Surveillance is becoming more and more important in the recent years. In many cities, cameras have been set to look after parks, streets, roads, facilities and so on, however this fact is rising concerns about privacy. In this work, an alternative surveillance method which gather at once security and privacy has been propose and tested. Based on fiber optic specklegram technology; a system consisting of a fiber optic, a coherent light source and a photodetector has been placed under a carpet for detecting people walking over it and its accuracy, regarding measuring the steps, have been measured. Results suggest that using low exposed geometries along the carpet and basic processing methods, it is possible to detect with more than 95% of accuracy the number of steps done by the person walking over the carpet.
Different low-cost approaches based on fiber specklegram sensors are employed to measure the physiological activity of patients lying in bed. This study is conducted over 20 volunteers to measure the movement and heart rate (HR) using two different sensor designs placed at two different bed locations. Three different processing methods are developed and tested in order to extract useful information from the measured data. The results suggest that a stretched fiber optic configuration under the head of the person lying in bed is the optimal configuration to detect HR and motion, nonetheless the other tested possibilities also exhibit remarkably good performances. On the other hand, the three proposed processing methods also achieve a good precision in the HR detection. The sensor implementation is simple, not requiring any special conditions, and it provides robust performance. This leads to the conclusion that fiber specklegram technology is a feasible method to be used in real situations for heartbeat and movement monitoring.
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