Concepts for Day-Night Stereo Obstacle Detection in the Pantograph Gauge

Obstacles in the pantograph gauge cause damage and time delays when colliding with the pantograph. We have built an onboard system that avoids collisions by automatically detecting such obstacles at about 70 m in front of the train and retracting the pantograph in time. The system consists of three cameras mounted collinearly inside the train behind the front window. Up to now, the system only works when sufficient daylight is available. In this paper, we present methods for extending the system for operation at night and in tunnels. Within this context extension means that our concept of stereo triangulation via three cameras is to be kept as far as possible. In this paper, active as well as passive night vision techniques in the ultraviolet, visible and infrared spectrum are surveyed. Overall concepts for day-dawn-night vision are shown. These concepts are analyzed with regard to their applicability and results are presented. We conclude that thermal infrared is the best technique for our application since day and night images look the same.