Off-axis phase-only holograms of 3D objects using accelerated point-based Fresnel diffraction algorithm

- Accelerated point-based Fresnel diffraction algorithm is proposed for calculating off-axis phase-only holograms of 3D object.
- Calculating principal complex amplitude of object points on the z-axis in hologram plane using Fresnel diffraction formula.
- Using fast convolution operation based on FFT to calculate the phase-only holograms.
- Shortest recording distance and optimal recording distance have been determined to improve the imaging quality.

A method for calculating off-axis phase-only holograms of three-dimensional (3D) object using accelerated point-based Fresnel diffraction algorithm (PB-FDA) is proposed. The complex amplitude of the object points on the z-axis in hologram plane is calculated using Fresnel diffraction formula, called principal complex amplitudes (PCAs). The complex amplitudes of those off-axis object points of the same depth can be obtained by 2D shifting of PCAs. In order to improve the calculating speed of the PB-FDA, the convolution operation based on fast Fourier transform (FFT) is used to calculate the holograms rather than using the point-by-point spatial 2D shifting of the PCAs. The shortest recording distance of the PB-FDA is analyzed in order to remove the influence of multiple-order images in reconstructed images. The optimal recording distance of the PB-FDA is also analyzed to improve the quality of reconstructed images. Numerical reconstructions and optical reconstructions with a phase-only spatial light modulator (SLM) show that holographic 3D display is feasible with the proposed algorithm. The proposed PB-FDA can also avoid the influence of the zero-order image introduced by SLM in optical reconstructed images.