Radial Distortion in Silicon Lens-Integrated THz Cameras

Silicon lenses are widely employed to turn a terahertz (THz) focal-plane array into a THz camera. For the first time, we have identified the type of radial distortion caused by such lenses. To this end, we measured all single-pixel far-field radiation patterns of a 15-mm diameter 2.75-mm extended hemispherical silicon lens-integrated 32×32-pixel CMOS camera at 0.652 THz. From this, a beam incidence angle grid has been generated, indicating barrel distortion. The measured beam incidence angle is compared to a previously published closed-form relation between scan angle and feed position for extended hemispherical lenses. The presented results are essential for all beam switching applications based on dielectric extended hemispherical lenses with an elliptical extension realized in the lens center.