Design of a compact off-axis four-mirrorobjective system (OFOS) for a thermal camera

The optical design of a compact off-axis four-mirror objective system (OFOS) of a thermal camera for a syndromic surveillance system that captures bioclinical signals, like temperature, directly related to the physical symptoms of the COVID-19 disease through thermal images is presented. The OFOS design works on wavelengths of 7.5–14 µm, with an f-number of 4, and a field of view (FOV) of 24×4 deg.