中文摘要：

扩展源发出的光经过平均密度场传输的成像还没有被充分地研究。当某个扩展源与某个侧窗头罩内的成像系统相距较近时，用光线追迹和傅立叶光学研究该扩展源发出的光经过平均密度场传输的成像特性。研究发现扩展源上不同点光源的成像偏移角和成像模糊指标有差异。因此采用综合偏移指标、综合模糊指标来分别描述扩展源成像的总体偏移、模糊情况。研究发现：当扩展源和成像系统的相对位置不变，平均密度场相对成像系统分别沿流向、展向、光轴方向平移时，上述两个指标均会发生变化。并且在这三种情况下这两个指标的变化情况各不相同。对上述现象的原因进行了深入的分析。在工程设计中，该研究有助于选择成像系统相对窗口的合适安装位置。

英文摘要：

Extended source light transmission through mean flow field and imaging have not been fully studied. When an extended source is closed to an imaging system in a forebody with a side-mounted window, light emitted by this extended source passing through the mean flow field and imaging are studied with ray tracing and Fourier optics. It is found that imaging deviation angles and imaging blur indexes of different point sources of the extended source are different. So integrated deviation index and integrated blur index are adopted to describe entire deviation and blur conditions of the extended source imaging, respectively. It is also found that when the relative position of the extended source and imaging system is invariant, and the mean flow field moves along flow, expansion and optical axis directions relative to the imaging system respectively, integrated deviation index and integrated blur index vary. Varying conditions of the two indexes are different among the three moving conditions. The reasons of these phenomena are deeply analyzed. In engineering design, this research may be beneficial to selection of a proper location of the imaging system relative to the window.