Improved white-light interferometry on rough surfaces by statistically independent speckle patterns.
Bernhard Wiesner1, Ondrej Hybl, Gerd Häusler
1Institute of Optics, Information and Photonics, University of Erlangen–Nuremberg, Staudtstrasse 7/B2, 91058 Erlangen, Germany.
Applied Optics
|February 24, 2012
Summary
This study introduces a new white-light interferometry (WLI) method for rough surfaces. By analyzing sequential speckle patterns, it significantly reduces measurement uncertainty for accurate surface roughness analysis.
Area of Science:
- Optical Metrology
- Surface Characterization
- Interferometry
Background:
- White-light interferometry (WLI) is crucial for surface profiling.
- Measurement uncertainty in WLI is often limited by speckle pattern shifts and variations in speckle brightness.
- Darker speckles introduce greater statistical error in height measurements.
Purpose of the Study:
- To develop a novel method for significantly reducing measurement uncertainty in WLI for rough surfaces.
- To improve the accuracy of height map generation and surface roughness measurements using WLI.
Main Methods:
- Sequential switching of illumination direction to capture multiple independent speckle patterns.
- Selection of the brightest speckles from each sequential pattern.
- Calculation of an accurate height map based on the selected bright speckles.
Main Results:
- The novel method significantly reduces measurement uncertainty in WLI.
- Generated height maps exhibit no outliers, improving data quality.
- Measured surface roughness values closely correlate with stylus profilometry measurements.
Conclusions:
- The proposed WLI technique effectively mitigates errors caused by speckle variations.
- This method provides a more robust and accurate approach to surface roughness characterization.
- The technique offers improved performance for WLI applications on rough surfaces.
