Light scattering of semitransparent sintered polytetrafluoroethylene films

Qinghe Li, Bong Jae Lee, Zhuomin M. Zhang, David W. Allen
2008 Journal of Biomedical Optics  
Polytetrafluoroethylene ͑PTFE͒ is a strongly scattering material and has been regarded to have optical properties similar to biological tissues. In the present study, the bidirectional reflectance distribution function ͑BRDF͒ and the bidirectional transmittance distribution function ͑BTDF͒ of several PTFE films, with thicknesses from 0.11 to 10 mm, are measured using a laser scatterometer at the wavelength of 635 nm. The directional-hemispherical reflectance ͑R͒ and transmittance ͑T͒ were
more » ... ance ͑T͒ were obtained by integrating BRDF and BTDF for normal incidence. Comparison of the ratio of the measured R and T with that calculated from the adding-doubling method allows the determination of the reduced scattering coefficient. Furthermore, the effect of surface scattering is investigated by measuring the polarization-dependent BRDF and BTDF at oblique incidence. By analyzing the measurement uncertainty of BTDF in the near-normal observation angles at normal incidence, the present authors found that the scattering coefficient of PTFE should exceed 1200 cm −1 , which is much greater than that of biological tissues. On the other hand, the absorption coefficient of PTFE must be less than 0.01 cm −1 , much smaller than that of biological tissues, a necessary condition to achieve R ജ 0.98 with a 10-mm-thick slab.
doi:10.1117/1.2992485 pmid:19021442 fatcat:nzhlfp7upvdtdjj2smvylgjf4m