A novel technique of reflective spectroscopy, hyperspectral imaging (HSI), was used to develop a methodology for colour measurement, which is very important in the field of art conservation - especially in the analysis of documents. The major focus of this work is an examination of the repeatability and reproducibility of colour parameters calculated from the hyperspectral data. The study was performed with commercial colour standards and pen ink lines, corresponding to large and small-scale colour areas, respectively. In some cases, the error of parameter determination indicated significant differences between the examined sample sets, which may be attributed to the low population of pixels from which the colour data were obtained. Our study allowed the development of an optimal hyperspectral image acquisition method for applications requiring accurate determination of the object's spectral characteristics. Besides determining the proper measurement procedure and the colour accuracy of the HSI, our study is also used to test this method for colour change monitoring of a real-life sample - a document treated with low-temperature plasma as a cleaning agent. The results proved that, by using hyperspectral imaging, colour change can be precisely determined and monitored within a selected area on the object. The application of HSI presented in our study was found to be an important alternative to conventional colorimeters.
Keywords: Colour; Document processing and analysis; Hyperspectral imaging; Reflectance spectroscopy; Repeatability.
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