Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Glasses-free 3-D projector

19.05.2014

New design could also make conventional 2-D video higher in resolution and contrast

Over the past three years, researchers in the Camera Culture group at the MIT Media Lab have steadily refined a design for a glasses-free, multiperspective, 3-D video screen, which they hope could provide a cheaper, more practical alternative to holographic video in the short term.

Now they've designed a projector that exploits the same technology, which they'll unveil at this year's Siggraph, the major conference in computer graphics. The projector can also improve the resolution and contrast of conventional video, which could make it an attractive transitional technology as content producers gradually learn to harness the potential of multiperspective 3-D.

Multiperspective 3-D differs from the stereoscopic 3-D now common in movie theaters in that the depicted objects disclose new perspectives as the viewer moves about them, just as real objects would. This means it might have applications in areas like collaborative design and medical imaging, as well as entertainment.

... more about:
»Camera »MIT »Technology »algorithm »explains »hertz »images »produce

The MIT researchers — research scientist Gordon Wetzstein, graduate student Matthew Hirsch, and Ramesh Raskar, the NEC Career Development Associate Professor of Media Arts and Sciences and head of the Camera Culture group — built a prototype of their system using off-the-shelf components.

The heart of the projector is a pair of liquid-crystal modulators — which are like tiny liquid-crystal displays (LCDs) — positioned between the light source and the lens. Patterns of light and dark on the first modulator effectively turn it into a bank of slightly angled light emitters — that is, light passing through it reaches the second modulator only at particular angles. The combinations of the patterns displayed by the two modulators thus ensure that the viewer will see slightly different images from different angles.

The researchers also built a prototype of a new type of screen that widens the angle from which their projector's images can be viewed. The screen combines two lenticular lenses — the type of striated transparent sheets used to create crude 3-D effects in, say, old children's books.

Exploiting redundancy

For every frame of video, each modulator displays six different patterns, which together produce eight different viewing angles: At high enough display rates, the human visual system will automatically combine information from different images. The modulators can refresh their patterns at 240 hertz, or 240 times a second, so even at six patterns per frame, the system could play video at a rate of 40 hertz, which, while below the refresh rate common in today's TVs, is still higher than the 24 frames per second standard in film.

With the technology that has historically been used to produce glasses-free 3-D images — known as a parallax barrier — simultaneously projecting eight different viewing angles would mean allotting each angle one-eighth of the light emitted by the projector, which would make for a dim movie. But like the researchers' prototype monitors, the projector takes advantage of the fact that, as you move around an object, most of the visual change takes place at the edges. If, for instance, you were looking at a blue mailbox as you walked past it, from one step to the next, much of your visual field would be taken up by a blue of approximately the same shade, even though different objects were coming into view behind it.

Algorithmically, the key to the researchers' system is a technique for calculating how much information can be preserved between viewing angles and how much needs to be varied. Preserving as much information as possible enables the projector to produce a brighter image. The resulting set of light angles and intensities then has to be encoded into the patterns displayed by the modulators. That's a tall computational order, but by tailoring their algorithm to the architecture of the graphics processing units designed for video games, the MIT researchers have gotten it to run almost in real time. Their system can receive data in the form of eight images per frame of video and translate it into modulator patterns with very little lag.

Bridge technology

Passing light through two modulators can also heighten the contrast of ordinary 2-D video. One of the problems with LCD screens is that they don't enable "true black": A little light always leaks through even the darkest regions of the display. "Normally you have contrast of, let's say, values between 0 and 1," Wetzstein explains. "That's the full contrast, but in practice, all modulators have something like 0.1 to 1. So you get this 'black level.' But if you multiply two optically together, the black level goes down to 0.01. If you show black on one, which is 10 percent, and black on the other, which is also 10 percent, what you get through is 1 percent. So it's much more black."

By the same token, Hirsch explains, if the patterns displayed on the modulators are slightly offset from each other, the light passing through them will interfere with itself in ways that actually heighten the resolution of the resulting images. Again, the researchers have developed an algorithm that can calculate those patterns on the fly.

As content creators move to so-called "quad HD," video with four times the resolution of today's high-definition video, the combination of higher contrast and higher resolution could make a commercial version of the researchers' technology appealing to theater owners, which in turn could smooth the way for the adoption of multiperspective 3-D. "One thing you could do — and this is what actual projector manufacturers have done in the recent past — is take four 1080p modulators and put them next to each other and build some very complicated optics to tile them all seamlessly and then get a much nicer lens because you have to project a much smaller spot and bundle that all up together," Hirsch says. "We're saying you could take two 1080p modulators, stick them in your projector one after the other, then take your same old 1080p lens and project through it and use this software algorithm, and you end up with a 4k image. But not only that, it's got even higher contrast."

###

Written by Larry Hardesty, MIT News Office

Additional background

ARCHIVE: Glasses-free 3-D TV looks nearer http://newsoffice.mit.edu/2012/glasses-free-3d-television-0712

ARCHIVE: Better glasses-free 3-D http://newsoffice.mit.edu/2011/glasses-free-3d-0504

ARCHIVE: In Profile: Ramesh Raskar http://newsoffice.mit.edu/2011/profile-raskar-0929

Abby Abazorius | Eurek Alert!
Further information:
http://www.mit.edu

Further reports about: Camera MIT Technology algorithm explains hertz images produce

More articles from Medical Engineering:

nachricht Imaging probe yields double insight
05.08.2015 | The Agency for Science, Technology and Research (A*STAR)

nachricht Tiny mechanical wrist gives new dexterity to needlescopic surgery
24.07.2015 | Vanderbilt University

All articles from Medical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

Im Focus: FIC Proteins Send Bacteria Into Hibernation

Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.

For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...

Im Focus: Fraunhofer IPA develops prototype of intelligent care cart

It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.

Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Interstellar seeds could create oases of life

28.08.2015 | Physics and Astronomy

An ounce of prevention: Research advances on 'scourge' of transplant wards

28.08.2015 | Health and Medicine

Fish Oil-Diet Benefits May be Mediated by Gut Microbes

28.08.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>