History
In 1971, Christoph Cremer and Thomas Cremer proposed the creation of a perfect hologram, i.e. one that carries the whole field information of the emission of a point source in all directions, a so-called hologram.
The first description of a practicable system of 4Pi microscopy, i.e. the setup with two opposing, interfering lenses, was invented by Stefan Hell in 1991. He could demonstrate it experimentally also in 1994.
In the following years the number of applications for this microscope have grown. Parallel excitation and detection with 64 spots in the sample simultaneously combined with the improved spatial resolution resulted in the successful recording of the dynamics of mitochondria in yeast cells with a 4Pi microscope in 2002.
A commercial version was launched by microscope manufacturer Leica Microsystems in 2004.
Up to now, the best quality in a 4Pi microscope was reached in conjunction with the STED principle. Using a 4Pi microscope with appropriate excitation and de-excitation beams it was possible to create a uniformly 50 nm sized spot which corresponds to a decreased focal volume compared to confocal microscopy by a factor of 150–200.
Read more about this topic: 4Pi Microscope
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