If the mythical Greek Cyclops—the giant with a single eye—had existed, 3D displays would have been wasted on him. The reason we see in 3D at all is because each of our eyes receives a slightly different image from a given scene, simply because they’re not in the same place. 3D vision is made possible by the 3 inches or so that separate the eyes.
Early 3D gimmicks included book covers and postcards. As you change your viewing angle by tilting these objects from side to side, the image seems to change. A “lenticular lens” makes this possible. It’s an array of very thin, cylindrical magnifying lenses, or lenticules, set out in rows, made from a sheet of plastic.
Stereoscopic 3D effects were introduced in films during the 1950s. Images comprised two superimposed, slightly offset colour layers. By wearing so-called “anaglyph” spectacles that placed a different filter over each eye, usually red for one eye and green for the other, it was possible to give the impression of a 3D image.
It was a short-lived fad, not least because of the geeky look the glasses imparted to users. Viewers who wore normal spectacles found additional problems using the anaglyph versions. However, there has been a recent resurgence of interest in 3D viewing, at least in part due to the highly acclaimed 3D movie Avatar from James Cameron.
Viewing glasses are normally needed to watch television in 3D. They come in active and passive versions. The active ones are battery powered and use moving or switchable elements to deliver a different image to each eye.
The effective refresh rate of the TV image is halved, meaning that 3D-ready TVs need a minimum refresh rate of 120 Hz to prevent image flicker. Active shutter TVs are now in production by both Sony and Panasonic, some with refresh rates of up to 240 Hz.
Passive polarised glasses, like their early counterparts, rely on an optical material to help distinguish between the images delivered to each eye and can only be used with front-projection systems. This means they’re easier to use with projected images, but the technology is difficult to implement in flat-screen TVs. They don’t work with mature display technologies such as LCD, plasma, or DLP, but Korean manufacturer LG is backing this technology.
3D TVs, electronic games, and even mobile phone displays that don’t require users to wear special glasses are now beginning to appear. Perhaps surprisingly, many of them rely on the earliest 3D technology—lenticular lenses.
Dubbed “autostereoscopic,” these television screens consist of a lenticular-lensed flat screen that projects slightly different images at different angles so our eyes can receive offset images that our brains interpret as 3D images. Philips and LG are both producing TVs with lenticular lenses. A similar technology known as “parallax barriers” has been pioneered by Sharp.
The challenge for 3D TV designers has been to overcome poor resolution and narrow viewing angles. Viewing angles are determined by the maximum angle at which a ray can leave the image through the correct lenticule. In 3D TV viewing, angles of just 20° are typical, outside of which viewers see double images on the screen.
At CEATEC 2011, Asia’s biggest consumer electronics show, Toshiba unveiled an LCD 3D TV capable of 40° viewing angles, an achievement made possible by using software to optimise light emission from the centre, right, and left of the screen, according to the company. Clearly, semiconductor processing power applied to decades-old lenticular technology is enabling 3D TV.
In the case of the Toshiba TVs, which were shown in 12-inch and 20-inch models, the final image has a resolution of 1280 by 720 pixels. But an LCD panel of 8.29 million pixels is necessary to achieve this resolution because nine separate images are created and transmitted in the required direction through the lenticular overlay. The image processing engine is a Cell microprocessor developed jointly by Sony and IBM.
At this year’s Consumer Electronics Show (CES) in Las Vegas, Toshiba also demonstrated a tablet PC with a 15.6-inch lenticular display that “when calibrated” produces a 3D image without the need for glasses. The clever part here is that the notebook’s camera detects the angle at which you are viewing the display and then dynamically calibrates it for the best 3D experience.
Nintendo’s 3DS gaming console, launched earlier this year, allows gamers to watch 3D effects without glasses. Its screen is manufactured using parallax-barrier technology developed by Sharp. A parallax barrier works in a similar way to polarising glasses and directs the light from two images slightly differently. The “sweet spot” for 3D viewing is about 20 inches from the screen.
Along with the narrow viewing angle, this means only one person can play the game at any one time, but the screen is switchable between 2D and 3D mode. Some U.K. newspapers have reported that the Nintendo 3DS has caused dizziness, headaches, and nausea. Time will tell if that’s true, or if it’s just caused by excitement surrounding the new technology!
It will be interesting to see if 3D display technology is now here to stay or if interest in it will, once again, fade away.