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Abstract: In this paper, a speckle interferometer with a plastic optical fiber system is reported for unobtrusive monitoring of heartbeat and respiration. The sensor consists of a laser diode butt-coupled to the plastic optical fiber, whose exit face projects speckle patterns onto a linear optical sensor array, which leads to a simple and cost-effective construction. Speckle images are acquired in a sequence and transformed into a 1D signal by using a phase-shifting method. Band-pass filtering and Morlet-wavelet-based multiresolutional approaches were used to analyze signals for the detection of cardiac and respiratory activities, respectively. Ten young, healthy persons participated in system testing, by lying supine on a mattress with embedded plastic optical fiber. Experimental results show the proposed system and detection algorithms are highly efficient. Sensitivities of 99.4 0.6% and 95.3 3%, precisions of 98.8 1.5% and 97.9 2.3%, and mean delays between interferometric detections and corresponding referential signals of 116.6 55.5ms and 1299.2 437.3 ms were computed for heartbeat and respiration, respectively.
Keywords: plastic optical fiber, speckle interferometry, unobtrusive monitoring, heartbeat detection, respiration detection, phase-shift method, wavelet transform
Published in DKUM: 10.07.2015; Views: 1243; Downloads: 16
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