Broadband THz, extended depth of focus imaging based on step phase mask aided interferometry

This work describes the realization of an extended depth of field (EDOF) in pulsed THz imaging systems using a step phase mask (SPM) attached to the objective lens. The SPM was designed to generate an EDOF compared to Gaussian broadband sources. This imaging property is demonstrated using a resolution target illuminated by broadband THz beams. An imaging depth improvement factor of 1.5 is demonstrated. In this paper we present the element design method together with numerical and experimental results.