The term "microscope" has Greek roots. It consists of two words, which in translation mean "small" and "look." The main role of the microscope is its use when examining very small objects. At the same time, this device allows you to determine the size and shape, structure and other characteristics of bodies invisible to the naked eye.
History of Creation
There is no exact information about who was the inventor of the microscope in history. According to some sources, it was designed in 1590 by the father and son of Janssen, a master in the manufacture of glasses. Another contender for the title of inventor of the microscope is Galileo Galilei. In 1609, this scientist presented a device with concave and convex lenses for public viewing at the Accademia dei Lincei.
Over the years, the system for viewing microscopic objects has evolved and improved. A huge step in its history was the invention of a simple achromatically adjustable two-lens device. This system was introduced by the Dutchman Christian Huygens in the late 1600s. Eyepieces of this inventorare in production today. Their only drawback is the insufficient breadth of the field of view. In addition, compared to modern devices, Huygens eyepieces have an uncomfortable position for the eyes.
A special contribution to the history of the microscope was made by the manufacturer of such instruments Anton Van Leeuwenhoek (1632-1723). It was he who drew the attention of biologists to this device. Leeuwenhoek made small-sized products equipped with one, but very strong lens. It was inconvenient to use such devices, but they did not double the image defects that were present in compound microscopes. The inventors were able to correct this shortcoming only after 150 years. Along with the development of optics, the image quality in composite devices has improved.
Improvement of microscopes continues today. So, in 2006, German scientists working at the Institute of Biophysical Chemistry, Mariano Bossi and Stefan Hell, developed the latest optical microscope. Due to the ability to observe objects with dimensions of 10 nm and three-dimensional high-quality 3D images, the device was called a nanoscope.
Classification of microscopes
At present, there is a wide variety of instruments designed to examine small objects. Their grouping is based on various parameters. This may be the purpose of the microscope or the method of illumination adopted, the structure used for the optical design, etc.
But, as a rule, the main types of microscopesare classified according to the resolution of microparticles that can be seen using this system. According to this division, microscopes are:
- optical (light);
-electronic;
-X-ray;-scanning probe.
The most widely used microscopes are of the light type. Their wide selection is available in optics stores. With the help of such devices, the main tasks of studying an object are solved. All other types of microscopes are classified as specialized. Their use is usually made in a laboratory.
Each of the above types of devices has its subspecies, which are used in a particular area. In addition, today it is possible to buy a school microscope (or educational), which is an entry-level system. Offered to consumers and professional devices.
Application
What is a microscope for? The human eye, being a special biological type optical system, has a certain level of resolution. In other words, there is the smallest distance between observed objects when they can still be distinguished. For a normal eye, this resolution is within 0.176 mm. But the dimensions of most animal and plant cells, microorganisms, crystals, the microstructure of alloys, metals, etc. are much smaller than this value. How to study and observe such objects? This is where various types of microscopes come to the aid of people. For example, optical type devices make it possible to distinguish structures in which the distancebetween elements is a minimum of 0.20 µm.
How does a microscope work?
The device, which makes it possible for the human eye to examine microscopic objects, has two main elements. They are the lens and the eyepiece. These parts of the microscope are fixed in a movable tube located on a metal base. It also has a subject table.
Modern types of microscopes are usually equipped with a lighting system. This is, in particular, a condenser having an iris diaphragm. A mandatory set of magnifying devices are micro and macro screws, which serve to adjust the sharpness. The design of microscopes also provides for the presence of a system that controls the position of the condenser.
In specialized, more complex microscopes, other additional systems and devices are often used.
Lenses
I would like to start the description of the microscope with a story about one of its main parts, that is, from the lens. They are a complex optical system that increases the size of the object in question in the image plane. The design of the lenses includes a whole system of not only single, but also glued two or three lenses.
The complexity of such an optical-mechanical design depends on the range of tasks that must be solved by one or another device. For example, the most complex microscope has up to fourteen lenses.
Included in the lensare the frontal part and the systems following it. What is the basis for building an image of the desired quality, as well as determining the operating state? This is a front lens or their system. Subsequent parts of the lens are required to provide the required magnification, focal length and image quality. However, the implementation of such functions is only possible in combination with a front lens. It is worth mentioning that the design of the next part affects the length of the tube and the height of the lens of the device.
Eyepieces
These parts of the microscope are an optical system designed to build the necessary microscopic image on the surface of the retina of the observer's eyes. The eyepieces contain two groups of lenses. The closest to the eye of the researcher is called the eye, and the far one is called the field (with its help, the lens builds an image of the object under study).
Lighting system
The microscope has a complex design of diaphragms, mirrors and lenses. With its help, uniform illumination of the object under study is ensured. In the earliest microscopes, this function was performed by natural light sources. As optical devices improved, they began to use first flat and then concave mirrors.
With the help of such simple details, the rays from the sun or the lamp were directed to the object of study. In modern microscopes, the lighting system is more perfect. It consists of a condenser and a collector.
Subject table
Microscopic preparations requiring study,are placed on a flat surface. This is the subject table. Various types of microscopes can have this surface designed in such a way that the object of study will rotate in the field of view of the observer horizontally, vertically or at a certain angle.
Operation principle
In the first optical device, the lens system provided an inverse image of micro-objects. This made it possible to see the structure of matter and the smallest details that were to be studied. The principle of operation of a light microscope today is similar to the work carried out by a refractor telescope. In this device, light is refracted as it passes through the glass part.
How do modern light microscopes magnify? After a beam of light rays enters the device, they are converted into a parallel stream. Only then does the refraction of light in the eyepiece, due to which the image of microscopic objects increases. Further, this information enters in the form necessary for the observer in his visual analyzer.
Subspecies of light microscopes
Modern optical instruments are classified:
1. According to the class of complexity for research, work and school microscope.
2. By field of application for surgical, biological and technical.
3. By types of microscopy for devices of reflected and transmitted light, phase contact, luminescent and polarizing.4. In the direction of the light flux to inverted and direct.
Electron microscopes
Over time, the device designed to examine microscopic objects has become more and more perfect. Such types of microscopes appeared in which a completely different principle of operation, independent of the refraction of light, was used. In the process of using the latest types of devices, electrons were involved. Such systems make it possible to see individual parts of matter so small that light rays simply flow around them.
What is an electron type microscope for? It is used to study the structure of cells at the molecular and subcellular levels. Also, similar devices are used to study viruses.
Design of electron microscopes
What underlies the operation of the latest instruments for viewing microscopic objects? How is an electron microscope different from a light microscope? Are there any similarities between them?
The principle of operation of an electron microscope is based on the properties that electric and magnetic fields have. Their rotational symmetry is able to have a focusing effect on electron beams. Based on this, we can answer the question: “How does an electron microscope differ from a light microscope?” In it, unlike an optical device, there are no lenses. Their role is played by appropriately calculated magnetic and electric fields. They are created by turns of coils through which current passes. In this case, such fields act like a converging lens. When the current increases or decreases, the focal length changes.instrument distance.
As for the circuit diagram, the electron microscope has it similar to the circuit diagram of a light device. The only difference is that the optical elements are replaced by electric ones similar to them.
Magnification of an object in electron microscopes occurs due to the process of refraction of a beam of light passing through the object under study. At different angles, the rays enter the plane of the objective lens, where the first magnification of the sample takes place. Then the electrons pass the way to the intermediate lens. In it there is a smooth change in the increase in the size of the object. The final image of the studied material is given by the projection lens. From it, the image falls on the fluorescent screen.
Types of electron microscopes
Modern types of magnifiers include:
1. TEM, or transmission electron microscope. In this setup, an image of a very thin object, up to 0.1 µm thick, is formed by the interaction of an electron beam with the substance under study and its subsequent magnification by magnetic lenses in the objective.
2. SEM, or scanning electron microscope. Such a device makes it possible to obtain an image of the surface of an object with a high resolution of the order of several nanometers. When using additional methods, such a microscope provides information that helps determine the chemical composition of near-surface layers.3. Tunneling Scanning Electron Microscope, or STM. Using this device, the relief of conductive surfaces with a high spatialpermission. In the process of working with STM, a sharp metal needle is brought to the object under study. At the same time, a distance of only a few angstroms is maintained. Next, a small potential is applied to the needle, due to which a tunnel current arises. In this case, the observer receives a three-dimensional image of the object under study.
Leuwenhoek microscopes
In 2002, a new company producing optical instruments appeared in America. Its product range includes microscopes, telescopes and binoculars. All these devices are distinguished by high image quality.
The head office and development department of the company are located in the USA, in the city of Fremond (California). But as for the production facilities, they are located in China. Thanks to all this, the company delivers advanced and high-quality products to the market at an affordable price.
Do you need a microscope? Levenhuk will suggest the required option. The range of optical equipment of the company includes digital and biological devices for magnifying the object under study. In addition, the buyer is offered and designer models, executed in a variety of colors.
The Levenhuk microscope has extensive functionality. For example, an entry-level training device can be connected to a computer and is also capable of capturing video of ongoing research. Levenhuk D2L model is equipped with this functionality.
The company offers biological microscopes of various levels. These are simpler models, and novelties,suitable for professionals.
