4 PI MICROSCOPY

4Pi microscope is a laser scanning fluorescence microscope with an improved axial resolution. The typical value of 500–700nm can be improved to 100–150nm which corresponds to an almost spherical focal spot with 5–7 times less volume than that of standard confocal microscopy. To achieve a full spherical wavefront with a solid angle of 4π two opposing objective lenses are matched coherently, so the two individual wavefronts add up and join forces.