Flexible and accurate system calibration method in microscopic fringe projection profilometry

Area of Science:

• Optics
• Metrology
• Microscopy

Background:

• Accurate three-dimensional (3D) measurement of microstructures is crucial for precision manufacturing and inspection.
• Existing calibration methods like phase-height mapping (PHM) and stereo vision (SV) have limitations, including reliance on expensive equipment or difficulties in projector calibration.
• System calibration accuracy directly impacts the final 3D reconstruction quality.

Purpose of the Study:

• To develop a simplified and accurate 3D system calibration approach for microscopic fringe projection profilometry.
• To enable simultaneous calibration of projector, camera, and phase-to-3D coordinates relationship.
• To reduce reliance on complex or expensive calibration apparatus.

Main Methods:

• Established an optically coupled microscopic fringe projection system with a Scheimpflug pinhole projector and a bi-telecentric camera.
• Introduced a simplified 3D system calibration method combining phase modulation transfer and ray propagation.
• Utilized a single 2D target for simultaneous calibration of the projector, camera, and phase-to-3D coordinates.

Main Results:

• The proposed method allows for simultaneous calibration of all system components using only a 2D target.
• External projector parameters were calibrated, enabling determination of the target's complete poses.
• Direct mapping coefficients from phase to 3D coordinates were obtained through optical geometry and phase labels.
• Experimental comparisons confirmed the feasibility and accuracy of the developed method.

Conclusions:

• The simplified 3D system calibration method is effective for microscopic fringe projection profilometry.
• This approach offers a more accessible and accurate alternative to existing calibration techniques.
• The method enhances the reliability of 3D measurements for complex microstructures.