Polarization Imaging Research Articles

Infrared Imaging System with a Local Polarization Channel for Target Detection

Infrared imaging can detect the targets from their backgrounds during the day and night. As a supplementary tool, polarization imaging can visually characterize the polarized information of targets in complicated environments. In this study, an infrared imaging system with a local polarization channel is developed and simulated. The system can acquire local infrared and polarization information of the target without compromising the monitoring of the entire field of view. This system is composed of two infrared imaging channels with a common image plane: a peripheral channel for the entire field of view and a local imaging channel for the target of interest to achieve local magnification and polarization imaging. Herein, an imaging simulation of the infrared imaging system with a local polarization channel is performed, and the results show that the system performs well.

Metasurfaces‐Enabled Advanced Multidimensional Imaging: Principle and Applications

AbstractThe efficient acquisition of multidimensional information—spatial, polarization, frequency, and phase of optical fields, is a key research focus. Metasurfaces, which are emerging as planar arrays of artificial nanostructures, offer significant advantages in advanced imaging due to their exceptional ability to manipulate electromagnetic waves through subwavelength optical resonators. Meanwhile, the rapidly developing computational imaging algorithms have also greatly enhanced the performance of metasurfaces in multi‐dimensional imaging. In this review, we focus on the research progress in metasurface‐empowered multidimensional imaging, including advanced spatial imaging, compact polarization imaging, high‐resolution spectral imaging, single‐shot phase imaging, and edge imaging. Their basic principles and imaging results will also be presented. Furthermore, a summary of several current challenges and anticipation in various future directions within this field will also be provided.

Image enhancement method for paint defects based on polarization fusion technique

The highly reflective nature of paint surfaces poses a challenge for defect detection. In this paper, a polarization fusion based image enhancement algorithm for paint defects is proposed to improve the image quality and complement the masked defect details. Firstly, the linearly polarized photometric (DOLP) image is initially fused with the angle of polarization (AOP) image. The light intensity images and polarization feature images were enhanced using a single scale Retinex algorithm and these images were decomposed and reconstructed using wavelet transform to integrate the low and high frequency subbands based on saliency maps and regional energy features. Experiments were performed on defects at different locations and compared with other classical methods. The results show that the proposed fusion algorithm improves the contrast while providing more complete defect information, clearer texture details and significant advantages over other algorithms.

Color polarization imaging demosaicing based on stokes vector information complementation and fusion

Color polarization imaging demosaicing based on stokes vector information complementation and fusion

Effect of the estimation result of the degree of polarization of target light on clear imaging.

Previous underwater imaging methods have not developed a clear idea of estimating the degree of polarization of target light (Pobj). To address this issue, this Letter answers the question of how the estimation result of Pobj affects clear imaging. First, the theoretical derivation states that Pobj is simply a scale modulation factor of the imaging result. Second, experiments are conducted for validation, and results conform well to the derivation. Hence, the effect of the estimated Pobj on clear imaging is obtained. This parameter only influences brightness rather than contrast but may cause noise amplification as well as the unfavorable result of negative pixels. Therefore, no precise estimation is needed; pick the value near the ends of the definition domain directly and take the absolute value. Based on these, a new imaging formula is proposed, enabling the processing time to fulfill the actual dynamic imaging requirements. As far as we are concerned, the attained prior knowledge and formula could provide strong assistance for underwater polarization imaging.

Image Dehazing Enhancement Strategy Based on Polarization Detection of Space Targets

In view of the fact that the technology of polarization detection performs better at identifying targets through clouds and fog, the recognition ability of the space target detection system under haze conditions will be improved by applying the technology. However, due to the low ambient brightness and limited target radiation information during space target detection, the polarization information of space target is seriously lost, and the advantages of polarization detection technology in identifying targets through clouds and fog cannot be effectively exerted under the condition of haze detection. In order to solve the above problem, a dehazing enhancement strategy specifically applied to polarization images of space targets is proposed. Firstly, a hybrid multi-channel interpolation method based on regional correlation analysis is proposed to improve the calculation accuracy of polarization information during preprocessing. Secondly, an image processing method based on full polarization information inversion is proposed to obtain the degree of polarization of the image after inversion and the intensity of the image after dehazing. Finally, the image fusion method based on discrete cosine transform is used to obtain the dehazing polarization fusion enhancement image. The effectiveness of the proposed image processing strategy is verified by carrying out simulated and real space target detection experiments. Compared with other methods, by using the proposed image processing strategy, the quality of the polarization images of space targets obtained under the haze condition is significantly improved. Our research results have important practical implications for promoting the wide application of polarization detection technology in the field of space target detection.

Design of high efficiency and wideband dual-functional metasurface for polarization conversion and asymmetric transmission

A wideband and high-efficiency bi-functional metasurface for polarization conversion and asymmetric transmission (AT) based on the gratings/ polarization converter/gratings structure is proposed. The proposed metasurface structure consists of a two double-split ring structure array sandwiched by two orthogonal metallic sub-wavelength gratings. Using two orthogonal metallicsub-wavelength gratings, the proposed metasurface reveals excellent AT effect and nearly perfect polarization conversion performance for linearly polarized waves. The proposed metasurface achieves a polarization conversion ratio (PCR) of above 0.99 from 3.7 GHz to 20.2 GHz with a relative bandwidth (RBW) of 138% and an AT parameter of over 0.9 from 5.8 GHz to 17 GHz withan RBW of 99.5%. Moreover, the proposed metamaterial maintains high PCR and AT performance for a wide range of incident angles. Due to its excellent features, such as the wideband and high efficiency of both PCR and AT performances, the proposed bi-functional metasurface can be useful for promising applications such as polarization imaging. radar, radiometer, and transmission.array antennas.

Polarization-Enhanced Underwater Laser Range-Gated Imaging for Subaquatic Applications.

Laser range-gated underwater imaging technology, by removing most of the backscattering noise, can effectively increase image contrast and extend the detection range. The optical signal captured by a range-gated imaging system primarily comprises reflected light from the object and backscattered light from the surrounding water. Consequently, surfaces with low reflectivity or highly turbid water environments substantially constrain the applicability of the range-gated imaging system. To enhance the detection capability of underwater laser range-gated imaging, this paper proposes the incorporation of underwater polarized light imaging technology as an enhancement method. Based on polarization differences, backscattered light and reflected light from an object can be distinguished. Experimental results indicate that, compared to images obtained using a conventional range-gated laser imaging system, those captured with a polarization-enhanced system exhibit an increase of up to 47% for the corresponding Enhancement Measure Evaluation (EME) index. The proposed approach, which integrates polarization imaging with range-gated laser imaging, has the potential to broaden the applicability of underwater laser imaging scenarios, such as deep-sea exploration and military applications.

Reverse Design of Pixel-Type Micro-Polarizer Arrays to Improve Polarization Image Contrast.

Micro-polarizer array (MPA) is the core optical component of the Division of Focal-Plane (DoFP) imaging system, and its design is very important to the system's performance. Traditional design methods rely on theoretical analysis and simulation, which is complicated and requires designers to have profound theoretical foundations. In order to simplify the design process and improve efficiency, this paper proposes a 2 × 2 MPA reverse-design strategy based on particle swarm optimization (PSO). This strategy uses intelligent algorithms to automatically explore the design space in order to discover MPA structures with optimal optical properties. In addition, the all-pass filter is introduced to the MPA superpixel unit in the design, which effectively reduces the crosstalk and frequency aliasing between pixels. In this study, two MPA models were designed: a traditional MPA and an MPA with an all-pass filter. The Degree of Linear Polarization (DOLP) image contrast is used as the evaluation standard and compared with the traditional MPA; the results show that the contrast of the newly designed traditional MPA image is increased by 21%, and the MPA image with the all-pass filter is significantly increased by 82%. Therefore, the reverse-design method proposed in this paper not only simplifies the design process but also can design an MPA with enhanced optical performance, which has obvious advantages over the traditional method.

Supercooled Water Cloud Detection From Polarized Multi‐Angle Imager Data Using 1.37 μm Water Vapor Polarized Channel

AbstractDetecting supercooled water clouds (SWCs) is essential for enhancing artificial rainfall, preventing aircraft ice accretion, and developing a better understanding of radiative energy balance. The 1.37 μm channel, known as strong water vapor absorbing, was made polarized in the polarized multi‐angle imager (PMAI) onboard FengYun‐3G satellite. The infight data shown that the new 1.37 μm polarized channel could be used to detect SWCs. The cloudbow is observed around the 140° scattering angle in the 1.37 μm polarization image, with a maximum polarization reflectance of approximately 0.04–0.06. The indicated water clouds with spherical particles in the high‐level altitude could be SWCs. Then, the SWCs detected by 1.37 μm polarized channel is verified using polarized reflectance of other channels, the reflectance difference of channels, and thermal infrared bright temperature. The presence of cloudbow in 1.03 and 1.64 μm channels indicate liquid water cloud. The reflectance difference between 1.03 and 1.64 μm of SWCs agree with characteristic of water cloud. The thermal infrared channels from the imager on the same platform indicate cold cloud with the brightness temperature far below 273.16 K. Therefore, the only use of 1.37 μm polarized channel could perform the identification of SWCs. PMAI provides a powerful tool for monitoring supercooled water clouds.

High performance self-driven broadband photodetector for polarized imaging based on novel ZrS3/ReSe2 van der Waals heterojunction

The distinctive characteristics of anisotropic two-dimensional (2D) materials, including in-plane anisotropy of optical absorption and carrier mobility, render them exceptionally suitable for application in the field of polarization detection and as a novel platform for the polarization imaging. Meanwhile, the consolidation of diverse functionalities within a single photodetector is highly anticipated to meet the demands of some special scenarios. Herein, a novel ZrS3/ReSe2 van der Waals (vdWs) heterostructure device was successfully constructed to realize polarization-sensitive, self-powered, and broadband photodetection and imaging. Owing to the built-in electric field of the type-II band alignment within the heterojunction, the device achieves a self-powered photoresponse ranging from 300 to 980 nm, an ultralow dark currentt ∼1 pA, and a commendable rise/decay time of 0.35/0.28 ms. Additionally, it has been demonstrated that the self-driven photodetector possesses a polarization-sensitivity with a notable anisotropic ratio about 2.02 (1.98) under 490 nm (980 nm) light illumination with zero bias, coupled with an excellent repeatability and stability. Furthermore, we also demonstrate the polarization imaging capabilities of the device in visible and near-infrared spectrum, realizing a contrast-enhanced degree of linear polarization imaging. This work paves a new platform to develop heterojunction photodetectors for high performance polarization-sensitive photodetection and next-generation polarized imaging.

Polarization-selective dual-band infrared metamaterial perfect absorber

Abstract Metamaterial absorbers have significant effects and great potential for applications in a variety of important sciences and technologies, including infrared imaging, thermal emitters, electromagnetic shielding, and photodetectors. However, conventional absorbers with a single function are difficult to meet the growing demand of devices, especially for the situations where the absorption and polarization are simultaneously required in infrared detection. If the polarization absorption function is realized by integrating absorption and polarization elements, it will lead to a large overall system size and slow response time. To solve this problem, we propose a dual-band polarization-selective metamaterial perfect absorber, whose maximum absorptions at resonant wavelengths of λ1=2.824μm and λ2=7.622μm are 99.99% and 99.88%, respectively. The absorber exhibits strong polarization sensitivity, absorbing TM-polarized incident light and reflecting TE-polarized incident light at the two resonant wavelengths. The extinction ratios of the absorber at the two referred resonant wavelengths are 90.9 and 142.7, respectively. The proposed absorber would be beneficial for infrared polarization detection and imaging.

Lensless Mueller holographic microscopy with robust noise reduction for multiplane polarization imaging

Lensless holographic microscopy has emerged as a powerful and cost-effective tool for computational imaging, offering high resolution over a large field of view, beneficial for various biological applications. However, conventional approaches can struggle with contrast and accurate visualization of diverse components over the samples, which can directly affect the diagnostic precision of the techniques. Mueller imaging, while offering detailed, stain-free observations of polarized light responses in samples, often has a limited field of view and single plane information. This is due to the use of high NA microscope objectives and generally complex hardware setups, thus narrowing its practical effectiveness. This work introduces a Lensless Mueller Holographic Microscopy (LMHM) system that overcomes these limitations, enabling large field of view, volumetric multi-layer imaging, and Mueller matrix computation using in-line lens-free holography setup. The proposed system provides precision visualization of polarization information in samples, offering high-quality features due to the incorporation of a numerical multi-height Gerchberg-Saxton reconstruction algorithm with additional complex field filtering and a physical rotating diffuser. The proposed LMHM framework is validated with a calibrated USAF 1951 birefringent test target. A multiplane sample containing cloth fiber is utilized to study the LMHM capabilities of imaging volumetric samples. Finally, the LMHM is used to analyze two mice’s brain slices, effectively showcasing this organ’s anatomy. Among other structures in the brain, the proposed method easily allows the visualization of, e.g., the corpus callosum. These results constitute a proof-of-concept evaluation for bioimaging applications.

Three-dimensional polarimetric ptychography

A three-dimensional polarimetric ptychography (3D-PP) technique is proposed to reconstruct the residual stress distribution in optical elements in three dimensions by combining polarization imaging and a 3D ptychographic iterative engine (3D-PIE). 3D-PP mainly uses two orthogonal linear polarizers placed along the light direction to capture the photoelastic information within an optical element. Based on phase shift theory, a three-step phase shift method is proposed to record three dark field images, allowing for calculating the isometric line of residual stress within the optical element. This method enables the layer-by-layer measurement of residual stress within thick samples and assesses the distribution of residual stress along the detection axis, enhancing the precision of stress measurements.

Research of the underwater polarization imaging process based on the Oren–Nayar polarization bidirectional reflection distribution function

Research of the underwater polarization imaging process based on the Oren–Nayar polarization bidirectional reflection distribution function

Achromatic Full Stokes Polarimetry Metasurface for Full-Color Polarization Imaging in the Visible Range.

Metasurfaces provide an ultrathin platform for compact, real-time polarimetry. However, their applications in polychromatic scenes are restricted by narrow operating bandwidths that causes spectral information loss. Here, we demonstrate full-color polarization imaging using an achromatic polarimeter consisting of four polarization-dependent metalenses. Leveraging an intelligent design scheme, we achieve effective arbitrary phase compensation and multiobjective matching with a limited database. This system provides broadband achromaticity across wavelengths from 450 to 650 nm, resulting in a relative bandwidth of approximately 0.364 for full Stokes imaging. Experimental reconstruction errors for wavelengths of 450, 550, and 650 nm are 7.5%, 5.9%, and 3.8%, respectively. Performance is evaluated based on both achromatic bandwidth and crosstalk, with our design achieving three times the performance of the current state-of-the-art. The full-color, full-polarization imaging capability of the device is further validated with a customized object. The proposed scheme advances polarization imaging for practical applications.

Underwater image restoration via spatially adaptive polarization imaging and color correction

Polarization imaging is extensively employed in underwater image restoration owing to its effectiveness in eliminating backscattered light. However, the existing polarization-based imaging methods rely on the strong assumption that the degrees of polarization (DoPs) of the target and backscattered light remain constant. Additionally, these methods ignore wavelength-specific absorption phenomena. To address these challenges, we propose an underwater image restoration method via spatially adaptive polarization imaging and color correction. First, based on optimal polarization difference images, we propose a method for calculating the spatial DoP of the target. In this method, the polarization characteristics of the target and background are fully exploited, and a scoring function is designed to achieve an optimal differential image. Second, we propose an adaptive local optimization method to estimate the spatial DoP of backscattering, which involves dividing the image into multiple local regions, and then employing improved particle swarm optimization (IPSO) algorithms to obtain the optimal value of DoP for each region. Finally, we introduce an adaptive compensation method based on the channel with minimal color absorption to correct color shifts during underwater polarization imaging. Extensive experiments demonstrate that our method exhibits superior generalization capability and outstanding restoration performance compared to existing methods.

Near-field terahertz electro-optical imaging based on a polarization image sensor

Abstract This paper presents a hyperspectral microscopy system that offers two-dimensional (2D) measurement of the spectral phase and amplitude information of terahertz (THz) radiation without the need for raster scanning. To achieve this, a new THz imaging method is introduced, wherein the distribution of the THz electric field is spatially measured using the electro-optic effect with a commercial polarization image sensor. This method enables the direct measurement of polarization components, eliminating the need for the polarization optics usually required in conventional electro-optical imaging. The performance of this imaging method is compared with a conventional 2D imaging system based on a standard visible camera. Finally, the sub-wavelength resolution capabilities of this new sensor are demonstrated by imaging a sample in the near field.

Angle-resolved polarization Raman spectroscopy of β-Ga2O3 and their application in sensitive solar-blind photodetection

Polarization-sensitive photodetection has promising prospects for civilian and military applications based on anisotropic semiconductors. However, it is greatly limited due to the lack of valid materials as well as the terrible linear dichroism ratio. In this Letter, a metal–oxide–semiconductor β-Ga2O3 with strong anisotropic property is proposed for highly efficient polarizing detection, which can potentially overcome these limitations. Angle-resolved polarization Raman spectroscopy was performed to confirm excellent anisotropic phonon vibration. Unique narrow solar-blind polarization-sensitive photo-absorption (240–270 nm) can be observed, which can be attributed to the natural anisotropy, referring in particular to the polarization-resolved absorption in the surround of the bandgap of β-Ga2O3. Benefiting from the structural anisotropy, the polarization-sensitive photodetector exhibits an excellent linear dichroic ratio of ∼1.8. Moreover, obvious color change is observed under different polarized angles, providing great potential in polarization imaging. With these advantages, we anticipated that this research will pave avenues for the fabrication of polarization-sensitive solar-blind UV photodetectors.

Exploration of Volatileomics and Optical Properties of Fusarium graminearum-Contaminated Maize: An Application Basis for Low-Cost and Non-Destructive Detection.

Fusarium graminearum (F. graminearum) in maize poses a threat to grain security. Current non-destructive detection methods face limited practical applications in grain quality detection. This study aims to understand the optical properties and volatileomics of F. graminearum-contaminated maize. Specifically, the transmission and reflection spectra (wavelength range of 200-1100 nm) were used to explore the optical properties of F. graminearum-contaminated maize. Volatile organic compounds (VOCs) of F. graminearum-contaminated maize were determined by headspace solid phase micro-extraction with gas chromatography-tandem mass spectrometry. The VOCs of normal maize were mainly alcohols and ketones, while the VOCs of severely contaminated maize became organic acids and alcohols. The ultraviolet excitation spectrum of maize showed a peak redshift as fungi grew, and the intensity decreased in the 400-600 nm band. Peak redshift and intensity changes were observed in the visible/near-infrared reflectance and transmission spectra of F. graminearum-contaminated maize. Remarkably, optical imaging platforms based on optical properties were developed to ensure high-throughput detection for single-kernel maize. The developed imaging platform could achieve more than 80% classification accuracy, whereas asymmetric polarization imaging achieved more than 93% prediction accuracy. Overall, these results can provide theoretical support for the cost-effective preparation of low-cost gas sensors and high-prediction sorting equipment for maize quality detection.