Numerical study using angular spectrum propagation model for aero optical imaging

When the interceptors with optical detector onboard fly at supersonic speeds, aero-optical effects (AOEs) will occur and have bad influence on the accuracy of image navigation and eventually decrease the operational effectiveness. Thus, it is crucial for precise image navigation to do research on prediction of the performance of aero optical imaging. This paper employs a method based on the model of angular spectrum propagation to study the light transmission through the supersonic flowfields and aero optical imaging. First, the density fields are translated into the refractive index fields through the Gladstone–Dale (G–D) relationship. In this paper, each CFD grid is viewed as a uniform and isotropic cell, and it is assumed that the optical waves are propagating cell by cell. According to the angular spectrum propagation, each CFD grid is thought of as a linear spatial filter (LPF), and the supersonic flowfields are regarded as the combinations of these LPFs. The different spatial frequencies brought about by the different densities are used to analyze the influences of the density distribution on the light propagation. The proposed method can calculate the optical transformation function (OTF) and directly use it for modeling the aero optical image. In the end, the aero optical images are simulated and the centroid offsets of aero optical imaging are calculated. The results show that the proposed approach is reasonable.