Fiction turned into Fact: 3D Television
Television, like most technology, has evolved since its debut. First, there was the switch from black and white to color TV. Then manufacturers began to offer televisions in larger formats using various projection methods. Over the last two decades, we've seen LCD and plasma technologies advance to the point where you can go out and buy a 61-inch (about 155 centimeters) television that's only a few centimeters thick. And high-definition television (HDTV) provides us with a picture that's so vibrant and sharp it's almost as if we weren't looking at a collection of pixels.
So what's next in television technology? Now that you can practically replace a wall with a screen and watch movies in high resolution, where do we go from here?The answer may end up right in front of your face or at least appear to be there, anyway. We're talking about 3-D television.Audiences first got a glimpse at 3-D technology way back in 1922 with the release of "The Power of Love." Whether they thought it was a curious thing or not is lost to history. But that began the somewhat cyclical fascination with three-dimensional film.
The next big boom in 3-D happened in the 1950s. That era introduced the world to dozens of B movies that relied heavily on odd gimmicks. Movie producers wanted to find ways to lure audiences away from their television sets and into the theater. Their schemes ranged from installing vibrating plates in theater seats to simulate an electric shock to sliding an inflatable skeleton down a zip line during the film. In comparison, wearing a pair of goofy glasses was pretty tame.
Several television episodes and specials have appeared in 3-D. There's also a market for 3-D DVDs. For the most part, 3-D hasn't made a big impact on the home entertainment industry. But if some of the most popular exhibits at the 2009 Consumer Electronic Show are good indicators, we may soon be reaching out to try to touch the images on our televisions in the near future.
Let's learn more about how we perceive objects in three dimensions.
Techniques Used In a 3D Television
- 3D ALTERNATE FRAME SEQUENCING
3D Alternative Frame Sequencing film is recorded with two cameras like most other 3D films, but, rather than having two projectors producing separate images for each eye like used in Polarization, the images are placed into a single strip of film in alternating order. In other words, there is the first left-eye image, then a right-eye image, then the next left-eye image, followed by the corresponding right-eye image and so on…!
The film is then run at 48 frames-per-second instead of the traditional 24 frames-per-second and the audiences wear very specialized LCD shutter glasses/3D active glasses which have lenses that can open and close/darken and lighten in rapid succession. The projection system has a transmitter that tells the glasses which eye to have open/darkened and the glasses switch eyes as the separate frames come on the screen.
Sony’s latest 3D TV Release uses alternative frame sequencing but at present it's unclear as to which manufacturers will also take up this technology or whether they will go in favor of 3D Polarization.
- 3D AUTOSTEREOSCOPY
Autostereoscopy is a method of displaying three-dimensional images that can be viewed without the use of special glasses. The methods produce depth perception even though the image is produced by a flat screen.If the viewer positions their head in certain viewing positions, they will perceive a different image with each eye, giving a stereo image. Unfortunately as great as this sound, sometimes eye strain and headaches can be side effects of long viewing exposure to autostereoscopic displays. Some displays can have multiple viewing zones allowing multiple users to view the image at the same time.There are a number of companies developing autostereoscopic 3D displays with most notably the advances made by Phillips having produced good results. Philips released the first 3D HDTV autostereoscopic display with a 2160p resolution and 46 viewing angles & Hitachi has also released the first 3D mobile phone for the Japanese market using this technology.
- 3D Anaglyph
3D Anaglyph in comparison to other technologies is reasonably old as it was first developed in the late 1800’s and is very rarely used today.It provides a 3D effect when viewed with 2 color glasses (each lens a chromatically opposite color, usually red and cygan (blue-green). Images are made up of two color layers, but they are offset with respect to each other to produce a depth effect. Usually the main subject is in the centre, while the foreground and background are shifted in opposite directions.Similar to that of Polarization the visual cortex of the brain then fuses this into perception of a three dimensional scenes or composition.3D Anaglyph Technology will not be the technology used in 3D going forwards with much improved Polarization or Alternative Frame Sequencing taking its place. It does however still have its fans and is often used for childrens entertainment often in the form of 3D picture books.
Autostereoscopic 3D television sets work on a principle of lenticular lenses and parallax barrier.
- Lenticular lenses
The less popular of the two autostereoscopic models involves the use of lenticules, which are tiny cylindrical plastic lenses. These lenticules are pasted in an array on a transparent sheet, which is then stuck on the display surface of the LCD screen. So when the viewer sees an image, it is magnified by the cylindrical lens.To see how this works, roll up a newspaper or magazine into a cylindrical shape and hold it up in front of you. Now, with your other hand, cover your left eye. Notice the text and pictures that your right eye can see. Then uncover your left eye and use your hand to obstruct your right eye. Naturally, given the two varying angles, you will see a bit more of text and pictures on the extreme left side when you look with your left eye, and vice versa. By combining these two images, our brain can perceive depth. Similarly, when you are looking at the cylindrical image that the TV is now showing you, your left and right eye see two different 2D images, which the brain combines to form one 3D image.However, lenticular lenses technology is heavily dependent on where you are sitting. It requires a very specific ‘sweet spot’ for getting the 3D effect, and straying even a bit to either side will make the TV’s images seem distorted. Depending on the number of lenticules and the refresh rate of the screen, there can be multiple ‘sweet spots’.
- Parallax Barrier
The other major method to enable autostereoscopic output is called the parallax barrier. This is being actively pursued by companies such as Sharp and LG, since it is one of the most consumer-friendly technologies and the only one of the lot which allows for regular 2D viewing.The parallax barrier is a fine grating of liquid crystal placed in front of the screen, with slits in it that correspond to certain columns of pixels of the TFT screen. These positions are carved so as to transmit alternating images to each eye of the viewer, who is again sitting in an optimal ‘sweet spot’. When a slight voltage is applied to the parallax barrier, its slits direct light from each image slightly differently to the left and right eye; again creating an illusion of depth and thus a 3D image in the brain.
The best part about this, though, is that the parallax barrier can be switched on and off with ease (one button on the remote is all it would take, according to Sharp), allowing the TV to be used for 2D or 3D viewing. So on a computer monitor, you could play video games in full 3D glory and then easily switch to 2D mode for your work requirements.While the wide range of content it offers is heartening, again, the need to sit in the precise ‘sweet spots’ hampers the usage of this technology.Still, there are quite a few companies finally looking to make 3D TVs a reality. In the upcoming third part of this series, we will take a look at some of the brands and products that promise to bring next-gen content to your living room
Several things are clear. The higher the quality of the pictures, the better is the 3D TV. This is not the place for loss of resolution or compression artefacts. This must be factored into plans. All 3D TV systems have the potential to cause eyestrain. It can be minimised only if we pay attention to detail all the way along the production and delivery chain. But the viewers’ cannot watch 3D TV for very long continuous periods, unless he is a seasoned 3D TV viewer with eyes accustomed to the optical gymnastics needed else can view it for an hour or two at most. 3D TV can have a lot of impact, but it is not true complete natural vision..