Optical design of a multiscale imager in 8 to 12 μm spectral band using monocentric lens

Abstract

Long-wave infrared (LWIR) imagers utilize self emission in 8 to 12 μm spectral band to image objects passively even during night time when the reflected radiation is not available. These are mostly used for surveillance purpose requiring large field of view (FOV). Achieving wide FOV and high-resolution image of megapixel (MP) order requires higher format detectors that are not readily available in LWIR. Further, the optical performance gets limited by fundamental limits of space bandwidth factor. An LWIR monocentric multiscale imager is proposed. The designed lens operates at f / 1.5 with effective focal length (EFL) of 50 mm and effective pixel count of 3.9 MP. It covers 80 deg × 16 deg FOV over five detector arrays. We discuss the basics of multiscale imaging, the specific issues in LWIR band and their mitigation, optical design approach and finally analyze the optical performance of the designed lens.