Abstract
The form, waviness and roughness components of a measured profile are
separated by means of digital filters. The aim of analysis was to develop
an algorithm for one-dimensional filtering of profiles using approximation
by means of B-splines. The theory of B-spline functions introduced by
Schoenberg and extended by Unser et al. was used. Unlike the spline filter
proposed by Krystek, which is described in ISO standards, the algorithm
does not take into account the bending energy of a filtered profile in the
functional whose minimization is the principle of the filter. Appropriate
smoothness of a filtered profile is achieved by selecting an appropriate
distance between nodes of the spline function. In this paper, we determine
the Fourier transforms of the filter impulse response at different impulse
positions, with respect to the nodes. We show that the filter cutoff
length is equal to half of the node-to-node distance. The inclination of
the filter frequency characteristic in the transition band can be adjusted
by selecting an appropriate degree of the B-spline function. The paper
includes examples of separation of 2D roughness, as well as separation of
form and waviness of roundness profiles.
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