Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Sensations of color show a strong correlation with reflectance, even though the amount of visible light reaching the eye depends on the product of reflectance and illumination. The visual system must achieve this remarkable result by a scheme that does not measure flux. Such a scheme is described as the basis of retinex theory. This theory assumes that there are three independent cone systems, each starting with a set of receptors peaking, respectively, in the long-, middle-, and short-wavelength regions of the visible spectrum. Each system forms a separate image of the world in terms of lightness that shows a strong correlation with reflectance within its particular band of wavelengths. These images are not mixed, but rather are compared to generate color sensations. The problem then becomes how the lightness of areas in these separate images can be independent of flux. This article describes the mathematics of a lightness scheme that generates lightness numbers, the biologic correlate of reflectance, independent of the flux from objects <s> BIB001 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Imaging spectrometry, a new technique for the remote sensing of the earth, is now technically feasible from aircraft and spacecraft. The initial results show that remote, direct identification of surface materials on a picture-element basis can be accomplished by proper sampling of absorption features in the reflectance spectrum. The airborne and spaceborne sensors are capable of acquiring images simultaneously in 100 to 200 contiguous spectral bands. The ability to acquire laboratory-like spectra remotely is a major advance in remote sensing capability. Concomitant advances in computer technology for the reduction and storage of such potentially massive data sets are at hand, and new analytic techniques are being developed to extract the full information content of the data. The emphasis on the deterministic approach to multispectral data analysis as opposed to the statistical approaches used in the past should stimulate the development of new digital image-processing methodologies. <s> BIB002 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> A real-time video imaging system called the imaging burn depth indicator (IBDI) is described; IBDI can discriminate areas of burn wounds expected to heal in three weeks or less from the day of injury from those areas not expected to heal in that time period. The analysis can be performed on or about the third day postburn on debrided burn wounds. The relative diffuse reflectivity of the burn-wound is measured in the red, green, and near-infrared wavelength bands and an algorithm established previously is used to translate this optical data into burn healing probabilities. Over 100 burn wound sites were studied. Burn sites were evaluated on day three postburn by the IBDI and by the attending physician. Overall, the IBDI was found to be more accurate in predicting burn healing than were the attending physicians. > <s> BIB003 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Introduction One of the challenges of Imaging Spectroscopy is the identification, mapping and abundance determination of materials, whether mineral, vegetable, or liquid, given enough spectral range, spedral resolution, signal to noise, and spatial resolution. Many materials show diagnostic absorption features in the visual and near infrared region (0.4 to 2.5 pm) of the spectrum. ‘l’his region is covered by modern imaging spectrometers such as AVIRIS. The challenge is to identi~ the materials from absorption bands in their _ and determine what specific analyses must be done to derive particular parameters of interest, mnging from simply identifying its presence to deriving its abundance, or determining specific chemistry of the material. <s> BIB004 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> However, permission to reprint/republish this material for advertising or promotional purposes or for creating other new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from David Landgrebe and the World Scientific Publishing Company. This work was originally prepared for and appears in Informat ion Process ing for Remote Sens ing , edited by C. H. Chen, published by the World Scientific Publishing Co., Inc., 1060 Main Street, River Edge, NJ 07661, USA (Spring, 1999). In addition to general works such as this one, this book contains sections on Pattern Recognition, SAR Image Processing and Segmentation, Parameter Extraction, Neural Network and Fuzzy Logic Methods, Change Detection, Knowledge-based Methods and Data Fusion, Image Processing Algorithms including wavelet analysis techniques, Image Compression, and Discrimination of Buried Objects. Information Extraction Principles and Methods for Multispectral and Hyperspectral Image Data David Landgrebe School of Electrical & Computer Engineering Purdue University, West Lafayette, IN 47907-1285 Voice: 765-494-3486 Fax: 765-494-3358 landgreb@ecn.purdue.edu <s> BIB005 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> This paper analyzes the feasibility and performance of HSI systems for medical diagnosis as well as for food safety. Illness prevention and early disease detection are key elements for maintaining good health. Health care practitioners worldwide rely on innovative electronic devices to accurately identify disease. Hyperspectral imaging (HSI) is an emerging technique that may provide a less invasive procedure than conventional diagnostic imaging. By analyzing reflected and fluorescent light applied to the human body, a HSI system serves as a diagnostic tool as well as a method for evaluating the effectiveness of applied therapies. The safe supply and production of food is also of paramount importance to public health illness prevention. Although this paper will focus on imaging and spectroscopy in food inspection procedures -- the detection of contaminated food sources -- to ensure food quality, HSI also shows promise in detecting pesticide levels in food production (agriculture.) <s> BIB006 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Spectral imaging technology, which records simultaneously spectral and spatial information about an object, was initially developed for remote sensing and has since been successfully applied to other areas of research. Although relatively new to the field of conservation, this non-invasive method of investigation has already provided promising results in the analysis of paintings and written documents, the characterization of materials and digital documentation. This article reviews the published literature relating to the application of multispectral and hyperspectral imaging for the study and conservation of works of art and presents some new perspectives offered by this innovative and fast-developing technology. <s> BIB007 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Hyperspectral imaging (HSI) is an emerging platform technology that integrates conventional imaging and spectroscopy to attain both spatial and spectral information from an object. Although HSI was originally developed for remote sensing, it has recently emerged as a powerful process analytical tool for non-destructive food analysis. This paper provides an introduction to hyperspectral imaging: HSI equipment, image acquisition and processing are described; current limitations and likely future applications are discussed. In addition, recent advances in the application of HSI to food safety and quality assessment are reviewed, such as contaminant detection, defect identification, constituent analysis and quality evaluation. <s> BIB008 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Hyperspectral imaging describes the technique of photographing an object using several well-defined optical bands in a broad spectral range. Using satellite- and aircraft-based instruments, macro-scale hyperspectral imaging is well established for geo-observation with applications in many different fields such as geology, archaeology and defence. Microscope-based hyperspectral instruments and analysis techniques are successfully employed in bio-medical research. In order to transfer this technique to a non-destructive analysis method of historical documents kept in archives and libraries, a dedicated instrument has been specifically designed by request of the Nationaal Archief (National Archive of the Netherlands). This novel tool provides fully calibrated spectral reflectance data at 70 wavelengths ranging from the near-UV (365 nm) via the visible into the nearinfrared spectral region (1100 nm). Recordings are made over an area of 125 mm x 125 mm, using low-intensity wavelength-tunable light sources, while the temperature and relative humidity in the instrument measurement cabinet are constantly monitored. Even when recording all wavelength bands, a document is exposed for less than 15 minutes and analysis can be subsequently carried out using the digital dataset at any time for various purposes. This guarantees that the instrument is a completely non-invasive tool that can be applied safely even to objects of great value. Quantitative analysis of the extracted calibrated data can be performed, using chemometric methods, to identify writing materials such as inks and pigments to map their concentrations and to monitor the aging processes over various substrates. Excellent results have been obtained for distinguishing various inks, enhancing the contrast of watermarks and improve legibility of faded, or hidden text, even on carbonised paper. Current studies concentrate on the identification, quantification and monitoring of damages present on archival material before and after exposition and during storage conditions, such as biological damages, metal gall inks corrosion, paper oxidation, and pigments fading. <s> BIB009 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Multispectral imagery has been used as the data source for water and land observational remote sensing from airborne and satellite systems since the early 1960s. Over the past two decades, advances in sensor technology have made it possible for the collection of several hundred spectral bands. This is commonly referred to as hyperspectral imagery. This review details the differences between multispectral and hyperspectral data; spatial and spectral resolutions and focuses on the application of hyperspectral imagery in water resource studies and, in particular the classification and mapping of land uses and vegetation. <s> BIB010 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Wetland vegetation plays a key role in the ecological functions of wetland environments. Remote sensing techniques offer timely, up-to-date, and relatively accurate information for sustainable and effective management of wetland vegetation. This article provides an overview on the status of remote sensing applications in discriminating and mapping wetland vegetation, and estimating some of the biochemical and biophysical parameters of wetland vegetation. Research needs for successful applications of remote sensing in wetland vegetation mapping and the major challenges are also discussed. The review focuses on providing fundamental information relating to the spectral characteristics of wetland vegetation, discriminating wetland vegetation using broad- and narrow-bands, as well as estimating water content, biomass, and leaf area index. It can be concluded that the remote sensing of wetland vegetation has some particular challenges that require careful consideration in order to obtain successful results. These include an in-depth understanding of the factors affecting the interaction between electromagnetic radiation and wetland vegetation in a particular environment, selecting appropriate spatial and spectral resolution as well as suitable processing techniques for extracting spectral information of wetland vegetation. <s> BIB011 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Multispectral imaging has been applied to the field of art conservation and art history since the early 1990s. It is attractive as a non-invasive 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 non-invasive imaging and analytical techniques will be discussed. <s> BIB012 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Detecting invisible details and separating mixed evidence is critical for forensic inspection. If this can be done reliably and fast at the crime scene, irrelevant objects do not require further examination at the laboratory. This will speed up the inspection process and release resources for other critical tasks. This article reports on tests which have been carried out at the University of Jyvaskyla in Finland together with the Central Finland Police Department and the National Bureau of Investigation for detecting and separating forensic details with hyperspectral technology. In the tests evidence was sought after at an assumed violent burglary scene with the use of VTT’s 500-900 nm wavelength VNIR camera, Specim’s 4001000 nm VNIR camera, and Specim’s 1000-2500 nm SWIR camera. The tested details were dried blood on a ceramic plate, a stain of four types of mixed and absorbed blood, and blood which had been washed off a table. Other examined details included untreated latent fingerprints, gunshot residue, primer residue, and layered paint on small pieces of wood. All cameras could detect visible details and separate mixed paint. The SWIR camera could also separate four types of human and animal blood which were mixed in the same stain and absorbed into a fabric. None of the cameras could however detect primer residue, untreated latent fingerprints, or blood that had been washed off. The results are encouraging and indicate the need for further studies. The results also emphasize the importance of creating optimal imaging conditions into the crime scene for each kind of subjects and backgrounds. <s> BIB013 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> : The analysis of bloodstain patterns can assist investigators in understanding the circumstances surrounding a violent crime. Bloodstains are routinely subjected to pattern analysis, which is inherently dependent upon the ability of the examiner to locate and visualize bloodstain patterns on items of evidence. Often, the ability to properly visualize bloodstain patterns is challenging, especially when the stain patterns occur on dark and/or patterned substrates. In this study, preliminary research was performed to better understand how near-infrared reflectance hyperspectral imaging (HSI) could be used to observe bloodstain patterns on commonly encountered black fabrics. The ability of HSI to visualize latent bloodstains on several commonly encountered substrates is demonstrated. The images acquired through HSI are of sufficient quality to allow for differentiation between stains produced from an impact mechanism or a transfer mechanism. This study also serves as a proof of concept in the differentiation of multiple staining materials. Because of its ability to generate spectral data, the data provide a preliminary separation of stains where more than one type of stain existed. <s> BIB014 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Hyperspectral imaging (HSI) integrates conventional imaging and spectroscopy, to obtain both spatial and spectral information from a specimen. This technique enables investigators to analyze the chemical composition of traces and simultaneously visualize their spatial distribution. HSI offers significant potential for the detection, visualization, identification and age estimation of forensic traces. The rapid, non-destructive and non-contact features of HSI mark its suitability as an analytical tool for forensic science. This paper provides an overview of the principles, instrumentation and analytical techniques involved in hyperspectral imaging. We describe recent advances in HSI technology motivating forensic science applications, e.g. the development of portable and fast image acquisition systems. Reported forensic science applications are reviewed. Challenges are addressed, such as the analysis of traces on backgrounds encountered in casework, concluded by a summary of possible future applications. <s> BIB015 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> I. INTRODUCTION <s> Food safety is a great public concern, and outbreaks of food-borne illnesses can lead to disturbance to the society. Consequently, fast and nondestructive methods are required for sensing the safety situation of produce. As an emerging technology, hyperspectral imaging has been successfully employed in food safety inspection and control. After presenting the fundamentals of hyperspectral imaging, this paper provides a comprehensive review on its application in determination of physical, chemical, and biological contamination on food products. Additionally, other studies, including detecting meat and meat bone in feedstuffs as well as organic residue on food processing equipment, are also reported due to their close relationship with food safety control. With these applications, it can be demonstrated that miscellaneous hyperspectral imaging techniques including near-infrared hyperspectral imaging, fluorescence hyperspectral imaging, and Raman hyperspectral imaging or their combinations are powerful tools for food safety surveillance. Moreover, it is envisaged that hyperspectral imaging can be considered as an alternative technique for conventional methods in realizing inspection automation, leading to the elimination of the occurrence of food safety problems at the utmost. <s> BIB016
This human eye is only able to see in a limited part of electromagnetic spectrum and can distinguish between objects based on their different spectral responses in that narrow spectral range BIB001 . However, multispectral imaging sensors have been developed that are able to acquire an image in infrared and visible segments of electromagnetic spectrum. This allows material identification on the basis of their unique spectral sig-nature in a wide spectral range. Multispectral imaging exploits the property that each material has its own unique spectral signatures. Spectrum of a single pixel in a multispectral image provides information about its constituents and surface of the material. Multispectral imaging technology is being used for environment and land observation remote sensing in satellite and airborne systems since late 1960s BIB005 . Multispectral imaging systems acquire data in a small number of spectral bands by using parallel sensor arrays. Most of the multispectral imaging systems use three to six spectral bands with large optical band intervals, ranging from visible to near infrared regions of electromagnetic spectrum for scene observation. However, such low number of spectral bands is the limiting factor for discrimination of various materials. Recent developments in hyperspectral sensing during the past two decades has made it possible to acquire several hundred spectral bands of observational scene in a single acquisition. The increased spectral resolution of these hyperspectral images allow for detailed examination of land surfaces and different materials present in the observational scene, which was previously not possible with low spectral resolution of multispectral imaging scanners. Hyperspectral imaging (HSI) or imaging spectrometry BIB002 is a spectral sensing technique in which an object is photographed using several well defined optical bands in broad spectral range. It was originally implemented on satellite and airborne platforms for remote sensing applications but during last two decades, HSI has been applied to numerous applications including agricultural and water resources control BIB010 , BIB011 , military defense, art conservation and archeology BIB007 , BIB012 , medical diagnosis BIB006 , BIB003 , analyses of crime scene details BIB013 , BIB014 , document imaging BIB009 , forensic medicine BIB015 , food quality control BIB008 , BIB016 and mineralogical mapping of earth surface BIB004 . This review details the fundamentals of hyperspectral imaging, discusses the common hyperspectral remote sensing terminologies and highlights the modern applications of hyperspectral imagery in the areas of food quality and safety assessment, medical diagnosis, precision agriculture, water resource management, forensic document examination, artwork authentication and defense and homeland security. 