折/衍混合消热差共形光学系统的设计

Athermal design for hybrid refractive/diffractive conformal optical system

为了满足共形整流罩光学系统无热化工作的要求,基于硅、锗和硒化锌3种材料以及制作于整流罩内壁的衍射面设计了采用折/衍混合消热差方法的红外成像共形光学系统。介绍了共形光学系统像差特性以及衍射光学元件的像差、温度及色散特性,提出了利用可消像散的衍射面结构的温度补偿能力来设计共形光学系统消热差结构的方案,并设计了应用于中波红外成像结构中的万向支架式共形光学系统。软件分析结果表明,该系统充分利用了衍射光学元件的位相补偿,热膨胀系数小和色散因子大等特点,在-40～70℃能够较好地保证±20°搜索观察视场中的成像质量,且所有观察视场中的MTF值均大于0.43。

In order to achieve the athermalization of conformal optical systms,an infrared imaging system was presented by using the hybrid refractive/diffractive elements made of Si,Ge,and ZnSe and a diffraction surface mounted on the dome’s inner surface.The aberration characteristics of conformal optics and the aberration,thermal and dispersion characteristics of diffractive elements were introduced,then an athermal method by using the thermal compensation characteristics of the diffractive surface on the dome’s inner surface was given.A gimbaled conformal optical system used in mid-IR wavelength was designed.After analyzing the design,it is shown that the conformal optical system makes full use of the charateristics of diffraction elements in good phase compensation,small heat expansion coefficients and big dispersion factors and can work well at-40～70 ℃ while its average MTF value is higher than 0.43 in each Field of Regard （FOR）.