Fig. 5. Schemes to reduce the form factor of a VR display.

a Schematic of a basic VR optical configuration. b Achromatic metalens used as VR eyepiece. c VR based on curved display and lenslet array. d Basic working principle of a VR display based on pancake optics. e VR with pancake optics and Fresnel lens array. f VR with pancake optics based on purely HOEs. Reprinted from b ref. ⁸⁷ under the Creative Commons Attribution 4.0 License. Adapted from c ref. ⁸⁸ with permission from IEEE, e ref. ⁹¹ and f ref. ⁹² under the Creative Commons Attribution 4.0 License