Limitation Study of Integrating Sphere for Directional Light Source

Abstract

Integrating spheres are widely used for the photometry measurement of light sources. Their size and geometry influence the measurement uncertainty such as the baffle geometry inside, which avoids the first incident light from the light source. Different set-up conditions of the directional light source, including LED light-bar and surface light source, result in different luminous fluxes. We have simulated directional light sources mounting at the center of sphere to proceed the feasibility study of directional light source in different mounting conditions. By varying the types of directional light source, the geometry of integrating sphere, the baffle condition, the size of sphere, and the absorptivity of the light source, we found the optimal measurement conditions. The result in this study shows that we could use the limitation of integrating sphere to measure the directional light source, and decrease the measurement uncertainty.