Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <s> Image spectroscopy (IS) is an important tool for the noninvasive analysis of works of art. It generates a wide sequence of multispectral images from which a reflectance spectrum for each imaged point can be recovered. In addition, digital processing techniques can be employed to divide the images into areas of similar spectral behavior. An IS system designed and developed in our laboratory is described. The methodology used to process the acquired data integrates spectral analysis with statistical image processing: in particular, the potential of principal-component analysis applied in this area is investigated. A selection of the results obtained from a sixteenth-century oil-painted panel by Luca Signorelli is also reported. <s> BIB001 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <s> Abstract Laser induced breakdown spectroscopy (LIBS) was used for the first time in the in-situ identification of pigments in an illuminated manuscript dated from the 12th-13th century ad . Spectral data are presented from the analysis performed on the illumination of an initial letter ‘T’ and on the gold paint used in several parts of the writing. Identification of most pigments, in a nearly non-destructive way, was achieved. In parallel to LIBS, hyper-spectral imaging analysis was performed, which enabled the mapping of the pigments’ spatial distribution on the basis of their characteristic, visible and near infrared absorption spectral features. The identification of the red pigment based on hyper-spectral imaging analysis is demonstrated. Identification of pigments and inks is of great importance for the dating and systematic characterization of illuminated manuscripts and, as shown in this work, a combined analytical approach can provide important and useful information. <s> BIB002 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <s> Abstract We have developed a computer controllable hyper-spectral imaging apparatus, capable of acquiring spectral images of 5 nm bandwidth and with 3 nm tuning step, in the spectral range 380–1000 nm. The critical component of the apparatus is the innovative imaging monochromator, which enables the tuning of the imaging wavelength. This module is coupled with a two-dimensional detector array composing a tunable wavelength camera system. Electronic controllers are employed for detector and monochromator synchronization and driving, while the system calibration, image processing and analysis are performed with the aid of specially developed software. The system records light intensity as a function of both wavelength and location. In the image domain, the data set includes a full image at each individual wavelength. In the spectroscopy domain, a fully resolved diffuse reflectance and/or fluorescence spectrum at each individual pixel can be recorded. The developed spatially resolved spectral acquisition system is ideal for the non-destructive analysis of heterogeneous materials such as objects of artistic and historic value. Experimental studies show its potential in assisting the identification and mapping of painting materials in situ. Furthermore, it was shown that it enables the recovery of erased–overwritten scripts in old manuscripts and the determination of proper spectral bands for the on-line monitoring of laser and non-laser cleaning procedures. <s> BIB003 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <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> BIB004 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <s> Diffuse reflectance hyperspectral imaging, or reflectance imaging spectroscopy, is a sophisticated technique that enables the capture of hundreds of images in contiguous narrow spectral bands (bandwidth < 10 nm), typically in the visible (Vis, 400-750 nm) and the near-infrared (NIR, 750-2500 nm) regions. This sequence of images provides a data set that is called an image-cube or file-cube. Two dimensions of the image-cube are the spatial dimensions of the scene, and the third dimension is the wavelength. In this way, each spatial pixel in the image has an associated reflectance spectrum. This "big data" image-cube allows for the mining of artists' materials and mapping their distribution across the surface of a work of art. Reflectance hyperspectral imaging, introduced in the 1980s by Goetz and co-workers, led to a revolution in the field of remote sensing of the earth and near planets ( Goetz, F. H.; Vane, G.; Solomon, B. N.; Rock, N. Imaging Spectrometry for Earth Remote Sensing . Science , 1985 , 228 , 1147 - 1152 ). In the subsequent decades, thanks to rapid advances in solid-state sensor technology, reflectance hyperspectral imaging, once only available to large government laboratories, was extended to new fields of application, such as monitoring agri-foods, pharmaceutical products, the environment, and cultural heritage. In the 2000s, the potential of this noninvasive technology for the study of artworks became evident and, consequently, the methodology is becoming more widely used in the art conservation science field. Typically hyperspectral reflectance image-cubes contain millions of spectra. Many of these spectra are similar, making the reduction of the data set size an important first step. Thus, image-processing tools based on multivariate techniques, such as principal component analysis (PCA), automated classification methods, or expert knowledge systems, that search for known spectral features are often applied. These algorithms seek to reduce the large number of high-quality spectra to a common subset, which allow identifying and mapping artists' materials and alteration products. Hence, reflectance hyperspectral imaging is finding its place as the starting point to find sites on polychrome surfaces for spot analytical techniques, such as X-ray fluorescence, Raman spectroscopy, and Fourier transform infrared spectroscopy. Reflectance hyperspectral imaging can also provide image products that are a mainstay in the art conservation field, such as color-accurate images, broadband near-infrared images, and false-color products. This Account reports on the research activity carried out by two research groups, one at the "Nello Carrara" Institute of Applied Physics of the Italian National Research Council (IFAC-CNR) in Florence and the other at the National Gallery of Art (NGA) in Washington, D.C. Both groups have conducted parallel research, with frequent interchanges, to develop multispectral and hyperspectral imaging systems to study works of art. In the past decade, they have designed and experimented with some of the earliest spectral imaging prototypes for museum applications. In this Account, a brief presentation of the hyperspectral sensor systems is given with case studies showing how reflectance hyperspectral imaging is answering key questions in cultural heritage. <s> BIB005 </s> Modern Trends in Hyperspectral Image Analysis: A Review <s> F. ARTWORK AUTHENTICATION <s> In recent years various scientific practices have been adapted to the artwork analysis process. Although a set of techniques is available for art historians and scientists, there is a constant need for rapid and non-destructive methods to empower the art authentication process. In this paper hyperspectral imaging combined with signal processing and classification techniques are proposed as a tool to enhance the process for identification of art forgeries. Using bespoke paintings designed for this work, a spectral library of selected pigments was established and the viability of training and the application of classification techniques based on this data was demonstrated. Using these techniques for the analysis of actual forged paintings resulted in the identification of anachronistic paint, confirming the falsity of the artwork. This paper demonstrates the applicability of infrared (IR) hyperspectral imaging for artwork authentication. <s> BIB006
The global art market is increasing rapidly over the past decades  . A 7% year on year increase in total sales of art and antiques was recorded in 2013  . Most of these high value dealings were made using non-scientific expertise in art. Forensic testing was not used to assure authenticity of the traded object. However, only a limited number of artwork evaluations can be carried out by an experienced specialist. Foolproof evaluations can be carried out if supported by non-destructive scientific tests  ,  . Fourier Transform Infrared (FTIR), X-ray fluorescence, and Raman spectroscopy have been used previously for artwork authentication  ,  . HSI is proposed as a novel and non-destructive artwork examination method in the recent literature. HSI limits the number of invasive tests needed and provides more information from a sample. Several methods employing pigment analysis provided by HSI and classification techniques have been proposed in the recent literature BIB004 ,  - BIB001 for conservation and restoration of artworks such as paintings. These methods allow for identification of restored regions in paintings and distinguish them from the important regions in the original painting. Hyperspectral images captured in the infrared range also revealed useful features of painters such as preparatory drawings BIB005 . Two forged paintings and the results of IR hyperspectral imaging and SVM classification proposed in BIB006 are illustrated in Figure 10 . The broad spectral information provided by HSI combined with signal processing also allows for identification of the underlying material in artworks. Materials which are clearly visible in a specific band and obscured in the other bands are reflective within the same band and thus easily detectable by the HSI system  . The appropriate bands in the HSI data of historic texts and manuscripts allow for identification of inks and pigments for dating of manuscripts BIB002 and recovery of erased and overwritten scripts BIB003 .