Fig. 1. Principle schematic of human eye VAC. (a) Light from objects at different distances enters eyes and is refracted by lens and imaged on retina^[29]; (b) left and right eyes watch 3D images of film sources with parallax^[39]; (c1)-(c4) schematic of VAC with an intersecting raster grid^[20]; (d), (e), (f) VAC is illustrated by a ball and a Rubik's cube^[40]

Fig. 2. Current mainstream VAC solution classification. Without depth information^［47］: (a1) collimated illumination Maxwellian display; (a2) image filtering Maxwellian display; (a3) scanning laser projection Maxwellian display. With partially depth information: (b1) PSLC film multi-focal plane^［50］; (b2) multi-display spatial-multiplexed multi-focal plane^［118］; (b3) optofluidic adaptive focus lens^［52］; (b4) liquid crystal adaptive focus lens^［54］. With complete depth information: (c1) integral imaging display based on microlens array^［40］; (c2) holographic display based on complex amplitude modulation^［62］; (c3) holographic display based on wavefront modulation^［63］

Fig. 3. Maxwellian display system with pupil expanded^[76]. (a) Image filtering Maxwellian display. HOE as coupling-out element; (b) multiplexed HOE as coupling-out element; (c) screen display of different positions with pupil expanded

Fig. 4. Axial pupil expansion solution for Maxwellian near-eye display system^[79]. (a) Eye is held rigidly at Maxwellian beam point position ; (b) forward shift of eye occurs in axial direction; (c) compensated by FTL; (d) forward shift of eye occurs, display image missing; (e) display full image compensated by FTL

Fig. 5. Microdisplay and MEMS resonators for laser beam scanning displays. (a) JBD's Micro-LED^[104]; (b) Sony's Micro-OLED^[105]; (c) Himax's LCoS^[106]; (d) schematic of color projection display by MEMS resonators through 3 beams of RGB laser color combining^[49]; (e) Microsoft's MEMS used in AR near-eye displays^[103]; (f) laser beam first passes through MEMS and then focuses by concave mirror to form Maxwellian near-eye display^[103]; (g) single stage MEMS resonators used in Microsoft's HoloLens 2^[107]; (h) two-stage MEMS resonators reported by Hofmann et al^[49]; (i) schematic of structure of near-eye display module MEMS device in Microsoft's HoloLens 2^[107]

Fig. 6. Multi-focal plane AR near-eye display solution. (a1)-(a2) Magic Leap's scheme arranges 6 waveguide light coupling-out layers to achieve two focal plane displays at 1 m and 3 m distances^[112]; (b) schematic of color diffraction waveguide light coupling-in and coupling-out by 3 RGB beams^[120]; (c) Cheng et al. used two microdisplays in form of spatial multiplexing to achieve a two-focal plane display with free-form prism design^[118]

Fig. 7. Multi-focal plane near-eye display based on PSLC^[50]. (a) Schematic diagram of a multi-focal plane near-eye display using PSLC; (b) arrangement of liquid crystal (LC) molecules inside PSLC films in powered and non-powered states

Fig. 8. AR near-eye display system based on varifocal principle. (a) Meta's varifocal Fresnel LC lens consists of 28 ring bands^[54]; (b) comparison of design profile and measured profile of dimention of Fresnel LC varifocal lens^[54]; (c) internal multilayer structure of Fresnel LC varifocal lens and its control circuit^[54]; (d) schematic diagram of optofluidic varifocal lens applied to AR near-eye display^[52]; (e) experimental verification of letter display for two distances of 100 mm and 150 mm^[52]

Fig. 9. Near-eye display solution based on light field display technology to relieve VAC. (a) Integral imaging units combined with free-form prisms^[40]; (b) near-eye display glasses prototype based on integral imaging^[148]; (c) stereo pixel information recorded on prototype display^[148]; (d) compressive light field display based on mask; (e) super multi-view display technology^[161]

Fig. 10. Near-eye display based on complex amplitude wavefront reconstruction with full depth information that eliminates VAC. (a) Wavefront reconstruction by cascaded amplitude type hologram^[62]; (b) prototype design and effect of AR near-eye display corresponding to (a)^[62]; (c) wavefront reconstruction by phase type hologram^[63]; (d) prototype design and effect of AR near-eye display corresponding to (c)^[63]