Near-eye display: from lab to commercial applications

Near-eye display, also known as head-mounted display, has emerged as a vital approach to give humans virtual images since its invention dating back to the last century. However,the typically poor performance impose limitations in the on-demand applications of near-eye display. In particular, for the ultimate realization of commercial near-eye display, it is necessary to provide an ultra-wide field of view (FOV), obvious depth cues and a compact form factor with acceptable weight. In recent years, various display methods have been proposed as potential solutions to these problems. Freeform surface elements can be a suitable way for the achievement of not only an impressive field of view but also an improved and lightened image, but its weight and volume can hardly be wearable. Potential solutions include but are not limited to:inserting reflective mirrors into the system, replacing the spherical lens group with a wedge-shaped freeform prism and applying gradient index lenses. Depth cues can be fulfilled by retinal projection, multi-focal, holographic displays and so on. Each of these technologies has unique disadvantages. For instance, it is most challenging to develop full-color,high-resolution holographic displays with acceptable price and FOV. Metasurface may be the possible solution.Multi-focal and vary-focal plane displays often comes at the cost of both time multiplexing and large data bandwidth. Retinal projection gives observer clear images with no relation to distance, however, the propagating light must pass through center of pupil. Here, we investigate recent developments in near-eye display, systematically classify vital problems in near-eye display systems and analyze technical principle of solutions to them. Meanwhile, prospect for the future development of each technology will be proposed.