研究了三子镜结构与由6个子镜构成的三臂形稀疏孔径结构，分析了两种孔径结构的特点。从光瞳函数出发推导出三子镜与三臂形稀疏孔径结构的调制传递函数(MTF)解析式，在此基础上用Matlab软件模拟两种稀疏孔径的MTF图像，并对模拟结果进行分析与比较。结果表明：两种结构的MTF都呈均匀正六边形分布；填充因子同为22%时，三子镜结构在归一化频率0.3附近MTF出现零点，三臂结构在归一化频率0.15处出现零点；随着填充因子的增加，三子镜与三臂结构的MTF值提高，三臂结构MTF曲线比三子镜结构起伏小，但MTF值也小，信息丢失较多。ZEMAX模拟成像及图像增强结果表明三子镜整体成像效果要优于三臂结构。

Two kinds of sparse aperture systems of three sub-apertures and three arms sparse aperture are researched, and the characteristics of this two kinds of sparse aperture configurations are analyzed. Modulation transfer functions (MTFs) of the three sub-apertures and three arms configurations are derived from the formulas of the pupil functions．Based on the formulas of MTF, MTF curves are simulated by Matlab. Comparing the MTFs of three sub-apertures and the three arms aperture, it is shows that MTFs of two kind of configurations are all arranged to uniform hexagon. When the fill factors are both at 20%, the MTFs of three sub-apertures and three arms aperture have zero frequency at the normalized spatial frequencies of 0.3 and 0.15, respectively. The MTFs of the two sparse aperture configurations become larger with the increase of the fill factor. The MTF curve of three arms aperture is more stable than that of three sub-apertures, but with smaller MTF values. As a result, three arms apertures lose more information. The results of imaging simulation and image enhancement of two sparse aperture configurations show that three sub-apertures configuration outperforms three arms aperture in imaging quality.