In the finalized project BiRD JRP 16NRM08 (https://www.birdproject.eu), funded by the EU program EURAMET EMPIR Call 2016 – „Metrology Research for Pre‐ and Co‐normative projects“, basic research was carried out on such measurands which determine the appearance of products. These are, amongst color and its angle-dependent distribution also gloss, sparkle, and graininess. The term sparkle describes the specific appearance of surfaces which can be observed under directed illumination by reflection of point-like scattering centers and is similar to the appearance of sparkling stars in the night-sky. This effect is generated e.g. by high-reflective microparticles, which are embedded in the lacquer coat of a surface. Well-known examples are metallic automobile coatings. Graininess describes the appearance of such surfaces when illuminated diffusely [1]. Although the sparkle-effect is widely applied in industrial production, there is no...

In the project BxDiff JRP 18SIB03 (https://bxdiff.cmi.cz/), which is supported within the EU program EURAMET EMPIR Call 2018 - SI Broader Scope, measurement systems in the status of national standard facilities are created to perform BTDF - (Bidirectional transmittance distribution function) and BSSRDF - (Bidirectional surface scattering distribution function) investigations. PTB funds therein the development of a dedicated BTDF measurement facility in terms of a so-called “Größtgerät” (strategic investment). Main aims of the 17 involved partners stemming from national metrology institutes, research and university institutes, and material processing companies, are to close the measurement-technology gap for the mentioned measurands as well as to expand existing techniques into currently not accessible regimes. For example, it is envisaged to apply BRDF (Bidirectional reflectance distribution function) measurements to small samples with...

Measuring the total momentum transfer of the absorbed and re-emitted photons from a highly reflective surface (reflection of the laser beam from an optical mirror) as a force provides the possibility of measuring the optical power with direct traceability to SI units.  PTB and the Technical University of Ilmenau (TUI) recently reviewed the viability and precision of the photon-momentum-based optical power measurement method that employs an amplification effect caused by a multi-reflected laser beam trapped in an optical cavity. Trial measurements were performed at two different metrology laboratories: the laboratory for mass/force at the TUI, and the clean room laser radiometry laboratory at PTB, using a portable force measurement setup developed by TUI, consisting of two electromagnetic force compensation balances. We compared the results of the optical power measurements performed with the force measurement setup, via the...