Hyperspectral and multispectral imaging

Hyperspectral and multispectral imaging

The hyperspectral imaging and multispectral imaging brings information to light. Both technologies uses the spatial and wavelength-separated detection in different electromagnetic wavelength-ranges (spectrum).

ultraviolet light (UV) spectral range 50 nm – 400 nm
visual light spectral range 400 nm – 750 nm
near infrared light spectral range 750 nm – 2500 nm
mid-infrared (MIR) spectral range 2500 nm – 10000 nm
Embedded in grass, the ‚IWS‘ writing was made of snthetic turf and visualized by hyperspectral imaging
© Fraunhofer IWS Dresden
Embedded in grass, the ‚IWS‘ writing was made of snthetic turf and visualized by hyperspectral imaging

The difference between multispectral and hyperspectral imaging is the number of the acquired spectral points. For a ‚real‘ hyperspectral imaging 100 spectral points should be acquired at least. Hyperspectral systems works in most cases – due to a line-wise scanning – as pushbroom imager, whereas the most multispectral imager record the whole image in one shot. The spectrum is then generated by the propagation of light through different optical filters (‚multichannel‘), sub-pixel-structures (‚Filter-on-Chip‘) or special prisms.

In accordance to the detector technolgy, hyperspectral and multispectral cameras will be often differentiated in respect to the usable wavelength ranges:

 

UV
  • detection range 250 nm – 500 nm
  • UV-enhanced Si-detector
  • applications: fluorescence imaging, ultra-thin layers etc.
VNIS
(abbrev.: VIS-NIR)
  • detection range 400 nm – 1000 nm
  • Si-detector
  • applications: optical properties (reflection, color), security features, fluorescence, surface structure, thin films etc.
NIR
  • detection range 900 nm – 1600 nm
  • InGaAs detector
  • sample structure, chemical composition, contaminations, defects
SWIR
(abbrev.: short wave infrared)
  • detection range 1000 nm – 2500 nm
  • MCT detector
  • smaple structure, chemical composition, contaminations, combinatoral vibrations
MIR
  • detection range 2500 nm – 10000 nm
  • MCT detector
  • chemical groups and features, ground vibrations