3-DIMENSIONAL IMAGING IN CONFOCAL FLUORESCENT MICROSCOPY WITH ANNULAR LENSES

Three-dimensional imaging properties in confocal fluorescent microscope systems with annular lenses are investigated in terms of the three-dimensional optical transfer function (OTF). Starting from the OTF, we also consider the optical sectioning property. The dependence of the OTF and the optical sectioning strength on the radius of the central obstruction of the lens is revealed. For the case of a finite-sized circular pinhole in front of the detector, both the OTF and the optical sectioning strength, together with the signal level, are calculated as a function of the radius of the pinhole. Investigations show that for a given finite size of the pinhole, the optical sectioning strength can be increased by altering the radius of the central obstruction of the lens to an optimum value, and that a higher signal level may be maintained by using an annular objective only.