What determines the resolution of the microscope
The resolution of a microscope is the ability
This characteristic is determined primarilythe wavelength of radiation used in microscopy (visible, ultraviolet, X-ray radiation). The fundamental limitation is the impossibility of obtaining an image of an object with the help of electromagnetic radiation, which is smaller in size than the wavelength of this radiation.
"To penetrate deeper" into the microworld is possible when using radiation with shorter wavelengths.
How does a microscope work?
The optical system is designed forspatial transformation of the radiation field before the optical system (in the "space of objects") in the field after the optical system (in the "image space"). This division of "spaces" is very arbitrary, since these "space" fields, different from the point of view of changes in the structure of the field, may in some cases (for example, when using mirrors) coincide in three-dimensional physical space.
This organization is achieved bythe use of shaped optical elements, the action of which is manifested in the phenomenon of refraction, reflection and scattering of radiation. The physical cause of all these phenomena is interference.
In many cases, to explain the actionof an optical element, it is quite enough to use the concepts of the essence of these phenomena, without disclosing the role of interference, which makes it possible to describe the radiation field by a formalized geometric model based on an intuitive concept of a "ray of light" and the postulate of infinitely small radiation wavelength and optical homogeneity of the medium filling all space in which the laws of geometric optics operate.
But in the case when it turns out to be necessaryto take into account the wave properties of radiation and take into account the comparability of the dimensions of the optical element with the radiation wavelength, geometric optics begins to give errors, which is called diffraction, which is essentially not an independent phenomenon, but only the same interference.
What are microscopes
- Optical microscopes
The human eye is a naturalan optical system characterized by a certain resolution, that is, the smallest distance between the elements of the observed object (perceived as points or lines) at which they can still be different from one another.
For a normal eye, when moving away from an object byt. n. best vision distance (D = 250mm), average normal resolution is ~ 0.2mm. The sizes of microorganisms, most plant and animal cells, small crystals, details of the microstructure of metals and alloys, etc. are much less than this value.
Until the middle of the 20th century, they worked only with visibleoptical radiation, in the range of 400-700 nm, as well as with near ultraviolet (fluorescent microscope). Optical microscopes could not provide a resolution of less than a half-wavelength of the reference radiation (wavelength range 0.2-0.7 microns, or 200-700 nm).
Thus, the optical microscope is able to distinguish structures with a distance between points up to ~ 0.20 μm, so the maximum magnification that could be achieved was ~ 2000 times.
- Electron microscopes
A beam of electrons, which have the properties of not only a particle, but also a wave, can be used in microscopy.
The wavelength of an electron depends on its energy, andthe electron energy is equal to E = Ve, where V is the potential difference passed by the electron, e is the electron charge. The wavelengths of electrons passing through a potential difference of 200,000 V are of the order of 0.1 nm.
Electrons can be easily focused with electromagnetic lenses, since an electron is a charged particle. An electronic image can be easily converted into a visible one.
The resolution of an electron microscope is 1000–10000 times higher than that of a traditional light microscope, and for the best modern instruments it can be less than one angstrom.
- Scanning Probe Microscopes
A class of microscopes based on surface scanning with a probe.
Scanning probe microscopes (SPM) are a relatively new class of microscopes. An SPM image is obtained by registering interactions between the probe and the surface.
At this stage of development, it is possible to registerinteraction of the probe with individual atoms and molecules, due to which SPMs are comparable in resolving power to electron microscopes, and surpass them in some parameters.
- X-ray microscopes
X-ray microscope - device for examining very smallobjects whose dimensions are comparable to the length of the X-ray wave. Based on the use of electromagnetic radiation with a wavelength of 0.01 to 1 nanometer.
Resolution X-ray microscopesabilities are between electron and optical microscopes. The theoretical resolution of an X-ray microscope reaches 2-20 nanometers, which is an order of magnitude higher than the resolution of an optical microscope (up to 150 nanometers). Currently, there are X-ray microscopes with a resolution of about 5 nanometers.
- Infrared microscopy
It is a research method by observing samples through a microscope in infrared light. The method is designed to study samples of very small size (on the order of micrometers).
The visible light observed by the experimenter, andthe infrared light recorded by the detector passes through one common optical system, therefore the image in the binocular corresponds to the area that is analyzed in infrared radiation.
IR microscopy is used to analyze samples in very small quantities (0.01 to 100 µg) or small sizes (10–1 to 10–3 mm), as well as concentration fluctuations and inclusions.
What are the disadvantages of the invented microscopes?
Light microscopes performancelimited by the level of random noise created by elementary particles of light - quanta of electromagnetic radiation, or photons. Discreteness of photons determines the sensitivity, resolution and speed of optical devices.
To optimize these parameters, the developersusually follow the path of increasing the intensity of light and replacing its conventional sources with laser ones. But the use of laser microscopes is not always possible when studying biological systems, since bright lasers can destroy a living cell.
How has science advanced in the development of microscopes?
The last major discovery in this area was made in early June 2021. Scientists from Australia and Germany have created a quantum microscope that can see previously invisible cellular structures.
According to the authors, this paves the way for the creation of new biotechnologies and practical applications - from navigation to medical imaging. The research results are published in the journal Nature.
Researchers at the University of Queensland have suggested that biological imaging can be improved without increasing light intensity using quantum photon correlations.
Together with German colleagues from RostockAt the university, they experimentally proved that using quantum correlations, it is possible to obtain a signal-to-noise ratio 35 percent higher than with conventional microscopy without photodamage. Much higher with this technology and the speed of image processing.
How does a quantum microscope work?
The creators of the quantum microscope have madeinstallation, which is a coherent Raman microscope with subwavelength resolution and bright quantum-correlated illumination, which makes it possible to visualize molecular bonds inside the cell.
The microscope is based on the science of quantumentanglement, an effect that Einstein described as "eerie interactions at a distance." It is the world's first entanglement sensor with performance that surpasses the best available technology. Its creation will lead to the emergence of various types of new technologies - from the latest navigation systems to more advanced vehicles. Quantum entanglement in our microscope provides 35 percent improved clarity without destroying the cell, allowing you to see the smallest biological structures that would otherwise be invisible.
Warwick Bowen, Professor of the Laboratory of Quantum Optics and the Center of Excellence for Engineering Quantum Systems, Australian Research Council
The authors believe that the main success of the new method is overcoming the so-called victory over the principles of traditional light microscopy, which is unable to penetrate into a living cell.
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