Various experiments have been conducted to investigate the influence of fluorescent whitening agent (FWA) on aspects of colour evaluation. Large amount of samples were prepared by direct dyeing with various concentration of colorant dyes as well as FWA. These dyed samples, together with high-FWA-content samples provided by third party, were used as stimuli in instrumental measurement by spectrophotometer and tele-spectroradiometer as well as in psychophysical experiment. The influence of FWA on instrumental illumination variation, calibration methods' performance, calibration standards' performance are studied. It was found that there is no significant relationship between the material of measured target and calibration standard. It is also found that spectrophotometers agrees well if the UV content in illumination is properly calibrated. A practical design of viewing cabinet with improved quality in UV range was proposed. The additional calibrated UV lamp significantly improved the fluorescent daylight lamps performance in term of metamerism index. Such improvement in UV enabled common viewing cabinets be upgraded to cater the need of visual assessment involving FWA. Three pairs of metameric samples were developed which matched under illumination with certain UV component while mismatched under illumination with other UV conditions. These metameric pairs were developed as UV Visual Aid which could be used as practical checker to visualize the UV quality in light conditions. Psychophysical experiment with category-judgment method was conducted to investigate the preferred white of human. Mean-category-value and ellipsoid fitting were used to find the resulting preferred white colour. There were significant amount of samples which were not within the Tint limit of CIE Whiteness index but were categorized by observers as acceptable white. This indicated the possible need of expanding the Tint limit of CIE Whiteness. Psychophysical experiment with magnitude estimation method was conducted to evaluate the prediction of visual whiteness by various whiteness formulae. CIE Whiteness index had the best agreement between instrumental prediction and visual perception, outperforming Uchida and C/V Whiteness.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:713487 |
| Date | January 2013 |
| Creators | Chen, Ye |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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