Васильев Д.В., (c)
Прикреплённый файл - BASIC INFORMATION NECESSARY FOR WORKING WITH A LIGHT MICROSCOPE
TABLE OF CONTENTS
THE HISTORY OF THE CREATION OF THE MICROSCOPE 2
THE MAIN TYPES OF LIGHT MICROSCOPES USED FOR BIOLOGICAL RESEARCH 6
BASIC METHODS OF LIGHT MICROSCOPY 8
BASIC CONCEPTS OF OPTICS USED FOR LIGHT MICROSCOPES 10
OPTICAL LIGHT MICROSCOPE DEVICE 15
RULES FOR WORKING WITH A MICROSCOPE 28
RECOMMENDATIONS FOR THE CARE OF MICRO-OPTICS 31
LITERARY INDEX 32
With great inventions, it often happens that it is very difficult to unambiguously name their authors. As a rule, such inventions do not arise out of nowhere, their appearance is preceded by other discoveries and inventions that create the necessary material and scientific basis. Thanks to this, many inventors can claim authorship, and in order to determine the authorship, it is necessary to trace the entire history of the invention. In this case, it is extremely difficult to talk about one inventor and it is only possible to trace the main stages during which various people made this or that invention.
This rule also applies to the invention of the microscope. But in the literature, despite the fact that there are works showing the complexity of this problem [Katsnelson, 1963; Gurikov,1980], they often, sometimes undeservedly, try to name a specific author of the invention [Sobol, 1943; Sobol, 1957; Vinogradova, 2012], Therefore, the purpose of this article is to try to understand the question of authorship for the invention of the microscope and to tell about the stages of creating this optical device.
Stage 1 – the creation of lenses and the study of the main optical phenomena.
To create a light microscope, lenses are necessary, and the history of lens production goes back to the very distant past. So an ancient large flat-convex lens made of rock crystal in Nineveh 2500 years BC has come down to our times. Glass lenses began to be manufactured around 600-400 years before the Birth of Christ, in Mesopotamia [Vinogradova, 2012]. In Europe, in Sweden, a double lens (convex on both sides) with a diameter of 5 cm was also found made in 500 AD. The list of discovered ancient lenses can be continued for as long as you want, but now, alas, you can only guess about the scope of their application at that time. The first and rather detailed description of lenses as an object for image magnification appears only in the works of Roger Bacon in the 13th century [Tolansky, 1971; Gurikov, 1983]. However, the first works on optics appear in antiquity. It is known that Euclid and Aristotle experimentally established the main optical phenomena — rectilinear propagation of light, independence of light beams, reflection from a mirror surface and refraction of light at the boundary of two transparent media. But although ancient scientists were interested in the nature and properties of light, nothing is yet known about the creation of optical devices by them. Despite the existence of a sufficient number of theoretical works on optics, practical optics, especially in terms of the use of lenses, developed extremely poorly until the late Middle Ages [Gurikov, 1980]. And only in the 13th century the first glasses appeared in Italy.
Stage 2-creation of complex optical devices.
The first ideas about creating complex optical devices from lenses to increase the image are found in the manuscripts of Leonardo da Vinci. In his manuscripts there are many graphic constructions of the course of rays in lenses, an experimental method for determining optical aberrations is given. From the works of the scientist, it can be learned that he may be the creator of not only a single-lens, but also a two-lens (with two convex (collective) lenses) optical device for image magnification [Gurikov, 1980]. There are drawings of such a device, but whether it was created, unfortunately, is unknown.
The business started by Leonardo da Vinci was continued by his compatriot Giovanni Battista de la Porta (1535-1615). Thus, in the book "De refractione" ("On Refraction"), he tries to study optical systems consisting of a combination of convex and concave lenses, i.e., the scheme of the telescope,which will later be created by Galileo [Dorfman, 1974; Gurikov, 1980]. Unfortunately, in the literature devoted to the creation of a microscope, neither Leonardo Davinci nor Giovanni Battista are almost never mentioned. It is generally believed that the first devices that can be called microscopes, if one wishes, were invented either by the Dutch master of glasses Zachariah Jansen, or by the Italian scientist Galileo Galilei [Sobol, 1945; Katsnelson, 1963; Tolansky, 1971; Gurikov, 1983; Vinogradova, 2012]. But they cannot definitely be considered the inventors of the microscope. First of all, these inventors did not seek to create a microscope at all, and were not engaged in subsequent research of the microcosm. They simply created optical devices that could be used for microscopy if desired. Moreover, they have competitors who claim to be the first in the creation of two-lens devices for image magnification. There is information that Johann (Hans) Lippersgey, (a master of making glasses) who lived next door to the Jansen family, also created at the same time an optical device very similar to the device of Master Jansen. But he tried to use it not as a microscope, but as a telescope and tried to patent it, but he did not receive a patent because the right to invent similar devices at the same time was claimed by masters - Zachariah Jansen and Jacob Metius from Alkmaar [Borellus, 1665; Sobol, 1941; Sobol, 1945; Katsnelson, 1963; Gurikov, 1983]. Information about the invention and existence of the telescope reached Galileo Galilei. Thanks to this information, Galileo created his own optical instrument, but at the same time using the scientific knowledge accumulated in optics by this time. Later (1609-1610), Galileo, improving the telescope he designed, tried to use it as a kind of microscope by changing the distance between the concave eyepiece and the convex lens [Tolansky, 1971; Gurikov, 1983]. However, his device was extremely inconvenient to handle and was subsequently forgotten and lost.
Thus, four people at once claim the right to be called the inventors of an optical device that could be used as a microscope. But the instruments of Galileo, Zachariah Jansen, Lippersgey and Metius, unfortunately, have never been used to study the microcosm. However, thanks to them, the stage of active development of optics began, and devices designed specifically for the study of the microcosm were invented, but these were devices of a different design.
Stage 3-creation of optical devices intended for microscopy.
The theoretical basis for the creation of such microscopes was laid by the work of Johannes Kepler. He suggested using an eyepiece and a lens in the form of single convex lenses, which gave an inverse (inverted) image [Sobol, 1945; Katsnelson, 1963]. The first device for studying the microcosm according to the Kepler scheme was created by Cornelius Jacobson Drebbel — a Dutch inventor who was engaged in research in the field of chemistry and optics. His optical device was first presented to the public in 1619 in London, and brought him wide fame. Many modern devices for microscopy also work on the principles proposed by Drebbel. The microscopes made by him spread in Europe, having penetrated from England to France and Italy [Sobol, 1943; Sobol, 1957]. Due to the fact that it was his model of the microscope that became widely distributed for the first time, he is also considered one of the inventors of the microscope. In any case, Christian Huygens wrote: “In 1621, Drebel, a Dutchman who lived in London, was known as the owner of such complex microscopes and was considered by everyone to be their inventor" [Sable, 1945]. Christian himself was also interested in optics. He is the author of the "Treatise on Light" (the wave theory of light), which was published in 1678. He also wrote the theory of reflection, refraction and double refraction. And it is Huygens who is considered by many to be the father of the principles of modern microscopy [Sobol, 1945; Katsnelson, 1963]. But, despite his great contribution to the development of optical devices, Huygens still did not invent the microscope. But thanks to his theory of the undulating propagation of light in 1665, Robert Hooke, an English naturalist, created his own microscope. Moreover, he supplemented the theoretical scientific basis necessary for the creation of microscopes by creating a hypothesis about the transverse nature of light waves, which he outlined in the book "Micrography". The main postulates of this theory were subsequently confirmed by experience, and are used in modern microscopy. R. Hooke also owns the first successes associated with the use of the microscope in scientific biological research [Sobol, 1945; Katsnelson, 1963; Vinogradova, 2012].
A special and very noticeable trace in the history of the development of microscopy was left by Anthony Van Leeuwenhoek, who lived in the Netherlands, in the city of Delft from 1632 to 1723 [Churilovsky, 1966; Vinogradova, 2012]. He is often called the inventor of the microscope. But the merit of Leeuwenhoek is not the creation of a microscope. I must say that not only the device itself, but also the name of the device appeared even before the birth of Leeuwenhoek. It was proposed in 1625 by I. Faber, a member of the Roman "Academy of the Sharp-Sighted" ("Akudemia dei lincei") [Vinogradova, 2012]. The merit of Leeuwenhoek is that he independently made and used simple (single-lens) microscopes in his research, which gave an image magnification of up to three hundred times. It was Anthony Van Leeuwenhoek who first, based on the experience of his observations, compiled a description of the kingdom of microscopic organisms and bacteria. He actively popularized his discoveries and because of this he is often called the inventor of the microscope. In the future, the light microscope was improved many times: In 1668 Eustachy Divini, having attached a field lens to the eyepiece, invented an eyepiece of a modern type [Vermel, 1970; Vinogradova, Zakharov, 1918]. In 1673, Jan Hevelius introduced a micro-screw, in 1716, G. Hertel proposed placing a small mirror under the object table to direct light rays into the microscope tube [Vinogradova, Zakharov, 1918]. As a result, microscopes began to be made from five main parts, which are currently part of the modern optical microscope. These are: 1. the housing; 2. the light source, the beam from which is focused on the lens; 3. the object table; 4. the lens; 5. the eyepiece.
To date, the design of the microscope has become somewhat more complicated, although the basic scheme remains the same. A conventional light microscope used in laboratories for biological research usually has several interchangeable lenses installed in a revolver. A pair of eyepieces is also used to provide binocular perception of the studied drug. Projection or photo eyepieces designed for projecting images onto the screen or photographing can be attached to it as options. The design of light microscopes largely depends on the methods of light microscopy, determined by the goals of research and the characteristics of the objects under study. Therefore, in addition to the usual universal optical microscopes found in schools and laboratories, there are a large number of specialized microscopes:
- Comparison microscopes. They provide a visual comparison of the two drugs.
- Contact microscopes. They are used for microscopic studies of the structures of individual sections of biological tissues. To do this, the microscope lens is pressed against the object under study.
- Stereo microscopes allow you to examine an object from different angles of view. Thanks to this, a person perceives the image three-dimensionally.
- Ultraviolet and infrared microscopes designed to study objects in the ultraviolet or infrared part of the light spectrum that is invisible to the naked eye. To do this, they are equipped with a fluorescent screen, on which an image of the studied drug is formed. A camera or an electron-optical converter can also be used.
- Polarizing microscopes. They allow us to detect inhomogeneities (anisotropy) of the structure of objects by studying the contrast of the image or color changes. With their help, it is possible to analyze molecular compounds of organic and synthetic types, as well as to study various natural objects with a crystal structure.
- Interference microscopes that make it possible to study objects with low refractive indices of light and extremely small thickness. In an interference microscope, the light beam entering the microscope is bifurcated. Part passes through the object under study, and the other passes by. In the ocular part, both beams connect and interfere, which allows you to see the structure under study.
- Luminescent microscopes. They use the effect of luminescence of biological objects that occurs under the influence of ultraviolet radiation. These microscopes examine the structure of the objects under study, which is actively used in microbiology and immunology.
- Operating microscopes. They can have a fairly complex mechanical device and are used for microsurgical operations.
- Comparison microscopes that allow visual comparison of two drugs;
- Contact microscopes for microscopic studies of the structures of individual sections of biological tissues (for this, the microscope lens is pressed against the object under study;
- Ultraviolet and infrared microscopes designed to study objects in the ultraviolet or infrared part of the light spectrum invisible to the naked eye, and many other microscopes designed for a narrow range of purposes.
But the most common is the classical optical microscope, the basics of work on which this material is devoted.
There are the following main methods of research using light microscopes:
- The method of the light field in the flow of passing light. It is based on the principle of passing a stream of light through a sample, which partially absorbs and scatters the rays falling on it, and thus forming an image obtained in the eyepiece. The most common method used to study colored tissues of plants and animals, thin sections, cuts, etc.
- The method of oblique lighting. The light flow is directed at a large angle to the test sample. It is used to identify the relief of the sample under study and to increase the contrast of the resulting image.
- The method of the light field in reflected light. The subject of the study is illuminated from above, and the image is formed due to the different reflectivity of the object's surface. Allows you to study the surfaces of opaque objects.
- The dark field method. The light rays are directed by the condenser so that they form a hollow cone, in the center of which is the lens. Due to this, some of the rays do not fall into the microscope lens, and the observed object looks like it is illuminated in a dark field. The method is intended for the study of transparent samples that do not absorb light.
- Ultramicroscopy method. Bright rays of light are directed perpendicular to the object table. The wave scattering effect makes it possible to detect very small particles less than half the wavelength in size. It is used for observation, analysis and counting of small objects.
- Phase-contrast method. When passing through the sample, the light wave acquires a phase relief, which is then fixed by a special lens. The image is visible as elements with different brightness. Allows you to study transparent and unpainted samples, the structures of which have different optical densities. For phase-contrast microscopy, special eyepieces and a condenser, or a specialized phase-contrast microscope, are used.
- The polarization method. The analysis of anisotropic materials is carried out in light passed through a special filter, as a result, when passing through the sample, the plane of polarization of the rays changes. Thanks to this, it is possible to analyze and study objects that have the properties of double refraction. It is intended for the formation of images of unpainted anisotropic structures (for example, collagen fibers and myofibrils).
- Interference method. It is based on the interference of light, when each beam is bifurcated, entering the microscope. One of the received rays is directed through the observed object, and the other is directed past it. In the ocular part of the microscope, both beams are connected again by interfering. It is used to study living tissues and cells.
- The fluorescent (luminescent) method. It is used for detecting fluorescent (luminescent) objects. In a fluorescent microscope, light from a powerful source passes through two filters. One filter passes only the light of the wavelength that excites the fluorescence of the sample. Another filter passes light of the wavelength emitted by a fluorescent object. Thus, fluorescent objects absorb light of one wavelength and emit another wavelength. It is widely used in materials science and biomedical research.
Опубликовано на Порталусе 28 сентября 2021 года
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