Dual-band Imaging Research Articles

Design of an integrated imaging system of airborne SAR and visible light camera based on common aperture antenna.

In recent years, the advantages of multi-sensor integration are gradually highlighted. In this paper, an integrated imaging system (IIS) of airborne synthetic aperture radar (SAR) and visible light camera (VLC) based on common aperture antenna is designed to meet the mission requirement of acquiring visible light and SAR images simultaneously. The IIS adopts the coaxial scheme, its structure is simple and compact, and is more suitable for airborne platform. In this paper, a parameter design method of IIS based on common aperture antenna is proposed. After the system parameters design, the imaging performance of IIS is analyzed by simulation. The results show that the system parameters are designed reasonably and the imaging performance meets the mission requirement. The designed IIS can realize the visible and Ka-band (30 GHz) dual-band imaging. Under the condition of 20 km altitude, the imaging resolutions of VLC and SAR are higher than 0.2 m and 0.3 m respectively, the field of view of VLC is 1.46°, and the swath length of SAR is greater than 870 m.

Independently Accessible Dual-Band Barrier Infrared Detector Using Type-II Superlattices

We report a novel dual-band barrier infrared detector (DBIRD) design using InAs/GaSb type-II superlattices (T2SLs). The DBIRD structure consists of back-to-back barrier diodes: a “blue channel” (BC) diode which has an nBp architecture, an n-type layer of a larger bandgap for absorbing the blue band infrared/barrier/p-type layer, and a “red channel” (RC) diode which has a pBn architecture, a p-type layer of a smaller bandgap for absorbing the red band infrared/barrier/n-type layer. Each has a unipolar barrier using a T2SL lattice matched to a GaSb substrate to impede the flow of majority carriers from the absorbing layer. Each channel in the DBIRD can be independently accessed with a low bias voltage as is preferable for high-speed thermal imaging. The device modeling of DBIRDs and simulation results of the current–voltage characteristics under dark and illuminated conditions are also presented. They predict that the dual-band operation of the DBIRD will produce low dark currents and 45–56% quantum efficiencies for the in-band photons in the BC with λc = 5.58 μm, and a nearly constant 32% in the RC with λc = 8.05 μm. The spectral quantum efficiency of the BC for 500 K blackbody radiation is approximately 50% over the range of λ = 3–4.7 μm, while that of the RC has a peak of 42% at 5.9 μm. The DBIRD may provide improved high-speed dual-band imaging in comparison with NBn dual-band detectors.

Grayscale two-photon 3D printed gradient-refractive-index metamaterial lens for dual-band mid-infrared imaging

Gradient refractive index (GRIN) metamaterial lenses can achieve multi-band fusion infrared imaging and has the characteristics of integration, light weight, and achromaticity, compared with existing curved refractive lenses group. Constructing a three-dimensional (3D) GRIN lens for dual-band (3.0–5.0 and 7.5–9.2 µm) mid-infrared imaging is challenging due to the difficulty of fabricating the desired 3D GRIN materials with continuously changing linewidths. Here, we present a 3D self-focusing GRIN lens with a cylindrical symmetry configuration in the mid-infrared band. Such a 3D GRIN lens is designed with gradient woodpile polymer metamaterials based on effective medium theory and fabricated with high fidelity by grayscale two-photon lithography. Simulated and experimental results simultaneously exhibit a 3D GRIN lens possessing dual-band, achromatic, near-diffraction-limit focusing on the wavelengths of 4.5 and 7.5 µm. The protocol for developing the 3D GRIN lens with dual-band fusion imaging would prompt potential applications in integrated light-coupled devices and lightweight infrared imaging devices.

Dual-band color fusion image quality assessment based on color descriptors

Dual-band color fusion image quality assessment based on color descriptors

Confocal laser endomicroscopy as predictive biomarker of clinical and endoscopic efficacy of vedolizumab in ulcerative colitis: The DETECT study.

In patients with ulcerative colitis (UC), no biomarker is available to help the physician to choose the most suitable biotherapy. The primary objective of this pilot study was to assess the feasibility of identification of α4β7- and TNF-expressing cells, to predict the response to vedolizumab using confocal laser endoscopy (CLE). Patients with moderate-to-severe UC, naïve of biotherapy, received vedolizumab. Clinical evaluation was performed at each infusion. Endoscopic evaluation was performed before inclusion and at week 22. Fresh colonic biopsies were stained using FITC-labelled vedolizumab and Alexa fluor-labelled adalimumab and ex vivo dual-band CLE images were acquired. Blood samples were collected to measure trough concentrations of vedolizumab and to determine absolute counts of T and B cells subpopulations, NK cells and monocytes. Nineteen patients were enrolled in the study and received at least one dose of vedolizumab. Clinical remission and endoscopic improvement were observed in 58% of whom 5 patients (45%) had an endoscopic subscore of 0. In terms of clinical response and remission, endoscopic improvement and histologic response, FITC-conjugated vedolizumab staining tended to be higher in responder patients compared to non-responders at week 22. A threshold value of 6 positive FITC-vedolizumab staining areas detected by CLE seemed informative to discriminate the responders and non-responders. The results were similar in terms of clinical remission and endoscopic improvement with a sensitivity of 78% and a specificity of 85% (p = 0.05). Trough concentrations and blood immune cells were not associated with responses to vedolizumab. This pilot study demonstrate that dual-band CLE is feasible to detect α4β7- and TNF-expressing cells. Positive α4β7 staining seems to be associated with clinical and endoscopic remission in UC patients treated by anti-α4β7-integrin, subject to validation by larger-scale studies. Clinical-trial.gov: NCT02878083.

Dual-band low-light image enhancement

Dual-band low-light image enhancement

Optical design of a visible/short-wave infrared common-aperture optical system with a long focal length and a wide field-of-view.

Addressing the urgent need for long-distance dim target detection with a wide field-of-view and high sensitivity, this paper proposes a visible and short-infrared dual-band common-aperture optical system characterized by a broad field and extended focal length. To achieve system miniaturization and high-sensitivity target detection, the visible and infrared optical systems share a Ritchey-Chretien primary and secondary mirror. The primary optical path is segmented into visible light (0.45-0.75µm) and short-wave infrared (SWIR) (2-3µm) bands by a dichroic spectral splitter prism. The SWIR optical system utilizes four short-wave cooled infrared detectors, and wide-field stitching is achieved using a field-of-view divider. While ensuring the high cold-shield efficiency of cooled infrared detectors, this common-aperture optical system delivers visible and SWIR dual-band images with expansive fields, elongated focal lengths, and sizable apertures. The visible-light optical system has a focal length of 277mm, a field-of-view of 2.3∘×2.3∘, and an entrance pupil diameter of 130mm. Meanwhile, the SWIR optical system features a focal length of 480mm, a field-of-view of 2.26∘×1.8∘ and an entrance pupil diameter of 160mm. The design outcomes suggest that the imaging quality of the optical system approaches the diffraction limit. This visible/SWIR common-aperture optical system exhibits high sensitivity, a large field-of-view, compact structure, and excellent imaging quality, thereby meeting the requirements for long-distance dim target detection and imaging.

Dual-Band Image Fusion Approach Using Regional Weight Analysis Combined with a Multi-Level Smoothing Filter

Image fusion is an effective and efficient way to express the feature information of an infrared image and abundant detailed information of a visible image in a single fused image. However, obtaining a fused result with good visual effect, while preserving and inheriting those characteristic details, seems a challenging problem. In this paper, by combining a multi-level smoothing filter and regional weight analysis, a dual-band image fusion approach is proposed. Firstly, a series of dual-band image layers with different details are obtained using smoothing results. With different parameters in a bilateral filter, different smoothed results are achieved at different levels. Secondly, regional weight maps are generated for each image layer, and then we fuse the dual-band image layers with their corresponding regional weight map. Finally, by imposing proper weights, those fused image layers are synthetized. Through comparison with seven excellent fusion methods, both subjective and objective evaluations for the experimental results indicate that the proposed approach can produce the best fused image, which has the best visual effect with good contrast, and those small details are preserved and highlighted, too. In particular, for the image pairs with a size of 640 × 480, the algorithm could provide a good visual effect result within 2.86 s, and the result has almost the best objective metrics.

Self-powered SnSx/TiO2 photodetectors (PDs) with dual-band binary response and the applications in imaging and light-encrypted logic gates

In this work, we report the design and fabrication of self-powered binary response PDs based on II-type heterostructures consisting of SnSx nanoflakes (NFs) and rutile TiO2 nanorod arrays (NRs). The TiO2 NRs effectively block light with wavelengths below 400 nm from reaching SnSx. Under 385 nm light, the photoelectrons in TiO2 recombine with holes in SnSx at the interface due to the energy band bending, resulting in a positive photocurrent. Under 410 nm light, the photoelectrons in SnSx and the photogenerated holes in TiO2 accumulate at the interface, overcoming the interfacial potential barriers induced by the higher Fermi levels of SnSx and inducing a negative photocurrent. Based on the bipolar response, the dual-band imaging capability without external filters and the light-encrypted OR, AND, and NOT logic gates using a single device are demonstrated. This work provides a blueprint for the development of multifunctional self-powered PDs that can simplify system architecture, reduce the energy consumption, and improve accuracy for applications, such as visual systems, light-controlled logic circuits, and encrypted optical communications.

Iterative Network for Disparity Prediction with Infrared and Visible Light Images Based on Common Features.

In recent years, the range of applications that utilize multiband imaging has significantly expanded. However, it is difficult to utilize multichannel heterogeneous images to achieve a spectral complementarity advantage and obtain accurate depth prediction based on traditional systems. In this study, we investigate CFNet, an iterative prediction network, for disparity prediction with infrared and visible light images based on common features. CFNet consists of several components, including a common feature extraction subnetwork, context subnetwork, multimodal information acquisition subnetwork, and a cascaded convolutional gated recurrent subnetwork. It leverages the advantages of dual-band (infrared and visible light) imaging, considering semantic information, geometric structure, and local matching details within images to predict the disparity between heterogeneous image pairs accurately. CFNet demonstrates superior performance in recognized evaluation metrics and visual image observations when compared with other publicly available networks, offering an effective technical approach for practical heterogeneous image disparity prediction.

Polarization Reversal of Group IV-VI Semiconductors with Pucker-Like Structure: Mechanism Dissecting and Function Demonstration.

Polarization imaging presents advantages in capturing spatial, spectral, and polarization information across various spectral bands. It can improve the perceptual ability of image sensors and has garnered more applications. Despite its potential, challenges persist in identifying band information and implementing image enhancement using polarization imaging. These challenges often necessitate integrating spectrometers or other components, resulting in increased complexities within image processing systems and hindering device miniaturization trends. Here, the characteristics of anisotropic absorption reversal are systematically elucidated in pucker-like group IV-VI semiconductors MX (M=Ge, Sn; X=S, Se) through theoretical predictions and experimental validations. Additionally, the fundamental mechanisms behind anisotropy reversal in different bands are also explored. The photodetector is constructed by utilizing MX as a light-absorbing layer, harnessing polarization-sensitive photoresponse for virtual imaging. The results indicate that the utilization of polarization reversal photodetectors holds advantages in achieving further multifunctional integration within the device structure while simplifying its configuration, including band information identification and image enhancement. This study provides a comprehensive analysis of polarization reversal mechanisms and presents a promising and reliable approach for achieving dual-band image band identification and image enhancement without additional auxiliary components.

DBPFNet: a dual-band polarization image fusion network based on the attention mechanism and atrous spatial pyramid pooling.

In the current image fusion techniques, typically dual-band images are fused to obtain a fused image with salient target information, or intensity and polarization images are fused to achieve an image with enhanced visual perception. However, the current lack of dual-band polarization image datasets and effective fusion methods pose significant challenges for extracting more information in a single image. To address these problems, we construct a dataset containing intensity and polarization images in the visible and near-infrared bands. Furthermore, we propose an end-to-end image fusion network using attention mechanisms and atrous spatial pyramid pooling to extract key information and multi-scale global contextual information. Moreover, we design efficient loss functions to train the network. The experiments verify that the proposed method achieves better performance than the state-of-the-art in both subjective and objective evaluations.

An inner warp discovered in the disk around HD 110058 using VLT/SPHERE and HST/STIS

Context. An edge-on debris disk was detected in 2015 around the young, nearby A0V star HD 110058. The disk showed features resembling those seen in the disk of β Pictoris that could indicate the presence of a perturbing planetary-mass companion in the system. Aims. We investigated new and archival scattered light images of the disk in order to characterise its morphology and spectrum. In particular, we analysed the disk’s warp to constrain the properties of possible planetary perturbers. Methods. Using data from two VLT/SPHERE observations taken with the Integral Field Spectrograph (IFS) and near InfraRed Dual-band Imager and Spectrograph (IRDIS), we obtained high-contrast images of the edge-on disk. Additionally, we used archival data from HST/STIS with a poorer inner-working angle but a higher sensitivity to detect the outer parts of the disk. We measured the morphology of the disk by analysing vertical profiles along the length of the disk to extract the centroid spine position and vertical height. We extracted the surface brightness and reflectance spectrum of the disk. Results. We detect the disk between 20 au (with SPHERE) and 150 au (with STIS), at a position angle of 159.6° ± 0.6°. Analysis of the spine shows an asymmetry between the two sides of the disk, with a 3.4° ± 0.9° warp between ~20au and 60 au. The disk is marginally vertically resolved in scattered light, with a vertical aspect ratio of 9.3 ± 0.7% at 45 au. The extracted reflectance spectrum is featureless, flat between 0.95 µm and 1.1 µm, and red from 1.1 µm to 1.65 µm. The outer parts of the disk are also asymmetric with a tilt between the two sides compatible with a disk made of forward-scattering particles and seen not perfectly edge-on, suggesting an inclination of <84°. Conclusions. The presence of an undetected planetary-mass companion on an inclined orbit with respect to the disk could explain the warp. The misalignment of the inner parts of the disk with respect to the outer disk suggests a warp that has not yet propagated to the outer parts of the disk, favouring the scenario of an inner perturber as the origin of the warp.

Radio-continuum decrements associated to shadowing from the central warp in transition disc DoAr 44

ABSTRACT Warps have often been used to explain disc properties, but well-characterized examples are important due to their role in disc evolution. Scattered light images of discs with central gaps have revealed sharp warps, such that the outer rings are shadowed by tilted inner discs. The near-infrared intensity drops along the ring around T-Tauri star DoAr 44 have been interpreted in terms of a central warp. We report new ALMA observations of DoAr 44 in the continuum at 230 and 350 GHz (at ∼10 au), along with a new epoch of Spectro Polarimetric High-contrast Exoplanet REsearch (SPHERE)/Infrared Dual-band Imager and Spectrograph differential polarized imaging taken during excellent weather conditions. The ALMA observations resolve the ring and confirm the decrements proposed from deconvolution of coarse 336 GHz data. The scattered light image constrains the dips, which correspond to a misaligned inner disc with a relative inclination ξ = 21.4 $^{+6.7}_{-8.3}$ deg. The SPHERE intensity profile shows a morphological change compared to a previous epoch that may be interpreted as a variable orientation of the inner disc, from ξ ∼ 30 deg to ξ ∼ 20 deg. The intensity dips probably correspond to temperature decrements, as their mm-spectral index, $\alpha ^{230 \textrm {GHz}}_{350 \textrm {GHz}} \sim$ 2.0 ± 0.1, is indicative of optically thick emission. The azimuth of the two temperature decrements are leading clockwise relative to the infrared-dips, by η = 14.95 deg and η = 7.92 deg. For a retrograde disc, such shifts are expected from a thermal lag and imply gas surface densities of Σg = 117 ± 10 g cm−2 and Σg = 48 ± 10 g cm−2. A lopsided disc, with contrast ratio fr = 2.4 ± 0.5, is also consistent with the large continuum crescent.

An unmanned aerial vehicle (UAV)-borne dual-band polarization imaging system for evidence search

Existing evidence search systems mostly adopt traditional intensity imaging, which has low image contrast and is easily affected by environmental conditions, thus making it difficult to accurately identify the target and unable to meet the demand for evidence search in the case scene. To solve the aforementioned problems, we propose a combined visible polarization and long-wave infrared evidence search method, developed a high-resolution polarization imager, and perform a test to detect evidence with visible polarization and long-wave infrared imaging on unmanned aerial vehicles (UAVs). The results show that the target contrast is 10–20 % higher than that of traditional intensity imaging. And contrast ratio can be improved by up to 30% after graphics fusion processing. Therefore, the application of visible polarization and infrared combined imaging detection technology can significantly improve the search capability and system environmental adaptability of the evidence at the crime scene. In conclusion, the findings can significantly improve the efficiency of the case and are of great importance for effective and rapid search for evidence.

Design method of dual-band synchronous zoom optical system based on co-path zoom groups

The dual-band zoom imaging system has great application value in military and civilian fields with the advantages of a large field of view (FOV) search, long-range tracking, camouflaged target reconnaissance, and all-day operation. To address the problem of synchronous zoom in dual-band co-aperture zoom optical systems, a dual-band simultaneous zoom optical system design method based on the co-path zoom groups is proposed. This optical system can realize zooming simultaneously in visible (VIS) and shortwave infrared (SWIR) bands and effectively control the total length. We first analyze the synchronous zoom principle of the dual-band co-path zoom optical system, then we propose a joint solution method for solving the initial structure of the dual-band zoom optical system. After obtaining the initial structure parameters, we performed the real-lens replacement and aberration correction in Zemax. Finally, a dual-band co-path simultaneous zoom optical system with working bands of 900∼1700 nm and 480∼660 nm, and zoom ranges of 10∼150 mm and 100∼150 mm, respectively, was designed. The focal length difference of the dual-band optical system is less than 0.16% during the simultaneous zooming process, and the system also has the advantages of good imaging quality, compact structure, simple zoom structure, and smooth cam curve.

Research on objective assessment of dual-band color night vision fusion image quality based on scene understanding

Research on objective assessment of dual-band color night vision fusion image quality based on scene understanding

Ultra-compact dual band imaging spectrometer with freeform prisms.

Wide spectrum and miniaturization are the main challenges in the imaging spectrometer design. In this paper, we propose an ultra-compact dual band imaging spectrometer (CDBIS) with cemented freeform prisms, which works at both the visible-near-infrared (VNIR) from 400nm to 1000nm and the shortwave-infrared (SWIR) from 1000nm to 1700nm. The imaging spectrometer is only composed of three cemented prisms, a primary prism and two triangular prisms. And a freeform surface characterized by the Zernike polynomial is introduced in each prism. The CDBIS is dispersed by a diffraction grating, which is designed on the second surface of the primary prism. Based on vector aberration theory (VAT), the relationship among the astigmatism generated by the introduced freeform surfaces, the wavelength, and the field of view is studied. Accordingly, a wideband is realized by introducing the freeform surfaces after the diffraction grating. Furthermore, through optimizing the coefficients of Zernike polynomial terms, residual astigmatism at different wavelengths is well balanced. An imaging spectrometer with a volume of only 100c m 3 is obtained, with a spectral resolution of 1.45nm at VNIR and 2.40nm at SWIR, respectively. It has a huge potential for broadband space exploration.

Chasing extreme planetary architectures

Context. Planet(s) in binaries are unique architectures for testing predictions of planetary formation and evolution theories in very hostile environments. Their presence in such a highly perturbed region poses a clear challenge from the early phase of planetesimals accretion to the dynamical evolution and stability through a very long period of time (several Gyrs in some case). Aims. The combination of radial velocity, speckle interferometry, high-contrast imaging and high-precision astrometry with interfer-ometry, offers a unique and unprecedented set of observable to push the exploration of the extreme planetary system HD 196885. By dissecting the physical and orbital properties of each component, we aim at shedding light on its global architecture and stability. Methods. We used the IRDIS dual-band imager of SPHERE at VLT, and the speckle interferometric camera HRCAM of SOAR, to acquire high-angular resolution images of HD 196885 AB between 2015 and 2020. Radial velocity observations started in 1983 with CORAVEL at OHP have been extended with a continuous monitoring with CORALIE at La Silla, and ELODIE and SOPHIE at OHP over almost 40 yr extending the radial velocity measurements HD 196885 A and resolving both the binary companion and the inner giant planet HD 196885 Ab. Finally, we took advantage of the exquisite astrometric precision of the dual-field mode of VLTI/GRAVITY (down to 30 µas) to monitor the relative position of HD 196885 A and B to search for the 3.6 yr astrometric wobble of the circumpri-mary planet Ab imprinted on the binary separation. Results. Our observations enable to accurately constrain the orbital properties of the binary HD 196885 AB, seen on an inclined and retrograde orbit (iAB = 120.43 deg) with a semi-major axis of 19.78 au, and an eccentricity of 0.417. The GRAVITY measurements confirm for the first time the nature of the inner planet HD 196885 Ab by rejecting all families of pole-on solutions in the stellar or brown dwarf masses. The most favored island of solutions is associated with a Jupiter-like planet (MAb = 3.39 MJup), with moderate eccentricity (eAaAb = 0.44), and inclination close to 143.04 deg. This results points toward a significant mutual inclination (Ф = 24.36 deg) between the orbital planes (relative to the star) of the binary companion B and the planet Ab. Our dynamical simulations indicate that the system is dynamically stable over time. Eccentricity and mutual inclination variations could be expected for moderate von Zipele Kozai Lidov cycles that may affect the inner planet.

Small Zoom Mismatch Adjustment Method for Dual-Band Fusion Imaging System Based on Edge-Gradient Normalized Mutual Information.

Currently, automatic optical zoom setups are being extensively explored for their applications in search, detection, recognition, and tracking. In visible and infrared fusion imaging systems with continuous zoom, dual-channel multi-sensor field-of-view matching control in the process of synchronous continuous zoom can be achieved by pre-calibration. However, mechanical and transmission errors of the zoom mechanism produce a small mismatch in the field of view after co-zooming, degrading the sharpness of the fusion image. Therefore, a dynamic small-mismatch detection method is necessary. This paper presents the use of edge-gradient normalized mutual information as an evaluation function of multi-sensor field-of-view matching similarity to guide the small zoom of the visible lens after continuous co-zoom and ultimately reduce the field-of-view mismatch. In addition, we demonstrate the use of the improved hill-climbing search algorithm for autozoom to obtain the maximum value of the evaluation function. Consequently, the results validate the correctness and effectiveness of the proposed method under small changes in the field of view. Therefore, this study is expected to contribute to the improvement of visible and infrared fusion imaging systems with continuous zoom, thereby enhancing the overall working of helicopter electro-optical pods, and early warning equipment.