Compact, UAV-mounted hyperspectral imaging system with automatic geometric distortion rectification.

A highly compact hyperspectral imager with an automatic geometric rectification function is developed in this study, which can be mounted on a UAV for ultra-wide range hyperspectral imaging. For better application, the system can provide visible light image transmission and hyperspectral imaging in the real-time mode. A specific design is proposed to allow the visible light camera and hyperspectral camera to share the same telescope optical path, making the system have a high integration level with a total mass of 1.9 kilograms. Thanks to the sharing-optical-path design, the field of view (FOV), frame rate, and spatial resolution are modified the same between the visible light camera and hyperspectral camera. As a result, the geometric rectification is easily performed, and repeated rectifications are eliminated to improve the imaging efficiency. A FOV of 40 degrees in the frame direction and 26 degrees in the flight direction are realized with a focal length of 13mm, providing a large spectral range from 400 nm to 1000 nm and an excellent spectral resolution of 2.5 nm. An automatic geometric rectification workflow is presented and verified in experiments, which can improve the geometric rectification of hyperspectral images in the presence of low-quality UAV navigation data through the incorporation of frame images. Experimental results show that the relative accuracy of geometric rectification is less than 2 pixels when applying the algorithm to our system dataset.