Taiwan currently faces an aging population and a rise in mortality rate caused by
cardiovascular disease. Therefore, the prevention of cardiovascular disease and the constant
tracking of physiological information are crucial. Photoplethysmography (PPG) is used to
instantaneously measure and monitor a person’s physiological information. Compared with
electrocardiography, PPG measurements are more convenient and less expensive. However, PPG
is more susceptible to the effects of motion artifacts. To accurately analyze the physiological
information contained in PPG signals, the negative effects of motion artifacts on PPG signals
must first be eliminated. In this study, independent component analysis was employed to
separate independent components (i.e., PPG signals and noise) from raw signals with motion
artifacts. Subsequently, independent components containing PPG signals were selected and the
locations of the PPG signal components in the frequency spectrum were analyzed. Next, the raw
signals were passed through a multi-bandpass filter specifically designed for this study to
eliminate motion artifacts. Motion artifacts were created for an experiment using two types of
finger movements: vertical and horizontal finger movements. From the independent component
analysis of the independent components, the waveforms of the filtered PPG signals in the time
and frequency domains were acquired, which were then compared with the results of heartbeat
measurement.
