3D--How Does It Work?
3D is based on the principle of stereoscopy, which creates the illusion of depth in an image. The easiest way to enhance depth perception in the brain is to provide the eyes of the viewer with two different images, representing two perspectives of the same object, with a minor deviation exactly equal to the perspectives that both eyes naturally receive in binocular vision.
There are currently three kinds of 3D technology on the market and each one works differently:
The first one, anaglyph technology, is the most famous one (think red/blue paper glasses) but usually the 3D effects are not so great.
The second one, polarized (or passive) technology, is the technology you have been exposed to when watching a 3D movie in an IMAX theater (e.g. Avatar 3D, Alice in Wonderland 3D, etc.)
The third one, active technology, is the most recent one that is quickly becoming the standard in terms of 3D watching at home.
Let’s learn more about each of these technologies....
Anaglyph Technology:
Is 3D new? Not at all.
For the longest time, mankind has been interested in creating a 3D effect on a 2D screen. Most painters created some effect of perspective in their paintings to simulate a 3D effect.
More recently, in 1853 Wilhelm Rollmann developed a technique to simulate 3D. He created anaglyph images using two color layers superimposed but offset with respect to each other to produce a depth effect. Usually the main subject remained centered while the foreground and background shifted laterally in opposite directions. When viewed with two-color glasses (the lenses are chromatically opposite in color usually red and cyan), these images produced a stereoscopic 3D effect (your brain is tricked into thinking that this picture is in 3D).
This technology has been used countless times in movie theaters, as the typical red and blue glasses are inexpensive. The movie Bwana Devil is regarded as the first of the commercial 3D movies in the 1950s. However, while the 3D effect were fun to watch, the pictures were of low quality and had strong shades of green and red.
Most DVD and Blu-ray Discs currently on the market use this technology.Polarized (or Passive) Technology:
This is where it gets interesting. Most of us have seen Avatar or other movies in IMAX 3D with polarized 3D glasses. These glasses create the illusion of three-dimensional images by restricting the light that reaches each eye, creating a stereoscopic, or 3D, effect.
To create that 3D effect, two images are projected onto the same screen through different polarizing filters. The viewer wears low-cost eyeglasses which also contain a pair of different polarizing filters. Through the filters, each eye sees a different picture (each filter allows the light which is similarly polarized and blocks the light polarized in the opposite direction). This is used to produce a three-dimensional effect by projecting the same scene into both eyes, but depicted from slightly different perspectives.
The great thing about this technology is that the glasses you need to wear to enjoy 3D are really cheap (between $1 and $10 per pair); however, most believe that the 3D effects generated through this technology are not as sharp as the ones generated through a display with active technology.
Active Technology:
This technology has been adopted by most consumer electronics firms, including LG, Samsung, Panasonic, and more. With this technology, an HDTV will display one image to your left eye and one image to your right eye. Since the effective frame rate is halved, these HDTVs need to have double the refresh rate of HDTVs (60 Hz). This is why you will find that all 3D HDTVs have a minimum frame rate of 120 Hz (most have a frame rate around 240 Hz or even 480 Hz).
Active liquid crystal shutter glasses are then worn by the viewer and quickly block each eye in sequence to ensure that each eye only sees the corresponding image being displayed on the 3D TV set. The active shutter glasses are kept in sync with the HDTV using Bluetooth, infrared, or radio technology. These special glasses usually contain liquid crystals that can be made opaque, thus acting as a shutter. These glasses are battery-operated (battery life estimated at around 80 hours or so).
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