Influence of refractive index gradient on aero-optic imaging deviation

Aero-optical imaging deviation results in the boresight error which adversely affects the airborne imaging applications such as detection, guidance, navigation, and so on. The influence of refractive index gradient on aero-optic imaging deviation was studied. Firstly, The flow fields under different flying conditions were computed by the Reynolds-averaged Navier-Stokes method. Then the Gladstone-Dale relation was used to convert the mean density field into the refractive index field. After that, refractive index gradients whose absolute value below the selected threshold were set to zero and the new refractive index field was reconstructed. At last, ray tracing was performed via the Snell algorithm to obtain deflection angles and gradients along the ray trajectory. The simulation results show that the imaging deviation is closely related to the refractive index gradient, as the gradient increases, the imaging deviation also increases, and the high refractive index gradient region is the main reason for aero-optic imaging deviation.