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

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

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

Parts of the microscope

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

Mechanical system

The mechanical system of the microscope comprises all those parts that are part of the structure of the apparatus itself .

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

1. Base or foot

The foot forms the base of the microscope, being at the lowest part of the apparatus and gives it support. It is usually the heaviest part of the whole microscope , and it is thanks to this that the apparatus achieves sufficient balance to avoid lying down.

This structure can have several shapes, but the most common is Y-shaped or rectangular. It usually includes a rubber bumper to prevent it from sliding across the surface while in use.

2. Arm or column

The arm, also called the spine or handle, is the skeleton of the microscope. It is a piece that lies in the middle 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 , the part through which it will be observed.

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

3. Plate

The plate is the part where you place the sample you want to observe. It is a flat surface on which you place the glass strip on which the tiny object you want to observe is located . To hold this glass strip, the plate has two metal clips.

The vertical position of the plate in relation to the lens lenses is adjustable by means of two screws, also allowing the degree of focus of the sample image to be modulated. In the centre of the plate there is a hole through which the light beam from the light source passes, located at the base of the microscope.

4. Macrometric screw

The macrometric screw allows to adjust the vertical position of the sample in relation to the target. This screw, when turned, makes the microscope tube slide vertically thanks to a system similar to that of a rack.

By means of this movement, it is possible to quickly focus the preparation on the plate.

5. Micrometric screw

The micrometric screw is a mechanism that is used to achieve a more precise focus of the sample to be observed. Although focusing with this screw is done more slowly, it is more accurate than with the macrometric screw.

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

6. Revolver

The revolver is a rotating piece on which the lenses are mounted. Its name is because, when used, it moves and sounds like the revolver of a gun.

By turning the revolver, the lenses pass through the axis of the tube and are positioned in such a way that they allow you to see what is on the plate . Each of the lenses that are screwed onto this piece has a different magnification and by turning the revolver it is possible to choose the most suitable lens 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 to the objectives. This part is what maintains the correct alignment between the lenses that make up the first and second phase of magnification of the image of the sample.

Optical system

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

1. Spotlight or light source

The focus, which provides illumination to the plate, is usually made up of a halogen lamp which is located at the base of the microscope. The light comes out of the bulb and goes into a reflector, sending the light rays to the plate.

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

2. Capacitor

The condenser consists of a system of converging lenses that capture the light beam and concentrate its rays in such a way as to provide greater or lesser contrast .

Normally, the rays emitted by the light source are divergent. Using the capacitor, it is possible to make these rays parallel or even convergent.

In the microscope there is a screw that serves to regulate the light condensation . This screw can be found in different places depending on the model of the device.

3. Diaphragm or iris

The diaphragm is located above the light reflector and below the plate.

By means of this part it is possible to regulate the intensity of the light, opening or closing the diaphragm , in the same way that the human iris does with the light coming from the outside. The optimal point of the diaphragm will vary depending on the sample on the slide and the degree of illumination of the place where the microscope is located.

4. Objectives

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

By turning the revolver clockwise, the lenses are coupled to 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. They are hollow cylinders on top of the microscope that have converging lenses.

These optical elements provide the second stage of image magnification. That is, the image is first magnified by the lenses and then again magnified by the eyepieces .

The combination between the lens used and the eyepieces is what determines the total increase of what is observed on the plate. Depending on whether the microscope has one or two eyepieces, we speak of monocular or binocular microscopes. There are also trinocular microscopes.

6. Optical prism

Some microscopes include optical prisms, which are located inside the device and serve 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 a proper two-dimensional image is obtained.

7. Transformer

The transformer is necessary to be able to connect the microscope to the current , since, normally, the power of the microscope bulb is below the power of the common electric current.

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

Bibliographic references:

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