Conversion of a digital camera into a non-contact colorimeter for use in stone cultural heritage: The application case to Spanish granites

In this study, a digital CMOS camera was calibrated for use as a non-contact colorimeter for measuring the color of granite artworks. The low chroma values of the granite, which yield similar stimulation of the three color channels of the camera, proved to be the most challenging aspect of the task. The appropriate parameters for converting the device-dependent RGB color space into a device-independent color space were established. For this purpose, the color of a large number of Munsell samples (corresponding to the previously defined color gamut of granite) was measured with a digital camera and with a spectrophotometer (reference instrument). The color data were then compared using the CIELAB color formulae. The best correlations between measurements were obtained when the camera works to 10-bits and the spectrophotometric measures in SCI mode. Finally, the calibrated instrument was used successfully to measure the color of six commercial varieties of Spanish granite.The present study was financially supported by the Xunta de Galicia (09TMT014203PR) and the European Union and Spanish Ministry of Economy and Competitiveness under grants DPI2008-06455-C02-02 and DPI2011-30090-C02-02. Dr. Patricia Sanmartín acknowledges a scholarship for postgraduate studies abroad (2012 Call) from Barrié de la Maza Foundation. She is currently supported by a postdoctoral contract within the framework of the 2011–2015 Galician Plan for Research, Innovation and Growth (Plan I2C) for the year 2012

Evaluation and optimal design of spectral sensitivities for digital color imaging

The quality of an image captured by color imaging system primarily depends on three factors: sensor spectral sensitivity, illumination and scene. While illumination is very important to be known, the sensitivity characteristics is critical to the success of imaging applications, and is necessary to be optimally designed under practical constraints. The ultimate image quality is judged subjectively by human visual system. This dissertation addresses the evaluation and optimal design of spectral sensitivity functions for digital color imaging devices. Color imaging fundamentals and device characterization are discussed in the first place. For the evaluation of spectral sensitivity functions, this dissertation concentrates on the consideration of imaging noise characteristics. Both signal-independent and signal-dependent noises form an imaging noise model and noises will be propagated while signal is processed. A new colorimetric quality metric, unified measure of goodness (UMG), which addresses color accuracy and noise performance simultaneously, is introduced and compared with other available quality metrics. Through comparison, UMG is designated as a primary evaluation metric. On the optimal design of spectral sensitivity functions, three generic approaches, optimization through enumeration evaluation, optimization of parameterized functions, and optimization of additional channel, are analyzed in the case of the filter fabrication process is unknown. Otherwise a hierarchical design approach is introduced, which emphasizes the use of the primary metric but the initial optimization results are refined through the application of multiple secondary metrics. Finally the validity of UMG as a primary metric and the hierarchical approach are experimentally tested and verified

Publicaciones y ponencias - 2004 -

This document presents the list of publications and presentations done by the EAFIT teaching and administrative staff in the year 2004. The information is organized alphabetically by Research Groups of the corresponding Schools. The contributions appear in alphabetical order in the following sequence: international and national publications, and international and national presentations. The publications include books, chapters of books, and articles. The  presentations include conferences, congresses, and general academic events. The majority of these presentations have been published in the proceedings of the corresponding event.Este documento presenta la relación de publicaciones y ponencias realizadas por los profesores y personal administrativo de la Universidad EAFIT en el año 2004. La información está organizada por Grupos de Investigación dentro de cada una de las Escuelas. Cada contribución aparece en orden alfabético dentro de la correspondiente categoría de la siguiente secuencia: publicaciones internacionales, publicaciones nacionales, ponencias internacionales y ponencias nacionales. En las publicaciones están comprendidos los libros, capítulos de libros y artículos de revista. Las ponencias relacionan las presentaciones en conferencias, congresos y eventos de divulgación. La mayoría de estas presentaciones figuran, tal como se indica en cada caso, publicadas como parte de las memorias del evento respectivo