The term "microscope" has Greek roots. It consists of two words, which in translation means “small” and “look”. The main role of the microscope is to use it when considering very small objects. Moreover, 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, the master of glasses. Another contender for the title of inventor of the microscope is Galileo Galilei. In 1609, these scientists presented a device with a concave and convex lens for public viewing at the Academy dei Linchei.
Over the years, the system for examining microscopic objects has evolved and improved. A huge step in its history was the invention of a simple achromatically regulated two-lens device. The Dutchman Christian Huygens introduced this system in the late 1600s. The eyepieces of this inventor are still in production today. Their only drawback is the insufficient breadth of the field of view. In addition, compared with the device of modern devices, Huygens eyepieces have an inconvenient location for the eyes.
A special contribution to the history of the microscope was made by the manufacturer of such devices, Anton Van Levenguk (1632-1723). It was he who attracted the attention of biologists to this device. Levenguk made small-sized products equipped with one, but very strong lens. It was inconvenient to use such devices, but they did not double image defects, which was present in composite microscopes. The inventors were able to correct this shortcoming only after 150 years. Along with the development of optics, image quality in composite devices has improved.
The improvement of microscopes continues today. So, in 2006, the 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
Currently, there is a wide variety of devices designed to consider small-sized objects. Their grouping is based on various parameters. This may be the purpose of the microscope or the accepted method of lighting, the structure used for the optical scheme, etc.
But, as a rule, the main types of microscopes are classified by the resolution of microparticles, which 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 light type. Their rich selection is available at optics stores. With the help of such devices, the main tasks for the study of an object are solved. All other types of microscopes are specialized. Their use is usually made in laboratory conditions.
Each of the above types of devices has its own subspecies that are used in one or another field. In addition, today it is possible to buy a school microscope (or training), which is an entry-level system. Professional appliances are also offered to consumers.
Application
What is a microscope for? The human eye, being a special optical system of a biological type, has a certain level of resolution. In other words, there is the smallest distance between the observed objects, when they can still be distinguished. For a normal eye, this resolution is within 0.176 mm. But the sizes of most animal and plant cells, microorganisms, crystals, the microstructure of alloys, metals, etc. are much smaller than this value. How to study and observe such objects? Here various types of microscopes come to the rescue of people. For example, devices of the optical type make it possible to distinguish structures in which the distance between the elements is at least 0.20 microns.
How is the microscope arranged?
The device, with the help of which the examination of microscopic objects becomes accessible to the human eye, has two main elements. They are the lens and eyepiece. These parts of the microscope are fixed in a movable tube located on a metal base. It also has an object table.
Modern types of microscopes are usually equipped with a lighting system. This is, in particular, a condenser having an iris diaphragm. Mandatory equipment for magnifying devices are micro- and macroscrews, which are used 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.
The lenses
I would like to start the description of the microscope with a story about one of its main parts, that is, with the lens. They are a complex optical system that increases the size of the subject in the image plane. The design of the lenses includes a whole system of not only single, but also glued in two or three pieces of lenses.
The complexity of such an optical-mechanical design depends on the circle of those tasks that must be solved by a particular device. For example, in the most sophisticated microscope, up to fourteen lenses are provided.
The lens contains the front part and the systems following it. What is the basis for building an image of the desired quality, as well as determining the working condition? 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 possible only in combination with a frontal lens. It is worth saying that the design of the subsequent part affects the length of the tube and the height of the lens of the device.
Eyepieces
These parts of the microscope are an optical system designed to build the necessary microscopic images on the surface of the eye of the observer. The eyepieces contain two groups of lenses. The closest to the researcher’s eye is called the eye, and the furthest is called the field (with its help, the lens builds an image of the object under study).
Lighting system
The microscope provides a complex structure of diaphragms, mirrors and lenses. With its help, uniform illumination of the studied object is ensured. In the very first microscopes, this function was performed by natural light sources. As optical instruments improved, they began to use first flat and then concave mirrors.
With the help of such simple details, rays from the sun or a lamp were sent to the object of study. In modern microscopes, the lighting system is more advanced. It consists of a condenser and a collector.
Subject table
Microscopic preparations that need to be studied are located on a flat surface. This is the subject table. Different types of microscopes can have a given surface designed in such a way that the object of study will rotate horizontally, vertically or at a certain angle in the observer's field of view .
Operating principle
In the first optical device, the lens system provided an inverse image of microobjects. This made it possible to discern the structure of the substance and the smallest details that were to be studied. The operating principle of a light microscope today is similar to the work carried out by a refractory telescope. In this device, light is refracted as it passes through the glass portion.
How are modern light microscopes magnified? After a beam of light rays enters the device, they are converted into a parallel stream. Only then does the light refract in the eyepiece, due to which the image of microscopic objects increases. Further, this information comes in the form necessary for the observer in his visual analyzer.
Subspecies of light microscopes
Modern optical devices classify:
1. The complexity of the research, working and school microscope.
2. By field of application for surgical, biological and technical.
3. By types of microscopy on reflected and transmitted light devices, phase contact, luminescent and polarizing.
4. In the direction of the light flux inverted and straight.
Electron microscopes
Over time, a device designed to examine microscopic objects has become increasingly sophisticated. Such types of microscopes appeared in which a completely different principle of operation, independent of light refraction, was used. In the process of using the latest types of devices involved electrons. Such systems make it possible to see so small individual parts of a substance that light rays simply flow around them.
What is an electronic type microscope for? With its help, the structure of cells is studied at the molecular and subcellular levels. Also, such devices are used to study viruses.
The device of electron microscopes
What is the basis of the latest devices for examining 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 those properties possessed by electric and magnetic fields. Their rotational symmetry is capable of exerting a focusing effect on electron beams. Based on this, we can answer the question: “How is an electron microscope different 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 flows. Moreover, such fields act like a
collecting lens. When increasing or decreasing the current strength, the focal length of the device changes.
As for the circuit diagram, then with an electron microscope it is similar to the circuit of a light device. The only difference is that the optical elements are replaced by electrical elements similar to them.
An increase in an object in electron microscopes occurs due to the process of refraction of a beam of light passing through the object under study. At various angles, the rays fall into the plane of the objective lens, where the first increase in the sample occurs. Further, the electrons pass the path to the intermediate lens. In it, a gradual change in the increase in the size of the object occurs. The final picture of the studied material gives a projection lens. From it, the image enters the fluorescent screen.
Types of electron microscopes
Modern types of magnifying devices include:
1 . TEM, or transmission electron microscope. In this setup, an image of a very thin object with a thickness of up to 0.1 μm is formed during the interaction of an electron beam with the test substance and its subsequent increase in magnetic lenses located in the lens.
2 . SEM, or scanning electron microscope. Such a device makes it possible to obtain an image of the surface of an object with a high resolution of about several nanometers. When using additional methods, such a microscope provides information that helps determine the chemical composition of the surface layers.
3. Tunnel scanning electron microscope, or STM. Using this device, the relief of conductive surfaces with high spatial resolution is measured. In the process of working with STM, a sharp metal needle is brought to the object under study. In this case, a distance of only a few angstroms is maintained. Further, a small potential is supplied to the needle, due to which a tunneling current arises. In this case, the observer receives a three-dimensional image of the investigated object.
Microscopes "Levenguk"
In 2002, a new optical device company appeared in America. The assortment list of its products includes microscopes, telescopes and binoculars. All these devices feature high image quality.
The head office and development department of the company are located in the USA, in the city of Frimond (California). But as for production facilities, they are located in China. Thanks to all this, the company supplies the market with advanced and high-quality products at an affordable price.
Do you need a microscope? Levenhuk will offer the necessary option. The range of optical equipment of the company includes digital and biological devices for increasing the studied object. 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 it is also capable of video recording of ongoing research. Such functionality is equipped with the Levenhuk D2L model.
The company offers biological microscopes of various levels. These are simpler models and new products that are suitable for professionals.