Infrared light is more useful and has a wide range of uses, which are illustrated by a few examples:
(1) Night Vision
Infrared light is used in night vision devices when there is not enough visible light. Night vision devices operate through a process that involves converting ambient photon photons to electrons, which are then amplified through chemical and electronic processes and then converted back to visible light. Infrared light sources can be used to enhance the available ambient light converted by night vision devices, increasing visibility in the dark without the need for a visible light source. The use of infrared light and night vision equipment should not be confused with thermal imaging, which generates images based on differences in surface temperatures by detecting infrared radiation (heat) emitted from an object and its surroundings.
(2) Thermal imaging
Infrared radiation can be used to remotely determine the temperature of an object (if the emissivity is known). This is known as temperature recording, or pyrometry in the case of very hot objects or visible in NIR. Thermal imaging (thermography) is primarily used for military and industrial applications, but due to the massive reduction in production costs, the technology has entered the public market in the form of automotive infrared cameras. Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum (approximately 900-14,000 nanometers or 0.9-14 microns) and produce an image of that radiation. Since infrared radiation is emitted by all objects depending on their temperature, and in accordance with the blackbody law of radiation, a thermal imaging camera can "see" a person's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, so thermal imaging allows one to see changes in temperature (hence the name).
(3) Heating
Infrared radiation can be used as a deliberate heating source. For example, it is used in infrared saunas to heat the occupants. It can also be used for other heating applications, such as removing ice from airplane wings (de-icing). Infrared can be used for cooking and reheating food because it primarily heats opaque, absorbent objects rather than the air around them. Infrared heating is also becoming more popular in industrial manufacturing processes such as coating curing, plastic forming, annealing, plastic welding and print drying. In these applications, infrared heaters replace convection ovens and contact heating. Efficiency is achieved by matching the wavelength of the infrared heater to the absorption properties of the material.
(4) Communication
Infrared data transfer is also used for short-range communication between computer peripherals and personal digital assistants. These devices typically conform to standards published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation that is focused into a narrow beam through a plastic lens. The beam is modulated, i.e., turned on and off, to prevent interference from other infrared sources such as daylight or artificial light. The receiver uses a silicon? photodiode to convert infrared radiation into electrical current. It responds only to fast pulsed signals generated by the transmitter and slowly filters out the changing infrared radiation from the ambient light. Infrared communication is suitable for indoor use in densely populated areas. Infrared does not penetrate walls and therefore does not interfere with other devices in adjacent rooms. Infrared is the most common way for remote controls to control appliances. Infrared remote control protocols (e.g. RC-5, SIRC) are used to communicate with infrared. Free-space optical communication using infrared lasers may be a relatively inexpensive way to install communication links in urban areas operating at speeds of up to 4 gigabits per second, compared to the cost of burying fiber optic cables, except for radiation damage. "Since the eye cannot detect infrared, blinking or eye closure to help prevent or minimize damage may not occur." Infrared lasers are used to provide light for fiber optic communication systems. Infrared light with a wavelength of approximately 1,330 nanometers (minimum dispersion) or 1,550 nanometers (optimum transmittance) is the best choice for standard silica fiber. IR data transmission of encoded audio versions of printed signs is being investigated through the RIAS (Remote Infrared Acoustic Signage) program to assist the visually impaired. Transmitting IR data from one device to another is sometimes referred to as luminescence.
(5) Astronomy
Astronomers use optical components (including mirrors, lenses, and solid-state digital detectors) to observe objects in the infrared portion of the electromagnetic spectrum. For this reason, it is categorized as part of optical astronomy. To form images, the components of an infrared telescope need to be carefully shielded from heat sources, and the detectors are frozen using liquid helium.
The sensitivity of ground-based infrared telescopes is significantly limited by atmospheric water vapor, which absorbs a portion of the infrared radiation arriving from the outer space of selected atmospheric windows. This limitation can be partially mitigated by placing the telescope observatory at a high altitude, or by carrying a balloon or airplane high above the telescope. Space telescopes are not plagued by such obstacles, so outer space is considered an ideal location for infrared astronomy.
The infrared portion of the spectrum has several useful benefits for astronomers. The cold, dark molecular clouds of gas and dust in our galaxy will be illuminated by stars embedded in the radiant heat exposure. Infrared can also be used to detect protostars before they start emitting visible light. Stars in the infrared spectrum emit a small amount of energy, making it easier to detect cool objects such as planets nearby. (In the visible spectrum, the glare from the star will drown out the reflected light from the planet.)
Infrared light is also useful for looking at the cores of active galaxies, which are usually cloaked in gas and dust. Distant galaxies with high redshifts will have the peak portion of their spectra shifted toward longer wavelengths, so they are easier to observe in the infrared.
Extended reading:
Infrared radiation (IR) is electromagnetic radiation (EMR) that has longer wavelengths than visible light, and is therefore usually invisible to the human eye (although IR from certain pulsed lasers with wavelengths of up to 1050 nm can be seen by humans under certain conditions). It is sometimes referred to as infrared light.IR wavelengths extend from the nominal red edge of the visible spectrum at 700?nm (frequency?430?THz) to 1?mm (300?GHz) Most thermal radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy and behaves both like waves and like its quantum particles, described as photons.
Infrared radiation was discovered by astronomer Sir William Herschel in 1800, who through its effect on thermometers came to discover a type of radiation with a spectral energy lower than that of red light, invisible. More than half of the Sun's total energy is eventually found to reach the Earth in the form of infrared light. The balance between absorbed and emitted infrared radiation has important implications for Earth's climate.
Infrared radiation is emitted or absorbed by molecules as they change their rotational vibrational motion. It excites vibrational modes in molecules through changes in dipole moments, making it a useful frequency range for studying these energy states in properly symmetrical molecules. Infrared spectroscopy examines the absorption and transmission of photons in the infrared range.
Infrared radiation is used in industrial, scientific, military, law enforcement, and medical applications. Night vision equipment using active near-infrared illumination can observe people or animals without detecting an observer. Infrared astronomy uses telescopes equipped with sensors to penetrate dusty regions of space such as molecular clouds, to detect objects such as planets, and to view highly redshifted objects in the early universe. [8] Infrared thermography cameras are used to detect heat loss in insulated systems, to observe altered blood flow through the skin, and to detect overheating in electrical equipment.
The wide range of uses for military and civilian applications include target acquisition, surveillance, night vision, homing and tracking. The human body at normal body temperature primarily radiates at wavelengths around 10 micrometers (μm). Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspection, growth detection, remote temperature sensing, short-range wireless communications, spectroscopy and weather forecasting.