Resolution Limits of Hyper-Hemispherical Silicon Lens-Integrated THz Cameras Employing Geometrical Multi-Frame Super-Resolution Imaging

In this paper, we present a comprehensive study to understand the image formation and associated resolution limitations of hyper-hemispherical high-resistivity floating-zone silicon (HRFZ-Si) lens-integrated terahertz (THz) cameras, and we extend this understanding into THz super-resolution imaging applications. Along these lines, design trade-offs between fixed field-of-view (FoV) and frequency-dependent angular resolution of such cameras are also discussed. The present study is based on investigations of a CMOS THz camera that is made of a 3232-pixel focal plane array (FPA) sensor and a 15-mm diameter objective hyper-hemispherical HRFZ-Si lens. Two experiments are performed at 0.652 THz. In the first experiment, THz geometrical multi-frame super-resolution imaging is performed to demonstrate that such cameras can always reach the maximum achievable resolution in their entire operating bandwidth. In the other, a full radiation pattern scan is performed to measure aberrations of off-axis displaced pixels in order to give a comprehensive picture of the camera's resolution behavior across the full camera frame. The investigations and discussions are general in nature and should be applicable to any broadband THz camera.