Fig. 1. PPG technology. (a) Transmission model of PPG technology; (b) reflection model of PPG technology

Fig. 2. Reflection model of IPPG technology

Fig. 3. Blood composition and light penetration depth^[20]. (a) Absorption of red, green and blue light by hemoglobin; (b) penetration depths of red, green and blue light in the skin; (c) modulation amplitudes of red, green and blue channels

Fig. 4. Origin of IPPG waveform^[13]

Fig. 5. Flow chart of physiological parameter acquisition of IPPG technology

Fig. 6. Measurement results of AZIPPG motion experiment^[63]. (a) Comparison of pulse wave signals; (b) Pearson correlation coefficient; (c) Bland-Altman analysis

Fig. 7. SPASD results^[74]. (a) Original live skin. (b) superpixel segmentation map of the live skin; (c) test result of live skin; (d) original skin model; (e) superpixel segmentation map of the skin model; (f) test result of skin model

Fig. 8. Comparison of the R measured by noncontact device proposed and the SPO2 measured by contact device versus time^［89］

Fig. 9. Interface diagram of non-contact fatigue driving detection system

Fig. 10. IPPG signal waveform characteristics of patients with different diseases^[133]. (a) IPPG signal characteristics in patients with atrial fibrillation related heart disease; (b) IPPG signal characteristics in patients with diabetes mellitus