Fig. 1. Modeling of LED light source. (a) Mechanical structure; (b) spectral measurement result; (c) distribution of intensity; (d) distribution of irradiance

Fig. 2. Modeling of PD detector. (a) Mechanical structure; (b) spectral response curve; (c) angular response curve; (d) spectral-angular response contour

Fig. 3. Schematic diagram of skin tissue stratification modeling

Fig. 4. Schematic diagram of light propagation and absorption in skin tissues

Fig. 5. Schematic diagrams of the layout for each channel module. (a) Single-channel; (b) dual-channel; (c) four-channel; (d) eight-channel

Fig. 6. Schematic diagram of the center distance for the module

Fig. 7. Schematic diagrams of the window structures for the module. (a) Distributed window; (b) integrated window

Fig. 8. Schematic diagrams of light leakage paths. (a) Distributed window; (b) integrated window

Fig. 9. Schematic diagrams of the optical propagation paths for the blood oxygen module

Fig. 10. Simulated results under different distances for light source-detector

Fig. 11. Variation in luminous flux with distance for light source-detector

Fig. 12. Comparison of the total flux and average flux for modules with different channels at different detection distances. (a) Total flux; (b) average flux

Fig. 13. Comparison of detector detection efficiencies at different positions. (a) Detector grouping at each location; (b) comparison of detection efficiencies between detector groups

Fig. 14. Comparison of illuminance for modules with different channels. (a) Single-channel; (b) dual-channel; (c) four-channel; (d) eight-channel

Fig. 15. Schematic diagrams of light propagations in the tilted state of module

Fig. 16. Major construction features of Fresnel lens

Fig. 17. Distributions of spatial light modulated by different constant-angle Fresnel lenses. (a) 0°; (b) 10°; (c) 20°; (d) 30°; (e) 40°; (f) 50°; (g) 60°; (h) 70°; (i) 80°

Fig. 18. Major construction features of variable-angle Fresnel lens

Fig. 19. Distributions of spatial light modulated by variable-angle Fresnel lenses with different focals. (a) Planar window; (b) 100.0 mm; (c) 50.0 mm; (d) 30.0 mm; (e) 25.0 mm; (f) 20.0 mm; (g) 15.0 mm; (h) 10.0 mm; (i) 7.5 mm

Fig. 20. Illuminance of modules with different channels modulated by a variable-angle Fresnel lens. (a) Single-channel; (b) dual-channel; (c) four-channel; (d) eight-channel

Fig. 21. Comparison of the illumination uniformities and luminous fluxes of modules with different channels modulated by Fresnel lens or planar window