By Edison Ramsey
To understand the microscope more, you need to understand its parts. You need to understand what each part is capable of.
This article, however, will only focus on the lenses system - the whole group responsible in forming the image.
The Eyepiece
Without this part, you cannot see the specimen being examined. This is by far, among the most important parts of the microscope. This is a cylindrical tube which contains a lens. Stereo microscopes have two eyepieces, while a compound microscope only has one.
The Objective Lenses
The primary role of the objective lenses is to gather light from the object or specimen being observed. There are several objective lenses in a microscope. Each lens varies according to magnification to provide you with more options for better specimen examination.
Sometimes, special objectives are used for certain examination techniques. The phase contrast - developed by Frits Zernike - is by far the most sophisticated. The phase contrast technique is basically about enhancing contrast. As a general rule, you can easily differentiate two specimens or even objects if they have high contrast - white is better seen when set against a black background.
Books and even Internet articles that explain the phase contrast method seems too technical for this kind of article - one that's focused in explaining the lenses system of the microscope. Still, to give you an idea on the concept of the phase contrast microscopy, this simple explanation would do:
It's a bit hard to have a microscopic view of living tissues (such as blood) because most of them are transparent. These kinds of specimen are usually called phase objects because they do not absorb light - instead, they diffract (to cause the bending of the waves) them. As a result of the bending, the light becomes less visible (by 1/4 wavelength). Let's not discuss what 1/4 wavelength really means but simply put, it suggests that such a reduced property of light cannot be seen by your naked eye, not even by a camera.
It is in this context that the phase contrast technique becomes very useful. Somehow, this technique - using special objectives and a condenser - is able to solve such a problem. It is able to yield an image that is darker than its light background.
Other special objectives are the infinity-corrected optical systems - where the image distance is set at infinity. These lenses are great for biomedical and industrial microscopes.
The Nosepiece
As mentioned, most microscopes have more than one objective lenses. As such, these objectives need something to hold them together - and this is where the nosepiece comes in handy.
The Tube
This is the very thing that holds the eyepiece and the objective lenses - but at an appropriate distance. This is responsible for keeping away stray light.
While the lenses are already powerful enough, some still prefer to use accessories such as a fluorescent filter. This is done in order to get optimum lighting and for special viewing techniques.
Once again, these parts only refer to the lenses system of a microscope. These are the ones responsible in forming the image of the specimen. You still need to acquaint yourself with the other parts - such as the illumination system and specimen control to better understand how the microscope works.
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Source:www.isnare.com |
