Fig. 1. Representative optical combiner solutions for AR display systems. (a) Freeform prism; (b) optical waveguide; (c) semi-reflective semi-transmissive lens; (d) schematic of an optical waveguide based on polarization-dependent metasurface design^[38]; (e) conceptual diagram of an exit pupil expander utilizing metasurface gratings and SRG couplers^[39]; (f) schematic illustration of achromatic full-color AR optical waveguide^[41]

Fig. 2. Schematic diagrams of selected 3D display technologies. (a) Illustrations of three types of visual aid glasses^[52]; (b) recording and reconstruction process in holographic technology^[53]; (c) volumetric 3D display system^[51]

Fig. 3. Anomalous refraction and reflection phenomena based on generalized Snell’s law^[60]. (a) Schematic illustration of generalized Snell’s law; (b) anomalous refraction induced by phase discontinuities

Fig. 4. Phase modulation mechanisms of metasurfaces. (a) Propagation phase metasurface^[54]; (b) geometric phase metasurface^[68]

Fig. 5. Schematic illustration of different optical field responses of local and nonlocal metasurfaces^[70]. (a)(c) Optical responses of ideal local metasurface in real space and momentum space; (b)(d) optical responses of nonlocal metasurface in real space and momentum space; (e) applications of nonlocal metasurfaces

Fig. 6. Schematic illustration of principle of integral imaging 3D display^[90]

Fig. 7. Schematic illustration of three focusing modes in integral imaging. (a) Real image mode; (b) virtual image mode; (c) focused image mode

Fig. 8. Schematic illustration of plenoptic function. (a) Seven-dimensional plenoptic function^[92]; (b) four-dimensional plenoptic function based on optical two-plane model^[93]

Fig. 9. Collection and display process of integral imaging based on four-dimensional plenoptic function

Fig. 10. Integral imaging 3D display based on achromatic metalens array^[56]. (a) Schematic illustration of metalens-based integral imaging; (b) SEM images of fabricated metalens sample; (c) experimental optical setup and 3D display results

Fig. 11. AR true 3D display based on Meta II^[20]. (a) Schematic illustration of display principle; (b) prototype of display module; (c) schematic diagram of microlens array rendering method; (d) 3D imaging results

Fig. 12. Computer-generated holography. (a) Diffraction based on triangular mesh modeling^[48]; (b) TDST system and holographic display suitable for AR^[104]; (c) schematic diagram of dynamic 3D scene holography using Kinect-based acquisition^[107]

Fig. 13. Holographic AR 3D light field display based on metasurface grating waveguide^[21]. (a) Schematic of display optical path; (b) structure of metasurface grating; (c) achromatic correction by optical path matching within waveguide; (d) electric field distributions at red (638 nm), green (521 nm), and blue (445 nm) wavelengths, with incident and diffracted wave vectors indicated by arrows