A microscopeis an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.
There are many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope) and the various types of scanning probe microscope.
History:
The first microscope to be developed was the optical microscope, although the original inventor is not easy to identify. An early microscope was made in 1590 in Middelburg, Netherlands.Two eyeglass makers are variously given credit: Hans Lippershey (who developed an early telescope) and Hans Janssen. Giovanni Faber coined the name microscope for Galileo Galilei's compound microscope in 1625.
It was not until the 1660s and 1670s that the microscope was used extensively for research in Italy, Holland and England. Marcelo Malpighi in Italy began the analysis of biological structures beginning with the lungs. Robert Hooke's Micrographia had a huge impact, largely because of its impressive illustrations. The greatest contribution came from Antoni van Leeuwenhoek who discovered red blood cells and spermatozoa and helped popularise microscopy as a technique. On 9 October 1676, Leeuwenhoek reported the discovery of micro-organisms.
In the early 1900s a significant alternative to light microscopy was developed, using electrons rather than light to generate the image. Ernst Ruska started development of the first electron microscope in 1931 which was the transmission electron microscope (TEM). The transmission electron microscope works on the same principle as an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses. Use of electrons instead of light allows a much higher resolution.
The 1980s saw the development of the first scanning probe microscopes. The first was the scanning tunneling microscope in 1981, developed by Gerd Binnig and Heinrich Rohrer. This was closely followed in 1986 with Gerd Binnig, Quate, and Gerber's invention of the atomic force microscope.
Components:
-Eyepiece (ocular):
The eyepiece, or ocular, is a cylinder containing two or more lenses; its function is to bring the image into focus for the eye. The eyepiece is inserted into the top end of the body tube. Eyepieces are interchangeable and many different eyepieces can be inserted with different degrees of magnification. Typical magnification values for eyepieces include 2×, 5× and 10×. In some high performance microscopes, the optical configuration of the objective lens and eyepiece are matched to give the best possible optical performance. This occurs most commonly with apochromatic objectives.
-Objective turret or Revolver:
Objective turret or Revolver is the part that holds the set of objective lenses, it allows to change them.
-Objective:
At the lower end of a typical compound optical microscope there are one or more objective lenses that collect light from the sample. The objective is usually in a cylinder housing containing a glass single or multi-element compound lens. Typically there will be around three objective lenses screwed into a circular nose piece which may be rotated to select the required objective lens. These arrangements are designed to be parfocal, which means that when one changes from one lens to another on a microscope, the sample stays in focus. Microscope objectives are characterized by two parameters, namely, magnification and numerical aperture. The former typically ranges from 5× to 100× while the latter ranges from 0.14 to 0.7, corresponding to focal lengths of about 40 to 2 mm, respectively. Objective lenses with higher magnifications normally have a higher numerical aperture and a shorter depth of field in the resulting image. Some high performance objective lenses may require matched eyepieces to deliver the best optical performance.
-Focus wheels(macrometer):
Adjustment wheels move the stage up and down with separate adjustment for coarse and fine focussing. The same controls enable the microscope to adjust to specimens of different thickness. In older designs of microscopes, the focus adjustment wheels move the microscope tube up or down relative to the stand and had a fixed stage.
- Frame:
The frame provides a mounting point for various microscope controls. Normally this will include controls for focusing, typically a large knurled wheel to adjust coarse focus, together with a smaller knurled wheel to control fine focus. Other features may be lamp controls and/or controls for adjusting the condenser.
- Light source:
Many sources of light can be used. At its simplest, daylight is directed via a mirror. Most microscopes, however, have their own adjustable and controllable light source – often a halogen lamp, although illumination using LEDs and lasers are becoming a more common provision.
- Condenser:
The condenser is a lens designed to focus light from the illumination source onto the sample. The condenser may also include other features, such as a diaphragm and/or filters, to manage the quality and intensity of the illumination. For illumination techniques like dark field, phase contrast and differential interference contrast microscopy additional optical components must be precisely aligned in the light path.
The stage is a platform below the objective which supports the specimen being viewed. In the center of the stage is a hole through which light passes to illuminate the specimen. The stage usually has arms to hold slides (rectangular glass plates with typical dimensions of 25×75 mm, on which the specimen is mounted).
At magnifications higher than 100x moving a slide by hand is not practical. A mechanical stage, typical of medium and higher priced microscopes, allows tiny movements of the slide via control knobs that reposition the sample/slide as desired. If a microscope did not originally have a mechanical stage it may be possible to add one.
All stages move up and down for focus. With a mechanical stage slides move on two horizontal axes for positioning the specimen to examine specimen details.
Focusing starts at lower magnification in order to center the specimen by the user on the stage. Moving to a higher magnification requires the stage to be moved higher vertically for re-focus at the higher magnification and may also require slight horizontal specimen position adjustment. Horizontal specimen position adjustments are the reason for having a mechanical stage.
Due to the difficulty in preparing specimens and mounting them on slides, for children it's best to begin with prepared slides that are centered and focus easily regardless of the focus level used.
-Other components
1.Body tube 5.Reflector mirror
2.Revolver 6.Arm
3.stage clips 7.Base
4.Diagraphm 8.Micrometer
Actually there are several things that need to be familiar with how to care and use of microscopes. Microscopes are stored in the box that were previously wrapped in plastic. When the microscope was used immediately clean any dirt that is returned by way wiped with a soft cloth, then return to the original box, with the condition of objective lens that has a weak magnification microscope and erect state. At the time of the microscope was taken, use it with both hands. One hand holding the arm of a microscope, and the hand holding the other leg microscope. At the time of the microscope will be used to see something or specimens, then you must:
a. Use the objective lens with a magnification of the smallest or weakest.
b. Place the object on the microscope table, bring the objective lens to the object.
c. Note the shadow of the object through the eyepiece, with a rough player, move the objective lens away from or close to the object to be observed.
d. Adjust the position of the shadow to be visible in the middle of the observation area.
e. If the shadow is not visible, repeat the activity above.
f. If the image has not been seen clearly, try not to use a powerful objective lens.
g. At the time of moving the objective lens of magnification weak to the strong magnification, should look to the side to avoid friction with the outbreak of the glass objects or glass objects or specimens.
h. Do not direct mirror directly at the sun, because the very strong light bounced off a mirror to the eye can lead to impaired vision.
i. Clean the lens with lens paper. Give a little water on the paper used to clean the lens before the lens. To clean dirt that is difficult to clean, use alcohol that dripped onto the paper before attempting to clean lens
j. At the time of use, glass objects covered with glass cover. Be careful when using a glass cover, because it is easily broken and can injure the hand.
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