diattenuation and retardance Mueller matrix into five independent reduction coefficients. And then, it uses Zernike polynomials to decompose these coefficients at the exit pupil, thereby providing a method for quantitatively analyzing the polarization aberrations. This method also gives the constraint values of the Zernike term of polarization aberrations during astronomical telescope design. Finally, the effectiveness and correctness of the process are verified by simulation of the actual optical system, pointing out that the <em>D</em><sub>1</sub>, <em>D</em><sub>2</sub>, <em>D</em><sub>3</sub>, and <em>R</em><sub>5</sub> terms need to be calibrated and optimized to ensure polarization accuracy. This method offers a valuable tool and theoretical guidance for the polarization design of high-precision optical systems.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-25DOI: 10.1016/j.optlaseng.2024.108604
In this paper, we introduce an iterative correcting algorithm for phase demodulation in optical metrology via phase-shifting interferometry. The scheme can effectively cope with interferograms with both temporal intensity variations and non-uniformly spaced phase shifts. When the background intensity and fringe visibility vary only over time while spatially remaining constants, our approach can iteratively estimate and correct them. For each iteration, we propose retrieving the phase shifts and the temporal variations, and then we extract the phase map from the corrected interferograms. We provide the spectral analysis of the method according to the frequency transfer function (FTF) formalism for phase-shifting algorithms. Results show that our scheme can accurately retrieve the phase map where the demodulation errors are unintelligible. Additionally, our method has computational time comparable to state-of-the-art iterative algorithms for non-uniformly phase-shifted interferograms, converging rapidly within ten iterations.
{"title":"Iteratively correcting algorithm for suppressing temporal variations in phase-shifting interferometry","authors":"","doi":"10.1016/j.optlaseng.2024.108604","DOIUrl":"10.1016/j.optlaseng.2024.108604","url":null,"abstract":"<div><div>In this paper, we introduce an iterative correcting algorithm for phase demodulation in optical metrology via phase-shifting interferometry. The scheme can effectively cope with interferograms with both temporal intensity variations and non-uniformly spaced phase shifts. When the background intensity and fringe visibility vary only over time while spatially remaining constants, our approach can iteratively estimate and correct them. For each iteration, we propose retrieving the phase shifts and the temporal variations, and then we extract the phase map from the corrected interferograms. We provide the spectral analysis of the method according to the frequency transfer function (FTF) formalism for phase-shifting algorithms. Results show that our scheme can accurately retrieve the phase map where the demodulation errors are unintelligible. Additionally, our method has computational time comparable to state-of-the-art iterative algorithms for non-uniformly phase-shifted interferograms, converging rapidly within ten iterations.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-24DOI: 10.1016/j.optlaseng.2024.108607
With the advancement of imaging technology, macrophotography images (MPIs) have become a popular research topic. Unlike natural images, MPIs often feature sharp foregrounds and blurred backgrounds, leading to distinct perceptual characteristics in estimation. As the number of MPIs grows rapidly, concerns over image quality and security increase. Robust watermarking techniques have been introduced to address these challenges. Just Noticeable Difference (JND) has been widely used in quantization-based watermarking frameworks. However, existing JND models handle each image area with a single-level perceptual attention. Visual attention in Quaternion Discrete Wavelet Transform (QDWT), which can reflect the Multi-level perceptual attention feature. Therefore, we propose a new method called Quaternion Attention-based Just Noticeable Difference model for MPIs Watemarking (QAJnd-MW) for watermarking MPIs. This method uses visual attention mechanisms, recognizing that the HVS is more sensitive to attention regions. We generate a masking effect in the JND field. The input image undergoes QDWT to explore multi-scale features. The multi-scale feature maps, with multi-directional luminance and multi-channel color, help create local and global attention maps, which are fused to form the final attention map. Specifically, considering both attention-based masking effects, the quaternion attention-guided JND model is designed for a robust MPI watermarking framework, aiming to further improve MPI security. Extensive experiments on the MP2020 and Blur Detection datasets show that the proposed model significantly improves robustness against JPEG compression attacks, reducing the bit error rate (BER) by up to 12%. Additionally, the model performs well against other attacks, such as those in online social networks, with lower BER than current state-of-the-art techniques.
{"title":"Quaternion attention-based JND model for macrophotography image watermarking","authors":"","doi":"10.1016/j.optlaseng.2024.108607","DOIUrl":"10.1016/j.optlaseng.2024.108607","url":null,"abstract":"<div><div>With the advancement of imaging technology, macrophotography images (MPIs) have become a popular research topic. Unlike natural images, MPIs often feature sharp foregrounds and blurred backgrounds, leading to distinct perceptual characteristics in estimation. As the number of MPIs grows rapidly, concerns over image quality and security increase. Robust watermarking techniques have been introduced to address these challenges. Just Noticeable Difference (JND) has been widely used in quantization-based watermarking frameworks. However, existing JND models handle each image area with a single-level perceptual attention. Visual attention in Quaternion Discrete Wavelet Transform (QDWT), which can reflect the Multi-level perceptual attention feature. Therefore, we propose a new method called <strong>Q</strong>uaternion <strong>A</strong>ttention-based <strong>J</strong>ust <strong>N</strong>oticeable <strong>D</strong>ifference model for <strong>M</strong>PIs <strong>W</strong>atemarking <strong>(QAJnd-MW)</strong> for watermarking MPIs. This method uses visual attention mechanisms, recognizing that the HVS is more sensitive to attention regions. We generate a masking effect in the JND field. The input image undergoes QDWT to explore multi-scale features. The multi-scale feature maps, with multi-directional luminance and multi-channel color, help create local and global attention maps, which are fused to form the final attention map. Specifically, considering both attention-based masking effects, the quaternion attention-guided JND model is designed for a robust MPI watermarking framework, aiming to further improve MPI security. Extensive experiments on the MP2020 and Blur Detection datasets show that the proposed model significantly improves robustness against JPEG compression attacks, reducing the bit error rate (BER) by up to 12%. Additionally, the model performs well against other attacks, such as those in online social networks, with lower BER than current state-of-the-art techniques.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-23DOI: 10.1016/j.optlaseng.2024.108606
In recent years, there has been growing interest in the utilization of terahertz (THz) technologies in telecommunications applications. In such systems, radiation multiplexing is required. In one of the solutions, multiplexing can be achieved through the application of appropriate passive optical components. In this study, three different designs of passive diffractive optical elements (DOEs) that meet the functionality of spatial multiplexing of THz radiation are presented. The functionality was achieved by combining two spatially separated optical channels into a single optical path with an addition of the focusing effect, creating multiple-input single-output (MISO) system performance. Two structures were designed as various combinations of off-axis segmentation of kinoform focusing lenses with particular shifts. However, the distribution of the third structure was created with the interactive algorithm. The performance of all structures was verified with numerical simulations using propagation based on the modified convolution method, giving promising results. In this study, the novel, specially dedicated method of 3D modeling was applied. MISO structures were manufactured using fused deposition modeling (FDM) 3D printing technology from styrene-butadiene copolymer (SBC) material, which is remarkably transparent for the THz radiation range (its absorption coefficient value is less than 1 cm−1 in the range up to 750 GHz). The manufactured structures were examined in the experimental setup. All three MISO structures demonstrated proper functionality by redirecting and focusing radiation from two spatially separated radiation sources into the single focal spot located on the main optical axis. However, the structure designed with the iterative algorithm significantly surpassed the performance of the other structures. This structure redirected over two times higher intensity in the desired manner and exhibited approximately 68.12% higher relative efficiency compared to the others. The structure designed with an iterative method is recommended for further investigation and future application in 6G telecommunication systems.
{"title":"Advanced diffractive optical elements implementing multiple-input spatial multiplexing of terahertz radiation","authors":"","doi":"10.1016/j.optlaseng.2024.108606","DOIUrl":"10.1016/j.optlaseng.2024.108606","url":null,"abstract":"<div><div>In recent years, there has been growing interest in the utilization of terahertz (THz) technologies in telecommunications applications. In such systems, radiation multiplexing is required. In one of the solutions, multiplexing can be achieved through the application of appropriate passive optical components. In this study, three different designs of passive diffractive optical elements (DOEs) that meet the functionality of spatial multiplexing of THz radiation are presented. The functionality was achieved by combining two spatially separated optical channels into a single optical path with an addition of the focusing effect, creating multiple-input single-output (MISO) system performance. Two structures were designed as various combinations of off-axis segmentation of kinoform focusing lenses with particular shifts. However, the distribution of the third structure was created with the interactive algorithm. The performance of all structures was verified with numerical simulations using propagation based on the modified convolution method, giving promising results. In this study, the novel, specially dedicated method of 3D modeling was applied. MISO structures were manufactured using fused deposition modeling (FDM) 3D printing technology from styrene-butadiene copolymer (SBC) material, which is remarkably transparent for the THz radiation range (its absorption coefficient value is less than 1 cm<sup>−1</sup> in the range up to 750 GHz). The manufactured structures were examined in the experimental setup. All three MISO structures demonstrated proper functionality by redirecting and focusing radiation from two spatially separated radiation sources into the single focal spot located on the main optical axis. However, the structure designed with the iterative algorithm significantly surpassed the performance of the other structures. This structure redirected over two times higher intensity in the desired manner and exhibited approximately 68.12% higher relative efficiency compared to the others. The structure designed with an iterative method is recommended for further investigation and future application in 6G telecommunication systems.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0143816624005840/pdfft?md5=b3d1ea29a4af3671b650a1689fe516c5&pid=1-s2.0-S0143816624005840-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-23DOI: 10.1016/j.optlaseng.2024.108599
Snapshot temporal compressive imaging offers a potent method for capturing high-dimensional spatiotemporal information from a superimposed 2D image of a dynamic scene. However, despite its notable bandwidth-saving capability, simultaneous acquisition of spatiotemporal intensity and phase information remains challenging due to the phase insensitivity of detectors. To address this issue, a novel temporal compressive complex amplitude imaging (TCCAI) method based on double random phase encoding is proposed here. Within TCCAI, the target scene undergoes spatial modulation by a static phase mask in the spatial domain, followed by spatial encoding by an ultrahigh-speed-switchable phase mask in the spatial frequency domain after a Fourier transform. Adjacently, the scene is inversely Fourier transformed and integrally exposed onto a planar detector. Ultimately, the complex amplitude information, sensitive to both intensity and phase, can be faithfully reconstructed over time using a plug-and-play-based deep image prior algorithm. The feasibility, robustness, and superiority of TCCAI over intensity encoding-based methods are demonstrated through simulation. This approach is expected to pave the way for real-time multidimensional temporal imaging.
{"title":"Temporal compressive complex amplitude imaging based on double random phase encoding","authors":"","doi":"10.1016/j.optlaseng.2024.108599","DOIUrl":"10.1016/j.optlaseng.2024.108599","url":null,"abstract":"<div><div>Snapshot temporal compressive imaging offers a potent method for capturing high-dimensional spatiotemporal information from a superimposed 2D image of a dynamic scene. However, despite its notable bandwidth-saving capability, simultaneous acquisition of spatiotemporal intensity and phase information remains challenging due to the phase insensitivity of detectors. To address this issue, a novel temporal compressive complex amplitude imaging (TC<img>CAI) method based on double random phase encoding is proposed here. Within TC<img>CAI, the target scene undergoes spatial modulation by a static phase mask in the spatial domain, followed by spatial encoding by an ultrahigh-speed-switchable phase mask in the spatial frequency domain after a Fourier transform. Adjacently, the scene is inversely Fourier transformed and integrally exposed onto a planar detector. Ultimately, the complex amplitude information, sensitive to both intensity and phase, can be faithfully reconstructed over time using a plug-and-play-based deep image prior algorithm. The feasibility, robustness, and superiority of TC<img>CAI over intensity encoding-based methods are demonstrated through simulation. This approach is expected to pave the way for real-time multidimensional temporal imaging.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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