Researchers presented a prototype glasses-free 3D light field display system with a significantly extended viewing distance thanks to a newly developed flat lens. The system is an important step towards compact and realistic 3D displays that could be used for televisions, portable electronics and tabletop devices.
Bright field displays use a dense field of light rays to produce real-time color 3D video that can be viewed without glasses. This approach to creating a 3D display allows multiple people to view the virtual scene at once, much like a real 3D object.
“Most brightfield 3D displays have a limited viewing range, which causes the virtual 3D image to degrade as the viewer moves away from the device,” the team leader said. researcher Wen Qiao of Soochow University. “The nanostructured flat lens we designed is only 100 microns thick and has a very large depth of field, allowing a high-quality virtual 3D scene to be seen from farther away.”
In Optical, a journal of Optica Publishing Group, the researchers report that their prototype display exhibits high efficiency and color fidelity over viewing distances of 24cm to 90cm. These features all combine to create a more realistic viewing experience.
“We developed this new technology in hopes of creating screens that could make people feel as if they were actually together while video conferencing,” Qiao said. “With the continued development of nanotechnology, we anticipate that glasses-free 3D displays will become a normal part of everyday life and change the way people interact with computers.”
Creating multiple views
Bright field displays create realistic images by projecting different views that allow the 3D scene to look the same when viewed from different angles. The focal length of the lenses used to create these views is the limiting factor when it comes to viewing distance.
To overcome this, the researchers carefully designed a new diffractive flat lens by patterning nanostructures on a flat surface in such a way as to focus the light. Interlacing several of these lenses allowed them to create a pixelated view modulator, the optical component that creates the different perspectives of a scene in a bright field display. A 3D display that creates four views, for example, would use four such lenses, each converging light into a single view.
“Because flat lenses provide superior light handling capability compared to traditional glass lenses, they can be used to solve dreaded problems such as limited motion parallax, crosstalk, visual fatigue, and viewing distances. limited viewing in 3D screens,” Qiao said.
Test the prototype
After showing that the lens achieved high resolution when focusing the red, green, and blue light used by LCD screens to create images, the researchers incorporated them into a prototype 3D light field display of 4 inches with viewing distances between 24 and 90 centimeters.
The display formed smooth horizontal parallax with less than 26% crosstalk at all viewing distances, meaning there were few errors that could cause eye strain or make the image look unrealistic. The screen also featured a luminous efficiency of up to 82%, far superior to other similar 3D display systems that have been reported. High luminous efficiency is important for creating a bright virtual image, especially for applications where power consumption is important, such as portable electronics.
Although the prototype had a viewing angle of only 9 degrees, the researchers say this could be increased to nearly 180 degrees by optimizing the design of the nanostructures used to make the flat lenses. In addition to studying this, they plan to further improve light efficiency by developing a more sophisticated design algorithm to manipulate the light beam at each pixel. They point out that easier ways to fabricate the nanostructures would also be needed for this type of display to be practical to fabricate.