Effects of Internal Spatial Response Distribution Function of the Integrating Sphere on Total Luminous Flux Measurements

In typical measurements of total luminous flux using an integrating sphere, non-uniformity of the spatial response distribution function (SRDF) inside the sphere can cause measurement errors. It is important to analyze the SRDF in order to evaluate any potential uncertainty of the integrating sphere measurements. If the SRDF can be quantified, it may be possible to reduce the measurement errors. Our findings in this study showed that when the light distribution of the test light sources are different, a difference in the total luminous flux measurement occurs due to the difference in the internal SRDF of the integrating sphere. We also found that it is possible to quantify the effect of SRDF on the total luminous flux measurement by examining the opening angle of the luminous intensity distribution of the light source.