Optimum Quasi-Optical System Synthesis With Enhanced Depth-of-Field for Cross-Range Refocusing Terahertz Defog Camera

Abstract

A complex offset double-reflector configuration for focal-plane array (FPA) is presented, optimized for highresolution indoor imaging applications. The proposed quasioptical system utilizes a compact ellipsoidal Dragonian geometry due to its uniform scanning performance with a broad range of $\pm 10^{\circ}$ field-of-view (FoV). Fourteen beams can be scanned before reaching the 3dB scan loss limit; therefore, the number of active elements in the array increases, resulting in a higher EIRP. We demonstrate the design equivalence between a paraboloidal main reflector and an ellipsoidal one. The enhanced depth-of-field is obtained through generating a quasi-non-diffractive Bessel beam by an axicon. The system can scan the beam over 0.5 m in crossrange at a standoff range with less than a 3% increase of the half-power beam-width. A demonstrator was fabricated, and the defog experimental results confirm the predicted performance.