平面LED(light-emitting diode)阵列远场条件是实现其光度学参数正确测量的前提, 为了确定不同平面LED阵列的远场条件, 基于点光源发光强度的测量原理建立了面光源光轴上的不同距离下照度与距离平方乘积的函数关系模型, 用其表征面光源光轴上光场的分布规律。在此基础上利用照度平方反比定律, 以及平面LED阵列远场的近似条件, 推导出了平面LED阵列远场条件的理论计算模型。以某款LED日光灯和LED射灯为对象, 搭建了相关实验测量系统, 对其光轴上的光场分布规律以及远场条件进行了实验验证。结果表明, LED日光灯和LED射灯在光轴上的光场实验分布曲线与理论分布曲线基本吻合, 并且LED日光灯和LED射灯的理论远场条件分别为测量距离大于或等于LED阵列尺寸的4.4倍和14.6倍, 实验远场条件分别为测量距离大于或等于LED阵列尺寸的5.1倍和17.7倍, 实验和理论计算的远场条件基本一致, 从而验证了LED阵列远场理论模型的正确性。

The far-field condition of LED array plays a foundational role in measuring its photometric parameter. In order to determine the far-field condition of different LED arrays, a function of the product of illumination and distance squared based on the measurement principle for luminous intensity is given, which is used for the characterization of distribution of light field on optical axis. Then, the far-field condition model is deduced based on the inverse-square law and the far-zone approximation of LED array. Finally, taking the LED fluorescent lamp and LED spot lamp for example, the distribution of light field on optical axis and the far-field condition are verified experimentally. The results show that the experimental distribution of light field on optical axis fit the theoretical calculation very well. The calculated far-field conditions for LED fluorescent lamp and LED spot lamp are 4.4 and 14.6 times size of its LED array respectively. While the corresponding values for the experimental data are 5.1 and 17.7 times, which are substantial agree with the theoretical calculated values. The theoretical model of far-field condition for LED array is therefore verified.