An inverted metallographic microscope is one of the two types of metallographic microscopes used today.  It functions in much the same way as an upright metallographic microscope but is designed differently.  It also has a slightly different use compared to an upright microscope. 

The design and purpose of the inverted metallographic microscope
The main purpose of a metallographic microscope is to study samples of metals and metal alloys.  In some cases, it can also be used to study rocks and minerals, ideally by producing a flat, smooth and polished surface.  This type of optical microscopy allows the operator to examine the nature of the specimen, its grain, structure and any abnormalities on its surface.  It is a very valuable instrument used in a variety of fields including quality control laboratories, silicon wafer plants and foundries.  It is also an important tool in geological field work.

The upright metallographic microscope is often used to view flat or smaller specimens such as silicon wafers, flat metals and alloys or thin slices of rocks and minerals.  However, there are times when samples cannot be processed or sliced into thin pieces, making them difficult to use with the upright metallographic microscope.  This is because the working distance between the stage on which the specimen is mounted and the objective lens is too small to accommodate a bigger sample.

When samples are too big or thick to use with an upright metallographic microscope, the inverted metallographic microscope is preferred.  Unlike a conventional upright microscope, the inverted type is built with its light source and condenser on top of the specimen stage while its objective lenses are located below.  Essentially, using the inverted microscope means viewing the specimen from above instead of from below.

The setup of this optical microscopy system allows an operator to study metal samples and other specimen that are too large or heavy to be used with upright microscopes.  This way, the working distance between the specimen and the objectives also does not become a problem.  This setup is not limited to metallurgical and metallographic studies, however.  There are also inverted microscopes used with biological specimens in clinical laboratories.

Magnification
The type of magnification that an inverted metallographic microscope is equipped with will depend on what its purpose will be.  Standard inverted microscopes are generally smaller and are good enough for students, teachers and hobbyists.  Although equipped with a fine focus mechanism, these units don’t always offer the best magnification.  But in terms of general usage, their features and functionality should suffice.

Inverted metallographic microscopes used for research by professionals are much bigger and are equipped with more features.  This versatility allows the operator to enhance magnification and to use the microscope with other devices such as cameras and computers.  Research-type inverted microscopes can also handle a wider range of samples.

Key considerations in an inverted metallographic microscope
Not all inverted metallographic microscopes are designed and built the same way, since their purposes differ.  However, there are key points to consider when choosing this type of instrument.  These include:

Type of application
The type of inverted metallographic microscope you should choose will depend on the purpose it will serve.  The wider the range of its use, the higher quality the microscope should offer.  For one, it is impractical to purchase two different metallographic microscopes for two different purposes.  One unit should be able to cover all the necessary areas the microscope will be used for.

Optics
The microscope’s quality and performance will depend heavily on its optical system.  The magnification power of the microscope can range from 100x to a high of 1000x, although some brands might offer even higher magnification.  The objective lens can range from 10x to 100x.  If the microscope will be used to capture images of the specimen, the resolution should also be considered because it will impact the quality of the image later on.

Precision control
Viewing the optimum image of the specimen is still controlled manually so it’s important that the precision control of the instrument is of high quality.  Its focusing mechanism should be able to produce crisp and clear images efficiently.  It is also important that the inverted metallographic microscope is sturdy and can withstand temperature changes, jarring and vibrations.

Ergonomics
If long hours working with an inverted metallographic microscope are foreseen, it is important that the instrument is ergonomically designed to ensure that the operator is comfortable.  Ergonomics will also play a key part in the design of the microscope to ensure that its control mechanisms are within reach and are easy to use.

Expandability
If the inverted metallographic microscope will be used with other accessories on a regular basis, choose one that has all the ports needed for connectivity to digital cameras, videocams, computers or computer monitors.  It should also be flexible enough to provide interchangeable lenses to improve image quality and to work with optional light sources in case conditions are not ideal.