Integrated, Speckle-Based Displacement Measurement for Lateral Scanning White Light Interferometry.

Area of Science:

• Metrology
• Optical Measurement Techniques
• Surface Science

Background:

• Lateral scanning white light interferometry (LSWLI) enables high-resolution topography measurements on dynamic surfaces.
• Precise lateral displacement data is critical for achieving the resolution capabilities of LSWLI.
• The impact of displacement uncertainty on topography measurement accuracy remains an open question.

Purpose of the Study:

• To quantify the influence of displacement uncertainty on LSWLI topography measurements.
• To propose and validate an integrated digital speckle correlation (DSC) method for precise displacement measurement within LSWLI.
• To assess the benefits of integrated DSC for LSWLI on moving objects.

Main Methods:

• Monte Carlo simulations were performed to analyze the effect of displacement uncertainty on LSWLI.
• Digital speckle correlation (DSC) was integrated into the LSWLI field of view for simultaneous displacement measurement.
• An experimental LSWLI setup with integrated DSC was tested on a rotating cylindrical object with a linear encoder strip surface.

Main Results:

• Monte Carlo simulations revealed that displacement uncertainty significantly impacts total height uncertainty more than motion uncertainty.
• Integrated DSC provided precise, synchronized, and calibrated displacement measurements without external systems.
• The integrated LSWLI-DSC system successfully performed topography measurements on a rotating surface.

Conclusions:

• Displacement measurement accuracy is a critical factor in LSWLI performance.
• Integrating DSC into LSWLI offers a robust solution for accurate topography measurements on moving surfaces.
• The proposed method eliminates the need for external synchronization and calibration, enhancing applicability for translatory and rotatory scans.