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Non-contact heart rate and respiratory monitoring based on imaging photoplethysmography at fingertip

In this paper, we use imaging photoplethysmography (IPPG) to realize non-contact measurement of blood volume change of human fingertip, which can avoid distortion of blood vessel wall caused by pressure applied to fingertip. We use CMOS color camera to collect signals and white LED as light source. In the process of signal processing, we abandon the traditional morphological filtering algorithm in the form of double-layer cascade, and use single-layer morphological filtering algorithm. Experiments show that the single-layer morphological filtering algorithm has a good effect of eliminating baseline drift of signals, and can perfectly retain the detail components of signals without shifting the transverse components. We proposed a peak-to-valley value detection algorithm to calculate the heart rate by detecting the time interval between the adjacent peaks value. The experiment compared the accuracy of calculating the heart rate by using the traditional fast Fourier transform and the heart rate based on peak-to-valley value detection. The respiration rate was detected by using the third-order Butterworth filter. The accuracy of heart rate monitoring can be achieved at 97.86% and the accuracy of respiration monitoring can be achieved at 95.02%.