Overview of 3D technologies

As an assistant researcher with a big budget, I’ve had a chance over the past few weeks to play around with all the various 3D technologies currently on the market. Today I’d like to give you a brief overview of all the various technology behind this years 3D revolution, then next week we’ll take a more in-depth look at specific products that you can buy and be playing games on your PC in 3D now.

Introduction:

The concept of viewing something in 3D is remarkably simple – instead of just looking at a single flat image, you’re actually looking at 2. The amazing part is that your brain can combine these 2 images into 1 single 3D view of the world. Even without any crazy glasses, your brain can do this. Look at the side-by-side pictures below of my messy-as-hell desk, and slowly cross your eyes so you vision goes all doubled. Now line up those two images somewhere in the middle, and suddenly your brain will identify them as 3D and you’ll be blown away.

So how are all these new 3D TVs and displays going to work, and how do those funny glasses you put on in the cinema make the movie 3D? The same concept applies to all of them – the movie theatre/TV screen needs to deliver a slightly different image to each eye. So let’s take a look at the various methods to do that:

Just so you know, I’m not including “analglyph” (red/blue glasses) in this list as the tech is incredibly old and bad quality.

Passive Polarization:

Science time. Light is quite chaotic usually – it travels in all directions, until it hits something or is reflected back. When it gets reflected, off a mirror for instance, it becomes polarized. You can also polarize light with a special filter. The clever thing with these filters is that the polarized light that passes through one can then only pass through another filter if it’s aligned in the same way as the first filter. So, by putting together two of these filters, you can control the amount of light that passes through all the way from 0% to 100% just by adjusting the angle of the second filter.

So, can you see how we might use these polarizing filters to deliver a different image to each eye, and hence make a 3D image to the viewer? Essentially, we need 2 projectors, each with a different filter on them, a screen to reflect the image back at us, and then a pair of glasses fitted with another set of filters (the same as the filters fitted on the projectors). This is how all IMAX theatres work. One projector produces light for the image of one eye (polarized on particular direction), which only one of the filters will allow through, and the other projector produces the light for other eye. Combined in our minds, we get 3D.

The advantages of the polarizing method are that the glasses are incredibly cheap to produce and easily replaceable – perfect for large scale movie screenings and such. Unfortunately, a special screen is required (a “silver screen”) which will preserve the polarization of the projected image – normal white screens just bounce the light back off in a different direction – so it can’t be used in just any theatre without retrofitting a new screen. It’s also not really viable for use at home, because of the cost of purchasing 2 projectors and the silver screen.

Active Shutter Glasses:

With active shutter glasses, each lens has a tiny LCD screen in it. With a small amount of power, the LCD screen can be completely blacked out. This means that if we syncronized the left and right lens to turn on and off alternately, and then displayed a different image for each eye alternately at the same exact time on the screen, we can deliver a different image to each eye of the viewer. Try it now – focus on something, then blink in each eye alternately – the image is slightly different, which is why you get 3D right? Now, if we speed up the whole process so that each lens is turning it self on and off maybe 30 times a second in time with the alternate frames of the movie (syncronized generally via infra-red signal), our brain would simply merge the two images together and make a single 3D image.

Using shutter glasses to view 3D is actually not new technology. Around 10 years ago when shutter glasses were first introduced, bedroom PC gamers were having a blast with affordable shutter glasses that could be used with those huge old CRT monitors; but then the flatscreens took over the world. Flatscreen monitors, nice and small and thin as they are, are sadly quite slow. Slow enough that you could no longer use shutter glasses, which pretty much destroyed 3D gaming. Now, flatscreens are finally catching up to be fast enough to use with shutter glasses again, which is why there is a sudden resurgence of 3D technologies and movie this year. The key number is 120Hz, at which point using flatscreens with active shutter glasses becomes a reality again.

What about projectors for cinemas? Well, most projectors are actually just the same as flatscreens, only instead of putting a back on the screen they shine a light through it instead, so the same applied. Newer, more expensive projectors use a different kind of technology called DLP, which is basically a series of tiny little mirrors, one for each pixel, which move to display a different colour – most of these can also be used with active shutter glasses. Again, these kind of projectors have hit a consumer price-point this year too, so you’ll be seeing a lot of 3D capable projectors as well as new TVs.

The downside to active shutter glasses is that the glasses are quite bulky (remember, there’s a battery and two tiny LCD screen in there!) so some people find them uncomfortable. The glasses themselves are also quite expensive to replace, so the ones you get at the cinema tend to be rather heavy duty to withstand public use, and hence heavier.

“Holographic” 3D displays:

I’m not sure if holographic is the official name for this kind of 3D imagery, but I’m going to call it that as it’s the easiest to understand. You can be sure that each company will give it their own name though. Holographic 3D requires NO GLASSES, so it’s what most people might aspire to as being the ultimate in 3D technology. Though this kind of technology might actually sound a long way off, it is here, now. Though there are a myriad of competing technologies, they all boil down to the same basic method – remember though holograms you got in cereal packets as a kit? Yeh, pretty much the same… Only, instead of having to wave the thing around to see the left and right view, the TV automagically displays each image at the same time, and depending on the angle it is viewed from (ie., your left and right eye) displays a different image.

Having had the chance to play around with one of these displays, I can honestly say I’m not that impressed. Ok, this kind of 3D technology is still in it’s infancy, so I’m sure the quality will improve, but it just doesn’t seem to have a lot of depth, even at the highest convergence settings. You look at it, and think “well, it’s kind of 3D I guess…” Another problem is that the angles you can view these TV screens at is very much set in stone – moving your head a little left or right will ruin the effect. Again, I’m sure this will improve with time, but I would stay away from them until then.

One good use of the holographic screens is on the back of 3D cameras – the screen is so small that the lack of depth isnt really an issue, but it gives you a good idea of the 3D image you’re taking without having to wear glasses. Again, we’ll take a look at an actual 3D camera you can buy in the next article, coming soon.

So there you go. I hope you have a slightly better idea of the kinds of 3D technology out there, and coming to your homes this year. My personal preference is the 3D shutter glasses, as they seem to give a better quality picture with the most immersive feeling – but 3D viewing style is very much a personal preference. Some people get headaches in minutes, some can sit 30cm from the screen and play for hours. In fact, 1 out of every 10 people can’t even see in 3D…

Next week I’ll introduce you to actual products available to buy, so you can experience 3D games and movies on your computer, right now. Stay tuned, and don’t forget to subscribe to the RSS feed. (What is an RSS feed?)