Whenever a person or surveillance system is trying to capture clear photographs or smooth video, light plays a very important role. Most people have taken a video and seen that the resulting footage is over or under exposed because the camera is unable to adapt to the challenging light environment. Trains are noted for being a particularly difficult environment to film in and several unique challenges arise and must be overcome in order to achieve consistently smooth video footage. For example, a fast-moving train will often experience severe light fluctuations when traveling through tunnels, open air and shade, or when another train passes by. These challenges are not limited to what is happening outside of the train, but also include onboard challenges such as the lights being switched on and off, and doors opening and closing. In order to ensure clear imagery on trains, a tailor made solution is required.
Technology overview and the challenges
Auto Exposure (AE) is a technology that has been around for many years. It adjusts the shutter, IRIS, and gain (for red, green, and blue components) based on the ambient light captured by the sensor. The AE algorithm uses an image taken in ideal light conditions and stores it as a reference image. If the current image brightness is higher or lower than the reference image, the AE algorithm will adjust the current image to make it the same as the reference image. However, if the change of brightness affects a small part of the overall image, or if there is a significant light change in a small area, the traditional AE algorithm will readjust the whole image, which is a problem that must be addressed before the AE feature can be effectively deployed on trains.
Moxa will be showcasing its latest technologies at Booth E10 at the 19th Annual Asia Pacific Rail conference and exhibition taking place from 21-22 March at HKCEC, Hong Kong. Admission to expo is free – Get your free expo pass here.