When the flight with an optical window is flying in a high speed, the temperature and the refractive index of the air
around it will be changed because of the friction, and this will make the image on the detector blurring and shifting,
which will degrade the detecting precision greatly. This paper chooses a typical kind of model for the research. Ansys
is used in order to gain the temperature field around the hood in real size instead of an assumptive and approximate
model. So the refractive index of the air could be worked out. On this basis, the offset and the blur of the image could be
figured out using the ray tracing method. Considering of the characters of the grid points distribution and the huge
amount of data exported from Ansys, self-adaptive step length tracing method and interpolation method are used in
order to shorten the run time and guarantee computational precision at the same time instead of the adaptive variable
step method and complicated gradient algorithm. In this study, 3D simulation and programming results under different
flight conditions are discussed. The results clearly show the relationship between the image quality and the flight
altitude, wavelength and focal length.
|