2 October 2008 Method of objects detection employing passive IR detectors for security systems
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Abstract
PIR detectors used in security systems for people detection operate in far IR range (8÷14) mm. These detectors most frequently employ pyroelectric sensors. Application of a single pyroelectric sensor does not ensure distinguishing the phenomena of alarm character from, so-called, false alarms caused by, e.g., air turbulences or changes in a background temperature resulting from sun radiation. Thus, in PIR detectors, the sensors with two active elements are used (two sensors) and an alarm signal is determined on the basis of analysis of a difference (or a sum) and their output signals. Essential drawback of currently available PIR detectors is low efficiency of detection of slowly moving or crawling people. Efficiency of detection of slowly moving objects is low because radiation from such objects is close to background thermal noises. The presented signal analysis is based on determination of average moving value in three "time windows" of a defined wavelength. Moreover, a principle of "time windows" creation is given and an algorithm for determination of detection thresholds is described. In PIR detector, an adaptation detection threshold was taken following thermal changes of a background. Influence of sun radiation is taken into account in the algorithm of determination of adaptation detection threshold.
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Tomasz Sosnowski, Tomasz Sosnowski, Henryk Madura, Henryk Madura, Mariusz Kastek, Mariusz Kastek, Tadeusz Piątkowski, Tadeusz Piątkowski, Edward Powiada, Edward Powiada, } "Method of objects detection employing passive IR detectors for security systems", Proc. SPIE 7113, Electro-Optical and Infrared Systems: Technology and Applications V, 71131G (2 October 2008); doi: 10.1117/12.800147; https://doi.org/10.1117/12.800147
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