波带片的聚焦特性

我们在研究中发现,文献1]中所发表的关于菲涅尔波带片聚焦特性的结果,实际上是利用了夫朗和费近似而推导出的。本文指出,用这种方法推导出的结果,除了以瑞利准则定义的分解力外,都是不精确的,甚至是错误的。此外,本文还探讨了双相非光学波带片的聚焦特性。分析结果表明,在环数较少的情况下,对高分解力和低旁瓣的要求,双相波带片能提供正波带片或负波带片更好的折衷。

Focusing Properties of Zone Plates

Results published previously~1 concerning the focusing properties of Fresnel zone plates are found as that obtained by invoking Fraunhofer approximation. In this paper, we point out that the focusing properties of Fresnel zone plates derived from Fraunhofer diffraction theory are incorrect. except the resolution when it is defined based on Rayleigh criterion.our analysis also extends to the case of non-optical two-phase zone plates. The analysis shows that a twophase zone plate provides a more acceptable compromise between resolution and sidelobe level than a positive or a negative one when the number of zones is small.