Image Spectrometers, Color High Fidelity, and Fine-Art Paintings

This book chapter presents an introduction to image spectrometers with as example their application to the scanning of fine-art paintings. First of all, the technological aspects necessary to understand a camera as a measuring tool are presented. Thus, CFA-based cameras, Foveon-X, multi-sensors, sequential acquisition systems, and dispersing devices are introduced. Then, the simplest mathematical models of light measurement and light–matter interaction are described. Having presented these models, the so-called spectral reflectance reconstruction problem is presented. This problem is important because its resolution transforms a multiwideband acquisition system into an image spectrometer. The first part of the chapter seeks to give the reader a grasp of how different technologies are used to generate a color image, and to which extent this image is expected to be high fidelity. In a second part, a general view of the evolution of image spectrometers in the field of fine-art paintings scanning is presented. The description starts with some historical and important systems built during European Union projects, such as the pioneering VASARI or its successor CRISATEL. Both being sequential and filter-based systems, other sequential systems are presented, taking care to choose different technologies that show how a large variety of designs have been applied. Furthermore, a section about hyperspectral systems based on dispersing devices is included. Though not numerous and currently expensive, these systems are considered as the new high-end acquisition equipment for scanning art paintings. A. Ribés ( ) EDF Research & Development, 1 avenue du Général de Gaulle, BP 408, 92141 Clamart Cedex, France e-mail: [email protected] C. Fernandez-Maloigne (ed.), Advanced Color Image Processing and Analysis, DOI 10.1007/978-1-4419-6190-7 14, © Springer Science+Business Media New York 2013 449