Quantum Efficiency Measurement of Lamp Phosphors in Accordance with Radiometric Standards

To measure the quantum efficiencies of lamp phosphors, a JCSS (Japan Calibration Service System) traceable measurement method that uses a polychromator, with improved optical design to reduce stray light, and an integrating sphere has been developed. To verify the measurement accuracy of this method, a monochromator, which has a 0 - 45°incident optical system, was used. The BRDF (Bidirectional Reflectance Distribution Function) of the phosphor was measured by a goniophotometer. A comparison was made between these JCSS traceable measuring devices on the 260-400 nm wavelength characteristics of the internal quantum efficiency of the blue phosphor BAM  (BaMgAl10O17:Eu2+) , which has excitation characteristics up to 400 nm. The results agreed within 4 % of the difference of the measured values. This is a good agreement considering that it was a composite measure and that the uncertainty of the spectral irradiance standard in the spectral region is lower than 3 %. It has also been established that the proposed method using a polychromator and an integrating sphere shows sufficient measurement accuracy.