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Arieli, U., M. Mrejen y H. Suchowski. "Broadband coherent hyperspectral near-field imaging of plasmonic nanostructures". Optics Express 27, n.º 7 (25 de marzo de 2019): 9815. http://dx.doi.org/10.1364/oe.27.009815.
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Boniface, Antoine, Ivan Gusachenko, Kishan Dholakia y Sylvain Gigan. "Rapid broadband characterization of scattering medium using hyperspectral imaging". Optica 6, n.º 3 (4 de marzo de 2019): 274. http://dx.doi.org/10.1364/optica.6.000274.
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Muddiman, Ryan y Bryan Hennelly. "Broadband CARS high-throughput single-cell imaging". EPJ Web of Conferences 287 (2023): 03018. http://dx.doi.org/10.1051/epjconf/202328703018.
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Broadband Coherent anti-Stokes Raman Scattering (BCARS) enables the whole vibrational spectrum of cytologically prepared samples to be obtained using a hyperspectral raster scan approach. This technique has the potential to enable high-throughput automated detection of cell abnormalities. Images are distorted by the non-resonant background which requires a treatment for proper analysis. Using statistical denoising and phase retrieval returns Raman spectra similar to that of a spontaneous Raman measurement. Here, we present our work using this method for single-cell imaging of PEO1 ovarian adenocarcinoma cells prepared with the ThinPrep processor which enables label-free Raman cytology.
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Pei, Zhongming, Yong Mao Huang y Ting Zhou. "Review on Analysis Methods Enabled by Hyperspectral Imaging for Cultural Relic Conservation". Photonics 10, n.º 10 (29 de septiembre de 2023): 1104. http://dx.doi.org/10.3390/photonics10101104.
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In this review, the conservation methods for various types of cultural relics enabled by hyperspectral imaging are summarized, and the hyperspectral cameras and techniques utilized in the process from data acquisition to analyzation are introduced. Hyperspectral imaging is characterized by non-contact detection, broadband, and high resolution, which are of great significance to the non-destructive investigation of cultural relics. However, owing to the wide variety of cultural relics, the utilized equipment and methods vary greatly in the investigations of the associated conservation. Previous studies generally select a single type of cultural relic for conservation. That is, seldom study has focused on the application of hyperspectral techniques to generalized conservation methods that are simultaneously suitable for different types of cultural relics. Hence, some widely used hyperspectral cameras and imaging systems are introduced first. Subsequently, according to the previous investigations, the methods used for image acquisition, image correction, and data dimensionality reduction in hyperspectral techniques are described. Thirdly, a summary of methods in cultural relic conservation based on hyperspectral techniques is presented, which involves pigments, grottoes and murals, and painting and calligraphy. Later, some challenges and potential development prospects in hyperspectral-based methods are discussed for future study. Finally, the conclusions are given.
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Gattinger, Paul, Jakob Kilgus, Ivan Zorin, Gregor Langer, Ramin Nikzad-Langerodi, Christian Rankl, Martin Gröschl y Markus Brandstetter. "Broadband near-infrared hyperspectral single pixel imaging for chemical characterization". Optics Express 27, n.º 9 (19 de abril de 2019): 12666. http://dx.doi.org/10.1364/oe.27.012666.
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Judd, K. Peter. "Passive shortwave infrared broadband and hyperspectral imaging in a maritime environment". Optical Engineering 51, n.º 1 (9 de febrero de 2012): 013202. http://dx.doi.org/10.1117/1.oe.51.1.013202.
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Kho, Esther, Behdad Dashtbozorg, Lisanne L. de Boer, Koen K. Van de Vijver, Henricus J. C. M. Sterenborg y Theo J. M. Ruers. "Broadband hyperspectral imaging for breast tumor detection using spectral and spatial information". Biomedical Optics Express 10, n.º 9 (7 de agosto de 2019): 4496. http://dx.doi.org/10.1364/boe.10.004496.
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Ozeki, Yasuyuki, Wataru Umemura, Kazuhiko Sumimura, Norihiko Nishizawa, Kiichi Fukui y Kazuyoshi Itoh. "Stimulated Raman hyperspectral imaging based on spectral filtering of broadband fiber laser pulses". Optics Letters 37, n.º 3 (1 de febrero de 2012): 431. http://dx.doi.org/10.1364/ol.37.000431.
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Levy, Joseph, S. Craig Cary, Kurt Joy y Charles K. Lee. "Detection and community-level identification of microbial mats in the McMurdo Dry Valleys using drone-based hyperspectral reflectance imaging". Antarctic Science 32, n.º 5 (19 de mayo de 2020): 367–81. http://dx.doi.org/10.1017/s0954102020000243.
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AbstractThe reflectance spectroscopic characteristics of cyanobacteria-dominated microbial mats in the McMurdo Dry Valleys (MDVs) were measured using a hyperspectral point spectrometer aboard an unmanned aerial system (remotely piloted aircraft system, unmanned aerial vehicle or drone) to determine whether mat presence, type and activity could be mapped at a spatial scale sufficient to characterize inter-annual change. Mats near Howard Glacier and Canada Glacier (ASPA 131) were mapped and mat samples were collected for DNA-based microbiome analysis. Although a broadband spectral parameter (a partial normalized difference vegetation index) identified mats, it missed mats in comparatively deep (> 10 cm) water or on bouldery surfaces where mats occupied fringing moats. A hyperspectral parameter (B6) did not have these shortcomings and recorded a larger dynamic range at both sites. When linked with colour orthomosaic data, B6 band strength is shown to be capable of characterizing the presence, type and activity of cyanobacteria-dominated mats in and around MDV streams. 16S rRNA gene polymerase chain reaction amplicon sequencing analysis of the mat samples revealed that dominant cyanobacterial taxa differed between spectrally distinguishable mats, indicating that spectral differences reflect underlying biological distinctiveness. Combined rapid-repeat hyperspectral measurements can be applied in order to monitor the distribution and activity of sentinel microbial ecosystems across the terrestrial Antarctic.
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Wang, Chang, Xinyu Liu, Yang Zhang, Yan Sun, Zeqing Yu y Zhenrong Zheng. "Dual-Channel Switchable Metasurface Filters for Compact Spectral Imaging with Deep Compressive Reconstruction". Nanomaterials 13, n.º 21 (27 de octubre de 2023): 2854. http://dx.doi.org/10.3390/nano13212854.
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Spectral imaging technology, which aims to capture images across multiple spectral channels and create a spectral data cube, has been widely utilized in various fields. However, conventional spectral imaging systems face challenges, such as slow acquisition speed and large size. The rapid development of optical metasurfaces, capable of manipulating light fields versatilely and miniaturizing optical components into ultrathin planar devices, offers a promising solution for compact hyperspectral imaging (HSI). This study proposes a compact snapshot compressive spectral imaging (SCSI) system by leveraging the spectral modulations of metasurfaces with dual-channel switchable metasurface filters and employing a deep-learning-based reconstruction algorithm. To achieve compactness, the proposed system integrates dual-channel switchable metasurface filters using twisted nematic liquid crystals (TNLCs) and anisotropic titanium dioxide (TiO2) nanostructures. These thin metasurface filters are closely attached to the image sensor, resulting in a compact system. The TNLCs possess a broadband linear polarization conversion ability, enabling the rapid switching of the incidence polarization state between x-polarization and y-polarization by applying different voltages. This polarization conversion facilitates the generation of two groups of transmittance spectra for wavelength-encoding, providing richer information for spectral data cube reconstruction compared to that of other snapshot compressive spectral imaging techniques. In addition, instead of employing classic iterative compressive sensing (CS) algorithms, an end-to-end residual neural network (ResNet) is utilized to reconstruct the spectral data cube. This neural network leverages the 2-frame snapshot measurements of orthogonal polarization channels. The proposed hyperspectral imaging technology demonstrates superior reconstruction quality and speed compared to those of the traditional compressive hyperspectral image recovery methods. As a result, it is expected that this technology will have substantial implications in various domains, including but not limited to object detection, face recognition, food safety, biomedical imaging, agriculture surveillance, and so on.
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Reitzig, Sven, Franz Hempel, Julius Ratzenberger, Peter A. Hegarty, Zeeshan H. Amber, Robin Buschbeck, Michael Rüsing y Lukas M. Eng. "High-speed hyperspectral imaging of ferroelectric domain walls using broadband coherent anti-Stokes Raman scattering". Applied Physics Letters 120, n.º 16 (18 de abril de 2022): 162901. http://dx.doi.org/10.1063/5.0086029.
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Spontaneous Raman spectroscopy (SR) is a versatile method for analysis and visualization of ferroelectric crystal structures, including domain walls. Nevertheless, the necessary acquisition time makes SR impractical for in situ analysis and large scale imaging. In this work, we introduce broadband coherent anti-Stokes Raman spectroscopy (B-CARS) as a high-speed alternative to conventional Raman techniques and demonstrate its benefits for ferroelectric domain wall analysis. Using the example of poled lithium niobate, we compare the spectral output of both techniques in terms of domain wall signatures and imaging capabilities. We extract the Raman-like resonant part of the coherent anti-Stokes signal via a Kramers–Kronig-based phase retrieval algorithm and compare the raw and phase-retrieved signals to SR characteristics. Finally, we propose a mechanism for the observed domain wall signal strength that resembles a Čerenkov-like behavior, in close analogy to domain wall signatures obtained by second-harmonic generation imaging. We, thus, lay here the foundations for future investigations on other poled ferroelectric crystals using B-CARS.
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Gouisset, E., G. Rioland, F. Bourcier, D. Faye, P. Walter y F. Infante. "Detection and characterization of contamination with fluorescence spectroscopy". IOP Conference Series: Materials Science and Engineering 1287, n.º 1 (1 de agosto de 2023): 012025. http://dx.doi.org/10.1088/1757-899x/1287/1/012025.
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Abstract In the field of failure analysis and in particular molecular and particulate contamination, being able to detect any trace of contaminants during the integration of an orbital spacecraft is crucial. In this context, fluorescence allows not only to detect but also to discriminate contaminants. We studied the fluorescence response of two epoxy adhesives, typical sources of spacecraft contamination in orbit with a portable broadband hyperspectral instrument (UV-Vis-NIR) developed in collaboration with the CNES and Intraspec Technologies, but also with a commercial spectrofluorometer. These measurements had two objectives, evaluate the performance of our hyperspectral instrument in order to identify prospect of improvement, but as well study the pertinence of fluorescence signature study in the contamination field. The first goal brings out that the hyperspectral instrument is capable of imaging the scene and allows us to extract fluorescence spectra from the image, but it still needs development, especially in term of sensitivity in UV range. The second goal shows promising results. Fluorescence studies with the spectrofluorometer emphasize that fluorescence spectra are specific to the chemical nature of the contaminant, which allows us to clearly discriminate them.
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GUPTA, NEELAM. "HYPERSPECTRAL AND POLARIZATION IMAGING WITH DOUBLE-TRANSDUCER AOTFS FOR WIDER SPECTRAL COVERAGE". International Journal of High Speed Electronics and Systems 17, n.º 04 (diciembre de 2007): 845–55. http://dx.doi.org/10.1142/s0129156407005028.
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We have developed a number of programmable hyperspectral imagers operating from the ultraviolet to the longwave infrared using an acousto-optic tunable filter (AOTF) in conjunction with a suitable camera. Each of these AOTFs is fabricated with a single transducer to operate over only one octave in wavelength. Recently, we have developed two separate tellurium dioxide ( TeO 2) noncollinear AOTF cells that operate over two octave range. Each cell has an aperture of 1.5 × 1.5 cm 2 with a field-of-view of 4.2°, and two thin-plate lithium niobate transducers are bonded on it. The tuning range of the first cell is 0.43–2.1 μm , and 0.69–4.0 μm for the second cell. We have used each of these cells to carry out spectral imaging experiments with CCD, InGaAs , and InSb cameras to cover the spectral region from the visible to the midwave infrared. We image the two orthogonally polarized diffracted beams to get spectropolarimetric information from the scene, as well as a broadband image by using one of the undiffracted beams. In this paper, we discuss the two AOTF cells, the imaging experiments, and present the results obtained.
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Aneece, Itiya y Prasad Thenkabail. "Accuracies Achieved in Classifying Five Leading World Crop Types and their Growth Stages Using Optimal Earth Observing-1 Hyperion Hyperspectral Narrowbands on Google Earth Engine". Remote Sensing 10, n.º 12 (13 de diciembre de 2018): 2027. http://dx.doi.org/10.3390/rs10122027.
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As the global population increases, we face increasing demand for food and nutrition. Remote sensing can help monitor food availability to assess global food security rapidly and accurately enough to inform decision-making. However, advances in remote sensing technology are still often limited to multispectral broadband sensors. Although these sensors have many applications, they can be limited in studying agricultural crop characteristics such as differentiating crop types and their growth stages with a high degree of accuracy and detail. In contrast, hyperspectral data contain continuous narrowbands that provide data in terms of spectral signatures rather than a few data points along the spectrum, and hence can help advance the study of crop characteristics. To better understand and advance this idea, we conducted a detailed study of five leading world crops (corn, soybean, winter wheat, rice, and cotton) that occupy 75% and 54% of principal crop areas in the United States and the world respectively. The study was conducted in seven agroecological zones of the United States using 99 Earth Observing-1 (EO-1) Hyperion hyperspectral images from 2008–2015 at 30 m resolution. The authors first developed a first-of-its-kind comprehensive Hyperion-derived Hyperspectral Imaging Spectral Library of Agricultural crops (HISA) of these crops in the US based on USDA Cropland Data Layer (CDL) reference data. Principal Component Analysis was used to eliminate redundant bands by using factor loadings to determine which bands most influenced the first few principal components. This resulted in the establishment of 30 optimal hyperspectral narrowbands (OHNBs) for the study of agricultural crops. The rest of the 242 Hyperion HNBs were redundant, uncalibrated, or noisy. Crop types and crop growth stages were classified using linear discriminant analysis (LDA) and support vector machines (SVM) in the Google Earth Engine cloud computing platform using the 30 optimal HNBs (OHNBs). The best overall accuracies were between 75% to 95% in classifying crop types and their growth stages, which were achieved using 15–20 HNBs in the majority of cases. However, in complex cases (e.g., 4 or more crops in a Hyperion image) 25–30 HNBs were required to achieve optimal accuracies. Beyond 25–30 bands, accuracies asymptote. This research makes a significant contribution towards understanding modeling, mapping, and monitoring agricultural crops using data from upcoming hyperspectral satellites, such as NASA’s Surface Biology and Geology mission (formerly HyspIRI mission) and the recently launched HysIS (Indian Hyperspectral Imaging Satellite, 55 bands over 400–950 nm in VNIR and 165 bands over 900–2500 nm in SWIR), and contributions in advancing the building of a novel, first-of-its-kind global hyperspectral imaging spectral-library of agricultural crops (GHISA: www.usgs.gov/WGSC/GHISA).
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Stergar, Jošt, Rok Hren y Matija Milanič. "Design and Validation of a Custom-Made Laboratory Hyperspectral Imaging System for Biomedical Applications Using a Broadband LED Light Source". Sensors 22, n.º 16 (20 de agosto de 2022): 6274. http://dx.doi.org/10.3390/s22166274.
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Hyperspectral imaging (HSI) is a promising optical modality that is already being used in numerous applications. Further expansion of the capabilities of HSI depends on the modularity and versatility of the systems, which would, inter alia, incorporate profilometry, fluorescence imaging, and Raman spectroscopy while following a rigorous calibration and verification protocols, thus offering new insights into the studied samples as well as verifiable, quantitative measurement results applicable to the development of quantitative metrics. Considering these objectives, we developed a custom-made laboratory HSI system geared toward biomedical applications. In this report, we describe the design, along with calibration, characterization, and verification protocols needed to establish such systems, with the overall goal of standardization. As an additional novelty, our HSI system uses a custom-built broadband LED-based light source for reflectance imaging, which is particularly important for biomedical applications due to the elimination of sample heating. Three examples illustrating the utility and advantages of the integrated system in biomedical applications are shown. Our attempt presents both the development of a custom-based laboratory HSI system with novel LED light source as well as a framework which may improve technological standards in HSI system design.
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Dobler, Gregory, Federica B. Bianco, Mohit S. Sharma, Andreas Karpf, Julien Baur, Masoud Ghandehari, Jonathan Wurtele y Steven E. Koonin. "The Urban Observatory: A Multi-Modal Imaging Platform for the Study of Dynamics in Complex Urban Systems". Remote Sensing 13, n.º 8 (7 de abril de 2021): 1426. http://dx.doi.org/10.3390/rs13081426.
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We describe an “Urban Observatory” facility designed for the study of complex urban systems via persistent, synoptic, and granular imaging of dynamical processes in cities. An initial deployment of the facility has been demonstrated in New York City and consists of a suite of imaging systems—both broadband and hyperspectral—sensitive to wavelengths from the visible (∼400 nm) to the infrared (∼13 micron) operating at cadences of ∼0.01–30 Hz (characteristically ∼0.1 Hz). Much like an astronomical survey, the facility generates a large imaging catalog from which we have extracted observables (e.g., time-dependent brightnesses, spectra, temperatures, chemical species, etc.), collecting them in a parallel source catalog. We have demonstrated that, in addition to the urban science of cities as systems, these data are applicable to a myriad of domain-specific scientific inquiries related to urban functioning including energy consumption and end use, environmental impacts of cities, and patterns of life and public health. We show that an Urban Observatory facility of this type has the potential to improve both a city’s operations and the quality of life of its inhabitants.
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Dierssen, Heidi M., Kelley J. Bostrom, Adam Chlus, Kamille Hammerstrom, David R. Thompson y Zhongping Lee. "Pushing the Limits of Seagrass Remote Sensing in the Turbid Waters of Elkhorn Slough, California". Remote Sensing 11, n.º 14 (12 de julio de 2019): 1664. http://dx.doi.org/10.3390/rs11141664.
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Remote sensing imagery has been successfully used to map seagrass in clear waters, but here we evaluate the advantages and limitations of different remote sensing techniques to detect eelgrass in the tidal embayment of Elkhorn Slough, CA. Pseudo true-color imagery from Google Earth and broadband satellite imagery from Sentinel-2 allowed for detection of the various beds, but retrievals particularly in the deeper Vierra bed proved unreliable over time due to variable image quality and environmental conditions. Calibrated water-leaving reflectance spectrum from airborne hyperspectral imagery at 1-m resolution from the Portable Remote Imaging SpectroMeter (PRISM) revealed the extent of both shallow and deep eelgrass beds using the HOPE semi-analytical inversion model. The model was able to reveal subtle differences in spectral shape, even when remote sensing reflectance over the Vierra bed was not visibly distinguishable. Empirical methods exploiting the red edge of reflectance to differentiate submerged vegetation only retrieved the extent of shallow alongshore beds. The HOPE model also accurately retrieved the water column absorption properties, chlorophyll-a, and bathymetry but underestimated the particulate backscattering and suspended matter when benthic reflectance was represented as a horizontal eelgrass leaf. More accurate water column backscattering could be achieved by the use of a darker bottom spectrum representing an eelgrass canopy. These results illustrate how high quality atmospherically-corrected hyperspectral imagery can be used to map eelgrass beds, even in regions prone to sediment resuspension, and to quantify bathymetry and water quality.
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Applegate, Matthew B., Samuel S. Spink y Darren Roblyer. "Dual-DMD hyperspectral spatial frequency domain imaging (SFDI) using dispersed broadband illumination with a demonstration of blood stain spectral monitoring". Biomedical Optics Express 12, n.º 1 (24 de diciembre de 2020): 676. http://dx.doi.org/10.1364/boe.411976.
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Go, Sujung, Jhoon Kim, Sang Seo Park, Mijin Kim, Hyunkwang Lim, Ji-Young Kim, Dong-Won Lee y Jungho Im. "Synergistic Use of Hyperspectral UV-Visible OMI and Broadband Meteorological Imager MODIS Data for a Merged Aerosol Product". Remote Sensing 12, n.º 23 (5 de diciembre de 2020): 3987. http://dx.doi.org/10.3390/rs12233987.
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The retrieval of optimal aerosol datasets by the synergistic use of hyperspectral ultraviolet (UV)–visible and broadband meteorological imager (MI) techniques was investigated. The Aura Ozone Monitoring Instrument (OMI) Level 1B (L1B) was used as a proxy for hyperspectral UV–visible instrument data to which the Geostationary Environment Monitoring Spectrometer (GEMS) aerosol algorithm was applied. Moderate-Resolution Imaging Spectroradiometer (MODIS) L1B and dark target aerosol Level 2 (L2) data were used with a broadband MI to take advantage of the consistent time gap between the MODIS and the OMI. First, the use of cloud mask information from the MI infrared (IR) channel was tested for synergy. High-spatial-resolution and IR channels of the MI helped mask cirrus and sub-pixel cloud contamination of GEMS aerosol, as clearly seen in aerosol optical depth (AOD) validation with Aerosol Robotic Network (AERONET) data. Second, dust aerosols were distinguished in the GEMS aerosol-type classification algorithm by calculating the total dust confidence index (TDCI) from MODIS L1B IR channels. Statistical analysis indicates that the Probability of Correct Detection (POCD) between the forward and inversion aerosol dust models (DS) was increased from 72% to 94% by use of the TDCI for GEMS aerosol-type classification, and updated aerosol types were then applied to the GEMS algorithm. Use of the TDCI for DS type classification in the GEMS retrieval procedure gave improved single-scattering albedo (SSA) values for absorbing fine pollution particles (BC) and DS aerosols. Aerosol layer height (ALH) retrieved from GEMS was compared with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data, which provides high-resolution vertical aerosol profile information. The CALIOP ALH was calculated from total attenuated backscatter data at 1064 nm, which is identical to the definition of GEMS ALH. Application of the TDCI value reduced the median bias of GEMS ALH data slightly. The GEMS ALH bias approximates zero, especially for GEMS AOD values of >~0.4 and GEMS SSA values of <~0.95. Finally, the AOD products from the GEMS algorithm and MI were used in aerosol merging with the maximum-likelihood estimation method, based on a weighting factor derived from the standard deviation of the original AOD products. With the advantage of the UV–visible channel in retrieving aerosol properties over bright surfaces, the combined AOD products demonstrated better spatial data availability than the original AOD products, with comparable accuracy. Furthermore, pixel-level error analysis of GEMS AOD data indicates improvement through MI synergy.
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Khmaladze, Alexander, Joshua Jasensky, Erika Price, Chi Zhang, Andrew Boughton, Xiaofeng Han, Emily Seeley, Xinran Liu, Mark M. Banaszak Holl y Zhan Chen. "Hyperspectral Imaging and Characterization of Live Cells by Broadband Coherent Anti-Stokes Raman Scattering (CARS) Microscopy with Singular Value Decomposition (SVD) Analysis". Applied Spectroscopy 68, n.º 10 (octubre de 2014): 1116–22. http://dx.doi.org/10.1366/13-07183.
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Sequera, Pedro, Jorge E. González, Kyle McDonald, Steve LaDochy y Daniel Comarazamy. "Improvements in Land-Use Classification for Estimating Daytime Surface Temperatures and Sea-Breeze Flows in Southern California". Earth Interactions 20, n.º 16 (1 de junio de 2016): 1–32. http://dx.doi.org/10.1175/ei-d-14-0034.1.
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Abstract Understanding the interactions between large-scale atmospheric and oceanic circulation patterns and changes in land cover and land use (LCLU) due to urbanization is a relevant subject in many coastal climates. Recent studies by Lebassi et al. found that the average maximum air temperatures during the summer in two populated California coastal areas decreased at low-elevation areas open to marine air penetration during the period of 1970–2005. This coastal cooling was attributed to an increase in sea-breeze activity. The aims of this work are to better understand the coastal flow patterns and sea–land thermal gradient by improving the land-cover classification scheme in the region using updated airborne remote sensing data and to assess the suitability of the updated regional atmospheric modeling system for representing maritime flows in this region. This study uses high-resolution airborne data from the NASA Hyperspectral Infrared Imager (HyspIRI) mission preparatory flight campaign over Southern California and surface ground stations to compare observations against model estimations. Five new urban land classes were created using broadband albedo derived from the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) sensor and then assimilated into the Weather Research and Forecasting (WRF) Model. The updated model captures the diurnal spatial and temporal sea-breeze patterns in the region. Results show notable improvements of simulated daytime surface temperature and coastal winds using the HyspIRI-derived products in the model against the default land classification, reaffirming the importance of accounting for heterogeneity of urban surface properties.
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Gryko, Łukasz y Jakub Lewandowski. "Tunable LED illumination for biological tissue imaging". Photonics Letters of Poland 15, n.º 4 (31 de diciembre de 2023): 75–77. http://dx.doi.org/10.4302/plp.v15i4.1251.
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The article presents the results of biological tissue imaging with a tunable broadband LED illuminator with adjustable color and correlated color temperature of white light characterized by high color rendering indices. Color imaging of tissue is the basis for diagnostic procedures in various disease states. For this reason, it is essential to optimize the illumination so that differences in tissue color are highlighted not only by improved color fidelity but also by high color contrast. Full Text: PDF References M.H. Tran, B. Fei, "Compact and ultracompact spectral imagers: technology and applications in biomedical imaging", J Biomed Opt 28, 4 (2023). CrossRef E.J.M. Baltussen, E.N.D. Kok, S.G.J. Brouwer de Koning, "Hyperspectral imaging for tissue classification, a way toward smart laparoscopic colorectal surgery", J Biomed Opt 24, 1 (2019). CrossRef N.T. Clancy, G. Jones, L. Maier-Hein, D.S. Elson, and D. Stoyanov, "Surgical spectral imaging", Med Image Anal 63, 101699 (2020). CrossRef R. Zhang, Z. Guo, Y. Chen, "A Deep Learning-Aided Remote Spectrally Tunable LED Light Source Integrated System", IEEE Trans Instrum Meas 72, 1 (2023). CrossRef P. Liu, H. Wang, Y. Zhang, "Investigation of self-adaptive LED surgical lighting based on entropy contrast enhancing method", Opt Commun 319, 133 (2014). CrossRef J. Shen, S. Chang, H. Wang, Z. Zheng, Light. "Optimising the illumination spectrum for enhancing tissue visualisation", Res. Technol. 51, 99 (2019). CrossRef K. Kameyama, T. Ohbayashi, K. Uehara, A. Koga, Y. Hata, "The Influence of Illumination Color on the Subjective Visual Recognition of Biological Specimens", Yonago Acta Med 63, 266 (2020). CrossRef H. Wang, R.H. Cuijpers, M. R. Luo, I. Heynderickx, and Z. Zheng, "Optimal illumination for local contrast enhancement based on the human visual system", J Biomed Opt 20, 015005 (2015). CrossRef J. Mundinger, K. Houser, "Adjustable correlated colour temperature for surgical lighting", Light. Res. Technol. 51, 280 (2019). CrossRef M.A. Ilișanu, F. Moldoveanu, A. Moldoveanu, "Multispectral Imaging for Skin Diseases Assessment—State of the Art and Perspectives", Sensor 23, 3888 (2023). CrossRef K.L. Hanlon, G. Wei, L. Correa-Selm, and J.M. Grichnik, "Dermoscopy and skin imaging light sources: a comparison and review of spectral power distribution and color consistency", J Biomed Opt 27, 080902 (2022). CrossRef O.V. Mamontov, A.V. Shcherbinin, R.V. Romashko, "Intraoperative Imaging of Cortical Blood Flow by Camera-Based Photoplethysmography at Green Light", Appl Sci 10, 6192 (2020). CrossRef F.J. Burgos-Fernández, T. Alterini, F. Diaz-Douton, L. Gonzales, C. Mateo, C. Mestre, J. Pujol, M.Vilaseca, "Reflectance evaluation of eye fundus structures with a visible and near-infrared multispectral camera", Biomed Opt Express 13, 3504 (2022). CrossRef D. Kapsokalyvas, N. Bruscino, "Spectral morphological analysis of skin lesions with a polarization multispectral dermoscope", Opt Express 21, 4826 (2013). CrossRef J. Yang, H. Xu, F. Zhang, Z. Wang, P. Xu, "Enhancing local color contrast by optimizing multichannel LED light sources", Opt. Eng. 57, 1 (2018). CrossRef N. Posner, A. Stefanidi, J. Hanhart, Biomed. Eng. Res. (2020). DirectLink U.J. Blaszczak, L. Gryko, A. Zajac, "Tunable white light source for medical applications", Proc. SPIE, 10445 (2017), CrossRef L. Gryko, U. J. Blaszczak, A.S. Zajac, "Colorimetric characterization of the tunable LED-based light source at the output of the homogenizing rod", Proc SPIE, 1080811 (2018). CrossRef U.J. Błaszczak, Ł. Gryko, A.S. Zając, "Characterization of multi-emitter tuneable led source for endoscopic applications", Metrol. Meas. Syst. 26, 153 (2019). CrossRef U.J. Błaszczak, M. Gilewski, Ł. Gryko, A.S. Zając, "Badanie wpływu sposobu zasilania na wybrane parametry optyczne zestawu diod elektroluminescencyjnych", Przeglad Elektrotechniczny 92, 150 (2016). CrossRef
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Park, Jong-Uk, Hyun-Jae Kim, Jin-Soo Park, Jinsoo Choi, Sang Seo Park, Kangho Bae, Jong-Jae Lee et al. "Airborne observation with a low-cost hyperspectral instrument: retrieval of NO2 vertical column densities (VCDs) and the satellite sub-grid variability over industrial point sources". Atmospheric Measurement Techniques 17, n.º 1 (15 de enero de 2024): 197–217. http://dx.doi.org/10.5194/amt-17-197-2024.
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Abstract. High-spatial-resolution NO2 vertical column densities (VCDs) were retrieved from airborne observations using the low-cost hyperspectral imaging sensor (HIS) at three industrial areas (i.e., Chungnam, Jecheon, and Pohang) in South Korea, where point sources (i.e., power plant, petrochemical complex, steel yard, and cement kiln) with significant NO2 emissions are located. An innovative and versatile approach for NO2 VCD retrieval, hereafter referred to as the modified wavelength pair (MWP) method, was developed to overcome the excessively variable radiometric and spectral characteristics of the HIS attributed to the absence of temperature control during the flight. The newly developed MWP method was designed to be insensitive to broadband spectral features, including the spectral dependency of surface and aerosol reflectivity, and can be applied to observations with relatively low spectral resolutions. Moreover, the MWP method can be implemented without requiring precise radiometric calibration of the instrument (i.e., HIS) by utilizing clean-pixel data for non-uniformity corrections and is also less sensitive to the optical properties of the instrument and offers computational cost competitiveness. In the experimental flights using the HIS, NO2 plumes emitted from steel yards were particularly conspicuous among the various NO2 point sources, with peak NO2 VCDs of 2.0 DU (Dobson unit) at Chungnam and 1.8 DU at Pohang. Typical NO2 VCD uncertainties ranged between 0.025–0.075 DU over the land surface and 0.10–0.15 DU over the ocean surface, and the discrepancy can be attributable to the lower signal-to-noise ratio over the ocean and higher sensitivity of the MWP method to surface reflectance uncertainties under low-albedo conditions. The NO2 VCDs retrieved from the HIS with the MWP method showed a good correlation with the collocated Tropospheric Monitoring Instrument (TROPOMI) data (r=0.73, mean absolute error equals 0.106 DU). However, the temporal disparities between the HIS frames and the TROPOMI overpass, their spatial mismatch, and their different observation geometries could limit the correlation. The comparison of TROPOMI and HIS NO2 VCDs further demonstrated that the satellite sub-grid variability could be intensified near the point sources, with more than a 3-fold increase in HIS NO2 VCD variability (e.g., difference between 25th and 75th quantiles) over the TROPOMI footprints with NO2 VCD values exceeding 0.8 DU compared to footprints with NO2 VCD values below 0.6 DU.
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Zhang, Wenyi, Hongya Song, Xin He, Longqian Huang, Xiyue Zhang, Junyan Zheng, Weidong Shen, Xiang Hao y Xu Liu. "Deeply learned broadband encoding stochastic hyperspectral imaging". Light: Science & Applications 10, n.º 1 (25 de mayo de 2021). http://dx.doi.org/10.1038/s41377-021-00545-2.
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AbstractMany applications requiring both spectral and spatial information at high resolution benefit from spectral imaging. Although different technical methods have been developed and commercially available, computational spectral cameras represent a compact, lightweight, and inexpensive solution. However, the tradeoff between spatial and spectral resolutions, dominated by the limited data volume and environmental noise, limits the potential of these cameras. In this study, we developed a deeply learned broadband encoding stochastic hyperspectral camera. In particular, using advanced artificial intelligence in filter design and spectrum reconstruction, we achieved 7000–11,000 times faster signal processing and ~10 times improvement regarding noise tolerance. These improvements enabled us to precisely and dynamically reconstruct the spectra of the entire field of view, previously unreachable with compact computational spectral cameras.
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Guo, Kai, Duo Yang, Bingyi Liu y Zhongyi Guo. "Random broadband filters based on combination of metasurface and multilayer thin films for hyperspectral imaging". Journal of Physics D: Applied Physics, 25 de abril de 2024. http://dx.doi.org/10.1088/1361-6463/ad4370.
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Abstract Metasurface based micro-spectrometer presents a promising avenue for achieving compact, lightweight, and cost-effective solutions for miniaturization of hyperspectral imaging systems. Nevertheless, this type of design encounter limitations primarily due to constrained manipulation mechanism of light field, resulting in high cross-correlation among transmission spectra and imperfect reconstructed images. In this paper, we propose and numerically demonstrate a micro-spectrometer based on metasurface combined with multilayer thin films, whose spectral response improves performance for application, i.e. achieving low spectral cross-correlation. Additionally, we incorporate particle swarm optimization with compressed sensing algorithm to optimize the proposed micro-spectrometer. This approach effectively reconstructs both narrowband and broadband hyperspectral signals with minimal error, achieving an impressive 2nm spectral resolution. The simulation results of hyperspectral imaging demonstrated that the proposed methodology successfully reconstructs broadband hyperspectral images with an average spectral fidelity of 91.42%. This method holds significant potential for integrating into smartphones and other portable spectrometers, advancing the design of compact hyperspectral imaging systems.
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Fang, Jianan, Kun Huang, Ruiyang Qin, Yan Liang, E. Wu, Ming Yan y Heping Zeng. "Wide-field mid-infrared hyperspectral imaging beyond video rate". Nature Communications 15, n.º 1 (28 de febrero de 2024). http://dx.doi.org/10.1038/s41467-024-46274-z.
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AbstractMid-infrared hyperspectral imaging has become an indispensable tool to spatially resolve chemical information in a wide variety of samples. However, acquiring three-dimensional data cubes is typically time-consuming due to the limited speed of raster scanning or wavelength tuning, which impedes real-time visualization with high spatial definition across broad spectral bands. Here, we devise and implement a high-speed, wide-field mid-infrared hyperspectral imaging system relying on broadband parametric upconversion of high-brightness supercontinuum illumination at the Fourier plane. The upconverted replica is spectrally decomposed by a rapid acousto-optic tunable filter, which records high-definition monochromatic images at a frame rate of 10 kHz based on a megapixel silicon camera. Consequently, the hyperspectral imager allows us to acquire 100 spectral bands over 2600-4085 cm−1 in 10 ms, corresponding to a refreshing rate of 100 Hz. Moreover, the angular dependence of phase matching in the image upconversion is leveraged to realize snapshot operation with spatial multiplexing for multiple spectral channels, which may further boost the spectral imaging rate. The high acquisition rate, wide-field operation, and broadband spectral coverage could open new possibilities for high-throughput characterization of transient processes in material and life sciences.
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Bürsing, Helge y Wolfgang Gross. "Hyperspectral imaging: future applications in security systems". Advanced Optical Technologies 6, n.º 2 (1 de enero de 2017). http://dx.doi.org/10.1515/aot-2017-0007.
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AbstractThe idea behind hyperspectral imagers (HSI) is to generate an image with hundreds of contiguous narrow channels, the so-called spectral bands. As each material has a specific spectral signature, robust detection and classification of specific materials is now achievable. Spectra can be characterized by narrow features in their signatures that broadband and multispectral cameras cannot resolve. As a result of technical progress, new HSI with higher spatial resolution and better signal-to-noise ratios have been developed. Additionally, it is possible to buy small HSI that weigh less than 1 kg, which opens up new applications in surveillance and monitoring with unmanned aerial systems (UAS). Despite the capabilities of hyperspectral data evaluation, HSI is applied to surprisingly few tasks. This is a result of the sheer amount of recorded data that needs to be analyzed and the complex data pre-processing when the sensors are not used in a controlled environment. Also, extensive research is required to find the most efficient solution for a given task. The goal of this letter is to introduce and compare the different sensor techniques, discuss potential use for applications in civil security and give an outlook of future challenges.
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Giorgetta, Fabrizio R., Jean-Daniel Deschênes, Richard L. Lieber, Ian Coddington, Nathan R. Newbury y Esther Baumann. "Broadband dual-comb hyperspectral imaging and adaptable spectroscopy with programmable frequency combs". APL Photonics 9, n.º 1 (1 de enero de 2024). http://dx.doi.org/10.1063/5.0179270.
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We explore the advantages of a free-form dual-comb spectroscopy (DCS) platform based on time-programmable frequency combs for real-time, penalty-free apodized scanning. In traditional DCS, the fundamental spectral point spacing, which equals the comb repetition rate, can be excessively fine for many applications. While fine point spacing is not itself problematic, it comes with the penalty of excess acquisition time. Post-processing apodization (windowing) can be applied to tailor the resolution to the sample, but only with a deadtime penalty proportional to the degree of apodization. The excess acquisition time remains. With free-form DCS, this deadtime is avoided by programming a real-time apodization pattern that dynamically reverses the pulse periods between the dual frequency combs. In this way, one can tailor the spectrometer’s resolution and update rate to different applications without penalty. We show the operation of a free-form DCS system where the spectral resolution is varied from the intrinsic fine 160 MHz up to 822 GHz by applying tailored real-time apodization. Because there is no deadtime penalty, the spectral signal-to-noise ratio increases linearly with resolution by 5000× over this range, as opposed to the square root increase observed for post-processing apodization in traditional DCS. We explore the flexibility to change resolution and update rate to perform hyperspectral imaging at slow camera frame rates, where the penalty-free apodization allows for optimal use of each frame. We obtain dual-comb hyperspectral movies at a 20 Hz spectrum update rate with broad optical spectral coverage of over 10 THz.
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Chang, Kai-Hao, Yen-Chun Chen, Yo-Song Huang, Wei-Lun Hsu, Guo-Hao Lu, Chao-Feng Liu, Chun-Jen Weng et al. "Axicon metalens for broadband light harvesting". Nanophotonics, 8 de marzo de 2023. http://dx.doi.org/10.1515/nanoph-2023-0017.
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Abstract In this study, an axicon metalens comprising a large central disc surrounded by nanoposts for energy harvesting in composite metal-oxide semiconductor sensors was designed, fabricated, and experimentally characterized. The main role of the central disc is focusing light; the nanoposts of various diameters deflect light to form a Bessel-like beam. The spatial distribution of the optical transmission was measured using micro-hyperspectral imaging. The axicon metalens concentrates the light to the sensitive area of the sensor and also harvests light from adjacent pixels. After adding an axicon metalens, the normalized peak transmission is up to 250% at λ = 700 nm as compared to a blank TiO2 film. The experimental results had fair agreement with the finite-difference-time-domain simulation. The ultra-broadband energy-harvesting performance of the sensor suggests that it could be applied in surveillance and Internet of Things applications.
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Ebner, Alexander, Paul Gattinger, Ivan Zorin, Lukas Krainer, Christian Rankl y Markus Brandstetter. "Diffraction-limited hyperspectral mid-infrared single-pixel microscopy". Scientific Reports 13, n.º 1 (6 de enero de 2023). http://dx.doi.org/10.1038/s41598-022-26718-6.
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AbstractIn this contribution, we demonstrate a wide-field hyperspectral mid-infrared (MIR) microscope based on multidimensional single-pixel imaging (SPI). The microscope employs a high brightness MIR supercontinuum source for broadband (1.55 $$\upmu \hbox {m}$$ μ m –4.5 $$\upmu \hbox {m}$$ μ m ) sample illumination. Hyperspectral imaging capability is achieved by a single micro-opto-electro-mechanical digital micromirror device (DMD), which provides both spatial and spectral differentiation. For that purpose the operational spectral bandwidth of the DMD was significantly extended into the MIR spectral region. In the presented design, the DMD fulfills two essential tasks. On the one hand, as standard for the SPI approach, the DMD sequentially masks captured scenes enabling diffraction-limited imaging in the tens of millisecond time-regime. On the other hand, the diffraction at the micromirrors leads to dispersion of the projected field and thus allows for wavelength selection without the application of additional dispersive optical elements, such as gratings or prisms. In the experimental part, first of all, the imaging and spectral capabilities of the hyperspectral microscope are characterized. The spatial and spectral resolution is assessed by means of test targets and linear variable filters, respectively. At a wavelength of 4.15 $$\upmu \hbox {m}$$ μ m a spatial resolution of 4.92 $$\upmu \hbox {m}$$ μ m is achieved with a native spectral resolution better than 118.1 nm. Further, a post-processing method for drastic enhancement of the spectral resolution is proposed and discussed. The performance of the MIR hyperspectral microsopce is demonstrated for label-free chemical imaging and examination of polymer compounds and red blood cells. The acquisition and reconstruction of Hadamard sampled 64 $$\times$$ × 64 images is achieved in 450 ms and 162 ms, respectively. Thus, combined with an unprecedented intrinsic flexibiliy gained by a tunable field of view and adjustable spatial resolution, the demonstrated design drastically improves the sample throughput in MIR chemical and biomedical imaging.
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Katkovnik, Vladimir, Igor Shevkunov y Karen Egiazarian. "Admm and Spectral Proximity Operators in Hyperspectral Broadband Phase Retrieval for Quantitative Phase Imaging". SSRN Electronic Journal, 2023. http://dx.doi.org/10.2139/ssrn.4327878.
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Katkovnik, Vladimir, Igor Shevkunov y Karen Egiazarian. "ADMM and Spectral Proximity Operators in Hyperspectral Broadband Phase Retrieval for Quantitative Phase Imaging". Signal Processing, mayo de 2023, 109095. http://dx.doi.org/10.1016/j.sigpro.2023.109095.
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Skiles, S. McKenzie, Christopher P. Donahue, Adam G. Hunsaker y Jennifer M. Jacobs. "UAV hyperspectral imaging for multiscale assessment of Landsat 9 snow grain size and albedo". Frontiers in Remote Sensing 3 (12 de enero de 2023). http://dx.doi.org/10.3389/frsen.2022.1038287.
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Snow albedo, a measure of the amount of solar radiation that is reflected at the snow surface, plays a critical role in Earth’s climate and in regional hydrology because it is a primary driver of snowmelt timing. Satellite multi-spectral remote sensing provides a multi-decade record of land surface reflectance, from which snow albedo can be retrieved. However, this observational record is challenging to assess because discrete in situ observations are not well suited for validation of snow properties at the spatial resolution of satellites (tens to hundreds of meters). For example, snow grain size, a primary driver of snow albedo, can vary at the sub-meter scale driven by changes in aspect, elevation, and vegetation. Here, we present a new uncrewed aerial vehicle hyperspectral imaging (UAV-HSI) method for mapping snow surface properties at high resolution (20 cm). A Resonon near-infrared HSI was flown on a DJI Matrice 600 Pro over the meadow encompassing Swamp Angel Study Plot in Senator Beck Basin, Colorado. Using a radiative transfer forward modeling approach, effective snow grain size and albedo maps were produced from measured surface reflectance. Coincident ground observations were used for validation; relative to retrievals from a field spectrometer the mean grain size difference was 2 μm, with an RMSE of 12 μm, and the mean broadband albedo was within 1% of that measured near the center of the flight area. Even though the snow surface was visually homogenous, the maps showed spatial variability and coherent patterns in the freshly fallen snow. To demonstrate the potential for UAV-HSI to be used to improve validation of satellite retrievals, the high-resolution maps were used to assess grain size and albedo retrievals, and subpixel variability, across 17 Landsat 9 OLI pixels from a satellite overpass with similar conditions two days following the flight. Although Landsat 9 did not capture the same range of values and spatial variability as the UAV-HSI, on average the comparison showed good agreement, with a mean grain size difference of 9 μm and the same broadband albedo (86%).
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Qin, Jianwei, Oscar Monje, Matthew R. Nugent, Joshua R. Finn, Aubrie E. O’Rourke, Kristine D. Wilson, Ralph F. Fritsche, Insuck Baek, Diane E. Chan y Moon S. Kim. "A hyperspectral plant health monitoring system for space crop production". Frontiers in Plant Science 14 (4 de julio de 2023). http://dx.doi.org/10.3389/fpls.2023.1133505.
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Compact and automated sensing systems are needed to monitor plant health for NASA’s controlled-environment space crop production. A new hyperspectral system was designed for early detection of plant stresses using both reflectance and fluorescence imaging in visible and near-infrared (VNIR) wavelength range (400–1000 nm). The prototype system mainly includes two LED line lights providing VNIR broadband and UV-A (365 nm) light for reflectance and fluorescence measurement, respectively, a line-scan hyperspectral camera, and a linear motorized stage with a travel range of 80 cm. In an overhead sensor-to-sample arrangement, the stage translates the lights and camera over the plants to acquire reflectance and fluorescence images in sequence during one cycle of line-scan imaging. System software was developed using LabVIEW to realize hardware parameterization, data transfer, and automated imaging functions. The imaging unit was installed in a plant growth chamber at NASA Kennedy Space Center for health monitoring studies for pick-and-eat salad crops. A preliminary experiment was conducted to detect plant drought stress for twelve Dragoon lettuce samples, of which half were well-watered and half were under-watered while growing. A machine learning method using an optimized discriminant classifier based on VNIR reflectance spectra generated classification accuracies over 90% for the first four days of the stress treatment, showing great potential for early detection of the drought stress on lettuce leaves before any visible symptoms and size differences were evident. The system is promising to provide useful information for optimization of growth environment and early mitigation of stresses in space crop production.
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Mahmoud, Alaaeldin y Yasser H. El-Sharkawy. "Instant plastic waste detection on shores using laser-induced fluorescence and associated hyperspectral imaging". Optical and Quantum Electronics 56, n.º 5 (25 de marzo de 2024). http://dx.doi.org/10.1007/s11082-024-06564-8.
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AbstractPlastic pollution is a rising environmental issue, with millions of tons of plastic debris collecting in the world's seas and on its shores. Hyperspectral imaging (HSI) has become increasingly widely used as a more precise approach that can identify targets in remote sensing aquatic missions. The interference from other beach materials, and the need for proper identification of litter types can make identifying dumped plastics on sand-surrounded beaches challenging. This study lays the groundwork for a physical laboratory setting for images captured by a hyperspectral (HS) imager. The suggested testing setup included the development of a fluorescence signature for the target theater of operations (low-density polyethylene (LD-PE) and wood surrounded by sand) for detecting polymers in a simulated beach environment using the laser-induced fluorescence (LIF) approach. Initially using broadband-spectrum light, strong sample diffuse reflectance contrast is observed in the imaging at wavelengths between 400 and 460 nm. Next, a dedicated LIF system for plastic litter discovery was developed using an ultraviolet (UV) laser source. Initial findings show that there is a distinct fluorescence signal for plastics at 450 nm and at 750 nm for wood. Our pilot studies support current efforts to determine the optimum spectral signature that these polymers will appear with clarity on shorelines using an inexpensive imagery combined with our UV LIF approach, which may have an impact on applications for the detection of beach pollution. The knowledge gained from this study can be used to construct reliable aerial conventional cameras for plastic waste environmental monitoring and management.
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Parmar, Devang, Simone Dehm, Naga Anirudh Peyyety, Sandeep Kumar y Ralph Krupke. "Enhanced Broadband Photodetection with Geometry and Interface Engineered Nanocrystalline Graphite". Advanced Sensor Research, 20 de noviembre de 2023. http://dx.doi.org/10.1002/adsr.202300134.
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AbstractPhotodetection across the near‐infrared (NIR) to short‐wavelength infrared (SWIR) spectrum is important for many applications. This study explores photodetection using nanocrystalline graphite (NCG) in a suspended, narrow constriction configuration for improved performance. Bowtie constrictions are fabricated in both suspended and substrate‐supported NCG devices, allowing for accurate comparison. It shows that the suspended constriction enhances the bolometric photoresponse and sensor detectivity by several orders of magnitude compared to the substrate‐supported counterparts, attributed to reduced thermalization and electric field concentration. The suspended configuration preserves a spectrally flat photoresponse while reducing operating voltage through a tailored NCG layer thickness. Chromatic aberration‐corrected photocurrent spectroscopy is used to measure the photoresponse from 1100 to 1700 nm, and diffraction‐limited hyperspectral photocurrent imaging is conducted to measure the local photocurrent generation across the device. Bolometric and photo‐thermoelectric currents are restricted to the suspended central constriction due to electric field concentration and thermal decoupling and the direction of the photocurrents within the sensor is revealed. The experimental data is complemented by simulations of the light absorption and the electric field distribution. This work indicates the importance of geometry and thermal decoupling for boosting device performance, offering promising prospects for sensitive and low‐power NCG‐based photodetectors in the NIR‐SWIR range.
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Ren, Haoran, Jaehyuck Jang, Chenhao Li, Andreas Aigner, Malte Plidschun, Jisoo Kim, Junsuk Rho, Markus A. Schmidt y Stefan A. Maier. "An achromatic metafiber for focusing and imaging across the entire telecommunication range". Nature Communications 13, n.º 1 (19 de julio de 2022). http://dx.doi.org/10.1038/s41467-022-31902-3.
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AbstractDispersion engineering is essential to the performance of most modern optical systems including fiber-optic devices. Even though the chromatic dispersion of a meter-scale single-mode fiber used for endoscopic applications is negligible, optical lenses located on the fiber end face for optical focusing and imaging suffer from strong chromatic aberration. Here we present the design and nanoprinting of a 3D achromatic diffractive metalens on the end face of a single-mode fiber, capable of performing achromatic and polarization-insensitive focusing across the entire near-infrared telecommunication wavelength band ranging from 1.25 to 1.65 µm. This represents the whole single-mode domain of commercially used fibers. The unlocked height degree of freedom in a 3D nanopillar meta-atom largely increases the upper bound of the time-bandwidth product of an achromatic metalens up to 21.34, leading to a wide group delay modulation range spanning from −8 to 14 fs. Furthermore, we demonstrate the use of our compact and flexible achromatic metafiber for fiber-optic confocal imaging, capable of creating in-focus sharp images under broadband light illumination. These results may unleash the full potential of fiber meta-optics for widespread applications including hyperspectral endoscopic imaging, femtosecond laser-assisted treatment, deep tissue imaging, wavelength-multiplexing fiber-optic communications, fiber sensing, and fiber lasers.
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Cheng, Qiang, Shervin Karimkashi, Zeeshan Ahmad, Ossi Kaario, Ville Vuorinen y Martti Larmi. "Hyperspectral image reconstruction from colored natural flame luminosity imaging in a tri-fuel optical engine". Scientific Reports 13, n.º 1 (10 de febrero de 2023). http://dx.doi.org/10.1038/s41598-023-29673-y.
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AbstractThe detection of chemiluminescence from various radicals and molecules in a hydrocarbon flame can provide valuable information on the rate of local heat release, combustion stability, and combustion completeness. In this study, chemiluminescence from the combustion process is detected using a high-speed color camera within the broadband spectrum of visible light. Whereon, a novel hyperspectral reconstruction approach based on the physically plausible spectral reconstruction (PPSR) is employed to reconstruct the spectral chemiluminescence signals from 400 to 700 nm with a resolution of 10 nm to provide 31 different spectral channels. The reconstructed key chemiluminescence signals (e.g., CH*, CH2O*, C2*, and CO2*) from the color images are further analyzed to characterize the chemical kinetics and combustion processes under engine conditions. The spectral chemiluminescence evolution with engine crank angle is identified to comprehend the effect of H2 fraction on flame characteristics and combustion kinetics. Additionally, in this study, a detailed kinetic mechanism is adopted to deepen the theoretical understanding and describe the spectral chemiluminescence from H2/CH4 and H2/CH4/n-dodecane flames at relevant conditions for various species including OH*, CH*, C2*, and CO2*. The results indicate that the PPSR is an adequately reliable approach to reconstructing spectral wavelengths based on chemiluminescence signals from the color images, which can potentially provide qualitative information about the evolution of various species during combustion. Here, the reconstructed chemiluminescence images show less than 1% errors compared to the raw images in red, green, and blue channels. Furthermore, the reconstructed chemiluminescence trends of CH*, CH2O*, C2*, and CO2* show a good agreement with the detailed kinetics 0D simulation.
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Li, Yanhao, Xiong Jiang, Yimu Chen, Yuhan Wang, Yunkai Wu, De Yu, Kaiyang Wang, Sai Bai, Shumin Xiao y Qinghai Song. "A platform for integrated spectrometers based on solution-processable semiconductors". Light: Science & Applications 12, n.º 1 (26 de julio de 2023). http://dx.doi.org/10.1038/s41377-023-01231-1.
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AbstractAcquiring real-time spectral information in point-of-care diagnosis, internet-of-thing, and other lab-on-chip applications require spectrometers with hetero-integration capability and miniaturized feature. Compared to conventional semiconductors integrated by heteroepitaxy, solution-processable semiconductors provide a much-flexible integration platform due to their solution-processability, and, therefore, more suitable for the multi-material integrated system. However, solution-processable semiconductors are usually incompatible with the micro-fabrication processes. This work proposes a facile and universal platform to fabricate integrated spectrometers with semiconductor substitutability by unprecedently involving the conjugated mode of the bound states in the continuum (conjugated-BIC) photonics. Specifically, exploiting the conjugated-BIC photonics, which remains unexplored in conventional lasing studies, renders the broadband photodiodes with ultra-narrowband detection ability, detection wavelength tunability, and on-chip integration ability while ensuring the device performance. Spectrometers based on these ultra-narrowband photodiode arrays exhibit high spectral resolution and wide/tunable spectral bandwidth. The fabrication processes are compatible with solution-processable semiconductors photodiodes like perovskites and quantum dots, which can be potentially extended to conventional semiconductors. Signals from the spectrometers directly constitute the incident spectra without being computation-intensive, latency-sensitive, and error-intolerant. As an example, the integrated spectrometers based on perovskite photodiodes are capable of realizing narrowband/broadband light reconstruction and in-situ hyperspectral imaging.
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Zhang, Min, Peipei Dang, Yujia Wan, Yingsheng Wang, Zixun Zeng, Dongjie Liu, Qianqian Zhang, Guogang Li y Jun Lin. "Tailoring Ultra‐Wide Visible‐NIR Luminescence by Ce3+/Cr3+/Yb3+‐alloying Sc‐Based Oxides for Multifunctional Optical Applications". Advanced Optical Materials, 28 de enero de 2024. http://dx.doi.org/10.1002/adom.202302941.
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AbstractVisible‐to‐near‐infrared (VIS‐NIR) luminescent materials are in great demand in the field of non‐destructive testing such as component determination and hyperspectral imaging. Although Cr3+‐activated phosphors are widely reported, controllable tailoring ultra‐wide VIS‐NIR luminescence excited by blue light is still a challenge. The strategies of cationic substitution and energy transfers are effective for adjusting the luminescence of Cr3+‐activated phosphors. In this work, a series of Cr3+‐doped Sc‐based solid solution phosphors (Ba3‐mSrmSc4O9:Cr3+) are reported. Under the excitation of blue light, these phosphors exhibit broadband emission due to the different luminescence centers induced by Cr3+ occupying different cationic sites. Because of the weaker crystal field strength, Cr3+ realizes a broadband emission with a longer peak position (λem = 820 nm) and broader full width at half maximum (FWHM≈182 nm) in Ba2SrSc4O9. Furthermore, Ce3+/Yb3+ ions are introduced into Ba2SrSc4O9:Cr3+, achieving an ultra‐wide VIS‐NIR luminescence (460–1200 nm) by the Ce3+→Cr3+→Yb3+ multiple energy transfers. Designing energy transfers is beneficial to improve the quantum efficiency and weaken the thermal quenching. Finally, the NIR phosphor‐converted light‐emitting diode (pc‐LED) fabricated by Ba2SrSc4O9:Cr3+ demonstrates great potential in night‐vision and water component detection. This work provides an effective design idea for controllable tailoring ultra‐wide VIS‐NIR luminescence by chemical substitution and energy transfer.
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Mahmoud, Alaaeldin y Yasser H. El-Sharkawy. "Delineation and detection of breast cancer using novel label-free fluorescence". BMC Medical Imaging 23, n.º 1 (16 de septiembre de 2023). http://dx.doi.org/10.1186/s12880-023-01095-2.
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Abstract Background Accurate diagnosis of breast cancer (BC) plays a crucial role in clinical pathology analysis and ensuring precise surgical margins to prevent recurrence. Methods Laser-induced fluorescence (LIF) technology offers high sensitivity to tissue biochemistry, making it a potential tool for noninvasive BC identification. In this study, we utilized hyperspectral (HS) imaging data of stimulated BC specimens to detect malignancies based on altered fluorescence characteristics compared to normal tissue. Initially, we employed a HS camera and broadband spectrum light to assess the absorbance of BC samples. Notably, significant absorbance differences were observed in the 440–460 nm wavelength range. Subsequently, we developed a specialized LIF system for BC detection, utilizing a low-power blue laser source at 450 nm wavelength for ten BC samples. Results Our findings revealed that the fluorescence distribution of breast specimens, which carries molecular-scale structural information, serves as an effective marker for identifying breast tumors. Specifically, the emission at 561 nm exhibited the greatest variation in fluorescence signal intensity for both tumor and normal tissue, serving as an optical predictive biomarker. To enhance BC identification, we propose an advanced image classification technique that combines image segmentation using contour mapping and K-means clustering (K-mc, K = 8) for HS emission image data analysis. Conclusions This exploratory work presents a potential avenue for improving "in-vivo" disease characterization using optical technology, specifically our LIF technique combined with the advanced K-mc approach, facilitating early tumor diagnosis in BC.
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Chung, Taerin, Hao Wang y Haogang Cai. "Dielectric metasurfaces for next-generation optical biosensing: a comparison with plasmonic sensing". Nanotechnology, 23 de junio de 2023. http://dx.doi.org/10.1088/1361-6528/ace117.
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Abstract In the past decades, nanophotonic biosensors have been extended from the extensively studied plasmonic platforms to dielectric metasurfaces. Instead of plasmonic resonance, dielectric metasurfaces are based on Mie resonance, which provide comparable sensitivity with superior resonance bandwidth, Q factor, and figure-of-merit. Although the plasmonic photothermal effect is beneficial in many biomedical applications, it is a fundamental limitation for biosensing. Dielectric metasurfaces solve the Ohmic loss and heating problems, providing better repeatability, stability, and bio-compatibility. We review the high-Q resonances based on various physical phenomena tailored by meta-atom geometric designs, and compare dielectric and plasmonic metasurfaces in refractometric, surface-enhanced, and chirality sensing for various biomedical and diagnostic applications. Departing from conventional spectral shift measurement using spectrometers, imaging-based and spectrometer-less biosensing are highlighted, including single-wavelength refractometric barcoding, surface-enhanced molecular fingerprinting, and integrated visual reporting. These unique modalities enabled by dielectric metasurfaces point to two important research directions. On the one hand, hyperspectral imaging provides massive information for smart data processing, which not only achieve better biomolecular sensing performance than conventional ensemble averaging, but also enable real-time monitoring of cellular or microbial behaviour in physiological conditions. On the other hand, a single metasurface can integrate both functions of sensing and optical output engineering, using single-wavelength or broadband light sources, which provides simple, fast, compact and cost-effective solutions. Finally, we provide perspectives in future development on metasurface materials, configurations, nanofabrication, surface modification and system integration, towards next-generation optical biosensing for ultra-sensitive, portable/wearable, lab-on-a-chip, point-of-care, multiplexed and scalable applications.