光束合成是突破单路激光功率限制、获得高功率激光输出的重要手段。以亮度为判据，对不同光束合成方法的合成效果进行理论研究，给出了激光光束合成效果的预评价方法。分析了亮度、光束质量因子和Strehl比3个描述光束质量的重要参量之间的关系，给出了亮度与Strehl比的关系式，据此得出了相干合成系统与光谱合成系统亮度的定标放大公式，并对两种系统的功率与亮度定标放大能力进行了比较。

Beam combination is an important method to break through single laser power limit and obtain high power laser output. Brightness is taken as the criterion, and theoretical investigation about the combination effect of different methods is carried out. The pre-evaluation method of laser beam combination effect is given. Relationship among three important parameters used to describe beam quality, including brightness, beam quality factor and Strehl ratio, are analyzed. The formula describing the relationship between brightness and Strehl ratio is given, and brightness scaling magnification formulas of coherent beam combination system and spectral beam combination system are obtained. The power and the brightness scaling amplification capability of the two systems are compared.