Vortex annihilation to reduce phase singularities and resultant speckles in computer-generated holography

The natural depth sensation in computer-generated holography (CGH) comes from scattering effects caused by the random phase, but this also results in speckles. These speckles are directly linked to the optical vortices existing in the object phase and become intractable under coherent illumination. Here, we propose a vortex annihilation strategy cooperating with optimization algorithms to address phase singularities in CGH. It works out the scalar potential and vector potential in the object phase, based on which the irrotational part of the phase is extracted through an annihilation between optical vortices of opposite handedness. Our experimental results validate the effectiveness of the synthesized irrotational phase for a speckle-free viewing experience in holographic display, with the number of phase singularity reduced by a factor of ~100.