DOI QR코드

DOI QR Code

Assessing the Refractive Index of Glass Beads for Use in Road-marking Applications via Retroreflectance Measurement

  • Shin, Sang Yeol (Department of Materials Science and Engineering, Korea Aerospace University) ;
  • Lee, Ji In (Department of Materials Science and Engineering, Korea Aerospace University) ;
  • Chung, Woon Jin (Division of Advanced Materials Engineering, Kongju National University) ;
  • Cho, Sung-Hoon (E-Hwa Industrial Co. Ltd.) ;
  • Choi, Yong Gyu (Department of Materials Science and Engineering, Korea Aerospace University)
  • Received : 2019.06.18
  • Accepted : 2019.08.20
  • Published : 2019.10.25

Abstract

Retroreflection of vehicle headlights, as induced by spherical glass beads, is a key optical phenomenon that provides road-surface markings with greatly enhanced visibility, thus better securing a driver's safety in the nighttime as well as in unclear daytime. Retroreflectance of glass beads is a quite sensitive function of their refractive index, so that measurement of the refractive index of glass specifically in the shape of spherical beads needs to be performed within a reasonable uncertainty that is tolerable for road-marking applications. The Becke line method has been applied in assessing refractive index of such glass beads as e.g. an industrial standard in the Republic of Korea; however, the reference refractive-index liquids are not commercially available these days for refractive index greater than 1.80 due to the toxicity of the constituent materials. As such, high-refractive-index glass beads require an alternate method, and in this regard we propose a practically serviceable technique with uncertainty tantamount to that of the Becke line method: Based on comparison of calculated and measured retroreflectance values of commercial glass beads, we discover that their refractive index can be determined with reasonable precision via the retroreflectance measurement. Specifically, in this study the normalized retroreflectance originating from a single glass sphere is computed as a function of refractive index using the Fresnel equations, which is then validated as coinciding well with retroreflectance values measured from actual specimens, i.e. glass-bead aggregates. The uncertainties involved are delineated in connection with radius and imperfections of the glass beads.

Keywords

Glass beads;Road surface marking;Refractive index;Retroreflection;Fresnel equations

Acknowledgement

Supported by : Ministry of Trade, Industry and Energy of Korea

References

  1. L. A. Ivanov, D. V. Kiesewetter, N. N. Kiselev, V. I. Malyugin, and V. A. Slugin, "Measurement of retroreflection by glass beads for road marking," Proc. SPIE 6251, 62510U (2006).
  2. T. Grosges, "Retro-reflection of glass beads for traffic road stripe paints," Opt. Mater. 30, 1549-1554 (2008). https://doi.org/10.1016/j.optmat.2007.09.010
  3. J. T. Lee, T. L. Maleck, and W. C. Taylor, "Pavement marking material evaluation study in Michigan," ITE J. Inst. Transp. Eng. 69, 44-51 (1999).
  4. T. Schnell, F. Aktan, and Y. C. Lee, "Nighttime visibility and retroreflectance of pavement markings in dry, wet, and rainy conditions," Transp. Res. Rec. 1824, 144-155 (2003). https://doi.org/10.3141/1824-16
  5. D. M. Burns, T. P. Hedblom, and T. W. Miller, "Modern pavement marking systems: Relationship between optics and nighttime visibility," Transp. Res. Rec. 2056, 43-51 (2008). https://doi.org/10.3141/2056-06
  6. H. Fuquan, L. Shangying, and W. Shaomin, "The refractive index measurement of high refractive index glass beads," Acta Photon. Sin. 30, 753-756 (2001).
  7. F. Sarcinelli, R. Pizzoferrato, and F. Scudieri, "Study of the refractive index of microscopic glass beads by light-refraction analysis," Appl. Opt. 36, 8999-9004 (1997). https://doi.org/10.1364/AO.36.008999
  8. J. L. Hand and S. M. Kreidenweis, "A new method for retrieving particle refractive index and effective density from aerosol size distribution data," Aerosol. Sci. Technol. 36, 1012-1026 (2002). https://doi.org/10.1080/02786820290092276
  9. A. Leblance-Hotte, R. St-Gelais, and Y.-A. Peter, "Optofluidic device for high resolution volume refractive index measurement of single cell," in Proc. 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences (Japan, Oct. 2012), pp. 1330-1332.
  10. T. Yamaguchi, "Refractive index measurement of high refractive index glass beads," Appl. Opt. 14, 1111-1115 (1975). https://doi.org/10.1364/AO.14.001111
  11. R. W. Spinrad and J. F. Brown, "Relative real refractive index of marine microorganisms: a technique for flow cytometric estimation," Appl. Opt. 25, 1930-1934 (1986). https://doi.org/10.1364/AO.25.001930
  12. S.-Y. Li, S. Qin, D.-H. Li, and Q.-H. Wang, "Using a laser source to measure the refractive index of glass beads and Debye theory analysis," Appl. Opt. 54, 9688-9694 (2015). https://doi.org/10.1364/AO.54.009688
  13. Glass beads for traffic paint, KS L 2521, Korean Standard Association, Seoul (2017).
  14. Standard test method for measurement of retroreflective signs using a portable retroreflectometer at a 0.2 degree observation angle, ASTM E1709-16e1, ASTM International, Pennsylvania (2016).
  15. Standard test method for measurement of retroreflective signs using a portable retroreflectometer at a 0.5 degree observation angle, ASTM E2540-16, ASTM International, Pennsylvania (2016).
  16. M. D. Stoudt and K. Vedam, "Retroreflection from spherical glass beads in highway pavement markings. 1: Specular reflection," Appl. Opt. 17, 1855-1858 (1978). https://doi.org/10.1364/AO.17.001855
  17. E. Hecht, Optics, 4th ed. (Addison-Wesley, New York, 2002), Chapter 4.
  18. G. Zhang, J. E. Hummer, and W. Rasdorf, "Impact of bead density on paint pavement marking retroreflectivity," Transp. Eng. J. ASCE 136, 773-781 (2010). https://doi.org/10.1061/(ASCE)TE.1943-5436.0000142
  19. K. Vedam and M. D. Stoudt, "Retroreflection from spherical glass beads in highway pavement markings. 2: Diffuse reflection (a first approximation calculation)," Appl. Opt. 17, 1859-1869 (1978). https://doi.org/10.1364/AO.17.001859
  20. D. Hericz, T. Sarkadi, G. Erdei, T. Lazuech, S. Lenk, and P. Koppa, "Simulation of small- and wide-angle scattering properties of glass-bead retroreflectors," Appl. Opt. 56, 3969-3976 (2017). https://doi.org/10.1364/AO.56.003969
  21. N. M. Ravindra, P. Ganapathy, and J. Choi, "Energy gaprefractive index relations in semiconductors-An overview," Infrared Phys. Technol. 50, 21-29 (2007). https://doi.org/10.1016/j.infrared.2006.04.001
  22. S. Y. Shin, B.-K. Cheong, and Y. G. Choi, "Local structural environments of Ge doped in eutectic Sb-Te film before and after crystallization," J. Phys. Chem. Solids 117, 81-85 (2018). https://doi.org/10.1016/j.jpcs.2018.02.021
  23. S. Y. Shin, J. I. Lee, W. J. Chung, and Y. G. Choi, "Correlations between refractive index and retroreflectance of glass beads for use in road-marking applications under wet conditions," Curr. Opt. Photon. 3, 423-428 (2019).