The 14 parts of the microscope, and their functions

The microscope has been a fundamental tool in research, especially in disciplines related to medicine and biology, such as microbiology, histology and cytology.

However, and despite its relative easy handling, this device has several parts which have different functions that together make it possible to make something microscopic visible to the eye human.

Next we will know the parts of the microscope, in addition to detailing what role they fulfill both structurally and in obtaining the image.

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Microscope parts

These are the parts that make up the microscope, which can be divided into two systems: the mechanical and the optical.

Mechanic system

The mechanical system of the microscope includes all those parts that are part of the structure of the device itself.

These parts provide balance, unite the parts that make up the microscope's optical system, and regulate both the sharpness and magnification of the sample image.

1. Base or foot

The foot constitutes the base of the microscope, being in the lower part of the apparatus and giving it support.

It tends to be the heaviest part of the entire microscope, and it is thanks to this that the device achieves sufficient balance to avoid lying down.

This structure can have several shapes, but the most common is a Y-shaped or a rectangle. It usually includes a rubber stopper to prevent it from sliding across the surface while it is being used.

2. Arm or spine

The arm, also called the column or handle, is the skeleton of the microscope. It is a piece that is in the middle part of the device, connecting all its parts. In this way, connects the surface where the sample to be observed will be placed and the eyepiece, part by which it will be observed.

Both the lenses that make up the eyepiece and those found in the objectives are on the arm of the microscope.

3. Platen

The stage is the part where the sample to be observed is placed. Is about a flat surface on which the glass strip is placed on which the tiny object to be observed is located. To hold this glass strip, the stage has two metal clips.

The vertical position of the stage with respect to the objective lenses is adjustable by means of two screws, also allowing the degree of focus of the sample image to be modulated. In the center of the stage there is a hole through which the light beam from the illumination source passes, located at the base of the microscope.

4. Coarse screw

The coarse screw allows the vertical position of the specimen to be adjusted relative to the objective. This screw, when turned, makes the microscope tube slide vertically thanks to a system similar to that of a zipper.

By this movement, it is possible to quickly focus the preparation on the stage.

5. Micrometer screw

The micrometer screw is a mechanism that used to achieve a more precise focus of the sample to observe. Although focusing with this screw is slower, it is more precise than with the coarse screw.

Thus, using this part of the microscope, it is possible to obtain a sharp focus by moving the stage vertically and almost imperceptibly. These movements are of the order of 0.001 millimeters.

6. Stir

The revolver is a rotating part on which the objectives are mounted. Its name comes from the fact that, when used, it moves and sounds like the revolver of a pistol.

Turning the revolver, Objectives pass through the axis of the tube and are positioned so that what is on the stage can be seen. Each of the objectives that are screwed into this piece have a different magnification and, by turning the revolver, it is possible to choose the most suitable objective for the sample to be observed.

7. Tube

The tube is a structural piece, which is attached to the arm of the microscope, connecting the eyepiece with the objectives. This part it is the one that maintains the correct alignment between the lenses that make up the first and second phase of magnification of the sample image.

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Optical system

The optical system of the telescope includes all the necessary elements to be able to increase the image of what is on the stage and correct its lighting. All parts of the optical system are designed in such a way that it is possible to correct chromatic irregularities, such as for example that the light is divided into different colors.

1. Spotlight or light source

The spotlight, which provides illumination to the hob, it is usually made up of a halogen lamp found at the base of the microscope. The light leaves the bulb and passes into a reflector, sending the light rays to the stage.

Depending on the size of the microscope, this light source will have a higher or lower voltage. In the microscopes most used in laboratories, the voltage is usually 12 volts.

2. Condenser

The condenser consists of a converging lens system that capture the light beam and concentrate its rays in such a way that a greater or lesser contrast is offered.

Normally, the rays emitted by the light bulb are divergent. By means of the capacitor, it is possible to make these rays parallel or even convergent.

In the microscope there is a screw that serves to regulate light condensation. This screw may be in a different place depending on the model of the appliance.

3. Diaphragm or iris

The diaphragm is located above the light reflector and under the stage.

Through this part it is possible to regulate the intensity of the light, opening or closing the diaphragm, just as the human iris does in light from outside. The sweet spot of the diaphragm will vary depending on the specimen on the stage and the degree of illumination where the microscope is located.

4. objectives

The objectives are converging lenses that are regulated by the revolver. These lenses are the ones that offer the first stage of magnification.

Turning the revolver clockwise, the objectives are coupled with each other, allowing to increase the image of what is being observed.

5. Eyepieces

Eyepieces are the lens systems closest to the observer's eye. These are hollow cylinders at the top of the microscope and have converging lenses.

These optical elements are what provide the second stage of image magnification. That is to say, the image is first magnified by the objectives and then again magnified by the eyepieces.

It is the combination of the objective used and the eyepieces that determines the total magnification observed on the stage. Depending on whether the microscope has a single eyepiece or two, we speak of monocular microscopes or binocular microscopes. There are also trinocular microscopes.

6. Optical prism

Some microscopes include optical prisms, which are located inside the apparatus and are used to correct the direction of light.

The existence of this part is very necessary in binocular microscopes, since by means of the prism it is possible to divide the light beam in two so that it goes to both eyepieces and an appropriate two-dimensional image is obtained.

7. Transformer

The transformer is necessary to be able to connect the microscope to the currentSince, normally, the wattage of the light bulb in microscopes is usually below the wattage of ordinary electrical current.

Some transformers have a potentiometer which is used to regulate the intensity of the light.

Bibliographic references:

• Vázquez-Nin, G. (200). Introduction to electron microscopy applied to biological sciences. Mexico DF, Mexico. UNAM.