This paper contains the full design process of a wide-angle lens used for LWIR earth sensors from paraxial power allocation calculation to optimization of lens. The lens has a relative large image circle of 13mm, which is compatible with a 640×480 25μm uncooled FPA, and its full FOV is 180°. Its focal length is 4.177 and F number is 0.8. The f-theta distortion is less than 0.25%. By choosing chalcogenide glasses as lens material, the lens has a higher transmittance compare to Germanium lens. Also by analyzing the chromatic aberration of the lens, applying a DOE surface helps to improve the image quality, and pushes the modulated transfer function towards diffraction limitation.
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RongSheng Qiu, Wei Dou, JinYan Kan, Kun Yu, "Optical design of wide-angle lens for LWIR earth sensors," Proc. SPIE 10209, Image Sensing Technologies: Materials, Devices, Systems, and Applications IV, 102090T (3 May 2017);