Surveillance sensor systems using CMOS imagers
Surveillance sensors are being applied in factory automation systems, traffic control, entrapment protection, automotive safety systems and in other applications where information about the occupancy of a scene is required. In order to detect object motion several methods exploiting distinct physical phenomena, e. g. passive infrared sensors or active microwave sensors, have been realized. When comparing all of the applicable methods, the electro-optical approach outperforms with respect to the spatial resolution of the monitored area. Therefore, electro-optical sensors are able to provide additional information, e. g. to predict the direction of motion, or to localize and identify objects. However, convenient image processing systems using CCD sensors for image acquisition and DSP or µP boards for signal processing and classification are not well suited for dedicated, powerful and cost-effective optical sensor solutions. In contrast to this mainstream approach CMOS based imaging techn ologies offer novel solutions in both the design and applications of electro-optical surveillance sensors. This contribution discusses CMOS imagers operating principles and describes certain architectures and applications for passive and active surveillance sensors. The capabilities to realize on-chip motion detection and range sensing using fast shutter devices are illustrated. We conclude with a discussion of the status of CMOS surveillance sensors and suggest trends for future applications.