一个正透镜、一个负透镜及一个衍射光学元件以不同的组合可以构成两种折衍射混合光学系统。当这两种系统消球差、彗差及复消色差后会产生不同的色球差。通过赛德尔像差理论,分析了这两种结构产生不同色球差的原因。计算表明当衍射光学元件以负透镜的平面为基底时产生的色球差为以正透镜的平面为基底时产生的色球差的7倍。对衍射光学元件以负透镜的平面为基底的情形,提出了减小系统色球差的解决办法,使系统色球差减小到0.307 mm。另外设计了一个传统复消色差光学系统,并和折衍射混合光学系统进行了比较,分析表明,衍射光学元件可代替传统光学系统中的特殊光学材料并使系统达到相同的成像质量。最后讨论了衍射光学元件的衍射效率对系统成像质量的影响。

A positive lens, a negative lens and a diffractive optical element (DOE) can compose two kinds of hybrid diffractive-refractive telescope objectives when assembled differently. There is a different spherochromatism after the two systems correct secondary spectrum, spherical aberration and comatic aberration. Reasons of the different spherochromatism of the two configurations are researched by Seidel aberration analysis. And spherochromatism of the configuration with diffractive optical element placed on the negative lens is 7 times as much as that of the other. When the substrate of diffractive optical element is the negative lens, a solution is presented to decrease spherochromatism of the system, and the value of spherochromatism is decreased to 0.307 mm. A conventional apochromatic optical system is designed in addition, and compared with the hybrid diffractive-refractive apochromatic optical system. It shows DOE can substitute special optical material of conventional optical system and obtain the same imaging effect. The influence of diffraction efficiency on the imaging optical system by the polychromatic integrated efficiency of DOE is analyzed at last.