Over the past three decades, significant developments have been made in hyperspectral imaging due to which it has emerged as an effective tool in numerous civil, environmental, and military applications. Modern sensor technologies are capable of covering large surfaces of earth with exceptional spatial, spectral, and temporal resolutions. Due to these features, hyperspectral imaging has been effectively used in numerous remote sensing applications requiring estimation of physical parameters of many complex surfaces and identification of visually similar materials having fine spectral signatures. In the recent years, ground based hyperspectral imaging has gained immense interest in the research on electronic imaging for food inspection, forensic science, medical surgery and diagnosis, and military applications. This review focuses on the fundamentals of hyperspectral image analysis and its modern applications such as food quality and safety assessment, medical diagnosis and image guided surgery, forensic document examination, defense and homeland security, remote sensing applications such as precision agriculture and water resource management and material identification and mapping of artworks. Moreover, recent research on the use of hyperspectral imaging for examination of forgery detection in questioned documents, aided by deep learning, is also presented. This review can be a useful baseline for future research in hyperspectral image analysis.

Modern Trends in Hyperspectral Image Analysis: A Review

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.

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Advances in multispectral and hyperspectral imaging for archaeology and art conservation

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.

Multispectral and hyperspectral imaging technologies in conservation: current research and potential applications

Terahertz imaging for non-destructive evaluation of mural paintings

ConspectusDiffuse 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, ...

Reflectance Hyperspectral Imaging for Investigation of Works of Art: Old Master Paintings and Illuminated Manuscripts

Wide-band near-infrared refiectography is a familiar imaging technique for conservators. For many decades it has been the most effective method for providing an extensive knowledge of underdrawings, retouchings and pentimenti. In this study, a narrow-band multi-wavelength imaging (image spectroscopy) system assembled around a lead oxide-lead sulphide (PbO-PbS) vidicon camera is described and applied to the investigation of paintings in the visible and near-infrared regions. A suitable methodology has been set up in order to make the measurements accurate and reliable. The technique has been applied to the detection of different pigments in the sixteenth-century panel painting ‘La strage degli undicimila martiri’ by Pontormo.

Image spectroscopy mapping technique for noninvasive analysis of paintings

Imaging spectroscopy technique was introduced in the cultural heritage field in the 1990s, when a multi-spectral imaging system based on a Vidicon camera was used to identify and map pigments in paintings. Since then, with continuous improvements in imaging technology, the quality of spectroscopic information in the acquired imaging data has greatly increased. Moreover, with the progressive transition from multispectral to hyperspectral imaging techniques, numerous new applicative perspectives have become possible, ranging from non-invasive monitoring to high-quality documentation, such as mapping and characterization of polychrome and multi-material surfaces of cultural properties. This article provides a brief overview of recent developments in the rapidly evolving applications of hyperspectral imaging in this field. The fundamentals of the various strategies, that have been developed for applying this technique to different types of artworks are discussed, together with some examples of recent applications.

https://www.mdpi.com/1424-8220/20/10/2843/pdf

Hyper-Spectral Imaging Technique in the Cultural Heritage Field: New Possible Scenarios.

Reflectance spectroscopy supplies fundamental information for investigating art objects and diagnosing their state of conservation. Until recently, reflectance spectra could be measured only on samples taken from the art objects. Recent progresses in fiber optics reflectance spectroscopy (FORS) and image spectroscopy (IS) have made it possible, however, to perform non-invasive measurements. Moreover, the two techniques can supply data in large enough quantities as to make the use of sophisticated statistical methods significant for detecting variations due to ageing and degradation. FORS and IS are, in a sense, complementary techniques as the former provides information on single points, while the latter provides 2-D maps from which the reflectance spectrum of each pixel can be displayed. Both FORS and IS were applied in the case study on the Lansdowne version of the Madonna dei fusi (Madonna of the Yarnwinder). In particular, IS was realized by means of a hyper-spectral scanner recently assembled at the "Nello Carrara" Istituto di Fisica Applicata. The characteristics of the scanner are: 0.1 mm spatial sampling over a 1x1 m2 surface and ~1 nm spectral sampling in the wavelength range from 400 nm to 900 nm. The information provided by these two techniques was consistent with what supplied by the non-invasive techniques employed by the other teams participating in the case study, in particular as regards the pigments, the preparatory layer, the binding medium, and the previous restoration works.

Fiber optic reflectance spectroscopy and hyper-spectral image spectroscopy: two integrated techniques for the study of the Madonna dei Fusi

The present paper, which focuses on the identification of red lake pigments, in particular madder, brazilwood, and cochineal, addresses the advantages and drawbacks of using reflectance hyperspectral imaging in the visible and near-infrared ranges as a non-invasive method of discrimination between different red organic pigments in cultural heritage objects. Based on reconstructions of paints used in the period extending from the fourteenth to the sixteenth century, prepared with as far as possible historical accuracy, the analyses by means of visible/near-infrared reflectance hyperspectral imaging were carried out with the objective of understanding the most significant differences between these vegetal- and animal-based red lake pigments. The paper discusses the results that were obtained on four original Italian and North European paintings and compared with those from the paint reconstructions, in order to demonstrate how the hyperspectral imaging technique can be usefully and effectively applied to the identification and mapping of red lake pigments in painted surfaces of interest in the conservation field.

Non-invasive identification of traditional red lake pigments in fourteenth to sixteenth centuries paintings through the use of hyperspectral imaging technique

In recent years Hyper-Spectral Imaging (HSI) technologies have become well-established for applications in the field of Cultural Heritage, and in particular for non-invasive analysis and high quality documentation of paintings and other polychrome surfaces. This paper reports on the latest developments of the on-going research at IFAC-CNR, where a new prototype of a high-performance hyper-spectral scanner, operating in the NIR spectral region (900-1700nm range), was designed, assembled and tested. This new NIR scan-head was designed to be mounted on the same mechanical structure used for the earlier IFAC-CNR scanner prototype, which operated in the 400-900nm range. As ultimate goal the whole system would be intended to provide 2D hyper-spectral data on the extended 400-1700nm range, so as to strongly improve the capability of pigment discrimination, and to increase the possibility of visualizing the underlying features of the polychrome surfaces (such as under-drawings, pentimenti, etc.). In the present version, the NIR scan-head operates with a spectral sampling rate of about 2 nm, and a spatial sampling rate of about 9 dots per millimeter. The results of testing and characterization of the new high resolution NIR IFAC-CNR scanner are presented, with a focus on the main technical problems tackled in customizing the new system for the investigation and documentation of paintings.

Lorenzo Stefani

Papers

Image spectroscopy mapping technique for noninvasive analysis of paintings

Hyper-Spectral Imaging Technique in the Cultural Heritage Field: New Possible Scenarios.

Fiber optic reflectance spectroscopy and hyper-spectral image spectroscopy: two integrated techniques for the study of the Madonna dei Fusi

Non-invasive identification of traditional red lake pigments in fourteenth to sixteenth centuries paintings through the use of hyperspectral imaging technique

Extending hyperspectral imaging from Vis to NIR spectral regions: a novel scanner for the in-depth analysis of polychrome surfaces