What is a microscope: the structure and device of a microscope. Features of using a digital microscope in biology lessons Image of a microscope designation of its components

The study of microorganism cells invisible to the naked eye is possible only with the help of microscopes. These devices make it possible to obtain an image of the objects under study, magnified hundreds of times (light microscopes), tens and hundreds of thousands of times (electron microscopes).

A biological microscope is called a light microscope, since it provides the ability to study an object in transmitted light in a bright and dark field of view.

The main elements of modern light microscopes are the mechanical and optical parts (Fig. 1).

The mechanical part includes a tripod, a tube, a turret, a micromechanism box, an object stage, macrometric and micrometric screws.

Tripod consists of two parts: a base and a tube holder (column). Base Rectangular-shaped microscope has four support platforms at the bottom, which ensures a stable position of the microscope on the surface of the desktop. tube holder connects to the base and can be moved in a vertical plane with macro and micrometer screws. Turning the screws clockwise lowers the tube holder, while turning it counterclockwise raises it away from the preparation. At the top of the tube holder is reinforced head with a socket for a monocular (or binocular) nozzle and a guide for a revolving nozzle. The head is attached screw.

Tube - This is a microscope tube that allows you to maintain a certain distance between the main optical parts - the eyepiece and the objective. An eyepiece is inserted into the tube at the top. Modern models of microscopes have an inclined tube.

Turret nozzle is a concave disk with several sockets into which 3 – 4 lenses. By rotating the turret, you can quickly set any lens to its working position under the opening of the tube.

Rice. 1. Microscope device:

1 - base; 2 - tube holder; 3 - tube; 4 - eyepiece; 5 - revolver nozzle; 6 - lens; 7 - subject table; 8 - terminals pressing the preparation; 9 - condenser; 10 – condenser bracket; 11 – handle for moving the condenser; 12 - folding lens; 13 - mirror; 14 - macro screw; 15 - microscrew; 16 - a box with a micrometric focusing mechanism; 17 - head for mounting the tube and turret; 18 - screw for fixing the head

micro-gear box carries on one side a guide for the condenser bracket, and on the other - a guide for the tube holder. Inside the box is the focusing mechanism of the microscope, which is a system of gears.

Subject table serves to place a drug or other object of study on it. The table can be square or round, movable or fixed. The movable table moves in a horizontal plane with the help of two side screws, which allows you to view the drug in different fields of view. On a fixed table for examining an object in different fields of view, the drug is moved by hand. In the center of the object table there is a hole for illumination from below by light rays directed from the illuminator. The table has two spring terminals designed to fix the drug.

Some microscope systems are equipped with a slider, which is necessary when examining the surface of a slide or when counting cells. The drug guide allows the movement of the drug in two mutually perpendicular directions. There is a system of rulers - verniers on the preparation master, with the help of which it is possible to assign coordinates to any point of the object under study.

macrometric screw(macro screw) is used for preliminary orientation of the image of the object in question. Turning the macroscrew clockwise lowers the microscope tube, while turning it counterclockwise raises it.

micrometer screw(microscrew) is used to accurately set the image of the object. The micrometer screw is one of the most easily damaged parts of the microscope, so it must be handled with care - do not rotate it in order to roughly set the image in order to prevent the tube from spontaneously lowering. When the microscrew is fully turned, the tube moves 0.1 mm.

The optical part of the microscope consists of the main optical parts (objective and eyepiece) and an auxiliary lighting system (mirror and condenser).

Lenses(from lat. objektum- subject) - the most important, valuable and fragile part of the microscope. They are a system of lenses enclosed in a metal frame, on which the degree of magnification and numerical aperture are indicated. The outer lens facing the preparation with its flat side is called the frontal lens. It is she who provides the increase. The remaining lenses are called corrective lenses and serve to eliminate the shortcomings of the optical image that arise when examining the object under study.

Lenses are dry and immersion, or submersible. Dry a lens is called, in which there is air between the front lens and the object in question. Dry lenses usually have long focal lengths and magnifications of 8x or 40x. Immersion(submersible) is called a lens in which a special liquid medium is located between the front lens and the preparation. Due to the difference between the refractive indices of glass (1.52) and air (1.0), part of the light rays is refracted and does not enter the eye of the observer. As a result, the image is fuzzy, smaller structures remain invisible. It is possible to avoid scattering of the light flux by filling the space between the preparation and the front lens of the objective with a substance whose refractive index is close to that of glass. These substances include glycerin (1.47), cedar (1.51), castor (1.49), linseed (1.49), clove (1.53), anise oil (1.55) and other substances. Immersion lenses have the designations on the frame: I (immersion) – immersion, HI (homogeneous immersion) is a homogeneous immersion, OI (oilimmersion) or MI- oil immersion. At present, as an immersion liquid, synthetic products are more often used, which correspond in optical properties to cedar oil.

Lenses are distinguished by their magnification. The magnification of lenses is indicated on their frame (8x, 40x, 60x, 90x). In addition, each lens is characterized by a certain working distance. For an immersion lens, this distance is 0.12 mm, for dry lenses with a magnification of 8x and 40x - 13.8 and 0.6 mm, respectively.

Eyepiece(from lat. ocularis- eye) consists of two lenses - eye (upper) and field (lower), enclosed in a metal frame. The eyepiece is used to magnify the image that the lens gives. The magnification of the eyepiece is indicated on its frame. There are eyepieces with a working magnification from 4x to 15x.

When working with a microscope for a long time, a binocular attachment should be used. The nozzle bodies can move apart within 55–75 mm, depending on the distance between the observer's eyes. Binocular attachments often have their own magnification (about 1.5x) and corrective lenses.

Condenser(from lat. condenso- condense, thicken) consists of two or three short-focus lenses. He collects the rays coming from the mirror and directs them to the object. With the help of a handle located under the object stage, the condenser can be moved in a vertical plane, which leads to an increase in the illumination of the field of view when the condenser is raised and a decrease in it when the condenser is lowered. To adjust the intensity of illumination in the condenser there is an iris (petal) diaphragm, consisting of steel sickle-shaped plates. With a fully open diaphragm, it is recommended to consider stained preparations; with a reduced aperture of the diaphragm, unstained preparations are recommended. Below the condenser is flip lens framed, used when working with low magnification lenses, such as 8x or 9x.

Mirror It has two reflective surfaces - flat and concave. It is hinged at the base of the tripod and can be easily rotated. In artificial light, it is recommended to use the concave side of the mirror, in natural light - flat.

Illuminator acts as an artificial light source. It consists of a low-voltage incandescent lamp mounted on a tripod and a step-down transformer. On the transformer case there is a rheostat handle that regulates the incandescence of the lamp and a toggle switch to turn on the illuminator.

In many modern microscopes, the illuminator is built into the base.

The first microscope was an optical device that made it possible to obtain an inverse image of micro-objects and to see very small details of the structure of the substance to be studied. According to its scheme, an optical microscope is a device similar to the design of a refractor, in which light is refracted at the moment of its passage.

A beam of light rays entering the microscope is first converted into a parallel stream, after which it is refracted in the eyepiece. Then information about the object of study enters the visual analyzer of a person.

For convenience, the object of observation is highlighted. For this purpose, a mirror is located at the bottom of the microscope. Light reflects off a mirrored surface, passes through the object in question, and enters the lens. A parallel stream of light goes up to the eyepiece. The degree of magnification of the microscope depends on the parameters of the lenses. Usually this is indicated on the instrument case.

Microscope device

The microscope has two main systems: mechanical and optical. The first includes a stand, a box with a working mechanism, a stand, a holder for a tube, coarse and fine aiming, as well as an object table. The optical system includes a lens, an eyepiece and an illumination unit, which includes a capacitor, a light filter, a mirror and an illumination element.

Modern optical microscopes have not one, but two or even more lenses. This allows you to deal with image distortion called chromatic aberration.

The optical system of the microscope is the main element of the whole structure. The lens determines how much magnification of the object in question will be. It consists of lenses, the number of which depends on the type of device and its purpose. The eyepiece also uses two or even three lenses. To determine the overall magnification of a particular microscope, multiply the magnification of its eyepiece by the same characteristic of the objective.

Over time, the microscope improved, the principles of its operation changed. It turned out that when observing the microcosm, one can use not only the property of light refraction. Electrons can also be involved in the operation of a microscope. Modern electron microscopes make it possible to see individual particles of matter that are so small that light flows around them. For the refraction of electron beams, not magnifying glasses are used, but magnetic elements.

The first concepts of a microscope are formed at school in biology lessons. There, children will learn in practice that with the help of this optical device it is possible to examine small objects that cannot be seen with the naked eye. The microscope, its structure is of interest to many schoolchildren. The continuation of these interesting lessons for some of them is the whole further adult life. When choosing some professions, it is necessary to know the structure of the microscope, since it is the main tool in the work.

The structure of the microscope

The device of optical devices complies with the laws of optics. The structure of a microscope is based on its constituent parts. Units of the device in the form of a tube, an eyepiece, an objective, a stand, a table for the location of the object of study, an illuminator with a condenser have a specific purpose.

The stand holds the tube with the eyepiece, objective. An object table with an illuminator and a condenser is attached to the stand. An illuminator is a built-in lamp or mirror that serves to illuminate the object under study. The image is brighter with an illuminator with an electric lamp. The purpose of the condenser in this system is to regulate the illumination, focusing the rays on the object under study. The structure of microscopes without condensers is known; a single lens is installed in them. In practical work, it is more convenient to use optics with a movable stage.

The structure of the microscope, its design directly depend on the purpose of this device. For scientific research, X-ray and electronic optical equipment is used, which has a more complex device than light devices.

The structure of a light microscope is simple. These are the most accessible optical devices, they are most widely used in practice. An eyepiece in the form of two magnifying glasses placed in a frame, and an objective, which also consists of magnifying glasses tucked into a frame, are the main components of a light microscope. This whole set is inserted into a tube and attached to a tripod, in which is mounted an object table with a mirror located under it, as well as an illuminator with a condenser.

The main principle of operation of a light microscope is to enlarge the image of the object of study placed on the object table by passing light rays through it with their further contact with the objective lens system. The same role is played by the eyepiece lenses used by the researcher in the process of studying the object.

It should be noted that light microscopes are also not the same. The difference between them is determined by the number of optical blocks. There are monocular, binocular or stereo microscopes with one or two optical units.

Despite the fact that these optical devices have been used for many years, they remain incredibly in demand. Every year they improve, become more accurate. The last word has not yet been said in the history of such useful instruments as microscopes.

Functional Parts of the Microscope

The microscope includes three main functional parts:

1. Lighting part

Designed to create a light flux that allows you to illuminate the object in such a way that the subsequent parts of the microscope perform their functions with the utmost accuracy. The illuminating part of a transmitted light microscope is located behind the object under the objective in direct microscopes and in front of the object above lens v inverted. The lighting part includes a light source (a lamp and an electric power supply) and an optical-mechanical system (collector, condenser, field and aperture adjustable / iris diaphragms).

2. Playback part

Designed to reproduce an object in the image plane with the image quality and magnification required for research (i.e., to build such an image that reproduces the object as accurately as possible and in all details with the corresponding optics microscope resolution, magnification, contrast and color reproduction). The reproducing part provides the first stage of magnification and is located after the object to the image plane of the microscope.

The playback part includes lens and intermediate optical system.

Modern microscopes of the latest generation are based on optical systems lenses adjusted for infinity. This requires the additional use of so-called tube systems, which are parallel beams of light emerging from lens, "collect" in the image plane microscope.

3. Visualizing part

Designed to obtain a real image of an object on the retina, film or plate, on the screen of a television or computer monitor with additional magnification (the second stage of magnification).

The imaging part is located between the image plane of the lens and the eyes of the observer ( camera, camera). The visualizing part includes a monocular, binocular or trinocular visual attachment with an observational system ( eyepieces, which work like a magnifying glass).

In addition, this part includes systems of additional magnification (systems of a wholesaler / change of magnification); projection nozzles, including discussion nozzles for two or more observers; drawing devices; image analysis and documentation systems with appropriate adapter (matching) elements.

Structural and technological parts

Modern microscope consists of the following structural and technological parts:

optical;

mechanical;

electric.

The mechanical part of the microscope

The main structural and mechanical unit of the microscope is tripod. The tripod includes the following main blocks: base and tube holder.

Base is a block on which the entire microscope. In simple microscopes, illuminating mirrors or overhead illuminators are installed on the base. In more complex models, the lighting system is built into the base without or with a power supply.

Varieties of microscope bases

base with lighting mirror;

so-called "critical" or simplified lighting;

Keller illumination.

change unit lenses, having the following versions - turret, threaded device for screwing lens, "sled" for threadless fastening lenses using special guides;

focusing mechanism for coarse and fine adjustment of the microscope for sharpness - a mechanism for focusing movement of lenses or tables;

attachment point for interchangeable object tables;

attachment point for focusing and centering movement of the condenser;

attachment point for interchangeable nozzles (visual, photographic, television, various transmitting devices).

Microscopes may use racks to mount nodes (for example, the focusing mechanism in stereo microscopes or the illuminator mount in some models of inverted microscopes).

The purely mechanical part of the microscope is object table, intended for fastening or fixing in a certain position of the object of observation. Tables are fixed, coordinate and rotating (centered and non-centered).

The structure of the microscope

The device of optical devices complies with the laws of optics. The structure of a microscope is based on its constituent parts. Units of the device in the form of a tube, an eyepiece, an objective, a stand, a table for the location of the illuminator with a condenser have a specific purpose.

The structure of a light microscope is simple. These are the most accessible and most widely used in practice. An eyepiece in the form of two magnifying glasses placed in a frame, and an objective, which also consists of magnifying glasses tucked into a frame, are the main components of a light microscope. This whole set is inserted into a tube and attached to a tripod, in which is mounted an object table with a mirror located under it, as well as an illuminator with a condenser.

The main principle of operation of a light microscope is to enlarge the image placed on the object stage by passing light rays through it with their further contact with the objective lens system. The same role is played by the eyepiece lenses used by the researcher in the process of studying the object.