Friday, December 13, 2013

Autostereo (Glasses Free) 3DTV In 2014: Sizzle or Fizzle?

Autostereo (Glasses-Free) 3D
Is 10 Years Away and Always Will Be?

That phrase caught my attention in a Variety article last January published by Valentina Valentini following a less than stellar debut of autostereo devices at the 2013 Consumer Electronic Show (CES) in Las Vegas. It reflects the thinking among many professionals 'in the know' within the 3D industry, but certainly not by all. Will the story be any different at CES 2014? With the mammoth Vegas convention rapidly approaching in less than a month I thought this would be a good time to take a look at where things stand in the world of glasses-free 3D.

The Holy Grail of 3D TV:
First, I should express my bias. I consider today’s passive 3D HDTVs ideal for achieving a very high quality stereo experience and wearing polarized glasses doesn't bother me at all. However, the consumer electronics industry and the media in general seem to have determined that the only way to make 3D welcome in the home is to get rid of the 3D glasses all together. Indeed, the amount of attention devoted to 4K or ultra high definition (UHD) TV at CES 2013 was seen as a less than positive forecast for 3D. In fact many proponents of 3D consider the inordinant amount of attention paid to UHD a wake up call that there needs to be greater attention devoted to making 3D more 'consumer friendly'. And there's little doubt that consumer friendly means no 3D glasses.

Unfortunately that perception has resulted in consumers being caught up in the industry hype that autostereo TVs are at best, already here or at worse, imminent.  As a consequence some have delayed their 3DTV purchases in anticipation of the ‘new generation’ of glasses-free TVs rather than taking advantage of the exceptional quality that HD and UHD passive 3D systems deliver today, albeit with glasses.

The Technology Behind Glasses Free Display Devices:
Currently glasses free 3D display devices are dominated by lenticular and parallax barrier technology, a variation of which has been around for over a century. Prior to being applied to these devices most of us have experienced the technology in novelty items and postcards. Sometimes called flicker or wiggle pictures, the cards are printed with two images on one sheet.  When the cards are wiggled horizontally they display a simple animation between the two images or alternately expose a second, entirely different image. In its more subtle form, this lenticular technique can simulate parallax, producing a fairly high quality static stereo image. This is accomplished by precisely placing a corrugated screen over a stereo pair that has been sliced into alternating strips.  Reflected light off of the alternating striped images is refracted via the corrugated ridges to the viewers corresponding left and right eyes.

This works fine for print signage such as point of purchase advertising as well as for other static displays such as theater lobby posters.  However, the technology requires viewers to position themselves precisely within a sweet spot in front of the printed image so that the corrugated ridges accurately refract reflected light to the appropriate eye. A moviegoer attracted to a lenticular lobby poster quickly understands that they must position themselves to an optimal location directly in front of and at a particular distance from the image to fully appreciate the 3D effect; a place we call the sweetspot. If they move to either side of the sweet spot they experience a 'dead zone' where the image becomes extremely confused and uncomfortable. 

While this limitation might be considered a marketing advantage for autostereo signage because of its attention grabbing potential, the same viewing restrictions are a significant disadvantage when applied to autostereo HDTVs that have emerged over the past three years. Lenticular and parallax barrier HDTV systems are similar in concept to the print technology described above in that they typically involve slicing stereo pairs into alternating strips.

However, in the case of 3DTV, the refracted light is not reflected off of the stereo pair strips.  Instead the light is generated from a backlight behind the LCD screen and a second LCD screen, imbedded with micro lenses is overlaid in such a manner that the pixels of the source image line up precisely with the lenses in the overlay. It’s these micro lenses that act to refract the light from each pixel of the underlying stereo pair to the appropriate left or right eye of the observer, producing the illusion of parallax without glasses.  In the case of parallax barrier systems, micro slits are added into the screen to mitigate cross talk between the refracted light, producing what some consider a higher quality stereo experience than lenticular alone.  However, regardless which autostereo display technology one uses, the viewing angle or sweet spot is a serious limitation.  If the viewer moves their head vertically or to one side or another, the parallax effect falls apart entirely.

Autostereo Mobile Devices:
When applied to single user devices like smart phones, tablets and even laptops, the sweet spot limitation is not as much of an issue because the user typically positions their head in front of the display and can move the device backward and forward from their eyes to get an optimized stereo effect. I’ve seen some decent quality autostereo video and images on smart phones such as the discontinued HTC 3D phone and I've seen adequate autostereo on a handful of tablets that are just making their debut in the market.

However it's clear that the technology has a long way to go before it can be considered a solid consumer product. One improvement on single user autostereo devices is the addition of eye tracking that takes advantage of front facing cameras. Eye tracking has the advantage of adjusting the viewing sweet spot based on the location of the viewer's head.  These devices can achieve a good parallax illusion for a single person within a viewing angle of as much as 170 degrees. However, apparently the eye tracking approach will not work with current parallax barrier systems because the micro barriers are a limitation in manipulating the sweet spot for wider viewing angles. 

Autostereo HDTV:
In the case of autostereo 3DTV where multiple people would typically watch a movie together in a family room, the process of converting stereo pairs that can be refracted through micro lenses and barriers is the same as described above for single user devices.  However, with more than one viewer there is a requirement for multiple stereo pairs to be displayed on the screen simultaneously.  While this allows for several viewers to watch 3D on the same TV screen, each person still must locate and then sit within their specific sweet spot.  If they get up from their seat or move their head too far  to either side, the illusion of parallax not only goes away but there is often a reversal of left and right eye projection making further viewing very uncomfortable.  On top of this, the use of as many as 9 or more stereo pairs being displayed simultaneously significantly reduces the overall resolution of the experience. I believe that attempts to improve lenticular and parallax barrier systems for TV viewing have been largely unsuccessful.  4K systems partially satisfy the resolution issue from displaying multiple images to accommodate several viewers, but the sweet spot limitation is still very much evident.

A Promising Variation of This Technology Was Demonstrated at CES 2013:
Dolby and Phillips have been promoting a 4K autostereo TV that some have called lenticular technology on steroids. It has greater pixel density due to the higher resolution and it uses lenticular lenses that I’m told are extremely high precision, down to the micron.

Instead of having 9 to 16 views, this technology accommodates 28 views which Dolby and Phillips claim mitigates dead spots and ghosting.  However, in reality the system actually has many more sweet spots and dead spots than other systems but because of the greater number of views being displayed, the transitions between each sweet spot are smaller and therefore less bothersome.  In addition, I'm told that this lenticular device uses an algorithm that further reduces the negative visual impact of the dead zones between sweet spots. The Dolby/Phillips system seems to be a step in the right direction but I believe it requires a great deal of improvement before it can become a consumer commodity. The two companies claim that in addition to planned algorithmic improvements to their lenticular system, an 8K resolution TV will eventually deliver 56 views, further limiting the dead zones between the sweet spots. Of course that product is very much in the future.

Will this be the autostereo solution? In Valentina Valentini's CES 2013 Variety article she quotes Lenny Lipton, the godfather of 3D who, reflecting on Dolby's autostereo display said, "the best I've ever seen, but he added "I'll be damned if I know whether the public will accept it." 

So Where Do We Go From Here?

Scientists at NHK (Japanese Broadcasting Corporation) consider 8K the maximum spatial resolution that 2D TV will ultimately achieve. They claim that anything above 8K produces deminishing returns because the added resolution is imperceptable to the human eye.

They speculate that once 8K 2D TV has reached an installed base, 3D will become the highest priority in the advancement of TV technology. Those evangelizing autostereo TV have expressed hope that 8K will provide the necessary spatial resolution to host 56 or more sweetspots.  Will that do the trick? We'll have to wait and see.  I wouldn't be surprised if one or more of the major manufacturers debuts such an autostereo prototype at CES 2014.

If they do, I suggest asking them to show the same content next to a current passive HD 3DTV. Then you can compare both the quality and accuracy of the stereo between the two devices. To become successful, in addition to tackling reduced dead zones the device has to display accurate stereo information, something that has been sorely lacking in the current line up of lenticular and parallax barrier displays.

It's quite apparent that Ultra High Definition will continue to be one of the hottest buzzwords for the consumer electronics industry this year and it will likely become a driving force among many of the largest TV manufacturers.  However I firmly believe that the industry as a whole will come to understand that 3D and UHD are not mutually exclusive.  Instead, I see 3D technology essential to the near term adoption of UHD and vice versa. The two technologies are in a sense, mutually beneficial killer apps.

So if you're planning to attend CES in January, I don't think you'll find a UHD solution to the autostereo puzzle. Near term, autostereo technology will likely progress along the lines of the Dolby/Phillips approach.  No one will be happier than me if they or others succeed in creating an autostereo experience that is equal in quality to the 3DTVs currently available to consumers.  If we don't see that level of quality on the horizon, autostereo technology might have to take on a uniquely different technological paradigm if glasses free 3D TV in the home is going to become a viable consumer product.  I'll be attending CES this year and hope to explore the latest and greatest in autostereo systems.  If I find that developments in autostereo technology have exceeded my expectations I will discuss those findings in a future blog post.

In the meantime, I'll be content wearing my passive 3D glasses at home, watching absolutely stunning 3D on the latest TV displays whether they be HD or UHD.