【摘要】 本文利用波带片通光孔的半径与半波带数、焦距及波长的关系ρ_k=（Kf′λ）^1/2简单扼要地分析了在波带片主轴上,除了与波带片距离为f′这个主焦点外,与它距离为f′/3,f′/5,…等各点为什么是波带片的弱焦点,而在主轴上距波带片为nf′（n=2,3,…）的相应系列点为什么不是波带片焦点之原因。更多还原

【Abstract】 In this essay, thr relationship between the rcdius of the transparent round hole and the number of thr half-wave band, focal length and wavelength, pK = , is used to analyze the reason why the points on the principal axis of the zone plate, which arc at the distance of f’/3, f’/5 and so forth from it , arc its weak focuses except that the point on the axis at the distance of f’ from it, is the principal focus, while the relevant scries of points on the principal axis, which arc at the distance of nf’(n=2, 3,…) from the zone plate , arc not the focuses of it.更多还原