Meaning
Computational algorithms that isolate or remove specific ranges of cycles per millimetre from topographical data represent this filter type. Standard use of a spatial frequency filter helps separate small-scale roughness from the larger errors in mould form. Quality reports rely on these settings to calculate values like Ra or Rz without being biased by the overall tilt of the part.
Changing the filter cutoff value shifts which features are counted as defects.
Noise Reduction
High-frequency spikes from sensor noise disappear when an appropriately tuned filter is applied to the raw scan. This smoothing allows for a clear view of the underlying surface finish produced by the tool. Processing steps must be documented to ensure consistent reporting across laboratories.
Feature Isolation
Metrologists use low-pass or band-pass filters to focus on specifically relevant features like tool marks. Measuring fine textures on micro-parts requires careful selection of the cutoff to avoid erasing real geometry. Unfiltered data is often too complex for meaningful pass or fail comparison.
Measurement Standard
Consistency follows from using the exact filters specified in standards like ISO 25178. Digital artifacts in the processed image occur if the filter window is poorly sized. Correct software application confirms that the reported roughness is a true reflection of the plastic surface.
