Scanning moiré and phase shifting with time delay and integration imaging

Area of Science:

• Optical Metrology
• 3D Imaging and Profilometry
• Image Processing

Background:

• Scanning moiré patterns in projection profilometry represent height contours but suffer from undersampling.
• Phase-shifting interferometry is ideal for automated profile unwrapping but is hindered by spatial information loss in undersampled moiré fringes.
• Time Delay and Integration (TDI) imaging allows for on-line scanning moiré pattern generation from rotating objects.

Purpose of the Study:

• To address errors in phase unwrapping caused by spatial information loss in undersampled scanning moiré fringes.
• To present a method for accurate 3D profile reconstruction from scanning moiré data.
• To enhance the reliability of automated 3D profilometry using TDI imaging.

Main Methods:

• Generating on-line scanning moiré patterns from a rotating cylinder using TDI imaging.
• Implementing a data oversupply strategy to counteract the effects of undersampling.
• Utilizing programmable image magnification in the scanning direction via TDI features.

Main Results:

• The proposed method effectively balances the impact of undersampling by providing an oversupply of data.
• Accurate phase and profile unwrapping from scanning moiré fringes was achieved, mitigating previous errors.
• The TDI feature with magnification enabled robust 3D profile reconstruction from the entire periphery of a cylindrical object.

Conclusions:

• The TDI imaging technique with data oversupply offers a viable solution for accurate 3D scanning moiré profilometry.
• This approach overcomes the limitations of spatial information loss in undersampled moiré fringes, improving phase unwrapping.
• The method enhances the automation and precision of 3D contour mapping for cylindrical objects.