Implementation of Fresnel Digital Holography: Coaxial and Off-Axis Methods

To fully implement Fresnel digital holography, there are two primary methodologies: coaxial and off-axis configurations. Each method exhibits distinct advantages and limitations that require careful evaluation before selection. In coaxial holography, a single laser beam is divided into reference and object waves using a beam splitter, typically implemented through MATLAB's wave propagation functions with careful phase alignment. Off-axis holography employs two separate beams with angular separation, requiring more complex Fourier transform operations and spatial frequency filtering in the reconstruction algorithm.

While coaxial setup simplifies optical alignment through direct in-line interference patterns, it may yield lower resolution due to overlapping diffraction orders. The reconstruction code typically involves inverse Fresnel transforms with phase correction. Conversely, off-axis holography demands precise angle calibration between beams but enables higher resolution through carrier frequency separation in the Fourier domain. Implementation often includes windowed Fourier transforms and phase unwrapping algorithms for quality enhancement.

We encourage researchers to download and experiment with both methods, incorporating numerical propagation algorithms and phase retrieval techniques. Understanding the computational differences—such as the need for Fourier domain filtering in off-axis versus direct numerical propagation in coaxial—will help determine the optimal approach for specific applications like microscopic imaging or 3D reconstruction.