3D TV – A Distant Perspective

Following on from high-definition TV, 3D TV is expected to provide the next big technology push and consumer pull for the industry. 3D technology approaches have been around for many years but with varying degrees of inconvenience for the viewer. Many versions of 3D-TV have been shown at the past few IFA's. However, this time chip vendor NXP seems to be serious. The company was expected to show a demo of 3D TV content to selected visitors.

The technical lynchpin of NXP's demo was set to be the latest iteration of the PNX51xx display coprocessor, due for public announcement in the fourth quarter of 2009 or the first quarter of 2010. The imminent chip is designed to support three-dimensional images with spatial information.

Technically, 3D TV requires that images have been recorded stereoscopically, at least, and the entire signal chain has to be designed to accommodate and process this data accordingly. The critical point in the signal chain is the display. Two approaches are in place that, unfortunately, both require the viewer wears special eyeglasses.

In the "lining" technique, even and odd pixel lines in the display are containing the information for the left and the right eye, respectively. Polarizing filters in front of the display correspond with accordingly polarized eyeglasses used by the viewer. Thus, the two eyes of the viewer receive different images, generating the spatial impression. Since polarizing eyeglasses are available at low price, the technology is cheap.

In the "frame interleave" mode, alternating frames contain the respective images for left and right eye in a time sequenced manner. This technique requires shutter-equipped eyeglasses that are synchronized with alternating image frames.

Both techniques are associated with trade-offs in image quality: While the lining technique effectively reduces the number of lines and thus the image resolution, the frame interleave technique halves the number of effective frames per second.

For this reason, content providers and technologists are considering doubling the frame rate or the resolution. Both approaches would double the bandwidth required for transmission. "This however would go at the expense of the number of channels available to broadcasters," explained NXP business development manager Yong S. Choi. Since standards and infrastructure issues as well as strategic issues need to be cleared first, commercial 3D TV cannot be expected in the near future.

The industry is not yet inclined to step ahead with real products, at trade shows this year they only intend to "test the water," as Choi puts it. Nevertheless, the content industry is already "betting heavily on 3D," Choi said. "Some Hollywood directors are staking their careers on 3D."

By Christoph Hammerschmidt, EE Times