Best 3D Glasses – Passive Polarized vs Active Shutter 3D technology
3D glasses form a vital component of current 3D Display technology enabling stereoscopic vision and depth perception. As explained in greater depth in the 3D TV technology guide, we are able to perceive depth due to the fact that each of our eyes observes the same scene but at a slightly different perspective. When the individual images being viewed by each eye reaches our visual cortex, our brain automatically puts these images together and interprets information regarding the third dimension. Try tossing a ball back and forth with a friend with one eye shut and you will realize just how important the second eye is for us to perceive depth.
Panasonic's Active Shutter 3D Glasses
Thus, ultimately any 3D display technology will rely on using a method to deliver separate images (or views) of the same scene to each eye. 3D glasses provide a very simple and elegant approach to achieving this. The idea behind them is simple enough, each eye piece allows the image meant for the corresponding eye to pass through while blocking the image meant for the other eye.
3D Glasses can be divided into two primary technologies, Active and Passive. Active glasses are usually powered and involve moving or switchable elements in the glasses that “actively” discriminate the incoming image so as to provide a different image to each eye. In direct contrast, Passive glasses do not rely on any powered or movable elements. They usually rely on some special type of optical material that helps discriminate between the images meant for each eye.
Active Shutter 3D Glasses
Active shutter glasses are currently a very popular choice amongst consumer electronics giants who are investing in 3D display technology. The primary reason for this is that this technology requires a very minimal modification to current HDTV displays and as a result it is much easier to develop and perfect. The individual eye pieces of these glasses incorporate liquid crystals and a polarization filter so that when a voltage is applied, the glass turns dark and prevents light from transmitting through. Thus the left and right eye glass can be shuttered alternatively in this manner and this shuttering effect is synced with the refresh rate of the display. The 3D TV displays a frame for the left and right eye alternatively and the sync with the active shutter glass ensures that each eye only ever views the image it is meant to see. As is probably evident, because of the way these displays work, the effective refresh rate of the TV is halved. This is why 3D Ready TVs have to have a minimum refresh rate of 120 Hz (meaning 60 frames per second for each eye).
So how will Active Shutter Glasses affect your 3D experience? Well, it is actually a very simple and elegant solution to providing stereoscopic vision using existing display technology. The pros and cons of this technology is listed below and will probably help answer some of your questions.
Advantages of Active Shutter Glass Technology
- Probably the cheapest 3D technology in the short term. This is because this technology only needs a refresh rate enhancement for current LCD and Plasma TVs, something that isn’t too hard or expensive to do. In addition a syncing unit will be required to sync the TV to the active shutter glasses
- Lower price point does not come at the expense of 3D image quality.
- Backward compatible with some of the high-end 3D capable TVs that were sold in 2008 and 2009
- Displays are based on very mature LCD, DLP and Plasma technology which means that most of the quirks are already ironed out and prices shouldn’t be prohibitive.
Some drawbacks of Active Shutter glasses
- The constant shuttering might bother some who are very sensitive to low refresh rates and cause flickering. This will be true of the lower end 120 Hz displays which only provide an effective refresh rate of 60 Hz. However, 3D display manufacturers have already announced many TV models with refresh rates of 240 Hz and even 480 Hz! These high refresh rates will easily get rid of any such complaint one might have of the 120 Hz displays
- Glasses are battery powered. This is one major drawback that is not particularly easy to alleviate. Due to the nature of the technology the glasses need to apply a potential to “shutter” the glasses. It also needs additional power to communicate and sync with the TV. Running low on batteries while watching a movie will surely be a very annoying experience. So if you are planning to buy one, be prepared for this. It shouldn’t be hard to deal with though. It’s just like your PS3/XBOX360 wireless controllers to be honest. Just set them up at the charging dock when you aren’t watching 3D television, and that should make sure that they are charged and ready to go when you need them
- While the 3D displays using this technology will be inexpensive themselves, the glasses will be more expensive than their passive counterparts due to their complexity. This means that it might be a bit prohibitive to own many active shutter glasses for when you have friends come over to watch a 3D movie. However, it is most likely that they will be well subsidized by the display manufacturers in an effort to encourage widespread 3D TV adoption.
That pretty much sums up the active shutter technology and its pros and cons. It is definitely the most mature 3D technology at the moment when it comes to personal 3D capable home theater systems for the home user and promises a fantastic 3D experience.
Passive Polarized 3D Glasses
The simplest passive 3D glasses that most of us are all familiar with are color anaglyph glasses…those cheap red-green or red-cyan glasses that you have used at some point or the other. These glasses do not have any “active” or powered components on the glasses. Instead, they rely some optical effect to discriminate between two images projected on a screen, each meant for a different eye. In the case of anaglyph glasses, the images for the left and right eye were projected using two projectors on the same screen and due to the color tints on each eye piece, a separate image was delivered to each eye. However, this technology has severe limitations, chief amongst them being the poor color fidelity due to the use of tinted glasses. The muted colors lead to a very surreal, uncomfortable and visually jarring 3D experience which prevents the viewer from being immersed in the 3D environment.
More recently, there has been resurgence in Passive 3D Glasses technology due to technological progress that has enabled Digital projectors such as those used by RealD and IMAX 3D to display commercial movies at movie theaters in true 3D. These systems rely on exploiting a property of light called polarization. If you are interested in the details of this technology check out my article explaining how 3D TV technology works. To explain it very generally, this technology relies on discriminating between two images projected on the same screen by 2 separate projectors based on the polarization of the light used to project the image. As shown in the figure below, when light of one polarization encounters an eye-piece that is polarized in the opposite direction, it cannot pass through. On the other hand, if both the lens and the light have the same polarization, then the light passes through the lens unimpeded. Thus, each eye piece has the opposite polarization and the image projected on the screen consists of two images, each possessing a different polarization and perspective, meant for one eye. In this manner, a separate image is delivered to each eye.
In commercial 3D projectors used in theaters, the projector technology relies on Circularly polarized light which works in a similar manner but also allows the viewer to tilt his or her head without degrading the image quality. These projectors also save on costs since they can alternatively generate right circularly polarized and left circularly polarized images in rapid succession without the need for two independent projectors.
We have listed the advantages and some of the disadvantages of this technology below
Advantages of Passive Polarized 3D Glasses
- Provides excellent rejection between the left and right eye views thus getting rid of any ghosting issues in the 3D videos
- Guaranteed flicker free 3D experience
- Provides amazing visuals and very rich colors
- Passive 3d Glasses are extremely cheap. You can easily stock up on them if you are planning to have a big Super Bowl party where you want to show off your fancy 3D TV. Additionally, there is a good chance that the glasses you kept from when you went to the theater will actually work for your passive polarized 3D display
Some disadvantages to keep in mind
- This technology is currently limited to front-projection systems. This means that it is easier to use in projectors but hard to implement in regular flat screen 3D Tvs. This is primarily because it is very hard for the light to retain it’s polarization property when it interacts with a screen. For front-projection systems, a special silver screen is used to reflect the light while maintaining the polarization of the projected images.
- This projection technology is currently very expensive and will appeal only to the hardcore 3D addicts out there. Silver screens aren’t cheap either!
- This technology is not compatible with current mature display technologies such as LCD, Plasma and DLP. This means that any new technology that is developed will still be in “Beta” mode and will probably take a couple of years before the kinks are ironed out.
The Verdict
So which type of 3D display technology should you go with? As things stand at the moment, we would very strongly recommend Active Shutter based 3D TVs. As listed above, this is based on very mature and robust display technologies and will also be very competitive when it comes to pricing. While passive polarized glasses are attractive in their passive nature, this display technology will still take a few years to mature before it will truly challenge active shutter based systems. Of course, chances are that in the next few years someone will develop a 3D TV that doesn’t require glasses… Well, at least we can hope that they do 
.
Related Articles you might find interesting
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How 3D TVs work
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A Guide to help buy 3D TVs
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What is Frame Sequential 3D?
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3D Ready TV Guide
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Plasma vs LCD 3D TV
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about 5 months ago
Shutter glasses are undoubtedly the best option for the forseeable future, but eventually passive polarized glasses will replace them – here’s why.
Even if the active glasses eventually end up as cheap as passive ones, (unlikely), their real disadvantage is that are necessarily tied to one display. Right now it’s easy to see 3d as the next thing after HD to enhance large screen tv’s, but 3d is different. HD is inextricably linked to large screens, but 3d is like color – it enhances any image of any size or resolution. Already there are 3d monitors and laptops, even 3d mobiles in Japan. Yes, some of these use shutter glasses, but again that only really works as long as you have one one 3d screen to look at. Ten years from now you will probably struggle to find a device of any kind with a screen that is 2d only, just as now there are almost no monochrome devices on sale. Passive polarized glasses can enable you to view multiple 3d devices simultaneously with no problem.
There are already a few LCD tv’s that use them. They are sold under the Hyundai name, though made by Arisawa of Japan. The problem is that they halve the vertical resolution, so you only get 540 lines per eye from a 1080 picture. The solution is obvious – a 2160 line screen! For the time being, however, it’s a lot easier and cheaper to double the frame rate than the resolution. That’s why shutter glasses are really the only game in town for now.
about 5 months ago
Very nice comment Richard, and I do agree with you. The fundamental drawback is indeed the lack of a standard shutterglass for all 3D displays coupled with the need for the 3d glasses to be powered.
As you mentioned, current polarized methods for LCDs suffer from the halving of the resolution. The other drawback (I could be wrong) is that most of these displays rely on linear polarization at the moment, which has its own set of drawbacks. Until they come up with a good circularly polarized solution for regular flatscreen 3D TVs, and one that is competitive in price with regular high refresh rate LCD/Plasma screens, I would imagine that active shutter will dominate.
A small price premium for Circularly polarized displays would work fine as users could recoup the cost by virtue of the ultra-low prices of passive 3D glasses. It is certainly an interesting battle to keep an eye on.
about 5 months ago
My point was not simply the issue of standardization – that is fixable in principle. The real issue is ‘What happens when there are multiple 3d screens within your field of view?’ Imagine you’re working on your 3d laptop while across the room someone if watching Avatar on the 50 inch tv. What chance that your shutter glasses will be perfectly synched with both ? Imagine trying to work while the tv drifts in and out of synch with your glasses. Nightmare.
The manufacturers are doing absolutely the right thing to rely on the shutter glasses to get the ball rolling. What is needed longer term is circularly polarized, double resolution screens at a reasonable price, and that is still a few years away.
about 5 months ago
That is true, I guess I didn’t consider the scenario of a 3D laptop + regular screen. I don’t know how popular 3D laptops will be though, as I can see people being enthusiastic about putting on a pair of glasses to view a movie on their hometheater system, but not so much to just work on their laptop.
I highly doubt that people will be walking around the house with their polarized glasses at all times so they can glance at the programming while working in the kitchen, etc, and enjoy the 3D.
However, I do agree that it would be best if circularly polarized systems are more widely adopted in the future. Ultimately, it would be awesome to have true Holographic displays
. As for Glassless 3D displays, I’m not yet convinced that there is any one technology out there that can overcome the basic viewing angle/distance limitations of current lenticular displays.
about 5 months ago
Last Wednesday Madison Square Garden broadcast a live 3-D (Side-By-Side encoded) NY Rangers hockey game. I was lucky enough to get to see it on a front-projected screen, a Panasonic (Active-Glasses) Plasma, a Samsung (Active-Glasses) LCD and an LG-not for sale in the US-polarized LCD set. The sets use the same glasses that theaters are using and creates 3-D by decoding the side-by-side into interlaced lines with the LCD is manufactured to create interlaced polarization. The result was crisp, bright 3-D with no ghosting whatsoever, even in the high-contrast fast movement of a hockey game. While the effective resolution of the 1080i picture was reduced to 960×540 by the side-by-side encoding, the image was impressive. Now if they would only offer the technology in the US…
about 5 months ago
Hi Lou,
Thanks for stopping by to comment and leave us with that info. That sounds awesome! Any idea why the LG polarized TVs won’t be on sale in the US, and where they will be available? That is great news though, as I think it would be awesome to have Passive 3D displays using Circularly polarized glasses.
Perhaps they are waiting till they can enhance the screen resolution so they do not end up halving the vertical resolution of the 3D content. As you correctly pointed out, side-by-side to interlaced polarized conversion results in a halving of both the vertical and horizontal resolution, which is far from ideal. It is good to know that the 3D experience was still great.
To be honest, at this point it looks like resolution is less of an issue compared to good picture quality, flicker free 3D, and lack of ghosting and cross-talk.
about 5 months ago
In regards to the image resolution comment, the shutter glass technology has the potential to provide better resolution and in the immediate future, it can do it from 3D Blue-ray content (full 1920×1080p60). However, from broadcast 3D content, the resolution is going to be half, either in the vertical or horizontal resolution, because of the nature of the frame compatible formats (side-by-side, over/under). So for watching broadcast content, passive or active glasses displays should provide similar perceived resolution, until broadcast 1080p60 is introduced in the market.
On a different note, I don’t know much about how the brain works with images. I seems that even though each eye is getting half resolution images, the brain is getting input from both eyes. I don’t think half + half will make full resolution because something should be lost in the translation, but I don’t think is half resolution either. It may be somewhere in between.
about 5 months ago
Hi Steve,
Thanks for stopping by to comment. While side by side or over/under might not sacrifice the resolution for passive displays, keep in mind that if your source is side by side but your display has horizontal alternate strips of polarized pixels, then you will effectively have half the resolution in both horizontal and vertical.
With regards to our vision, it is important to note that each eye sees the same resolution. We don’t actually double our resolution by viewing with one eye. In that case things should look half as sharp if we closed one eye
To be honest, side-by-side doesn’t look too bad unless you are watching it on a HUGE TV. Many of us are still fooled by 720p and 1080p images on regular HDTVs.
about 5 months ago
Passive is FAR superior. It really is a no brainer.
The biggest problem with active is the flicker is absolutely horrible. It will take a MINIMUM of over 400Hz refresh to make it remotely acceptable. When people saw flicker on 60Hz CRTs, this is because the picture was fading, not to 100% black, but lets say 80% of the way there during the 1/60 of a second between frames. A switch completely to black every time the shutter blocks an eye will be obvious and painful even with it only for around 1/200th of a second.
Active shutter is an old technology. They had it for the PC, supporting both Voodoo and NVidia video cards, in 1998 with a product called WickedVision. It was a cool gimmick in the 90’s, but it came with 3 pages of warnings because of how disorienting the flicker and double images (due to incomplete image transitions from one eye to the other) are, especially with fast action games. It actually said not to drive or operate heavy machinery for at least 4 hours after using it.
Passive polarized glasses based 3D has been affordable for the PC user for 5 years now with monitors polarized for passive 3D glasses like the 22″ iZ3D selling for under $300.
Having alternate polarization for each pixel does not need to lower your resolution. The screen can simply be 1920×2160 instead of 1920×1080, so there is 1920×1080 for each eye (or each pixel doubled in 2D mode).
about 5 months ago
One more thing. For broadcast 3D I hope to god the FCC gets with the 21st century and says that any 3D broadcast should be ATSC 2.0 not ATSC 1.0, the key difference being that the 2.0 spec says all receivers must support H.264 rather than just MPEG-2. The compression artifacts on U.S. TV broadcasts are already terrible, especially at 1080i, because MPEG-2 simply can’t handle that resolution inside of 19Mbps bandwidth (really more like 15-16Mbps allowing room for SD subchannels). Trying to fit 2 MPEG-2 feeds in that bandwidth for stereoscopic broadcasts will make the artifacting really horrendous unless they upgrade to a better codec like H.264, which Europe and Satellite providers already use even for 2D TV.
Particularly for scenes with lots of action (who watches 3D movies with no movement?), the difference in compression ratios for the same quality MPEG-2 vs. h.264 can be 20:1 (with low amounts of movement its more like 5:1).
about 5 months ago
@gluglug,
Regarding Passive technology, yes, it is better in that it allows for strain free viewing and no chance of flickering issues. However, the fact remains that at the moment it is more expensive as it requires (a) A higher resolution than Active shutter based displays and (b) A fundamental change in the way the display is mass produced.
Both these factors mean that these displays will cost quite a bit more to produce than active shutter based displays that only require a syncing unit and a high enough refresh rate. This is why manufacturers have adopted it for now. As prices come down and the technology evolves, I’m sure we’ll see more passive displays coming into the market.
I should mention that active shutter displays do not have as bad a flicker issue as CRT monitors. Firstly, CRTs do not hold the images on the screen like LCD monitors, so this is what makes the flicker far more noticable. The 1/200 blanking (effectively 200Hz) is pretty fast considering that even 75 to 80Hz CRTs were pretty much flicker free for most people.
If you think about it, regular LCDs have a 60Hz refresh rate, but no flicker…for the same reasons. I have viewed active shutter displays and I don’t have any issues even though I am very sensitive to 60Hz CRTs. 120Hz active shutter 3D displays are probably a bad idea for those who are sensitive to flicker, but once you get to 240Hz or higher, it really is a non issue. I’d suggest you try out the new displays for yourself to judge, but some of the 3D cinema technologies are also using active shutter glasses with great success.
Your point about the compression and codec issues is a great one. It will certainly be interesting to see what they come up with here in the US. I do agree that we would need to move to H.264 to have good 3D without major compression artifacts.
about 5 months ago
I’m sure you guys have seen the JVC 3D (GD-463D10U) model that is currently available in the US. It uses circular polarization, meaning other than the resolution issue…the TV is here…now. And it was the TV that the Avatar creators used to make the movie. Oh…and you better bring the credit card that has the high limit.
http://pro.jvc.com/pro/microsite/3d/monitor/index.html
about 5 months ago
Taking 3d viewing one step further than just a big screen, you might want to be more or less surrounded by the display, and then some sort of Goggles with built in display is the natural solution. It has a major advantage in a 3d context, and that is that the eyes can be shown independent images with no special technology at all. It is simply separate displays. This could be the path ahead, instead of trying to separate two images from one source by various means
about 5 months ago
That is certainly possible Ed, but then you no longer have a TV, but individual units for each person. I don’t know if people and families are willing to replace a TV that serves a social purpose in a sense as it allows family members and friends to watch something together.
Additionally, a complete goggles based display is still very technologically challenging. In addition, creating content for it would be challenging, especially because quite a lot of the content will be in the peripheral vision of the viewer, and thus “wasted space”. I do think that such technology has obvious uses in a vast number of applications, but I’m not convinced that it will replace the need for flat screen televisions in our homes altogether.
about 5 months ago
I think most of the comments can be applied to any point in the evoluiton of TV.
- The large LCD-screen was a big challenge long ago, while 28″ CRTs was very feasible.
- the color depth of a modern TV is a waste of space, since the eye cannot see color very well except the point at which you focus.
- etc
Regarding the “no longer one TV family experience”, you could still make the whole thing an augmented reality thing, where you see a “TV” in 3d in the far end of the room, the size you want, but if you turn your head, you see your wife just like she is.
The “one TV” has obvious disadvantage:
- Only one person sits straiht in front of it. Everyone else gets a distorted perspective
- It takes space in the room (even a flat, thin LED TV uses wall space)
- It is more expensive the bigger it is
- It uses a lot of power and generates heat
All these down sides would be less with goggles per viewer.
I don’t expect it to happen tomorrow, but it seems a likely evolution. And it will generae another set of problems than those we are fighting with today, which means some of them may never need to be solved. Just like the flicker-free, ultrasharp, thin, 50″ CRT TV we dreamt of long ago was never needed.
Ed
about 5 months ago
Nice points Ed. It certainly would be exciting to see that technology being made possible. Perhaps I am overly skeptical about the goggles thing because Virtual Reality via Headsets and goggles was always, just around the corner ever since I was a kid. I’ve always been excited about it but the progress made so far has been disappointing to say the least
about 5 months ago
I guess scepticism can be translated into anticipated number of years we have to wait
- Small LCD-screens were around for ages before they eventually replaced CRT:s for TV:s.
- I am sure many dreamt of color TV in the era of B&W.
- etc
And frankly, since 3d vision is about seeing two slightly different pictures with your two eyes, generating them both on the same flat surface is not the most logical way. In some sense, it is a heritage from the technology we have for 2d, where a flat surface is a very sensible idea.
In a way it is like generating stereo sound from a single speaker, with earplugs filtering out the sounds not intended for the bear it is in, until you realize that you can have two separate speakers. It makes (some) sense only because it starts from how you generated mono-sound.
Cheers /ed
about 4 months ago
Another thing I didn’t see here:
Active shutter technology greatly reduces the brightness of the viewed image, and requires the display to be able to produce much brighter image in 3D mode than in regular 2D mode (probably plasmas will have slight problem there, I can’t wait too see one in action). Passive polarized glasses in other hand affect the brightness very little, and this is another advantage they offer.
Flat panel TVs that use polarized solution basically have polarization layer on the front, with each line polarized differently, thus reducing the vertical resolution for each eye in half. There are other (better) polarized solutions for flat displays which produce full resolution per eye, but currently implemented only in PC monitors.
HMDs (head mounted displays) are ultimately the best possible 3D solution, but currently only offer low resolution for the mini-displays. And they are not suitable for family viewing, only for 3D gamers/enthusiasts.
about 4 months ago
Oops, I didn’t see there was previous page
. The PC monitor I was talking about is the iZ3D one, and it uses two LCD panels – one for both colored images, and the second one to polarize each pixel individually, so each eye gets different amount of the brightness for each pixel (it uses linear polarization). I’m interested what the upcoming 27″ model of theirs will offer in terms of ghosting and 2D image quality.
about 4 months ago
I don’t see any principal problems with having goggles that display a common “3d-tv” in the living room as am augmented reality item, thus allowing you to see the other people in the room just as you do today.
Sure, some technology development is still needed, but I think it would be pessimistic to consider it unrealistic for “family viewing”.
/ed