Three-dimensional display technologies aim to provide 3D visualization with a wide viewing angle, high resolution, and expansive display volume. However, current displays fall short of this goal because they have difficulty generating an adequate density of resolvable 3D pixels, known as voxels. An ultrathin 3D display system overcomes the challenges that typically limit glasses-free 3D displays, and provides a wide viewing angle without sacrificing image quality or depth of display. The display technology could enable highly interactive systems for healthcare, education, and entertainment. Researchers at Zhejiang University and Beijing University of Posts and Telecommunications used freeform optics to develop the technology. Freeform optics provided them with precise control of light, giving them the design flexibility needed to create an ultrathin, yet expansive directional backlight system. Each beam-shaping channel of the glasses-free, 3D display integrates an LED source, an aperture, and a freeform lens that precisely redirects incident light to generate uniform illumination. The researchers tiled these beam-shaping channels to create a tailored, large-area, highly directional backlight system. The ultrathin, 3D light-field display has a wide viewing angle of over 120° while maintaining clear image quality and vivid display depth. Courtesy of Zhejiang University/Rengmao Wu. They then added a module to the display, consisting of two layers of micro-triangular prisms, to improve the uniformity of backlight irradiance while preserving the directionality of the light. Large-area, lenticular lens arrays, designed to precisely control the light beam emanating from the backlight system, make it possible to construct highly miniaturized voxels. In glasses-free 3D light displays, the quality of the rendered 3D effect depends on how accurately the voxels are constructed, and on their number and size. Smaller, well-constructed voxels enable finer detail and more realistic depth. The directional backlight system and the light control module for voxel construction, which the researchers designed to achieve a wide viewing angle and highly miniaturized voxels, significantly enhance voxel resolution in the new 3D display. “In light field displays employing diffraction gratings or cylindrical lens arrays, voxel size is fundamentally constrained by the angular spread of backlight illumination,” professor Xinzhu Sang said. “Our system significantly improves voxel construction accuracy compared to existing scattering backlight-based 3D displays, achieving highly miniaturized voxels and substantial resolution enhancement.” To validate the new display architecture, the researchers demonstrated a 32-in directional, backlight-based prototype with a cabinet depth of just 28 mm. Roughly the size of a large computer monitor, the prototype provides dynamic 3D visualization and excellent clarity with a wide viewing angle of over 120° and a 3D display volume of 28 × 16 × 39 in. The ultra-slim cabinet depth of the prototype is exceptionally compact compared to existing directional, backlight-based light field display systems. “This level of compactness, combined with the substantial boost in resolution we achieved, represents an important step toward making the technology practical for real-world products,” professor Xu Liu, who led the research, said. The team evaluated the prototype’s performance using a 50-mm, fixed-focus lens with an f/2.8 aperture. This setup is often used to simulate how the human eye perceives depth and clarity. In one experiment, the researchers used the 3D display prototype to render images of an astronaut floating outside a space station. The display achieved a continuous depth range of 1 m and a viewing angle of more than 120°, enabling an immersive, realistic visual experience. The new 3D display produces 6x smaller voxels than conventional scattering backlight-based 3D display systems and maintains resolution even when the display is viewed from farther away than conventional systems. Its information utilization capabilities exceed that of currently available scattering backlight-based systems by more than two orders of magnitude, making the new 3D display system about 100-fold more efficient at using visual information to generate images than conventional displays. The rapid advancement of 3D display technology is advancing the potential of medical visualization systems, learning environments, and entertainment applications. The miniaturized-voxel, light field panel display system could be a driving force in the development of 3D displays for these and other industries. “The 3D display maintains crisp image quality across the entire imaging depth, which can help users visualize depth and spatial relationships for tasks requiring precise spatial understanding,” professor Rengmao Wu said. “This could, for example, help doctors easily see complex anatomical structures such as tumors or fractures in real time.” The team is working to further reduce the thickness and weight of the 3D display system and improve its optical efficiency. For commercialization, more work will be needed to develop smaller pixel structures, increase pixel density, and optimize pixel shape to enhance compatibility with 3D display technology. The research was published in Optica (www.doi.org/10.1364/OPTICA.571647).