CIE division scheme
The International Commission on Illumination (CIE) recommended the division of optical radiation into the following three bands:[4]
- IR-A: 700 nm?1400 nm
- IR-B: 1400 nm?3000 nm
- IR-C: 3000 nm?1 mm
A commonly used sub-division scheme is:[5]
- Near-infrared (NIR, IR-A DIN): 0.75-1.4 ?m in wavelength, defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles.
- Short-wavelength infrared (SWIR, IR-B DIN): 1.4-3 ?m, water absorption increases significantly at 1,450 nm. The 1,530 to 1,560 nm range is the dominant spectral region for long-distance telecommunications
- Mid-wavelength infrared (MWIR, IR-C DIN) also called intermediate infrared (IIR): 3-8 ?m. In guided missile technology the 3-5 ?m portion of this band is the atmospheric window in which the homing heads of passive IR 'heat seeking' missiles are designed to work, homing on to the IR signature of the target aircraft, typically the jet engine exhaust plume.
- Long-wavelength infrared (LWIR, IR-C DIN): 8?15 ?m. This is the "thermal imaging" region, in which sensors can obtain a completely passive picture of the outside world based on thermal emissions only and requiring no external light or thermal source such as the sun, moon or infrared illuminator. Forward-looking infrared (FLIR) systems use this area of the spectrum. Sometimes also called the "far infrared."
- Far infrared (FIR): 15-1,000 ?m (see also far infrared laser)
NIR and SWIR is sometimes called "reflected infrared" while MWIR and LWIR is sometimes referred to as "thermal infrared." Due to the nature of the blackbody radiation curves, typical 'hot' objects, such as exhaust pipes, often appear brighter in the MW compared to the same object viewed in the LW.
-----Original Message-----
From: ADavidhazy [mailto:andpph@xxxxxxx]
Sent: Sunday, February 22, 2009 12:04 PM
To: 'List for Photo/Imaging Educators - Professionals - Students'
Subject: Infrared schminfrared
Let me add my $.02 Wavelengths beyond the red (at least for a while) are generally called infrared (or near infrared if close to the visible, like from 700 to 1000 nm and far infrared if above 1000 nm - I just made this up!) but anything that is "imaged" by "thermal infrared" is essentially still infrared but it should be clearly labeled as such and not just be called infrared. Standard digital cameras, like film cameras, can't deal with thermal infrared since the bodies would become warm by the mere act of holding the camera body. AFAIK "infra" simply implies beyond ... there are a lot of wavelengths with special names that are out there beyond infrared in all its manifestations. Then there are the digital newcomers on the block that state they can through software make infrared images - no! if you don't record infrared in a scene no amount of software magic will include in the image any true infrared. One can guess but never be sure since we can't see it. OTSOTM and JMO - ;) andy
