Holographic near-eye display with improved image quality and depth cue based on pupil optimization

Holographic near-eye display is thought as one of ideal entrance of "metaverse", since it reconstructs the full wavefront information and provides all kinds of depth cues for human eye. Previous studies hardly noticed the influence of limited eye pupil aperture on the observation of holographic images, and calculated the hologram without considering the pupil aperture. In this paper, the incomplete image issue and increased speckle noise caused by pupil sampling is analyzed first. Then, the lensless solution based on spherical wave phase is proposed for observing complete and speckle-free images, but with two issues to be addressed, degraded image quality and inapparent depth cue. A pupil optimization-based iterative algorithm is proposed for better image quality and enhanced depth cue. By including the pupil filtering in the iteration to restrict the effective wavefront area at the pupil plane, the wavefront information loss caused by pupil sampling is reduced and the image quality is optimized. The initial spherical phase is also optimized, leading to enhanced depth cues. Both simulation and experiment verify that the proposed lensless holographic NED effectively handles the pupil sampling issue, and has improved image quality and depth cue compared with conventional method.