An Alternative of LIDAR in Nighttime: Unsupervised Depth Estimation Based on Single Thermal Image
Most existing autonomous driving vehicles and robots rely on active LIDAR sensors to detect the depth of the surrounding environment, which usually has limited resolution, and the emitted laser can be harmful to people and the environment. Current passive image-based depth estimation algorithms focus on color images from RGB sensors, which is not suitable for dark and night environment with limited lighting resource. In this paper, we propose a framework to estimate the scene depth directly from a single thermal image that can still observe the scene in the low lighting condition. We learn the thermal image depth estimation framework together with RGB cameras, which also mitigates the training condition due to the easy availability of RGB cameras. With the translated thermal images from color images from our generative adversarial network, our depth estimation method can explore the unique characteristics in thermal images through our novel contour and edge-aware constraints to obtain a stable and anti-artifact disparity. We apply the commonly available color cameras to navigate the learning process of thermal image depth estimation framework. With our approach, an accurate depth map can be predicted without any prior knowledge under various illumination conditions. Experiments in public dataset, as well as our newly collected data, demonstrate superior performance of our method on single thermal image depth estimation compared with other state-of-the-art algorithms.