@article{10584,
  abstract     = {Electrically tunable lenses (ETLs) are those with the ability to alter their optical power in response to an electric signal. This feature allows such systems to not only image the areas of interest but also obtain spatial depth perception (depth of field, DOF). The aim of the present study was to develop an ETL-based imaging system for quantitative surface analysis. Firstly, the system was calibrated to achieve high depth resolution, warranting the accurate measurement of the depth and to account for and correct any influences from external factors on the ETL. This was completed using the Tenengrad operator which effectively identified the plane of best focus as demonstrated by the linear relationship between the control current applied to the ETL and the height at which the optical system focuses. The system was then employed to measure amplitude, spatial, hybrid, and volume surface texture parameters of a model material (pharmaceutical dosage form) which were validated against the parameters obtained using a previously validated surface texture analysis technique, optical profilometry. There were no statistically significant differences between the surface texture parameters measured by the techniques, highlighting the potential application of ETL-based imaging systems as an easily adaptable and low-cost alternative surface texture analysis technique to conventional microscopy techniques},
  author       = {Nirwan, Jorabar Singh and Lou, Shan and Hussain, Saqib and Nauman, Muhammad and Hussain, Tariq and Conway, Barbara R. and Ghori, Muhammad Usman},
  issn         = {2072-666X},
  journal      = {Micromachines},
  keywords     = {surface texture, electrically tunable lens, materials, hypromellose, surface topography, surface roughness, pharmaceutical tablet, variable focus imaging},
  number       = {1},
  publisher    = {MDPI},
  title        = {{Electrically tunable lens (ETL) - based variable focus imaging system for parametric surface texture analysis of materials}},
  doi          = {10.3390/mi13010017},
  volume       = {13},
  year         = {2022},
}

@article{21516,
  abstract     = {The notion of elliptic or ellipsoidal conformal equivalent structure is introduced to model rough surface topography by use of convex homogenized shapes. The method is based on classical stereological results dealing with the relation between the number of intersections of an object with a set of parallel straight lines. The approach leads to an algorithm comparing the number of intercepts on both sampled surfaces and homogenized shapes selected for modeling. Some applications using the comparative values of the parameters of the homogenized structures are presented in this paper.},
  author       = {Roques-Carmes, Charles and Bodin, N. and Monteil, G. and Quiniou, J.F.},
  issn         = {1873-2577},
  journal      = {Wear},
  keywords     = {Rough surface topography, Stereology, Algorithm, Equivalent structure concept},
  number       = {1-2},
  pages        = {82--91},
  publisher    = {Elsevier},
  title        = {{Description of rough surfaces using conformal equivalent structure concept: Part 1. Stereological approach}},
  doi          = {10.1016/s0043-1648(00)00562-7},
  volume       = {248},
  year         = {2001},
}

@article{21517,
  abstract     = {In our new approach, the notion of conformal equivalent structure is introduced by comparing the slope or gradient distributions of surface topography in 2D or 3D mode, respectively. The stereological approach described in Section 2 is, thus, confirmed by the numerical one which is proposed in this paper. The approach emphasizes the viability of the modeling and the limits observed in some practical applications of the study of rough surfaces via different approximation methods. The few divergences which have been noticed may be explained by the introduction of parameters such as skewness and kurtosis.},
  author       = {Roques-Carmes, Charles and Bodin, N. and Monteil, G. and Quiniou, J.F.},
  issn         = {1873-2577},
  journal      = {Wear},
  keywords     = {Rough surface topography, Equivalent structure concept},
  number       = {1-2},
  pages        = {92--99},
  publisher    = {Elsevier},
  title        = {{Description of rough surfaces using conformal equivalent structure concept: Part 2. Numerical approach}},
  doi          = {10.1016/s0043-1648(00)00563-9},
  volume       = {248},
  year         = {2001},
}