3D computer screens are coming
By John Boyd
Though we live in a three-dimensional world, we spend much of our waking time interacting with the two-dimensional worlds displayed on our computers, mobile phones, game consoles, music players, PDAs, and TVs.
This could be about to change. In August Epson unveiled a prototype high-resolution 3D LCD display that can be viewed without the need for special glasses, does not limit viewing to a single position, and eliminates most of the discomfort usually associated with watching 3D content.
To grasp how the new display works, it helps to have an understanding of the principle at work behind 3D imaging. In direct-view 3D displays (no glasses necessary) a barrier, known technically as a parallax barrier, is placed in front of the image so that each eye sees slightly different views of the same scene. The brain merges the two images, which is then perceived as a single 3D picture. The barrier, formed from a physical construct of slits on the LCD display, reveals different sets of the image's pixels to each eye, thereby creating the illusion of depth. Alternatively, a specially shaped lens called a lenticular lens (used in the new Epson display) produces a similar effect by refracting the light so that each eye sees a slightly different image at the same time. Unlike a standard barrier, which blocks out a good deal of the display's light, a lens like this allows most of the light to pass through to the viewer, producing a brighter image.
Direct-view 3D displays do have drawbacks, however. In order to see a quality 3D image with good resolution, the viewer has to remain in one fixed central location; deviating from this position compromises the 3D effect. This may work for limited personal use, but its restrictiveness has prevented the technology from achieving commercial success.
Display manufacturers are therefore examining other approaches, one of which is a multi-view display where the 3D image can be seen from several viewing points. Multi-viewing not only provides a degree of freedom for the viewer to change viewing positions, but it has the added advantage of allowing several people to view the image at the same time.
"The downsides of multi-viewing are a deterioration in the quality of the image as the number of viewing positions is increased and an uneven 3D viewing experience," says Goro Hamagishi, general manager at Epson's Display Development Center. "For engineers, it's been a choice of emphasizing either good 3D image resolution or smooth, comfortable 3D viewing by increasing the number of viewing points. But not both."
Hamagishi, who has spent a decade researching and developing 3D technologies, decided to investigate just what was behind the source of the viewing discomfort. He used his experience in head-tracking research to learn exactly what the viewer was seeing and discovered that as a person moved outside an optimum viewing position, a 2D image would come into view, disrupting the continuous 3D effect and so creating viewing discomfort.
"Once I understood what was causing the problem, it was actually quite easy to come up with a solution," says Hamagashi. He explains that in conventional multi-view displays the view width–the horizontal span over which one eye perceives the same image on the display–is standardized at between 62 mm and 65 mm, a measurement based on the distance between the pupils of an average adult's eyes. As a result, there is a relatively large difference in what is viewed at each viewpoint, which leads to 2D blocks of the image being generated as a viewer changes viewing positions.
To eliminate these interfering blocks, "We researched the phenomenon further and found that a view width of between 31 mm and 32.5 mm, about half the standard width, was more appropriate, so we redesigned the lenticular lens to achieve this width," explains Hamagishi. "The outcome is a simple and effective way to produce high-quality, smooth 3D viewing with little of the discomfort previously experienced." What is more, he says that these design changes do not add significantly to the display's manufacturing costs.
The trial display announced by Epson in August is a high-resolution 2.57-inch low-temperature polysilicon 3D LCD with a pixel count of 1027 x 768, or XGA resolution. A lenticular lens is used to make the image three-dimensional. The result is a display providing eight viewpoints with view widths of 32.5 mm. It provides a viewing angle of 25 degrees and an optimum viewing distance of 450 mm. A 3D image viewed at any one position is composed of 384 x 256 pixels–equal to QVGA quality.
If the technology hurdles standing in the way of producing enjoyable 3D viewing proved relatively easy to overcome, Hamagishi is quick to admit the business challenges he faces going forward will be considerably harder to deal with. "Our task now is to build a collaborative network with 3D content creators to standardize on 31 mm to 32.5 mm for the view widths of 3D displays," he says. "Content is going to be the key to success in this business."
He is referring to the fact that manufacturers of 3D displays cannot expect to sell their products unless there is compelling 3D content that users want to watch. Given that such content requires the use of several cameras shooting from different positions, creating it is no easy matter. "We can't build a market on our own," says Hamagishi. "We need the help of the entire 3D industry."
In the meantime, Epson is continuing to fine-tune its 3D display technology. The current prototype is running off a PC for trial purposes, because generating the 3D content requires more processing power than is currently available in most mobile phones, the likely target market of the company's first commercial displays. By the time Epson is ready to release its first product in two years' time, however, the company believes more phones with the necessary power to run 3D content will be available.
"Technologically speaking, there is no restriction on the size of display that can use this 3D technology," says Hamagishi. "So besides mobile phones, PDAs, handheld game consoles, mobile TVs–all these can be our targets."