Fig. 1. Schematic diagram of spectral transmittance testing apparatus of infrared optical system

Fig. 2. Schematic diagram of off-axis field producing vignetting equivalent model when filled with aperture

Fig. 3. Schematic diagram of off-axis field intercepted by upper edge of front surface of aperture

Fig. 4. Schematic diagram of off-axis field intercepted by lower edge of front surface of aperture

Fig. 5. Schematic diagram of off-axis field intercepted by lower edge of rear surface of aperture

Fig. 6. Schematic diagram of off-axis field producing halo equivalent model without filling with aperture

Fig. 7. Schematic diagram of reflected light being intercepted by aperture of main mirror itself

Fig. 8. Effect of vignetting caused by aperture position on measurement

Fig. 9. Effect of vignetting caused by distance between aperture and plane return mirror on measurement

Fig. 10. Measurement results when consistency in relative vignetting between actual and aerial measurements