Surface and Form Metrology Group,

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Recent Advances in Separation of Roughness,
Waviness Form
Jay Raja Bala Muralikrishnan Shengyu Fu Xiangyang
Liu Center for Precision MetrologyUniversity of
North Carolina at CharlotteCharlotte, NC 28223
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Outline

• Introduction
• Historical Perspective
• 2RC
• Phase Correct
• Gaussian
• Bandwidth Filters
• Gaussian Bandpass
• Filter Banks
• Wavelets
• Recent Advances
• Spline Filters
• Robust Gaussian
• Morphological Filters
• Conclusion

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Constituents of Surface Texture
From ASME B46
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Historical Surface Metrology Measurement Spectrum
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Current Metrology Measurement spectrum
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Surface Texture Measurement and Characterization

• Profile Measurement
• Preprocessing
• Filtering
• Numerical Evaluation
• - Roughness Ra
• - Waviness Wa
• - Profile Pa

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Historical Perspective

• Graphical Evaluation
• 2RC Filters
• Transmission Characteristics
• Phase Characteristics

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Graphical Evaluation
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2RC Filter Transmission Characteristics
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2RC Filter - Phase Characteristics
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2RC Filter - Effect of Various Cutoffs
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Issues that Needed to be Addressed

• Phase Characteristics
• Bandwidths
• Special Cases - Plateau Honed Surfaces

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Filtering of Surface Profiles - Present

• Phase Correct Filter
• Gaussian Filter
• Valley Suppression Filter

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Phase Correct Filters
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Phase Correct Filters
Source Whitehouse, An improved type of
wavefilter for use in surface-finish
measurement, Procn Instn Mech Engr 1967-68
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FIR and IIR Filters
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Gaussian Filter
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Gaussian Filter - Transmission Characteristics
(?c and ?s)
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Separation of Roughness, Waviness and Form
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Example
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RK Filter ( DIN 4776)
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Comparison of 2RC, Gaussian and RK filters on
Plateau Honed surface
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Issues that Needs to be Addressed

• Bandwidths
• Multiscale nature of surfaces
• Wavelets
• Filtering effects in form removal
• Modified Gaussian
• Splines

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Bandwidth Filter

• Multi-Band Filters
• Filter Banks
• Multi-Resolution Filtering - Wavelet Transform

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Bandpass Filter - Gaussian Bandpass Filter

• Characteristics

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Bandpass Filter - Gaussian Bandpass Filter

• Example

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Bandpass Filter - Gaussian Bandpass Filter

• Example (continued)

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Gaussian Bandpass Filter

• Gaussian bandpass filter is suitable for
  analyzing the profiles with widely separated
  wavelength component
• Cutoff values

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Filter Bank - Uniform and Non-uniform

• Uniform filter bank
• Non-uniform filter bank Octave filter bank

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Multi-Resolution Filtering

• Analyze surface signals according to scale
• large window for gross features
• small window for fine features
• Multiresolution filtering based on wavelet
  analysis
• Wavelet an octave filter bank

Microscope
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Fourier, Short-time Fourier and Wavelet Transform
(continued)
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Fourier, Short-time Fourier and Wavelet Transform
(continued)
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Example of Wavelets
Scaling Functions Wavelets
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Multiresolution Analysis
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Wavelet Selection Daubechies
Most popular
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Wavelet Selection Daubechies - (continued)
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MULTIRESOLUTION ANALYSISGeneral Approach
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General Approach (continued)
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General Approach (continued)
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General Approach (continued)
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Surface Feature Extraction
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Surface Feature Extraction - (End effect
truncated)
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Special Filters

• Modified Gaussian
• Splines
• Morphological Filter

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Modified Gaussian Filter --Transmission
Characteristics
Advantage Mean line hugs texture
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Comparison with Gaussian
Black Modified Gaussian mean line Red
Gaussian mean line
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Non-periodic Spline Filter

• Filter equation

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Transmission Characteristics
Advantage No end effects
Low-pass transmission characteristics(
)
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Comparison with Gaussian
Black Spline mean line Red Gaussian mean line
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Comparison of Current Filters
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Morphological Filters ISO /TC 213 /AG 9 N51
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Wavelength Domain and Process Control
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Wavelength Domain and Functional Performance
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Conclusion

• Bandwidth Filtering for Process Diagnostics
  Functional Correlation
• Multi-resolution Filtering
• Special purpose Wavelets for Surface Profiles
• Morphological operations and Filters

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