THE PARTS OF THE LIGHT MICROSCOPE AND THEIR FUNCTIONS - SCIENCE - 2024

The main parts of the optical microscope are the foot, tube, nosepiece, column, stage, carriage, coarse and fine screw, eyepieces, objective, condenser, diaphragm and transformer.

The optical microscope is an optical lens-based microscope that is also known by the name of light microscope or bright field microscope. It can be monocular or binocular, which means that it can be seen with one or two eyes.

Parts of the optical microscope

With the use of a microscope we can amplify the image of an object through a system of lenses and light sources. By manipulating the passage of a ray of light between the lenses and the object, we can see the image of this magnified.

It can be divided into two parts under the microscope; the mechanical system and the optical system. The mechanical system is how the microscope is built and the parts in which the lenses are installed. The optical system is the system of the lenses and how they manage to amplify the image.

The light microscope generates a magnified image using various lenses. First, the objective lens is a magnification of the actual magnified image of the sample.

Once we get that enlarged image, the eyepiece lenses form an enlarged virtual image of the original sample. We also need a point of light.

In optical microscopes there is a light source and a condenser that focuses it on the sample. When light has passed through the sample, the lenses are responsible for magnifying the image.

Parts and functions of the light microscope

- Mechanic system

The foot or base

It constitutes the base of the microscope and its main support, it can have different shapes, the most common being rectangular and Y-shaped.

The tube

It is cylindrical in shape and inside is black to avoid the discomfort of light reflection. The end of the tube is where the eyepieces are placed.

The revolver

It is a rotating piece in which the objectives are screwed. When we rotate this device, the objectives pass through the axis of the tube and are placed in the working position. It is called stirring because of the noise the pinion makes when it fits into a fixed place.

The spine or arm

The column or arm, in some cases known as the loop, is the part at the back of the microscope. It is attached to the tube in its upper part and in the lower part it is attached to the foot of the device.

Platen

The stage is the flat metal piece on which the sample to be observed is placed. It has a hole in the optical axis of the tube that allows the light beam to pass in the direction of the sample.

The stage can be fixed or rotatable. If it is rotating, it can be centered or moved with circular movements using screws.

The car

Allows you to move the sample in an orthogonal motion, back and forth, or right to left.

The coarse screw

The device hooked to this screw makes the microscope tube slide vertically thanks to a rack system. These movements allow the preparation to focus quickly.

Micrometer screw

This mechanism helps to bring the specimen into sharp and precise focus through the almost imperceptible movement of the stage.

The movements are through a drum that has divisions of 0.001 mm. And that also serves to measure the thickness of docked objects.

- Parts of the optical system

Eyepieces

They are the lens systems closest to the observer's sight. They are hollow cylinders in the upper part of the microscope fitted with converging lenses.

Depending on whether there is one or two eyepieces, the microscopes can be monocular or binocular.

goals

They are the lenses that are regulated by the revolver. They are a converging lens system in which several objectives can be attached.

The attachment of the objectives is carried out in an increasing way according to their magnification in a clockwise direction.

The objectives are magnified on one side and are also distinguished by a colored ring. Some of the lenses do not focus the preparation in the air and need to be used with oil immersion.

Condenser

It is a converging lens system that captures light rays and concentrates them on the sample, providing more or less contrast.

It has a regulator to adjust the condensation through a screw. The location of this screw may vary depending on the microscope model

Lighting source

The lighting is made up of a halogen lamp. Depending on the size of the microscope, it may have a higher or lower voltage.

The small microscopes most used in laboratories have a voltage of 12 V. This illumination is located at the base of the microscope. The light leaves the bulb and passes into a reflector that sends the rays in the direction of the stage

Diaphragm

Also known as an iris, it is located on the reflector of light. Through this you can regulate the intensity of the light by opening or closing it.

Transformer

This transformer is necessary to plug the microscope into the electric current since the power of the bulb is less than the electric current.

Some of the transformers also have a potentiometer that is used to regulate the intensity of the light passing through the microscope.

All parts of the optical system in microscopes are made up of lenses corrected for chromatic and spherical aberrations.

Chromatic aberrations are due to light being composed of radiation that is unevenly deflected.

Achromatic lenses are used so that the colors of the sample are not changed. And spherical aberration occurs because the rays that pass through the end converge at a closer point, so a diaphragm is placed to allow the rays to pass in the center.

References

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