将谐衍射透镜应用在传统红外单波段佩茨瓦尔(Petzval)物镜上,设计得到工作波段处于3.4～4.2 μm和8～11 μm的红外双波段单层谐衍射光学系统。但单层谐衍射元件的衍射效率只在设计波长处衍射效率最高,随着波长相对设计中心波长向两侧偏离,主衍射级次的衍射效率逐渐下降。为提高含单层谐衍射元件光学系统的衍射效率,基于双层衍射元件衍射效率表达式研究了双层谐衍射元件的结构优化,给出了优化方法。设计出佩茨瓦尔型红外双波段双层谐衍射光学系统,其在3.4～4.2 μm和8～11 μm两个工作波段的衍射效率均达到90%以上,相比含有单层谐衍射面的光学系统衍射效率有了很大提升,提高了像面衬比度,完善了系统成像质量。

A new infrared dual-band Petzval objective with single-layer harmonic diffractive element (HDE) is designed, which can work in the 3.4～4.2 μm and 8～11 μm bands. However, it is only at the designed center wavelength that the single-layer harmonic diffractive element possesses the maximum diffraction efficiency, and the diffraction efficiency at the master diffraction order gradually decreases with the deviation of the wavelength from the center to both sides. To improve the diffraction efficiency, the double-layer harmonic diffractive element (HDE) structure is investigated and the optimization procedure is given based on the equation of diffraction efficiency of the double-layer diffractive element. Then the infrared dual-band Petzval objective with double-layer harmonic diffractive element is designed. The diffraction efficiency of the system at each wavelength in the designed 3.4～4.2 μm and 8～11 μm bands is larger than 90%, which improves the image contrast and the imaging quality significantly.