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3 pages, 158 KiB

Open AccessEditorial

Advanced Polarimetry and Polarimetric Imaging

by Xiaobo Li, Fei Liu and Jian Liang

Photonics 2024, 11(4), 317; https://doi.org/10.3390/photonics11040317 - 29 Mar 2024

Viewed by 1641

Abstract

Polarization, a core attribute of light waves, offers insights into light’s physical properties and its interactions with materials [...] Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

Research

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14 pages, 2315 KiB

Open AccessArticle

Numerical Study of the Spectrum of TE-Polarized Electromagnetic Waves of a Goubau Line Coated with Graphene

by Eugen Smolkin and Yury Smirnov

Photonics 2023, 10(12), 1297; https://doi.org/10.3390/photonics10121297 - 24 Nov 2023

Cited by 1 | Viewed by 987

Abstract

The problem of TE-polarized waves in a Goubau line (a perfectly conducting cylinder covered by a concentric layer) coated with graphene is studied. The classification of the waves existing in a Goubau line is carried out. The physical problem is reduced to solving [...] Read more.

The problem of TE-polarized waves in a Goubau line (a perfectly conducting cylinder covered by a concentric layer) coated with graphene is studied. The classification of the waves existing in a Goubau line is carried out. The physical problem is reduced to solving a transmission eigenvalue problem for an ordinary differential equation. The conjugation conditions contain the conductivity of graphene. In this work, we take into account the nonlinearity of graphene. Spectral parameters of the problem are the propagation constants of the waveguide. The article proposes a numerical method for calculating the propagation constants of such waves. A number of numerical experiments were carried out with a Goubau line filled with a dielectric, inhomogeneous dielectric, dielectric with losses, and metamaterial. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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15 pages, 5092 KiB

Open AccessArticle

Tunnel Lining Crack Detection Method Based on Polarization 3D Imaging

by Yue Zhang, Xuemin Zhang, Yun Su, Xuan Li, Shiwei Ma, Su Zhang, Weihe Ren and Kang Li

Photonics 2023, 10(10), 1085; https://doi.org/10.3390/photonics10101085 - 27 Sep 2023

Cited by 1 | Viewed by 1309

Abstract

Non-contact and non-destructive polarization 3D imaging uses a passive, single-frame array image to calculate 3D information, making it possible to obtain high-precision 3D information about tunnel cracks, and offering outstanding technical advantages. Based on the introduction of the principle of crack detection with [...] Read more.

Non-contact and non-destructive polarization 3D imaging uses a passive, single-frame array image to calculate 3D information, making it possible to obtain high-precision 3D information about tunnel cracks, and offering outstanding technical advantages. Based on the introduction of the principle of crack detection with polarization 3D imaging, a tunnel lining crack detection plan was developed and a detection equipment was designed. The method and process of polarization 3D imaging for lining crack detection are described in detail. A model of the impact of the tunnel environment on 3D detection and a method for obtaining absolute information have been established to obtain high-precision 3D information about cracks. In a real tunnel environment, tests were conducted to detect wide cracks, narrow cracks, and artificial cracks. The crack detection accuracy with respect to the crack width was 0.2–0.3 mm, and with respect to crack length was 0.2–0.3 mm. At the same time, crack depth information could be obtained. The present research results can provide technical support for the application of polarization 3D imaging in tunnel crack detection. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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12 pages, 5149 KiB

Open AccessArticle

Development and Calibration of a Vertical High-Speed Mueller Matrix Ellipsometer

by Jiamin Liu, Song Zhang, Bowen Deng, Lei Li, Honggang Gu, Jinlong Zhu, Hao Jiang and Shiyuan Liu

Photonics 2023, 10(9), 1064; https://doi.org/10.3390/photonics10091064 - 21 Sep 2023

Viewed by 1693

Abstract

In order to meet the requirements of dynamic monitoring from a bird’s eye view for typical rapidly changing processes such as mechanical rotation and photoresist exposure reaction, we propose a vertical high-speed Mueller matrix ellipsometer that consists of a polarization state generator (PSG) [...] Read more.

In order to meet the requirements of dynamic monitoring from a bird’s eye view for typical rapidly changing processes such as mechanical rotation and photoresist exposure reaction, we propose a vertical high-speed Mueller matrix ellipsometer that consists of a polarization state generator (PSG) based on the time-domain polarization modulation and a polarization state analyzer (PSA) based on division-of-amplitude polarization demodulation. The PSG is realized using two cascaded photoelastic modulators, while the PSA is realized using a six-channel Stokes polarimeter. On this basis, the polarization effect introduced by switching the optical-path layout of the instrument from the horizontal transmission to the vertical transmission is fully considered, which is caused by changing the incidence plane. An in situ calibration method based on the correct definition of the polarization modulation and demodulation reference plane has been proposed, enabling the precise calibration of the instrument by combining it with a time-domain light intensity fitting algorithm. The measurement experiments of SiO₂ films and an air medium prove the accuracy and feasibility of the proposed calibration method. After the precise calibration, the instrument can exhibit excellent measurement performance in the range of incident angles from 45° to 90°, in which the measurement time resolution is maintained at the order of 10 μs, the measurement accuracy of Mueller matrix elements is better than 0.007, and the measurement precision is better than 0.005. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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16 pages, 6072 KiB

Open AccessArticle

Calibration of Waveplate Retardance Fluctuation Due to Field-of-View Effect in Mueller Matrix Ellipsometer

by Zhou Jiang, Song Zhang, Hao Jiang and Shiyuan Liu

Photonics 2023, 10(9), 1038; https://doi.org/10.3390/photonics10091038 - 12 Sep 2023

Cited by 7 | Viewed by 1458

Abstract

Leveraging their unique phase modulation characteristics, birefringent waveplates have been widely used in various optical systems. With the development of material science and manufacturing techniques, the polarization properties of waveplates have become increasingly complex and diverse. Among these properties, the field-of-view effect of [...] Read more.

Leveraging their unique phase modulation characteristics, birefringent waveplates have been widely used in various optical systems. With the development of material science and manufacturing techniques, the polarization properties of waveplates have become increasingly complex and diverse. Among these properties, the field-of-view effect of the waveplate caused due to manufacturing defects or improper installation procedures is extremely difficult to calibrate and seriously affects the precision and accuracy of the relevant optical systems. In this paper, a calibration method that can compensate for the field-of-view effect of waveplates installed in the instrument is proposed. Moreover, to approve the fidelity of the proposed calibration method, a series of film thickness measurement experiments are carried out. The results show that under different installation conditions of the waveplates, the precision and accuracy of the film thickness measured with the proposed method significantly improved. This method can be expected to reduce the assembly difficulty of such optical systems, while also improving their accuracy and stability. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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12 pages, 2002 KiB

Open AccessCommunication

Synthetic Mueller Imaging Polarimetry

by José J. Gil and Ignacio San José

Photonics 2023, 10(9), 969; https://doi.org/10.3390/photonics10090969 - 24 Aug 2023

Viewed by 923

Abstract

The transformation of the state of polarization of a light beam via its linear interaction with a material medium can be modeled through the Stokes–Mueller formalism. The Mueller matrix associated with a given interaction depends on many aspects of the measurement configuration. In [...] Read more.

The transformation of the state of polarization of a light beam via its linear interaction with a material medium can be modeled through the Stokes–Mueller formalism. The Mueller matrix associated with a given interaction depends on many aspects of the measurement configuration. In particular, different Mueller matrices can be measured for a fixed material sample depending on the spectral profile of the light probe. For a given light probe and a given sample with inhomogeneous spatial behavior, the polarimetric descriptors of the point-to-point Mueller matrices can be mapped, leading to respective polarimetric images. The procedure can be repeated sequentially using light probes with different central frequencies. In addition, the point-to-point Mueller matrices, consecutively measured, can be combined synthetically through convex sums leading to respective new Mueller matrices, in general with increased polarimetric randomness, thus exhibiting specific values for the associated polarimetric descriptors, including the indices of polarimetric purity, and generating new polarimetric images which are different from those obtained from the original Mueller matrices. In this work, the fundamentals for such synthetic generation of additional polarimetric images are described, providing a new tool that enhances the exploitation of Mueller polarimetry. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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11 pages, 1920 KiB

Open AccessArticle

Polarization-Sensitive Structural Colors Based on Anisotropic Silicon Metasurfaces

by Xiao Shang, Jiebin Niu, He Li, Longjie Li, Huakui Hu, Cheng Lu and Lina Shi

Photonics 2023, 10(4), 448; https://doi.org/10.3390/photonics10040448 - 13 Apr 2023

Cited by 4 | Viewed by 2163

Abstract

Structural colors based on all-dielectric metasurfaces hold great promise for a wide range of applications, including high-density optical storage, ultra-high-resolution 3D displays, imaging security certification, and so on. However, achieving dynamic tunable structural color with a compact and simple Si platform remains a [...] Read more.

Structural colors based on all-dielectric metasurfaces hold great promise for a wide range of applications, including high-density optical storage, ultra-high-resolution 3D displays, imaging security certification, and so on. However, achieving dynamic tunable structural color with a compact and simple Si platform remains a great challenge. Here, we propose a dynamic tunable structural coloration with polarization-sensitive metasurfaces consisting of arrays of Si elliptical nanopillars, enabling full-colored images to be displayed and switched through the control of the polarization of incident light. A distinct feature of our design is that the color phase is independent of the viewing angle, which is fundamental for real applications. Moreover, we demonstrated that dual and multiple colors can be obtained by varying the angle of either the polarizer or the analyzer. Our scheme provides a simple yet general approach for potential applications in the fields of virtual reality, ultra-high-resolution 3D displays, and high-density information storage. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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10 pages, 2704 KiB

Open AccessCommunication

Full-Color and Anti-Counterfeit Printings with All-Dielectric Chiral Metasurfaces

by Longjie Li, He Li, Huakui Hu, Xiao Shang, Huiwen Xue, Jinyu Hu, Cheng Lu, Shengjie Zhao, Jiebin Niu and Lina Shi

Photonics 2023, 10(4), 401; https://doi.org/10.3390/photonics10040401 - 3 Apr 2023

Viewed by 1960

Abstract

Structural color is anticipated to replace pigmented or chemical color due to its superior saturation, resolution, environmental friendliness, and longevity. We achieve a full-color gamut of structural colors and anti-counterfeit functions by an all-dielectric chiral metasurface consisting of half-gammadion-shaped resonators embedded in PMMA [...] Read more.

Structural color is anticipated to replace pigmented or chemical color due to its superior saturation, resolution, environmental friendliness, and longevity. We achieve a full-color gamut of structural colors and anti-counterfeit functions by an all-dielectric chiral metasurface consisting of half-gammadion-shaped resonators embedded in PMMA and a top TiO₂ layer on quartz coated with an ITO layer. The prominent resonance peaks of this embedded chiral metasurface under the cross-polarization condition, which are provided by the polarization conversion features of the chiral structure, lead to extremely saturated structural colors. The color phase mainly depends on the structure’s period, opening up a full-color range well beyond sRGB. Especially, we demonstrate a star with hidden information of the letter “A” and the Chinese word “李龙杰” by taking advantage of the difference in the color phase change under different polarization conditions to decode the information, thus realizing the anti-counterfeiting function. Our proposed embedded chiral metasurface provides dual-function structural colors and is highly promising for micro-display, nanoprinting, anti-counterfeiting, data storage, and information encryption. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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15 pages, 5078 KiB

Open AccessArticle

High-Performance Polarization Imaging Reconstruction in Scattering System under Natural Light Conditions with an Improved U-Net

by Bing Lin, Xueqiang Fan, Dekui Li and Zhongyi Guo

Photonics 2023, 10(2), 204; https://doi.org/10.3390/photonics10020204 - 13 Feb 2023

Cited by 18 | Viewed by 2074

Abstract

Imaging through scattering media faces great challenges. Object information will be seriously degraded by scattering media, and the final imaging quality will be poor. In order to improve imaging quality, we propose using the transmitting characteristics of an object’s polarization information, to achieve [...] Read more.

Imaging through scattering media faces great challenges. Object information will be seriously degraded by scattering media, and the final imaging quality will be poor. In order to improve imaging quality, we propose using the transmitting characteristics of an object’s polarization information, to achieve imaging through scattering media under natural light using an improved U-net. In this paper, we choose ground glass as the scattering medium and capture the polarization images of targets through the scattering medium by a polarization camera. Experimental results show that the proposed model can reconstruct target information from highly damaged images, and for the same material object, the trained network model has a superior generalization without considering its structural shapes. Meanwhile, we have also investigated the effect of the distance between the target and the ground glass on the reconstructing performance, in which, and although the mismatch distance between the training set and the testing sample expands to 1 cm, the modified U-net can also efficaciously reconstruct the targets. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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19 pages, 10012 KiB

Open AccessArticle

Active Polarization Imaging for Cross-Linear Image Histogram Equalization and Noise Suppression in Highly Turbid Water

by Huajun Zhang, Jianrui Gong, Mingyuan Ren, Ning Zhou, Hantao Wang, Qingguo Meng and Yu Zhang

Photonics 2023, 10(2), 145; https://doi.org/10.3390/photonics10020145 - 30 Jan 2023

Cited by 7 | Viewed by 1854

Abstract

The absorption and scattering of impurity particles in turbid water cause the target signal light to be attenuated and to produce backscattered light, resulting in the reduced quality of underwater polarimetric imaging. As water turbidity increases, the effect of backscattered light becomes greater, [...] Read more.

The absorption and scattering of impurity particles in turbid water cause the target signal light to be attenuated and to produce backscattered light, resulting in the reduced quality of underwater polarimetric imaging. As water turbidity increases, the effect of backscattered light becomes greater, making polarization imaging in highly turbid water a challenge. Theory and experiment show that the increase in the intensity of backscattered light leads to high noise gain in the underwater active polarization imaging model. In order to enhance image contrast and suppress noise gain in highly turbid water, we propose an underwater imaging enhancement method that appropriately combines the non-physical and physical models. The method uses contrast limited adaptive histogram equalization (CLAHE) for a certain number of cross-linear images (I_min) before calculating their polarization enhancement images, and it constructs joint filtering (multi-frame averaging and bilateral filtering) to suppress the high noise gain introduced by the imaging model and CLAHE. The experimental results in highly turbid water validate the rationality and feasibility of the proposed method, and the comparative processing results (52.7~98.6 NTU) outperform those of the conventional non-physical and physical model methods. The method maintains the complexity of the system and facilitates the application of conventional polarimetric imaging in harsher underwater environments. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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12 pages, 4756 KiB

Open AccessArticle

Accurate Passive 3D Polarization Face Reconstruction under Complex Conditions Assisted with Deep Learning

by Pingli Han, Xuan Li, Fei Liu, Yudong Cai, Kui Yang, Mingyu Yan, Shaojie Sun, Yanyan Liu and Xiaopeng Shao

Photonics 2022, 9(12), 924; https://doi.org/10.3390/photonics9120924 - 30 Nov 2022

Cited by 11 | Viewed by 2461

Abstract

Accurate passive 3D face reconstruction is of great importance with various potential applications. Three-dimensional polarization face reconstruction is a promising approach, but one bothered by serious deformations caused by an ambiguous surface normal. In this study, we propose a learning-based method for passive [...] Read more.

Accurate passive 3D face reconstruction is of great importance with various potential applications. Three-dimensional polarization face reconstruction is a promising approach, but one bothered by serious deformations caused by an ambiguous surface normal. In this study, we propose a learning-based method for passive 3D polarization face reconstruction. It first calculates the surface normal of each microfacet at a pixel level based on the polarization of diffusely reflected light on the face, where no auxiliary equipment, including artificial illumination, is required. Then, the CNN-based 3DMM (convolutional neural network; 3D morphable model) generates a rough depth map of the face with the directly captured polarization image. The map works as an extra constraint to correct the ambiguous surface normal obtained from polarization. An accurate surface normal finally allows for an accurate 3D face reconstruction. Experiments in both indoor and outdoor conditions demonstrate that accurate 3D faces can be well-reconstructed. Moreover, with no auxiliary equipment required, the method ensures a total passive 3D face reconstruction. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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9 pages, 9725 KiB

Open AccessArticle

An Algorithm to Extract the Boundary and Center of EUV Solar Image Based on Sobel Operator and FLICM

by Shuai Li, Jianhua Zhang, Bei Liu, Chengzhi Jiang, Lanxu Ren, Jingjing Xue and Yansong Song

Photonics 2022, 9(12), 889; https://doi.org/10.3390/photonics9120889 - 22 Nov 2022

Cited by 2 | Viewed by 1355

Abstract

An algorithm to extract the disk boundary and center of EUV solar image using the Sobel operator, Fuzzy Local Information C-Means Clustering algorithm (FLICM), and the least square circle fitting method is proposed in this paper. The Sobel operator can determine the solar [...] Read more.

An algorithm to extract the disk boundary and center of EUV solar image using the Sobel operator, Fuzzy Local Information C-Means Clustering algorithm (FLICM), and the least square circle fitting method is proposed in this paper. The Sobel operator can determine the solar disk boundary preliminarily, and then the image is processed further using the FLICM algorithm. After the background is removed based on the clustered image and the boundary points can be highlighted, these points are fitted using the least square circle fitting method as the final boundary circle. The solar data used in this paper was from the observation of the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) instrument. The 2523 19.3 nm solar images covering solar minimum, moderate solar activity, and more active suns were calculated using the proposed algorithm to analyze the accuracy statistically. The statistical comparison results demonstrate that the method is accurate and effective. This method can support the processing of solar EUV images and serve the operational system of a space weather forecast. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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11 pages, 10906 KiB

Open AccessCommunication

Preparation of an Integrated Polarization Navigation Sensor via a Nanoimprint Photolithography Process

by Ze Liu, Jinkui Chu, Ran Zhang, Chuanlong Guan and Yuanyi Fan

Photonics 2022, 9(11), 806; https://doi.org/10.3390/photonics9110806 - 27 Oct 2022

Cited by 2 | Viewed by 1937

Abstract

Based on the navigation strategy of insects utilizing the polarized skylight, an integrated polarization sensor for autonomous navigation is presented. The polarization sensor is fabricated using the proposed nanoimprint photolithography (NIPL) process by integrating a nanograting polarizer and an image chip. The NIPL [...] Read more.

Based on the navigation strategy of insects utilizing the polarized skylight, an integrated polarization sensor for autonomous navigation is presented. The polarization sensor is fabricated using the proposed nanoimprint photolithography (NIPL) process by integrating a nanograting polarizer and an image chip. The NIPL process uses a UV-transparent variant template with nanoscale patterns and a microscale metal light-blocking layer. During the NIPL process, part of the resist material is pressed to fill into the nanofeatures of the variant template and is cured under UV exposure. At the same time, the other parts of the resist material create micropatterns according to the light-blocking layer. Polymer-based variant templates can be used for conformal contacts on non-flat substrates with excellent pattern transfer fidelity. The NIPL process is suitable for cross-scale micro–nano fabrication in wide applications. The measurement error of the polarization angle of the integrated polarization sensor is ±0.2°; thus, it will have a good application prospect in the polarization navigation application. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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Review

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35 pages, 12619 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Polarization Lidar: Principles and Applications

by Xudong Liu, Liping Zhang, Xiaoyu Zhai, Liye Li, Qingji Zhou, Xue Chen and Xiaobo Li

Photonics 2023, 10(10), 1118; https://doi.org/10.3390/photonics10101118 - 4 Oct 2023

Cited by 13 | Viewed by 7408

Abstract

Traditional lidar techniques mainly rely on the backscattering/echo light intensity and spectrum as information sources. In contrast, polarization lidar (P-lidar) expands the dimensions of detection by utilizing the physical property of polarization. By incorporating parameters such as polarization degree, polarization angle, and ellipticity, [...] Read more.

Traditional lidar techniques mainly rely on the backscattering/echo light intensity and spectrum as information sources. In contrast, polarization lidar (P-lidar) expands the dimensions of detection by utilizing the physical property of polarization. By incorporating parameters such as polarization degree, polarization angle, and ellipticity, P-lidar enhances the richness of physical information obtained from target objects, providing advantages for subsequent information analysis. Over the past five decades, the application fields of P-lidar have rapidly expanded, starting from its early use in atmospheric remote sensing to later applications in oceanic remote sensing. This review first provides a brief introduction to the basic principles of both polarization and P-lidar, along with typical systems. It then explores the applications of P-lidar in various remote sensing fields, including atmospheric, oceanic, and terrestrial domains. Additionally, we propose potential research directions based on current cutting-edge applications, with the aims of providing critical insights to researchers in the fields of polarization and lidar and inspiring further exciting ideas. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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26 pages, 16501 KiB

Open AccessReview

Working Mechanism and Progress of Electromagnetic Metamaterial Perfect Absorber

by Xiajun Liu, Feng Xia, Mei Wang, Jian Liang and Maojin Yun

Photonics 2023, 10(2), 205; https://doi.org/10.3390/photonics10020205 - 14 Feb 2023

Cited by 12 | Viewed by 4766

Abstract

Electromagnetic metamaterials are artificial subwavelength composites with periodic structures, which can interact strongly with the incident light to achieve effective control of the light field. Metamaterial absorbers can achieve nearly 100% perfect absorption of incident light at a specific frequency, so they are [...] Read more.

Electromagnetic metamaterials are artificial subwavelength composites with periodic structures, which can interact strongly with the incident light to achieve effective control of the light field. Metamaterial absorbers can achieve nearly 100% perfect absorption of incident light at a specific frequency, so they are widely used in sensors, optical switches, communication, and other fields. Based on the development history of metamaterials, this paper discusses the research background and significance of metamaterial perfect absorbers. Some perfect absorption mechanisms, such as impedance matching and coherent perfect absorption, are discussed. According to the functional division, the narrowband, dual frequency, multi-frequency, broadband, and tunable metamaterial perfect absorbers are briefly described. Full article

(This article belongs to the Special Issue Advanced Polarimetry and Polarimetric Imaging)

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