At all times, infrared radiation has surrounded man. Before the advent of technological progress, the rays of the sun had an impact on the human body, and with the advent of household appliances, infrared radiation also has an effect at home. Therapeutic heating of body tissues is successfully used in medicine for the physiotherapeutic treatment of various pathologies.

The properties of infrared radiation have long been studied by physicists and are aimed at obtaining maximum benefits and benefits for humans. All parameters of harmful effects were taken into account and methods of protection were recommended to preserve human health.

Infrared rays: what are they?

Invisible electromagnetic radiation that provides a strong thermal effect is called infrared. The rays range in length from 0.74 to 2000 µm, which is between microwave radio emission and visible red rays, which are the longest in the sun's spectrum.

Back in 1800, British astronomer William Herschel discovered electromagnetic radiation. This happened while studying the rays of the sun: the scientist noticed a significant heating of the instruments and was able to differentiate invisible radiation.

Infrared radiation has a second name - “thermal”. Heat emanates from objects that can maintain temperature. Short infrared waves heat more strongly, and if the heat is felt weak, it means that long-range waves are emanating from the surface. There are three types of wavelengths of infrared radiation:

• short or short up to 2.5 microns;
• average no more than 50 microns;
• long or distant 50–2000 µm.

Any body that has been previously heated emits infrared rays, releasing thermal energy. The most famous natural source of heat is the sun, and artificial ones include electric lamps, household appliances, and radiators, the operation of which generates heat.

Where is infrared radiation used?

Each new discovery finds its application, with the greatest benefit for humanity. The discovery of infrared rays helped solve many problems in various fields from medicine to industrial scale.

The most famous areas where the properties of invisible rays are used:

1. With the help of special devices, thermal imagers, you can detect an object at a remote distance using the properties of infrared radiation. Any object capable of maintaining temperature on its surface, thereby emitting infrared rays. A thermographic camera detects heat rays and creates an accurate image of the object being detected. This property can be used in industry and military practice.
2. To carry out the tracking procedure in military practice, devices with sensors that can detect a target that emits heat are used. In addition, what exactly is in the immediate environment is transmitted in order to correctly calculate not only the trajectory, but also the force of the impact, most often a missile.
3. Active heat transfer together with rays is used in domestic conditions, using beneficial properties for heating a room in the cold season. Radiators are made of metal, which is capable of transmitting the greatest amount of thermal energy. The same effect applies to heaters. Some household appliances: televisions, vacuum cleaners, stoves, irons have the same properties.
4. In industry, the process of welding plastic products and annealing is carried out using infrared radiation.
5. Infrared irradiation is used in medical practice to treat certain pathologies with heat, as well as to disinfect indoor air using quartz lamps.
6. Compiling weather maps is impossible without special instruments with thermal detection sensors that easily determine the movement of warm and cold air.
7. For astronomical research, special telescopes are made that are sensitive to infrared rays, which are capable of detecting space objects with different temperatures on the surface.
8. In the food industry for heat treatment of cereals.
9. To check banknotes, devices with infrared radiation are used, by the light of which counterfeit banknotes can be recognized.

The effect of infrared radiation on the human body is ambiguous. Different wavelengths can trigger unpredictable reactions. You need to be especially careful about the heat of the sun, which can cause harm and become a provoking factor for the launch of negative pathological processes in cells.

Long-wavelength rays hit the skin and activate heat receptors, imparting pleasant warmth to them. It is this frequency range that is actively used for therapeutic effects in medicine. Most of the heat is absorbed by the skin, falling on its surface. Low impact guarantees pleasant heating of the skin surface without affecting the internal organs.

Waves with a wavelength of 9.6 microns promote renewal of the epidermis, strengthen the immune system, and heal the body. Physiotherapy is based on the use of long infrared waves, triggering the following processes:

• blood circulation improves when smooth muscles relax after transmitting information to the hypothalamus when affecting the surface layer of the skin;
• blood pressure normalizes after vasodilation;
• the body's cells are more supplied with nutrients and oxygen, which improves the general condition;
• biochemical reactions proceed faster, which affects the metabolic process;
• immunity improves and the body's resistance to pathogenic microorganisms increases;
• accelerating metabolism helps remove toxic substances and reduce slagging.

Pathological influence

Waves with a short wavelength have the opposite effect. The harm of infrared radiation is due to the intense thermal effect caused by short rays. A strong thermal effect spreads deep into the body, causing heating of the internal organs. Overheating of tissues leads to dehydration and a significant increase in body temperature.

The skin at the site of contact with short-length infrared rays turns red and receives a thermal burn, sometimes of the second degree of severity with the appearance of blisters with cloudy contents. The capillaries at the site of the lesion expand and burst, leading to small hemorrhages.

Cells lose moisture, the body becomes weakened and susceptible to infections of various types. If infrared radiation enters the eyes, this fact has a destructive effect on vision. The mucous membrane of the eye becomes dry, the retina is negatively affected. The lens loses its elasticity and transparency, which is one of the symptoms of cataracts.

Excessive heat exposure causes an increase in inflammatory processes, if any, and also serves as a fertile ground for the occurrence of inflammation. Doctors say that exceeding the temperature by a couple of degrees can provoke infection with meningitis.

A general increase in body temperature leads to heat stroke, which, if help is not provided, can lead to irreversible consequences. Main signs of heat stroke:

• general weakness;
• Strong headache;
• blurred vision;
• nausea;
• increased heart rate;
• the appearance of cold sweat on the back;
• short-term loss of consciousness.

A serious complication associated with impaired thermoregulation occurs if the frequency of exposure to infrared radiation continues for a long time. If a person is not provided with timely assistance, brain cells are modified, and the activity of the circulatory system is inhibited.

List of activities in the first minutes after the onset of alarming symptoms:

1. Remove the source of infrared radiation from the victim: move the person to the shade or to a place away from the source of harmful heat.
2. Unbutton or remove any clothing that may interfere with deep, free breathing.
3. Open the window to allow fresh air to flow freely.
4. Wipe with cool water or wrap in a wet sheet.
5. Apply cold to the places where large arteries are located (temporal, groin, forehead, armpits).
6. If the person is conscious, he should be given cool, clean water to drink; this measure will lower the body temperature.
7. In case of loss of consciousness, a resuscitation complex should be performed, consisting of artificial respiration and chest compressions.
8. Call an ambulance to receive qualified medical care.

Indications

For therapeutic purposes, the use of long thermal waves is widely used in medical practice. The list of diseases is quite long:

• high blood pressure;
• pain syndrome;
• will help you lose extra pounds;
• diseases of the stomach and duodenum;
• depressive states;
• respiratory diseases;
• skin pathologies;
• rhinitis, uncomplicated otitis.

Contraindications to the use of infrared radiation

The benefits of infrared radiation are valuable for humans in the absence of pathologies or individual symptoms in which exposure to infrared rays is unacceptable:

• systemic blood diseases, tendency to frequent bleeding;
• acute and chronic inflammatory diseases;
• the presence of purulent infection in the body;
• malignant neoplasms;
• heart failure in the stage of decompensation;
• pregnancy;
• epilepsy and other severe neurological disorders;
• children up to three years of age.

Protective measures against harmful rays

Those at risk of receiving short-wave infrared radiation include those who like to spend long periods of time under the scorching sun and workers in workshops where the properties of heat rays are used. To protect yourself, you need to follow simple recommendations:

1. Those who like a beautiful tan should reduce their time in the sun and lubricate exposed skin with a protective cream before going outside.
2. If there is a source of intense heat nearby, reduce the heat intensity.
3. When working in workshops with high temperatures, workers must be equipped with personal protective equipment: special clothing, hats.
4. The time spent in rooms with high temperatures must be strictly regulated.
5. When carrying out procedures, wear protective glasses to maintain eye health.
6. Install only high-quality household appliances in the rooms.

Various types of radiation surround a person outdoors and indoors. Being aware of possible negative consequences will help you stay healthy in the future. The value of infrared radiation is undeniable for improving human life, but there is also a pathological effect that needs to be eliminated by following simple recommendations.

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:

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.

Infrared vision

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 (

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 shortwave radio emission ( =
m).Infrared radiation was discovered in 1800 by the English scientist W. Herschel. 123 years after the discovery of infrared radiation, Soviet physicist A.A. Glagoleva-Arkadyeva received 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 just variations 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

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

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.

INFRARED RADIATION (IR radiation, IR rays), electromagnetic radiation with wavelengths λ from about 0.74 μm to about 1-2 mm, that is, radiation occupying the spectral region between the red end of visible radiation and short-wave (submillimeter) radio emission. Infrared radiation belongs to optical radiation, but unlike visible radiation, it is not perceived by the human eye. Interacting with the surface of bodies, it heats them, which is why it is often called thermal radiation. Conventionally, the region of infrared radiation is divided into near (λ = 0.74-2.5 µm), medium (2.5-50 µm) and far (50-2000 µm). Infrared radiation was discovered by W. Herschel (1800) and independently by W. Wollaston (1802).

Infrared spectra can be lined (atomic spectra), continuous (condensed matter spectra), or striped (molecular spectra). The optical properties (transmittance, reflection, refraction, etc.) of substances in infrared radiation, as a rule, differ significantly from the corresponding properties in visible or ultraviolet radiation. Many substances that are transparent to visible light are opaque to infrared radiation of certain wavelengths, and vice versa. Thus, a layer of water several centimeters thick is opaque to infrared radiation with λ > 1 μm, so water is often used as a heat-protective filter. Plates made of Ge and Si, opaque to visible radiation, are transparent to infrared radiation of certain wavelengths, black paper is transparent in the far infrared region (such substances are used as light filters for isolating infrared radiation).

The reflectivity of most metals in infrared radiation is much higher than in visible radiation, and increases with increasing wavelength (see Metal optics). Thus, the reflection of infrared radiation from Al, Au, Ag, Cu surfaces with λ = 10 μm reaches 98%. Liquid and solid non-metallic substances have selective (wavelength-dependent) reflection of infrared radiation, the position of the maxima of which depends on their chemical composition.

Passing through the earth's atmosphere, infrared radiation is attenuated due to scattering and absorption by atoms and molecules of the air. Nitrogen and oxygen do not absorb infrared radiation and attenuate it only as a result of scattering, which is much less for infrared radiation than for visible light. Molecules H 2 O, O 2, O 3 and others present in the atmosphere selectively (selectively) absorb infrared radiation, and they absorb the infrared radiation of water vapor especially strongly. H 2 O absorption bands are observed in the entire IR region of the spectrum, and CO 2 bands are observed in its middle part. In the surface layers of the atmosphere there are only a small number of “transparency windows” for infrared radiation. The presence of smoke particles, dust, and small drops of water in the atmosphere leads to an additional attenuation of infrared radiation as a result of its scattering by these particles. With small particle sizes, infrared radiation is scattered less than visible radiation, which is used in IR photography.

Sources of infrared radiation. A powerful natural source of infrared radiation is the Sun, about 50% of its radiation lies in the IR region. Infrared radiation accounts for 70 to 80% of the radiation energy of incandescent lamps; it is emitted by an electric arc and various gas-discharge lamps, all types of electric space heaters. In scientific research, sources of infrared radiation are tungsten strip lamps, Nernst pin, globar, high-pressure mercury lamps, etc. The radiation of some types of lasers also lies in the IR region of the spectrum (for example, the wavelength of neodymium glass lasers is 1.06 μm, helium-neon lasers - 1.15 and 3.39 microns, CO 2 lasers - 10.6 microns).

Infrared radiation receivers are based on converting radiation energy into other types of energy that can be measured. In thermal receivers, absorbed infrared radiation causes an increase in the temperature of the thermosensitive element, which is recorded. In photoelectric receivers, the absorption of infrared radiation leads to the appearance or change of electric current or voltage. Photoelectric detectors (unlike thermal ones) are selective, that is, they are sensitive only to radiation from a certain region of the spectrum. Photographic recording of infrared radiation is carried out using special photographic emulsions, but they are sensitive to it only for wavelengths up to 1.2 microns.

Application of infrared radiation. IR radiation is widely used in scientific research and to solve various practical problems. The emission and absorption spectra of molecules and solids lie in the IR region; they are studied in infrared spectroscopy, in structural problems, and are also used in qualitative and quantitative spectral analysis. In the far IR region lies the radiation that arises during transitions between Zeeman sublevels of atoms; the IR spectra of atoms make it possible to study the structure of their electronic shells. Photographs of the same object taken in the visible and infrared ranges may differ significantly due to differences in reflection, transmission and scattering coefficients; In IR photography you can see details that are invisible in regular photography.

In industry, infrared radiation is used for drying and heating materials and products, and in everyday life - for heating rooms. Based on photocathodes sensitive to infrared radiation, electron-optical converters have been created in which an IR image of an object, invisible to the eye, is converted into a visible one. Based on such converters, various night vision devices (binoculars, sights, etc.) are built, allowing them to detect objects in complete darkness, conduct observation and aim, irradiating them with infrared radiation from special sources. With the help of highly sensitive infrared radiation receivers, they carry out thermal direction finding of objects using their own infrared radiation and create homing systems for the target of projectiles and missiles. IR locators and IR rangefinders allow you to detect objects in the dark whose temperature is higher than the ambient temperature and measure distances to them. The powerful radiation of IR lasers is used in scientific research, as well as for ground and space communications, for laser sounding of the atmosphere, etc. Infrared radiation is used to reproduce the meter standard.

Lit.: Schreiber G. Infrared rays in electronics. M., 2003; Tarasov V.V., Yakushenkov Yu.G. Infrared systems of the “looking” type. M., 2004.