面光源的远场条件分析

Far-Field Condition Analysis of Surface Light Source

对于有一定尺寸的面光源，在满足远场条件下，对其空间光强分布进行测量是保证照明设计中配光效果准确性的前提。根据发光面的实际组成情况，将面光源分为连续型和离散型两类进行光学建模分析，并针对最常见的平面和曲面光源，分别计算了圆形、矩形、环形、半球面和半柱面所对应的远场距离。结果表明，面光源的远场距离与发光面的形状关系密切，传统的5倍定律仅适用于连续型的圆形和矩形面光源，且在同等形状及尺寸下，连续型面光源的远场距离通常比离散型面光源的小。

For surface light source with a certain area, a prerequisite of ensuring the accuracy of lighting effects in optical design is that the intensity distribution should be measured under far-field condition. Surface light source is divided into continuum model and discrete model for discussion, according to the practical composition of emitting area. The far-field distances of several typical flat and curved surface light sources, such as the round, rectangular, annular, hemispherical, and semi-cylindrical sources are calculated. The results show that the far-field distance of surface light source is closely related to the shape of its emitting area. The classical five times rule is only valid for continuous round and rectangular sources. The far-field distances of continuous sources are smaller than those of discrete sources with the same shapes and sizes for most situations.