In the world of science, researchers are always looking to the future. While consumers are still scratching their heads and trying to decide which high-definition television (HDTV) to buy for their home theatres, researchers in laboratories around the world are already working to develop technologies that would surpass HDTV.

What will be the next step in the evolution of television? While there are labs in Japan that are working on super high-definition displays, the next true milestone is expected to be much more significant than simply improving image sharpness and color. At the Communications Research Centre Canada (CRC), researchers believe the next coup in the advancement of television will involve the addition of a third dimension. This monumental step can be likened to the addition of color to black-and-white television displays. In the future, stereoscopic or three-dimensional (3D-TV) displays will allow viewers to immerse themselves inside a world of objects that are separated in depth, far beyond the screen's surface. Best of all, you won't need those restrictive red and blue glasses that our parents or grandparents wore to enjoy 3D in the movie theatre.

At the CRC, research into 3D-TV has been underway since the mid 90s. Initial research projects addressed the important issue of determining the perceptual benefits that 3D would bring. More recently, the focus has shifted to human visual characteristics that could be exploited for applications in video coding, transmission, storage and display of 3D program material. In addition, CRC is also active in the standardization of stereoscopic technology.

How does 3D-TV work?

Since our two eyes are located at different positions in the head, the images perceived with the left eye are slightly different from those observed with the right eye. Differences in the horizontal positioning of objects in the left and right eye images are known as disparities, and our brains are smart enough to convert this into depth information-much like a surveyor solving a triangulation problem. 3D-TV mimics this real-world situation by presenting the viewer with two sets of slightly different images, one for the left eye and one for the right eye. Thus, compared to standard TV, 3D-TV conveys extra information in the form of disparity information contained in the dissimilar images, thereby greatly enhancing the sensation of depth and presence.

The major difference between a standard TV and a 3D-TV is the enhanced technologies that are needed to separately display images to the left and right eyes of a viewer. In the past, successful implementations of 3D display systems have involved some form of special glasses, such as red-blue or red-green colored glasses with anaglyphs, polarized glasses with the polarization method, and liquid crystal shutter glasses with time-sequential technology. The need to wear glasses, however, is possibly the most restrictive barrier preventing broadcasters from considering 3D-TV as a serious option. Today, with the advent of autostereoscopic displays, this gloomy scenario may change, as with these displays the viewer is not required to wear any special glasses to experience the 3D effect.

Autostereoscopic displays are conventional displays - with a twist. The most common are equipped with a plastic lenticular sheet made of many tiny lenses placed in front of the LCD screen. The tiny lenses redirect the light coming from each pixel in a controlled fashion, so that each eye sees different views. Most autostereoscopic displays typically employ nine to 16 different views of a scene, whereas a regular TV displays only one. These different views are presented simultaneously on the TV screen but they are spatially interleaved in alternate columns of pixels. The lenticular sheet redirects the light coming from each view in a specific direction in a fan-like fashion. As a result, one eye sees one view whereas the other eye sees another view, recreating the stereoscopic effect.

Issues with 3D-TV

Despite the major advancements afforded by autostereoscopic displays, a number of issues need to be addressed before 3D-TV is ready for the general public. High-quality stereoscopic content production will require multiple views captured with multiple cameras. Coding and transmission requirements for broadcasting such a high volume of video information will be considerable.

At the CRC, researchers are currently investigating advanced compression techniques for coding multiple views of the same scene and novel methods for transmitting the depth information contained in a scene. Other research issues include converting 2D images to 3D and viewing interpolation from a stereoscopic pair of views. Visual comfort and image quality assessment involving the use of human viewers for testing are other hot topics of research, and CRC is among the leading research institutions in these areas of research.

How long will it take for 3D-TV to become a reality in our living rooms? At the CRC, we cannot predict when it will happen, but we can easily predict that it will happen. Why? You just have to see it to believe it.