Far-Infrared Fresnel Lens for Thermal Imaging

Abstract

We propose that thin and light-weighted silicon Fresnel lenses is suit for thermal imaging. We adopted a one-mask process with photolithography and inductive coupled plasma reactive ion etching (ICP-RIE) to fabricate silicon three-dimensional structure. Thermal image was taken with a Fresnel lens, which we designed with ray-trace method and fabricated with the three-dimensional (3D) fabrication process. Thermal cameras have been expensive because germanium lenses are difficult to be machined. Since the 3D fabrication process suits mass production compared with other method like multi-level lithography, competitive-price FIR optical systems can be realized.