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Seiko Epson readies 3D images for handsets

Posted: 21 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:2D? 3D? LCD? cellphone? handset?

While 3D is expected to be visible in the next-generation TV, some Japanese vendors are looking at all possibilities to bring 3D images to mobile screens.

Seiko Epson has released in Japan a prototype of 2.57-inch color LCD 3D display that seeks for a commercial launch in two years' time. The 3D LCD panel does not need special glasses.

Displaying 3D images on a mobile screen has particular challenges. The biggest is the inability to identify a fixed viewing distance between the user and the screen. Before 3D displays present a slightly different image to each eye. Images are first split, then displayed on the LCD panel. Lenticular lenses are put in front of the LCD panel so that images from different angles do not reach one eye at the same time. The 3D image display has no additional equipment when a fixed distance is built between an LCD panel and the viewer's eye. A handset user often must tilt the cellphone's LCD panel, making the viewing points to shift.

One solution is to capture the object's image from multiple angles, split it up and display on the panel as many images as possible. The more the image is split, the more depth that can be produced for the object displayed on the screen.

However, continuously raising the number of "splits" reduces the resolution of 3D images because the number of pixels used on the LCD panel remains the same.

"Since 3D display development is not driven by consumer demand, it is necessary to maintain the picture resolution of a 3D display at the same level as that of the 2D display," said Goro Hamagishi, general manager, display development center, R&D division, Seiko Epson.

Delivering better image
The issue is how to provide a smooth 3D image while maintaining its high quality. Seiko Epson's solution includes narrowing the image width that achieves each viewing point and designing special pixel alignment on its LCD display.

The image width at the viewing point is defined as the viewable range of the same image at one viewing location when the viewing point shifts horizontally.

Generally, the range is set from 62mm to 65mm, similar to the distance between the right and the left eyes. At that width, the number of 3D images that can be displayed on an LCD panel is limited to four.

Seiko Epson engineers trimmed that width from 31mm to 32.5mm. This gives eight "split-up" 3D images to be viewed on the LCD panel, producing smoother 3D viewing.

This approach also means that image resolution is dropped by one-eighth of what one can see on the original LCD panel. To address this issue, the company designed a new alignment for RGB dots that form one pixel. Instead of lining up each RGB dot horizontally in LCD panels, Seiko Epson's engineers arranged them like a staircase.

The new alignment decreased the image deterioration, horizontally to three-eighth, and vertically to one-third. Human eyes have sensitivity characteristics for horizontal resolution. Using a 1,024pixel x 786pixel (XGA) LCD panel, the researchers said they succeeded in displaying 384pixel x 256pixel (QVGA quality) 3D images per viewing point.

- Yoichiro Hata
EE Times

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