Infra-red imaging is beyond the visible spectrum, starting about 800nm and extending beyond. Humans cannot see these wavelengths but they do reveal interesting and often very important data. But to see or image this, it is necessary to use special sensor/camera technology. Once imaged we can then process the data and make informed decisions about objects and scenes that we would otherwise be blind to in the visible spectrum. Examples are heat, water density and material differentiation.
Water has a fairly high absorption rate between 1400-1900nm meaning you can observe high concentration of water using SWIR cameras. Think bruised fruit or monitoring water content in crop fields. IR Imaging technology offers solutions that we cannot do with visible imaging, such as differentiating between plastic, organic and non-organics materials. There is also the more commonly known use, which is imaging radiated heat.
Using a N-IR camera with N-IR lighting can be a powerful way to ‘remove’ colour from an image.
Removing colour can reveal product detail making it easier to process and will give more robust results.
SWIR is powerful technology, allowing us to view outside the visible spectrum and detect for example, bruised fruit and fill levels on bottles.
Gated SWIR imaging can be used to prevent fog or smoke obscuring an object, making it possible to see through and image what is happening ‘beyond’ the fog/smoke.
Thermal cameras detect and image radiated heat, not visible light. Applications include;
Short Wave Infra-red uses InGaAs sensors. With a spectral response from 900-1700nm, these are particularly well suited for hot glass inspection. Glass is transparent in this band, so the user can image through glass. Think of a hot glass jar – using SWIR it is possible to see the details in the bulk/ and on both faces of the jar at the same time. Ideal for crack detection and inspecting for contamination such as a foreign body.
Visible wavelengths and Near-IR use silicon based sensors, but these are blind above 1100-1200nm. As the band moves from 900-1700nm a different sensor technology is required and that is called InGaAs, used in SWIR cameras. Next is Medium Wave IR is which very exotic and requires very expensive Indium Antimonide sensors (Multipix does not offer products in this range). Moving further along the spectrum we come to Long Wave IR which is used for thermal imaging and commonly use Microbolometer sensors.