Infrared occupant position detection system and method for a motor vehicle

Abstract

An improved IR occupant position detection system that provides accurate and reliable classification and position information at a speed sufficient to timely inhibit or otherwise control deployment of occupant restraints. A two-dimensional array of IR emitters is selectively activated to periodically illuminate two or more of predetermined viewing planes in the vicinity of a passenger seating area, and the reflected IR energy is detected by a photo-sensitive receiver and analyzed to detect the presence of an occupant, to classify the occupant, and to identify and dynamically track the position of the occupant's head/torso relative to predefined zones of the passenger compartment. Modulating the intensity of the emitted IR beams with a known carrier frequency, band-pass filtering the received signal, and synchronously detecting the filtered signal distinguishes the reflected IR energy from other signals picked up by the IR receiver. Additionally, a two stage adaptive control mechanism compensates for the variation in intensity of the reflected energy with distance between the emitter and the occupant. The emitter is implemented with orthogonal anode and cathode power rails with individual IR LED elements placed at each anode-cathode intersection. Optical dispersion within the package is greatly reduced by an opaque cover layer that effectively forms a well for each LED element.