Types of microscopes: description, main characteristics, purpose. How does an electron microscope differ from a light microscope?

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 to use it when considering very small objects. In this case, this device allows you to determine the size and shape, structure and other characteristics of bodies invisible to the naked eye.

History of creation

Precise information about who was the inventor of the microscope, in history there. According to some sources, in 1590 his father and son Janssen, the master of spectacles, designed the spectacles. Another contender for the title of inventor of the microscope is Galileo Galilei. In 1609, these scientists were presented with a device with a concave and convex lenses for a review of the public at the Academy dei Lincei.

Over the years, the system for viewing microscopic objects developed and improved. A huge step in its history was the invention of a simple achromatically regulated two-lens device. This system was introduced by the Dutch Christian Huygens in the late 1600s. Eyepieces of this inventor are still in production today. Their only drawback is the insufficient width of the field of view. In addition, in comparison with the device of modern devices, eyewear Huygens have an uncomfortable location for the eyes.

A special contribution to the history of the microscope was made by the manufacturer of such devices Anton Van Leuvengook (1632-1723). It was he who drew the attention of biologists to this device. Levenguk made small-sized products equipped with one, but very strong lens. It was uncomfortable to use such devices, but they did not duplicate image defects that were present in composite microscopes. To correct this lack of inventors could only 150 years later. Along with the development of optics, the image quality in composite devices has improved.

The improvement of microscopes continues in our days. So, in 2006, German scientists working in the Institute of Biophysical Chemistry, Mariano Bossi and Stefan Hellem, developed the newest optical microscope. Because of the ability to observe objects with sizes of 10 nm and three-dimensional high-quality 3D images, the device was called an nanoscope.

Classification of microscopes

Currently, there is a wide variety of instruments designed to deal with small objects. They are grouped based on various parameters. This may be the appointment of a microscope or the adopted method of illumination, the structure used for the optical scheme, and so on.

But, as a rule, the main types of microscopes are classified according to the resolution of microparticles, which can be seen with the help of this system. According to this division, microscopes can be:
- optical (light);
- electronic;
- X-ray;
- Scanning probes.

The most widely used microscopes of light type. Their rich choice is available in optics stores. With the help of such devices, the main tasks of researching an object are solved. All other types of microscopes are classified as specialized. Their use is made, as a rule, in the laboratory.

Each of the above types of instruments has its own subspecies, which are used in this or that sphere. In addition, today there is the opportunity to buy a school microscope (or educational), which is an entry-level system. Produced consumer and professional devices.

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 dimensions of most animals and plant cells, microorganisms, crystals, microstructure of alloys, metals, etc., are much smaller than this size. How to study and observe similar objects? Here, various kinds of microscopes come to help people. For example, optical-type instruments make it possible to distinguish between structures in which the distance between elements is at least 0.20 μm.

How is the microscope arranged?

The instrument, with which the consideration of microscopic objects becomes accessible to the human eye, has two main elements. They are the lens and the eyepiece. The data of a part of the microscope in a movable tube located on a metal base are fixed. On it there is also a subject table.

Modern types of microscopes, as a rule, are equipped with a lighting system. This is, in particular, a condenser having an iris diaphragm. Mandatory bundling of magnifying devices are micro- and macro-screws, which serve to adjust the sharpness. The design of microscopes 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 describing the microscope with a story about one of its main parts, that is, from the lens. They are a complex optical system, increasing the size of the subject in the image plane. The design of lenses includes a whole system of not only single, but also glued two or three pieces of lenses.

The complexity of such an optomechanical design depends on the range of tasks that must be solved by one or another instrument. For example, in the most complicated microscope, up to fourteen lenses are provided.

The lens consists of the front part and the systems following it. What is the basis for building the image of the desired quality, as well as determining the working state? This is a frontal lens or their system. Subsequent parts of the lens are necessary to provide the required magnification, focal length and image quality. However, the implementation of such functions is possible only in combination with the front lens. It should also be said that the design of the following part affects the length of the tube and the height of the instrument's lens.

Eyepieces

These parts of the microscope represent an optical system designed to construct the necessary microscopic image on the retina's surface of the observer's eyes. In the eyepieces there are two groups of lenses. The nearest to the eye of the researcher is called the eye, and the distant one is the field (with its help the lens builds the image of the object under study).

Lighting system

The microscope provides for a complex construction of diaphragms, mirrors and lenses. With its help, uniform illumination of the investigated object is provided. In the very first microscopes, this function was performed by natural light sources. With the improvement of optical instruments, they first began to use 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 investigation. In modern microscopes, the lighting system is more perfect. It consists of a condenser and a collector.

Subject table

Microscopic drugs that need to be studied are located on a flat surface. This is the subject table. Different kinds of microscopes can have a given surface designed in such a way that the object of research will be rotated in the field of view of the observer horizontally, vertically or at a certain angle.

Operating principle

In the first optical device, the lens system produced a reverse image of microobjects. This made it possible to discern 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 that of a refracting telescope. In this device the light is refracted at the moment of passage through the glass part.

How do modern light microscopes increase? After the beam of light rays hits the device, they are converted into a parallel stream. Only then there is a refraction of light in the eyepiece, due to which the image of microscopic objects increases. Further this information arrives in the form necessary for the observer in its visual analyzer.

Subspecies of light microscopes

Modern optical instruments are classified as:

1. In the class of complexity for a research, work and school microscope.
2. On the field of application for surgical, biological and technical.
3. By types of microscopy on devices reflected and transmitted light, phase contact, luminescent and polarizing.
4. Direction of the light flux to inverted and straight.

Electron microscopes

Over time, the device intended for the examination of microscopic objects became more and more perfect. There appeared such types of microscopes, in which a completely different principle of work, independent of the refraction of light, was used. In the process of using the newest types of devices, electrons were used. Such systems allow one to see so small individual parts of a substance that they are simply flowed by light rays.

Why do you need an electron microscope? With its help, the structure of cells at the molecular and subcellular levels is studied. Also, similar devices are used to study viruses.

Electron microscope device

What is the basis for the work of the newest devices for the examination of microscopic objects? How does an electron microscope differ from a light microscope? Are there any similarities between them?

The principle of operation of an electron microscope is based on those properties that electric and magnetic fields possess. Their rotational symmetry can have a focusing effect on electron beams. Proceeding from this, it is possible to answer the question: "What is the difference between an electron microscope and 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. In this case, such fields act like a collecting lens. As the current increases or decreases, the focal length of the device changes.

As for the circuit diagram, in the electron microscope it is similar to that of a light device. The only difference lies in the fact that the optical elements are replaced by similar electrical ones.

The magnification of an object in electron microscopes is due to the refraction process of a light beam passing through the object under study. At different angles, the rays fall into the plane of the objective lens, where the first increase in the sample takes place. Then the electrons pass the path to the intermediate lens. It gradually changes the size of the object. The final picture of the test material is provided by the projection lens. From it the image gets on 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, up to 0.1 μm thick, is formed by the interaction of an electron beam with the substance under study and subsequent magnification of the 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, which is on the order of several nanometers. 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. With the help of this instrument, the relief of conductive surfaces with high spatial resolution is measured. In the process of working with the STM, a sharp metal needle is led to the object under study. At the same time the distance is maintained only a few angstroms. Further on, a small potential is applied to the needle, due to which a tunnel current arises. The observer receives a three-dimensional image of the object under study.

Microscope "Levenguk"

In 2002, America introduced a new company that produces optical instruments. In the assortment list of its products are microscopes, telescopes and binoculars. All these devices are distinguished by high image quality.

The company's head office and development department are located in the US, in the city of Frimonde (California). But as far as production facilities are concerned, they are located in China. Thanks to all this, the company delivers to the market advanced and high-quality products at an affordable price.

Do you need a microscope? Levenhuk will propose the necessary option. In the range of optical technology of the company there are digital and biological instruments for increasing the studied object. In addition, the buyer is offered and design models, executed in a variety of colors.

The Levenhuk microscope has extensive functionality. For example, an entry-level educational device can be attached to a computer, and it is also able to record video of ongoing research. Such functionality is equipped with the model Levenhuk D2L.

The company offers biological microscopes of various levels. This is a simpler model, and new products that will suit professionals.