Seiko Epson Develops 3-D LCD for Cellphones

While 3-D is expected to become all the rage for next-generation TV, some Japanese vendors are thinking ahead to figure out a way to bring 3-D images to mobile handset screens. Seiko Epson recently unveiled in Japan a prototype of 2.57-inch color LCD 3-D display aiming for a commercial launch in two years. The 3-D LCD panel requires no special glasses.

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

One solution is to capture the object's image from multiple angles, split it up and display as many images as possible on the panel. The more the image is split, the more depth that can be created for the object displayed on the screen. But continuously increasing the number of "splits" decreases the resolution of 3-D images since the number of pixels used on the LCD panel remains the same.

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

The issue is how to display a smooth 3-D image while maintaining its high quality. Seiko Epson's solution consists of narrowing the image width that reaches each viewing point and devising 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.

Usually, that range is set at 62 to 65 mm, similar to the distance between the right and left eye. At that pitch (width), the number of 3-D images that can be displayed on an LCD panel is limited to four. Seiko Epson engineers narrowed that width down to 31 to 32.5 mm. This allows eight "split-up" 3-D images to be displayed on the LCD panel, creating smoother 3-D viewing.

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

The new alignment minimized the image deterioration--horizontally to 3/8, and vertically to 1/3. Human eyes have sensitivity characteristics for horizontal resolution. Using a 1,024-x-786 pixel (XGA) LCD panel, the researchers said they succeeded in displaying 384 x 256 pixels (QVGA quality) 3-D images per viewing point.

By Yoichiro Hata, EE Times