Development of LED-based standard source for total luminous flux calibration

Abstract

For total luminous flux calibration by a sphere-spectroradiometer system in 2π geometry, a new LED-based standard light source (standard LED) covering the full visible wavelength range has been developed. The developed standard LED has sufficient spectral power over the full visible wavelength range using UV-LED dies of different peak wavelengths in combination with red, green and blue phosphors. By evaluating spectrum flatness based on the magnitude of the second derivative, the spectrum of the standard LED was customised to minimise the measurement uncertainty. Properties of the standard LED such as the luminous intensity distribution, stability and reproducibility were also evaluated. The evaluation results indicate that the standard LED has good properties as a standard light source for the 2π total spectral radiant flux scale. Furthermore, the result of an operating current dependence suggests that the standard LED has benefits as a standard source that conventional standard lamps do not have.

Led Filament Standard Lamps for Total Luminous Flux and Luminous Intensity

“…To achieve a wide spectral bandwidth, there are usually two ways: one is to use multiple LED chips with different peak wavelengths and packaged together according to a specific arrangement. Another way is to coat the blue LED die with yellow phosphor (Nakazawa et al, 2018). The developed LED filament standard lamp adopts the latter method, and its spectrum and CCT are close to the CIE illuminant L, as shown in Figure 2.…”

“…CIE lists "New Calibration Sources and Illuminants for Photometry, Colorimetry and Radiometry" as one of the top ten strategic plans. NMIJ (Japan) developed a new standard LED of total spectral radiant flux in 2π geometry (Nakazawa et al, 2018). PTB (Germany) developed 2 types of high power (100 lm and 2500 lm) LED-based calibration standards for luminous flux (Zwinkels, 2016).…”

Establishment of 2π total spectral radiant flux scale with a broadband LED-based transfer standard source

“…Then the halogen lamps are used only at the mounting condition with these lamps calibrated. Recently, NMIJ and Nichia Corporation developed a new LED-based standard source (2π standard LED) that is suitable for use as a transfer standard source of 2π TSRF measurement [9]. For 2π geometry measurement, LED-based sources are readily available because LED chips typically have the property of emitting light only in the forward direction.…”

“…However, few reports have described studies examining LED source development as a transfer standard with emphasis on extending the spectral range of the spectrum [16]. To resolve the shortcomings described above, we developed a 2π standard LED for use in spectral measurements to avoid spectral-shape-related uncertainty to the greatest degree possible [9].…”

Development of a Compact-Size Standard Led for Sphere-Spectroradiometer in 2pi Geometry

“…Recently, NMIJ and Nichia Corporation have developed a new LED based standard source (2 standard LED) that is suitable for TSRF measurements in 2 geometry (Nakazawa et al, 2018). The 2 standard LED has sufficient spectral power over the full visible wavelength range.…”