PhD abstract

Gloss is a visual appearance attribute. It is a construction from the visual system built on the optical signal from a surface and sensed by the eye. Recent developments in fundamental spectrophotometry lead to instruments able to measure luminous reflection with an acuity equal to the visual system in terms of angular resolution and dynamic. A cross-discipline description between optics and vision is now possible on a same set of samples. In this work, we build through sol-gel process a metrological gloss scale. It is multivariate in terms of surface topology, refractive indices, hue and gloss levels. This scale is then characterized in roughness, specular gloss and BRDF. We expose the measurement techniques and corrections used on our goniospectrophotomer ConDOR. This instrument is dedicated to high resolution measurement of specular peaks. By the end of this study, Condor has reached an angular resolution of 0.014°, the smaller achieved until now, twice better than the human visual system acuity. The dynamic range extends over 6.5 decades. ConDOR is used to measure BRDF of several glossy samples from different scales. These measurements are studied and discussed. A first link between roughness and BRDF is drawn.Using a reference gloss scale, we finally study two aspects of gloss perception: both effects of a change in the solid angle of illumination and in the observation environment realism. Our results indicate that the visual system is more sensitive to gloss variations under realistic conditions as well in lighting as in environment. This effect is particularly noticeable on matt samples. Lesser realistic or lesser natural conditions could lead observers to confusion.

PhD thesis

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TEL : 2017CNAM1133

Key words

Gloss, BRDF, Psychometric scales, Sol-Gel, Goniospectrophotometry, ConDOR.