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Infrared radiation
At the heart of the electromagnetic spectrum is infrared radiation, often described as “invisible heat.” This radiation lies right near visible light on the spectrum, characterized by wavelengths longer than those of red light. Although our eyes can't pick it up, infrared radiation is everywhere around us, emitted by objects and living things, carrying crucial information that we can exploit.
But why is infrared radiation so important? How does infrared radiation, although beyond the reach of our visual perception, prove to be a key to how we explore and interact with the world around us? How does its position within the electromagnetic spectrum give us a unique perspective on objects and phenomena that otherwise remain hidden? Through this article, we delve into the nuances of infrared radiation, exploring its broad applications and its crucial role in our constant quest for understanding and innovation.
(Electromagnetic spectrum)
Thermal radiation is the process by which an object emits energy in the form of electromagnetic rays due to its temperature. Unlike conduction and convection, which involve the transfer of heat through direct contact or fluid movement, thermal radiation can propagate in a vacuum because it does not require a material medium to propagate. They are generally divided into three categories based on their wavelengths, and these categories are often called near, mid, and far infrared.
(Infrared radiation in comparison with other types of radiation)
- Near infrared has wavelengths generally contained between 700 and 2500 nanometers (nm), which places it just beyond the limit of red visible light. They are found in particular in spectroscopy, remote sensing, astronomy, telemetry, medical imaging (for example, pulse oximetry), and materials analysis. They are often used to measure the chemical composition of substances.
- Mid-infrared has wavelengths between approximately 2500 and 5000 nm up to approximately 25,000 nm (or 25 micrometers). This range includes thermal infrared. They are used in infrared spectroscopy to analyze the chemical composition of molecules. They are also essential for gas detection, infrared thermography, non-contact temperature measurement and chemical bond characterization.
- Far infrared, on the other hand, has much longer wavelengths than the other categories, generally above 25,000 nm (25 micrometers) and extending into the millimeters. They are mainly used in astronomy to observe emissions from celestial objects, such as galaxies and stars, which mainly emit in this part of the spectrum. They are also used in materials research, particularly for the study of crystalline and molecular vibrations.
(Wavelengths of the electromagnetic spectrum)
Infrared radiation is generated by various physical mechanisms that involve the movements of atoms and molecules. One of the most common mechanisms is the emission of thermal radiation, also called black body radiation. When objects are heated, their atoms and molecules vibrate and rotate more quickly, emitting infrared photons.
Another mechanism for generating infrared radiation is the absorption and re-emission of photons by molecules. Molecules can absorb energy in the form of photons in the infrared range, causing changes in their energy levels. Subsequently, they emit infrared photons when they return to their original state.
Finally, collective movements of electric charges, such as oscillations of molecular dipoles in polar molecules, can also generate infrared radiation. These charge movements induce variations in the dipole moment, which results in the emission of infrared photons.
Materials play a crucial role in the interaction with infrared (IR) radiation. Some materials naturally emit IR, which is often used in thermal sensing applications, such as temperature sensors. Other materials are excellent IR absorbers, meaning they absorb infrared energy efficiently, causing their temperature to increase. Materials used in thermal coatings and solar panels are good examples. Finally, some materials transmit IR without absorbing or emitting a large amount of radiation, making them useful in windows and IR optics, allowing vision through thermal barriers while preserving thermal insulation
When an object or surface is heated or cooled, its atoms and molecules vibrate at specific frequencies depending on the temperature. This vibration generates infrared radiation whose intensity depends on the temperature of the object. The thermal camera detects this infrared radiation and converts it into a thermal image where temperature variations are represented on a gray tone scale or a color scale (when applying a colorization palette).
Thermography is used in many applications: building inspection, preventive maintenance, medicine, security and surveillance but also in scientific research.
Infrared radiation continues to be of critical importance in many industries and fields due to its unique thermal sensing and thermal imaging capabilities.
Near, mid and far infrared radiation are distinguished by their wavelengths and specific applications. Near infrared is used for spectroscopy and chemical sensing applications, mid infrared is used for chemical analysis and thermography, while far infrared is primarily used in astronomy and materials research.
Thermography is a powerful technique for detecting temperature variations, providing rapid, non-invasive visualization of thermal issues and environmental conditions. It finds applications in many fields, from construction to medicine, security and research.
The introduction of solutions such as IRis further improves the ability to process thermal video streaming in real time, paving the way for more efficient and innovative applications in the future.
Discover how this advanced technology can drive efficiency and innovation in various areas, dive into the details by exploringour page dedicated to IRis.
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