||Verifying Calibration Effectiveness and Simulation Exactness in Comparison between Measurement and Simulation on Optical Properties in Integrating Sphere
||Uh-Chan Ryu ; Yong Wook Lee
|| LED Luminaire Measurement ; Integrating Sphere ; Self-Absorption Calibration ; CRI ; LM-79-08
||In measuring optical properties of lighting with a colored surface using an integrating sphere, it is necessary to calibrate out the variations caused by the surface color as recommended in the IES LM-79-08. Assuming hemispheres as non-fluorescent surfaces of test samples such as LED lamps, LED luminaires, etc., the sizes and the colors of the hemispheres are changed to give variations of the optical properties tested in the integrating sphere. Real measurement data and simulation results for a 0.5-m diameter integrating sphere were compared to give another simulation for a 2-m diameter integrating sphere. Calibration effectiveness will be shown in terms of total luminous flux (TLF), xy color coordinates, correlated color temperature (CCT) and color rendering index (CRI) in a 0.5-m diameter integrating sphere. As the hemisphere diameters are increased from 3cm to 20cm and those colors are varied, TLF decreased up to 61%, and CCT increased from 3452K to 4366K. CRI was raised by 11 without calibration. The deviations of TLF, CCT and CRI were decreased to less than 5%, 22K and 0, respectively, with the calibration procedure, even if the hemisphere sizes were increased up to 0.2m. This implies that a proper calibration procedure for an integrating sphere assures accurate measurement for large-sized samples.