Optical Properties Of Fluorescent Dyes And Their Computer Color Matching

Computer Colour Matching (CCM) is based on the theory of colorimetry and the Kubelka-Munk theory that represents the relation between reflectance and concentration, and gives recipes in a suitable matching algorithm. The use of fluorescent dyes on textile had become widespread in keeping with the demand for bright and clear white shades. Because of the special optics performance of fluorescent dyes, CCM systems are unable to predict the recipes of clothes with fluorescent dyes. This study was focused on the research and investigation of fluorescent dyes in order to found the fundamentals of fluorescence to give useful information for CCM of fluorescent dyes.Fluorescent dyes have typical optics properties, i.e.; they absorb energy in the near-ultraviolet and visible region of spectrum and emit the fluorescent energy in the visible region. The measured reflectance consisted of the energy of reflectance and emission. Now, there are no simple and reliable methods to separate out the true reflectance and the fluorescence portion from the measured reflectance.It is very effective to study optics properties of the solution of fluorescent dyes. Through a series of experiment and analysis, following results could be concluded: fluorescent dyes have a fixed absorption and emission band in which both have a maximum energy wavelength. The curve of absorption is mirror symmetry of that of emission, In a certain range of concentration, the energy of emission and absorption is positive proportional to the concentration of fluorescent dyes.Also, a sort of experiments and examinations of whiten-gray, whiten-dyed and dyed fabric and an analytic research have been carried out to investigate the dependence of reflection on concentration. The proportion of ultraviolet in the lightsource shows an important effect on the emitted fluorescence energy. The fluorescence energy absorbed by background can not be neglected and affected the total emitted fluorescence energy. A literature has reported that the true reflectance was the combination of the reflectance measured by polychromatic at long wavelength with the reflectance measured by monochromatic at the short wavelength, which has proved to be false in our experiments. In this study, apparent energy flux of fluorescence is defined to represent the effects of fluorescence of fluorescent dyes and the relation between the effects and the concentration. The true reflectance of fluorescent dyes has been calculated by E. Allen's method. Through the results of the true reflectance, the quantum efficiency of fluorescent dyes has been studied. Chromaticity characteristics of fluorescent dyes have been studied and chromaticity charts have been drawn.Based on K-M theory and double-mode light path, a simple equation for calculating fluorescent quantum efficiency has been put forward. Three hypothesis are proposed in addition to the hypothesis of K-M theory: (1)the absorption wavelength and the emission wavelength are not overlapped; (2)the fluorescent emission is identical whether in down or up propagating directions; (3) the fluorescent energy is directly proportional to the exciting energy that absorbed by the fluorescent materials and the ratio is fluorescent quantum efficiency. The dependence of quantum efficiency on the concentration and wavelength has been discussed. Quantum efficiency is a fixed value at any wavelength. Within the quenching concentration, quantum efficiency does not show any changes.The two different optical models of fluorescent dyes have been compared and a satisfactory and identical result has been obtained which gives a way to the CCM of the fluorescent dyes.A new method- three regions method for color matching of fluorescent dyes (including fluorescent whitening agents) has been studied and the average color difference is no more than 2.