Topic: Microscope Work No. 1. Design of a light microscope
Equipment: microscope, permanent specimen, pencil case.
Design of the work: Write down the structure of the microscope, the purpose of its parts, operating rules.
A microscope is an optical-mechanical device that allows you to magnify the object in question (object, specimen).
A microscope distinguishes between optical and mechanical systems.
OPTICAL SYSTEM:
The lens is the most important part of the microscope and is screwed to the bottom of the tube. The lens in a microscope is located in close proximity to the object being examined, which is why it got its name. It consists of a system optical lenses, inserted into a brass frame, and requires very careful handling and careful maintenance (you should never press the lens on the specimen lying on the stage, as this can cause damage or even the lens falling out).
Lens purpose:
1) Construct an image in a microscope tube that is geometrically similar to the object being studied.
2) Enlarge the image one or another number of times.
3) Reveal details invisible to the naked eye. Lenses in quantity 2-3 pieces are screwed into a special device called a revolver (4).
Eyepiece - inserted into top part tube. It looks at the image of the object (not the object), directed upward by the lens. It consists of a system of lenses inserted into a metal cylinder. The eyepiece builds an image, magnifies it, but does not reveal the details of the structure.
Condenser – collects and concentrates all the light reflected from the mirror in the plane of the preparation. The condenser consists of a cylinder (frame) inside which there are 2 lenses. By raising and lowering the condenser you can adjust the illumination of the preparation.
Diaphragm – located at the bottom of the condenser. Just like a condenser, it serves to regulate the intensity of light.
Mirror – used to catch light from a lighting source. It is movably attached under the table, rotating around a horizontal axis. The mirror on one side is flat, with the druse it is concave.
MECHANICAL SYSTEM:
base (tripod) or solid leg (1); box with micromechanism (2) and microscrew (3);
feed mechanism for rough aiming - macroscrew or ratchet (8); stage (4);
screws (5, 6, 12, 13);
head (9); revolver (10); terminals; tube (11);
arc or tube holder (7); Cremalier (macroscrew)– serves for approximate “rough” installation on the background
Microscrew - serves for finer and more accurate aiming.
Subject table– attached to the front of the column on which the object being examined is placed. There are 2 terminals on the table; with their help the drug is fixed. The drug is moved using screws located on the side of the table.
Tube – serves to connect the lens and eyepiece, and is connected to the tripod in such a way that it can be raised and lowered. The tube is moved using two screws: macrometric and micrometric.
Tripod – connects all the above parts of the microscope.
Determining the total magnification of a microscope
Lens |
10x |
15x |
||
Determining focal length
F8=0.9cm~1cm
F40=1.2mm~1mm
Auxiliary equipment (remember the names):
1. slides and coverslips;
2. a glass or flask for water, a pipette;
3. razor (blade), dissecting needles;
4. strips of filter paper, napkin.
Rules for working with a microscope:
You should work with the microscope without hasty or sudden movements. When working with a microscope, maintain cleanliness and accuracy. Protect the microscope from dust and contamination.
1. The microscope is carried with two hands: one hand - by the tube holder, the other - from below by the base.
2. The microscope is installed directly in front of the worker, opposite his left eye, and does not move.
3. WITH right side the necessary tools, materials and a sketchbook are located.
4. Before starting work, use a soft (preferably cambric) cloth to wipe off dust from the eyepiece, lens, and mirror.
5. Having placed the microscope on permanent place, lower the microscope tube using a microscrew, while looking from the side of the microscope, so that the low-magnification objective is at a distance of ~ 1 cm from the slide.
6. Each object is studied first at low magnification, and then transferred to high magnification.
7. Natural light is used for lighting, but not direct, solar or electric, preferably matte.
8. Lighting installation:
a) remove the frosted glass under the condenser; b) install the condenser with the front lens at the level of the microscope stage (under-
remove it with a screw; c) open the diaphragm completely;
d) install a low magnification lens; e) by moving the mirror, direct the light so that, having passed through the lens, a beam of light
It completely illuminated the plane of the lens entrance pupil.
9. After installing the lighting, we place the specimen on the stage so that the object in question is under the front lens of the low-power objective. Then lower the tube again using the ratchet so that there is a distance between the front lens of the small objective and the cover glass of the specimen 3-4 mm (when lowering the tube, you need to look not at the eyepiece, but at the side of the lens).
10. Looking into the eyepiece with your left eye (without closing your right eye), smoothly turn right hand Screw the ratchet, find the image, and at the same time with your left hand we give the object a favorable position.
11. When switching to high magnification, we move the revolver and in place of low magnification we put a 40 lens X . At high magnification, by rotating the microscrew, achieve a clear image (rotate the microscrew no more than half a turn). Remember that when you rotate the micro- and macroscrew clockwise, the lens tube goes down, and when you rotate it in the opposite direction, it goes up.
12. After work, we install the low magnification lens again.
13. Only at low magnification should the specimen be removed from the microscope stage. After use, the microscope should be wiped with a napkin and placed under the case.
Work No. 2. Working with a microscope at low and high magnification.
Design of the work: Write down the preparation technique.
Preparations and their preparation.
Drugs can be temporary or permanent. When making a temporary preparation, the object is placed in a drop clear liquid- water or glycerin. Ta-
These drugs cannot be stored for long periods of time. In the case when the object of study is placed in a drop of hot glycerin-gelatin or Canada balsam, which hardens when cooled. The result is a permanent preparation that can be stored for years.
On practical exercises in plant anatomy, students use both permanent and temporary preparations made by themselves. To make a temporary drug you need:
o using a pipette, place a drop of water or glycerol in the center of the slide; o use a dissecting needle to place the object in a drop of the prepared liquid;
o Carefully cover the object with a thin (fragile) cover glass. The top of the cover glass should remain dry, i.e. water should not go beyond it. Excess water is removed using a strip of filter paper. If there is not enough liquid under the glass, you can add it by moving the pipette to the edge of the coverslip without lifting it.
o the preparation often contains air bubbles, which enter it along with the object or when the cover glass is abruptly, carelessly lowered, and with their contours interfere with the study of the object. They can be removed by adding water to one side of the cover slip while simultaneously removing it from the opposite side, or by lightly tapping the cover slip with a dissecting needle, holding the specimen almost vertically.
USE IN SCHOOL
The acquired knowledge and practical skills are used in the school biology course in the lesson “Introduction to magnifying devices” and in the process of teaching the entire course of botany and other biological disciplines.
HOMEWORK: Learn the structure of a microscope, the rules of working with it and the technique of preparing preparations.
The term "microscope" has Greek roots. It consists of two words, which when translated mean “small” and “I look.” The main role of the microscope is its use in examining very small objects. At the same time, this device allows you to determine the size and shape, structure and other characteristics of bodies invisible to the naked eye.
History of creation
There is no exact information in history about who was the inventor of the microscope. According to some sources, it was designed in 1590 by the father and son Janssens, eyeglass makers. Another contender for the title of inventor of the microscope is Galileo Galilei. In 1609, these scientists presented an instrument with concave and convex lenses to the public at the Accademia dei Lincei.
Over the years, the system for viewing microscopic objects has evolved and improved. A huge step in its history was the invention of a simple achromatically adjustable two-lens device. This system was introduced by the Dutchman Christian Huygens in the late 1600s. The eyepieces of this inventor are still in production today. Their only drawback is the insufficient width of the field of view. In addition, compared to the design of modern instruments, Huygens eyepieces have an inconvenient location for the eyes.
A special contribution to the history of the microscope was made by the manufacturer of such devices, Anton Van Leeuwenhoek (1632-1723). It was he who attracted the attention of biologists to this device. Leeuwenhoek made small-sized products equipped with one, but very strong lens. Such devices were inconvenient to use, but they did not double the image defects that were present in compound microscopes. The inventors were able to correct this shortcoming only 150 years later. Along with the development of optics, image quality in composite devices has improved.
Improvement of microscopes continues to this day. Thus, in 2006, German scientists working at the Institute of Biophysical Chemistry, Mariano Bossi and Stefan Hell, developed a new optical microscope. Due to the ability to observe objects with dimensions of 10 nm and three-dimensional high-quality 3D images, the device was called a nanoscope.
Classification of microscopes
Currently exists big variety instruments designed to examine small objects. Their grouping is based on various parameters. This may be the purpose of the microscope or the method of illumination adopted, the structure used for optical design etc.
But, as a rule, the main types of microscopes are classified according to the resolution of microparticles that can be seen using this system. According to this division, microscopes are:
- optical (light);
- electronic;
- X-ray;
- scanning probes.
The most widely used microscopes are the light type. There is a wide selection of them in optical stores. With the help of such devices, the main tasks of studying a particular object are solved. All other types of microscopes are classified as specialized. They are usually used in a laboratory setting.
Each of the above types of devices has its own subtypes, which are used in one area or another. In addition, today it is possible to buy a school microscope (or educational), which is a system entry level. Professional devices are also offered to consumers.
Application
What is a microscope for? The human eye, being a special biological optical system, has a certain level of resolution. In other words, there is a smallest distance between observed objects when they can still be distinguished. For a normal eye, this resolution is within 0.176 mm. But the sizes of most animal and plant cells, microorganisms, crystals, the microstructure of alloys, metals, etc. are much smaller than this value. How to study and observe such objects? This is where different types of microscopes come to the aid of people. For example, optical devices make it possible to distinguish structures in which the distance between elements is at least 0.20 microns.
How does a microscope work?
A device with which to the human eye consideration of microscopic objects becomes available has two main elements. They are the lens and the eyepiece. These parts of the microscope are fixed in a movable tube located on a metal base. There is also an object table on it.
Modern types of microscopes are usually equipped with a lighting system. This, in particular, is a condenser with an iris diaphragm. A mandatory set of magnifying devices includes micro- and macroscrews, which are used to adjust the sharpness. The design of microscopes also includes a system that controls the position of the condenser.
In specialized, more complex microscopes, other additional systems and devices are often used.
Lenses
I would like to start describing the microscope with a story about one of its main parts, that is, the lens. They are a complex optical system that increases the size of the object in question in the image plane. The design of the lenses includes a whole system of not only single, but also two or three lenses glued together.
The complexity of such an optical-mechanical design depends on the range of tasks that must be solved by one or another device. For example, the most complex microscope has up to fourteen lenses.
The lens consists of the front part and the systems following it. What is the basis for constructing an image of the required quality, as well as determining the working condition? This is a front lens or their system. Subsequent parts of the lens are necessary to provide the required magnification, focal length and image quality. However, such functions are only possible in combination with a front lens. It is also worth mentioning that the design of the subsequent part affects the length of the tube and the height of the lens of the device.
Eyepieces
These parts of the microscope are an optical system designed to construct the necessary microscopic image on the surface of the retina of the observer's eye. The eyepieces contain two groups of lenses. The one closest to the researcher’s eye is called the ocular one, and the farthest one is the field one (with its help, the lens builds an image of the object being studied).
Lighting system
The microscope has a complex design of diaphragms, mirrors and lenses. With its help, uniform illumination of the object under study is ensured. In the very first microscopes, this function was carried out. As optical instruments improved, they began to use first flat and then concave mirrors.
With the help of such simple details, rays from the sun or lamp were directed to the object of study. In modern microscopes it is more advanced. It consists of a condenser and a collector.
Subject table
Microscopic preparations requiring examination are placed on a flat surface. This is the object table. Different kinds microscopes may have this surface, designed in such a way that the object of study will be rotated towards the observer horizontally, vertically or at a certain angle.
Operating principle
In the first optical device, a system of lenses gave an inverse image of micro-objects. This made it possible to discern the structure of the substance and the smallest details that were subject to study. The principle of operation of a light microscope today is similar to the work carried out by refracting telescope. In this device, light is refracted as it passes through the glass part.
How do modern light microscopes magnify? After a beam of light rays enters the device, they are converted into a parallel stream. Only then does the refraction of light occur in the eyepiece, due to which the image of microscopic objects is magnified. Next, this information arrives in the form necessary for the observer in his
Subtypes of light microscopes
Modern ones classify:
1. By complexity class for research, work and school microscopes.
2. By area of application: surgical, biological and technical.
3. By types of microscopy: devices of reflected and transmitted light, phase contact, luminescent and polarization.
4. In the direction of the light flux into inverted and direct.
Electron microscopes
Over time, the device designed to examine microscopic objects became more and more sophisticated. Such types of microscopes appeared in which a completely different operating principle, independent of the refraction of light, was used. In the process of using the newest types of devices, electrons were involved. Such systems make it possible to see individual parts of matter so small that light rays simply flow around them.
What is a microscope for? electronic type? It is used to study the structure of cells at the molecular and subcellular levels. Similar devices are also used to study viruses.
The device of electron microscopes
What underlies the operation of the latest instruments for viewing microscopic objects? How electron microscope different from light? Are there any similarities between them?
The operating principle of an electron microscope is based on the properties that electrical and magnetic fields. Their rotational symmetry can have a focusing effect on electron beams. Based on this, we can answer the question: “How does an electron microscope differ from a light microscope?” It, unlike an optical device, does not have lenses. Their role is played by appropriately calculated magnetic and electric fields. They are created by turns of coils through which current passes. In this case, such fields act similarly. When the current increases or decreases, the focal length of the device changes.
Concerning schematic diagram, then in an electron microscope it is similar to the circuit of a light device. The only difference is that the optical elements are replaced by similar electrical ones.
Magnification of an object in electron microscopes occurs due to the process of refraction of a beam of light passing through the object under study. At various angles, the rays enter the plane of the objective lens, where the first magnification of the sample occurs. Next, the electrons travel their way to the intermediate lens. In it there is a smooth change in the increase in the size of the object. The final image of the material under study is produced by the projection lens. From it the image hits the fluorescent screen.
Types of electron microscopes
Modern types include:
1. TEM, or transmission electron microscope. In this installation, an image of a very thin object, up to 0.1 microns thick, is formed by the interaction of an electron beam with the substance under study and its subsequent magnification by magnetic lenses located in the lens.
2. SEM, or scanning electron microscope. Such a device makes it possible to obtain an image of the surface of an object with high resolution, on the order of several nanometers. Using additional methods such a microscope provides information that helps determine chemical composition near-surface layers.
3. Tunneling scanning electron microscope, or STM. With help of this device The relief of conductive surfaces with high spatial resolution is measured. In the process of working with STM, a sharp metal needle is brought to the object being studied. In this case, a distance of only a few angstroms is maintained. Next, a small potential is applied to the needle, resulting in a tunnel current. In this case, the observer receives a three-dimensional image of the object under study.
Microscopes "Leevenguk"
In 2002, it appeared in America new company, engaged in the production of optical instruments. Its product range includes microscopes, telescopes and binoculars. All these devices are distinguished by high image quality.
The company's head office and development department are located in the USA, in Fremond (California). But as for production facilities, they are located in China. Thanks to all this, the company supplies the market with advanced and high-quality products at an affordable price.
Do you need a microscope? Levenhuk will offer the required option. In assortment optical technology The company has digital and biological instruments to magnify the object being studied. In addition, the buyer is offered designer models in a variety of colors.
Levenhuk microscope has extensive functionality. For example, an entry-level teaching device can be connected to a computer and is also capable of video recording of the research being carried out. The Levenhuk D2L model is equipped with this functionality.
The company offers biological microscopes of various levels. These include simpler models and new items that are suitable for professionals.
The first concepts about a microscope are formed at school during biology lessons. There, children learn in practice that with the help of this optical device they can examine small objects that cannot be seen with the naked eye. The microscope and its structure are of interest to many schoolchildren. Continuation of these interesting lessons for some of them the whole future becomes adulthood. When choosing some professions, it is necessary to know the structure of a microscope, since it is the main tool in the work.
Microscope structure
The design of optical instruments complies with the laws of optics. The structure of a microscope is based on its components. The components of the device in the form of a tube, an eyepiece, a lens, a stand, a table for placing the object of study, and an illuminator with a condenser have a specific purpose.
The stand holds a tube with an eyepiece and lens. An object stage 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 electric lamp. The purpose of the condenser in this system is to regulate illumination and focus the rays on the object being studied. 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 a microscope and its design directly depend on the purpose of this device. For scientific research X-ray and electron optical equipment is used, which has a more complex structure than light devices.
The structure of a light microscope is simple. These are the most affordable optical devices and are most widely used in practice. An eyepiece in the form of two magnifying glasses placed in a frame, and a lens, which also consists of magnifying glasses tucked into a frame, are the main components of a light microscope. This entire set is inserted into a tube and attached to a tripod, in which a stage with a mirror located under it, as well as an illuminator with a condenser, is mounted.
The main principle of operation of a light microscope is to magnify the image of an object of study placed on the stage by passing light rays through it and then hitting them on the objective lens system. The same role is played by the eyepiece lenses, which are 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 units. There are monocular, binocular or stereomicroscopes with one or two optical units.
Despite the fact that these optical instruments have been in use for many years, they remain incredibly in demand. Every year they improve and become more accurate. Not said yet the last word in the history of such useful instruments as microscopes.
Light is an optical instrument designed to study objects invisible to the naked eye. Light microscopes can be divided into biological and stereoscopic. Biological microscopes are also called laboratory, medical are microscopes for examining thin transparent samples in transmitted light. Biological laboratory microscopes have high magnification, the most common is 1000x, but some models can have magnification up to 1600x.
Stereoscopic microscopes are used to examine opaque objects (coins, minerals, crystals, electrical circuits, etc.) in reflected light. Stereoscopic microscopes have a small magnification (20x, 40x, some models up to 200x), but at the same time they create a three-dimensional image of the observed object. This effect is very important, for example, when studying the surface of a metal.
In this article we will take a more detailed look at the structure of a biological laboratory microscope, for which we will consider separately the optical, mechanical and lighting systems of the microscope.
2. Nozzle
4. Base
5. Turret
6. Lenses
7. Coordinate table
8. Stage
9. Iris diaphragm condenser
10. Lighter
11. Switch (on/off)
12. Macrometric (rough) focusing screw
13. Micrometric (fine) focusing screw
Microscope optical system
The optical system of the microscope consists of lenses located on the turret head, and eyepieces. With the help of the optical system, the image of the sample under study is actually formed on the retina of the eye. Note that the image obtained using a biological microscope is inverted.
MAGNIFICATION = LENS MAGNIFICATION X EYE MAGNIFICATION.
Mechanical microscope system
The mechanical system consists of a tube, a tripod, a stage, focusing mechanisms, and a turret.
Focusing mechanisms are used to focus the image. Coarse (macrometric) focusing screw used when working with low magnifications, and fine (micrometric) focusing screw– when working at high magnifications.
The object under study is placed on the stage. There are several types of object tables: fixed (stationary), movable, coordinate and others. By using coordinate table You can move the test sample to horizontal plane along the X and Y axes.
On turret head lenses are located. By turning it, you can select one lens or another, and thus change the magnification.
An eyepiece is inserted into the tube.
Microscope lighting system
The lighting system consists of a light source, a condenser and a diaphragm.
The light source can be built-in or external. Biological microscopes have bottom illumination.
Using a condenser and a diaphragm, you can adjust the illumination of the preparation. Condensers There are single-lens, double-lens, and three-lens. By raising or lowering the condenser, you respectively condense or scatter the light falling on the sample. Diaphragm May be iris with a smooth change in hole diameter or stepped with several holes of different diameters. Thus, by reducing or increasing the diameter of the hole, you accordingly limit or increase the flow of light falling on the object under study.
Microscope is optical instrument to study objects invisible to the naked eye. The microscope (Fig. 1) distinguishes between mechanical and optical parts. The mechanical part of the device consists of a leg with a tube holder attached to it, on which a tube, eyepieces and lenses are mounted (lenses are changed using a revolving device), a stage and a lighting apparatus with a mirror. The tube is movably attached to the tube holder and is raised and lowered using two screws: a micrometric screw is used to pre-set the focus; micrometer screw - for fine focusing. The object table is equipped with a device that allows you to move the specimen in different directions in the horizontal plane. The lighting apparatus consists of a condenser and a diaphragm, which are located between the mirror and the table.
Rice. 1. Biological microscope:
1 - eyepieces;
2 - binocular attachment;
3 - head for attaching a revolver with a seat for changing tubes;
4 - screw for fastening the binocular attachment;
5 - revolver on a sled;
6 - lens;
7 - object table;
8 and 9 - lamb for longitudinal (8) and transverse (9) movement of the drug driver;
10 - aplanatic condenser of direct and oblique illumination;
11 - table centering screws;
12 - mirror;
13 - micromechanism wing;
14 - condenser bracket;
15 - head of the screw fixing the upper part of the stage;
16 - box with micromechanism;
17 - leg;
18 - rough movement screw;
19 - tube holder.
The diaphragm controls the intensity of light entering the condenser. The condenser can be moved in the vertical direction, changing the intensity of the light flux entering the lens. Lenses are systems of mutually centered lenses that provide a reverse magnified image of an object. The magnification of the lenses is indicated on the frame (X10, X20, X40, X90). There are two types of lenses: dry and immersion (submersible). The immersion lens is first lowered into immersion oil using a macroscrew under eye control, and then, by manipulating the microscrew, a clear image of the object is achieved. The eyepiece is an optical system that magnifies the image obtained through the lens. The eyepiece magnifications are indicated on the frame (X5, etc.). The total magnification of a microscope is equal to the magnification of the objective multiplied by the magnification of the eyepiece.
Rice. 2. MBI-1 microscope with OI-19 illuminator.
You can work with the microscope in daylight and artificial light, using a special lighting apparatus as a light source (Fig. 2). When working with a condenser, a flat mirror is used, regardless of the light source. A concave mirror is operated without a condenser. At daylight the condenser is raised to the level of the object stage; in the case of an artificial one, it is lowered until the light source appears in the plane of the specimen. See also Microscopic technique, Microscopy.
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