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To satisfy environment requirement of infrared search and trace optical system, an infrared diffractive/refractive hybrid optical system in 3.7–4.8μm with 11.42° of field of view for passive athermalization is presented. The system is consisted of three lenses, including two aspheric surfaces and a diffraction surface, which has only two materials Ge and Si. The optical system has compact structure, small volume and light weight. The image quality of the system approaches the diffraction limit in the temperature range −80°C to 160°C. It is compatible with staring focal plane array which has a format of 320×240 and the pixel pitch of 30μm. The system need not move the compensated lens repeatedly to obtain the best images from −80°C to 160°C and enhances the performance of target tracking and recognition. [ABSTRACT FROM AUTHOR]

Based on the most advanced staring focal plane array which had a format of 640×480 and the pixel pitch of 15μm, a set of all-sphere midwave infrared ahermalization optical system was designed. The working wavelength was in 3–5μm, the full field of view was 8.58°, the relative aperture was 1/2, the efficient focal length (EFL) was 80m. The opticalsystem consisted of four lenses with three kinds of material – Ge, ZnSe and Si. All surfaces were sphere, which was easier to process test, making the cost inexpensive, and it could avoid using diffractive surface and aspheric surface. The image quality of the system approaches the diffraction limit in the temperature range −60°C-180°C. The design results proved that, the high resolution midwave infrared optical system had compact structure, small volume, high resolution and excellent image quality, meeting the design requirements, so that it could be used for photoelectric detection and tracking system. [ABSTRACT FROM AUTHOR]