Holistic form reconstruction based on a nonlinear 3D zonal grid model in stereoscopic deflectrometry

Area of Science:

• Optical Metrology
• Surface Metrology
• Computational Imaging

Background:

• Phase measuring deflectrometry (PMD) is crucial for specular surface measurement.
• Stereo-PMD addresses height-slope ambiguity but suffers from error propagation during stepwise reconstruction.
• Traditional zonal methods with 2D grids struggle with irregular slope data.

Purpose of the Study:

• To develop a novel nonlinear 3D grid model for stereo-PMD.
• To overcome limitations of stepwise reconstruction and irregular sampling in surface metrology.
• To enhance accuracy and noise robustness in specular surface measurement.

Main Methods:

• Proposed a nonlinear 3D grid model for stereo-PMD, replacing relative height with absolute height.
• Implemented a reconstruction method involving two nonlinear optimizations.
• Utilized stereo-PMD data with the new nonlinear 3D grid model.

Main Results:

• The nonlinear 3D grid model significantly shortens the error propagation chain.
• The method effectively handles irregular slope sampling data.
• Demonstrated enhanced low-order accuracy and improved noise robustness compared to traditional methods.

Conclusions:

• The proposed nonlinear 3D grid model offers a superior approach for stereo-PMD surface reconstruction.
• This method overcomes key limitations of existing techniques, particularly error accumulation and irregular data handling.
• The findings suggest a significant advancement in specular surface metrology.