Method for analysing luminous intensity of light-emitting diodes

Abstract

Light-emitting diodes (LEDs) have built-in lenses that enable spatially limited light beams. The use of lenses increases the luminous intensity levels, but complicates accurate LED intensity measurements. A novel method for determining the luminous intensity of the LED is proposed. The method based on a modified inverse-square law describes the behaviour of an LED in terms of its luminous intensity, the radius of the virtual source and the location of the virtual source. The applicability of the method was tested for 17 LED types with different packages, angular intensity distributions and power levels. When applying the new method to the measurement data, instead of the inverse-square law of the point source, the distance dependence of apparent LED luminous intensity of up to 47% reduced to statistical variation of less than 1%.