Axial super-resolution using a double-zone pinhole in a confocal microscope

A double-zone pinhole intensity ratio measurement method is proposed for confocal microscopy based on the inverse phase characteristics of the axial response between the central and annular portions of the spot. The simulation and experimental results show that when the normalized optical radius of the central region is 3.2 and the peak values of the axial response of the two regions are similar, the central lobe of the axial characteristic curve can be compressed by 72.8%, without changing the original structure of the system. This simple method can effectively suppress both the light-source intensity drift and changes in the measured surface reflectance.