Design of an absolute spectral emission power distribution measurement system in the UV-Vis-NIR region using an integrating sphere head and spectrometer
We propose the design of a measurement system capable of obtaining the spectral power distribution (SPD) of radiation in units of spectral flux by correlating independent measurements from a spectrometer and an integrating sphere radiometer. A 4-inch integrating sphere head was utilized to perform absolute radiometric measurements. Spectral emission from commercially-available LEDs emitting at a peak wavelength of 517.15 nm and radiant flux of 13.44 mW were recorded by two different spectrometers and analyzed. The efficiencies of the devices in generating radiation were determined by monitoring the current and voltage during the experiment. Plots of the spectral flux corresponding to the two spectrometers were compared to observe the effect of varying spectral response functions. These were then integrated over the spectral range of measurement, giving radiant flux readings of 12.90 and 12.73 mW, with percent deviations of 4.02% and 5.28%, respectively. Results also showed that the light sources emit visible radiation with luminous flux of 7.01 and 6.88 lumens through the luminosity function, which correspond to power efficiencies of 21.84% and 23.29%, and luminous efficacies of 118.68 and 125.90 lumens/Watts.