Infrared Polarization Imaging Research Articles

Dynamically manipulating long-wave infrared polarized thermal radiation by a vanadium dioxide metasurface.

Dynamically manipulating the spectra and polarization properties of thermal radiation is the key to counter an infrared polarization imaging system (IPIS) under the different background environments. In this Letter, we propose a phase-change metasurface thermal emitter (PCMTE) composed of vanadium dioxide (VO2) dipole antenna arrays to dynamically manipulate polarized radiation spectra in the long-wave infrared (LWIR) region of 8-14 µm. During the thermally induced and reversible insulator-to-metal transition (IMT) in VO2, by simulating the LWIR images at different polarization angles for the PCMTE and background plates, the PCMTE can realize dynamically tunable LWIR camouflage; then, their degree of linear polarization (DoLP) can be calculated, which can demonstrate that the PCMTE can also achieve dynamically tunable LWIR polarization camouflage at the specific radiation angles and backgrounds. Our proposed PCMTE provides an effective scheme for adaptive IR polarization camouflage.

Research on the Processing of Image and Spectral Information in an Infrared Polarization Snapshot Spectral Imaging System

In order to solve the problems of a low target recognition rate and poor real-time performance brought about by conventional infrared imaging spectral detection technology under complex background conditions or in the detection of targets of weak radiation or long distance, a kind of infrared polarization snapshot spectral imaging system (PSIFTIS) and a spectrum information processing method based on micro-optical devices are proposed in this paper, where the synchronous acquisition of polarization spectrum information is realized through the spatial modulation of phase with a rooftop-shaped multi-stage micro-mirror and the modulation of the polarization state of light with a micro-nanowire array. For the polarization interference image information obtained, the infrared polarization spectrum decoupling is realized by image segmentation, optical path difference matching, and image registration methods, the infrared polarization spectrum reconstruction is realized by Fourier transform spectral demodulation, and the infrared polarization image fusion is realized by decomposing and reconstructing the high- and low-frequency components of the polarization image based on the Haar wavelet transform. The maximum spectral peak wavenumber error of the four polarization channels of the polarization spectrum reconstruction is less than 2 cm−1, and the polarization angle error is within 1°. Ultimately, compared with the unprocessed polarization image unit, the peak signal-to-noise ratio is improved by 45.67%, the average gradient is improved by 8.03%, and the information entropy is improved by 56.98%.

Particle Swarm Optimization of Multilayer Multi-Sized Metamaterial Absorber for Long-Wave Infrared Polarimetric Imaging.

Infrared polarization imaging holds significant promise for enhancing target recognition in both civil and defense applications. The Division of Focal Plane (DoFP) scheme has emerged as a leading technology in the field of infrared polarization imaging due to its compact design and absence of moving parts. However, traditional DoFP solutions primarily rely on micro-polarizer arrays, necessitating precise alignment with the focal plane array and leading to challenges in alignment and the introduction of optical crosstalk. Recent research has sought to augment the performance of infrared detectors and enable polarization and spectral selection by integrating metamaterial absorbers with the pixels of the detector. Nevertheless, the results reported so far exhibit shortcomings, including low polarization absorption rates and inadequate polarization extinction ratios. Furthermore, there is a need for a comprehensive figure of merit to systematically assess the performance of polarization-selective thermal detectors. In this study, we employ the particle swarm optimization algorithm to present a multilayer, multi-sized metamaterial absorber capable of achieving a remarkable polarization-selective absorption rate of up to 87.2% across the 8-14 μm spectral range. Moreover, we attain a polarization extinction ratio of 38.51. To elucidate and predict the resonant wavelengths of the structure, we propose a modified equivalent circuit model. Our analysis employs optical impedance matching to unveil the underlying mechanisms responsible for the high absorption. We also introduce a comprehensive figure of merit to assess the efficacy of infrared polarization detection through the integration of metamaterials with microbolometers. Finally, drawing on the proposed figure of merit, we suggest future directions for improving integrated metamaterial absorber designs, with the potential to advance practical mid-infrared polarization imaging technologies.

A Super-Resolution Reconstruction Method for Infrared Polarization Images with Sparse Representation of Over-Complete Basis Sets

The spatial resolution of an infrared focal plane polarization detection system is limited by the structure of the detector, resulting in lower resolution than the actual array size. To overcome this limitation and improve imaging resolution, we propose an infrared polarization super-resolution reconstruction model based on sparse representation, optimized using Stokes vector images. This model forms the basis for our method aimed at achieving super-resolution reconstruction of infrared polarization images. In this method, we utilize the proposed model to initially reconstruct low-resolution images in blocks. Subsequently, we perform a division by weight, followed by iterative back projection to enhance details and achieve high-resolution reconstruction results. As a supplement, we establish a near-real-time short-wave infrared time-sharing polarization system for data collection. The dataset was acquired to gather prior knowledge of the over-complete basis set and to generate a series of simulated focal plane images. Simulation experimental results demonstrate the superiority of our method over several advanced methods in objective evaluation indexes, exhibiting strong noise robustness in quantitative experiments. Finally, to validate the practical application of our method, we establish a split-focal plane polarization short-wave infrared system for scene testing. Experimental results confirm the effective processing of actual captured data by our method.

Polarized Prior Guided Fusion Network for Infrared Polarization Images

Polarized Prior Guided Fusion Network for Infrared Polarization Images

Analysis of Two-Color Infrared Polarization Imaging Characteristics for Target Detection and Recognition

Infrared polarization imaging has demonstrated significant advantages in target detection and recognition in natural environments. While there have been numerous research achievements on medium-wave/long-wave infrared polarization in a single band, there is a lack of related conclusions on the characteristics of wide spectral two-color infrared polarization imaging. To address this gap, this article employs a theoretical model in infrared polarization imaging to investigate the influence of temperature, incident angle, and refractive index on polarization degree and polarization angle. These findings have been substantiated through discussions on experimental results. We conducted a comparative analysis between intensity imaging and polarization imaging within the framework of traditional single-band infrared imaging. We then delineated the benefits of dual-color infrared polarization imaging. Finally, we harnessed image registration fusion algorithms to amalgamate multiple-band images. Our findings demonstrate that this fusion technique not only enables penetration through water mist but also enhances target visibility, providing theoretical support for all-weather target detection and identification.

Shortwave Infrared InGaAs Detectors On-Chip Integrated with Subwavelength Polarization Gratings.

Shortwave infrared polarization imaging can increase the contrast of the target to the background to improve the detection system's recognition ability. The division of focal plane polarization indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice due to the advantages of compact structure, real-time imaging, and high stability. However, because of the mismatch between nanostructures and photosensitive pixels as well as the crosstalk among the different polarization directions, the currently reported extinction ratio (ER) of superpixel-polarization-integrated detectors cannot meet the needs of high-quality imaging. In this paper, a 1024 × 4 InGaAs FPA detector on-chip integrated with a linear polarization grating (LPG) was realized and tested. The detector displayed good performance throughout the 0.9-1.7 um band, and the ERs at 1064 nm, 1310 nm and 1550 nm reached up to 22:1, 29:1 and 46:1, respectively. For the crosstalk investigation, the optical simulation of the grating-integrated InGaAs pixel was carried out, and the limitation of the ER was calculated. The result showed that the scattering of incident light in the InP substrate led to the crosstalk. Moreover, the deviation of the actual grating morphology from the designed structure caused a further reduction in the ER.

Shortwave Infrared Polarization Imaging and Monolithic Integrated Polarization Amplification Systems Based on Aligned Carbon Nanotube Arrays

AbstractNext‐generation shortwave infrared (SWIR) imaging systems generally require a multidimensional information sensing capability (including intensity, wavelength, polarization, phase, etc.), a highly integrated photodetector unit, and information processing, allowing for miniaturization and low‐cost production. However, traditional polarized SWIR imaging systems with integrated polarizer arrays as supplementary filters and silicon‐based amplifying circuits are complicated and very expensive. Here, a SWIR polarization‐sensitive photodetector and a monolithic integrated polarization amplification system (MIPAS) based on well‐aligned carbon nanotube (CNT) arrays are demonstrated. The polarization‐sensitive CNT photodetector exhibits anisotropic ratios of ≈5.18 and ≈7.56 at 1800 and 2000 nm wavelengths, respectively, and high‐resolution characteristics that can be utilized to image SWIR laser spots with a radius of less than 10 µm. Furthermore, MIPAS including a CNT field‐effect transistor, a CNT loading resistor, and a polarization‐sensitive CNT photodetector is used to increase the anisotropic ratio of the CNT photodetector. The amplified anisotropic ratio is improved up to 173 and 243 at 1800 and 2000 nm wavelengths, respectively, which is the maximum reported in the SWIR band. Our work demonstrates that the CNT polarization‐sensitive photodetector has the potential for SWIR polarization imaging with a monolithic integrated polarization amplification system.

A polarization-dependent near-infrared metamaterial absorber based on the hybrid halide perovskite in two orthogonal directions

A wide-angle and polarization-sensitive metamaterial absorber is highly desired for near-infrared optical applications, such as stealth coatings, photovoltaic materials, and detectors. Although current near-infrared metamaterial absorbers achieve high absorption rates, they are typically either polarization-independent or only sensitive to one direction. Herein, a (CH3NH3)PbBr3-based perfect absorber with high absorption in both orthogonal directions and polarization sensitivity has been designed. The maximum absorption in the transverse magnetic (TM)-polarized light exceeds 99.6% at 800–1000 nm. The maximum absorption in the transverse electric (TE)-polarized light exceeds 98.9% at 1500–1800 nm, and the peak absorption is more than 84.3% at 1800–2200 nm using finite-difference time-domain methods. By modifying various structural parameters, the absorption of the absorber could be separately shifted in a wide wavelength region. In addition, the designed absorber maintains good performance at large angles of incidence. This structure can be applied to other hybrid perovskite materials by simply changing the structural parameters. These results present a huge potential for applications based on metamaterial absorbers, such as infrared polarization imaging, selective spectral detection, near-infrared sensing, and polarization multiplexing.

Noise-aware infrared polarization image fusion based on salient prior with attention-guided filtering network.

Infrared polarization image fusion integrates intensity and polarization information, producing a fused image that enhances visibility and captures crucial details. However, in complex environments, polarization imaging is susceptible to noise interference. Existing fusion methods typically use the infrared intensity (S0) and degree of linear polarization (DoLP) images for fusion but fail to consider the noise interference, leading to reduced performance. To cope with this problem, we propose a fusion method based on polarization salient prior, which extends DoLP by angle of polarization (AoP) and introduces polarization distance (PD) to obtain salient target features. Moreover, according to the distribution difference between S0 and DoLP features, we construct a fusion network based on attention-guided filtering, utilizing cross-attention to generate filter kernels for fusion. The quantitative and qualitative experimental results validate the effectiveness of our approach. Compared with other fusion methods, our method can effectively suppress noise interference and preserve salient target features.

Analysis of infrared polarization imaging characteristics based on long wave infrared zoom system

In order to meet the requirements of target detection at different distances in infrared polarization detection, a transmission-type long-wave infrared polarization zoom optical system is designed, can zoom in 18–90 mm and the wavelength range is 8–14 μm. The spatial resolution is 0.18–0.9 mrad, and the machining and assembly errors are analyzed. Based on BRDF and Stokes vector model, aluminum is spontaneous emission, and reflected emission characteristics under specific conditions are simulated and analyzed. Infrared polarization imaging and island imaging experiments verify the unique advantages of infrared polarization technology in distinguishing natural and manufactured objects, metal and non-metal, and high-temperature object recognition. The changing trend of contrast between infrared intensity image and polarization image with solar altitude angle is explored, providing theoretical support for developing an infrared photoelectric detection field.

Demosaicking DoFP images using edge compensation method based on correlation.

With the development of nanotechnology, the division of focal plane (DoFP) infrared polarization imaging system with real-time imaging has matured. Meanwhile, the demand for real-time acquisition of polarization information is growing, but the super-pixel structure of the DoFP polarimeter will bring instantaneous field of view (IFoV) errors. Existing polarization demosaicking methods cannot satisfy both accuracy and speed in terms of efficiency and performance. According to the characteristics of DoFP, this paper proposes an edge compensation demosaicking method by analyzing the channel correlations of polarized images. The method performs demosaicing in the differential domain, and the proposed method's performance is verified by comparison experiments using synthetic and authentic polarized images in the near-infrared (NIR) band. The proposed method outperforms the state-of-the-art methods in terms of accuracy and efficiency. It achieves an average peak signal-to-noise ratio (PSNR) improvement of 2 db on public datasets compared to current state-of-the-art methods. A typical 768 × 1024 specification short-wave infrared (SWIR) polarized image can be processed in 0.293s on the Intel Core i7-10870 H CPU, and the technique significantly outperforms various existing demosaicking methods.

Design of an Au–Pt–Ti wire-grid polarizer based on midinfrared pixelated micropolarizer arrays

Polarization information is widely used in complex applications such as industrial detection, biomedicine, earth remote sensing, modern military, and aerospace. However, traditional polarization devices cannot adequately satisfy the requirements of increasingly complex environments. A subwavelength grating consisting of three types of materials, namely, aurum, platinum, and titanium, was designed to improve the performance of the polarimetric components of a midwavelength infrared polarization imaging system. The morphological structure parameters of the designed grating were optimized by analyzing the effects on the polarization performance through the rigorous coupled wave theory. The proposed Au–Pt–Ti composite grating could address the problem of grating peeling off from the substrate because of high temperature during preparation. The composite grating has some advantages such as high mechanical stability, lower oxidation, and great polarization properties. The diffraction can be reduced and the extinction ratio (ER) can be effectively enhanced in a midwave infrared (MWIR) focal plane array through appropriate reduction in the termination edge spacing and the addition of a gold frame between polarizer pixels. The grating with a period of 0.8 μm was designed for application in the MWIR band. The fill factor was 0.5 and the depths of Au–Pt–Ti in the grating region were 0.44 μm. Each pixel was separated by a 3.2-μm wide gold frame. Modeling results revealed that the ER of grating was higher than 28.68 and 32.77 above the incident wavelengths of 3.89 and 4.57 μm, respectively. Additionally, excellent polarization capability was observed over a wide MWIR spectrum. Furthermore, the current manufacturing process level may generate polarizers with the aforementioned structural specifications.

Ultrahigh Extinction Ratio Long‐Wave Infrared Polarization‐Selective Broadband Metamaterial Absorber

Metamaterial absorbers (MAs) provide new miniaturization, integration, and high‐performance solution for infrared polarization imaging systems. However, it is challenging for past MAs to obtain broadband absorption and a high extinction ratio simultaneously. Herein, a long‐wave infrared broadband polarization‐selective MA with an ultrahigh extinction ratio is proposes and numerically demonstrated. The MA is composed of a metal–dielectric–metal sandwich structure. The cut‐wire resonator on the top layer and the wire pair on the bottom layer provide the MA with excellent polarization selectivity. In the wavelength range of 8.28–14.15 μm, the absorption of the Transverse Magnetic (TM) wave is greater than 90%, while the absorption of the Transverse Electric (TE) wave is less than 0.15%, and the average extinction ratio reaches 724. The high extinction ratio remains to reach 119 when the MA is integrated into a silicon substrate. This work promises to bring new solutions to infrared polarization imaging.

Research progress of short-wavelength infrared polarization imaging technologies

与传统成像系统相比，偏振成像系统通过探测目标物在不同状态下的明显偏振差异，提高对目标物的探测和识别能力，因而被广泛应用于复杂环境或有伪装物的目标探测。特别是短波红外谱范围的信息探测可以提供人眼所不能看见的分辨率和细节，是目前军事和民用领域的重点研究方向之一。这篇综述归纳总结了传统偏振成像系统的结构分类及其特点，探讨了新型微纳偏振成像系统的研究进展，并针对目前短波红外偏振成像技术存在的主要问题提供了可行性分析和建议。

Design and Experimental Analysis of Micropolarization Array Based on a Long-Wave Infrared Optical System

Aiming at the shortcomings of the traditional infrared polarization imaging device, such as large volume, complex structure, difficult registration, and inability to recognize moving targets, this paper proposes an infrared polarization imaging method based on a micropolarizer. The long refractive wave infrared polarization optical system is designed to achieve the imaging detection of a 0.25 m target at 1 km; for this, a design of a micropolarizer array suitable for the long-wave infrared band is proposed. In the simulation analysis, the effects of the grating substrate and line grating material, grating period, duty cycle, and grating slot depth on the polarization performance of grating are discussed, respectively. Through infrared polarization imaging experiments on typical targets, the unique advantages of infrared polarization technology in distinguishing metal and non-metal, natural and artificial objects, and high-temperature object recognition are verified, which provides practical support for physical evidence searches and camouflage target recognition.

Review of thermal infrared polarimetry, part 2: experiment

After the discussion on thermal polarization theory from part 1 of this review, we now review practical methods for experimentally measuring infrared polarization properties. Starting with a model for thermal emission from inhomogeneous media, we discuss the complexities of paints and how to determine the ideal thickness of paints used for blackbody simulators. Another commonly used inhomogeneous material is anodized aluminum, and we provide an extensive discussion of its fascinating structure and its optical properties in the thermal infrared. Theoretical analysis and experimental measurements show how the peculiar properties of alumina in the longwave infrared region combine to create a material that has a surprisingly high emissivity, for optically smooth sapphire and highly inhomogeneous anodize-coated aluminum. To illustrate features of thermal polarization theory given in part 1 of this review, we also present a series of infrared polarization images, and demonstrate the use of a convenient reference source for thermal polarization testing.

High-Performance Ultra-Broadband Absorber for Polarized Long-Wavelength Infrared Light Trapping

Conventional infrared polarization imaging and detection systems are normally complex, bulky, and expensive, since rare existing absorber components possess polarization selectivity, especially in the long-wavelength infrared (LWIR) range. In this study, we propose a novel high-performance metamaterial absorber with ultra-broadband high absorption and polarization selectivity in the entire LWIR atmospheric window. The absorber can realize an absorptance higher than 90% with a 4750 nm bandwidth due to different surface plasmons coupled with optical phonons. It exhibits precise polarization-selective absorption at the target wavelength; specifically, it can selectively trap TM-polarized light while restricting the absorption of TE-polarized light. In addition, the designed metamaterial exhibits remarkable spectral stability when the geometric parameters of the microstructure change, which is of great benefit in its manufacturing process. The proposed ultra-thin absorber provides a promising approach to simplify LWIR imaging and detection systems and further improve their performance.

TIPFNet: a transformer-based infrared polarization image fusion network

The fusion of infrared intensity and polarization images can generate a single image with better visible perception and more vital information. Existing fusion methods based on a convolutional neural network (CNN), with local feature extraction, have the limitation of fully exploiting salient target features of polarization. In this Letter, we propose a transformer-based deep network to improve the performance of infrared polarization image fusion. Compared with existing CNN-based methods, our model can encode long-range features of infrared polarization images to obtain global contextual information using the self-attention mechanism. We also design a loss function with the self-supervised constraint to boost the performance of fusion. Experiments on the public infrared polarization dataset validate the effectiveness of the proposed method. Our approach achieves better fusion performance than the state-of-the-art.

A temperature-controlled mid-wave infrared polarization radiation source with adjustable degree of linear polarization

This paper proposes a temperature-controlled mid-wave infrared polarization radiation source with adjustable degree of linear polarization (DoLP), referred to as TMPSD, which will be useful for the polarization performance measurements of the thermal polarization imaging systems. The main parts of the TMPSD are a standard blackbody source, a variable temperature cell holder and a mid-wave infrared polarizer placed in it. The experimental results show that when the temperature range of the blackbody source changes between 20 °C and 100 °C, and that of the polarizer between −120 °C and 20 °C, the DoLP of the radiation emitted from the TMPSD is 0.2683–0.9072 in the 3.0–5.2 μm bandwidth. The TMPSD exhibiting the large dynamic range and high accuracy can be readily adjusted. It is expected that the proposed TMPSD will effectively improve the quantitative accuracy of infrared polarization imaging systems during performance calibration and testing of mid-wave infrared polarization imaging systems.