Decorrelation and anti-correlation from defocus in digital holographic interferometry

Area of Science:

• Optical Physics
• Metrology
• Digital Holography

Background:

• Speckle noise is a significant challenge in digital holographic interferometry, affecting image quality and measurement accuracy.
• Understanding speckle decorrelation is crucial for reliable quantitative phase measurements in holographic interferometry.
• Out-of-focus reconstruction in digital holography can introduce artifacts and alter speckle properties.

Purpose of the Study:

• To develop a theoretical model for speckle noise decorrelation in out-of-focus reconstructed images within digital Fresnel holographic interferometry.
• To investigate the influence of focus mismatch on the complex coherence factor in holographic interferometry.
• To validate the proposed theoretical model using simulated and experimental data.

Main Methods:

• Theoretical modeling of speckle noise decorrelation considering focus mismatch.
• Derivation of the complex coherence factor based on sensor-to-object and reconstruction distances.
• Validation through numerical simulations and experimental holographic interferometry setups.

Main Results:

• A theoretical model accurately describes speckle noise decorrelation in out-of-focus holographic interferometry.
• Focus mismatch significantly impacts the complex coherence factor, dependent on distances.
• Excellent agreement between theoretical predictions, simulated data, and experimental results confirms the model's validity.
• The phenomenon of anti-correlation in phase data was observed and analyzed.

Conclusions:

• The proposed theoretical model provides a robust framework for understanding speckle decorrelation in digital holographic interferometry.
• Accurate modeling of focus mismatch is essential for mitigating noise and improving measurement precision.
• The findings have implications for enhancing the reliability of quantitative phase measurements in various holographic applications.