Off-axis digital holographic particle positioning based on polarization-sensitive wavefront curvature estimation

Area of Science:

• Optical Metrology
• Particle Imaging
• Holography

Background:

• Holographic particle imaging struggles with precise axial positioning due to poor resolution.
• Accurate 3D particle localization is crucial for applications like particle imaging velocimetry.

Purpose of the Study:

• To develop and validate a novel method for estimating the axial position of micrometer particles using holographic data.
• To improve the accuracy of 3D particle positioning in holographic particle imaging.

Main Methods:

• Utilized off-axis holography to record scattered light at 90 degrees, obtaining complex light amplitude.
• Reconstructed a complex-valued volume and calculated phase gradients to estimate wavefront curvature.
• Identified the axial position by finding where the wavefront curvature of scattered light becomes zero.

Main Results:

• Simulations confirmed that wavefront curvature approaches zero at the particle's true axial position.
• Experimentally tracked a 100 μm axial translation of particles in a silicon cube using a telecentric holographic system.
• Achieved a mean displacement of 105.0 μm with a standard deviation of 25.3 μm for tracked particles.

Conclusions:

• The developed method accurately estimates particle axial position by analyzing wavefront curvature.
• This technique offers a viable solution for enhancing 3D particle localization in holographic imaging applications.
• The findings demonstrate the potential for improved particle tracking and analysis in fluid dynamics and other fields.