Autofocusing method for a digital fringe projection system with dual projectors

Area of Science:

• Optics and Photonics
• Computer Vision
• Metrology

Background:

• 3D profilometry systems often require manual focus adjustment, limiting their efficiency and applicability.
• Dynamic focusing is crucial for accurate 3D reconstruction, especially with varying object depths.
• Existing autofocusing methods may not be suitable for dual-projector 3D profilometry setups.

Purpose of the Study:

• To develop and validate a novel autofocusing technique for a dual-projector 3D profilometry system.
• To enable dynamic focal plane adjustment for precise 3D shape measurement.
• To automate the focusing process within a specific object distance range.

Main Methods:

• Utilizing a camera equipped with an electronically focus-tunable lens (ETL) for dynamic focal plane control.
• Employing dual pre-calibrated projectors to project fringe patterns for triangulation-based 3D reconstruction.
• Pre-calibrating the depth-to-current relationship for each focal plane and calculating optimal current values based on initial 3D results.

Main Results:

• Demonstrated successful autofocusing for 3D profilometry with a dual-projector system.
• Developed a prototype system capable of automatically focusing on objects between 450 mm and 850 mm.
• Achieved accurate 3D shape measurements through dynamic focal adjustments.

Conclusions:

• The proposed autofocusing technique effectively enhances the performance of dual-projector 3D profilometry systems.
• The ETL-based system offers automated and precise 3D measurements across a practical working distance.
• This advancement has potential applications in various fields requiring rapid and accurate 3D surface analysis.