White-light interferometry on rough surfaces--measurement uncertainty caused by noise
1Palacky University, Faculty of Science, Regional Centre of Advanced Technologies and Materials, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Science of the Czech Republic, Olomouc, Czech Republic. Pavel.Pavlicek@upol.cz
Applied Optics
|February 7, 2012
Summary
White-light interferometry measures object geometry using interferograms. Noise limits measurement accuracy, but the Cramer-Rao inequality helps calculate the minimum uncertainty, including shot noise effects.
Area of Science:
- Optical metrology
- Surface characterization
- Interferometry
Background:
- White-light interferometry is crucial for measuring the geometrical form of rough surfaces.
- Interferograms are analyzed to determine the longitudinal coordinate of measured surfaces.
- Measurement accuracy is compromised by noise inherent in interferograms.
Purpose of the Study:
- To determine the lower limit of longitudinal measurement uncertainty in white-light interferometry.
- To quantify the impact of noise on surface geometry measurements.
- To specifically analyze uncertainty contributions from shot noise.
Main Methods:
- Application of the Cramer-Rao inequality to interferometric data.
- Analysis of interferograms affected by various noise sources.
- Calculation of theoretical lower bounds for measurement uncertainty.
Main Results:
- The Cramer-Rao inequality provides a quantifiable lower limit for longitudinal measurement uncertainty.
- Noise significantly impacts the accuracy of geometrical form measurements.
- The study isolates and quantifies the uncertainty contribution from shot noise.
Conclusions:
- Understanding noise limitations is essential for accurate white-light interferometry.
- The Cramer-Rao inequality is a valuable tool for assessing measurement uncertainty.
- Minimizing shot noise is critical for improving the precision of surface geometry measurements.
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