Letteratura scientifica selezionata sul tema "IR hyperspectral imaging"

The accurate determination of the quality parameters of crops requires a spectral range from 400&amp;thinsp;nm to 2500&amp;thinsp;nm (Kawamura et al., 2010, Thenkabail et al., 2002). Presently the hyperspectral imaging systems that cover this wavelength range consist of several separate hyperspectral imagers and the system weight is from 5 to 15&amp;thinsp;kg. In addition the cost of the Short Wave Infrared (SWIR) cameras is high (~&amp;thinsp;50&amp;thinsp;k€). VTT has previously developed compact hyperspectral imagers for drones and Cubesats for Visible and Very near Infrared (VNIR) spectral ranges (Saari et al., 2013, Mannila et al., 2013, Näsilä et al., 2016). Recently VTT has started to develop a hyperspectral imaging system that will enable imaging simultaneously in the Visible, VNIR, and SWIR spectral bands. The system can be operated from a drone, on a camera stand, or attached to a tractor. The targeted main applications of the DroneKnowledge hyperspectral system are grass, peas, and cereals. In this paper the characteristics of the built system are shortly described. The system was used for spectral measurements of wheat, several grass species and pea plants fixed to the camera mount in the test fields in Southern Finland and in the green house. The wheat, grass and pea field measurements were also carried out using the system mounted on the tractor. The work is part of the Finnish nationally funded <q>DroneKnowledge – Towards knowledge based export of small UAS remote sensing technology</q> project.

Hyperspectral microscopy is an imaging technique that provides spectroscopic information with high spatial resolution. When applied in the relevant wavelength region, such as in the infrared (IR), it can reveal a rich spectral fingerprint across different regions of a sample. Challenges associated with low efficiency and high cost of IR light sources and detector arrays have limited its broad adoption. Here, we introduce a new approach to IR hyperspectral microscopy, where the IR spectral map is obtained with off-the-shelf components built for visible light. The method is based on the nonlinear interference of correlated photons generated via parametric down-conversion. In this proof-of-concept we demonstrate the chemical mapping of a patterned sample, where different areas have distinctive IR spectroscopic fingerprints. The method provides a wide field of view, fast readout, and negligible heat delivered to the sample, which opens prospects for its further development for applications in material and biological studies.

Quantification of gaseous emission fluxes from volcanoes can yield valuable insights on processes occurring in the Earth’s interior as part of hazard monitoring. It is also an important task in the framework of climate change, in order to refine estimates of natural emissions. Passive open-path UltraViolet (UV) scattered observation by UV camera allows the imaging of volcanic plumes and evaluation of sulfur dioxide (SO2) fluxes at high temporal resolution during daytime. Another technique of imaging is now available in the InfraRed (IR) spectral domain. Infrared hyperspectral imagers have the potential to overcome the boundary of daytime sampling of the UV, providing measurements also during the night and giving access simultaneously to additional relevant gas species. In this context the IMAGETNA campaign of measurements took place at Mt Etna (Italy) in June 2015. Three different IR imagers (commercial and under developments) were deployed, together with a Fourier Transform InfraRed spectrometer (FTIR) instrument, a UV camera, a Long Wavelength InfraRed (LWIR) camera and a radiometer. We present preliminary results obtained by the two IR cameras under development, and then the IR hyperspectral imager results, coming from full physics retrieval, are compared to those of the UV camera. The comparison points out an underestimation of the SO2 Slant Column Densities (SCD) of the UV camera by a factor of 3.6. The detailed study of the retrieved SO2 SCD highlights the promising application of IR imaging in volcanology for remotely volcanic plume gas measurements. It also provides a way to investigate uncertainties in the SO2 SCD imaging in the UV and the IR.

A high performance hyperspectral imager with high light throughput suitable for microscopy and analytical imaging was built and tested. The imager utilizes phenomenon of optical activity. The new technique provides a continuous spectral range of several hundreds of nanometers starting in deep UV. Similar spectral range starting in the near IR is also achievable.A performance of a low cost implementation of the new technology is presented. The imager has a form of a microscope adaptor, which is inserted between the microscope and a low-cost 8-bit CCD camera. The resulting instrument is simple, robust, and highly compact. The imager module is placed in-line to the microscope imaging system and does not introduce observable image aberrations. Advantageously, the imager is transparent to conventional imaging operations, thus with the imager in-place there is no need for reconfiguration of the microscope to switch between conventional and hyperspectral video/digital imaging modes.The presented spectral imager answers the need for a practical, sensitive, compact, and affordable imaging spectrometer. The instrument is well suited for a broad range of applications requiring rapid parallel acquisition of highly resolved concurrent spatial and spectral information such as high throughput screening, biochip analysis, remote sensing or nondestructive semiconductor testing.

The work presented in this paper is part of a wider research project, which aims at documenting and analyzing stained glass windows by means of hyperspectral imaging. This technique shares some similarities with UV-VIS-IR spectroscopy, as they both provide spectral information; however, spectral imaging has the additional advantage of providing spatial information, since a spectrum can be collected in each pixel of the image. Compared to UV-VIS-IR spectroscopy, spectral imaging has rarely been used for the investigation of stained glass windows. One of the objectives of this paper is, thus, to compare the performance of these two instruments to validate the results of hyperspectral imaging. The second objective is to evaluate the potential of analyzing colored-glass pieces in reflectance modality and compare the results with those obtained in transmittance, in order to highlight the differences and similarities between the two approaches. The geometry of the systems and the backing material for the glass, as well as the characteristics of the glass pieces, are discussed. L*a*b* values obtained from the spectra, as well as the calculated color difference ΔE00, are provided, to show the degree of agreement between the instruments and the two measurement modalities.

Polariscopy is demonstrated using hyperspectral imaging with a focal plane array (FPA) detector in the infrared (IR) spectral region under illumination by thermal and synchrotron light sources. FPA Fourier-transform IR (FTIR) imaging microspectroscopy is useful for monitoring real time changes at specific absorption bands when combined with a high brightness synchrotron source. In this study, several types of samples with unique structural motifs were selected and used for assessing the capability of polariscopy under this FPA-FTIR imaging technique. It was shown that the time required for polariscopy at IR wavelengths can be substantially reduced by the FPA-FTIR imaging approach. By using natural and laser fabricated polymers with sub-wavelength features, alignment of absorbing molecular dipoles and higher order patterns (laser fabricated structures) were revealed. Spectral polariscopy at the absorption peaks can reveal the orientation of sub-wavelength patterns (even when they are not spatially resolved) or the orientation of the absorbing dipoles.

Les astéroïdes primitifs sont des petits corps qui ont relativement peu évolué depuis leur formation. Ils nous renseignent sur la composition chimique du système solaire primitif et son évolution jusqu’à aujourd’hui. Avant les années 2020, les seuls potentiels analogues de ces objets dont nous disposions pour des analyses en laboratoire étaient les chondrites carbonées (CCs). Mais le lien entre les CCs et leurs corps parents astéroïdaux n'est pas encore clair, et la composition primitive des CCs est partiellement altérée par l’interaction avec l’atmosphère terrestre. C’est pourquoi dans les années 2010, deux missions spatiales ont observé et collecté des échantillons de la surface d’astéroïdes primitifs : ils représentent la première analyse en laboratoire de fragments représentatifs de leur corps parents. L’astéroïde géocroiseur de type C, (162173) Ryugu, a été la cible de la mission Hayabusa2 (JAXA). La sonde a réalisé deux collectes, prélevant des échantillons de la surface et de la sous-surface excavée par un impacteur artificiel. En décembre 2020, la capsule scellée contenant 5.4 g d’échantillons est revenue sur Terre et a été ouverte dans la Curation Facility (Sagamihara, Japon), un complexe contenant un ensemble d’enceintes propres pour réaliser une première analyse des grains, sans les exposer à l’atmosphère et en préservant leur intégrité. L’objectif de ma thèse a été de caractériser la composition des grains de Ryugu pour retracer l’évolution de la matière primitive à différentes étapes de l’histoire du système solaire. Pour cela, j’ai analysé les données acquises par MicrOmega, un imageur hyperspectral proche infrarouge (0.99 – 3.65 μm) installé dans la Curation Facility. MicrOmega permet une analyse de la composition minérale et organique des grains de manière non invasive. J’ai étudié la bande d’absorption à 2.7 μm, caractéristique de la vibration du groupe -OH dans les phyllosilicates des grains. J’ai réalisé une étude statistique sur les variations de position et de profondeur de la bande entre plusieurs centaines de grains millimétriques, qui témoignent une variation de composition des phyllosilicates. Cette analyse suggère qu’une partie des grains du site de collecte de surface ont été exposés à l’altération spatiale, un processus affectant la composition et la microstructure de la surface des corps sans atmosphères. À l’inverse, la totalité des grains provenant de la sous-surface ont subi une très faible exposition à l’environnement spatial. Cette étude montre aussi que les échantillons de Ryugu sont très appauvris en eau (H₂O) par rapport aux chondrites CI malgré leur minéralogie proche, et suggère qu’une partie importante de l’eau des CI pourrait être d’origine terrestre. J’ai ensuite étudié les variations de la forme et de la position de la bande à 2.7 μm à la surface des grains. J’ai montré que l'hétérogénéité spectrale de la surface varie d'un grain à l'autre. Cette variation d'hétérogénéité pourrait être liée à des variations du degré d'altération aqueuse et/ou du degré d'altération spatiale sur des surfaces avec différentes rugosités. Cette étude montre le potentiel de l’imagerie hyperspectrale infrarouge pour détecter des variations dans le contenu en eau entre différents grains, sans biais par l’atmosphère terrestre. Ces travaux apportent une meilleure compréhension de l’évolution physique et chimique de la surface et de la sous-surface proche des astéroïdes primitifs. Ils apportent aussi de nouveaux éléments sur l’altération terrestre des chondrites carbonées, avec une implication sur la quantité d’eau dans les corps parents astéroïdaux des chondrites CI
Primitive asteroids are small bodies that have evolved relatively little since their formation. They contain information about the chemical composition of the early solar system and its evolution up to the present day. Before the 2020s, the only potential analogs of these objects available for laboratory analysis were carbonaceous chondrites (CCs). But the link between CCs and their asteroidal parent bodies is not yet clear, and the primitive composition of CCs is partially altered by interaction with the terrestrial atmosphere. This is why, in the 2010s, two space missions observed and collected samples from the surface of primitive asteroids: they represent the first laboratory study of fragments representing their parent bodies. The C-type near-Earth asteroid (162173) Ryugu, was the target of the Hayabusa2 mission (JAXA). The spacecraft performed two samplings, collecting surface and subsurface samples excavated by an artificial impactor. In December 2020, the sealed capsule containing 5.4g of samples returned to Earth and was opened in the Curation Facility (Sagamihara, Japan), a complex containing a set of clean chambers for carrying out an initial analysis of the grains, preserving their integrity and without exposing them to the terrestrial atmosphere. The aim of my thesis was to characterize the composition of Ryugu samples to retrace the evolution of the primitive matter at different stages in the history of the solar system. Thus, I analysed data acquired by the near-infrared (0.99 – 3.65 μm) hyperspectral microscope MicrOmega, installed in the Curation Facility. MicrOmega enables a non-invasive characterization of the mineral and organic composition of the grains. I studied the 2.7 μm band, characteristic of the vibration of the -OH group in the phyllosilicates of the samples. I carried out a statistical study of the variations in the position and depth of the band between several hundred millimetre-sized grains, which indicate a variation in the composition of the phyllosilicates. This analysis suggests that some of the grains collected at the surface experienced space weathering, a process that affects the composition and microstructure of the surface of airless bodies. Conversely, all the grains from the subsurface have undergone a limited exposure to the space environment. This study also shows that the Ryugu samples are depleted in water (H₂O) compared with CI chondrites, despite their similar mineralogy, and suggests that a significant proportion of the water in the CIs could be of terrestrial origin. I then studied the variations in the shape and position of the 2.7 μm band at the surface of the grains. I showed that the spectral heterogeneity of the surface varies from one grain to another. This variation in heterogeneity could be linked to variations in the degree of aqueous alteration and/or the degree of space weathering on surfaces with different roughnesses. This study shows the potential of infrared hyperspectral imaging to detect variations in the water content between the grains, without any bias by the terrestrial atmosphere. This work provides a better understanding of the physical and chemical evolution of the surface and the near subsurface of primitive asteroids. It also provides new insights on the terrestrial alteration of carbonaceous chondrites, with implications for the quantity of water in the asteroidal parent bodies of CI chondrites

Une nouvelle génération de spectromètres imageurs émerge dans le domaine de l'exploration spatiale par l'ajout d'une dimension supplémentaire de mesure, la dimension angulaire. L'imagerie spectroscopique multi-angulaire est conçue pour fournir une caractérisation plus précise des matériaux planétaires et permet une meilleure séparation des signaux provenant de l'atmosphère et la surface. Le capteur Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) à bord de la sonde Mars Reconnaissance Orbiter est une caméra hyperspectrale qui fonctionne systématiquement dans le mode multi-angulaire depuis l'orbite. Néanmoins, les images multi-angulaires hyperspectrales posent certains problèmes de manipulation, de visualisation et d'analyse en raison de leur taille et de leur complexité. Dans ce cadre, cette thèse propose des algorithmes statistiques et physiques pour analyser les images acquises par l'instrument CRISM de manière efficace et robuste. Premièrement, je propose une chaîne de post-traitement visant à améliorer la qualité radiométrique des données CRISM et à générer des produits améliorés, ces dernières données étant conçues pour permettre une analyse fine de la planète Mars. Deuxièmement, je m'intéresse à la correction atmosphérique des images CRISM en exploitant les capacités multi-angulaires de cet instrument. Un algorithme innovant, à base physique est mis en oeuvre pour compenser les effets atmosphériques afin d'estimer la reflectance de surface. Cette approche est particulièrement utilisée dans cette thèse pour déduire les propriétés photométriques des matériaux qui coexistent dans un site spécifique de Mars, le cratère de Gusev. Troisièmement, j'effectue une comparaison d'une sélection des meilleurs techniques existantes, visant à réaliser une déconvolution spectrale des données acquises par l'instrument CRISM. Ces techniques statistiques se sont avérées utiles lors de l'analyse d'images hyperspectrales de manière non supervisé, c'est a dire, sans aucun a priori sur la scène. Une stratégie originale est proposée pour discriminer les techniques les plus appropriées pour l'exploration de Mars, à partir de données indépendantes provenant d'autres capteurs d'imagerie haute résolution afin de construire une vérité de terrain
New generation of imaging spectrometers are emerging in the field of space exploration by adding an additional view of measurement, the angular dimension. Multi-angle imaging spectroscopy is conceived to provide a more accurate characterization of planetary materials and a higher success in separating the signals coming from the atmosphere and the surface. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter is a hyperspectral camera that operates systematically in multi-angle mode from space. Nonetheless, multi-angle hyperspectral images are related to problems of manipulation, visualization and analysis because of their size and complexity. In this framework, this PhD thesis proposes robust statistical and physical algorithms to analyze images acquired by the CRISM instrument in an efficient manner. First, I propose a tailor-made data pipeline aimed at improving the radiometric quality of CRISM data and generating advanced products, the latter data being devised to perform fine analysis of the planet Mars. Second, I address the atmospheric correction of CRISM imagery by exploiting the multi-angle capabilities of this instrument. An innovative physically-based algorithm compensating for atmospheric effects is put forward in order to retrieve surface reflectance. This approach is particularly used in this thesis to infer the photometric properties of the materials coexisting in a specific site of Mars, the Gusev crater. Third, I perform an intercomparison of a selection of state-of-the-art techniques aimed at performing spectral unmixing of hyperspectral data acquired by the CRISM instrument. These statistical techniques are proved to be useful when analyzing hyperspectral images in an unsupervised manner, that is, without any a priori on the scene. An original strategy is proposed to discriminate the most suitable techniques for the exploration of Mars based on ground truth data built from independent high resolution imagery

Lo scopo del lavoro di ricerca è stato lo sviluppo di applicazioni per il recupero e il riciclo dei materiali, partendo da approcci classici di separazione e caratterizzazione fino all’utilizzo di strumenti innovativi per il riconoscimento e il monitoraggio dei materiali attraverso applicazioni di imaging iperspettrale. Uno degli obiettivi della ricerca, è stato quello di utilizzare sistemi di acquisizione HyperSpectral Imaging (HSI) per ottenere informazioni utili per l’esplorazione dei dati, applicando metodi di analisi multivariata in modalità supervisionata; pertanto l’applicazione di un approccio ingegneristico trasversale ha permesso di sviluppare dei sistemi online per il recupero e il riciclo di scarti eterogenei, che possono trovare ampio spazio in future soluzioni di tipo industriale. La prima parte di questo studio ha riguardato la caratterizzazione e la valorizzazione di uno scarto proveniente da un impianto di smistamento di rifiuti plastici indifferenziati urbani, dividendo il processo in fasi principali, come l’identificazione dei polimeri attraverso la classica spettroscopia FT-IR, il riconoscimento dei polimeri attraverso l’analisi HSI, lo sviluppo di un processo di separazione sperimentale e la certificazione del campione in Combustibile Solido Secondario (CSS) di qualità. È stato utilizzato un approccio di tipo analitico, basato sull’analisi HSI, per eseguire una caratterizzazione dei rifiuti plastici post-imballaggio, finalizzato all’identificazione dei polimeri plastici che costituiva il campione rappresentativo; l’applicazione di questa tecnica è particolarmente adatta ad applicazioni di tipo online, con la possibilità di valutare qualitativamente e quantitativamente la presenza dei diversi polimeri che costituiscono il rifiuto. La successiva parte del lavoro, ha visto l'approfondimento della ricerca e lo sviluppo di una metodologia innovativa per il recupero e il riciclo dei rifiuti elettronici a fine vita. I rifiuti elettronici hanno una composizione molto eterogenea, per cui alcuni elementi e componenti sono difficili da individuare e riconoscere, anche per via dello sviluppo sempre crescente di nuove tecnologie e la crescente miniaturizzazione dei componenti che vengono utilizzati. Al fine di migliorare il recupero di materie prime e aumentare il livello di tutela ambientale, una corretta caratterizzazione di questi rifiuti rappresenta il primo e necessario passo per il recupero di metalli preziosi e terre rare.

Quantum imaging with undetected photons allows measuring mid-infrared information with visible or near-infrared silicon-based light detection. We demonstrate a combination of quantum imaging and Fourier-transform spectral analysis for broadband high-resolution mid-infrared hyperspectral imaging.

An imaging algorithm converts conventional polarization-controlled IR hyperspectral data into images of the 3D angles of molecular orientations. The new polarization IR method maps the 3D orientation angles of polymer chains in a PCL film.