This text is to compare Frensnel s zones plate with ordinary lens, on the axle point of light intension and focal distance as well as their difference in use.
当光通过菲涅耳半波带与普通透镜时，可发现在轴上点的光强、焦距以及用途上的不同。
2
When the number ofzones is sufficiently large, only one focus to shift to the lens can be obtained in the transmission space.