Glasses-free 3D displays could transform the portable electronics industry. However, the limited resolution of display panels in existing 3D displays compromises spatial and angular resolution as well as viewing angle capabilities. An approach to 3D displays developed by scientists at Soochow University distributes display information nonuniformly, based on the viewing habits of people. The new technique preserves high angular resolution in the central viewing region — while maintaining a wide viewing angle. In the Soochow team’s approach, spatially variant information is projected based on the frequency of observation. Densely packaged views are arranged at the center, and sparsely arranged views are distributed at the periphery. The approach provides stereoscopic vision with a smooth motion parallax at the central view and enlarges the viewing angle at the periphery view. To support their display strategy, the researchers developed a large-scale 2D-metagrating complex (2DMC) to manipulate differently shaped views. As a view modulator, the 2DMC enabled control over the propagation direction and the irradiance distribution of the emergent light from each 2D metagrating. Due to the limited resolution of display panels, current 3D displays suffer from a trade-off among the spatial resolution, angular resolution, and viewing angle. Inspired by the so-called spatially variant resolution imaging found in vertebrate eyes, a team of researchers proposed a 3D display with spatially variant information density. Performance of the foveated glasses-free 3D display is shown. (a) Images of Albert Einstein, and (b) whales and lotus leaves, observed from various views with natural motion parallax and color mixing. Numbers in the lower left corner represent the viewing angle of the image. Courtesy of Jianyu Hua, Erkai Hua, Fengbin Zhou, Jiacheng Shi, Chinhua Wang, Huigao Duan, Yueqiang Hu, Wen Qiao, and Linsen Chen. The researchers designed the large-scale 2DMC for three purposes: to vary the angular separation of the views in different regions; to tailor the irradiance pattern of each view to eliminate overlap between views and avoid crosstalk; and to avoid gaps between views to ensure a smooth transition within the field of view. The researchers manipulated the 2DMC to generate the desired radiation patterns; for example, the 2DMC generated dot-shaped views to provide the highest information density. It can also be used to generate vertically oriented, line-shaped views to reduce information density in the vertical direction, while maintaining information density in the horizontal direction. The 2DMC view modulator can also be used to eliminate crosstalk or increase viewing depth. By combining views with a fan-shaped irradiance pattern, the team was able to realize a tabletop 3D display system with variant information density. This provided high spatial and angular resolution at the most comfortable viewing zone for people. “In prior studies, constant information density was provided within the viewing angle by views with the same distribution pattern,” the researchers said. “In contrast, we propose a 3D display with spatially variant information density by precisely manipulating the view distribution into a hybrid dot/line/rectangle shape. As a result, the information density will be modulated as in the foveated vision of vertebrate eyes.” Since the periphery viewing zone typically is used less, the researchers suppressed the redundant depth information and broadened the FOV to a range comparable to that of a 2D display panel. The researchers also developed a flexible interference lithography system that enabled them to fabricate the view modulator with more than 1 million pixelated 2D metagratings over an area greater than 9 in. Using their approach to 3D displays, they demonstrated that a static or video rate, full-color 3D display with a FOV of 160° could be achieved with display information totaling less than 4 K. The 3D display system has a thin, light form factor that allows it to be integrated with off-the-shelf flat panels. The integration possibilities make it potentially useful for applications for portable electronic devices. The research was published in Light: Science & Applications (www.doi.org/10.1038/s41377-021-00651-1).