The Basics of the Microscope
The modern microscope is a collection of interchangeable parts. There is no such thing as a "phase microscope" or a "fluorescence microscope", the microscope is made up of a collection of parts, call them modules, that provide the required functions. Microscope manufacturers work very hard to increase the modularity of their microscopes. The more modular the more economically they can manufacture them. They don't have to manufacture a frame just for metallurgists or a binocular head just for biologists. They can manufacture a range of modules and use them for a wide range of purposes.
There are two basic types of modern microscopes, the stereo and the compound. The stereo uses two separate light paths to get a true stereo image of the specimen. The compound has one beam path but may split that into two parts, one for each eye. This is binocular vision which is different from stereo.
When you look into a stereo microscope you see the specimen's depth in true 3-D. This makes it real easy to dissect objects, do surgery or look at complex 3-D objects. Stereos are limited in their resolution so they are limited in their magnification. Stereos are the most used microscope, they are found every were from ecology studies to machine tools.
The binocular compound is the microscope used when high resolution is needed and when depth perception is not needed. Compound means that there are two major optical parts to the microscope, an objective and an eyepiece, providing magnification. Frankly the stereo works in a very similar fashion but I'm going to use compound because every body else does.
In the old days compound microscopes could be either monocular (only one eye could be used) or binocular (both eyes are used). The modern compound microscope is binocular. Monocular microscopes are a commercial non-entity. If they are sold at all they are sold to small schools that should know better. Monoculars are very hard to use even for experienced users. They take all the fun out of the micro world. If you have budget constraints and are thinking of a monocular microscope try buying good used binocular microscopes. This is a far better plan than killing some ones love of the micro world with an impossible to use microscope.
To make it easier on all of us, me writing and you reading, I am from here on out going to call a compound microscope a microscope and a stereo microscope a stereo. That's what everyone commercially calls them and I guess I'll go along with the crowd.
A modern microscope comes in two basic frame types. These are the upright and the inverted. The upright microscope looks down on the specimen with its objectives. This is the most used type of microscope. The inverted looks up at the specimen. Inverteds are designed to be used were ever the specimen is very large or heavy or were the specimen is influenced by gravity. Yes I know that everything is influenced by gravity but some things like cells in suspension are influenced more than others. Inverted microscopes are used to look at materials, cell culture and aquatic specimens.
These types of specimens show the two uses for inverted microscopes. Materials specimens can be both large and heavy, they need the large, fixed stages that are typical of modern inverteds. Cell culture and aquatic specimens collect on the bottom of their containers. The only way to see these specimens with any ease is to look up through the bottom of the container.
Inverteds come in two sizes, routine and research. The routine size is the smaller of the two and is built with limited uses in mind. It may not have a fine focus since it is designed for low to medium powers only, its stage may not be as versatile and it may not accept cameras as easily as a research inverted. The research inverted is designed to do everything. Any technique you can think of along with a wide range of documentation accessories (35mm cameras, tv., etc.). All research inverted can be equipped for Kohler illumination. These are large, expensive and complex microscopes that can do a wide range of things. If you need a wide range of things done with an inverted then buy one.
If you are doing materials work you will probably use a research inverted without a transmitted illuminator. This setup used to be called a metalagraph. However in todays materials scene were a metalurgist may be looking at carbon fibers and the microscope being used is the same frame as a biologists I feel that the term is outdated.
Upright microscopes come in three general sizes; student, bench top or mid size and research. The three size differ in price, capability and illumination. Bench top and research microscopes are Kohler illuminated while most student microscopes use diffusion illumination. Student microscopes are the smallest and least expensive of the three. While student microscopes can be used for advanced techniques and documentation they do not do these things with ease or grace. They are designed for bright field and phase and to be used by students. This means that they have to be rugged and simple to use.
Student microscopes are sold primarily to schools, no surprise there. They also make very good doctors office microscopes since they are simple, rugged and cheap. If you do not need high performance and ruggedness is very important consider a student microscope. The prices start at $900 to and go up to $2100 depending on equipment and the quantity you buy. Dealers usually get a better price break on student microscopes.
Bench top microscopes are used in every imaginable discipline. From textiles to animal husbandry the bench top is the work horse. Bench tops can do just about any technique you can think of. The difference between a bench top and research microscope is how many techniques they can do at one time and how many documentation devices they can use at once.
A bench top can do all the techniques you can think of but you might have to disassemble it to but on new modules. If this isn't a problem a bench top is a very good idea. If you are going to be doing only one technique and not a lot of documentation then a bench top is ideal. Modern bench top microscopes try not only to be modular but very easy to use. More and more we are seeing bench top microscopes add ease of use features like very low set control positions and tiltable heads. These features are there to make the user more productive.
Research microscopes are big. I mean big as in large as in heavy as in... well you get the idea. A modern research microscope will weigh in the range of 30Kg. to 50 Kg. This mass is composed of big optical systems, big mechanical systems and lots of electronics. These behemoths can use multiple cameras, large specimens and the widest range of simultaneous techniques. Most have built in computers to control the cameras and other functions including focus. If you are doing particularly demanding work or if you do a lot of documentation then one of these is in order. While they are expensive they can do what no other microscope can do. However a bench top may do all you want to do for a whole lot less money.
What this means to you
The two basic types of microscopes are stereo and compound. Inside the compound group are inverted and upright. There are size categories in both groups that balance money and performance.