SPONSORED: HYPERSPECTRAL IMAGING
Hyperspectral cameras are primarily used in remote sensing and agricultural applications, in which scanning or push-broom cameras are installed on satellites, aircraſt or UAVs
The future of hyperspectral imaging
Gemma Church talks to Pro-Lite Technology about next-generation, cost-effective hyperspectral imaging technologies
I
maging spectroscopy is an established technique where each captured pixel comprises many bands
of light intensity data across the electromagnetic spectrum, instead of the three bands used by traditional RGB cameras. We often divide imaging
spectroscopy into two categories. There are multispectral cameras, which are restricted to narrow spectral bands (typically three to 15), and hyperspectral cameras, which can collect a larger number of distinct, yet contiguous bands across a wide spectral range – up to several hundred. There are many different
28 Electro Optics July 2021
technologies for both types of imaging, each bringing specific strengths and a place in the growing market and application space.
Hyperspectral cameras, for
example, are primarily used in remote sensing and agricultural applications. Scanning or push- broom cameras are installed on satellites, aircraft or UAVs, with push-broom scanning where one narrow spectral line in the scene is imaged at a time, and the line is split into its spectral components before reaching the sensor array. On the 2D sensor array, one dimension is used for spectral separation and the second dimension is for imaging in one spatial direction. The second spatial dimension in the scene arises from scanning the camera over the scene (for example by means of a UAV or the movement of an aircraft). The result is one 2D image
for each spectral channel. Alternatively, every pixel in the image contains one full spectrum. Compared to ‘snapshot’ or real-time
spectral imagers, push-broom instruments trade higher spectral and spatial resolution for reduced measurement speed. Nick Barnett, business
development manager at Pro-Lite Technology, explained: ‘Push- broom cameras are ideal for imaging objects on a conveyor belt or from a UAV or aircraft, where there is inherent scanning due to the movement of either the camera or object under investigation.’ In the company’s latest white
paper, Pro-Lite Technology explains how hyperspectral imaging is changing. Several new approaches and applications are introduced, some of which have the potential to significantly reduce costs and resolve some of the long-standing technical and operational issues with these devices. Both push-broom and snapshot technologies will continue to have a strong foot- hold in the market, according to Barnett, who added: ‘High-end applications using UAVs, aircraft and satellites will probably
continue to be served by push- broom cameras that will provide increasing spectral and spatial resolution.’ We’ll also see these snapshot
techniques appearing in an increasing number of consumer devices. Barnett added: ‘Snapshot techniques providing video-rate hyperspectral and multispectral imaging will be adopted by machine vision, robotics and medical applications. I expect there to be a huge increase in low-cost multispectral cameras designed for specific tasks based on bespoke filter sets. It also won’t be long before spectral cameras based on MEMS sensors or mosaic filter technology are embedded on mobile phones, with a selection of apps for specific tasks.’ But traditional push-broom
cameras still have limitations, particularly when it comes to some applications, and often with regards to the cost of the system. Barnett said: ‘Where the object of interest is static, an external scanning mechanism is required with accompanying
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