Dual-sensitivity profilometry with defocused projection of binary fringes

Area of Science:

• Optical Metrology
• 3D Surface Profilometry
• Image Processing

Background:

• Traditional profilometry techniques often require complex calibration and struggle with discontinuous surfaces.
• Projector defocusing is a method to generate sinusoidal fringes from binary patterns, but its application in dual-sensitivity profilometry needs optimization.
• Nonlinear gamma calibration of projectors can be cumbersome and introduce errors.

Purpose of the Study:

• To present a dual-sensitivity profilometry technique using defocused projection of binary fringes.
• To enable accurate 3D surface reconstruction of discontinuous surfaces.
• To simplify the fringe generation process by eliminating the need for projector gamma calibration.

Main Methods:

• Generating two sets of sinusoidal fringe patterns (high- and low-frequency) by applying a single analog low-pass filter (projector defocusing) to binary fringes.
• Utilizing high-frequency fringes for high-quality wrapped phase maps and low-frequency fringes for nonwrapped phase maps.
• Employing error-diffusion dithering for low-frequency binary fringe generation.

Main Results:

• Achieved high-quality wrapped phase maps using high-frequency carrier fringes.
• Obtained lower-quality, nonwrapped phase maps with low-frequency carrier fringes.
• Demonstrated the utility of the nonwrapped phase map as a stepping stone for dual-sensitivity temporal phase unwrapping.

Conclusions:

• The proposed dual-sensitivity profilometry technique effectively measures discontinuous surfaces.
• A single defocusing level allows for faster acquisition of both high- and low-frequency fringe data.
• The binary nature of fringes eliminates the need for projector gamma calibration, simplifying the process.