Developing LED-based standard lamps for solid-state light calibration
Solid-state lighting (SSL), which uses light-emitting diodes (LEDs), has replaced traditional incandescent lighting across many industries, workplaces, and products, due to lower power consumption and greater durability. However, the development of SSL technology did not have a parallel development for updated calibration standards. The standard lamps used for calibrations and V(λ)-filtered photometers used as transfer standards were based on incandescent bulbs with correlated colour temperatures (CCT) of 2856 K. The use of these standards when measuring SSL devices caused spectral errors and so new LED standard lamps were required.
This project defined new reference spectra for LEDs, including RGB (red, green, blue) and violet LEDs which could be suitable standard illuminants for colorimetry. The analysed LED illuminants were included in the 4th edition of the CIE Technical Report no. 15: Colorimetry.
The relative spectral power distributions of 1516 LED products of different types were also measured, including spots, tubes, streetlamps, and from a large number of lighting manufacturers. Based on these new reference spectra, the project produced new photometric standard lamps for luminous intensity and luminous flux using suitable white LEDs.For luminous intensity, 8 standard lamps, able to produce an output aperture and luminous intensity similar to those of a traditional incandescent Wi41/G standard lamp, were constructed and characterised. For luminous flux, 2 types of lamps were developed, designed to ensure compatibility with hardware already in use at laboratories.
The new lamps were tested in two intercomparisons, indicating that LED standard lamps with 4100 K CCT are suitable for use as transfer standards and can outperform incandescent standards due to higher resilience when in transit.
These results led to the development of a new reference spectrum for improved photometer calibration that was incorporated into a CIE technical report published in 2023.
The project also produced new photometric measurement methods and new reference photometers, based on predictable quantum-efficient detectors (PQED), which do can operate without optical V(λ) filters. These allow illuminance measurements for the newly produced LED standard lamps, with uncertainties as low as 0.2%.
The new standards developed by this project can be used by National Measurement Institutes and test laboratories to accurately calibrate solid-state light photometers and give European industry an advantage in the development of new commercial standard lamps.
This will result in more reliable classifications of solid-state lighting, increasing consumer confidence in this greener technology.
Coordinator: Tuomas Poikonen (MIKES)
For more information, please contact the EURAMET Management Support Unit:
Phone: +44 20 8943 6666