Close enough to touch

On January 31, 2010, several hundred British soccer fans were able to watch the English Premier League’s top Sunday match between Arsenal London and Manchester United in a completely new way when BSkyB began testing a new 3D channel. To this end, the company equipped nine pubs around the country with special giant screens. As a result, viewers were able to experience passes, shots, and goals in spatial depth, as the playing field was optically “extended” into the pubs and the players seemed close enough to touch.

Human beings are able to perceive their environment in three dimensions because their eyes always simultaneously transmit two images to their brains, which then translate the angles of view into the three geometric dimensions of length, width, and depth.

The eight 3D cameras that were installed by BSkyB around the soccer stadium for the 3D premiere all work according to the same principle. Each camera is equipped with two lenses set roughly as far apart as the eyes of an adult. The cameras thus record parallel images — one for the right eye and one for the left. BSkyB TV vans broadcast these images throughout the country, but only the guests in the nine pubs were actually able to experience them in 3D. That’s because they were viewing them on special liquid crystal flat screens that simultaneously displayed the two “eye” images. The images had been polarized in a manner that enabled the fans to correctly perceive the left and right images with the help of 3D glasses. Polarization refers to the direction in which a wave of light oscillates. The use of glass embedded with optical gratings that allow only vertically or horizontally oscillating light waves to pass through makes it possible to filter light waves.

Television screen manufacturers were delighted about the public premiere of 3D TV, as they had been looking forward to it for a long time. That’s because the turnover generated by the sale of LCD TVs fell for the first time in 2009 after years of rapid growth that began at the beginning of the decade. Manufacturers therefore hope that the 3D-enabled LCD variants will revive the market. Indeed, market researchers predict that around 64 million 3D LCD televisions will be sold each year by 2018. Such units will require 3D content, however.

 
3D films can be produced in different ways. The polarization technique that BSkyB is using for its pilot project was actually developed at the end of the 1930s as an alternative to anaglyph images viewed with red-green glasses (see box with background information). The glasses for both techniques are relatively cheap because they don’t require any electronic systems. However, they do have a disadvantage: Both methods reduce the image resolution, which lowers the brilliance and the sharpness of contours. That’s because showing the images simultaneously requires the image for the right eye to be displayed over the first, third, fifth etc. row of the screen, while the image for the left eye is shown on the second, fourth, sixth etc. row. This cuts in half the number of pixels displayed per image.

That doesn’t happen with 3D films viewed with shutter glasses. In this case, images are displayed one after the other rather than simultaneously. A TV screen that operates with a 100 Hz refresh rate generates 50 images per second for each eye, for example. Shutter glasses, which are linked to the screen via an infrared antenna, alternately dim the left and right eye as the images appear, which means that each eye sees the image at full resolution.

The problem is that even at a refresh rate of only 50 Hz, viewers still see an annoying flicker at certain viewing angles. This effect occurs when the change of image occurs so slowly that the inertia of the eye can no longer ignore it. As a result, monitors with a refresh rate of 100 Hz are insufficient in combination with shutter glasses. Higher frequencies are preferable, and televisions that operate with 200 Hz are already available on the market.