为了进一步诊断反演出基片及光学元件中杂质缺陷的形态和尺寸，应用Bobbert-Vileger(BV)理论建立两种缺陷粒子的复合光散射模型，通过对场进行矢量球谐函数展开，对基片上缺陷粒子的光散射问题展开讨论，对散射场及微分散射截面进行推导求解。同时将数值计算结果退化为球形粒子与采用扩展Mie理论方法所得结果做了比较，二者吻合较好。通过数值计算考察了不同材质下，形变对微分散射截面的影响。结果表明，金属缺陷的散射更易受形变的影响，而介质缺陷受形变的影响很小。当球缺靠近基底的情况下，微分散射截面受散射角的影响较大；球缺背离基底时，几乎和球形粒子散射曲线重合,因此通过对微分散射截面的计算可以定位反演出球缺的位置和材质。

In order to accurately identify the size and material of contaminants about the wafers and optical elements, the scattering model about two kinds of slightly non-spherical particles on wafer is established by the Bobbert and Vileger (BV) theorem. The scattering process is analyed and the scattering coefficients are derived through expansion vector spherical harmonic function. The figure about the differential scattering cross setion (DSCS) of a non-spherical particle is calculated, which is compared with that from extended Mie. The results are coincidence, which proves the validity of the method. The effect of different material non-spherical particle deformations is reviewed by the calculation. The result shows that the effect of the dielectric is smaller than that of the metal. Therefore, the material of the defect and the shape can be extracted by calculating the DSCS.