Catadioptric optics for high-resolution terahertz imager

Abstract

INO has developed infrared camera systems with microscanning capabilities in order to increase image resolution. It has been shown in previous works that the image quality may be improved even if the pixel pitch is smaller than the point spread function. [1] This paper introduces a catadioptric optics system with fully integrated microscan for improved resolution in the THz band. The design, inspired by the INO's HRXCAM infrared camera core and adapted for terahertz wavelengths, includes two mirrors and one refractive element. It has a 11.9 degree full field of view and an effective F-number of 1.07 over a wide spectral range, from 100 µm to 1.5 mm wavelength. This diffraction limited optics is used to provide video rate high quality THz images. A THz camera, with 160 x 120 pixel and 52 µm pitch detector, is combined with the microscan objective to provide a 320 x 240 pixel image with a 26 µm sampling step.Preliminary imaging results using a THz illumination source at 118 µm wavelength are presented. A comparison between standard and microscanned images is also presented.