Augmented Reality and Virtual Reality Displays: Perspectives and Challenges

Abstract

As one of the most promising candidates for next-generation mobile platform, augmented reality (AR) and virtual reality (VR) have potential to revolutionize the ways we perceive and interact with various digital information. In the meantime, recent advances in display and optical technologies, together with the rapidly developing digital processers, offer new development directions to advancing the near-eye display systems further. In this perspective paper, we start by analyzing the optical requirements in near-eye displays poised by the human visual system and then compare it against the specifications of state-of-the-art devices, which reasonably shows the main challenges in near-eye displays at the present stage. Afterward, potential solutions to address these challenges in both AR and VR displays are presented case by case, including the most recent optical research and development, which are already or have the potential to be industrialized for extended reality displays.

Keywords: Laser; Optical Imaging; Optical Materials; Photonics.

Graphical abstract

Figure 1

Illustration on the Performance of Human Vision (A) The profile of human FOV. (B) The relation between human visual acuity and visual angle. (C) Sketch of the VAC issue. The accommodation cue coincides with vergence cue when viewing a real object (left). The mismatch occurs when viewing a virtual object displayed at a fixed plane (right).

Figure 2

The Development Trend of Panel Resolution The pixel density of display panels will gradually increase for VR application. Before panels with ideal pixel density are available at low cost, it is also feasible to employ global resolution enhancement based on mechanical or optical wobulation method and local resolution enhancement with foveated display technologies.

Figure 3

Optical Structures of AR Systems with Extended FOV (A) Schematic illustration of the LNED system. TIR happens at each reflection during the propagation, and the angle is marked in orange. (B) Lightguide-based polarization multiplexing system for enlarging FOV. The system is based on two PVGs with opposite polarization responses (LCP and RCP) and different diffraction angles. (C) Schematic diagrams of the Maxwellian view system, including the imaging principle and two distinct forms derived from it: partial reflector and lightguide structure.

Figure 4

Schematic Plots of Major Microdisplays and Combiners The microdisplays cover liquid-crystal-on-silicon (LCoS), digital light processer (DLP), laser beam scanner (LBS), micro organic light-emitting diode (μOLED), and micro light-emitting diode (μLED), whereas the combiners include freeform half mirror, birdbath, freeform prism, off-axis holographic optical element (HOE), cascaded mirrors, and grating couplers. Three kinds of grating couplers are also highlighted: surface relief grating (SRG), volume Bragg grating (VBG), and polarization volume grating (PVG).