Hyperspectral imaging involves dividing light into thousands of small bands to gain detailed information. This compares with multi-spectral, which deals with far fewer bands. Every pixel has a complete spectrum in it and this can be used for a variety of applications including mineralogy, agriculture, astronomy, and surveillance. With lightweight hyperspectral imaging systems mounted on fixed wing aircraft and small UAVs, accurate data over very large areas.
Figure 1. Example Hyperspectral Image
These systems can effectively monitor the health of crops, ‘seeing’ water and nutrient levels and the presence of hard-to-spot diseases. They can provide access to challenging areas such as swamps, Antarctica, and mountainous regions. Hyperspectral imaging has enabled many advances in precision agriculture.
Precision agriculture requires more than just basic RGB information. For example, video images flying over a field would not be able to accurately distinguish real plants from fake ones. Looking at the spectral content in the pixels, hyperspectral solutions can detect chlorophyll or very small color-changes on foliage. Color information can be useful to distinguish brown from green, but more bands are required for finer details.
One example is the inspection of orange groves to look for citrus blight disease done by Headwall Photonics’ Hyperspec® VNIR hyperspectral solution using an Adimec OEM camera core. Citrus blight destroys the vitality of trees and can spread throughout the grove. One of the early signs of this disease is a byproduct secreted on the surface of the leaves. Inspection for this used to require a man climbing a ladder to inspect the top of each tree. More often, growers might not know of a problem until trees started dying. With hyperspectral imaging, this can be seen 300-400 meters above the crops covering a large area quickly (mounted on UAVs). Any problems can be quickly dealt with to eliminate the spread and minimize the destruction.
There were several reasons an OEM/industrial camera were required as opposed to a security type camera or video camera. Security cameras are typically limited to 30 fps, which is not enough to gather the necessary data. Since the UAVs fly relatively close to the ground, faster frame rates are required to get images of the entire area. The Adimec camera offered 1 Megapixel at 50 fps and then functionality for binning and region of interest enabled the desired resolution at 85 fps. With frequent flights, hard landings and outdoor environmental conditions, a rugged, lightweight camera design also reduces/eliminates repair issues.
For more information, contact Adimec or Headwall Photonics.