In this work we evaluate the spectral reflectance and colour associated to the human iris. Some prosthesis used in the clinical practice and cosmetic coloured contact lenses are also analyzed. Specifically 100 real irises corresponding to 50 patients, 68 fake eye balls and 17 coloured contact lenses have been studied. The spectral reflectance profiles in the visible range of these samples have been measured by means of a multi-spectral system developed for this purpose. The system consists of a 12-bit digital CCD camera and an RGB tunable filter, which allows the acquisition of a magnified image of the patient's eye and the reconstruction of the associated spectra by means of the Moore-Penrose pseudo-inverse method. The true spectral reflectances of the samples are also measured using a conventional tele-spectracolorimeter. The measured and reconstructed spectra are compared using the CIEDE2000 colour difference formula as well as the Root Mean Square Error (RMSE). The results obtained show that the system allows the reconstruction of the curves associated to human irises, fake eye balls, and coloured contact lenses with a high accuracy, mainly when the system is trained using the human irises database.
Meritxell Vilaseca, Rita Mercadal, Jaume Pujol, Montserrat Arjona, Marta de Lasarte, Rafael Huertas, Manuel Melgosa, Francisco H. Imai, "Measuring and Analyzing the Colour of the Iris with a Multi-Spectral Imaging System" in Proc. IS&T CGIV 2008/MCS'08 4th European Conf. on Colour in Graphics, Imaging, and Vision 10th Int'l Symp. on Multispectral Colour Science, 2008, pp 427 - 431, https://doi.org/10.2352/CGIV.2008.4.1.art00091