Study of the imaging property of a fluorescent confocal microscopy with a phase-only filter in an extended source

The phase information of an enlarged source is reconstructed with an annular two-zone phase-only filter in a fluorescent confocal scanning optical microscope for resolution improvement. The dependences of its resolution on the source size and on the phase transmission of the outer annular zone of the filter are investigated theoretically by use of its three-dimensional optical transfer function (3D OTF). The increased source size and the required phase value of the outer annular zone of the phase-only filter for an optimal 3D OTF of the optical system are presented.