Towards the Implementation of the Concept of Visual Appearance in Reflectometry

Metrological Instrumentation

Visual appearance is the superordinate concept for effects of colour respectively colour change, gloss, haze, orange peel, texture, transparency etc. All these effects look different for different observers, depending on the illumination with sunlight or artificial light, especially with the increasing importance of LED-sources for illumination purposes and the angle between illumination, sample and observer. Furthermore the industrial importance of e.g. multi colour lacquering, textures etc. especially in the automotive industry is rapidly increasing. Therefore visual appearance is expected to be one of the most important issues in the field of reflectometry within the next years. This was also acknowledged by the EURAMET Technical Committee “Photometry and Radiometry”, because it plays an important role within its Roadmap 3 “Physical measurement of physical perception for product quality”. One of the final goals of this roadmap is to replace the human observer in production control by physical measurands and quantities.
Mrs. Holopainen has carried out first measurements with respect to the above mentioned effects of visual appearance. This was mainly the characterisation of the whole hemispherical reflection indicatrix for standard reflection materials, like Opal glasses, Barium sulphate standards, PTFE-based standards (PTFE: Polytetrafluoroethylene) and Ceramic standard materials. Furthermore, she evaluated basic principles and practices concerning the existing gonioreflectometer and performed reflectance measurements related to an article “Comparison measurements of 0:45 radiance factor and goniometrically determined diffuse reflectance” published in Applied Optics (Applied Optics: 48 (2009), 15, 2946 - 2956, DOI: Investigation of the translucency properties of some standard diffuse reflection materials were carried out.

TU Braunschweig
Ph.D. student: 
Häkkinen (née Holopainen)