Coherent confocal microscope with a phase-only filter in its extended source

The phase information of an extended source is reconstructed by use of a two-zone （annular） phaseonly filter in a coherent confocel scanning optical microscope. The dependence of its resolution on its source size is investigated theoretically by its three-dimensional optical transfer function （3D OTF）. The results show that the resolution is improved, even though the source size is enlarged.