5/24/2010 11:29 AM
When one considers 3-D imaging, there is a lot of history and a striking array of methods and technologies to consider. The first 3-D imaging dates back to 1844, when the Scottish inventor and writer David Brewster introduced the stereoscope, a device that could take photographic pictures in 3-D. Through fits and starts, 3-D has had a long and convoluted history that is still far from unresolved.
In the 1950s, when TV became popular in the United States, many 3-D movies were produced. The first was “Bwana Devil” from United Artists, which could be seen all across the United States in 1952. Subsequently, TV stations began airing 3-D serials based on the same technology as 3-D movies.
Virtually all 3-D productions, whether in movie theaters or on home TV, have used some form of glasses. Anaglyphic 3-D used passive red-cyan glasses, while polarization 3-D used passive polarized glasses. Most modern systems use alternate-frame sequencing with active-shutter glasses, but the pinnacle of the technology will come when the 3-D effect can be displayed using no glasses or headgear.
Today, stereoscopy is the most widely accepted method for making and delivering 3-D video. It involves capturing stereo pairs in a two-view setup, with cameras mounted side by side and separated by the same distance as that between a person’s pupils. Legacy film or video material in 2-D can be converted to a 3-D “look” with depth processing. However, a convincing effect is harder to achieve, and the resulting image often looks like a cardboard miniature.
Today’s 3-D-ready TV sets are those that operate in 3-D mode (in addition to regular 2-D mode), in conjunction with LCD shutter glasses. The TV set tells the glasses which eye should see the image being exhibited at the moment, creating a stereoscopic image. These TV sets usually support HDMI v1.4 and a minimum (input and output) refresh rate of 120Hz.
While the sets are already available in retail, the entertainment industry is still trying to adopt a common and compatible standard for 3-D in home electronics. Some issues under consideration are the type of 3-D glasses (passive or active and each manufacturer uses proprietary glasses); how to present a faster frame rate in HD to avoid judder; 3-D film enhancement; bandwidth considerations; subtitles; recording format; and a Blu-ray standard.
Then there’s the creation of 3-D TV standards. Currently, there are several techniques for stereoscopic video coding as well as stereoscopic distribution formatting, including anaglyph, quincunx and 2D plus Delta.
Content providers, such as Disney, DreamWorks and other Hollywood studios, and technology developers, such as Philips, have asked the SMPTE for the development of a 3-D TV standard to avoid a battle of formats. They want to guarantee consumers that they will be able to view the 3-D content they purchase with the appropriate technology solutions at a range of prices; that process is still underway.
HDMI Version 1.4, released in June 2009, defines a number of 3-D transmission formats. The format frame packing (left and right image packed into one video frame with twice the normal bandwidth) is mandatory for HDMI 1.4 3-D devices. All three resolutions (720p50, 720p60 and 1080p24) have to be supported by display devices, and at least one of those has to be supported by playback devices.
With all of these issues still unresolved, 3-D broadcasting has begun to emerge in the public conscious. Broadcasters are using different methods for delivering signals. The precision of digital technology makes it easier, but unified standards are still not written. What is being sold as the first year of the 3-D revolution is actually one more experimental step in a long and winding road that has more than 150 years of history.