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

Scattering effects caused by the random phase distribution in computer-generated holography (CGH) produce a natural depth sensation, but they also result in speckles. These speckles are 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 with opposite handedness. Our experiment validates the effectiveness of the irrotational phase for a speckle-suppressed viewing experience in holographic display, with the number of phase singularity reduced by a factor of ∼100 for general grayscale objects.