The same infrared, the difference is that the wavelength is different. The specific breakdown is as follows:
Near infrared (NIR, IR-A DIN): wavelengths in the 0.75-1.4 microns, defined by the absorption of water, commonly used in fiber optic communications due to the low attenuation rate in silica glass. Wavelengths in this region are very sensitive to image enhancement. Examples include night-vision equipment, like night-vision goggles.
Short wavelength infrared (SWIR, IR-B DIN): 1.4-3 microns, water absorption increases significantly at 1,450 nm. 1,530 to 1,560 nm is the main spectral region dominating long range communications.
Mid-wavelength infrared (MWIR, IR-C DIN) is also known as mid-infrared: wavelengths in the range of 3-8 microns. Passive infrared heat-seeking guided missile technology is designed to work using the atmospheric window in the 3-5 micron band, homing in on an aircraft's infrared markings, usually against the plume emitted by the aircraft's engines.
Long wavelength infrared (LWIR, IR-C DIN): 8-15 microns. This is the "thermal imaging" region, where sensors in this band do not require other light or external heat sources, such as the sun, moon, or infrared lamps, to obtain a complete passive image of thermal emissions. Forward-looking infrared (FLIR) systems use this region of the spectrum. It is sometimes categorized as "far infrared."
Far infrared (FIR): 50-1,000 microns (see Far Infrared Laser).
NIR and SWIR are sometimes referred to as "reflected infrared", while MWIR and LWIR are sometimes referred to as "thermal infrared", based on the properties of the blackbody radiation curve. Typical 'hot' objects, such as an exhaust pipe, will usually appear brighter in the MW band than in the LW band for the same object.
Discovery of infrared light
In 1666 A.D. Isaac Newton discovered the spectrum and measured 3,900 angstroms to 7,600 angstroms (400 nm to 700 nm) as the wavelength of visible light. On April 24, 1800 William Herschel of the Royal Society in London, England, published the sunlight in the visible spectrum of the red light outside there is an invisible extension of the spectrum, with thermal effects.
The method he used was very simple, using a thermometer to measure the temperature of each color of light through the prism after spectroscopy, from violet to red, and found that the temperature gradually increased, but when the thermometer was put into the red light outside the part of the temperature is still continuing to rise, and thus concluded that there is the existence of infrared light.
The same test was done on the ultraviolet part, but the temperature did not increase. Ultraviolet light was discovered by Ritter in 1801 using a silver chloride sensitizer.
The wavelength of near-infrared light that can be sensed by a negative is twice the wavelength of light visible to the naked eye. The upper limit of wavelengths that can be recorded with a negative is 13,500 angstroms, and with other special equipment, it can reach up to 20,000 angstroms, and beyond that, it is necessary to use a physical instrument to detect.