提出一种由九个子镜构成的复合三子镜稀疏孔径结构。给出该孔径的光瞳函数以及三种不同型的结构形式,并导出它的调制传递函数的解析表达式。对三种不同型的调制传递函数进行了分析比较,阐明复合三子镜三种结构各自的特点。通过数值计算给出复合三子镜Ⅰ型结构的最大截止频率和不同填充因子的等效直径。对不同填充因子下的复合三子镜进行模拟成像、加噪与图像重构,并用两种指标对不同情况下的图像进行像质评价。结果表明,复合三子镜像的空间分辨率,基本接近包围孔径像的分辨率,成像质量和信噪比随着填充因子的减小逐渐下降。经过维纳去卷积滤波,图像质量有所提高。复合三子镜具有结构灵活、易于装调的优点。

A sparse-aperture design named dual three sub-apertures, which is composed of nine sub-apertures, is proposed. The pupil function, analytical formulas of its corresponding modulation transfer function (MTF) and three configuration models have been given. The comparisons among the MTFs of three models are made. The features of three kinds of configuration of dual three sub-apertures is illuminated. The maximum cut-off frequency and equivalent diameters under the different filling factors of dual three sub-apertures for model Ⅰ are given by calculating. The image quality is evaluated by two kinds of method. The image simulations, noisy image restorations and reconstructuring image show that the image spatial resolution of dual three sub-apertures approaches the resolution of encircled aperture, the image quality degrades with the decreasing of filling factor. The image quality can be improved using Wiener filtering. The sparse-aperture system of dual three sub-apertures has the advantages of flexible configuration and easy fabrication.