Platform screen doors
Platform screen doors are used in crowded train or subway stations to avert accidents by creating a barrier between the train and the passengers waiting on the platform.
While the train is in the station and train doors are open, a camera checks the space between the train and the platform gate. Once passengers have boarded or departed the train and the "gap" is empty, the camera signals to the system controller that the doors can be closed.
In modern train stations the space between train and platform is narrow and light beams or light curtains can reliably detect objects and passengers. In older stations, however, the gap between the train and platform is wider 3D cameras are the best devices to monitor such a large space.
The sensor of the MESA SR4000 acts as the equivalent of 25’000 individual light beams. With a viewing angle of 70 x 55 degrees, it achieves an angular resolution of less than 0.5 degrees, enabling reliable detection of small objects such as the arm of a child or an umbrella sticking out of the train door.
TOF cameras from MESA are designed for continuous operation in a train station environment. Unlike laser scanners, they have no moving parts and are therefore extremely robust against the mechanical vibrations produced by approaching or departing trains.