By: Steve Adams. G0KVZ
As presented to the Vange Amateur Radio Society 21st Jun 2007
For the last 400 years, microscopes have been around in one form or another.
Although the actual inventor is unknown,
they were developed in the Netherlands between 1590 and 1608.
The lenses used in early examples were inadequate and resulted in rather poor images,
but even these early devices were a boon to scientists in their research into living
A compound lens is utilised in all modern microscopes as it is necessary to overcome
This is caused by the fact that the different colours that make up white light are not
refracted by the same amount when passed through one lens,
therefore a second lens is used to correct this distortion.
Typical power of modern microscopes is between x40 and x500,
although powers of x1200 are possible.
Development of the Electron microscope began in 1931, the first prototype,
capable of magnifying objects at just x400, was built by two German engineers,
Max Knoll and Ernst Ruska with the design being based on the work of Louis de Broglie,
a French physicist. Although Siemens held the patent (1931) it wasn't until 1937 that
they became actively involved by further developing the Electron microscope.
Modern electron microscopes are capable of magnifications of over x10,000
How the Electron microscope works
The performance of an ordinary microscope it limited by the fact that light waves are relatively
large when compared to some of the objects that need to be viewed.
In fact, light would simply pass by a virus particle rendering it invisible to light.
The electron microscope isn't troubled by this limitation, as it utilises an electron beam.
This beam of electrons is accelerated to a very high velocity using very high voltages,
and is focused using magnetic and or electric fields.
The electrons interact with the sample,
and this interaction is sensed electronically and converted into an image.
Modern uses for the Electron microscope
Surface features of an object - Hardness, reflectivity, etc.
Shape & size of particles - ductility, strength, etc.
Elements and compounds in the structure - melting point, hardness, etc.
Atom arrangement - conductivity, strength, etc.
These attributes can be determined for any material viewed in an electron microscope,
and this enables it to be used for diverse purposes in Metallurgy, Chemistry and Forensics,
as well as more conventional uses.
As mentioned previously, Electron microscopes can be used to show the internal fabrication of integrated circuits,
This is a fascinating topic, and there is a superb website devoted to the fantastic images of i.c's.
On these images examples can be seen of the hardware designers demonstrating how they can 'tag' their projects
in a way that would normally be invisible.
These 'doodlings' can be both ingenious and humourous.
Please visit The Florida State University Site!