Diffuse reflectivity of Tyvek in air and water, and anisotropical effects

Surface microstructure of water Cherenkov detectors reflective liner: Tyvek

“…The measurements were made for the wavelength λ = 488 nm and incidence angle θ i = 75°. Up to now, the influence of sample rotation on BRDF has been studied only by Velazquez et al 6,7 Figure 3. Optical anisotropic effects on the diffuse reflectivity of Tyvek 1056 (angle of incidence θ i = 75°) 6 .…”

“…Up to now, the influence of sample rotation on BRDF has been studied only by Velazquez et al 6,7 Figure 3. Optical anisotropic effects on the diffuse reflectivity of Tyvek 1056 (angle of incidence θ i = 75°) 6 . We used the professional complete angle scatter instrument (CASI) to study the anisotropic effect described by Velazquez et al Several BRDF measurements were performed using the scatterometer with the 633 nm laser source to check how the scatter profile is influenced by the sample rotation along its surface normal 8 .…”

“…Thus we can consider that surface anisotropy effect is not significant. Velazquez et al expected that anisotropic effect can be associated with the fibrous composition of the material and the presence of surface regions with preferential orientations of fibers 6,7 . We decided to study surface microstructure of Tyvek to explain described anisotropic effect.…”

“…Polarization was not taken into account. Conventional 2 mW He-Ne laser and 11 mW argon laser were used in Velazquez et al laboratory experimental setup of gonioreflectometer 6,7 . BRDF anisotropic effect was detected with argon laser (see Figure 3).…”

“…Figure 9. BRDF measurement setup of Velazquez et al 6,7 (left) and CASI instrument 8 (right). Figure 6 shows surface texture of Tyvek sample with dimensions comparable to the diameter of applied laser beam.…”