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The Renaissance of 3D:
How the New 3D Technologies Work

Bill Livolsi, February 5, 2010

LCD Shutter Glasses Method

LCD shutter glasses are the first high-quality 3D implementation suitable for home use. In systems that use these glasses, the video display shows alternating left-right images very rapidly--up to 120 frames per second. The viewer wears a pair of active LCD shutter glasses which alternately block the left or right eye. Much like the effect of a DLP color wheel, this happens so quickly that your brain melds the two images together and creates the impression of a single image with 3D depth.

Advantages of Shutter Glasses

Color. While glasses vary, most have lenses without significant tint, which puts them on par with the polarization method for color accuracy. The glasses we have been using have a greenish tint to them but other brands we have seen do not.

Cross-talk. LCD glasses are perhaps the best of the bunch when it comes to cross-talk because the eye not being used is actively blocked by the shutter mechanism. Earlier versions had problems with ghosting, where part of the previous image would be retained on the screen after a new image had appeared. Newer, faster displays have all but eliminated this artifact.

Relatively inexpensive. The prices of 3D projectors and televisions are already very low. Even today, a projector capable of 3D at 720p is available for less than $800. While there are ancillary costs involved, such as a computer with a powerful graphics card and a set of glasses for each viewer, for home use with small audiences it is certainly affordable.

Disadvantages of Shutter Glasses

Active glasses. This is the main difference between LCD shutter glasses and other systems: the mechanism that controls which eye sees what is embedded in the glasses, not the content or the projector. LCD shutter glasses are great for small audiences of responsible adults, but they have several downsides. They are expensive compared to the cost of glasses for all other technologies ($100 to $150 per pair at the time of this article's publication). They are complex, with batteries and electronics and fragile LCD lenses. If they are dropped, stepped on, or run out of batteries, it can disrupt the 3D experience. And if you have a lot of friends who want to come see the Super Bowl in 3D, it can be costly to supply everyone with their own pair.

Synchronization. An active shutter system needs to have a way to synchronize the shuttering of the glasses with the content on the screen. Some systems use an infrared emitter. Texas Instruments' system for projectors and televisions, called DLP Link, uses synchronization pulses built into the projected image itself. While the two implementations use different sources for the pulse information, the pulses themselves are the same.

There is a difference between a left-eye pulse and a right-eye pulse, which is why all glasses synchronized with a given TV will be in synch with each other as well. But the projector has no way of knowing which frame is intended for which eye, leading to an interesting problem. These pulses can become reversed, leading to one eye seeing what is intended for the other. In other words the left-eye pulse will be associated with the right-eye image. This is known as the "pseudoscopic effect" and it is quite disconcerting the first few times you experience it. The effect is a strange sense of the image being inside-out, as if you are looking at a hollow 3D image from the wrong side. It is a common occurrence, so manufacturers have planned for it - it can be remedied by toggling an option in the display, or a computer's video card driver, or sometimes in the software itself. Still, it is not as foolproof as other systems.

Flicker. Some people have reported seeing flicker when using shutter glasses. Flicker is what happens when the refresh rate is not high enough, leading to a sort of stop-motion effect. It is true that, since each eye only receives half of the refresh rate, projectors used with shutter glasses must be very fast. To this end, modern implementations use at least a 120Hz refresh rate to deliver 60 frames per second per eye. We did not encounter any flicker during our testing so we cannot comment on the phenomenon's prevalence or seriousness.

Light loss. Shutter glasses systems use a single projector which switches rapidly to display different images, so there is a minimum 50% reduction in light output compared to 2D just as in other single-projector systems. The glasses reduce perceived brightness as well. While not all glasses are the same, the models we have tested decrease perceived brightness by roughly 60% regardless of the display or the content. The upside is that they also reduce black levels and contrast is increased significantly.

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Contents: What is 3D Anaglyph Polarizers Interference Filter
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Comments (19) Post a Comment
Currious Posted Feb 5, 2010 5:41 PM PST
So what about glasses-less 3D TVs?

Some companies claim they have that techno in store, from a flat screen.

One easy way to generate 3D that has been done, is to use a fast rotating screen, and as it turns display different pixels for that 3D position.
DD HT Lover Posted Feb 6, 2010 7:00 AM PST
Another fantastic article. Thanks for keeping us ahead of the curve again.
Paul Posted Feb 6, 2010 12:34 PM PST
When special glasses are no longer required, I'll be interested.
Matthieu Posted Feb 8, 2010 6:10 AM PST
Wow you did your homework VERY well. I'm into the 3D photogrphy for a long time and still I learned some things about tech stuff from yur review.
MREUM Posted Feb 10, 2010 9:31 AM PST
I still think 3D is a fad, just like before. People will tire of it, particularly if the 3D films are no better than what has already been produced. Until a system emerges that does not need glasses I do not see it being anymore than a novelty, although the adolescent gaming crowd will probably like it.
willdao Posted Feb 11, 2010 3:03 PM PST
Bill,

Very nice, comprehensive article!

Will
Wyatt Posted Feb 12, 2010 11:35 AM PST
As someone who has been working on a 3D film for the past year now and has experienced looking at the same material with all technologies (except for Interference3D), I can tell you that a good pair of shutter glasses is the best way to go.

I am sensitive to 3D cross-talk and the shutter glasses eliminate this completely for a crisper / cleaner looking image. Another advantage is that you do not have to keep your head on a level plane, so if you wanted to lay down on the couch with your head cocked sideway, shutter glasses would still work as intended. Polarized glasses do not stand up well to this.

Hopefully shutter glasses win the format war and will be mass produced making them much more affordable than they currently are.
libair Posted Feb 15, 2010 1:09 AM PST
well i think that it will take a long period before we see broadcasting in 3d although in korea this technology is here experimentally of course!!so its difficult for me who bought an hdtv this summer to participate in this even if this is 2-3 years ahead!!without the display that is capable of 3d you can only dream of 3d movies!does anyone know if there is a possibility for a top video box lets say to convert hdtv to 3d ready???of course not the 60hz but the 120hz or 200 hz ones...would that be possible!!from the other side here in grece where i live we will have the h.264 in a couple of months so i think the 3d broadcating about a century ahead!!!
Roy Posted Feb 16, 2010 11:56 AM PST
Very informative article. Thanks!

Because "3D Vision" glasses are another $200 on top of the cost of the projector, is it possible ProjectorCentral might consider a combo/package/bundle price where a person could buy say the new ViewSonic 3D projector + Nividia 3D Vision for a package price of around $500?
Jeff M. Posted Feb 22, 2010 9:41 PM PST
I don't know about the rest of you but I am ALL about 3D! If anyone on here could help me, my email is kraftmacincheese@yahoo.com I have been scowering reviews and the like in the search for a 3D projector with the crispest video that 3D projectors can offer. I am going to be throwing a distance of about 10 feet and trying to fill up a 110" screen as much as possible in a 16:9 or similar ratio. I have my eyes on the Epson 8500ub because of the awesome 200,000:1 contrast however it does not have 3D capabilities. So can anyone help me with this. I am trying to find the absolute BEST 3D projector on the market that I can get for around 3000 or so. However I am afraid that the image won't be crisp for movies and games like on one that has a contrast such as the Epson. I am a noob to projection and all of that but am computer literate so you don't have to speak slowly lol :P Thanks everyone.

Jeff
Stunko Posted Apr 8, 2010 9:17 PM PST
The current round of 3D hype will be dead inside of 24 to 36 months.... and will be resurrected some time later again... and again... and again.
Vincent Posted Apr 12, 2010 8:41 PM PST
In the 3D race, seems like the LCD/Plasma TVs are a little faster than projectors. Please correct me if I am wrong. Some of the TVs such as Samsung already supports 3D BlueRay directly (i.e. supports HDMI 1.4 format). Most data/home projectors only support HDMI 1.3 (1080P but not 3D). HDMI 1.4 is a relatively new standard.

Second problem is that it seems that only DLP projectors can support 3D projection. LCD based projectors cannot refresh at 120Hz. So quite a number of brands of projectors will not be able to get into the bandwagon so quickly.

For those looking for 3D experience using a projector and at 1080p, I guess the projectors will only be available some time later this year.
Richard Posted Apr 25, 2010 10:32 AM PST
I'm curious about one other thing. Isn't the end user dependent on the kind of coding that appears on, for instance, a Blu-Ray disk? Will these disks contain all the various encoding schemes, or what? Will I have to shop carefully, noting the kind of technology present on a specific disk before I buy it? If so, the media producers can quickly determine what standards will be weeded out, and buying anything now is premature. Just like VHS and Betamax all over again.
Bob Posted May 29, 2010 7:51 AM PST
So, if my projector refreshes at 120 Hz already, what is the prognosis for an interface box to decode Blu-ray 3D signals interlaced at 60 Hz for left and right eyes and providing the synchronization signal for the shutter glasses?
mdf Posted Jun 2, 2010 10:03 AM PST
Glasses-less 3D will never happen with current displays or projectors. In order for 3D to work, your right eye and your left eye have to see different images. If you shift a few inches to the right on your couch, how could your left eye not see what your right eye had been seeing? Until there are non-static holographic displays (there aren't and no one is working on them) the laws of physics make a glassesless 3D technology completely impossible.
Yllon Posted Jun 20, 2010 4:59 AM PST
This is not exactly true. Hitachi as come up with a way for you to see 3D with out the glasses. It is called parallax viewing. While this format is a year or two away and is only available in flat panels we will eventually see 3D with out glasses.
theG Posted Oct 10, 2010 7:38 AM PST
Bob, "Glasses-less 3D will never happen" check out [sales link deleted] and what about the 3D Nintendo DS?

Anyway, i dont mind the RealD glasses which will go with my realD projector next year... i hate sgutter glasses tho, expensive and you can see the flickering..
Esther Posted Jul 20, 2011 9:26 AM PST
what exactly do the 3D glasses given out at the movie theaters do? does anyone see a future of 3D movies without the glasses? is it likely that the glasses-less 3D showing technology will ever become commercialized enough to be used as widely as regular 2D tvs that most ppl have in their homes?
Carlos Zacharias Posted Sep 2, 2011 6:00 PM PST
What is the diference: 3 D READY AND 3D? Ex.: Optoma D33 and D66. Whych one is abble to project 3D movies riht now?

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