Color measurements with colorimetric and multispectral imaging systems

Abstract

This work is focused on the study and comparison of the performance for color measurements of different systems based on optoelectronic imaging sensors. We used two different configurations of the imaging system, one with three acquisition channels and the other with more spectral bands, in order to measure the color associated to each pixel of the captured scene. We applied different methodologies to obtain the XYZ tristumulus values from the measured digital signals. The different techniques included an absolute spectral and colorimetric characterization of the system and also direct transformations between both sets, which used several mathematical fittings such as the pseudo-inverse technique, a non-linear estimation method and the principal component analysis. The proposed configurations were experimentally tested imaging the patches of the Gretagmacbeth ColorChecker DC and Color Rendition charts placed in a light booth, and measuring the corresponding colors. The results obtained showed that optoelectronic imaging systems can be used in order to perform rather accurate color measurements with high spatial resolution. Specifically, the best results in terms of CIELab color differences were achieved by using a multispectral configuration of the imaging system with seven spectral bands and directly transforming the digital signals into XYZ tristimulus values by means of the pseudo-inverse technique.