74 research outputs found

    Advances in multispectral and hyperspectral imaging for archaeology and art conservation

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    Multispectral imaging has been applied to the field of art conservation and art history since the early 1990s. It is attractive as a noninvasive imaging technique because it is fast and hence capable of imaging large areas of an object giving both spatial and spectral information. This paper gives an overview of the different instrumental designs, image processing techniques and various applications of multispectral and hyperspectral imaging to art conservation, art history and archaeology. Recent advances in the development of remote and versatile multispectral and hyperspectral imaging as well as techniques in pigment identification will be presented. Future prospects including combination of spectral imaging with other noninvasive imaging and analytical techniques will be discussed

    Remote sensing of strong emotions using electro-optical imaging technique

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    ©Cranfield UniversityThis thesis reports a summary of the PhD programme for the assessment of person‘s emotional anxiety using Electro-optical technology. The thesis focuses mainly on the understanding of fundamental properties of physiological responses to emotional anxiety and how they can be captured by using Electro-optical (EO) imaging methods such as hyperspectral imaging (HSI) and thermal imaging (TI) techniques. The thesis summarises three main areas of work that have been undertaken by the author in the programme: (a) Experimental set up including HSI system and data acquisition software design and implementation, (b) fundamental understanding of physiological responses to emotional anxiety from the EO perspective and (c) the development of a novel remote sensing technique for the assessment of emotions without the requirement of base line information. One of our main results is to provide evidence to prove that the mean temperature in the periorbital region remains the same within 0.2°C during emotional anxiety. Furthermore, we have shown that it is the high temperature pixels within the periorbital, which increases in numbers by a huge amount after 2 minutes of the onset of anxiety. We have also developed techniques to allow the assessment anxiety without the need of base line information. The method has been tested using a sample size of about 40 subjects, and achieved promising result. Technologies for the remote sensing of heart beat rate has been in great demand, this study also involves the development of heart beat detection using TI system. Moreover, we have also attempted for the first time to sense glucose concentration from the blood sample in-vivo using HSI technique remotely

    Active spectral imaging

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    With the ability to image a scene in tens to hundreds of spectral bands, multispectral and hyperspectral imaging sensors have become powerful tools for remote sensing. However, spectral imaging systems that operate at visible through nearinfrared wavelengths typically rely on solar illumination. This reliance gives rise to a number of limitations, particularly with regard to military applications. Actively illuminating the scene of interest offers a way to address these limitations while providing additional advantages. We have been exploring the benefits of using active illumination with spectral imaging systems for a variety of applications. Our laboratory setup includes multispectral and hyperspectral sensors that are used in conjunction with several laser illumination sources, including a broadband white-light laser. We have applied active spectral imaging to the detection of various types of military targets, such as inert land mines and camouflage paints and fabrics, using a combination of spectral reflectance, fluorescence, and polarization measurements. The sensor systems have been operated under a variety of conditions, both in the laboratory and outdoors, during the day and at night. Laboratory and outdoor tests have shown that using an active illumination source can improve target-detection performance while reducing false-alarm rates for both multispectral and hyperspectral imagers

    Snapshot hyperspectral imaging : near-infrared image replicating imaging spectrometer and achromatisation of Wollaston prisms

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    Conventional hyperspectral imaging (HSI) techniques are time-sequential and rely on temporal scanning to capture hyperspectral images. This temporal constraint can limit the application of HSI to static scenes and platforms, where transient and dynamic events are not expected during data capture. The Near-Infrared Image Replicating Imaging Spectrometer (N-IRIS) sensor described in this thesis enables snapshot HSI in the short-wave infrared (SWIR), without the requirement for scanning and operates without rejection in polarised light. It operates in eight wavebands from 1.1μm to 1.7μm with a 2.0° diagonal field-of-view. N-IRIS produces spectral images directly, without the need for prior topographic or image reconstruction. Additional benefits include compactness, robustness, static operation, lower processing overheads, higher signal-to-noise ratio and higher optical throughput with respect to other HSI snapshot sensors generally. This thesis covers the IRIS design process from theoretical concepts to quantitative modelling, culminating in the N-IRIS prototype designed for SWIR imaging. This effort formed the logical step in advancing from peer efforts, which focussed upon the visible wavelengths. After acceptance testing to verify optical parameters, empirical laboratory trials were carried out. This testing focussed on discriminating between common materials within a controlled environment as proof-of-concept. Significance tests were used to provide an initial test of N-IRIS capability in distinguishing materials with respect to using a conventional SWIR broadband sensor. Motivated by the design and assembly of a cost-effective visible IRIS, an innovative solution was developed for the problem of chromatic variation in the splitting angle (CVSA) of Wollaston prisms. CVSA introduces spectral blurring of images. Analytical theory is presented and is illustrated with an example N-IRIS application where a sixfold reduction in dispersion is achieved for wavelengths in the region 400nm to 1.7μm, although the principle is applicable from ultraviolet to thermal-IR wavelengths. Experimental proof of concept is demonstrated and the spectral smearing of an achromatised N-IRIS is shown to be reduced by an order of magnitude. These achromatised prisms can provide benefits to areas beyond hyperspectral imaging, such as microscopy, laser pulse control and spectrometry

    RESPONSE FUNCTION CHARACTERIZATION AND DECONVOLUTION IN HYPERSPECTRAL IMAGING

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    Hiperspektralno slikanje je neinvazivna slikovna tehnika, ki se vse bolj uveljavlja na številnih različnih področjih v biomedicini, npr. za diagnosticiranje raka in zgodnje odkrivanje zobnega kariesa, kakor tudi v farmaciji, prehranski industriji, agronomiji, raziskovanju zemeljskega površja in astronomiji. Rezultat hiperspektralnega slikanja je slika vzorca pri različnih valovnih dolžinah, s čimer je na voljo spektralna informacija o vzorcu, kakor tudi njena prostorska porazdelitev ter tako predstavlja združitev spektroskopije in strojnega vida. Za zajem hiperspektralne slike vzorca je potrebno le-tega navadno osvetliti s širokopasovnim svetilom. Odbito ali povratno sipano svetlobo nato prednja zbiralna leča usmeri na disperzijski element, po prehodu katerega se ponovno zbere in pošlje na svetlobno tipalo. Lastnosti disperzijskega elementa in prednje leče v kombinaciji z neporavnanostjo osi optičnih gradnikov povzročijo spremenljiva geometrijska popačenja in megljenje v hiperspektralnih slikah, ki lahko močno vplivajo na kakovost zajetih slik. Glede na način zajemanja hiperspektralnih slik delimo hiperspektralne sisteme v štiri skupine: točkovno spektralne, enorazsežno prostorske, dvorazsežno prostorske in trirazsežne. Pri sistemih za točkovno spektralno zajemanje in za enorazsežno prostorsko zajemanje zajamemo celotno hiperspektralno sliko z zaporednim zajemanjem spektrov v eni točki oziroma v eni prostorski razsežnosti. Sistemi za dvorazsežno prostorsko zajemanje omogočajo zajem dvorazsežne slike pri izbrani valovni dolžini, pri čemer nam izgradnjo celotne hiperspektralne slike omogoča valovno nastavljivi optični gradnik. Sistemi za trirazsežno zajemanje pa omogočajo hkraten zajem prostorske kakor tudi spektralne informacije. Matematično lahko zajem hiperspektralne slike opišemo kot konvolucijo med nepopačeno sliko vzorca ter prenosno funkcijo hiperspektralnega sistema. Natančna ocena prenosne funkcije nam omogoča, da z dekonvolucijo iz zajete slike vzorca izločimo vpliv prenosne funkcije hiperspektralnega sistema. Iz teorije spremenljivih linearnih sistemov vemo, da lahko prenosno funkcijo sistema določimo z opazovanjem odziva sistema na ustrezne testne signale v vseh stanjih sistema. V doktorski disertaciji bomo predstavili postopke, ki omogočajo uporabniku hiperspektralnega sistema njegovo enostavno in hitro karakterizacijo. Rezultati karakterizacije se nato lahko uporabijo v postopku obnove slik z dekonvolucijo za zmanjšanje geometrijskih popačenj in megljenja v zajetih hiperspektralnih slikah. Pomembnost karakterizacije hiperspektralnih sistemov je bila prepoznana na področju daljinskega zaznavanja, kjer je bilo v zadnjih letih objavljenih več raziskav, vendar pa nobena od njih ne uporabi rezultatov karakterizacije za hkratno zmanjšanje geometrijskih popačenj in megljenja kot posledice popačenj hiperspektralnih sistemov. Poleg tega so omenjene raziskave obravnavale karakterizacijo hiperspektralnih sistemov za daljinsko zaznavanje, pri katerih je fokusna ravnina nastavljena na neskončno oddaljenost, kar pa navadno ne drži za laboratorijske hiperspektralne sisteme. Večina postopkov za karakterizacijo le-teh obravnava le sivinsko kalibracijo, ki nam omogoča izločitev vpliva svetila in občutljivosti svetlobnega tipala, ne pa tudi vpliva preostalih optičnih gradnikov, ki v zajete slike vnašajo geometrijska popačenja in megljenje. V prvem delu doktorske disertacije obravnavamo razvoj celovitega postopka za obnovo hiperspektralnih slik, zajetih s sistemom za enorazsežno prostorsko zajemanje, pri čemer nadgradimo obstoječe postopke za karakterizacijo in jih razširimo v smislu uporabe rezultatov v dekonvoluciji. V drugem delu pa predlagamo in ovrednotimo kalibracijski objekt, ki nam omogoča enostavno neposredno meritev trirazsežne prenosne funkcije hiperspektralnih sistemov.Hyperspectral imaging is an emerging non-invasive modality that has shown great potential in numerous biomedical applications such as cancer diagnosis, burn depth assessment, and early caries detection, as well as in other fields including pharmacy, food industry, agriculture, remote sensing and astronomy. Hyperspectral imaging systems produce a stack of images acquired at many different wavelengths that provide information about the spectral content of the object and its spatial distribution. Acquisition of hyperspectral images typically involves illumination of the observed object by a broadband light source. The diffused or transmitted light is collected by the front lens and directed onto a dispersive element from where it is refocused onto the detector array. Properties of the dispersive element, front lens and misalignments of the optical elements contribute to positionally variant displacements and blur that can significantly degrade the overall quality of the acquired images. In general, hyperspectral images can be acquired in four different ways: whiskbroom, pushbroom, staring and snapshot configuration. In the case of whiskbroom and pushbroom systems, hyperspectral image is formed by spatially scanning the object in each pixel or line of pixels, respectively. Staring systems conduct a spectral scan of the object, acquiring 2D images at the selected spectral bands. On the other hand, snapshot systems allow simultaneous acquisition of the spatial and spectral information. The image formation process can be mathematically formulated by convolution of the observed scene with the response function, that models the aberrations introduced by the hyperspectral imaging system. Having an accurate estimate of the response function, deconvolution can invert the image formation process, obtaining an undistorted high-resolution estimate of the observed scene. From the theory of linear systems it is well known that the system can be fully characterized if the response to a standard test function is known in each state of the system. The main goal of this thesis is to provide the users of hyperspectral imaging systems with novel methods and tools to accurately measure and identify the response function that can be employed in subsequent deconvolution-based image restoration, reducing the effects of displacements and blur in the acquired images. The importance of hyperspectral imaging system characterization is recognized in the field of remote sensing where several studies have been published in recent years. However, it is overlooked that image deconvolution could be used to simultaneously reduce the effect of displacements and blur arising from the optical system. Furthermore, the proposed characterization methods require the lens working distance to be set to infinity, which is rarely the case in laboratory applications of hyperspectral imaging systems. Finally, in most of the laboratory hyperspectral imaging systems merely a flat-field correction is applied to eliminate the effect of illumination non-uniformity and sensor sensitivity, fully neglecting the effects of system optics on the acquired images. In the first part of this thesis, we devise a complete restoration procedure for pushbroom hyperspectral imaging systems, refining the previous work on the characterization of laboratory pushbroom hyperspectral imaging systems in a way that allows efficient deconvolution based image restoration. In the second part of the thesis, we propose and analyze a novel calibration target that offers a simple solution for direct and highly accurate 3D response function measurements of diffraction limited hyperspectral imaging systems

    Application-Dependent Wavelength Selection For Hyperspectral Imaging Technologies

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    Hyperspectral imaging has proven to provide benefits in numerous application domains, including agriculture, biomedicine, remote sensing, and food quality management. Unlike standard color imagery composed of these broad wavelength bands, hyperspectral images are collected over numerous (possibly hundreds) of narrow wavelength bands, thereby offering vastly more information content than standard imagery. It is this higher information content which enables improved performance in complex classification and regression tasks. However, this successful technology is not without its disadvantages which include high cost, slow data capture, high data storage requirements, and computational complexity. This research seeks to overcome these disadvantages through the development of algorithms and methods to enable the benefits of hyperspectral imaging in inexpensive portable devices that collect spectral data at only a handful (i.e., 5-7) of wavelengths specifically selected for the application of interest.This dissertation focuses on two applications of practical interest: fish fillet species classification for the prevention of food fraud and tissue oxygenation estimation for wound monitoring. Genetic algorithm, self-organizing map, and simulated annealing approaches for wavelength selection are investigated for the first application, combined with common machine learning classifiers for species classification. The simulated annealing approach for wavelength selection is carried over to the wound monitoring application and is combined with the Extended Modified Lambert-Beer law, a tissue oxygenation method that has proven to be robust to differences in melanin concentrations. Analyses for this second application included spectral convolutions to represent data collection with the envisioned inexpensive portable devices. Results of this research showed that high species classification accuracy (\u3e 90%) and low tissue oxygenation error (\u3c 1%) is achievable with just 5-7 selected wavelengths. Furthermore, the proposed wavelength selection and estimation algorithms for the wound monitoring application were found to be robust to variations in the peak wavelength and relatively wide bandwidths of the types of LEDs that may be featured in the designs of such devices

    Multiscale and multispectral characterization of mineralogy with the ExoMars 2020 rover remote sensing payload

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    This work was supported by the UK Space Agency (ST/P001297/1 and ST/P001394/1). Cousins also acknowledges the Royal Society of Edinburgh for funding.In 2020, the European Space Agency and Roscosmos will launch the ExoMars rover, with the scientific objective to detect evidence of life within the martian surface via the deployment of a 2 meter drill. The ExoMars Pasteur payload contains several imaging and spectroscopic instruments key to this objective: the Panoramic Camera (PanCam), Infrared Spectrometer for ExoMars (ISEM), and Close‐UP Imager (CLUPI). These instruments are able to collect data at a variety of spatial (sub‐mm to decimeter) and spectral (3.3 to 120 nm) resolutions across the 440 to 3300 nm wavelength range and collectively will form a picture of the geological and morphological characteristics of the surface terrain surrounding the rover. We deployed emulators of this instrument suite at terrestrial analog sites that formed in a range of aqueous environments to test their ability to detect and characterize science targets. We find that the emulator suite is able to effectively detect, characterize, and refine the compositions of multiple targets at working distances spanning from 2‐18 m. We report on: (i) the detection of hydrothermal alteration minerals including Fe‐smectites and gypsum from basaltic substrates, (ii) the detection of late‐stage diagenetic gypsum veins embedded in exposures of sedimentary mudstone, (iii) multispectral evidence of compositional differences detected from fossiliferous mudstones, and (iv) approaches to cross‐referencing multi‐scale and multi‐resolution data. These findings aid in the development of data products and analysis toolkits in advance of the ExoMars rover mission.Publisher PDFPeer reviewe

    Summaries of the Third Annual JPL Airborne Geoscience Workshop. Volume 1: AVIRIS Workshop

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    This publication contains the preliminary agenda and summaries for the Third Annual JPL Airborne Geoscience Workshop, held at the Jet Propulsion Laboratory, Pasadena, California, on 1-5 June 1992. This main workshop is divided into three smaller workshops as follows: (1) the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) workshop, on June 1 and 2; (2) the Thermal Infrared Multispectral Scanner (TIMS) workshop, on June 3; and (3) the Airborne Synthetic Aperture Radar (AIRSAR) workshop, on June 4 and 5. The summaries are contained in Volumes 1, 2, and 3, respectively
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