- Near-infrared (NIR): 700–1000 nm
- Short-wavelength infrared (SWIR): 1000–2500 nm
- Mid-wavelength infrared (MWIR): 3000–5000 nm
- Long-wavelength infrared (LWIR): 8000–14000 nm
SWIR possesses less energy than near-infrared, but more than mid-wavelength infrared (MWIR). SWIR radiation actually has quite a lot in common with light in the visible spectrum (400–700 nm), because photons in this wavelength range are either reflected or absorbed to varying degrees by different organic and inorganic materials. Studying the contrast between SWIR-reflective and SWIR-absorbent materials has opened the door to new technologies, such as machine vision and hyperspectral imaging.
Identifying and categorizing materials with SWIR LEDs
Many organic materials absorb rays in the 1000–1800 nm range, which makes short wavelength infrared (SWIR) LEDs particularly useful in a large number of applications. When more rays are absorbed, as in the case of materials with high moisture content like fruit and vegetables, SWIR imaging produces a ‘darker’ image; by contrast, materials or substances which reflect more rays will appear ‘brighter’. This type of spectroscopy can be used to monitor the nutritional value of food, which is a critical component of agricultural and processed food production, or identify foreign objects for removal.
SWIR technology allows analysis of material characteristics beyond the visual capability of the human eye. In particular, water, sugars, and proteins absorb the majority of the wavelengths in the SWIR band. The most common food ingredient, water, is measured for a variety of purposes, for example, ensuring the water content of baked cookies remains consistent in every batch.
From Kyoto with Love: engineering LEDs at the one-stop SSL shop
The semiconductor materials used to construct light-emitting diode (LED) chips, which consist of a luminous layer and a substrate, depend on the desired output wavelength. The full Ushio Epitex LED range covers a wide spectrum from 365 nm ultraviolet (UV) emitters, through visible light and NIR, up to 1750 nm SWIR.
Depending on the intended application, Ushio’s Epitex LED series offers the opportunity to select from a number of wavelengths, package types, and lenses for the modification of radiation distribution and intensity. Further customization is possible, with various photo-detection and heat sinking features available.
At Ushio’s state-of-the-art facilities in Kyoto, Japan, the entire LED manufacturing process can take place internally, from epitaxial formation to packaging processing. Utilizing over 30 years of LED experience and 1,500 construction combinations, configuration demands of any application can be met, such as multiple wavelengths and a photodiode in a single package.
From beginning to end: designing and constructing LEDs with Ushio Epitex
In more recent times, Ushio perfected the in-house development of LED chips and lenses that facilitate SWIR wavelengths between 1050 nm and 1750 nm. Over 15 years of research and experimentation found a gallium indium arsenide phosphide (GaInAsP) luminous layer interfaced with an indium phosphide (InP) substrate forms the ideal SWIR LED.
With center wavelengths available in increments of 50 or 100 nm, Ushio SWIR chips boast a wavelength variation of as low as ±10 nm. Meanwhile, the nearest competitors fall short of this accuracy, with a variance of more like ±50 nm.
Ushio’s SWIR photodetectors, on the other hand, generally use indium gallium arsenide (InGaAs). These sensors are considered to be more expensive than the common silicon (Si) and complementary metal-oxide-semiconductor (CMOS) sensor types, but the ability to detect the SWIR wavelengths beyond 1000 nm is largely lacking with those technologies.
Contact Ushio about the applications of SWIR
If you would like to learn more about short-wavelength infrared radiation and its applications, please contact Ushio’s regional experts:
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