Holographic detection for fast fringe projection profilometry of deep micro-scale objects

Area of Science:

• Optical Metrology
• Microscopic Imaging
• 3D Reconstruction

Background:

• Phase-shifting Fringe Projection Profilometry (FPP) is effective for macro-scale 3D measurements.
• Microscopic scale measurements face challenges due to limited depth-of-field, slowing down data acquisition and requiring mechanical adjustments.
• Existing methods struggle with deep microscopic objects.

Purpose of the Study:

• To introduce a novel approach combining digital holography (DH) with fringe projection for enhanced microscopic 3D measurements.
• To enable numerical refocusing of defocused regions in microscopic imaging.
• To overcome the depth-of-field limitations inherent in traditional FPP at the micro-scale.

Main Methods:

• Utilizing digital holography (DH) for capturing fringe patterns.
• Implementing numerical refocusing algorithms to reconstruct 3D data from defocused regions.
• Conducting experimental validation and comparing measurement noise against established DH and FPP techniques.

Main Results:

• The proposed DH method effectively minimizes measurement uncertainty under significant defocus conditions.
• For slight defocus, incoherent FPP demonstrated superior performance compared to coherent techniques.
• The new DH approach achieves performance comparable to other DH techniques in challenging microscopic scenarios.

Conclusions:

• Digital holography with fringe projection offers a viable solution for accurate and efficient 3D measurements of deep micro-scale objects.
• The ability to numerically refocus significantly improves measurement speed and reduces the need for mechanical adjustments.
• This technique expands the applicability of holographic methods in micro-metrology.