Field metallographic microscopes are a type of optical microscopy designed to view polished surfaces of rocks, minerals and metals.  Using high magnification power, metallographic microscopes are used in natural fields of study such as geology, materials science and in the semiconductor industry, often for the examination and evaluation of opaque materials and specimen. 

What makes field metallographic microscopes different from other types of optical microscopy?
Field metallographic microscopes are especially designed microscopes for use in field studies.  In geology, for example, researchers usually need to immediately examine rock and mineral specimens on site, since cutting, processing and transporting the samples to a laboratory often takes time and unnecessary effort.  With a metallographic microscope on hand, it is easier and much more cost effective to examine samples on location.

Field metallographic microscopes, also known as metallurgical microscopes, are built to be sturdier and tougher than conventional microscopes.  This is to ensure that the instruments can withstand the transport and regular wear and tear associated with field and on site activity.  These microscopes also have high power magnification capability, able to enlarge images thousands of times the normal size.

Types of field metallographic microscopes
There are two types of field metallographic microscopes: the upright microscope and the inverted microscope.  Although they are used differently, they are both valuable instruments in the field of metallurgy.  Of the two, it is the upright metallographic microscope that is more frequently used.  These are the same microscopes found in semiconductor plants and are used to examine and evaluate semiconductor products.  The inverted metallographic microscope, on the other hand, is used to view larger, heavier specimens.

The electron microscope in metallurgy
Another instrument that is often found helpful in metallurgy is the electron microscope.  Unlike other types of microscopes, the electron microscope utilizes electrons instead of light.  This results to highly magnified specimen images.  Electron microscopes allow the operator to view the basic structure of various materials.

Uses of field metallographic microscopes
Field metallographic microscopes are the instruments of choice for viewing flat, smooth surfaces of opaque materials such as rocks, minerals, metals, ceramics and clay, among others.  They are also used in microstructure analysis, crystallography and for the study of historical artifacts.  Because of their high power magnification features, field metallographic microscopes are capable of enlarging specimens to allow the operator to view surface defects, gradation in color, inclusions, grain size, grain boundaries and coating quality.

Field metallographic microscopes are effective for use in both remote locations and laboratories.  To allow better control and ease of use, they are often mounted on tripods to allow flexibility during field work.  They are rugged instruments but are portable and light enough for easy transport.

What to look for in metallographic microscopes
There are certain key components that make a field metallographic microscope a better choice.  However, always take into consideration its uses.  Metallographic microscopes are equipped with different features, not all of which may fit a particular requirement.  To ensure that the metallographic microscope is of excellent quality, there are certain areas where it should excel.  These include:

Optics
Any microscope is only as good as its optical system.  Optics should be made with quality materials and should exhibit good craftsmanship.  In good quality metallographic microscopes, optical lenses are often precision ground to ensure that they are durable and capable of producing excellent images.

Magnification
Field metallographic microscopes use high power magnification optics, with magnifications ranging from a low of 100x to a high of 1000x and objective lenses ranging from 10x to 100x.

Illumination
The nature of the samples viewed with field metallographic microscopes requires that a special type of illumination is used.  Bright field microscopes, for example, are not effective for use with opaque, polished materials.  This is because solid specimens are not capable of absorbing light and reflecting it for the operator to see.  For the study of metals, rocks and minerals, metallographic microscopes are usually equipped with polarizing light technology.

In polarized light microscopy, polarizing filters are used to manipulate light by splitting it into varied propagation speeds, a process referred to as birefringement.  When light passes through the two polarizing filters (the polarizer and the analyzer), it results to an image with excellent contrast and clarity.

For certain studies involving certain materials such as silicon wafers and mineral oxides, reflected light may be preferred because materials such as these are not good transmitters of light.  Generally, high power illumination from bulbs with at least 30 watts is often used.

Usability with other accessories
Very often, field metallographic microscopes are used with other accessories such as digital cameras, video cameras and computers.  These accessories make it possible for images to be captured and stored efficiently.  This is especially important in field work where it is not feasible to bring samples of specimen from the site to another location.