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, and a table for placing the 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 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 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.
Materials and equipment. Microscopes: MBR-1, BIOLAM, MIKMED-1, MBS-1; set of permanent microslides
Microscope- This optical instrument, which allows you to obtain a reverse image of the object being studied and examine small details of its structure, the dimensions of which lie beyond the resolution of the eye.
What is resolution?
Imagine that with the naked eye a person can distinguish two very close lines or points only if the distance between them is at least 0.10 mm (100 microns). If this distance is less, then the two lines or points will merge into one. Thus, the resolution human eye equal to 100 µm. Therefore, the greater the resolution of the lens, the more details of the structure of the observed object can be revealed. For the lens (x8) the resolution is 1.68 microns, for the lens (x40) - 0.52 microns.
The best light microscope improves the capability of the human eye by about 500 times, i.e. its resolving power is about 0.2 µm or 200 nm.
Resolution and magnification are not the same thing. If you use a light microscope to take photographs of two lines located at a distance of less than 0.2 microns, then no matter how you enlarge the image, the lines will merge into one. Available high magnification, but does not improve its resolution.
Distinguish useful And useless increase. By useful we mean such an increase in the observed object that it is possible to reveal new details of its structure. Useless is a magnification in which, by magnifying an object hundreds or more times, it is impossible to detect new structural details. For example, if an image obtained using a microscope (useful!) is enlarged many times more by projecting it onto a screen, then new, finer details of the structure will not be revealed, but only the size of existing structures will increase accordingly.
Typically used in teaching laboratories light microscopes, in which microslides are examined using natural or artificial light. Most common light biological microscopes: BIOLAM, MIKMED, MBR (biological working microscope), MBI (biological research microscope) and MBS (biological stereoscopic microscope). They provide magnification ranging from 56 to 1350 times. Stereomicroscope(MBS) provides a truly three-dimensional perception of a micro-object and magnifies from 3.5 to 88 times.
There are two systems in a microscope: optical And mechanical(Fig. 1). TO optical system include lenses, eyepieces and a lighting device (a condenser with a diaphragm and a light filter, a mirror or an electric light).
Picture 1. Appearance microscopes Biomed 1 and Biomed 2
Lens - one of the most important parts of a microscope, since it determines useful magnification of the object. The lens consists of a metal cylinder with lenses built into it, the number of which can vary. The magnification of the lens is indicated by numbers on it. For educational purposes, x8 and x40 lenses are usually used. The quality of a lens is determined by its resolution.
The lens requires very careful handling, especially for lenses with high magnification, because they have a working distance, i.e. the distance from the cover glass to the front lens is measured in tenths of a millimeter. For example, the working distance for a lens (x40) is 0.6 mm.
Eyepiece much simpler than a lens. It consists of 2-3 lenses mounted in a metal cylinder. Between the lenses there is a constant aperture that defines the boundaries of the field of view. The lower lens focuses the image of the object constructed by the lens in the plane of the diaphragm, and the upper one serves directly for observation. The magnification of the eyepieces is indicated on them by numbers: x7, x10, x15. The eyepieces do not reveal new structural details, and in this regard, their increase useless. Thus, the eyepiece, like a magnifying glass, gives a direct, virtual, enlarged image of the observed object, constructed by the lens.
For determining general microscope magnification should increase the magnification lens to magnify the eyepiece. For example, if the eyepiece provides 10x magnification and the objective provides 20x magnification, then the total magnification is 10x20 = 200x.
Lighting device consists of a mirror or electric illuminator, a condenser with an iris diaphragm and a light filter, located under the object stage. They are designed to illuminate an object with a beam of light.
Mirror serves to direct light through the condenser and the opening of the stage onto the object. It has two surfaces: flat and concave. In diffuse light laboratories, a concave mirror is used.
Electric lighting is installed under the condenser in the stand socket.
Condenser consists of 2-3 lenses inserted into a metal cylinder. When it is raised or lowered using a special screw, the light falling from the mirror onto the object is condensed or scattered, respectively.
Iris diaphragm located between the mirror and the condenser. It serves to change the diameter of the light flux directed by the mirror through the condenser to the object, in accordance with the diameter of the front lens of the lens and consists of thin metal plates. Using a lever, you can either connect them, completely covering the lower condenser lens, or separate them, increasing the flow of light.
Ring with frosted glass or light filter reduces the illumination of the object. It is located under the diaphragm and moves in horizontal plane.
Mechanical system The microscope consists of a stand, a box with a micrometer mechanism and a micrometer screw, a tube, a tube holder, a coarse aiming screw, a condenser bracket, a condenser moving screw, a revolver, and a sample stage.
Stand- This is the base of the microscope.
Box with micrometer mechanism, built on the principle of interacting gears, is fixedly attached to the stand. The micrometer screw serves to slightly move the tube holder, and, consequently, the lens over distances measured in micrometers. A full turn of the micrometer screw moves the tube holder by 100 microns, and a turn of one division lowers or raises the tube holder by 2 microns. To avoid damage to the micrometer mechanism, it is allowed to turn the micrometer screw in one direction no more than half a turn.
Tube or a tube- a cylinder into which eyepieces are inserted from above. The tube is movably connected to the head of the tube holder; it is fixed with a locking screw in a certain position. By loosening the locking screw, the tube can be removed.
Revolver designed for quickly changing lenses that are screwed into its sockets. The centered position of the lens is ensured by a latch located inside the revolver.
Coarse aiming screw used to significantly move the tube holder, and, consequently, the lens in order to focus the object at low magnification.
Subject table intended for placing the drug on it. In the middle of the table there is a round hole into which the front lens of the condenser fits. There are two springy terminals on the table - clamps that secure the drug.
Condenser bracket movably connected to the micrometer mechanism box. It can be raised or lowered by a screw that rotates a gear that fits into the grooves of a comb-cut rack.
The main task that is solved by the mechanical part is quite simple - ensuring the fastening and movement of the optical part of the microscope and the object.
Subject tables designed for fastening the observation object in a certain position. The main requirements are related to the rigidity of the mounting of the tables themselves, as well as to the fixation and coordination (orientation) of the object (preparation) relative to the lens.
The table is mounted on a special bracket. For ease of operation, the tables are structurally made fixed and movable.
Fixed stages are usually used in the simplest models of microscopes. The movement of the object on them is carried out with the help of the observer’s hands for rapid movement during express diagnostics. The drug is fixed on the table using spring legs or using a special drug holder device.
For mechanical movement or rotation of an object under the microscope lens, movable(Fig. 32) tables. The drug is fixed and moved using a drug driver. Coordinate movement of an object along two X-Y axes(or only one X at a time) is carried out using a handle (usually double coaxial) manually or by an electric motor (usually a stepper). The latter are called “scanning tables.” On the table along the guides along the X and Y axes there are scales with verniers for monitoring the position and linear measurement of movement in the horizontal plane.
Focusing mechanism: coarse and fine focusing. The focusing mechanism provides movement of the table or lens to establish a certain distance between the object of observation and optical part microscope This distance guarantees a sharp image of the subject. “Focusing” is carried out by two adjustments – coarse and fine. Each adjustment has its own mechanism and its own handle. The control handles can be spaced apart or combined, but must be located on the sides of the microscope: on the right and left in pairs.
Usually rough focusing(adjustment) is carried out by a pair of large handles (Fig. 31), located on either side of the tripod. They make a "rough" movement of the lens towards or away from the object. The minimum amount of movement is 1 mm per revolution. At the same time, coarse focusing is working for those studies where the microscope magnification is no more than 400 x.
Precise Focus(adjustment) is carried out by a pair of small knobs, which usually move the table or lens towards the object by 0.01 -0.05 mm in one revolution. The amount of movement per revolution depends on design features microscopes from various companies.
As a rule, a scale is applied to one of the fine focusing handles, which allows you to control the vertical movement of the microscope relative to the object of observation.
For example, the domestic microscope MIKMED-2 has a coarse focusing movement of up to 30 mm, while one turn of the handle provides a movement of 2.5 mm, fine focusing is carried out within 2.5 mm with one turn of 0.25 mm on one of the handles For precise focusing, there is a scale with a division value of 0.002 mm.
The functional purpose of the focusing movement is much greater than is usually assigned to it. You can't do without precise focusing:
If the microscope magnification is more than 400 x;
When working with immersion lenses;
When working with lenses that do not provide a sharp image across the entire observed field;
If throughout the entire visible field the object is uneven in thickness or has volume.
The combination (coaxial arrangement) of both handles greatly simplifies the work, while at the same time complicating the design and increasing the cost of the microscope.
Unit for fastening and moving the condenser. Condenser, as an independent unit, is a connecting element between the lighting system (light source) and the microscope (lens and imaging part).
The condenser mounting unit is located under the object stage. It looks like a bracket with a socket. Designed for installing the condenser, fixing it and centering it, i.e. moving it in a horizontal plane perpendicular to the optical axis of the microscope.
In addition, the assembly has a guide for focusing movement (movement) of the condenser vertically, along the optical axis.
No matter how the condenser is installed in the socket - from the side, from above or from below - it is firmly secured with a locking screw, which prevents it from falling out, on the one hand, and ensures a centered position during operation, on the other.
Centering screws ensure alignment of the illumination beam from the light source and the optical axis of the microscope (Kohler illumination adjustment). This is very important stage lighting settings in a microscope, affecting the uniformity of illumination and the accuracy of object reproduction, as well as the contrast and resolution of elements in the image of the object.
Focusing (height adjustment) of the condenser is carried out using a handle on the bracket and, like centering, affects the operation of the entire optical part of the microscope.
The condenser may be stationary. Usually such a design is inherent educational microscopes . These microscopes are used for routine work where the use of additional methods contrasting, and the object does not require more detailed examination.
Lens mount. There are several types of lens mounts in a microscope:
Screwing the lens directly into the tube (usually on educational “school” microscopes);
“sled” - mounting lenses using a special threadless device (guide);
Revolving device with several slots.
Currently, the most common type of lens mount is a revolving device (turret head) (Fig. 33).
The lens mount unit in the form of a revolving device performs the following functions:
Changing the magnification in the microscope by rotating the head, into each socket of which a lens of a certain magnification is screwed;
Fixed installation of the lens in the working position;
guaranteed centering of the optical axis of the lens relative to the optical axis of the microscope as a whole, including the lighting system.
The turret device can be 3, 4, 5, 6 or 7-cavity, depending on the complexity class of the microscope and the tasks it solves.
In microscopes that use differential interference contrast, the turret above the socket has one or more slots for installing a guide with a prism.
IN educational microscopes Lenses are usually attached in such a way that replacing them is difficult (that is, they are made non-removable).
The order of the lenses must be strictly observed: from lower magnification to higher magnification, while the turret moves clockwise.
As a rule, when assembling microscopes, the operation of selecting lenses is performed - equipment . This allows you not to lose the image of the object from the field of view when moving from one magnification to another.
And one more condition must be provided by the revolving device - parfocality . The nest of a revolver, or rather its outer surface, is a material base surface for measuring the height of the lens and the length of the lens tube (microscope). The lens must be screwed into the socket so that there is no gap between it and the turret. At the same time, the calculated values of all assembly optical elements in the microscope, as well as their design and technological support, are provided. This means that if a sharp image of an object is obtained with one lens, then when moving to another within the depth of field of the lens, a sharp image of the object is maintained.
Parfocality in a set of lenses is ensured by the design of the microscope and manufacturing technology. In the absence of this condition, when moving from one lens to another, significant subfocus by image sharpness.
Mounting unit for eyepieces (tube) in modern microscopes it is a bracket with a socket in which different kinds nozzles: visual attachments (monocular and binocular (Fig. 34)), photometric And spectrophotometric , microphoto - And adapter devices for video systems . In addition, the following can be installed in this slot: comparison nozzles , drawing machines , screen attachments , and incident light illuminators . The devices are secured with a locking screw.
It is impossible to imagine a model of a modern microscope without documentation systems
. In practice, this is a binocular attachment with access to a photo or television system.
Structurally, the eyepiece mounting unit can be equipped with an additional optical-mechanical module of interchangeable magnification, called “Optovar”. As a rule, it has several stages of magnification from less than 1 to 2.5 x, but there are also options with one stage. Typically the module is located between the visual head and the turret, thereby providing additional magnification for both the visual channel and the photo output. Certainly, highest value this is for the photo channel.
MICROSCOPE OPTICS
Optical components and accessories provide the main function of the microscope - creating an enlarged image of the object under consideration with a sufficient degree of reliability in shape, size ratio and color. In addition, the optics of the microscope must provide such magnification, contrast and resolution of elements that will allow observation, analysis and measurement that meet the requirements of clinical diagnostic practice methods.
The main optical elements of the microscope are: lens , eyepiece , condenser . Auxiliary elements - lighting system , wholesaler, visual And photo attachments with optical adapters and projectors.
Microscope lens designed to create an enlarged image of the object in question with the required quality, resolution and color rendition.
The classification of lenses is quite complex and is related to the objects for which the microscope is intended to study; it depends on the required accuracy of object reproduction, taking into account the resolution and color rendition in the center and across the field of view.
Modern lenses have a complex design; the number of lenses in optical systems reaches 7-13. In this case, calculations are based mainly on glasses with special properties and crystal fluorite or glasses similar to it in basic physical and chemical properties.
There are several types of lenses based on the degree of aberration correction:
Corrected in the spectral range:
Monochromatic lenses (monochromats) designed for use in a narrow spectral range, in practice they work well at one wavelength. Aberrations are corrected in a narrow spectral range. Monochromats were widespread in the 60s during the development of photometric research methods and the creation of equipment for research in the ultraviolet (UV) and infrared (IR) regions of the spectrum.
Achromatic lenses (achromats) designed for use in the spectral range 486-656 nm. These lenses eliminate spherical aberration, chromatic position aberration for two wavelengths (green and yellow), coma, astigmatism and partially spherochromatic aberration.
The image of the object has a slightly bluish-reddish tint. Technologically, the lenses are quite simple - a small number of lenses, technologically advanced for the manufacture of glass grade, radius, diameter and thickness of the lenses. Relatively cheap. Included in a set of microscopes that are intended for routine work and training.
Due to the simplicity of the design (only 4 lenses), achromats have the following advantages:
High light transmittance, which is necessary when carrying out photometric measurements and luminescent studies;
Providing conditions that are difficult to combine when calculating: a large working distance when working with a lens with a cover glass that clearly exceeds the standard thickness and at the same time the desire to maintain resolution, which is necessary when working on inverted microscopes.
The disadvantages include the fact that field aberrations in pure achromats are most often corrected by 1/2-2/3 of a field, i.e. without refocusing, observation within 1/2-2/3 of the center of vision is possible. This increases the observation time, because requires constant refocusing to the edge of the field.
Apochromatic lenses. U apochromats the spectral region is expanded and achromatization is performed for three wavelengths. In addition to position chromatism, spherical aberration, coma and astigmatism, secondary spectrum and spherochromatic aberration are also corrected quite well.
This type of lens was developed after lenses made of crystals and special glasses were introduced into the optical design of the lens. Number of lenses in optical design apochromats go up to 6. Compared to achromats, apochromats usually have higher numerical apertures, produce a clear image and accurately convey the color of the object.
Field aberrations in pure apochromats are corrected even less than in achromats, most often by 1/2 of a field, i.e. without refocusing, observation within 1/2 of the center of vision is possible.
Apochromats are usually used for particularly delicate and important studies, and especially where high-quality microphotography is required.
A light microscope is an optical instrument designed to examine objects invisible to the naked eye. Light microscopes can be divided into two main groups: biological and stereoscopic. also often called laboratory, medical - these 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.
Used to study opaque volumetric 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 (three-dimensional) image of the observed object. This effect is very important, for example, when examining the surface of metal, minerals and stones, as it allows you to detect depressions, cracks and other structural elements.
In this article we will look at the structure in more detail, 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, eyepieces, and may also include a prism block. With the help of the optical system, the image of the sample under study is actually formed on the retina of the eye. Therefore, it is important to pay attention to the quality of the optics used in the optical design of the microscope. Note that the image obtained using a biological microscope is inverted.
MAGNIFICATION = LENS MAGNIFICATION X EYE MAGNIFICATION.
Today, many children's microscopes use a Barlow lens with a magnification factor of 1.6x or 2x. Its use allows you to further smoothly increase the magnification of the microscope over 1000x. The benefit of such a Barlow lens is very doubtful. Her practical use results in significant degradation in image quality, and may be useful in rare cases. But manufacturers of children's microscopes successfully use it as a marketing ploy to promote their products, because often parents, without thoroughly understanding technical parameters microscope, choose it according to the erroneous principle “the higher the magnification, the better.” And, of course, not a single professional laboratory microscope will be equipped with such a lens, which will obviously deteriorate the image quality. Professional microscopes use exclusively a combination of different eyepieces and objectives to change magnification.
In the case of a Barlow lens, the formula for calculating the microscope magnification takes the following form:
MAGNIFICATION = LENS MAGNIFICATION X EYE CARRY MAGNIFICATION X BARLOW LENS MAGNIFICATION FACTOR.
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. The coarse (macrometric) focusing screw is used when working with low magnifications, and the fine (micrometric) focusing screw is used when working with high magnifications. Children's and school microscopes, as a rule, have only coarse focusing. However, you choose a biological microscope for laboratory research, having fine focusing is a must. Please note that the figure shows an example of a biological microscope with separate fine and coarse focusing, while depending on the design features, many microscopes may have coaxial screws for macro- and micrometric focus adjustment. Note that stereo microscopes only have coarse focusing.
Depending on the design features of the microscope, focusing can be accomplished by moving the object stage in a vertical plane (up/down) or the microscope tube with its optical unit also in a vertical plane.
The object under study is placed on the stage. There are several types of object tables: fixed (stationary), movable, coordinate and others. The most comfortable for work is the coordinate table, with which you can move the sample under study in a horizontal plane along the X and Y axes.
The lenses are located on the turret. By turning it, you can select one lens or another, and thus change the magnification. Inexpensive children's microscopes may be equipped with non-replaceable lenses, while professional biological microscopes use replaceable lenses that are screwed into the turret using a standard thread.
An eyepiece is inserted into the microscope tube. In the case of a binocular or trinocular attachment, it is possible to adjust the interpupillary distance and diopter correction to suit individual anatomical features observer. In the case of children's microscopes, the “pest” Barlow lens can first be installed in the tube, and then the eyepiece can be installed in it.
Microscope lighting system
The lighting system consists of a light source and a diaphragm.
The light source can be built-in or external. Biological microscopes have bottom illumination. Stereoscopic microscopes can be equipped with bottom, top and side illumination for different types lighting of drugs. Children's biological microscopes may have additional top (side) illumination, the practical use of which, in fact, is usually meaningless.
Using a condenser and a diaphragm, you can adjust the illumination of the preparation. Condensers can be single-lens, double-lens, or three-lens. By raising or lowering the condenser, you respectively condense or scatter the light falling on the sample. The diaphragm can be iris with a smooth change in the diameter of the hole 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. We also note that the condenser can be equipped with a filter holder for installing various light filters.
This is where you can finish your first acquaintance with the microscope. We hope that the above material will help you decide on your goals.
You can deliver in Kharkov, Kyiv or any other city in Ukraine in our OpticalMarket store, having previously received professional advice from our specialists.
A microscope is an optical device that allows you to obtain an inverse image of the object being studied and examine small details of its structure, the dimensions of which lie beyond the resolution of the eye.
Resolution microscope gives a separate image of two lines close to each other. The naked human eye has a resolution of about 1/10 mm or 100 microns. The best light microscope improves the capability of the human eye by about 500 times, i.e. its resolving power is about 0.2 µm or 200 nm.
Resolution and magnification are not the same thing. If you use a light microscope to take photographs of two lines located at a distance of less than 0.2 microns, then no matter how you enlarge the image, the lines will merge into one. You can get high magnification, but not improve its resolution.
Distinguish useful And useless increase. By useful we mean such an increase in the observed object that it is possible to reveal new details of its structure. Useless is a magnification in which, by magnifying an object hundreds or more times, it is impossible to detect new structural details. For example, if the image obtained using a microscope is enlarged many times more by projecting it onto a screen, then new, finer details of the structure will not be revealed, but only the size of existing structures will increase accordingly.
Typically used in teaching laboratories light microscopes, in which microslides are examined using natural or artificial light. Most common light biological microscopes: BIOLAM, MIKMED, MBR (biological working microscope), MBI (biological research microscope) and MBS (biological stereoscopic microscope). They provide magnification ranging from 56 to 1350 times. Stereomicroscope(MBS) provides a truly three-dimensional perception of a micro-object and magnifies from 3.5 to 88 times.
There are two systems in a microscope: optical And mechanical. TO optical system include lenses, eyepieces and a lighting device (a condenser with a diaphragm and a light filter, a mirror or an electric light).
The structure of light microscopes is shown in Fig. 1.
Rice. 1. Design of light microscopes:
A - MIKMED-1; B - BIOLAM.
1 - eyepiece, 2 - tube, 3 - tube holder, 4 - coarse aiming screw, 5 - micrometer screw, 6 - stand, 7 - mirror, 8 - condenser, iris diaphragm and light filter, 9 - stage, 10 - revolving device, 11 - lens, 12 - collector lens body, 13 - socket with lamp, 14 - power supply.
Lens - one of the most important parts of a microscope, since it determines useful magnification of the object. The lens consists of a metal cylinder with lenses built into it, the number of which can vary. The magnification of the lens is indicated by numbers on it. IN educational purposes Usually x8 and x40 lenses are used. The quality of a lens is determined by its resolution.
Eyepiece much simpler than a lens. It consists of 2-3 lenses mounted in a metal cylinder. Between the lenses there is a constant aperture that defines the boundaries of the field of view. The lower lens focuses the image of the object constructed by the lens in the plane of the diaphragm, and the upper one serves directly for observation. The magnification of the eyepieces is indicated on them by numbers: x7, x10, x15. The eyepieces do not reveal new structural details, and in this regard, their increase useless. Thus, the eyepiece, like a magnifying glass, gives a direct, virtual, enlarged image of the observed object, constructed by the lens.
For determining general microscope magnification The objective magnification should be multiplied by the eyepiece magnification.
Lighting device consists of a mirror or electric illuminator, a condenser with an iris diaphragm and a light filter, located under the object stage. They are designed to illuminate an object with a beam of light.
Mirror serves to direct light through the condenser and the opening of the stage onto the object. It has two surfaces: flat and concave. In diffuse light laboratories, a concave mirror is used.
Electric lighting is installed under the condenser in the stand socket.
Condenser consists of 2-3 lenses inserted into a metal cylinder. When it is raised or lowered using a special screw, the light falling from the mirror onto the object is condensed or scattered, respectively.
Iris diaphragm located between the mirror and the condenser. It serves to change the diameter of the light flux directed by the mirror through the condenser to the object, in accordance with the diameter of the front lens of the lens and consists of thin metal plates. Using a lever, you can either connect them, completely covering the lower condenser lens, or separate them, increasing the flow of light.
Ring with frosted glass or light filter reduces the illumination of the object. It is located under the diaphragm and moves in a horizontal plane.
Mechanical system The microscope consists of a stand, a box with a micrometer mechanism and a micrometer screw, a tube, a tube holder, a coarse aiming screw, a condenser bracket, a condenser moving screw, a revolver, and a sample stage.
Stand- This is the base of the microscope.
Box with micrometer mechanism, built on the principle of interacting gears, is fixedly attached to the stand. The micrometer screw serves to slightly move the tube holder, and, consequently, the lens over distances measured in micrometers. A full turn of the micrometer screw moves the tube holder by 100 microns, and a turn of one division lowers or raises the tube holder by 2 microns. To avoid damage to the micrometer mechanism, it is allowed to turn the micrometer screw in one direction no more than half a turn.
Tube or a tube- a cylinder into which eyepieces are inserted from above. The tube is movably connected to the head of the tube holder; it is fixed with a locking screw in a certain position. By loosening the locking screw, the tube can be removed.
Revolver designed for quickly changing lenses that are screwed into its sockets. The centered position of the lens is ensured by a latch located inside the revolver.
Coarse aiming screw used to significantly move the tube holder, and, consequently, the lens in order to focus the object at low magnification.
Subject table intended for placing the drug on it. In the middle of the table there is a round hole into which the front lens of the condenser fits. There are two springy terminals on the table - clamps that secure the drug.
Condenser bracket movably connected to the micrometer mechanism box. It can be raised or lowered by a screw that rotates a gear that fits into the grooves of a comb-cut rack.
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