Microscope definition for 3. What is a microscope? Subspecies of light microscopes

A microscope is a device designed to magnify the image of objects of study in order to view the details of their structure hidden to the naked eye. The device provides an increase of tens or thousands of times, which allows you to conduct research that cannot be obtained using any other equipment or device.

Microscopes are widely used in medicine and laboratory research. With their help, dangerous microorganisms and viruses are initialized in order to determine the method of treatment. The microscope is indispensable and is constantly being improved. For the first time, the likeness of a microscope was created in 1538 by the Italian physician Girolamo Fracastoro, who decided to install in series two optical lenses, similar topics that are used in glasses, binoculars, spyglasses and fools. Galileo Galilei worked on improving the microscope, as well as dozens of world famous scientists.

Device

There are many types of microscopes, which differ in design. Most models share a similar design, but with minor technical features.

In the vast majority of cases, microscopes consist of a stand on which 4 main elements are fixed:

Lens.
Eyepiece.
Lighting system.
Subject table.

Lens

The lens is a complex optical system that consists of successive glass lenses. The lenses are made in the form of tubes, inside which up to 14 lenses can be fixed. Each of them enlarges the image by taking it from the surface of the lens in front. Thus, if one magnifies the object by 2 times, the next one will increase the given projection even more, and so on until the object is displayed on the surface of the last lens.

Each lens has its own focusing distance. In this regard, they are tightly fixed in the tube. If any of them is moved closer or farther, it will not be possible to obtain a distinct increase in the image. Depending on the characteristics of the lens, the length of the tube in which the lens is enclosed may vary. In fact, the higher it is, the more magnified the image will be.

Eyepiece

The eyepiece of a microscope also consists of lenses. It is designed so that the operator who works with the microscope can put his eye on it and see the enlarged image on the objective. The eyepiece has two lenses. The first is located closer to the eye and is called the eye, and the second is the field. With the help of the latter, the image magnified by the lens is adjusted for its correct projection onto the retina of the human eye. This is necessary in order to remove defects in the perception of vision by adjusting, since each person focuses at a different distance. The field lens allows you to adjust the microscope to this feature.

Lighting system

To view the object under study, it is necessary to illuminate it, since the lens covers natural light. As a result, looking through the eyepiece, you can always see only a black or gray image. A lighting system has been specially developed for this. It can be made in the form of a lamp, LED or other light source. Most simple models light rays are received from an external source. They are directed to the subject of study with the help of mirrors.

Subject table

The last important and easiest part of the microscope to manufacture is the stage. The lens is pointed at it, since it is on it that the object for study is fixed. The table has a flat surface, which allows you to fix the object without fear that it will move. Even a minimal movement of the object of research under magnification will be huge, so it will not be easy to find the original point that was studied again.

Types of microscopes

Over the long history of the existence of this device, several microscopes have been developed that differ significantly from each other in terms of the principle of operation of microscopes.

Among the most commonly used and sought-after types of this equipment are the following types:

Optical.
Electronic.
Scanning probes.
X-ray.

Optical

An optical microscope is the most budgetary and simple device. This equipment allows you to magnify the image by 2000 times. It's pretty big indicator, which allows you to study the structure of cells, the surface of tissue, find defects in artificially created objects, etc. It should be noted that in order to achieve such high magnification the device must be of very high quality, so it is expensive. The vast majority of optical microscopes are made much simpler and have a relatively low magnification. Educational types of microscopes are represented precisely by optical ones. This is due to their lower cost, as well as not too high magnification.

Typically, an optical microscope has several lenses that are movable on a stand. Each of them has its own degree of magnification. When examining an object, you can move the lens to its working position and examine it at a certain magnification. If you want to get even closer, you just need to switch to an even larger lens. These devices do not have ultra-precise adjustment. For example, if you only need to zoom in a little, then by switching to another lens, you can zoom in dozens of times, which will be excessive and will not allow you to correctly perceive the enlarged image and avoid unnecessary details.

Electron microscope

Electronic is a more advanced design. It provides an image magnification of at least 20,000 times. The maximum magnification of such a device is possible by 10 6 times. The peculiarity of this equipment lies in the fact that instead of a beam of light, like optical ones, they send a beam of electrons. Image acquisition is carried out through the use of special magnetic lenses that respond to the movement of electrons in the column of the device. The beam direction is adjusted using . These devices appeared in 1931. In the early 2000s, they began to combine computer equipment and electron microscopes, which significantly increased the magnification factor, the adjustment range, and made it possible to capture the resulting image.

Electronic devices, for all their merits, have a high price, and require special conditions for operation. To obtain a high-quality clear image, it is necessary that the subject of study be in a vacuum. This is due to the fact that air molecules scatter electrons, which disturbs the clarity of the image and does not allow for fine adjustment. In this regard, this equipment is used in laboratory conditions. Also an important requirement for the use of electron microscopes is the absence of external magnetic fields. As a result, the laboratories in which they are used have very thick insulated walls or are located in underground bunkers.

Such equipment is used in medicine, biology, as well as in various industries.

Scanning probe microscopes

Scanning probe microscope allows you to get an image from an object by examining it with a special probe. The result is a three-dimensional image, with accurate data on the characteristics of objects. This equipment has a high resolution. This is a relatively new equipment that was created several decades ago. Instead of a lens, these devices have a probe and a system for moving it. The image obtained from it is registered by a complex system and recorded, after which a topographic picture of enlarged objects is created. The probe is equipped with sensitive sensors that respond to the movement of electrons. There are also probes that work according to the optical type by increasing due to the installation of lenses.

Probes are often used to obtain data on the surface of objects with complex relief. Often they are lowered into a pipe, holes, as well as small tunnels. The only condition is that the diameter of the probe corresponds to the diameter of the object under study.

This method is characterized by a significant measurement error, since the resulting 3D picture is difficult to decipher. There are many details that are distorted by the computer during processing. The initial data is processed mathematically using specialized software.

X-ray microscopes

The X-ray microscope is laboratory equipment used to study objects whose dimensions are comparable to the X-ray wavelength. Enlargement efficiency this device located between optical and electronic devices. sent to the object under study X-rays, after which the sensitive sensors react to their refraction. As a result, a picture of the surface of the object under study is created. Due to the fact that x-rays can pass through the surface of an object, such equipment allows not only to obtain data on the structure of the object, but also its chemical composition.

X-ray equipment is commonly used to assess the quality of thin coatings. It is used in biology and botany, as well as for the analysis of powder mixtures and metals.

The human eye is designed in such a way that it cannot see an object whose dimensions do not exceed 0.1 mm. In nature, there are objects whose dimensions are much smaller. These are microorganisms, cells of living tissues, elements of the structure of substances and much more.

Even in ancient times, polished natural crystals were used to improve vision. With the development of glassmaking, they began to produce glass lentils - lenses. R. Bacon in the XIII century. advised people from poor eyesight put convex glasses on objects in order to better examine them. At the same time, glasses appeared in Italy, consisting of two connected lenses.

In the XVI century. craftsmen in Italy and the Netherlands, who made spectacle glasses, knew about the property of a two-lens system to give an enlarged image. One of the first such devices was made in 1590 by the Dutchman 3. Jansen.

Despite the fact that the magnifying power of spherical surfaces and lenses was known as early as the 13th century, until the beginning of the 17th century. none of the naturalists even tried to use them to observe the smallest objects that are inaccessible to the naked human eye.

The word "microscope", which comes from two Greek words - "small" and "look", was introduced into scientific use by a member of the Academy "Dei Lyncei" (Rynx-eyed) Desmikian at the beginning of the 17th century.

In 1609, Galileo Galilei, studying the telescope he had designed, also used it as a microscope. To do this, he changed the distance between the lens and the eyepiece. Galileo was the first to come to the conclusion that the quality of lenses for spectacles and telescopes must be different. He created a microscope, choosing such a distance between the lenses, at which not distant, but closely spaced objects increased. In 1614, Galileo examined insects with a microscope.

E. Torricelli, a student of Galileo, adopted the art of grinding lenses from his teacher. In addition to making spotting scopes, Torricelli designed simple microscopes, consisting of one tiny lens, which he obtained from one drop of glass by melting a glass rod over a fire.

In the 17th century the simplest microscopes were popular, consisting of a magnifying glass - a biconvex lens mounted on a stand. The object table, on which the object in question was placed, was also fixed on the stand. At the bottom, under the table, there was a mirror of a flat or convex shape, which reflected the sun's rays onto an object and illuminated it from below. To improve the image, the magnifier was moved relative to the stage using a screw.

In 1665, the Englishman R. Hooke, using a microscope using small glass balls, discovered the cellular structure of animal and plant tissues.

Hooke's contemporary, the Dutchman A. van Leeuwenhoek, made microscopes consisting of small biconvex lenses. They gave 150–300x magnification. With the help of his microscopes, Leeuwenhoek studied the structure of living organisms. In particular, he discovered the movement of blood in blood vessels and red blood cells, spermatozoa, described the structure of muscles, skin scales and much more.

Leeuwenhoek opened new world the world of microorganisms. He described many types of ciliates and bacteria.

Many discoveries in the field of microscopic anatomy were made by the Dutch biologist J. Swammerdam. He studied the anatomy of insects in most detail. In the 30s. 18th century he produced a lavishly illustrated work entitled The Bible of Nature.

Methods for calculating the optical components of a microscope were developed by the Swiss L. Euler, who worked in Russia.

The most common scheme of the microscope is as follows: the object under study is placed on the object table. Above it is a device in which objective lenses and a tube are mounted - a tube with an eyepiece. The observed object is illuminated with a lamp or sunlight, inclined mirror and lens. Apertures installed between the light source and the object limit the luminous flux and reduce the proportion of light in it. scattered light. Between the diaphragms there is a mirror that changes the direction of the light flux by 90°. The condenser concentrates a beam of light on the subject. The lens collects the rays scattered by the object and forms an enlarged image of the object, viewed with the help of an eyepiece. The eyepiece works like a magnifying glass, giving extra magnification. The magnification limits of the microscope are from 44 to 1500 times.

In 1827, J. Amici used an immersion objective in a microscope. In it, the space between the object and the lens is filled with immersion liquid. As such a liquid, various oils(cedar or mineral), water or an aqueous solution of glycerin, etc. Such lenses allow you to increase the resolution of the microscope, improve the contrast of the image.

In 1850, the English optician G. Sorby created the first microscope for observing objects in polarized light. Such devices are used to study crystals, metal samples, animal and plant tissues.

The beginning of interference microscopy was laid in 1893 by the Englishman J. Sirks. Its essence is that each beam, entering the microscope, bifurcates. One of the received rays is directed to the observed particle, the second - past it. In the ocular part, both beams recombine, and interference occurs between them. Interference microscopy allows you to study living tissues and cells.

In the XX century. appeared different kinds microscopes with different purposes, design, allowing to study objects in wide ranges spectrum.

So, in inverted microscopes, the objective is located under the observed object, and the condenser is on top. The direction of the rays is changed with the help of a system of mirrors, and they fall into the eye of the observer, as usual - from the bottom up. These microscopes are designed to study bulky objects that are difficult to place on the stage of conventional microscopes. They are used to study tissue cultures, chemical reactions, determine the melting points of materials. Such microscopes are most widely used in metallography for observing the surfaces of metals, alloys, and minerals. Inverted microscopes can be equipped with special devices for microphotography and microcine filming.

Replaceable light filters are installed on luminescent microscopes, which make it possible to select in the illuminator radiation that part of the spectrum that causes luminescence of the object under study. Special filters pass only luminescence light from the object. Light sources in such microscopes are ultrahigh-pressure mercury lamps that emit ultraviolet rays and rays of the short-wave range of the visible spectrum.

Ultraviolet and infrared microscopes are used to study areas of the spectrum that are inaccessible to the human eye. The optical schemes are similar to those of conventional microscopes. The lenses of these microscopes are made of materials that are transparent to ultraviolet (quartz, fluorite) and infrared (silicon, germanium) rays. They are equipped with cameras that capture visible image and electron-optical converters that turn an invisible image into a visible one.

A stereo microscope provides a three-dimensional image of an object. These are actually two microscopes, made in a single design in such a way that the right and left eyes observe the object from different angles. They have found applications in microsurgery and the assembly of miniature devices.

Comparison microscopes are two conventional combined microscopes with a single ocular system. In such microscopes, two objects can be observed at once, comparing their visual characteristics.

In television microscopes, the image of the drug is converted into electrical signals that reproduce this image on the screen of the cathode ray tube. In these microscopes, you can change the brightness and contrast of the image. With their help, you can study at a safe distance objects that are dangerous for viewing at close range, such as radioactive substances.

The best optical microscopes allow you to magnify the observed objects by about 2000 times. Further magnification is not possible because the light bends around the illuminated object, and if its dimensions are smaller than the wavelength, such an object becomes invisible. The minimum size of an object that can be seen with an optical microscope is 0.2-0.3 micrometers.

In 1834, W. Hamilton established that there is an analogy between the passage of light rays in optically inhomogeneous media and the trajectories of particles in force fields. The possibility of creating an electron microscope appeared in 1924 after L. De Broglie put forward the hypothesis that all types of matter without exception - electrons, protons, atoms, etc. and waves. The technical prerequisites for creating such a microscope appeared thanks to the research of the German physicist X. Bush. He studied the focusing properties of axisymmetric fields and in 1928 developed a magnetic electron lens.

In 1928, M. Knoll and M. Ruska set about creating the first magnetic transmission microscope. Three years later, they captured an image of an object shaped by electron beams. In 1938 M. von Ardenne in Germany and in 1942 V.K. Zworykin in the USA built the first scanning electron microscopes operating on the principle of scanning. In them, a thin electron beam (probe) sequentially moved over the object from point to point.

In an electron microscope, unlike an optical one, electrons are used instead of light rays, and electromagnetic coils or electronic lenses are used instead of glass lenses. The electron gun is the source of electrons for illuminating the object. In it, the source of electrons is a metal cathode. Then the electrons are collected into a beam using a focusing electrode and, under the action of a strong electric field acting between the cathode and anode, gain energy. To create a field, a voltage of up to 100 kilovolts or more is applied to the electrodes. The voltage is regulated in steps and is very stable - in 1-3 minutes it changes by no more than 1-2 millionths of the original value.

Leaving the electron "gun", the electron beam is directed to the object with the help of a condenser lens, scattered on it and focused by the object lens, which creates an intermediate image of the object. The projection lens collects the electrons again and creates a second, even larger image on the fluorescent screen. On it, under the action of electrons hitting it, a luminous picture of the object arises. If you place a photographic plate under the screen, you can photograph this image.

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What is a microscope? Meaning and interpretation of the word mikroskop, definition of the term

microscope -

A compound microscope gives a greater magnification than a simple one, and has a higher resolution. Resolution is the ability to distinguish the details of the sample. An enlarged image, in which details are indistinguishable, provides little useful information.

The compound microscope has a two-stage scheme. One lens system, called the objective, is brought close to the specimen; it creates an enlarged and resolved image of the object. The image is further magnified by another lens system, called an eyepiece, which is placed closer to the observer's eye. These two lens systems are located at opposite ends of the tube.

Working with a microscope. The illustration shows a typical biological microscope. The tripod stand is made in the form of a heavy casting, usually a horseshoe shape. A tube holder is attached to it on a hinge, carrying all the other parts of the microscope. The tube, in which the lens systems are mounted, allows you to move them relative to the sample for focusing. The lens is located at the lower end of the tube. Typically, the microscope is equipped with several objectives of different magnification on the turret, which allows you to set them in working position on the optical axis. The operator, examining the sample, begins, as a rule, with a lens having smallest magnification and the widest field of view, finds the details of interest to him, and then examines them using a lens with a high magnification. The eyepiece is mounted on the end of a retractable holder (which allows you to change the length of the tube when necessary). The entire tube with the objective and eyepiece can be moved up and down to bring the microscope into sharp focus.

The sample is usually taken as a very thin transparent layer or section; it is placed on a rectangular glass plate, called a glass slide, and covered on top with a thinner, smaller glass plate, called a coverslip. The sample is often stained chemicals to increase contrast. The glass slide is placed on the stage so that the sample is above the center hole of the stage. The stage is usually equipped with a mechanism for smooth and precise movement of the sample in the field of view.

Under the object stage is the holder of the third lens system - the condenser, which concentrates the light on the sample. There can be several condensers, and an iris diaphragm is located here to adjust the aperture.

Even lower is an illuminating mirror mounted in a universal joint, which casts the light of the lamp onto the sample, due to which the entire optical system of the microscope creates a visible image. The eyepiece can be replaced with a photo attachment, and then the image will be formed on the film. Many research microscopes are equipped with a dedicated illuminator, so an illuminating mirror is not necessary.

Increase. The magnification of a microscope is equal to the magnification of the objective lens times the magnification of the eyepiece. For a typical research microscope the magnification of the eyepiece is 10, and the magnification of the objectives is 10, 45 and 100. Therefore, the magnification of such a microscope is from 100 to 1000. The magnification of some microscopes reaches 2000. Increasing the magnification even more does not make sense, since the resolution does not improve; on the contrary, the image quality deteriorates.

Theory. A consistent theory of the microscope was given by the German physicist Ernst Abbe at the end of the 19th century. Abbe found that the resolution (the smallest possible distance between two points that are visible separately) is given by

where R is the resolution in micrometers (10-6 m), . is the wavelength of light (created by the illuminator), µm, n is the refractive index of the medium between the sample and the objective, a. - half of the entrance angle of the lens (the angle between the extreme rays of the conical light beam entering the lens). Abbe called the quantity numerical aperture (it is denoted by the symbol NA). It can be seen from the above formula that the resolvable details of the object under study are the smaller, the larger NA and the shorter the wavelength.

Numerical aperture not only determines the resolution of the system, but also characterizes the aperture ratio of the lens: the light intensity per unit area of the image is approximately equal to the square of NA. For a good lens, the NA value is about 0.95. The microscope is usually designed so that its total magnification is approx. 1000NA.

Lenses. There are three main types of lenses, differing in the degree of correction of optical distortions - chromatic and spherical aberrations. Chromatic aberrations are due to the fact that light waves with different wavelengths are focused at different points on the optical axis. As a result, the image is colored. Spherical aberrations are caused by the fact that the light passing through the center of the lens and the light passing through its periphery are focused at different points on the axis. As a result, the image is fuzzy.

Achromatic lenses are currently the most common. In them, chromatic aberrations are suppressed due to the use of glass elements with different dispersions, which ensure the convergence of the extreme rays of the visible spectrum - blue and red - in one focus. A slight coloration of the image remains and sometimes appears as faint green bands around the object. Spherical aberration can only be corrected for one color.

Fluorite lenses use glass additives to improve color correction to such an extent that coloration in the image is almost completely eliminated.

Apochromatic lenses are the lenses with the most complex color correction. They not only almost completely eliminated chromatic aberrations, but also corrected for spherical aberrations not for one, but for two colors. Increase apochromats for of blue color slightly larger than for red, and therefore they require special "compensating" eyepieces.

Most lenses are "dry", ie. they are designed to work in such conditions when the gap between the objective and the sample is filled with air; the NA value for such lenses does not exceed 0.95. If a liquid (oil or, more rarely, water) is introduced between the objective and the sample, an "immersion" objective is obtained with an NA value as high as 1.4, with a corresponding improvement in resolution.

The industry is currently producing various kinds special lenses. These include flat-field objectives for microphotography, stress-free (relaxed) objectives for working in polarized light, and objectives for examining opaque metallurgical specimens illuminated from above.

Capacitors. The condenser forms a light cone directed at the sample. Typically, a microscope is provided with an iris to match the aperture of the light cone with the aperture of the objective, which ensures maximum resolution and maximum image contrast. (Contrast in microscopy has the same importance, as in television technology.) The simplest condenser, quite suitable for most general purpose microscopes, is the two-lens Abbe condenser. Larger aperture objectives, especially oil immersion objectives, require more complex corrected condensers. Oil objectives with maximum aperture require a special condenser that has immersion oil contact with the bottom surface of the glass slide on which the sample rests.

specialized microscopes. In connection with different requirements science and technology have developed microscopes of many special kinds.

A stereoscopic binocular microscope designed to obtain a three-dimensional image of an object consists of two separate microscopic systems. The device is designed for a small increase (up to 100). Commonly used for assembly of miniature electronic components, technical control, surgical operations.

The polarizing microscope is designed to study the interaction of samples with polarized light. Polarized light often makes it possible to reveal the structure of objects that lies beyond the limits of conventional optical resolution.

A reflective microscope is equipped with image-forming mirrors instead of lenses. Since it is difficult to make a mirror lens, there are very few fully reflective microscopes, and mirrors are currently used mainly only in attachments, for example, for microsurgery of individual cells.

Fluorescent microscope - with ultraviolet or blue light illumination of the sample. The sample, absorbing this radiation, emits visible luminescence light. Microscopes of this type are used in biology, as well as in medicine - for diagnosis (especially cancer).

The dark-field microscope makes it possible to circumvent the difficulties associated with the fact that living materials are transparent. The sample in it is viewed under such "oblique" illumination that direct light cannot enter the objective. The image is formed by light diffracted from the object, and as a result, the object appears very light against a dark background (with very high contrast).

The phase contrast microscope is used to examine transparent objects, especially living cells. Thanks to special devices, part of the light passing through the microscope is shifted in phase by half a wavelength relative to the other part, which is the reason for the contrast in the image.

The interference microscope is further development phase contrast microscope. Two light beams interfere in it, one of which passes through the sample, and the other is reflected. With this method, colored images are obtained, which provide very valuable information in the study of living material. See also ELECTRONIC MICROSCOPE; OPTICAL INSTRUMENTS; OPTICS.

Microscope

an optical instrument with one or more lenses for obtaining magnified images of objects not visible to the naked eye. Microscopes are simple and complex. A simple microscope is one lens system. A simple magnifying glass can be considered a simple microscope - a plano-convex lens. A compound microscope (often referred to simply as a microscope) is a combination of two simple ones. A compound microscope gives a greater magnification than a simple one, and has a higher resolution. Resolution is the ability to distinguish the details of the sample. An enlarged image, in which details are indistinguishable, provides little useful information. The compound microscope has a two-stage scheme. One lens system, called the objective, is brought close to the specimen; it creates an enlarged and resolved image of the object. The image is further magnified by another lens system, called an eyepiece, which is placed closer to the observer's eye. These two lens systems are located at opposite ends of the tube. Working with a microscope. The illustration shows a typical biological microscope. The tripod stand is made in the form of a heavy casting, usually a horseshoe shape. A tube holder is attached to it on a hinge, carrying all the other parts of the microscope. The tube, in which the lens systems are mounted, allows you to move them relative to the sample for focusing. The lens is located at the lower end of the tube. Typically, the microscope is equipped with several objectives of different magnification on the turret, which allows you to set them in working position on the optical axis. The operator, when examining a sample, usually starts with the lowest magnification objective and the widest field of view, finds the details of interest, and then examines them using a high magnification objective. The eyepiece is mounted on the end of a retractable holder (which allows you to change the length of the tube when necessary). The entire tube with the objective and eyepiece can be moved up and down to bring the microscope into sharp focus. The sample is usually taken as a very thin transparent layer or section; it is placed on a rectangular glass plate, called a glass slide, and covered on top with a thinner, smaller glass plate, called a coverslip. The specimen is often stained with chemicals to increase contrast. The glass slide is placed on the stage so that the sample is above the center hole of the stage. The stage is usually equipped with a mechanism for smooth and precise movement of the sample in the field of view. Under the object stage is the holder of the third lens system - the condenser, which concentrates the light on the sample. There can be several condensers, and an iris diaphragm is located here to adjust the aperture. Even lower is an illuminating mirror mounted in a universal joint, which casts the light of the lamp onto the sample, due to which the entire optical system of the microscope creates a visible image. The eyepiece can be replaced with a photo attachment, and then the image will be formed on the film. Many research microscopes are equipped with a dedicated illuminator, so an illuminating mirror is not necessary. Increase. The magnification of a microscope is equal to the magnification of the objective lens times the magnification of the eyepiece. For a typical research microscope, the eyepiece magnification is 10, and the objective magnification is 10, 45, and 100. Therefore, the magnification of such a microscope is from 100 to 1000. The magnification of some microscopes reaches 2000. Increasing the magnification even more does not make sense, since the resolution does not improve; on the contrary, the image quality deteriorates. Theory. A consistent theory of the microscope was given by the German physicist Ernst Abbe at the end of the 19th century. Abbe found that the resolution (the smallest possible distance between two points that are visible separately) is given by where R is the resolution in micrometers (10-6 m), . is the wavelength of light (created by the illuminator), µm, n is the refractive index of the medium between the sample and the objective, a. - half of the entrance angle of the lens (the angle between the extreme rays of the conical light beam entering the lens). Abbe called the quantity numerical aperture (it is denoted by the symbol NA). It can be seen from the above formula that the resolvable details of the object under study are the smaller, the larger NA and the shorter the wavelength. Numerical aperture not only determines the resolution of the system, but also characterizes the aperture ratio of the lens: the light intensity per unit area of the image is approximately equal to the square of NA. For a good lens, the NA value is about 0.95. The microscope is usually designed so that its total magnification is approx. 1000NA. Lenses. There are three main types of lenses, differing in the degree of correction of optical distortions - chromatic and spherical aberrations. Chromatic aberrations are due to the fact that light waves with different wavelengths are focused at different points on the optical axis. As a result, the image is colored. Spherical aberrations are caused by the fact that the light passing through the center of the lens and the light passing through its periphery are focused at different points on the axis. As a result, the image is fuzzy. Achromatic lenses are currently the most common. In them, chromatic aberrations are suppressed due to the use of glass elements with different dispersions, which ensure the convergence of the extreme rays of the visible spectrum - blue and red - in one focus. A slight coloration of the image remains and sometimes appears as faint green bands around the object. Spherical aberration can only be corrected for one color. Fluorite lenses use glass additives to improve color correction to such an extent that coloration in the image is almost completely eliminated. Apochromatic lenses are the lenses with the most complex color correction. They not only almost completely eliminated chromatic aberrations, but also corrected for spherical aberrations not for one, but for two colors. The magnification of apochromats for blue is somewhat greater than for red, and therefore special "compensating" eyepieces are needed for them. Most lenses are "dry", ie. they are designed to work in such conditions when the gap between the objective and the sample is filled with air; the NA value for such lenses does not exceed 0.95. If a liquid (oil or, more rarely, water) is introduced between the objective and the sample, an "immersion" objective is obtained with an NA value as high as 1.4, with a corresponding improvement in resolution. Currently, the industry also produces various kinds of special lenses. These include flat-field objectives for microphotography, stress-free (relaxed) objectives for working in polarized light, and objectives for examining opaque metallurgical specimens illuminated from above. Capacitors. The condenser forms a light cone directed at the sample. Typically, a microscope is provided with an iris to match the aperture of the light cone with the aperture of the objective, which ensures maximum resolution and maximum image contrast. (Contrast is just as important in microscopy as it is in television technology.) The simplest condenser, and quite suitable for most general purpose microscopes, is the two-lens Abbe condenser. Larger aperture objectives, especially oil immersion objectives, require more complex corrected condensers. Oil objectives with maximum aperture require a special condenser that has immersion oil contact with the bottom surface of the glass slide on which the sample rests. specialized microscopes. Due to the various requirements of science and technology, microscopes of many special types have been developed. A stereoscopic binocular microscope designed to obtain a three-dimensional image of an object consists of two separate microscopic systems. The device is designed for a small increase (up to 100). Commonly used for assembly of miniature electronic components, technical control, surgical operations. The polarizing microscope is designed to study the interaction of samples with polarized light. Polarized light often makes it possible to reveal the structure of objects that lies beyond the limits of conventional optical resolution. A reflective microscope is equipped with image-forming mirrors instead of lenses. Since it is difficult to make a mirror lens, there are very few fully reflective microscopes, and mirrors are currently used mainly only in attachments, for example, for microsurgery of individual cells. Fluorescent microscope - with ultraviolet or blue light illumination of the sample. The sample, absorbing this radiation, emits visible luminescence light. Microscopes of this type are used in biology, as well as in medicine - for diagnosis (especially cancer). The dark-field microscope makes it possible to circumvent the difficulties associated with the fact that living materials are transparent. The sample in it is viewed under such "oblique" illumination that direct light cannot enter the objective. The image is formed by light diffracted from the object, and as a result, the object appears very light against a dark background (with very high contrast). The phase contrast microscope is used to examine transparent objects, especially living cells. Thanks to special devices, part of the light passing through the microscope is shifted in phase by half a wavelength relative to the other part, which is the reason for the contrast in the image. The interference microscope is a further development of the phase contrast microscope. Two light beams interfere in it, one of which passes through the sample, and the other is reflected. With this method, colored images are obtained, which provide very valuable information in the study of living material. See also ELECTRONIC MICROSCOPE; OPTICAL INSTRUMENTS; OPTICS.

Tudupov Ayur

In his work, the student considers the history of the creation of the microscope. And also describes the experience of creating a simple microscope at home.

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MOU "Mogoytuy secondary school No. 1"

Research work on the topic

"What is a microscope"

Section: physics, technology

Completed by: 2nd grade student Ayur Tudupov

Head: Baranova I.V.

town Mogoytuy

year 2013

Performance

being put forward

student of the 2nd grade MOU MSOSh No. 1 p. Mogoytuy Tudupov Ayur

Research paper title

"What is a microscope?"

Work manager

Baranova Irina Vladimirovna

Brief description (topic) of the work :

This work belongs to experimental studies and is an experimental - theoretical study.

Direction:

Physics, applied research(technique).

Brief description of the research work

Name "What is a microscope?"

Made by Tudupov Ayur

Under the direction ofBaranova Irina Vladimirovna

Research work is devoted to the study of:making a microscope with a drop of water

Where did your interest in this issue come from?I always wanted to have a microscope to see the invisible world.

Where did we look for information to answer our questions?(indicate sources)

Internet
encyclopedias
Teacher consultation

What hypothesis was put forward?you can create a microscope with your own hands from a drop of water.

In the study, we usedthe following methods:

Experiments:

Experiment No. 1 "Creating a microscope."
Working with books.

Conclusions:

At home, you can make a simple microscope from improvised means.
I learned what a microscope is made of.
Creating your own thing is very interesting, especially since the microscope is an interesting thing.

We plan to use photographs to present the results of the study.

Participant Questionnaire

Work plan

Questionnaire of the author of the work - page 1
Table of contents - page 2
Brief description of the project - page 3
Introduction - page 4
Main body - pages 5 – 10
Microscope experiment. - pp. 11-14
Conclusion - page 15
Literature and sources - page 16

INTRODUCTION

From the early age every day, at home, in kindergarten and at school, coming from a walk and after the toilet, after games and before eating, I hear the same thing: “Don't forget to wash your hands!”. And so I thought: “Why wash them so often? Are they really clean?" I asked my mother: “Why do you need to wash your hands?”. Mom answered: “On the hands, as well as on all surrounding objects, there are many microbes that, if they get into the mouth with food, can cause illness.” I looked closely at my hands, but I did not see any germs. And my mother said that microbes are very small and cannot be seen without special magnifying devices. Then I armed myself with a magnifying glass and began to look at everything that surrounded me. But I still didn't see any microbes. My mother explained to me that microbes are so small that they can only be seen under a microscope. We have microscopes at school, but you can't take them home and look for germs. And then I decided to make my own microscope.

Purpose of my research: Assemble your microscope.

Project objectives:

Learn the history of the microscope.
Find out what microscopes consist of and what they can be.
Try to build your own microscope and test it.

My hypothesis : you can create a microscope with your own hands at home from a drop of water and improvised means.

Main part

The history of the creation of the microscope.

Microscope (from Greek - small and look) - an optical device for obtaining enlarged images of objects invisible to the naked eye.

It's fun to look at something through a microscope. No worse computer games and maybe even better. But who invented this miracle - a microscope?

Three hundred and fifty years ago, a spectacle master lived in the Dutch city of Middelburg. He patiently polished glasses, made glasses and sold them to anyone who needed it. He had two children - two boys. They were very fond of climbing into their father's workshop and playing with his instruments and glasses, although this was forbidden to them. And then one day, when the father went away somewhere, the guys made their way, as usual, to his workbench - is there anything new that you can have fun with? Glasses prepared for glasses lay on the table, and in the corner lay a short copper tube: from it the master was going to cut out rings - a frame for glasses. The guys squeezed into the ends of the tube spectacle glass. The older boy put a tube to his eye and looked at the page of an open book that was lying on the table here. To his surprise, the letters became huge. The younger looked into the phone and shouted, amazed: he saw a comma, but what a comma - it looked like a fat worm! The guys aimed the tube at the glass dust left after the glass was polished. And they saw not dust, but a bunch of glass grains. The tube turned out to be downright magical: it greatly enlarged all objects. The children told their father about their discovery. He did not even scold them: he was so surprised by the extraordinary property of the pipe. He tried to make another tube with the same glasses, long and extendable. The new tube increased even better. This was the first microscope. His

accidentally invented in 1590 by the spectacle master Zakharia Jansen, or rather, his children.

Similar thoughts about creating a magnifying device occurred to more than one Jansen: new devices were invented by the Dutchman Jan Lipershey (also a master of spectacles and also from Middelburg), and Jacob Metius. In England, the Dutchman Cornelius Drebbel appeared, who invented a microscope with two biconvex lenses. When rumors spread in 1609 that there was some kind of device for viewing tiny objects in Holland, Galileo understood the general idea of \u200b\u200bthe design the very next day and made a microscope in his laboratory, and in 1612 he had already established the manufacture of microscopes. At first, no one called the created device a microscope, it was called a conspicillium. The familiar words "telescope" and "microscope" were first uttered in 1614 by the Greek Demiscian.

In 1697, the Great Embassy left Moscow from Moscow, which included our Tsar Peter the Great. In Holland, he heard that "a certain Dutchman Leeuwenhoek", who lives in the city of Delft, makes amazing devices at home. With their help, he discovered thousands of animals, more wonderful than the most outlandish overseas animals. And these small animals "nest" in the water, in the air and even in the human mouth. Knowing the king's curiosity, it is not difficult to guess that Peter immediately went to visit. The devices that the king saw were the so-called simple microscopes (it was a magnifier with high magnification). However, Leeuwenhoek managed to achieve a magnification of 300 times, and this exceeded the capabilities of the best compound microscopes of the 17th century, which had both an objective and an eyepiece.

For a long time, the secret of "flea glass", as Leeuwenhoek's device was dismissively called by envious contemporaries, could not be revealed. How could

it turns out that in the 17th century a scientist created devices that, according to some characteristics, are close to devices of the early 20th century? After all, with the technology of that time it was impossible to make a microscope. Leeuwenhoek himself did not reveal his secret to anyone. The secret of "flea glass" was revealed only after 315 years, at the Novosibirsk State Medical Institute at the Department of General Biology and Fundamentals of Genetics. The secret had to be very simple, because Leeuwenhoek for short term managed to make many copies of his single-lens microscopes. Maybe he never polished magnifying lenses? Yes, fire did it for him! If you take a glass thread and place it in the flame of a burner, a ball will appear at the end of the thread - it was Leeuwenhoek who served as a lens. The smaller the ball was, the greater the increase could be achieved ...

In 1697, Peter the Great spent about two hours at Leeuwenhoek - and looked and looked. And already in 1716, during his second trip abroad, the emperor purchased the first microscopes for the Kunstkamera. So a wonderful device appeared in Russia.

A microscope can be called an instrument that reveals secrets. Microscopes looked different in different years, but every year they became more and more complex, and they began to have many details.

This is what Jansen's first microscope looked like:

The first large compound microscope was made by the English physicist Robert Hooke in the 17th century.

This is what microscopes looked like in the 18th century. There were many travelers in the 18th century. And they needed to have a travel microscope that would fit in a bag or jacket pocket. In the first half of the XVIII century. wide use received the so-called "hand" or "pocket" microscope, designed by the English optician J. Wilson. This is how they looked:

What is a microscope made of?

All microscopes consist of the following parts:

Part of a microscope	What is needed for
eyepiece	magnifies the image received from the lens
lens	provides an increase in a small object
tube	telescope, connects lens and eyepiece
adjustment screw	raises and lowers the tube, allows you to zoom in and out of the subject of study
object table	subject matter is placed on it.
mirror	helps guide the light in the hole on the stage.

There is also a backlight and clips.

I also learned what microscopes can be. In the modern world everythingmicroscopescan be divided:

Educational microscopes. They are also called school or children's.
Digital microscopes. The main task of a digital microscope is not just to show an object in an enlarged form, but also to take a photo or shoot a video.
Laboratory microscopes. The main task of a laboratory microscope is to conduct specific research in various fields of science, industry, and medicine.

Building your own microscope

When we were looking for information about the history of microscopes, we found out on one of the sites that you can make your own microscope from a drop of water. And then I decided to try to conduct an experiment to create such a microscope. A small microscope can be made from a drop of water. To do this, you need to take thick paper, pierce a hole in it with a thick needle and carefully place a drop of water on it. The microscope is ready! Bring this drop to the newspaper - the letters have increased. How less drop, the greater the magnification. In the first microscope, invented by Leeuwenhoek, everything was done just like that, only the droplet was glass.

We found a book called "My first scientific experiments" and slightly complicated the model of the microscope. For work I needed:

Glass jar.
Metallized paper (baking foil).
Scissors.
Scotch.
Thick needle.
Plasticine.

When I collected all this, I started to create a microscope model. A little lower I will gradually sign all my work. Of course, I needed a little help from my mother and sister.

MICROSCOPE

REPORT on Biology of a 6th grade student

For a long time, a person lived surrounded by invisible creatures, used their waste products (for example, when baking bread from sour dough, making wine and vinegar), suffered when these creatures caused illnesses or spoiled food supplies, but did not suspect their presence . I didn’t suspect because I didn’t see, but I didn’t see because the sizes of these micro creatures lay much below the limit of visibility that human eye. It is known that a person normal vision at an optimal distance (25-30 cm) can distinguish an object 0.07-0.08 mm in size in the form of a point. Smaller objects cannot be seen. This is determined by the structural features of his organ of vision.

Approximately at the same time when the exploration of space with the help of telescopes began, the first attempts were made to reveal, with the help of lenses, the secrets of the microworld. So, during archaeological excavations in Ancient Babylon, biconvex lenses were found - the simplest optical devices. The lenses were made from polished mountain crystal. It can be considered that with their invention man took the first step on the way to the microworld.

The easiest way to magnify an image of a small object is to observe it with a magnifying glass. A magnifying glass is a converging lens with a small focal length (usually no more than 10 cm) inserted into the handle.

telescope maker Galileo V 1610 In 1993, he discovered that, when wide apart, his spotting scope made it possible to greatly enlarge small objects. It can be considered the inventor of the microscope consisting of positive and negative lenses.
A more advanced tool for observing microscopic objects is simple microscope. When these devices appeared, it is not known exactly. At the very beginning of the 17th century, several such microscopes were made by a spectacle craftsman Zacharias Jansen from Middelburg.

In the essay A. Kircher, released in 1646 year, contains a description the simplest microscope named by him "flea glass". It consisted of a magnifying glass embedded in a copper base, on which an object table was fixed, which served to place the object in question; at the bottom there was a flat or concave mirror, reflecting the sun's rays onto an object and thus illuminating it from below. The magnifying glass was moved by means of a screw to the object table until the image became distinct and clear.

First great discoveries were just made using a simple microscope. In the middle of the 17th century, brilliant success was achieved by the Dutch naturalist Anthony Van Leeuwenhoek. For many years, Leeuwenhoek perfected himself in making tiny (sometimes less than 1 mm in diameter) biconvex lenses, which he made from a small glass ball, which in turn was obtained by melting a glass rod in a flame. Then this glass ball was ground on a primitive grinding machine. During his life, Leeuwenhoek made at least 400 such microscopes. One of them, kept in the University Museum in Utrecht, gives more than 300x magnification, which was a huge success for the 17th century.

At the beginning of the 17th century, there were compound microscopes composed of two lenses. The inventor of such a complex microscope is not exactly known, but many facts indicate that he was a Dutchman. Cornelius Drebel, who lived in London and was in the service of the English King James I. In the compound microscope, there was two glasses: one - the lens - facing the object, the other - the eyepiece - facing the eye of the observer. In the first microscopes, a biconvex glass served as an objective, which gave a real, enlarged, but inverse image. This image was examined with the help of an eyepiece, which thus played the role of a magnifying glass, but only this magnifying glass served to magnify not the object itself, but its image.

IN 1663 microscope Drebel was improved English physicist Robert Hooke, who introduced a third lens into it, called the collective. This type of microscope gained great popularity, and most of the microscopes of the late 17th - first half of the 8th century were built according to its scheme.

Microscope device

A microscope is an optical instrument designed to study magnified images of micro-objects that are invisible to the naked eye.

Main parts light microscope(Fig. 1) are a lens and an eyepiece enclosed in a cylindrical body - a tube. Most models designed for biological research come with three lenses with different focal lengths and a rotary mechanism designed for their quick change - a turret, often called a turret. The tube is located on the top of a massive stand, including the tube holder. Slightly below the objective (or turret with multiple objectives) is an object stage, on which slides with test samples are placed. Sharpness is adjusted using a coarse and fine adjustment screw, which allows you to change the position of the stage relative to the objective.

In order for the sample under study to have sufficient brightness for comfortable observation, the microscopes are equipped with two more optical units (Fig. 2) - an illuminator and a condenser. The illuminator creates a stream of light that illuminates the test preparation. In classical light microscopes, the design of the illuminator (built-in or external) involves a low-voltage lamp with a thick filament, a converging lens, and a diaphragm that changes the diameter of the light spot on the sample. The condenser, which is a converging lens, is designed to focus the illuminator beams on the sample. The condenser also has an iris diaphragm (field and aperture), which controls the intensity of illumination.

When working with light-transmitting objects (liquids, thin sections of plants, etc.), they are illuminated by transmitted light - the illuminator and condenser are located under the object table. Opaque samples should be illuminated from the front. To do this, the illuminator is placed above the object stage, and its beams are directed to the object through the lens using a translucent mirror.

The illuminator can be passive, active (lamp), or both. The simplest microscopes do not have lamps to illuminate samples. Under the table they have a double-sided mirror, in which one side is flat and the other is concave. In daylight, if the microscope is near a window, you can get pretty good illumination using a concave mirror. If the microscope is in a dark room, a flat mirror and an external illuminator are used for illumination.

The magnification of a microscope is equal to the product of the magnification of the objective and the eyepiece. With an eyepiece magnification of 10 and an objective magnification of 40, the total magnification factor is 400. Usually, objectives with a magnification of 4 to 100 are included in a research microscope kit. A typical microscope objective kit for amateur and academic research(x 4, x10 and x 40), provides magnification from 40 to 400.

Resolution is another important characteristic of a microscope, which determines its quality and the clarity of the image it forms. The higher the resolution, the more fine details can be seen with strong increase. In connection with resolution, one speaks of "useful" and "useless" magnification. “Useful” is the maximum magnification at which the maximum image detail is provided. Further magnification (“useless”) is not supported by the resolution of the microscope and does not reveal new details, but it can adversely affect the clarity and contrast of the image. Thus, the limit of useful magnification of a light microscope is not limited overall coefficient magnification of the lens and eyepiece - it can be made as large as desired if desired - but the quality of the optical components of the microscope, that is, the resolution.

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 the objective in inverted ones.
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 resolution, magnification, contrast and color reproduction corresponding to the microscope optics).
The reproducing part provides the first stage of magnification and is located after the object to the image plane of the microscope. The reproducing part includes a lens and an intermediate optical system.
Modern microscopes the latest generation are based on optical systems of lenses corrected for infinity.
This additionally requires the use of so-called tube systems, which “collect” parallel beams of light coming out of the objective in the image plane of the 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 imaging part includes a monocular, binocular or trinocular visual attachment with an observation system (eyepieces that 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 matching elements (photo channel).