Characteristic analysis of aspheric quasi-optical lens antenna in millimeter-wave radiometer imaging system.

Quasi-optical imaging systems require low blurring effect and large depth of focus (DOF) to get an acceptable sharpness of the image. To reduce aberration-limited blurring, the aspheric convex plano lenses with an aperture diameter of 350 mm are designed in W-band. We analyzed theoretically and experimentally the millimeter-wave band lens characteristics, such as beam spot size, spatial resolution (SR), and DOF, via f-number. It is first used to verify the DOF through f-number in the system-level test with the developed W-band radiometer imaging system. We have confirmed that the larger f-number of quasi-optical lens leads to a larger DOF but a lower SR.