An Areal Isotropic Spline Filter for Surface Metrology

Area of Science:

• Surface metrology
• Topography analysis
• Filter design

Background:

• Profile (2D) filters are often used as areal filters in 3D measurements.
• Spline filters exhibit undesirable anisotropic characteristics when applied areally, unlike Gaussian filters.
• This anisotropy limits the use of spline filters in surface topography evaluation.

Purpose of the Study:

• To develop an approximation method for creating an isotropic areal spline filter.
• To overcome the inherent anisotropy of spline filters in surface metrology.
• To enhance the applicability of spline filters for areal surface topography analysis.

Main Methods:

• Constructing a serial, high-order profile spline filter to mimic Gaussian filter characteristics.
• Composing an areal filter by applying the profile spline filter orthogonally.
• Approximating the filtering behavior of Gaussian filters using spline filter series.

Main Results:

• The developed areal filter demonstrates isotropic amplitude characteristics.
• The method effectively eliminates end effects, a common issue in areal filtering.
• The approximation successfully addresses the anisotropy disadvantage of spline filters.

Conclusions:

• The proposed method enables the creation of isotropic areal spline filters.
• This advancement expands the utility of spline filters in surface metrology.
• The technique provides a robust solution for analyzing areal surface topography.