High-numerical-aperture microlens shape measurement with digital holographic microscopy

Area of Science:

• Optical Engineering
• Microscopy
• Metrology

Background:

• Holographic microscopy is valuable for micro-optical element characterization.
• High numerical aperture (NA) micro-optics present challenges for traditional shape measurement.
• Existing methods struggle with accurate phase reconstruction for complex microstructures.

Purpose of the Study:

• To introduce a novel algorithm for overcoming limitations in holographic microscopic shape measurement.
• To enable precise shape reconstruction of micro-optical elements with high NA.
• To provide a simple yet accurate method for phase-based surface profiling.

Main Methods:

• Developed a new algorithm analyzing local ray transition for phase reconstruction.
• Algorithm adapted for both transmission and reflection holographic configurations.
• Validated through extensive simulations and experimental testing.

Main Results:

• Successfully reconstructed the height distribution of spherical and cylindrical microlenses.
• Achieved accurate measurements for micro-optics with NA up to 0.3.
• Demonstrated algorithm's effectiveness in a holographic Mach-Zehnder setup.

Conclusions:

• The developed algorithm offers a significant advancement in micro-optical element metrology.
• It provides a robust solution for shape measurement challenges posed by high NA.
• The method is experimentally verified and suitable for practical applications.