Optical sectioning by two-pinhole confocal fluorescence microscopy.

A two-pinhole axially superresolving confocal fluorescence imaging system is presented. Based on the concept of subtractive incoherent imaging, the system described here is equipped with a zero-focus complex-transmittance pupil filter in one of the collector paths. The optical sectioning capacity of the system is 25% superior to that of a free-pupil one-pinhole instrument.