Electron microscope by Max Knoll and Ernst Ruska

For a long time, Leeuwenhoek’s; microscope was the best tool for studying cells. Leeuwenhoek’s microscope used light to focus on an object.

The electron was discovered in 1897 by the Cambridge physicist J.J Thomson (1856-1940), who regarded it as a particle. In 1924 Louis de Broglie (1892-1966) introduced the idea of the wave nature of the electron.

Two years later in 1926, Hans Busch also working in Berlin, published an explanation of how the electron lens worked. He showed that a magnetic coil focuses an electron beam passing through it in the same way that a lens focuses a beam of light.

The first electron microscope was developed by Max Knoll and Ernst Ruska in Germany, 1931. They combined two magnetic coils in an attempt to create an electron microscope.

In 1933, Ruska demonstrated a point-to-point resolution of 50 nanometers in a specimen of cotton fibers.

With electron microscope, they were able to view objects at 400 times the normal sizes. A modern electron microscope can enlarge images by up to two million times.

By the 1950s and 1960s electron microscope had been developed to a high state of efficiency, enabling scientists to peer more deeply into nature’s secrets.
Electron microscope by Max Knoll and Ernst Ruska 

History of electron microscope

Louis de Broglie in 1925 first theorized that the electron had wave length characteristics with a wavelength substantially less that visible light. During 1926-1927 Hand Busch discovered that a rotationally symmetric, inhomogeneous magnetic field could be conceived of as a lens for an electron beam.

The term electron microscope was first used in the paper written by Max Knoll of Berlin Institute of Technology and Ernst Ruska of High-Voltage Laboratory in 1932.

In the paper they developed the idea of electron lenses into a practical reality and demonstrated electron images taken by the instrument.

In 1933 they made a ‘super-microscope’ of the ten thousands magnifications, by a system of an electron lens composed of two magnets with two pairs of pole piece.

By 1939, the first commercial transmission electron microscope from Siemens Corporation, based on the improvements of Ruska’s work was introduced.

In 1942 and electrostatic type by Toshiba and a magnetic type by Hitachi were commercialized.

After the war, learning from the development in the USA, electron microscope were produced not only by Hitachi, Toshiba but also by Shimazu and Japan Electron Optical Laboratory and in 1955 exportation began.

The 1970s brought further improvement in all of t operational systems of the electron microscope and also saw the development of high voltage electron microscope, scanning transmission electron microscope and an industry wide standard of 0.344 nm resolution for transmission electron microscopes sold in later part of the decade.
History of electron microscope