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

Abstract

The National Metrology Institute of Japan realized a total spectral radiant flux scale in the visible wavelength range (from 380 nm to 780 nm) for sphere-spectroradiometer calibration in 2π geometry. For a transfer standard in 2π geometry, a standard source based on a specially-designed broadband light-emitting diode (2π standard LED) was used. For the scale realization, we used the goniophotometer/spectroradiometer system. In the realization, an effect of a bandpass function of the array spectroradiometer was corrected by a matrix inversion approach. The relative expanded uncertainty (k = 2) for the scale is from 3.3% to 5.7% depending on the wavelength range. We also evaluated the contributions of the wavelength calibration and the bandpass function to the measurement of the total spectral radiant flux of typical white LEDs against the 2π standard LED. Our results demonstrate that the 2π standard LED achieves uncertainties comparable to those of a conventional standard lamp, within a practical wavelength range for LED measurements. These results show that the 2π standard LED is a useful transfer standard for the realization of the total spectral radiant flux scale and for evaluation of the total luminous flux of LEDs in 2π geometry.

Research on Performance Evaluation and Optimization Theory for Thermal Microscope Imaging Systems

“…Among them, ds 0 and ds 1 represent the microfacets of the object to be measured and the detector respectively, n 0 and n 1 represent the refractive index of the object space and image space respectively, 2u 0 and 2u 1 respectively represent the opening angle of the micro-unit of the object to be measured and the micro-unit of the detector of the optical system, l and l represent object distance and image distance, respectively, τ 0 represents the spectral transmittance of the optical system, d 0 and d 0 represent the diameter of the optical system in object space and image space, respectively. The radiant flux emitted by the micro-space element ds 0 in object space to a lens with an aperture d 0 can be expressed as [30]…”

The effects of silica-coated Y2O2S:Eu3+ red phosphor on the lighting properties of the light-emitting diode

“…A white LED can be made by precoating the phosphor combination of RGB phosphors above a ultraviolet (UV) LED die, or phosphors emit green and red light above a blue-color LED chip [6]- [8]. The favorable RGB phosphors for tricolor close-UV Indium gallium nitride-light-emitting diode (InGaN-LED) chips were Y2O2S:Eu 3+ , ZnS, and BaMgAl10O17Eu2 + [9], [10]. Unfortunately, the red phosphor Y2O2S:Eu 3+ exhibits lower photoluminescence (PL) intensity than the other green and blue ones, leading to the need for a  ISSN: 2302-9285 combination of phosphor with a huge number of red phosphors for proper hue rendering performance.…”