Parametric characterization of ground surfaces with laser speckles

Area of Science:

• Optics
• Surface Metrology
• Materials Science

Background:

• Speckle measurement techniques are established for isotropic surfaces.
• Characterizing anisotropic surfaces using speckle remains a challenge.

Purpose of the Study:

• To develop and validate a speckle-based method for measuring unidirectionally anisotropic surfaces.
• To enable simultaneous determination of multiple surface parameters from a single measurement.

Main Methods:

• A novel measurement setup and evaluation algorithm were developed.
• Two-dimensional fast Fourier transform (FFT) was used for analyzing diffraction patterns.
• Bidirectional evaluation of speckle contrast was employed for roughness parameters.

Main Results:

• The method successfully determines machining direction and autocorrelation length perpendicular to it.
• Two root mean square roughness parameters (parallel and perpendicular to machining direction) are obtained.
• Measurements were validated on physical samples and simulated surfaces using a spatial light modulator.

Conclusions:

• The presented speckle-based technique offers a comprehensive approach for anisotropic surface characterization.
• This method provides efficient and accurate measurement of key surface parameters.
• The study quantifies measurement uncertainty, enhancing the reliability of the technique.