Nonlinear phase error correction method based on multi-grayscale coding.

Area of Science:

• Optical Metrology
• 3D Imaging
• Computer Vision

Background:

• Fringe projection profilometry (FPP) is a key non-contact 3D measurement technique.
• Nonlinear intensity response of digital projectors degrades measurement accuracy.
• Increasing fringe projections enhances accuracy but reduces speed.

Purpose of the Study:

• Develop a method to simultaneously improve 3D measurement accuracy and speed.
• Address nonlinear intensity response errors in FPP.
• Reduce the number of required fringe projections.

Main Methods:

• Proposed a nonlinear phase error correction method using multi-grayscale coding.
• Fitted the system's intensity response curve using grayscale images.
• Corrected grayscale values of phase-shifting fringe images.
• Employed multi-grayscale coding to divide phase intervals by gray value order.

Main Results:

• Achieved accurate phase calculation with only seven images for single reconstruction.
• Nonlinear correction improved phase accuracy by 50.77% for the three-step phase-shifting algorithm.
• Reconstruction accuracy of a standard ball increased by 46.38%.

Conclusions:

• The multi-grayscale coding method effectively enhances both accuracy and speed in fringe projection profilometry.
• The proposed technique offers a significant improvement over traditional methods for 3D measurement.
• Validated efficacy through experimental results, demonstrating practical applicability.