The two lenses to the right of the light source are the condenser. The first lens converges the incoming light and the second lens focuses the light onto the sample and glass slide the smiley face. Finally, the light will end up passing through the objective lens far right which will magnify the light. But what happens if our specimen is sensitive to light? What happens if our image is too bright?
We need a way to control the amount of light entering the condenser and change the shape of the cone of light. Enter the diaphragm! As you can see it limits the light traveling through the condenser. Without us necessarily changing the brightness of the light source itself.
A less common diaphragm is a disc diaphragm looks a little something like this. It is basically a spinning wheel with different diameter openings. Want more light? Switch it over to the large hole. Want less light? Go to the smaller sized hole. The more common type of diaphragm is the iris diaphragm. These are a little more sophisticated and are more common among more expensive and more advanced microscopes.
Your iris controls the amount of light that enters your cones and rods of your eye by adjusting itself to be larger or smaller. This diaphragm is located closer to the condenser system of a microscope. In fact, the condenser sits right on top of the iris diaphragm. The image below is an example of the iris diaphragm and it opens and closes by sliding the switch along the grove which opens and closes the diaphragm to differing degrees. The aperture iris diaphragm goes hand in hand with a more technical concept called numerical aperture.
For a simple explanation of numerical aperture see this post. This diaphragm is also used to control the contrast. Increasingly, they are coaxial knobs - that is to say they are built on the same axis with the fine focus knob on the outside.
Coaxial focus knobs are more convenient since the viewer does not have to grope for a different knob. A mechanical stage is used when working at higher magnifications where delicate movements of the specimen slide are required. The viewer is required to move the slide manually to view different sections of the specimen.
Most light microscopes use low voltage, halogen bulbs with continuous variable lighting control located within the base. It is located under the stage often in conjunction with an iris diaphragm. It is located above the condenser and below the stage. Most high quality microscopes include an Abbe condenser with an iris diaphragm. Combined, they control both the focus and quantity of light applied to the specimen. Compound Microscope Parts. Learn about the parts of a compound microscope before making your first purchase.
All Blogs Compound Compound Microscope Parts A high power or compound microscope achieves higher levels of magnification than a stereo or low power microscope. It is used to view smaller specimens such as cell structures which cannot be seen at lower levels of magnification.
Essentially, a compound microscope consists of structural and optical components. However, within these two basic systems, there are some essential components that every microscopist should know and understand.
Tip: If you are using thin slides and can't focus, rather than adjust the rack stop, place a clear glass slide under the original slide to raise it a bit higher. Condenser Lens : The purpose of the condenser lens is to focus the light onto the specimen. Condenser lenses are most useful at the highest powers x and above. Microscopes with in-stage condenser lenses render a sharper image than those with no lens at x.
If your microscope has a maximum power of x, you will get the maximum benefit by using a condenser lenses rated at 0. A big advantage to a stage mounted lens is that there is one less focusing item to deal with.
If you go to x then you should have a condenser lens with an N. All of our x microscopes use 1. The Abbe condenser lens can be moved up and down. It is set very close to the slide at x and moved further away at the lower powers.
Diaphragm or Iris : Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide. There is no set rule regarding which setting to use for a particular power. Rather, the setting is a function of the transparency of the specimen, the degree of contrast you desire and the particular objective lens in use.
How to Focus Your Microscope : The proper way to focus a microscope is to start with the lowest power objective lens first and while looking from the side, crank the lens down as close to the specimen as possible without touching it.
Now, look through the eyepiece lens and focus upward only until the image is sharp. If you can't get it in focus, repeat the process again. Once the image is sharp with the low power lens, you should be able to simply click in the next power lens and do minor adjustments with the focus knob.
If your microscope has a fine focus adjustment, turning it a bit should be all that's necessary. Continue with subsequent objective lenses and fine focus each time. If you are unsure of the parts and functions of your microscope, contact Microscope World.
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