Different Types of Microscope:
How to Select a Light Microscope
A look at the different types of microscopes and what they are used for
The Englishman Robert Hooke (18th July 1635 - 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke's law), his book Micrographia, published in 1665 and for first applying the word "cell" to describe the basic unit of life. It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some fifteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor.
There are many different types of microscope, but it is easier to split these into two main categories.
Light microscopes and Non-light microscopes.
What do we mean by light microscope?
A light microscope is a generic term for the type of microscope you would normally see on TV, being used by men in white coats in a scientific laboratory. Basically, a regular "microscope", with two eyepieces and a recognisable microscope shape. This is a light microscope, but could equally be called a compound microscope, or optical microscope. The descriptions are different, but they all refer to the same basic microscope.
Each very different, but all are light microscopes
However, there are many different sub-categories of light microscope, each with a specific purpose, since people have many different requirements when magnifying subjects. In order to know which type of microscope you require, there are some basic questions that need answering:
- What sample will you be looking at?
- What magnification do you require?
- Do you want to 'do' anything to the sample whilst being magnified?
1. What sample will you be looking at?
Different samples have different physical properties and people want to look at almost anything under a microscope! For example, blood is very different to a diamond ring. If you are a microbiologist, your requirements for a microscope will be very different to a jewelry manufacturer.
2. What magnification do you require?
Red blood cells might typically be 6 - 8 µm in diameter, which is very small indeed! You will need a minimum magnification of around 400x to see red blood cells, but if you wish to view the cells in more detail, you will naturally need a greater magnification. Furthermore, blood will need to be prepared on a glass slide, so that you can view all the details you require.
A diamond ring however is approximately 1.5cm in size, which you can see it with your eyes. If you are a jewelry maker, you will need to see all the intricate details of the ring, so 10x - 20x magnification would be fine.
3. Do you want to 'do' anything to the sample whilst being magnified?
When setting a diamond in a ring, a jewelry maker will need to carefully place the precious stone in the setting of the ring. In order to do this, a 3-dimensional (stereo) view is required, since this provides depth perception, which aids hand-eye coordination, just in the same way that doing things with one eye closed is more difficult than using both eyes. Although red blood cells are too small to 'do' anything with, you may want to look at different aspects of the cells. This could involve different preparation of the blood and/or different illumination techniques, such a darkfield, or phase contrast illumination (see illumination techniques).
So you can see that people have very different requirements when using light microscopes.