Enhanced Vortex Phase Imaging for Millimeter-Wave Focal Plane System

Obtaining clear object images with high resolution is crucial for millimeter-wave (MMW) detection and sensing. This work investigates a general vortex phase imaging method for planar reflective objects, which can significantly enhance the lateral resolution in the MMW focal plane imaging (FPI) system. For an arbitrary reflective object, the convolutional imaging process based on vortex modes is theoretically analyzed. Meanwhile, an enhancement effect of the specific vortex mode caused by the orbital angular momentum (OAM) orthogonality is discussed. Expressions of the point spread function (PSF) and the image function theoretically indicate that the specific vortex mode that matches the object structure well can provide more imaging information. An efficient method combining diffraction integration and full-wave simulation is used to analyze the performance of this vortex phase imaging, and a significant resolution improvement is achieved. Additionally, an experimental system based on focal plane scanning is developed to verify the outcome of vortex imaging. Measurement results are in good agreement with the simulation results, exhibiting an excellent imaging performance with the lateral resolution reaching <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.48\lambda _{0}$</tex-math> </inline-formula> at 80 GHz. The proposed method suggests a massive potential in making use of scattering vortex spectrum, which would extend its application to other imaging systems.