LED filament standard lamp for total luminous flux with uniform spatial distribution

Abstract

To measure the total luminous flux emitted by a light source, the standard lamp which provides an absolute value of the total luminous flux is used with a sphere-photometer. Many institutes have developed their standard lamps based on LED. However, it is difficult to acquire uniform light distribution like the traditional incandescent lamps. To solve this problem, a novel LED filament standard lamp for total luminous flux is developed. First, a luminous intensity distribution model of a single LED filament is established. Based on this model, a method to calculate the luminous intensity distribution of multiple LED filaments is derived. To evaluate the uniformity of a light source, a spatial distribution uniformity index is introduced. Second, the spatial distribution uniformity index of the developed standard lamp is calculated by simulation and the optimal design is obtained. Experiment shows that the LED filament standard lamp for total luminous flux with the optimal design obtained uniform luminous intensity distribution in 4π geometry.