Introduction: different from the traditional light source, the measurement of light flux of LED light source poses a great challenge to the accuracy of the equipment in the process of using integrating sphere to measure the light flux. On the one hand, leds are generally more directional than traditional light sources and do not emit light uniformly throughout the space. This feature makes the LED direct light distribution on the surface of the integrating sphere uneven. This uneven distribution will result in different LED direct light having different reflection characteristics of the detector. Since the position of detector and baffle are fixed, the direct property of various reflection distributions is signal fluctuation. In the common test system, there are differences in the leds with different lighting angles, and the same LED can be placed in different directions and emitted in different positions. Even if the rated flux is the same; The actual measured values are different. According to the customer's verification results, the LED placement direction of the common LED test system always has more than 50% influence on the luminous flux measurement results (the difference between the maximum signal and the minimum signal of the same LED measured in different directions).
When measuring the different light angles of different leds, the distribution of direct reflection on the detector is different due to the distribution difference on the inner surface of the integrating sphere, which directly affects the difference of measurement accuracy