Reference-plane-based fast pixel-by-pixel absolute phase retrieval for height measurement

Area of Science:

• Optics and Photonics
• Metrology
• Computer Vision

Background:

• Absolute phase retrieval is critical for accurate height measurement in digital fringe projection (DFP).
• Conventional phase unwrapping methods often require multiple structured light patterns, increasing system complexity.
• Existing techniques struggle with complex surfaces and limited depth ranges.

Purpose of the Study:

• To develop novel, simplified pixel-by-pixel absolute phase retrieval techniques for DFP.
• To reduce the number of projected patterns required for accurate height measurements.
• To enable absolute phase retrieval across diverse object depth ranges and surface discontinuities.

Main Methods:

• Proposed two reference-plane-based absolute phase retrieval techniques.
• Developed a single-frequency method for limited height ranges using one reference plane.
• Introduced a dual-frequency method with two reference planes for extended depth range and step-height surfaces.

Main Results:

• Demonstrated effective absolute phase retrieval with minimal projections.
• Achieved accurate height measurements for objects within defined height limits.
• Successfully extended measurement depth range and handled objects with step-height discontinuities.

Conclusions:

• The proposed techniques simplify absolute phase retrieval in DFP systems.
• These methods offer efficient and accurate height measurements for various object types and depths.
• The techniques are robust and suitable for real-world metrology applications.