Fig. 1. Traditional microfacet scattering

Fig. 2. Geometric relationship of microfacet

Fig. 3. β orientation diagram

Fig. 4. Reflective azimuth replacement diagram

Fig. 5. Monte Carlo simulation flowchart

Fig. 6. θm Sampling plot

Fig. 7. Transmission model

Fig. 8. Photon distribution at different incident angles

Fig. 9. Photon distribution with different roughness

Fig. 10. Relationship between incidence angles and photon numbers

Fig. 11. Relationship between roughness and photon numbers

Fig. 12. Design of non-contact detection system

Fig. 13. Responsivity versus wavelength

Fig. 14. Experimental results of non-contact road condition detection system

Fig. 15. Relationship between roughness and signal-to-noise ratio under different incident angles