Photorefractive moiré-like patterns for the multifringe projection method in Fourier transform profilometry

Area of Science:

• Optics
• Holography
• 3D Metrology

Background:

• Fourier transform profilometry (FTP) is a key technique for 3D surface measurement.
• Traditional FTP methods often face limitations in capturing complex object geometries.
• Developing advanced fringe projection techniques is crucial for improving measurement accuracy and efficiency.

Purpose of the Study:

• To describe a new method for simultaneous moiré-like fringe pattern projection for Fourier transform profilometry.
• To demonstrate the generation of controlled moiré-like patterns with multiple variation directions.
• To present the 2D fringe projection stage for a proposed 3D object profilometry procedure.

Main Methods:

• Utilizing a photorefractive holographic interferometric process.
• Superposing high spatial frequency sinusoidal gratings with slightly different pitches to create low spatial frequency fringe patterns.
• Employing a photorefractive Bismuth Titanate (Bi₁₂TiO₂₀ or BTO) crystal as a dynamic holographic medium to induce optical holographic beating.
• Projecting two or more moiré-like fringe patterns with at least two different variation directions onto the object surface.

Main Results:

• Successfully generated controlled moiré-like fringe patterns with multiple variation directions.
• Demonstrated the dynamic induction of these patterns via holographic beating within the BTO crystal.
• Established the 2D fringe projection stage for a comprehensive 3D profilometry approach.

Conclusions:

• The proposed method enables simultaneous projection of multiple moiré-like fringe patterns.
• This technique is a significant advancement in the fringe projection stage of Fourier transform profilometry.
• The method holds potential for accurate 3D surface profiling of simple objects.