We look at the world through the eyes of a mantis crab: the near-infrared range. About infrared radiation

In various spheres of life, people use infrared rays. The benefits and harms of radiation depend on the wavelength and exposure time.

In everyday life, a person is constantly exposed to infrared radiation (IR radiation). Its natural source is the sun. Artificial ones include electric heating elements and incandescent lamps, any heated or hot bodies. This type of radiation is used in heaters, heating systems, night vision devices, and remote controls. The operating principle of medical equipment for physiotherapy is based on infrared radiation. What are infrared rays? What are the benefits and harms of this type of radiation?

What is IR radiation

IR radiation is electromagnetic radiation, a form of energy that heats objects and is adjacent to the red spectrum of visible light. The human eye does not see in this spectrum, but we feel this energy as heat. In other words, people perceive infrared radiation from heated objects with their skin as a sensation of heat.

Infrared rays are short-wave, medium-wave and long-wave. The wavelengths emitted by a heated object depend on the heating temperature. The higher it is, the shorter the wavelength and the more intense the radiation.

For the first time, the biological effect of this type of radiation was studied using the example of cell cultures, plants, and animals. It was found that under the influence of IR rays the development of microflora is suppressed and metabolic processes are improved due to the activation of blood flow. This radiation has been proven to improve blood circulation and have analgesic and anti-inflammatory effects. It has been noted that under the influence of infrared radiation, patients after surgery can more easily tolerate postoperative pain, and their wounds heal faster. It has been established that IR radiation helps to increase nonspecific immunity, which reduces the effect of pesticides and gamma radiation, and also accelerates the recovery process from influenza. IR rays stimulate the removal of cholesterol, waste, toxins and other harmful substances from the body through sweat and urine.

The benefits of infrared rays

Due to these properties, infrared radiation is widely used in medicine. But the use of broad-spectrum infrared radiation can lead to overheating of the body and redness of the skin. At the same time, long-wave radiation does not have a negative effect, therefore long-wave devices or emitters with selective wavelengths are more common in everyday life and medicine.

Exposure to long-wave infrared rays promotes the following processes in the body:

• Normalization of blood pressure by stimulating blood circulation
• Improving cerebral circulation and memory
• Cleansing the body of toxins, heavy metal salts
• Normalization of hormonal levels
• Stopping the spread of harmful germs and fungi
• Restoring water-salt balance
• Pain relief and anti-inflammatory effect
• Strengthening the immune system.

The therapeutic effects of infrared rays can be used for the following diseases and conditions:

• bronchial asthma and exacerbation of chronic bronchitis
• focal pneumonia in the resolution stage
• chronic gastroduodenitis
• hypermotor dyskinesia of the digestive organs
• chronic acalculous cholecystitis
• spinal osteochondrosis with neurological manifestations
• rheumatoid arthritis in remission
• exacerbation of deforming osteoarthritis of the hip and knee joints
• obliterating atherosclerosis of the vessels of the legs, neuropathy of the peripheral nerves of the legs
• exacerbation of chronic cystitis
• urolithiasis disease
• exacerbation of chronic prostatitis with impaired potency
• infectious, alcoholic, diabetic polyneuropathies of the legs
• chronic adnexitis and ovarian dysfunction
• withdrawal syndrome

Heating using infrared radiation helps strengthen the immune system, suppresses the growth of bacteria in the environment and in the human body, and improves the condition of the skin by increasing blood circulation in it. Air ionization helps prevent allergy exacerbations.

When IR radiation can cause harm

First of all, you need to take into account existing contraindications before using infrared rays for medicinal purposes. Harm from their use may occur in the following cases:

• Acute purulent diseases
• Bleeding
• Acute inflammatory diseases leading to decompensation of organs and systems
• Systemic blood diseases
• Malignant neoplasms

In addition, excessive exposure to broad spectrum infrared rays causes severe redness of the skin and can cause burns. There are known cases of tumors appearing on the face of metallurgical workers as a result of prolonged exposure to this type of radiation. There have also been cases of dermatitis and heat stroke.

Infrared rays, especially in the range of 0.76 - 1.5 microns (short wavelength region), pose a danger to the eyes. Prolonged and prolonged exposure to radiation can lead to the development of cataracts, photophobia and other visual impairments. For this reason, it is not advisable to be exposed to short-wave heaters for a long time. The closer a person is to such a heater, the less time he should spend near this device. It should be noted that this type of heater is intended for outdoor or local heating. Long-wave infrared heaters are used to heat residential and industrial premises intended for long-term stays.

Infrared (IR) radiation is a type of electromagnetic radiation that occupies the spectral range between visible red light (INFRAred: BELOW red) and shortwave radio waves. These rays create heat and are scientifically known as thermal waves. These rays create heat and are scientifically known as thermal waves.

All heated bodies emit infrared radiation, including the human body and the Sun, which in this way warms our planet, giving life to all life on it. The warmth that we feel from a fire near a fire or fireplace, a heater or warm asphalt is all a consequence of infrared rays.

The entire spectrum of infrared radiation is usually divided into three main ranges, differing in wavelength:

• Short wavelength, with wavelength λ = 0.74-2.5 µm;
• Medium wave, with wavelength λ = 2.5-50 µm;
• Long wavelength, with wavelength λ = 50-2000 µm.

Near or short-wave infrared rays are not hot at all; in fact, we don’t even feel them. These waves are used, for example, in TV remote controls, automation systems, security systems, etc. Their frequency is higher, and accordingly their energy is higher than that of far (long) infrared rays. But not at such a level as to harm the body. Heat begins to be created at mid-infrared wavelengths, and we already feel their energy. Infrared radiation is also called “thermal” radiation, because radiation from heated objects is perceived by the human skin as a sensation of heat. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. For example, a source with a wavelength of 1.1 microns corresponds to molten metal, and a source with a wavelength of 3.4 microns corresponds to metal at the end of rolling or forging.

Of interest to us is the spectrum with a wavelength of 5-20 microns, since it is in this range that more than 90% of the radiation produced by infrared heating systems occurs, with a radiation peak of 10 microns. It is very important that it is at this frequency that the human body itself emits infrared waves of 9.4 microns. Thus, any radiation at a given frequency is perceived by the human body as related and has a beneficial and, even moreover, healing effect on it.

With such exposure to infrared radiation on the body, the effect of “resonance absorption” occurs, which is characterized by the body’s active absorption of external energy. As a result, one can observe an increase in a person’s hemoglobin level, an increase in the activity of enzymes and estrogens, and, in general, a stimulation of a person’s vital activity.

The effect of infrared radiation on the surface of the human body, as we have already said, is useful and, on top of that, pleasant. Remember the first sunny days at the beginning of spring, when after a long and cloudy winter the sun finally came out! You feel how it pleasantly envelops the illuminated area of ​​your skin, face, palms. I no longer want to wear gloves and a hat, despite the rather low temperature compared to the “comfortable” one. But as soon as a small cloud appears, we immediately experience noticeable discomfort from the interruption of such a pleasant sensation. This is the very radiation that we so lacked throughout the winter, when the Sun was absent for a long time, and we, willy-nilly, carried out our “infrared post”.

As a result of exposure to infrared radiation, you can observe:

• Acceleration of metabolism in the body;
• Restoration of skin tissue;
• Slowing down the aging process;
• Removing excess fat from the body;
• Release of human motor energy;
• Increasing the body's antimicrobial resistance;
• Activation of plant growth

and many many others. Moreover, infrared irradiation is used in physiotherapy to treat many diseases, including cancer, as it promotes the expansion of capillaries, stimulates blood flow in the vessels, improves immunity and produces a general therapeutic effect.

And this is not at all surprising, because this radiation is given to us by nature as a way of transmitting heat and life to all living things that need this warmth and comfort, bypassing empty space and air as intermediaries.

INTRODUCTION

The imperfection of one's own nature, compensated by the flexibility of the intellect, constantly pushed a person to search. The desire to fly like a bird, swim like a fish, or, say, see at night like a cat, came true as the required knowledge and technology were achieved. Scientific research was often spurred by the needs of military activity, and the results were determined by the existing technological level.

Expanding the range of vision to visualize information inaccessible to the eye is one of the most difficult tasks, as it requires serious scientific training and a significant technical and economic base. The first successful results in this direction were obtained in the 30s of the 20th century. The problem of observation in low light conditions became particularly urgent during the Second World War.

Naturally, the efforts expended in this direction have led to progress in scientific research, medicine, communications technology and other fields.

PHYSICS OF INFRARED RADIATION

Infrared radiation- electromagnetic radiation occupying the spectral region between the red end of visible light (with wavelength (= m) and short-wave radio radiation (= m). Infrared radiation was discovered in 1800 by the English scientist W. Herschel. 123 years after the discovery of infrared radiation, the Soviet physicist A.A. Glagoleva-Arkadyeva obtained radio waves with a wavelength of approximately 80 microns, i.e. located in the infrared wavelength range.This proved that light, infrared rays and radio waves are of the same nature, all of these are just varieties of ordinary electromagnetic waves .

Infrared radiation is also called “thermal” radiation, since all bodies, solid and liquid, heated to a certain temperature emit energy in the infrared spectrum.

SOURCES OF IR RADIATION

MAIN SOURCES OF IR RADIATION OF SOME OBJECTS

Infrared radiation from ballistic missiles and space objects	Infrared radiation from aircraft	Infrared radiation from surface ships
Marching torch engine, which is a stream of burning gases carrying suspended solid particles of ash and soot that are formed during the combustion of rocket fuel. Rocket body. The earth, which reflects part of the sun's rays that fall on it. The Earth itself.	Radiation reflected from the airframe of an aircraft from the Sun, Earth, Moon and other sources. Internal thermal radiation of the extension pipe and nozzle of a turbojet engine or exhaust pipes of piston engines. Own thermal radiation of the exhaust gas jet. Internal thermal radiation from the aircraft skin, resulting from aerodynamic heating during flight at high speeds.	Chimney casing. Exhaust chimney hole

BASIC PROPERTIES OF IR RADIATION

1. Passes through some opaque bodies, also through rain,

haze, snow.

2. Produces a chemical effect on photographic plates.

3. Absorbed by a substance, it heats it.

4. Causes an internal photoelectric effect in germanium.

5. Invisible.

6. Capable of interference and diffraction phenomena.

7. Registered by thermal methods, photoelectric and

photographic.

CHARACTERISTICS OF IR RADIATION

Own Reflected Weakening Physical

thermal objects IR IR radiation features IR

radiation radiation in the atmosphere radiation backgrounds

Characteristics	Basic concepts
Own thermal radiation of heated bodies	The fundamental concept is a completely black body. An absolute black body is a body that absorbs all radiation incident on it at any wavelength. Black body radiation intensity distribution (Planck's s/n): where is the spectral brightness of radiation at temperature T, is the wavelength in microns, C1 and C2 are constant coefficients: C1 = 1.19*W*µm*cm*sr, C2=1.44*µm*deg. Maximum wavelength (Wien's law): , where T is the absolute body temperature. Integral radiation density - Stefan - Boltzmann law:
IR radiation reflected by objects	The maximum solar radiation, which determines the reflected component, corresponds to wavelengths shorter than 0.75 microns, and 98% of the total solar radiation energy falls in the spectral region up to 3 microns. This wavelength is often considered to be the boundary wavelength that separates the reflected (solar) and intrinsic components of IR radiation from objects. Therefore, it can be accepted that in the near part of the IR spectrum (up to 3 μm), the reflected component is decisive and the distribution of radiance over objects depends on the distribution of reflectance and irradiance. For the far part of the IR spectrum, the determining factor is the objects’ own radiation, and the distribution of emissivity over their area depends on the distribution of emissivity coefficients and temperature. In the mid-wave part of the IR spectrum, all four parameters must be taken into account.
Attenuation of IR radiation in the atmosphere	In the IR wavelength range there are several windows of transparency and the dependence of atmospheric transmission on wavelength has a very complex form. The attenuation of IR radiation is determined by the absorption bands of water vapor and gas components, mainly carbon dioxide and ozone, as well as radiation scattering phenomena. See figure “Absorption of IR radiation”.
Physical features of IR background radiation	IR radiation has two components: its own thermal radiation and reflected (scattered) radiation from the Sun and other external sources. In the wavelength range shorter than 3 microns, reflected and scattered solar radiation dominates. In this wavelength range, as a rule, the intrinsic thermal radiation of the backgrounds can be neglected. On the contrary, in the wavelength range greater than 4 μm, the intrinsic thermal radiation of the backgrounds predominates and reflected (scattered) solar radiation can be neglected. The wavelength range of 3-4 microns is, as it were, transitional. In this range there is a pronounced minimum in the brightness of background formations.

ABSORPTION OF IR RADIATION

Transmission spectrum of the atmosphere in the near and mid-infrared region (1.2-40 μm) at sea level (lower curve in the graphs) and at an altitude of 4000 m (upper curve); in the submillimeter range (300-500 microns) radiation does not reach the Earth's surface.

IMPACT ON HUMAN

Since ancient times, people have been well aware of the beneficial power of heat or, in scientific terms, infrared radiation.

In the infrared spectrum there is a region with wavelengths from approximately 7 to 14 microns (the so-called long-wave part of the infrared range), which has a truly unique beneficial effect on the human body. This part of the infrared radiation corresponds to the radiation of the human body itself, with a maximum at a wavelength of about 10 microns. Therefore, our body perceives any external radiation with such wavelengths as “our own”. The most famous natural source of infrared rays on our Earth is the Sun, and the most famous artificial source of long-wave infrared rays in Rus' is the Russian stove, and every person has definitely experienced their beneficial effects. Cooking with infrared waves makes food especially tasty, preserves vitamins and minerals, and has nothing to do with microwave ovens.

By influencing the human body in the long-wave part of the infrared range, it is possible to obtain a phenomenon called “resonance absorption”, in which external energy will be actively absorbed by the body. As a result of this effect, the potential energy of the body cell increases, and unbound water leaves it, the activity of specific cellular structures increases, the level of immunoglobulins increases, the activity of enzymes and estrogens increases, and other biochemical reactions occur. This applies to all types of body cells and blood.

FEATURES OF IMAGES OF OBJECTS IN THE IR RANGE

Infrared images have a distribution of contrasts between known objects that is unusual for the observer due to a different distribution of the optical characteristics of object surfaces in the IR range compared to the visible part of the spectrum. IR radiation makes it possible to detect objects in IR images that are not noticeable in ordinary photographs. It is possible to identify areas of damaged trees and shrubs, as well as reveal evidence of the use of freshly cut vegetation to camouflage objects. The different transmission of tones in images led to the creation of the so-called multi-spectral shooting, in which the same section of the plane of objects is simultaneously photographed in different zones of the spectrum by a multi-spectral camera.

Another feature of IR images, characteristic of heat maps, is that in addition to reflected radiation, their own radiation also participates in their formation, and in some cases only this alone. Intrinsic radiation is determined by the emissivity of the surfaces of objects and their temperature. This makes it possible to identify heated surfaces or areas thereof on heat maps that are completely undetectable in photographs, and to use thermal images as a source of information about the temperature state of an object.

IR images make it possible to obtain information about objects that are no longer present at the time of shooting. For example, on the surface of the site where an aircraft is parked, its thermal portrait is preserved for some time, which can be recorded on an IR image.

The fourth feature of heat maps is the ability to register objects both in the absence of incident radiation and in the absence of temperature changes; only due to differences in the emissivity of their surfaces. This property makes it possible to observe objects in complete darkness and in conditions where temperature differences are leveled out to the point of imperceptibility. Under such conditions, unpainted metal surfaces with low emissivity are especially clearly visible against the background of non-metallic objects that look lighter (“dark”), although their temperatures are the same.

Another feature of heat maps is associated with the dynamism of thermal processes occurring during the day. Due to the natural daily variation of temperatures, all objects on the earth's surface participate in a constantly occurring heat exchange process. Moreover, the temperature of each body depends on the conditions of heat exchange, the physical properties of the environment, the intrinsic properties of a given object (heat capacity, thermal conductivity), etc. Depending on these factors, the temperature ratio of adjacent objects changes during the day, so heat maps obtained at different times even from the same objects, differ from each other.

APPLICATION OF INFRARED RADIATION

In the twenty-first century, the introduction of infrared radiation into our lives began. Now it is used in industry and medicine, in everyday life and agriculture. It is universal and can be used for a wide variety of purposes. Used in forensics, physiotherapy, and in industry for drying painted products, building walls, wood, and fruit. Obtain images of objects in the dark, night vision devices (night binoculars), and fog.

Night vision devices - a history of generations

Zero generation
"Glass of Canvas"	Three- and two-electrode systems
	Photocathode Cuff Focusing electrode
	mid 30s
Philips Technical Center, Holland	Abroad - Zworykin, Farnsword, Morton and von Ardenne; in the USSR - G.A. Grinberg, A.A. Artsimovich
This image intensifier tube consisted of two glasses nested inside each other, on the flat bottoms of which a photocathode and a phosphor were applied. The high voltage voltage applied to these layers created an electrostatic field that provides direct transfer of an electronic image from the photocathode to a screen with a phosphor. A silver-oxygen-cesium photocathode, which had a rather low sensitivity, although operational in the range of up to 1.1 microns, was used as a photosensitive layer in the “Holst glass”. In addition, this photocathode had a high noise level, which required cooling to minus 40 °C to eliminate it.	Advances in electron optics have made it possible to replace direct image transfer by focusing with an electrostatic field. The greatest disadvantage of an image intensifier tube with electrostatic image transfer is the sharp decrease in resolution from the center of the field of view to the edges due to the mismatch of the curvilinear electronic image with the flat photocathode and the screen. To solve this problem, they began to be made spherical, which significantly complicated the design of lenses usually designed for flat surfaces.
First generation
Multistage image intensifier tubes
USSR, M.M. Bootslov by RCA, ITT (USA), Philips (Netherlands)
Based on fiber-optic plates (FOP), which are a package of many LEDs, plano-concave lenses were developed, which were installed instead of the entrance and exit windows. The optical image projected onto the flat surface of the VOP is transmitted without distortion to the concave side, which ensures the pairing of the flat surfaces of the photocathode and screen with a curved electronic field. As a result of the use of the VOP, the resolution became the same throughout the entire field of view as in the center.
Second generation
Secondary emission amplifier		Pseudo-binocular
1- photocathode 3-microchannel plate 4– screen
		In the 70s
US companies		company "Praxitronic" (Germany)
This element is a sieve with regularly spaced channels with a diameter of about 10 microns and a thickness of no more than 1 mm. The number of channels is equal to the number of image elements and is of the order of 10 6 . Both surfaces of the microchannel plate (MCP) are polished and metallized, and a voltage of several hundred volts is applied between them. Getting into the channel, the electron experiences collisions with the wall and knocks out secondary electrons. In a pulling electric field, this process is repeated many times, allowing the gain of NxlO to be obtained 4 times. To obtain MCP channels, optical fiber of different chemical composition is used.		Image intensifier tubes with MCPs of biplanar design were developed, that is, without an electrostatic lens, a kind of technological return to direct image transfer, as in the “Holst glass”. The resulting miniature image intensifier tubes made it possible to develop night vision goggles (NVGs) of a pseudo-binocular system, where the image from one image intensifier tube is split into two eyepieces using a beam splitting prism. The image rotation here is carried out in additional mini-lenses.
Third generation
Image intensifier tube P + and SUPER II +
started in the 70s to the present day
mostly American companies
Long-term scientific development and complex manufacturing technology, which determine the high cost of the third generation image intensifier tube, are compensated by the extremely high sensitivity of the photocathode. The integral sensitivity of some samples reaches 2000 mA/W, the quantum yield (the ratio of the number of emitted electrons to the number of quanta with a wavelength in the region of maximum sensitivity incident on the photocathode) exceeds 30%! The service life of such image intensifier tubes is about 3,000 hours, the cost is from $600 to $900, depending on the design.

MAIN CHARACTERISTICS OF THE EOF

Generations of image intensifiers		Photo cathode type	Integral sensitivity,	Sensitivity on wavelengths 830-850	Gain,	Available range recognition human figures in conditions of natural night light, m
	"Glass of Canvas"			about 1, IR illumination
				only under moonlight or IR illuminator
	Super II+ or II++

Infrared radiation is electromagnetic radiation in the wavelength range from m home. Any body (gaseous, liquid, solid) with a temperature above absolute zero (-273°C) can be considered as a source of infrared (IR) radiation. The human visual analyzer does not perceive rays in the infrared range. Therefore, species-specific unmasking features in this range are obtained using special devices (night vision, thermal imagers) that have worse resolution than the human eye. In general, the unmasking features of an object in the IR range include the following: 1) geometric characteristics of the object’s appearance (shape, dimensions, surface details); 2) surface temperature. Infrared rays are absolutely safe for the human body, unlike X-rays, ultraviolet or microwave rays. There is no area where the natural method of heat transfer would not be useful. After all, everyone knows that man cannot become smarter than nature; we can only imitate it.

BIBLIOGRAPHY

1. Kurbatov L.N. A brief outline of the history of the development of night vision devices based on electronic optical converters and image intensifiers // Issue. Defense Technicians. Ser. 11. - 1994

2. Koshchavtsev N.F., Volkov V.G. Night vision devices // Issue. Defense Technicians. Ser. P. - 1993 - Issue. 3 (138).

3. Lecomte J., Infrared radiation. M.: 2002. 410 p.

4. Menshakov Yu.K., M51 Protection of objects and information from technical reconnaissance means. M.: Russian. State Humanitarian. U-t, 2002. 399 p.

Infrared radiation- electromagnetic radiation, occupying the spectral region between the red end of visible light (with a wavelength λ = 0.74 μm and a frequency of 430 THz) and microwave radio radiation (λ ~ 1-2 mm, frequency 300 GHz).

The entire range of infrared radiation is conventionally divided into three areas:

The long-wavelength edge of this range is sometimes separated into a separate range of electromagnetic waves - terahertz radiation (submillimeter radiation).

Infrared radiation is also called “thermal radiation”, since infrared radiation from heated objects is perceived by the human skin as a sensation of heat. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. The radiation spectrum of an absolute black body at relatively low (up to several thousand Kelvin) temperatures lies mainly in this range. Infrared radiation is emitted by excited atoms or ions.

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Discovery history and general characteristics

Infrared radiation was discovered in 1800 by the English astronomer W. Herschel. While studying the Sun, Herschel was looking for a way to reduce the heating of the instrument with which the observations were made. Using thermometers to determine the effects of different parts of the visible spectrum, Herschel discovered that the “maximum of heat” lies behind the saturated red color and, possibly, “beyond visible refraction.” This study marked the beginning of the study of infrared radiation.

Previously, laboratory sources of infrared radiation were exclusively hot bodies or electrical discharges in gases. Nowadays, modern sources of infrared radiation with adjustable or fixed frequency have been created based on solid-state and molecular gas lasers. To record radiation in the near-infrared region (up to ~1.3 μm), special photographic plates are used. Photoelectric detectors and photoresistors have a wider sensitivity range (up to approximately 25 microns). Radiation in the far infrared region is recorded by bolometers - detectors that are sensitive to heating by infrared radiation.

IR equipment is widely used in both military technology (for example, for missile guidance) and civilian technology (for example, in fiber-optic communication systems). IR spectrometers use either lenses and prisms or diffraction gratings and mirrors as optical elements. To eliminate the absorption of radiation in air, spectrometers for the far-IR region are manufactured in a vacuum version.

Since infrared spectra are associated with rotational and vibrational movements in the molecule, as well as with electronic transitions in atoms and molecules, IR spectroscopy allows one to obtain important information about the structure of atoms and molecules, as well as the band structure of crystals.

Infrared radiation ranges

Objects typically emit infrared radiation across the entire spectrum of wavelengths, but sometimes only a limited region of the spectrum is of interest because sensors typically only collect radiation within a certain bandwidth. Thus, the infrared range is often subdivided into smaller bands.

Conventional division scheme

Most often, division into smaller ranges is done as follows:

Abbreviation	Wavelength	Photon energy	Characteristic
Near-infrared, NIR	0.75-1.4 microns	0.9-1.7 eV	Near-IR, limited on one side by visible light, on the other by water transparency, which deteriorates significantly at 1.45 µm. Widespread infrared LEDs and lasers for fiber and airborne optical communication systems operate in this range. Video cameras and night vision devices based on image intensifier tubes are also sensitive in this range.
Short-wavelength infrared, SWIR	1.4-3 microns	0.4-0.9 eV	The absorption of electromagnetic radiation by water increases significantly at 1450 nm. The range 1530-1560 nm predominates in the long-distance communication region.
Mid-wavelength infrared, MWIR	3-8 microns	150-400 meV	In this range, bodies heated to several hundred degrees Celsius begin to emit. In this range, thermal homing heads of air defense systems and technical thermal imagers are sensitive.
Long-wavelength infrared, LWIR	8-15 microns	80-150 meV	In this range, bodies with temperatures around zero degrees Celsius begin to emit radiation. Thermal imagers for night vision devices are sensitive in this range.
Far-infrared, FIR	15 - 1000 µm	1.2-80 meV

CIE scheme

International Illumination Commission International Commission on Illumination ) recommends dividing infrared radiation into the following three groups:

• IR-A: 700 nm – 1400 nm (0.7 µm – 1.4 µm)
• IR-B: 1400 nm – 3000 nm (1.4 µm – 3 µm)
• IR-C: 3000 nm – 1 mm (3 µm – 1000 µm)

ISO 20473 diagram

Thermal radiation

Thermal radiation or radiation is the transfer of energy from one body to another in the form of electromagnetic waves emitted by bodies due to their internal energy. Thermal radiation mainly falls in the infrared region of the spectrum from 0.74 microns to 1000 microns. A distinctive feature of radiant heat exchange is that it can be carried out between bodies located not only in any medium, but also in a vacuum. An example of thermal radiation is light from an incandescent lamp. The power of thermal radiation of an object that meets the criteria of an absolute black body is described by the Stefan-Boltzmann law. The relationship between the emissive and absorptive abilities of bodies is described by Kirchhoff's radiation law. Thermal radiation is one of the three elementary types of thermal energy transfer (in addition to thermal conductivity and convection). Equilibrium radiation is thermal radiation that is in thermodynamic equilibrium with matter.

Application

Night-vision device

There are several ways to visualize an invisible infrared image:

• Modern semiconductor video cameras are sensitive in the near infrared. To avoid color rendering errors, ordinary household video cameras are equipped with a special filter that cuts off the IR image. Cameras for security systems, as a rule, do not have such a filter. However, in the dark there are no natural sources of near-infrared light, so without artificial illumination (for example, infrared LEDs), such cameras will not show anything.
• Electron-optical converter is a vacuum photoelectronic device that amplifies light in the visible spectrum and near-IR. It has high sensitivity and is capable of producing images in very low light conditions. They are historically the first night vision devices and are still widely used today in cheap night vision devices. Since they work only in near-IR, they, like semiconductor video cameras, require lighting.
• Bolometer - thermal sensor. Bolometers for technical vision systems and night vision devices are sensitive in the wavelength range 3..14 microns (mid-IR), which corresponds to radiation from bodies heated from 500 to −50 degrees Celsius. Thus, bolometric devices do not require external lighting, registering the radiation of the objects themselves and creating a picture of the temperature difference.

Thermography

Infrared thermography, thermal imaging or thermal video is a scientific method of obtaining a thermogram - an image in infrared rays showing a pattern of distribution of temperature fields. Thermographic cameras or thermal imagers detect radiation in the infrared range of the electromagnetic spectrum (approximately 900-14000 nanometers or 0.9-14 µm) and use this radiation to create images that help identify overheated or undercooled areas. Since infrared radiation is emitted by all objects that have a temperature, according to Planck's formula for black-body radiation, thermography allows one to "see" the environment with or without visible light. The amount of radiation emitted by an object increases as its temperature increases, so thermography allows us to see differences in temperature. When we look through a thermal imager, warm objects are visible better than those cooled to ambient temperature; people and warm-blooded animals are more easily visible in the environment, both day and night. As a result, the advancement of thermography use can be attributed to the military and security services.

Infrared homing

Infrared homing head - a homing head that works on the principle of capturing infrared waves emitted by the target being captured. It is an optical-electronic device designed to identify a target against the surrounding background and issue a locking signal to an automatic aiming device (ADU), as well as to measure and issue a line of sight angular velocity signal to the autopilot.

Infrared heater

Data transfer

The spread of infrared LEDs, lasers and photodiodes has made it possible to create a wireless optical method of data transmission based on them. In computer technology, it is usually used to connect computers with peripheral devices (IrDA interface). Unlike the radio channel, the infrared channel is insensitive to electromagnetic interference, and this allows it to be used in industrial environments. The disadvantages of the infrared channel include the need for optical windows on the equipment, correct relative orientation of devices, low transmission speeds (usually does not exceed 5-10 Mbit/s, but when using infrared lasers, significantly higher speeds are possible). In addition, the confidentiality of information transfer is not ensured. Under direct visibility conditions, the infrared channel can provide communication over distances of several kilometers, but it is most convenient for connecting computers located in the same room, where reflections from the walls of the room provide stable and reliable communication. The most natural type of topology here is a “bus” (that is, the transmitted signal is simultaneously received by all subscribers). The infrared channel could not become widespread; it was supplanted by the radio channel.

Thermal radiation is also used to receive warning signals.

Remote control

Infrared diodes and photodiodes are widely used in remote control panels, automation systems, security systems, some mobile phones (infrared port), etc. Infrared rays do not distract human attention due to their invisibility.

Interestingly, the infrared radiation of a household remote control is easily recorded using a digital camera.

Medicine

The most common applications of infrared radiation in medicine are found in various blood flow sensors (PPGs).

Widely used heart rate (HR - Heart Rate) and blood oxygen saturation (Sp02) meters use green (for pulse) and red and infrared (for SpO2) LEDs.

Infrared laser radiation is used in the DLS (Digital Light Scattering) technique to determine heart rate and blood flow characteristics.

Infrared rays are used in physiotherapy.

Effect of long-wave infrared radiation:

• Stimulation and improvement of blood circulation. When exposed to long-wave infrared radiation on the skin, skin receptors are irritated and, due to the reaction of the hypothalamus, the smooth muscles of the blood vessels relax, as a result of which the vessels dilate.
• Improving metabolic processes. When exposed to heat, infrared radiation stimulates activity at the cellular level, improving the processes of neuroregulation and metabolism.

Food Sterilization

Infrared radiation is used to sterilize food products for disinfection.

Food industry

A special feature of the use of IR radiation in the food industry is the possibility of penetration of an electromagnetic wave into capillary-porous products such as grain, cereals, flour, etc. to a depth of up to 7 mm. This value depends on the nature of the surface, structure, material properties and frequency characteristics of the radiation. An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, helping to accelerate biochemical transformations in biological polymers (

Every day a person is exposed to infrared radiation and its natural source is the sun. Incandescent elements and various electric heating devices are classified as unnatural derivatives. This radiation is used in heating systems, infrared lamps, heating devices, TV remote controls, and medical equipment. Therefore, it is always necessary to know the benefits and harms of infrared radiation for humans.

Infrared radiation: what is it?

In 1800, an English physicist discovered infrared heat by splitting sunlight into a spectrum using a prism.. William Herschel applied a thermometer to each color until he noticed an increase in temperature as the color changed from violet to red. Thus, the area of ​​​​sensing heat was opened, but it is not visible to the human eye. Radiation is distinguished by two main parameters: frequency (intensity) and beam length. At the same time, the wavelength is divided into three types: near (from 0.75 to 1.5 microns), medium (from 1.5 to 5.6 microns), far (from 5.6 to 100 microns).

It is long-wave energy that has positive properties, corresponding to the natural radiation of the human body with the longest wavelength of 9.6 microns. Therefore, the body perceives every external influence as “native”. The best example of infrared radiation is the heat of the Sun. Such a beam has the difference that it heats the object, and not the space around it. Infrared radiation is a heat distribution option.

Benefits of infrared radiation

Devices that use long-wave thermal radiation affect the human body in two different ways. The first method has a strengthening property, increasing protective functions and preventing early aging. This type allows you to cope with various diseases, increasing the body’s natural defenses against illnesses. It is a form of treatment that is health-based and is suitable for use at home and in medical settings.

The second type of influence of infrared rays is the direct treatment of diseases and general ailments. Every day a person faces health-related disorders. Therefore, long emitters have therapeutic properties. Many medical institutions in America, Canada, Japan, CIS countries and Europe use such radiation. The waves are able to penetrate deeply into the body, warming up the internal organs and skeletal system. These effects help improve blood circulation and accelerate the flow of fluids in the body.

Increased blood circulation has a beneficial effect on human metabolism, tissues are saturated with oxygen, and the muscular system receives nutrition. Many diseases can be eliminated by regular exposure to radiation that penetrates deep into the human body. This wavelength will relieve such ailments as:

• high or low blood pressure;
• pain in the back;
• overweight, obesity;
• diseases of the cardiovascular system;
• depression, stress;
• disorders of the digestive tract;
• arthritis, rheumatism, neuralgia;
• arthrosis, joint inflammation, seizures;
• malaise, weakness, exhaustion;
• bronchitis, asthma, pneumonia;
• sleep disorder, insomnia;
• muscle and lumbar pain;
• problems with blood supply, blood circulation;
• otorhinolaryngological diseases without purulent deposits;
• skin diseases, burns, cellulite;
• renal failure;
• colds and viral illnesses;
• decreased protective function of the body;
• intoxication;
• acute cystitis and prostatitis;
• cholecystitis without stone formation, gastroduodenitis.

The positive effect of radiation is based on the fact that when the wave hits the skin, it acts on the endings of the nerves and a feeling of warmth occurs. Over 90% of radiation is destroyed by moisture located in the upper layer of the skin; it does not cause anything more than an increase in body temperature. The exposure spectrum, the length of which is 9.6 microns, is absolutely safe for humans.

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Radiation stimulates blood circulation, normalizing blood pressure and metabolic processes. By supplying the brain tissue with oxygen, the risk of dizziness is reduced and memory is improved. An infrared ray can remove heavy metal salts, cholesterol and toxins. During therapy, the patient's immunity increases, hormonal levels are normalized and the water-salt balance is restored. Waves reduce the effect of various toxic chemicals, have anti-inflammatory properties, and suppress the formation of fungi, including mold.

Applications of infrared radiation

Infrared energy is used in various fields, positively affecting humans:

1. Thermography. Using infrared radiation, the temperature of objects located at a distance is determined. Heat waves are mainly used in military and industrial applications. Heated objects with such a device can be seen without lighting.
2. Heating. Infrared rays contribute to an increase in temperature, having a beneficial effect on human health. In addition to being useful infrared saunas, they are used for welding, annealing plastic objects, and curing surfaces in the industrial and medical fields.
3. Tracking. This method of using thermal energy is to passively guide missiles. These flying elements have a mechanism inside them called a “heat seeker.” Cars, planes and other vehicles, as well as people, emit heat to help rockets find the right direction to fly.
4. Meteorology. Radiation helps satellites determine the distance at which clouds are located, determines their temperature and type. Warm clouds are shown in gray, and cold clouds are shown in white. Data is studied without interference both day and night. The Earth's hot plane will be indicated in gray or black.
5. Astronomy. Astronomers are equipped with unique instruments - infrared telescopes, which allow them to observe various objects in the sky. Thanks to them, scientists are able to find protostars before they begin to emit light visible to the human eye. Such a telescope will easily identify cold objects, but planets cannot be seen in the infrared spectrum being viewed due to the muting light from the stars. The device is also used to observe galactic nuclei that are obscured by gas and dust.
6. Art. Reflectograms, which work on the basis of infrared radiation, help specialists in this field examine in more detail the lower layers of an object or an artist’s sketches. This method allows you to compare the drawings of the drawing and its visible part to determine the authenticity of the painting and whether it was restored. Previously, the device was adapted for studying old written documents and making ink.

These are only the basic methods of using thermal energy in science, but new equipment operating on its basis appears every year.

Harm from infrared radiation

Infrared light not only brings a positive effect on the human body, it is worth remembering the harm that it can cause if used incorrectly and be dangerous to others. It is the IR ranges with a short wavelength that negatively affect. The bad effect of infrared radiation on the human body manifests itself in the form of inflammation of the lower layers of the skin, dilated capillaries and blistering.

The use of infrared rays should be immediately abandoned in case of the following diseases and symptoms:

• diseases of the circulatory system, bleeding;
• chronic or acute form of purulent processes;
• pregnancy and lactation;
• malignant tumors;
• pulmonary and heart failure;
• acute inflammation;
• epilepsy;
• With prolonged exposure to infrared radiation, the risk of developing photophobia, cataracts and other eye diseases increases.

Strong exposure to infrared radiation leads to redness of the skin and burns. Workers in the metallurgical industry sometimes develop heat stroke and dermatitis. The shorter the user's distance from the heating element, the less time he should spend near the device. Overheating of brain tissue by one degree and heat stroke is accompanied by symptoms such as nausea, dizziness, tachycardia, and darkening of the eyes. When the temperature rises by two degrees or more, there is a risk of developing meningitis.

If heat stroke occurs under the influence of infrared radiation, you should immediately place the victim in a cool room and remove all clothing that is constricting or restricts movement. Bandages soaked in cold water or ice bags are applied to the chest, neck, groin, forehead, spine and armpits.

If you don't have an ice bag, you can use any fabric or item of clothing for this purpose. Compresses are made only with very cold water, periodically moistening the bandages in it.

If possible, the person is completely wrapped in a cold sheet. Additionally, you can blow a stream of cold air onto the patient using a fan. Drinking plenty of cold water will help alleviate the condition of the victim. In severe cases of exposure, it is necessary to call an ambulance and perform artificial respiration.

How to avoid the harmful effects of IR waves

To protect yourself from the negative effects of heat waves, you must follow some rules:

1. If the work is directly related to high temperature heaters, then The use of protective clothing is required to protect the body and eyes.
2. Domestic heaters with exposed heating elements are used with extreme caution. You should not be close to them and it is better to reduce the time of their influence to a minimum.
3. The premises should contain devices that have the least impact on people and their health.
4. Don't stay in the sun for long periods of time. If this cannot be changed, then you need to constantly wear a hat and clothing that covers open areas of the body. This especially applies to children, who cannot always detect an increase in body temperature.

By following these rules, a person will be able to protect himself from the unpleasant consequences of excessive thermal influence. Infrared rays can cause both harm and benefit when used in certain ways.

Treatment methods

Infrared therapy is divided into two types: local and general. In the first type, there is a local effect on a particular area, and in general treatment, the waves treat the entire human body. The procedure is carried out twice a day for 15-30 minutes. The course of treatment ranges from 5 to 20 sessions. It is imperative to wear protective equipment when irradiating. Cardboard covers or special glasses are used for the eyes. After the procedure, redness with blurred boundaries appears on the skin, which disappears after an hour after exposure to the rays. Infrared radiation is highly valued in medicine.

High radiation intensity can cause harm to health, so you must follow all contraindications.

Thermal energy accompanies a person every day in everyday life. Infrared radiation brings not only benefits, but also harm. Therefore, it is necessary to treat infrared light with caution. Devices that emit these waves must be used safely. Many people do not know whether thermal exposure is harmful, but with the correct use of devices, it is possible to improve a person’s health and get rid of certain diseases.