Brief introduction:
Different from the traditional light source, the measurement of luminous flux of LED light source poses a great challenge to the accuracy of the equipment in the process of measuring luminous flux with integrating sphere. For one thing, LEDs are generally more directional than traditional light sources, and do not emit light uniformly throughout the space. This feature leads to uneven distribution of direct light on the surface of the integrating sphere. This uneven distribution will result in different LED direct light with different reflection characteristics of the detector. Since the position of the detector and the position of the baffle are fixed, the immediate property of the various reflection distributions is signal fluctuation. In the ordinary test system, there are differences between the LED with different emission angles, and the same LED with different placement directions has the same emission at different positions. Even if the rated luminous flux is the same; The actual measurements are different. According to customer verification results, the influence of the LED placement direction of the ordinary LED test system on the luminous flux measurement results is always more than 50%(the difference between the maximum signal and the minimum signal of the same LED measured in different directions).

On the other hand, the LED test system usually uses the halogen tungsten lamp as the standard light source. Compared with the LED, the standard lamp used has a great difference in appearance, lighting distribution characteristics and spectral characteristics. Therefore, the difference between the two should be corrected by absorption coefficient.

Source: China Lighting Network