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EMPIR BxDiff project “New quantities for the measurement of appearance” develops traceable calibrations procedures for BTDF and BSSRDF measurements


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 sizes in the (sub)-millimeter range.

As an indispensable basis to perform traceable measurements a clear and commonly accepted definition of the measurand is crucial. Discussions within the project regarding measurement geometries and sample properties, these may vary much from solely surface scattering objects to those with noticeable dissipative sub-surface bulk scattering, led to the identification of fundamental scattering quantities for the processes under investigation. Related results can be taken from the recently published Optics Express paper.

Fundamental scattering quantities for the determination of reflectance and transmittance, A. Ferrero, J.R. Frisvad, L. Simonot, P. Santafé, A. Schirmacher, J. Campos, and M. Hebert, Optics Express Vol. 29, No. 1 / 4 January 2021, doi.org/10.1364/OE.410225


WG 4.51 Reflection and Transmission
A. Schirmacher, Alfred.Schirmacher@ptb.de
T. Quast,     Tatjana.Quast@ptb.de


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