Fig. 1. Horizontal angle θ_x and vertical angle θ_y of stray light incidence

Fig. 2. Rotation rules for modeling stray light source

Fig. 3. Scanning calculating flow diagram of the distribution of bivariate function PST with θ_x and θ_y

Fig. 4. Opto-mechanical model of the off-axis four mirrors telescope

Fig. 5. Gaussian scattering model of metal structure surface

Fig. 6. Distribution surface of two-dimensional PST with θ_x and θ_y

Fig. 7. Distribution curve of one-dimensional PST

Fig. 8. Ray path of stray light

Fig. 9. Structures to suppress stray light for the off-axis four mirrors system

Fig. 10. Distribution diagram of PST of the system with baffles