Comparison of microscopic techniques/resolution

A microscope is a device you use to look at objects, which are much smaller than everything your eye is able to see. A technique that uses microscopes is called microscopy. Microscopy is mainly used in medicine and biology. In the following article I am going to compare the resolution of different microscopes (optical microscope, confocal microscope, atomic force microscope, electron microscope and fluorescence microscope) and explain where they are used in medicine.

Microscopic techniques and especially electron microscopes are used in medicine when it comes to renal diseases, tumor process, storage disorders and the identification of infectious agents. Light microscopes are still used everywhere where living biology is observed, for example if you want to take a look at the blood of your patient. So it is very helpful when trying to make a diagnosis. There are different types of microscopy techniques:

Optical microscopy is the oldest microscopic technique. Its resolution is about 200 nanometers, which is called the Abbe-Limit. Named after Ernst Abbe who developed the underlying regularities. Since 1963 there are several other optical microscopic techniques for example: 3D-SIM microscopy with a resolution of 105nm, 4Pi microscopy with a resolution of approximately 650-850nm, STED microscopy with a resolution o 2,4nm.

A confocal microscope is a special type of an optical microscope. As generally with light microscopes the resolution is limited by the diffraction. The resolution of a confocal microscope can be up to 0,8 nm.

An atomic force microscope does mechanical scanning of surfaces and measurement of atomic forces on the nanometerscale. So a atomic force microscope can have a resolution of 10-20nm.

Since 1930 there are electron microscopes with a higher resolution than optical microscopes, because electron waves have a 100,000 higher wavelength than light. A transmission electron microscope can have a resolution up to 50pm.

Fluorescence microscopy is also a special form of optical microscopy. It is based on the physical effect of fluorescence. Since 1960s, fluorescence microscopes are usually constructed as reflected light microscopes, their resolution can be around 700nm.

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Sources: http://www.physik.uni-regensburg.de/forschung/schwarz/Mikroskopie/11-AFM.pdf http://jacobs.physik.uni-saarland.de/lehre/Rasterkraftmikroskopie.pdf http://www.chemie.de/lexikon/Rasterkraftmikroskop.html http://www.nejm.org/doi/full/10.1056/NEJM184610210351201 http://www.imaging-git.com/science/electron-and-ion-microscopy/applications-electron-microscopy-medicine