An Ultra-Low-Power Contrast-Based Integrated Camera Node and its Application as a People Counter

We describe the implementation in a self-standing systemof a novel contrast-based binary CMOS imaging sensor.This sensor is characterized by very low power consumptionand wide dynamic range, which makes it attractive forwireless camera network applications. In our implementation,the sensor is interfaced with a Flash-based FPGA processor,which handles data readout and image processing.This self-standing camera node is configured as a system forcounting persons walking through a corridor. Simple featuresare extracted from each image in a video stream at 30fps. A classifier is designed based on the temporal evolutionof these features, which is modeled as a Markov chain. Thevideo stream is then segmented into intervals correspondingto individual persons crossing through the field of view. Experimentalresults are shown in cross-validated tests overreal sequences acquired by the camera.