Characterization of the LED filament lamp for luminous intensity calibration

Abstract

Light-emitting diode (LED) is now the main type of light source in global lighting marketing. However, traditional photometry with incandescent standard lamp is not sufficient to implement high level LED photometric measurement since a considerable spectral mismatch error may exist if the photometer has a large general V(λ) mismatch index . LED standard lamp is proposed to be the complementary transfer standard for photometry to reduce this measurement uncertainty. National Institute of Metrology, China (NIM) has previously reported a type of LED filament lamp for total luminous flux. In this article, NIM demonstrates another type of LED filament lamp for luminous intensity calibration. The LED filaments are sealed in T90 cylinder glass bulb as emitters, and has a spectrum similar to the reference white LED spectrum considered in Commission on Illumination (CIE) technical committee 2-90. The LED lamp uses the E27 screw base as the connector, and is compatible with the traditional alignment approaches. The warm-up time is less than 12 minutes. The output change of a group of 12 lamps, over a nearly two years of storage and 1 hour operation every day during the whole long term test, is found to be ±0.2 % or less for most of the lamps. The ageing effect of one lamp over a continuously 6500 hours burning is estimated to be -0.014% per hundred hours, and it is significantly lower than 1% per hundred hours, the typical drift rate of traditional incandescent luminous intensity lamp. In the aspect of the coincidence with inverse square law, the LED lamp has a similar performance to the WI41/G lamp, the traditional luminous intensity lamp.

Recent advances and perspectives in photometry in the era of LED lighting

“…Practical LED light sources [18][19][20], with spectral irradiance resembling the L41 spectrum, have been developed. Even if their spectra would somewhat deviate from the reference spectrum L41, they would reduce the spectral mismatch error in photometer calibration relative to calibrations using incandescent lamps.…”

“…Even if their spectra would somewhat deviate from the reference spectrum L41, they would reduce the spectral mismatch error in photometer calibration relative to calibrations using incandescent lamps. The LED light sources [18][19][20] have also other promising features, such as robustness and stability, which make them attractive as complementary standard lamps, working standards, and comparison artefacts. Their performance will be tested in a forthcoming international comparison measurement with global coverage of participants.…”