A
4Pi microscope is a laser scanning fluorescent microscope with an improved axial resolution
.
The typical value of 500–700 nm can be improved to 100–150 nm which
corresponds to an almost spherical focal spot with 5–7 times less volume
than that of standard confocal microscopy.
The improvement in resolution is achieved by using two opposing
objective lenses which both are focused to the same geometrical
location.