In 1977, moviegoers fell in love with holography the moment a static three-dimensional Leia popped out of R2D2 in Star Wars. But in recent decades 3D imagery has left the realm of science fiction and has found real-world applications in medical imaging, aerial mapping, and molecular modeling. And in the past few years, the entertainment industry has jumped back on the bandwagon of stereoscopy, after a couple of decades away.
To highlight recent work in this field, Optical Engineering (published by SPIE) and the Journal of Electronic Imaging (co-published by SPIE and IS&T) are both featuring special sections on stereoscopic imaging.
• In February 2012, Optical Engineering will publish a special section on 3D and 4D imaging techniques and applications, guest edited by SPIE Fellows Lenny Lipton and Charmaine Gilbreath.
• The Journal of Electronic Imaging will publish a special section on stereoscopic displays and applications in the January-March 2012 issue, guest edited by Neil Dodgson and SPIE Senior Member Nick Holliman.
Invented nearly a century ago, 3D cinema had a heyday in the 1950s and again in the 1980s, but limitations in image quality, display technology, and consumer eyewear prevented stereoscopic cinema from taking hold with viewers. Now, due to advances in projection and display technology, 3D cinema is back in the limelight.
Evidence of the success of modern 3D cinema can be seen from the $2-billion-grossing film Avatar to postproduction 3D conversions of classic 2D movies like The Lion King.
From movies to medicine
Lipton invented the ZScreen, which is the basis of the RealD 3D system used in modern cinema today. (Incidentally, he also wrote the lyrics to "Puff, the Magic Dragon.") Lipton says, "The key to today's successful stereoscopic theatrical projection is that operation has been routinized. It is now no harder to project a 3D than a 2D movie. That means having one projector do the job, not two."
The push-pull modulator. The left and right fields from a digital projector's lens pass through the ZScreen which consists of a sheet polarizer and two pi-cells. The pi-cell axes are orthogonal to each other and at 45 degrees to the polarizer axis. The pi-cells are switched on and off out of phase with each other with the result that successive fields are alternately left- and right-handedly polarized.
Although current consumer attention is focused on entertainment applications of 3D, movies are only the tip of the iceberg for stereoscopic applications. Papers in these special sections also cover 3D imagery for archiving of cultural objects, viewing systems for medical imaging, visual comfort and viewing experience, plant-stem modeling, and stereo video inpainting, among other topics.
"The authors of these papers collectively describe substantial advances that will have lasting technical impact on the field," says Dodgson, a professor of graphics and engineering at University of Cambridge (UK).
Those impacts particularly affect the medical and defense fields. Imagine a 3D projection of a patient, prior to a surgery. Or a defense-training software application that shows soldiers how to navigate around barriers. Automatic target recognition, 3D modeling of structures, and surveillance are just a few of the applications that currently rely on the continued development of stereoscopic technology.
"This is the stuff of science fiction films in the 1970s," Gilbreath says, "and now we can almost do it. Math and technology have converged to allow us to return to this nascent field, and now we're on the brink of truly interactive imaging. It's time to give this a second look, to harvest these ideas out of the labs, and move them into medical, military, or entertainment applications."
Stereoscopic advancements in Optical Engineering
Lipton's paper, "Brief history of electronic stereoscopic displays" is of particular interest to the Optical Engineering special section. This paper traces the development of stereoscopic display technology from inception in the 1920s through the current dominant method for commercial stereoscopic projection, the ZScreen.
A. The late Jim Fergasen (left) and Art Berman working at StereoGraphics on what would become the ZScreen.
B. CrystalEyes eyewear and IR emitter. Introduced for science and industry in 1989, it is the first shuttering eyewear product, millions of which are now in use in theaters and homes.
Lipton explains the ZScreen as follows: "Phase-shifting liquid crystal cells in optical series, using the input of a linear polarizer, output circularly polarized light at the projector's field rate to encode alternate perspective fields with left- and right-handed circular polarization. The dynamic range of the ZScreen is sufficiently high, and the transition times from left to right and right to left are not only symmetrical but very fast, making it the ideal device for the purpose."
Although this flicker-free display technology has revolutionized 3D for the entertainment industry, Lipton notes that there is still room for technological advancement: "Get rid of those annoying glasses," he says.
This technology, too, is right around the corner.
Papers in the special sections of Optical Engineering and the Journal of Electronic Imaging can be accessed via subscription or pay-per-view at spiedigitallibrary.org/oe and spiedigitallibrary.org/jei.
-Gwen Weerts is a senior editor at SPIE.
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