短焦距折衍射变焦成像系统中菲涅耳波带片的设计与分析

Design and analysis of the Fresnel zone plate applied in the refractive-diffractive hybrid imaging system with the short focus length

在折衍射变焦成像系统中,菲涅耳波带片(FZP)的上下两块电极图形是完全对准的。但是在短焦距折衍射成像系统中,FZP最小环带间距已达到微米级,导致上下两块电极图形中心对准极为困难。为减少对准误差,将上基板电极设计成环状图形,下基板设计为一个平板电极。应用衍射光学方法从理论上对此设计进行了分析,并与上述上下两块电极图形完全对准的设计方式对成像系统的影响进行比较,结果增加了焦点数目。

The patterns of two electrodes as the upper and lower substrates are accurately superposed on the Fresnel zone plate （FZP） in the refractive-diffractive hybrid focus-variable imaging system. However, for such imaging system with short focal length, the minimum width of the zone of FZP has reached the micron level. In order to reduce the error of center superposition, we designed a model that the upper substrate consists of annulate electrode while the lower substrate is entirely flat. We theoretically analyzed the model by the method of diffractive optics and compared the effect on the imaging which is caused by heterogeneous electric field with the symmetrical electric field. The result of the design is increase the number of foucs.