Optical speed-over-ground sensors for on-board vehicle speed measurement

Speed-over-ground (SOG) sensors can provide a potentially important input to advanced vehicle control systems, including instrumentation, navigation, braking, traction and steering. The basic requirements for automotive use include low cost, a speed range of 1-50 m/s, and a temperature range of -40-+85°C. A measuring rate of 10-50 Hz is needed in some applications. Exposure to rain or contamination and various road surface conditions should also be considered. The authors have chosen the optical spatial filtering technique, due to its simple construction and low cost. The sensor consists of a light source, imaging optics, and a photodetector array. The authors briefly discuss the principle of operation, its performance, and possible improvements