2010 Stereoscopic 3D Hardware Guide
By Neil Schneider
This is an introduction to modern stereoscopic 3D equipment for both the home 3D movie and video game consumer, and an explanation of technology used in the professional 3D cinema space. Members are welcome to point out additions or points we may have missed in this thread for a future revision.
It is important to recognize that this document is intended for 2D consumers interested in learning about stereoscopic 3D for the first time, and we are working hard to make the terminology and concepts as easy to understand as possible. We would also be grateful if members can contribute artwork to help convey what these technologies are about.
What is Stereoscopic 3D, and Why Should I Care?
How Does it Work?
What Can I Use Today?
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Where Are Things Headed? (Conclusion) 3D or “stereoscopic 3D” (S-3D) technology refers to media that displays images or content in a way that lets you perceive depth the same way you do in everyday life. 3D is very hot right now. All the leading Hollywood studios are releasing 3D movies in specially outfitted movie theaters, and revenues earned in 3D cinema is easily two to three times that of traditional 2D showings. Our industry’s latest victory is the movie Avatar, which has beaten Titanic’s record for being the best selling movie of all time! Why all the excitement? Why do these movies sell so well? 3D adds a superior level of visual beauty and immersion in a way that greatly enhances the film maker’s ability to tell stories – and this is not possible through other means. In our opinion, stereoscopic 3D technologies make experiences more memorable, and we are already seeing great promise in the educational fields. The flip side is a large consumer S-3D movement is in play, and in addition to being able to watch 3D movies, gamers are now able to enjoy their favourite titles in stereoscopic 3D. Samples of an S-3D gaming experience would be walking through a dark cave and actually seeing the depth in the back of the scene, or taking part in an action packed space battle, and seeing explosions flying out at you. These experiences are unique to stereoscopic 3D gaming, and are only now becoming realized. Unless you have a medical limitation, you are probably able to perceive 3D, and this is how it works: If you close your eyes one at a time, you will see that each eye sees a slightly offset view from the other. Your brain takes the images provided by your left and right eyes, and combines them into a single picture. This picture includes the depth we all take for granted.
All stereoscopic 3D displays work by showing each eye a unique and offset image. While there are several brands and products, they are all based on one or more of the following techniques: anaglyph, LCD shutter glasses, polarized projection and lenses, head mounted displays, and auto-stereoscopic 3D solutions. There is a wide selection of stereoscopic 3D solutions on the market, and here is a list of what is available by classification: All forms of anaglyph are based on the idea of filtering a unique image for each eye by separating the viewpoints with a selection of colors, and having the glasses differentiate the colors for each eye. Anaglyph is most often associated with “red/blue” glasses. Compared to modern solutions, this is considered the worst way to experience stereoscopic 3D. That said, it’s very inexpensive (possibly free!) and it works.
The viewer wears special anaglyph glasses, and each eye has its own lens: red for your left eye, blue for your right. The screen works in tandem by having a coordinated red and blue image. Between the glasses and the image, the red components are seen by one eye, the blue components are seen by the other, and the viewer gets a true stereoscopic 3D result. There are different techniques with different levels of complexity, but this is how things work at the simplest level. The downside of anaglyph is that after extended viewing, you may experience headaches, your brain will compensate by temporarily distorting your color spectrum, and the visual experience is not true to life. It is a misnomer to put the Dolby 3D stereoscopic 3D movie system in the anaglyph category, but it is often referred to as “anaglyph on steroids”. While Dolby 3D uses color to separate the left image from the right, this is where the similarity with anaglyph techniques ends. Dolby 3D places every color in each eye, and this leads to the required cinema grade color quality. The system chooses a red, a green, and a blue for the left eye (RGB), and a slightly different red, green, and blue for the right eye. With RGB, it is possible to project the entire color spectrum to each eye. In order for the color difference between eyes to remain unnoticeable, the viewers’ glasses have no less than fifty filters in each lens. When both eyes are open, the viewer’s dominant eye compensates for whatever minor color difference remains.
Dolby 3D’s biggest selling point is theater owners can maintain their traditional white screens, but the trade-off is the glasses have been criticized for being expensive compared to their polarized counterpart. While durable, the glasses also require cleaning with every showing. You can read MTBS’ interviews with Tim Partridge, Executive Vice-President of Dolby Laboratories HERE and HERE. There have been a few modern anaglyph options placed on the market recently. ColorCode 3-D and Trioviz are working examples. Using different choices of color filters, ColorCode 3-D and Trioviz can be viewed on almost any form of media including paper, screen, or projection. Unlike traditional anaglyph, the choice of filters makes the images comfortable enough to view in 2D, and equally viewable in 3D when wearing their glasses. While few have declared them as directly competitive with modern 3D displays, they have been used to help promote 3D movie releases like Monsters VS Aliens, and launch 3D magazine spreads, limited edition 3D television broadcasts (e.g. Chuck), and more. LCD shutter glasses have been available for several years now. Unlike anaglyph technology, they don’t require changing the screen’s colors to work.
These 3D glasses have an LCD panel that covers the entire eye. When a panel is on, it is completely black. When it is off, it is transparent. In practice, the left eye will be transparent when the right eye is black, and then the right eye is transparent when the left eye is black. The black phase is how the glasses blind each eye one at a time. Meanwhile, the screen is flashing two alternating images to coordinate with the glasses. An image for the left eye, an image for the right eye, and back again. When set up properly, this alternating pattern happens so fast that the viewer doesn’t see any flicker or strobe effects, and they benefit from a full color 3D image. LCD shutter glasses are sometimes referred to as “active glasses” or an “active solution” because they physically change and alternate to make 3D possible. The challenge with LCD shutter glasses is the rapid alternating between left and right images cuts the light levels in half. To get the same image quality you would normally get in 2D, you must double the brightness of your screen. There are three main avenues for LCD shutter glasses: LCD shutter glasses earned their start with old style CRT monitors. Once very popular, CRT monitors were replaced with much sleeker LCD panels. Unfortunately, these new LCD panels were not compatible with shutter glasses.
LCD shutter glasses are dependent on the refresh rate or the number of times the screen fully updates itself per second. If the refresh rate isn’t high enough, the viewer gets strobe effects, and the 3D becomes a nausea inducing experience. We know that a minimum of 60Hz per eye is required for comfortable viewing. The most popular LCD panels run at 60Hz, which translates to a gruelling 30Hz per eye once glasses are involved. It’s easy to understand why LCD panels were the near death of stereoscopic 3D in the home! Fortunately, LCD technology has come a long way, and many new panels coming to market support refresh rates of 120Hz or more! For the time being at least, the inexpensive nature of putting out 120Hz LCDs by default has made shutter glasses the dominant technology by TV manufacturers. For now.
Leading brands putting out 120Hz panels include Samsung, Sony, LG, and more.
NVIDIA has enjoyed a resurgence as well. With the help of proprietary stereoscopic 3D drivers and their own line of branded LCD shutter glasses, NVIDIA’s GeForce 3D Vision glasses have earned their share of coverage and following. We are also seeing consumer grade notebook computers with shutter glasses compatibility. The industry is heating up further with likely competition from combined AMD, Bit Cauldron, DDD, and iZ3D efforts. While a minority of manufacturers are going with plasma, there have been innovations in this field too. Similar to LCD displays, the latest plasmas offer 120Hz or better support, and also feature full 1080P resolution per eye.
While it is unclear if it’s plasma’s nature that allows for larger sizes, they have earned a lot of headline space for their grandiose exhibits. There are some single projector solutions that are popular among enthusiasts that work with LCD shutter glasses similar to the way CRT monitors work. Whereas before these projectors were targeted for business use, we are starting to see very affordable options in the consumer space.
Projectors are very exciting for gamers because they are one of the most inexpensive ways of getting a very large and immersive stereoscopic 3D image. Imagine life sized 3D monsters on your bedroom wall! That’s what S-3D projectors offer. The trade-offs with projectors include expensive bulb replacement and the need for space. However, their resolutions have climbed significantly, and 720P or higher is now very achievable in stereoscopic 3D. While 120Hz LCD panels have been well received, LCD shutter glasses owe their resurgence to DLP. Similar to CRT monitors, the screen alternates very quickly and projects two images. However, instead of rendering a complete image at a time, the resolution is cut in half and is handled in an alternating checkerboard pattern. This creates the illusion of the complete 2D resolution.
Fortunately, the nature of stereoscopic 3D reduces the importance of high resolution because of its volumetric nature, and the checkerboard solution does not have problems with under-detailed text that is hard to read the way interlaced solutions do. It also helps that 3D HDTV tends to be 40” or more in size, so the loss in resolution doesn’t impact the fine details the same way it would if the screens were smaller. However, as with all LCD shutter glasses solutions, there is a 50% loss of light because of the glasses’ alternating “dark phase” which the screens can’t fully compensate for just yet. While Checkerboard DLP isn’t as popular as it once was, some leading brands are still selling these units. While polarized movie theaters are dominant in North America, LCD shutter glasses are much more popular in Europe.
While movie theater glasses are less focused on aesthetics, they have the advantage of superior lens quality, long battery operation, and sharp synchronization. Technological innovation is happening in both theater and consumer markets, however. Polarized glasses work on the premise that light can be “vibrated” a certain way, and the glasses are able to filter this “vibration” to each of your eyes. This is sometimes referred to as a “passive solution” because the glasses have no moving or changing parts, and all the real action is happening on the screen or projector.
Polarized glasses have the competitive advantage of offering more brightness than LCD shutter glasses, and they can easily be shaped and sized to countless configurations as demonstrated above. There are five current methods for this technology: The consumer dual projector solution requires two aligned projectors with polarizing filters pointing to a single screen. The glasses filter these images based on their “vibration” signature, and the viewers get a complete 3D image. This is a favorite solution among technically inclined enthusiasts, but is also used on the big screen by IMAX 3D. With the exception of slightly darkened polarized glasses, there is little light reduction because there is no “black phase” on the glasses blocking out 50% of the light. This is also why IMAX 3D is able to show 3D movies on a very big screen. The trade off is the projectors can easily fall out of alignment, and the 3D effect can be greatly undermined when this happens. RealD uses a technology where a single projector creates two images and points to a single screen to make a 3D image, but how is this possible?
It is a similar idea to LCD shutter glasses where the screen alternately displays a left and right image very quickly and the glasses block each eye as needed. Instead of the glasses flickering on and off, there is a polarizer in front of the projector alternating between a left and right eyed filter. The audience’s polarized glasses filter these left and right images to each eye, and combined with the extremely fast rate that these images swap, you get a flicker free 3D image on the big screen. Similar to the LCD shutter glasses, the 3D trade-off is a 50% loss of light because of this flicker between images, so the screen image size has to be reduced to compensate. There is also a requirement for the theater owner to buy a special silver screen which is expensive and dampens the color quality. You can read MTBS’ interview with Joshua Greer, President of RealD and Elizabeth Brooks, RealD’s former Chief Marketing Officer HERE. To make a stereoscopic 3D image, there has to be two unique pictures projected to your eyes at the same time, or so quickly that they seem to appear at the same time. CRT monitors were popular because the screens could be updated very quickly for this purpose, but CRT technology is no longer in favor with consumers because it takes a lot of space, it’s heavy, and is not environmentally friendly.
120Hz LCD panels have quickly taken CRT’s place, but not everyone is comfortable with the shutter glasses experience. A popular way around this problem is to cut the vertical resolution in half with 50% of the lines devoted to your left eye, and 50% devoted to your right. A polarizing filter is then placed in front of the LCD panel to differentiate the left and right eyed resolution lines, and the viewer’s polarized glasses combine the images for a stereoscopic 3D result. High resolution is critical in 2D, but it isn’t as important for stereoscopic 3D. Even with the drop in resolution, a sharp interlaced image is very rewarding. Ghosting refers to cross-talk between the eyes, or an inability for each glasses lens to completely block out the image from the opposite eye. Current interlaced 3D monitors and HDTV solutions have very little crosstalk.
Another benefit is the light levels are very high compared to shutter glasses because there is no flickering between images or blocking the eyes in any way – with the exception of the slightly darkened polarized glasses. A challenge with interlaced 3D solutions is while graphics tend to look very good, small text can become difficult if not impossible to read. The problem is that half the vertical resolution interferes with the fine details lettering requires. This technology is resolution specific, so if your game requires a reduction in resolution to maintain performance, the image can’t be scaled to a larger size, and you will need to use a fraction of the screen space to get your games to work. DDD has a software work-around for this problem, but it is not a function of the hardware. In the case of large sized 3D monitors and HDTV solutions, the impact of these trade-offs are greatly reduced. While interlaced LCD technology manages to project a sharp image, professionals may need fuller resolutions for research purposes or gamers may be seeking even higher levels of detail. Instead of dividing the resolution of a single LCD panel between two eyes, an alternative is to take two full sized resolution LCD panels and project them on a central surface.
This scenario works in three parts: a. There is an LCD panel on top. The two LCD panels have polarizers and are projected to the center surface. The polarized eyeglasses filter each image from the center surface and the end user gets a nearly ghost free full resolution image. The trade off is one eye will be a bit darker than the other because while one image is projected on the center glass, the second image is projected through the center glass. This is a minor anomaly in exchange for a nearly cross-talk or ghosting free image. The biggest challenges are that the technology is very expensive and it takes a lot of physical space to be properly mounted. There are similar variations where the LCD panels are mounted horizontally instead of vertically. A final option is to have two LCD panels and a polarizer in a single monitor casing.
The technology works in three steps: a. The back panel projects a left and right full color image simultaneously and controls the intensity. This technology is advantageous because it offers full resolution results and takes nearly as little space as a traditional LCD monitor. There is no flicker between panels and it is a comfortable experience with little to no eyestrain. It is also very inexpensive compared to many of the other solutions in the market. In the case of the iZ3D monitor, there were trade-offs. When one eye was opened at a time, it was clear that there was some ghosting or crosstalk between the images. There was also a problem where one image was discolored compared to the other. The polarizers need to twist the light from 0 to 90 degrees to completely block and properly filter between the images, but LCD technology has inconsistencies when polarizing different colors. iZ3D’s solution was to develop new polarized glasses to compensate for this. The results are demonstrated below:
Head Mounted Displays, or HMD for short, is one of the oldest stereoscopic 3D technologies on the market. Unlike their predecessors, modern HMDs are lightweight helmets or headbands that place miniature screens directly in front of the viewer’s eyes. By having the screens directly in front of their eyes in an enclosed environment, the viewer is left with the illusion that they are seeing their favorite games or movies with a very large screen. While this illusion is subjective, head mounted displays are considered one of the most immersive stereoscopic 3D experiences possible.
They benefit from full color immersion and absolutely no ghosting because each eye is getting its own personal screen. Modern HMDs often include additional features like earphones and head tracking that adjust the game’s perspective as the viewer’s head moves. There are a few trade-offs with this technology, though. To date, the highest resolution consumer HMD solutions are 800X600 and 640X480 pixels per eye. While still impressive to see, modern gamers are used to much higher pixel counts. There have been few innovations to get around this problem. The nature of an HMD’s immersion also causes nausea for the inexperienced gamer. When we move our heads, our brain expects our vision to correlate with our movement. When we are wearing an HMD, and the image doesn’t change according to where our brain thinks our eyes should be looking, this incongruity creates nausea. Head Mounted Displays are one player at a time technology – so don’t expect to be sharing the experience with a group of friends at the same time. Though, having a movie theater to yourself isn’t so bad, either! Finally, believe it or not, ghosting has its benefits. When playing video games and determining the best settings for game play, it’s much easier to see with the naked eye what 3D proportions are best because the viewer can see both images at the same time and understand how they relate to each other. Since there is zero ghosting with HMD solutions, there is no reference point to do these adjustments. It is therefore important that the software drivers give some kind of visual cue on how the S-3D settings are being handled to ensure comfortable results. It’s actually very amazing. When this guide was first written, we lived in a world where CRT monitors were the leading S-3D solution, LCD monitors were the enemy, and 3D HDTVs were few and far between. What began as prototypes are now committed release products. In the June, 2008 release of this guide, we remarked: “Similar to the way Bill Gates expected Windows to be on every desktop, MTBS was founded on the expectation that stereoscopic 3D, in one form or another, will be on every desktop and in every living room. Given the wide selection of available technologies, let alone the multiple name brands getting involved with this growing industry, it should be clear that S-3D is quickly developing into a form of mass market media.” How right we were!
A number of standards have already been establushed. First, the connections between content peripherals and 3D HDTVs have been finalized via HDMI and DisplayPort.
The Blu-Ray Disc specification is complete, and 3D movie content for the home has already been commited.
We are also please to report that the S-3D Gaming Alliance (S3DGA) has been picking up steam, and we anticipate similar success in the stereoscopic 3D gaming markets. So far, so good! Given the drastic differences between this guide and the last, we can’t help but wonder what the future has in store. Please post your thoughts on this guide, and feel free to suggest additions and corrections if needed. |
