Development of Octo-Rotor UAV Prototype with Night-vision Stereo Camera System Used for Nighttime Visual Inspection

This paper presents an octo-rotor unmanned air vehicle (UAV) prototype and its vision system used for nighttime visual infrastructure inspection. After developing a stereo vision system using two inexpensive night-vision cameras for obtaining depth information, we conducted a comprehensive evaluation experiment to assess its practical use, to support the design and manufacture of our prototype, to build a camera system including a dedicated camera mount, and to compare and evaluate stereo matching algorithms. The nighttime inspection yielded depth images using stereo matching algorithms of four types for nighttime aerial photography of parallax images. We evaluated optimal stereo matching for nighttime aerial photographs. The experimentally obtained results revealed that the contrast between structure outlines and depth information was extracted clearly for the highest accuracy stereo matching result. Results show that our system concept can open up a new field of inspecting structures using nighttime aerial photography.