Fig. 1. Change process of human-computer interaction information capacity with time

Fig. 2. Main key parameters of optical characteristics of HUD system

Fig. 3. Range of road conditions corresponding to different display performances of HUD

Fig. 4. Three HUD principles^[18]. (a) C-HUD; (b) W-HUD; (c) AR-HUD

Fig. 5. SLM-based single plane AR-HUD^[44]. (a) Schematic of foveal imaging head-up display system; (b) optical part experimental device of foveal imaging head-up display system; (c) experimental result of foveal imaging head-up display system

Fig. 6. Schematic of HUD optical principle based on optical waveguide. (a) Principle of head-up display system based on arrayed waveguide grating; (b) principle of head-up display system based on surface relief grating; (c) principle of head-up display system based on volume holographic grating

Fig. 7. Single plane AR-HUD based on array waveguide^[47]. (a) Schematic of the principle of waveguide augmented reality head-up display system based on microprism array; (b) schematic of the overall structure of waveguide augmented reality head-up display system based on microprism array; (c) original drawing of system test; (d) imaging effect of waveguide augmented reality head-up display system based on microprism array

Fig. 8. Single plane AR-HUD based on volume holography. (a) Effect of large field-of-view augmented reality head-up display^[48]; (b) principle of SBG-based holographic optical waveguide head-up display system^[48]; (c) experimental device of holographic optical waveguide head-up display system based on SBG^[48]; (d) principle of head-up display system based on volume holography^[50]; (e) experimental device of head-up display system based on volume holography^[50]; (f) experimental rendering of head-up display system based on volume holography^[50]

Fig. 9. Multi plane AR-HUD based on free mirror^[62]. (a) Principle of head-up display system based on a single image generation unit; (b) head-up display prototype based on a single image generation unit; (c) close display effect of head-up display system based on a single image generation unit; (d) remote display effect of head-up display system based on a single image generation unit

Fig. 10. Multi plane AR-HUD based on SLM^[71]. (a) Principle of head-up display system based on SLM; (b) Head-up display system prototype based on SLM; (c) experimental rendering of head-up display system based on SLM at 3 m; (d) experimental rendering of the head-up display system based on SLM at 30 m

Fig. 11. HOE-based multiplanar AR-HUD. (a) Principle of multi plane HUD using HOE angle selectivity^[72]; (b) principle of multi plane HUD using HOE wavelength selectivity^[72]; (c) prototype of double depth head-up display system based on volume holography^[72]; (d) display effect of double depth head-up display system based on volume holography^[72]; (e) principle of augmented reality head-up display system with real-virtual dual mode^[73]; (f) prototype of real-virtual dual mode augmented reality head-up display system^[73]; (g) display rendering of real-virtual dual mode augmented reality head-up display system^[73]

Fig. 12. AR-3D-HUD based on geometric elements^[85]. (a) Principle of light field virtual projection head-up display system; (b) prototype of light field virtual projection head-up display system; (c) display effect of light field virtual projection head-up display system

Fig. 13. AR-3D-HUD based on volume holography. (a) AR-HUD prototype introduced by Seereal corporation ^[91]; (b) display effect of AR-HUD introduced by Seereal corporation at 1.9 m distance^[91]; (c) display effect of AR-HUD introduced by Seereal corporation at 4.5 m distance ^[91]; (d) principle of projection holographic 3D display system^[92]; (e) chessboard reconstructed by projection holographic 3D system observed at the target observation point^[92]; (f) three-dimensional scene reconstructed with two squares at 1 cm and 5 cm behind the holographic screen^[92]