Metrological Analysis of Integrating Sphere Photometers for LED Luminous Flux Measurement

Abstract

A comparative metrological analysis using mathematical models of three integrating sphere photometer schemes, for LED luminous flux measurement, was held. Each model takes into account the main design parameters of the photometer, typical values of which are used in the calculations. It's shown, that for given initial conditions, the greatest contribution to the total error for schemes with LED on the wall of sphere and in the center of sphere introduces instability of sphere reflectance coating, and for the scheme with LED in front of entrance aperture of sphere, for total luminous flux measurement, – instability of the distance to the diaphragm. In general, the highest accuracy for total luminous flux measurement have a scheme with LED in the center of the sphere, somewhat lower –  a scheme with LED on the wall of sphere, and the lowest – a scheme with LED in front of input aperture of the sphere. The substantiated recommendations on the best practical application of each of the schemes are given. Also, for all schemes dependencies of the total relative error on the primary errors of basic design parameters, that can be used to select the optimal scheme of the photometer and selection of optimal values of design parameters are given.