Fig. 1. Schematic of acquisition device

Fig. 2. Variations of SNR and DSNR with m. (a) Variation of SNR with m; (b) variation of DSNR with m

Fig. 3. Frequency spectrum of single S_i and reconstructed single at different principle frequency expansion coefficient (m) values. (a) Signal S_i; (b) frequency spectrum of single S_i (the frequency range of red, yellow and green lines is the main frequency domain when m=2); (c) reconstructed signal when m=0; (d) reconstructed signal when m=2

Fig. 4. Process of signal processing by multi-region dominant frequency enhancement (MRDFE) method. (a) A certain frame of neck image and selected ROI; (b) original grayscale signals of each ROI; (c) weighted signals of each ROI after filtering; (d) each component after principal component analysis

Fig. 5. Single period pulse wave and its characteristic points

Fig. 6. Measured pulse wave and its characteristic points

Fig. 7. Pulse wave signals obtained with different signal processing methods. (a) BF method; (b) BF+SSA method; (c) direct PCA method; (d) MRDFE method