New source and detector technology for the realization of photometric units

Abstract

The production of incandescent light bulbs is bound to end, as incandescent lighting is being phased out globally in favour of more energy-efficient and sustainable solutions. Temporally stable light-emitting diodes (LEDs) are potential candidates to replace incandescent lamps as photometric source standards. However, traditional V(λ) filter based photometers may have large uncertainty when LEDs are measured instead of incandescent lamps. This is due to the narrow and complicated spectra of LEDs. When the spectra of LEDs are limited to the visible wavelength range, new silicon detector technology can be advantageously exploited in photometry. We present a novel method—based on the recently introduced Predictable Quantum Efficient Detector (PQED)—for the realization of photometric units which completely eliminates the need to use V(λ) filters. Instead, the photometric weighting is taken into account numerically by measuring the relative spectral irradiance. The illuminance values of a blue and a red LED were determined using the new method and a conventional reference photometer. The values obtained by the two methods deviated from each other by −0.06% and 0.48% for the blue and red LED, respectively. The PQED-based values have much lower standard uncertainty (0.17% to 0.18%) than the uncertainty of the values based on the conventional photometer (0.46% to 0.51%).