LED-valoon perustuva standardivalolähde valaistussuureiden realisointiin

摘要

Standard lamps of luminous intensity are widely used in the field of photometry as references or stable sources in calibration measurements and in realization of SI units. Due to the fact that the lighting industry is moving from incandescent and fluorescent lamps to LED-based lighting, a concern about the availability of the incandescent standard lamps has arisen. Laboratories have to develop new methods and equipment to measure new light sources, such as LEDs, which differ from the traditional incandescent lamps, especially in spectral and angular properties. According to a recently published study, spectral errors in photometric measurements of LEDs can be reduced down by a factor of 3 on the average, if incandescent calibration sources are replaced by LED-based sources in calibration of photometers. Recently, the development of white LEDs has produced a wide range of LEDs with increased optical output and different colour temperatures.Some of these LEDs may be suitable to be used as stable calibration sources. In this work, a new LED-based luminous intensity standard lamp has been developed for use in photometric calibrations as a stable source of illuminance.The new source was characterised for temporal stability, spectral and angular properties, as well as for repeatability of luminous intensity. The LED-based standard lamp performed equally or better than a traditional Osram Wi41/G incandescent standard lamp. The expanded uncertainty of the luminous intensity measurement of the LED standard lamp is 0.62 % (k = 2) at the distance between 0.5 m - 4 m.