Light depolarization in off-specular reflection on submicro rough metal surfaces with imperfectly random roughness

Abstract

Depolarization at a rough surface relates to its roughness and irregularity (e.g., sags and crests) besides the material property. However, there is still lack of general theory to clearly describe the relationship between depolarization ratios and surface conditions, and one important reason is that the mechanism of depolarization relates to geometric parameters such as microcosmic height/particle distributions of sub-micro to nm levels. To study the mechanism in more detail, a compact laser instrument is developed, and depolarization information of a linearly polarized incident light is used for analyzing the roughness, during which a He-Ne laser source (λ = 632.8 nm) is used. Three nickel specimens with RMS roughness (Rq) less than λ/4 are fabricated and tested. Six different areas in each specimen are characterized in detail using an AFM. Rq are in the range of 34.1-155.0 nm, and the heights are non-Gaussian distribution in the first specimen and near-Gaussian distribution in the others. Off-specular inspection is carried out exactly on these 18 characterized areas, and results show that the cross-polarization ratios match quite well with Rq values of the first sample that has Rq ≤ λ/10 (or Rt ≤ λ), while they match well with maximum height, Rt, values of the other two that have Rt > λ (the maximum derivation is 11%). In addition, since this instrument is simple, portable, stable, and low-cost, it has great potential for practical online roughness testing after a linear calibration.

Concealing a shiny facial skin appearance by an Aerogel‐based formula. In vitro and in vivo studies

“…our in vitro and in vivo experiments suggest a two-phase process with regard to time, post-application. The immediate effect obtained at higher concentrations of Aerogel (1% and 2%), and observed in vivo, suggests a rapid light scattering of the concerned surfaces (contrast plates or facial skin), that is a soft focus that rapidly 'clogs' (in vitro) or mitigate (in vivo) most of the reflective microstructures present at the surface, in agreement with previous works [4,8]. Such rapid light scattering is likely inherent to many particulate matters as Perlite shows a noticeable immediate anti-shine effect, however, a much lower amplitude than the one brought by Aerogel at 2%.…”

“…Measuring the reflective properties of a given surface is paramount in many and diverse applications (medical, industrial, photographic etc.) [6][7][8][9]. With regard to skin, reflection of light is additionally influenced by gender and age [4,5].…”

Distinguishing Drones from Birds in a UAV Searching Laser Scanner Based on Echo Depolarization Measurement

“…Identification of surface type, its microscopic or macroscopic parameters, based on reflected light polarization state measurements have been reported many times [30][31][32][33][34][35][36][37][38][39][40][41]. Most of the research in this field however deals with laboratory methods based on full Stokes vector and Mueller matrix analysis.…”

Cross-polarization ratio analysis of digital speckle patterns applied to teeth demineralization diagnosis

“…It is well known that when a rough surface scatters a linearly polarized laser beam, we can observe the effect known as the depolarization process. The degree of depolarization can be inferred by the amount of light intensity polarized in the cross direction of the incident polarization [10]. The parameter that can quantify the depolarization process is the CPR [10].…”

“…Application of depolarization studied for surface roughness measurement was proposed [8,9]. Liu et al introduced the cross-polarization ratio (CPR) in order to study the roughness of random surfaces [10]. Recently, a proposal using CPR was presented with potential application to measure surface roughness using direct intensity measurement [11].…”