Quasioptical system design

摘要

The development of active THz cameras with the potential for video-rate operation is an emerging and exciting research field. With our currently realized 645 GHz system we achieve scan rates of a few seconds with a one-pixel heterodyne detector and two-dimensional fast rotational scanning. The active illumination allows to resolve the object topography with subwavelength resolution. Within the next evolution step we will realize an active 812 GHz system incorporating a 1×32-pixel heterodyne detector array with one-dimensional scanning. This will allow video-frame-rates for images (amplitude and phase) with approximately 2000 pixels. But for large fields of view the quasioptical system must be optimized to minimize the aberrations inherent in all optical systems. We show, with the use of the optical software package Zemax, how to design, simulate and optimize such quasioptical systems for the one-dimensional 1 × 32-pixel heterodyne detector array. The resulting quasioptical system is diffraction-limited over the field of view (20 cm × 30 cm) at the design working distance of 4 m and has an adjustable focus optics for distances from 2 m up to 6 m.