两种稀疏孔径系统的成像研究

Imaging research of two kinds of sparse-aperture systems

介绍一种由九个子镜构成的复合三子镜稀疏孔径系统及其结构形式。将复合三子镜和同样由九个子镜构成的典型GOLAY9稀疏孔径系统进行比较来研究两种稀疏孔径系统的成像情况。通过比较它们的结构特点与调制传递函数，并计算两种稀疏孔径系统的等效直径和实际等效直径，对不同填充因子的两种稀疏孔径模拟成像和维纳滤波，用图像的标准差和对比度指标对两种系统的成像像质进行评价。结果表明：在调制传递函数（MTF）的最大值方向，除归一化频率在0．55～O．65以外的空间频率处复合三子镜I型的MTF明显高于GOLAY9的MTF。当填充因子≥20％时，复合三子镜I型和GOLAY9的等效直径和实际等效直径基本接近。在空间频率24～45lp／mm处，图像对比度复合三子镜I型优于GOLAY9，复合三子镜整体性能与GOLAY9相近，且复合三子镜在结构排列上具有对称易装调的优点。

A sparse aperture configuration named dual three sub-apertures composed of nine sub-apertures was introduced and the models of configuration were described. The dual three sub-apertures system was compared with the GOLAY 9, which composed of nine sub-apertures, to research the imaging of two kinds of sparse aperture systems. The comparison of their characteristics and modulation transfer functions （MTF） with the dual three sub-apertures and the GOLAY 9 were given. The equivalent diameters and the practical equivalent diameters of two kinds of sparse aperture systems were calculated, and the image simulations and Wiener filtered images of two kinds of sparse aperture systems with different fill factors were shown. Their image quality was evaluated with their standard deviation （std） and image contrast. Through the comparison, it is shown that the MTF of the dual three sub-apertures is obviously higher than that of the GOLAY 9 at the direction of maximal MTF except at the normalized spatial frequency between 0. 55 to 0. 65. When the fill factor is not smaller than 20%, the equivalent diameters and the practical equivalent diameters of two kinds of sparse aperture systems are almost equal. The image quality of the dual three sub-apertures is better than that of the GOLAY 9 at the spatial frequency between 24-45 lp/mm. The performance of the dual three sub-apertures is almost same as the GOLAY 9. The dual three sub-apertures system has the advantages of symmetric configuration and easy fabrication.