Different from the traditional light source, the flux measurement of LED light source in the process of using integrating sphere to measure the luminous flux poses great challenge to the accuracy of the equipment. On the one hand, compared with traditional light sources, leds are generally more directional and do not emit light uniformly throughout the space. This feature makes the direct light distribution of LED on the surface of the integrating sphere uneven. This uneven distribution will result in different LED direct light with different detector reflection characteristics. Since the position of detector and baffle are fixed, the direct performance of various reflection distributions is signal fluctuation. In the common test system, leds with different lighting angles are different, and the same LED is placed in different directions and has the same emission at different positions. Even if the rated luminous flux is the same; The actual measurements are different. According to the customer's verification results, the influence of the LED placement direction of the ordinary LED testing system on the luminous flux measurement results is always more than 50%(the difference between the maximum and minimum signals of the same LED measured in different directions).

When measuring different LED luminescence angles, the distribution of direct reflection has different influence on the detector due to the difference in the distribution of the inner surface of the integrating sphere, which directly affects the difference in the measurement accuracy

On the other hand, the LED test system usually USES halogen tungsten lamps as the standard light source. Compared with the LED, the standard lamps used are quite different in appearance, lighting distribution characteristics and spectral characteristics. Therefore, the difference between them should be corrected by the absorption coefficient.