Illustration of noncontact dual wavelength PPG system, depicting illumination and imaging geometry, relative timing of events (upper inset), and arrangement of LED array (lower inset).
Signal acquisition and image processing.
Illustration of illumination and imaging positions (A) and sample frame from the sequence (B). The white box encloses an area of —the time varying mean value of which is plotted in Fig. 4.
Comparison of noncontact PPG signals and conventional PPG signal.
Comparison of Fourier spectra of noncontact and conventional PPG signals.
Scatter plot showing noncontact device’s measurement of heart rate at (circles) and (crosses), vs the contact device’s measurement, for each subject. Also shown is the line , where both devices are in perfect agreement about the measurement.
Bland-Altman (mean vs difference) plot, showing the average of the heart rate measurements by the contact and noncontact devices, vs the difference between their measurements, for each subject. (The circles indicate measurement at , and the crosses at .) Also plotted are lines indicating the mean of the differences and standard deviations about the mean.
Simulated percentage error in measurement of by integrative sampling (camera based) compared to sample-and-hold (contact method). Results pertain to a synthetic contact signal sampled at sample-and-hold method and the camera derived version of that signal at .
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