对两个不同光栅形成的Lau条纹分布进行了理论分析与实验研究。一般用于推导Lau条纹强度分布函数的方法比较复杂，其中基于交叉谱密度函数推导Lau条纹强度分布函数的方法相对简单。对该方法推导两个全同光栅Lau条纹强度分布函数的过程进行了仔细研究，并寻求将该方法进一步推广应用于两个不同光栅。探讨了该方法在光栅常数相同但占空比不同的两光栅情况下的适用性，并获得了光栅位置前后互换两种情况下简化的Lau 条纹强度分布函数，理论计算得到了实验结果的验证。因此，基于交叉谱密度函数的部分相干光理论可用于推导光栅常数相同、占空比不同的两个光栅的Lau 条纹分布函数。

The field distributions of Lau fringes for two different gratings are theoretically and experimentally investigated. The majority of the methods that are used to deduce the intensity distribution function of the Lau effect are rather complicated, among these, the method based on the cross-spectral density function is relatively easy. The process of deducing the intensity distribution function of Lau fringes generated by double identical gratings is studied based on the method, and the method is tried to be applied in a more general situation, two different gratings. The feasibility of the method in the situation of two gratings with the same grating constant but different duty ratios is discussed, and the simplified intensity distribution functions of two cases, in which the arranged positions of the two gratings are swapped, are achieved. The theoretical predictions are well demonstrated by the experimental results. Thus, the partially coherent theory based on the cross- spectral density function also works in the situation with two gratings of the same grating constant and different duty ratios.