3D holographic near-eye display based on Fraunhofer diffraction using metalens as an eyepiece

Near-eye display (NED) systems for virtual reality (VR) and augmented reality (AR) have been rapidly developing. However, the conventional three-dimensional (3D) display methods are always disturbed by excessive binocular parallax and accommodation-convergence conflict. Although computer-generated holography (CGH) has recently experienced a renaissance for the ability of generating real 3D scenes, the widespread use of holographic VR/AR devices are limited by the bulky refractive and diffractive optics in the complicated optical system. To address these problems, a NED system combining the 3D CGH based on Fraunhofer diffraction and a metalens with a 5 mm diameter as an eyepiece is proposed in this paper. Based on the fact that metasurfaces are of substantial interest for their extraordinary capability of wavefront shaping in a subwavelength scale, the introducing of the metalens eyepiece surly facilitates lightening the CGH-NED systems. Experiments are carried out for this design, where Fraunhofer diffraction with digital lens phases of different focal lengths are applied to simulate the wave propagations to produce computer-generated hologram, and the metalens transforms the holographic reconstructed 3D image into virtual image to realize NED. In the experiment, the metalens eyepiece composed of silicon nitride anisotropic nanofins is fabricated with the diffraction efficiency and field of view for 532 nm incidence of 15.7% and 31 degrees, respectively. Our work combining of CGH and metalens may provide a promising solution in future for computer-generated holographic 3D portable display device realization.