Standard specifications vs metrology of LED illumination systems

With the emerging availability of commercial LED based illumination systems, new families of standard specifications evolved. The special properties of LED compared to conventional thermal light sources lead to several new aspects in various fields of standardization and metrology, such as colour fidelity, luminance, problems of coherence and temporal power modulation, connected partially with problems found in laser technology. On one hand, fidelity standards had to be redefined, on the other hand, standards connected with occupational safety and health had to be adapted. Compliance with these standards is ensured by metrology methods and devices, which are subject to standard specifications, too. In the paper, we discuss the conformity of the metrology methods and devices proposed with the standard specification itself; flexibilities in the standard specifications leading to obvious gaps between the metrology and the technical definitions are addressed. Further on, technical simplifications made in the standard specifications are discussed under biological aspects. Finally, in continuation of our investigations on special temporal perception effects, as published in recent years, we discuss some results from spectral analysis in low frequency spectral domain.