简述了光学合成孔径成像系统的原理，合成孔径成像系统在获得高截止频率的同时，降低了系统的中频性能，在空域表现为点扩展函数次峰增加。然后运用两点分辨率和光学传递函数对衍射受限光学合成孔径成像系统的像质评价问题进行了分析，指出了瑞利判据、斯派罗准则和“门限”判据的不足，认为当点扩展函数次峰大于主峰的0.5倍时，合成孔径系统与单孔径系统相比将失去优势。以光学传递函数为标准，分析三孔径合成系统子孔径尺寸、相互间距与等效系统孔径尺寸之间的关系。当子孔径直径不变时，随着其所在圆半径的增大，实际截止频率先增大，然后减小。

The theory of optical synthetic aperture imaging system with emphasis on the characteristics of the spatial frequency is described. The cut-off spatial frequency is got higher at the cost of the mid-spatial frequency, and the sidelobes of point spread function (PSF) are higher. The image quality evaluation for diffraction-limited optical synthetic aperture imaging system is analyzed with two-point resolution and optical transmission function (OTF). The disadvantages of Rayleigh criterion, Sparrow criterion and threshold criterion are given. When the sidelobe is 0.5 times of the maximum, the imaging quality of synthetic aperture system is no better than that of the single aperture system. Based on the OTF, relations between the effective diameter of three operture system and pupil parameters including the diameter of sub-apertures and spacing parameter are analyzed. When the pupil diameter is fixed, practical cut-off spatial frequency becomes larger first, and then reduces with the augmentation of the distance between pupils.