HYPERSPECTRAL IMAGING


systems,’ Løke said. ‘With Mjolnir it was the first time when you could obtain scientific grade hyperspectral data with such a small camera. Making the camera so small and good would not be possible without the appropriate optical design.’ Pixel-level design is important because all


spectral channels in one spatial pixel must sample data from exactly the same area, so that data is spatially co-registered. ‘If you have spatial misregistration the spectral information in an image pixel is made up by parts of the spectra from spatial positions around that pixel,’ Løke added. ‘Similarly, you want any spectral channel of your hyperspectral camera to have exactly the same central wavelength throughout the entire field of view, you want your data to be spectrally co-registered.’ As such, HySpex often needs to correct aberrations on a sub-pixel level, whereas traditional imaging system aberrations are comparable to pixel size. ‘We prefer to have a wide choice of optical glass types to fulfil these very demanding image quality requirements,’ Løke said. Spatial and spectral co-registration


in a real camera are never perfect, Løke admitted. ‘But you want it to be as perfect as possible,’ he added. ‘Spatial and spectral misregistration in our cameras are low,


optical systems with a 1˚ field of view and 60˚ field of view will be very similar. Also, every now and then comes an application that has strong emphasis on a single specification, such as light throughput or weight or size. Ten it makes sense to make a new design that excels at the most important specification.’ As an example, HySpex has just released


HySpex’s Mjolnir product offers good quality data in a small hyperspectral system


and this, in combination with very sharp optics, is one of the key advantages when using our systems. We can detect and identify significantly smaller objects than most other cameras with seemingly similar specifications.’ Consequently, high quality hyperspectral


cameras are not particularly cheap, said Løke, but they can be versatile. ‘We try to create systems that can be used in a wide variety of applications,’ he said. ‘However, there are limits to that. It is unlikely that two


a short-wave infrared (SWIR) camera that spans 640 spatial pixels. ‘In the SWIR world, this is a high pixel count,’ said Løke. ‘We are happy that we managed to keep the same per pixel image quality as in our SWIR 384 system. Of course, we are constantly working on developing new products, and I believe that in a year or two from now I will be able to mention another new HySpex system.’ Tanks to such products, hyperspectral


imaging is being used ever more broadly, said Delta Optical Tin Film’s Pust. ‘It has been hyped for several years now, but it didn’t really pick up to become a really volume application,’ he said. ‘It’s now that people realise what you can do with it. Tey also see that there are now cameras on the market that are easier to handle for many more applications. So I see hyperspectral imaging getting broad acceptance and use in many different areas.’ O


HySpex


Pickit


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