The Methodic Design Of The Airbore IR Aspheric Hybrid Refractive-diffractive System With Large Aperture And Focus

Based on analysing status and developing trend of at IR optical system home andabroad, theoretical approach of large diameter IR optical system that includdetermination of IR optical material, representation of aspheric surfaces and binaryoptical elements, order aberration theory, problems of design and processinginspection technology are studied according to special requirements (widetemperature range, large diameter, etc) of airborne IR optical system.Design methods of airborne IR optical system are proposed, includes selection ofthe basic parameters of optical system, solving of original paremeters, and evaluatingmethod of image quality. A airborne IR aspheric hybrid refractive-diffractive opticalsystem with1000mm focus and250mm diameter is designed. Aspheric surface isadded to traditional hybrid refractive-diffractive optical system, whose angle of visionis±0.3oand range of working tempreture is-40~60℃. The variation range of imagequality is small within the scope of working tempreture while the system is optimizedby Zemax. The MTF is keeping above0.4while spatial frequency is10(lp/mm), anddiameter of Airy disk keeps smaller than20μm. The design compared to traditionalIR optical system have advantages such as well adaptability, large range of workingtempreture, smalle change of MTF, close to diffraction limit, and easy to processingand assemble.Coaxial three-mirror system, Pittsburgh cutting structure system and hybridreffractive-diffractive system are designed and compared. Coaxial three-mirror systemcan get better image quality and smaller size, but it is inconvenient for fitting becauseof its obscuration. Pittsburgh cutting structure is well after optimized, but this systemis too large and heavy, and mirror’s materials changed are variable according todifferent tempreture. While image quality of hybrid reffractive-diffractive system issatisfied and the system is small and light, and suitable for airbored optical system.The obtained results show that the airborne aspheric hybrid reffrective-diffractiveIR optical system is satified the given technical index. The methd could be applied toIR optical system while environment is severve in the air. This work is significant andplays an important role in developing high-performance airborne infraied system.