A new technique will help in the production of light weight, inexpensive 2D and 3D convertible screens in mobile devices.
Convertible video displays that provide 2D and 3D imaging without the necessity of any eyewear can be of great convenience to users, who will otherwise have to carry another accessory. Though these autostereoscopic displays have made their appearance in the TV market, the drawbacks of the technology come to light only when they are used at close viewing distances. Such displays must generally be viewed at a distance of approximately three ft or one meter, making it difficult to practically apply the technology in smaller screens of mobile devices.
A new technique of making such convertible displays, developed by researchers from Seoul National University, South Korea has overcome the drawbacks. This method provides these devices with near-viewing abilities, shrinking and simplifying the technology’s design. The paper describing this new method was published in The Optical Society’s (OSA) journal Optics Express, on 31st October, 2016.
In the case of eyewear-free displays, all the action happens behind the screen, where the optics and pixels of the images are layered to create the stereoscopic effect. These optically illusive effects can be produced in two major ways: by placing an array of micro-filters, known as parallax barriers, or an array of micro-lenses, known as lenticular lenses, in front of the images to make their appearance depend on the angle at which they are viewed.
This effect can be seen at its simplest form in movie posters where the images seem to change as one walks by. To achieve this, two or sometimes more images are interlaced. These interlaced images are then printed behind a plastic layer that has grooves corresponding to the intertwined pattern. These grooves operate as separate, interlaced arrays of filters or lenses that depict one image when a person approaches and another when they depart, viewing the poster from different angles.
Such layers are active in 2D or 3D convertible displays, and can be switched on/off electronically. The viewing distance is mainly determined by the gap between the barrier layer and the image layer. When these layers are stacked closely together, they enable viewing at a closer distance
In the paper detailing the study, Sin-Doo Lee, a professor of electrical engineering at Seoul National University, and team discuss a monolithic structure that can successfully combine a polarizing sheet, an image layer, and the active parallax barrier into one panel. The team opted for a polarizing interlayer in place of two unconnected image and barrier panels. While one side of this interlayer is in direct contact with the image layer, on the other side, the active parallax barrier of a liquid crystal layer is created as an array of periodically patterned indium-tin-oxide (ITO) electrodes.
The minimum separation required between the image and barrier layers is facilitated by this interlayer, which provides the short viewing distance that is essential in the small screens of mobile devices.
The polarizing interlayer approach here will allow high resolution together with design flexibility of the displays, and will be applicable for fabricating other types of displays such as viewing-angle switchable devices. Our technology will definitely benefit display companies in manufacturing low cost and light weight 2D/3D convertible displays for mobile applications. Under mobile environments, the weight is one of the important factors.
Sin-Doo Lee, a professor of electrical engineering at Seoul National University
In addition to being applicable in LC-based 2D/3D displays, this idea can also be applied in OLED-based 2D/3D displays, which provides the application to a wide variety of current and future device designs.