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World’s first stereoscopic motion picture camera made by William Friese-Green in 1893.There is no question that the current revolution in 3D imaging is due primarily to the commitment of Hollywood to the making of major 3D films and that this has been due principally to Los Angeles Corporation Real D’s spending of huge amounts of money to put digital 3D projections systems in place. From my point of view this happened because I saw Arch Oboler’s Bwana Devil in 1952 and began researching 3D in 1973 which led to the founding of StereoGraphics Corp in 1979 which was taken over by Real D in 2004. It is truly gratifying and amazing to see the vision I started to pursue in 1973 come to fruition.

Pioneering 3D Movie director Arch Oboler (Bwana Devil, The Bubble, Domo Arigoto) reading a 3D Comic ca 1982. Photo courtesy Susan Pinsky of Reel 3D. However, as anyone who has reflected on the causal nexus is aware, there are an unlimited number of other takes on reality, all equally valid. One could say that Arch Oboler is responsible or that Ed Land (founder of Polaroid Corp, one major inventor and marketer of polarized sheets) is, or that it’s due to Larry Hornbeck (principal inventor of DLP projection - US 5280277) or the 50,000 or so engineers and chemists who developed digital electronics and liquid crystal (LC) technology, and so on back to the beginning of time. Likewise, we are beholden to the great grandparents of Walt Disney, without whom there would presumably have been no Walt, no Mickey and Donald, no Shamrock Holdings and no $50M in the bank for Real D. Or, perhaps if Real D had talked to me or to IBM , Thomson or many others mentioned below, they would have had no reason to buy StereoGraphics or ColorLink and there would be burgeoning 3D but no CP switchers.

Even if Liquid Crystals (LC’s) or DLP projectors or polarizer technology did not exist it would still be feasible to have a 3D cinema now (e.g., using film with mechanical shutters- as was done 80 years ago- or CRT or light valve projectors such as Eidophor-the king of large screen electronic projection for many years (http://www.dcinematoday.com/dc/ProjectorHistory.aspx?index=31) , or with the Infitec system described below). All that was ever required was someone willing to get things started by spending lots of money to establish a 3D projection network and to convince the studios to make content and that just happened to be Real D in the last few years.

There are at least 5 distinct types of large screen 3D projection in current use. All projection modalities are agnostic regarding the means for taking, editing and compressing the images, so I will not go into the software issues except to mention that there are several codecs being promoted. It appears that Real D, DDD and Sensio are among those touting their own software and custom chips for compressing images into side by side formats (with possible options for over/under) while TDVision and Neotek (the TriD format mentioned below) eschew the discarding of any lines H or V and have means to compress all the pixels of both images into Windows compatible formats that might be made to run on next generation (and some current gen) TV sets, Set Top Boxes, TV recorders and HD DVD players. Of course the real codec decisions are likely to be made not by SMPTE committees but by tech managers at SONY, Matsushita, Philips, Samsung etc. Personally, I would not throw away the horizontal pixels needed for depth (letting the codec massage them back into place) unless there was really no other way. A similar struggle is going on in the autostereo arena between Philips (who, among other ways, have tried to get their proprietary version of the well known 2D plus depth method adopted as the Chinese national standard by exhortations before a government committee) and nearly everyone else, who want to compress with more standard means the 8 or 9 images most commonly used.

Anaglyph techniques are the oldest of all 3D projection means and are familiar to most people via the red and blue paper glasses. In Europe the glasses are usually red and green but in the last 15 years there have been a variety of entities promoting orange and blue--due to Land’s work at Polaroid long ago resulting in the Retinex theory of color vision. The orange/blue was first introduced in a serious commercial way by Li Gang of China who used it for 3DTV broadcasts in the early 90’s; next by 3DTV Corp on the net shortly thereafter in the modified and much easier to view SpaceSpex format; and then in the Danish ColorCode glasses for general use including at least one IMAX film and the Japan-only 3D release of Cameron’s ‘Ghosts of the Abyss’ DVD. To minimize ghosting both Li Gang and the Danes used very dark blue which produces severe luminance imbalance and corresponding eyestrain. My SpaceSpex modification fixes this and makes this a feasible method for getting full color stereo with any type of display.

Most people have a poor opinion of anaglyph, but if it is done digitally, and with care, from image creation to final viewing and the display is calibrated for the exact program and glasses being used, and the parallax is minimized, one can get a very nice full color image with more or less balanced luminosity (i.e., comfortable prolonged viewing) with simple two color paper glasses. Use of dichroic filters decreases crosstalk, but dramatically increases cost, and ghosting remains a problem unless the whole program is edited for minimal parallax or a ghost reduction algorithm is used.

The ultimate in anaglyph quality is the recent triband Infitec system mentioned below and clearly there can be an intermediate system (i.e., in image quality and cost) using two color bands for each eye, with corresponding costly 50 layer curved glass viewers (but see the Bosch patent below). The prime reasons for persistent interest in this old and humble method are the very low cost glasses (ten or even twenty pair/dollar in paper and almost free for multiple use plastic versions) and universal compatibility. Anaglyph can be captured, encoded, edited and displayed with virtually any method possible and if you want to do it over the net and broadcast TV or sell on DVD to billions it’s the only way. However, test images for consumer calibration of their displays/ personal visual systems (eyes) is essential (and of course highly desirable but almost universally ignored for any 3D or 2D system). Many persons continue to work at improving the anaglyph with new ideas and patents appearing yearly for over a century and most of this work is accessible in patents and web pages, so I will only mention some excellent work I have seen by John Schulze of Brightland http://www.brightland.com/r/Akumira_-_Stereoscopic_3D.html and the anachrome process by Alan Silliphant www.anachrome.com .

All techniques that use sheets of plastic polarizer in the projection path have the limitation that these absorb much of the light (as well as causing some depolarization) and so high brightness projectors are used which require cooling and degrade the polarizer. Some have dealt with this and other limitations by specifying wire grid polarizers (e.g., US 6,831,722, WO2007/070245) and these are just beginning to appear in commercial displays. Conventional TFTs have crucial advantages over current LCOS and so Kodak and others are developing ways to make more complex projectors to enable their use for 3D (WO2007/070245).

The dominant stereoscopic projection system at the moment (marketed by Real D but promised by several others) uses electrooptic switching of circular polarization (CP) with a specially constructed multilayer LC plate (US 2007/258138, WO2007/067493) in front of the projector lens with a silver (i.e., aluminized) screen and passive paper or plastic CP glasses for viewing. Alternation of polarized fields is a very old idea and goes back at least to the 40’s when the first sheet polarizers were invented, at which time it was done via a rotating polarized disc (a system resuscitated and being marketed to the 3D movie industry now).

Kerr cells (electrically switchable polarizing liquids, in principle identical to the CP switching of LCD’s by RealD’s method and due to the same electrically controlled birefringence), were invented and patented for this purpose about the same time (e.g., US 2002515, US 2118160, US 2417446, US 2616962, US 2638816, US 2665335, US 3358079, DE 736457, DE 2055935, DE 2140944) .

The achromatic (color correcting) properties of triple sets of mutually orthogonal half-wave retarders, discovered long ago by S. Pancharatnam (Indian Academy of Sci. 41A, 137-44(1955)) and subsequently pursued by many, particularly his compatriot P. Hariharhan (P.Hariharan and P. E. Ciddor, “An achromatic phase shifter operating on the geometric phase,” Opt. Commun. 110(1–2), p.13–17,(1994) ; P. Hariharan and P. E. Ciddor, ‘‘Achromatic phase shifters: A quantized ferroelectric liquid-crystal system,’’ Opt. Commun. 117 (1-2), p.13–15, (1995); P. Hariharan, "Achromatic and apochromatic halfwave and quarterwave retarders", Optical Engineering, 35, p.3335-3337, (1996); P. Hariharan and P. E. Ciddor, “Improved switchable achromatic phase shifters,” Opt. Eng. 38,6, p.1078–1080, (1999)). It is thus well known in the art, and has been researched frequently, and most vigorously recently by the Colorado company ColorLink (now part of Real D). Work on its components and related or alternative display tech is coming in an avalanche from all the big companies (e.g., Toshiba US7250923) as well as countless smaller ones—e.g., DigiLens (now owned by SBG Labs--- i.e., Switchable Bragg Gratings-- http://www.sbglabs.com/company.htm). For one suggested use of DigiLens in a complex Barco dual DLP projection patent see WIPO2005/039192, EP1830585. Among much related tech of interest are the LC products from Rolic, and tunable electrowettable diffraction filters from Nokia (WO 2007/096687). Much of the work uses polarization switchers and it is feasible to use other EO methods such as Pockel’s cells to switch polarization, either with classical methods or new ones (e.g., http://www.photonics.com/content/spectra/2007/May/research/87499.aspx) but research is required.

Those interested in details of ColorLink’s achromatic polarization switches and related tech may consult their numerous patent applications such as US 2008/0129939, 2008/0129900 , 2007/0188711 , 2006/0291053 and 2006/0285026, WO2007/086952, WO2007/024713,WO2006/135867, WO2007/095476 or their many granted patents for an introduction to the extensive prior art. There is also their book Polarization Engineering for LCD Projection (2005) which can be downloaded for the Kindle reader or viewed (slowly) from Amazon’s page. There is also much info in various recent texts such as Yang & Wu—Fundamentals of Liquid Crystal Devices (2006), Khoo-- Liquid Crystals ( 2007), Kato--Liquid Crystalline Functional Assemblies and Their Supramolecular Structures ( 2008), Scharf--Polarized Light in Liquid Crystals and Polymers ( 2007), Stewart-- The Static and Dynamic Continuum Theory of Liquid Crystals (2004), Briman et al.-- The Physics of Liquid Crystals (1993), Takatoh et al--Alignment Technologies and Applications of Liquid Crystal Devices (2006), Vicari—Optical Applications of Liquid Crystals (2003), Neto et al--The Physics of Lyotropic Liquid Crystals (2005), the long review by Singh-Phase Transitions in Liquid Crystals-- Physics Reports 324 (2000) p107-269 and Singh-Liquid Crystal Fundamentals(2002), all of which I select from a far larger list as they seem to be available on P2P.

As in any hitech arena, many of these patents get quite esoteric for nonspecialists, e.g., using Poincare’ spheres for calculating achromatism, and of questionable utility as practical methods for digital 3D cinema. US 2008/0129900 e.g., attempts to fix artifacts due to the gap between segments of the color wheel in single chip DLP projectors, which produces time sequential color ghosting (see Andrew Woods actual projector tests on frame sequential viewing with DLP), by instantaneously altering the driving voltage and hence the chromatic properties of the multilayered LC pi-cell, to blank gap image frames and smooth out their sequential spectral color. This and other work cited here indicates that the obvious method of affixing polarized pieces on the color wheel is unlikely to work well (e.g., see the Cobalt/3ality patents such as WO2005/112440).

It has been said (e.g., on the Real D page) that one cannot use single chip projectors for any active (i.e., frame sequential) 3D technique, but various single chip projectors operating at 85 or 120hz have been in successful 3D use with shutter glasses for at least 5 years, though they currently have some limits on image quality. In addition, new tech is being introduced (e.g., US 5490009, US 5612753, US 7180554, US 7241014, WO 2006/038744) and many new models specifically engineered for 3D will appear soon. Scandinavia based Projection Design and also the USA company LightSpeed have released new models suitable for small theaters. Even the king of the large format 3D film IMAX has seen the 3D digital light and is pursuing 3D DLP projection (US 7224411, WO 2007/024313). IMAX has used wireless shutter glasses with stereo headphones in some of their 3D theaters for about 10 years and they noticed that if one uses shutter glasses with silver screen and carefully aligned polarizers on the projectors as well, the figure of merit for on axis extinction rises from 150:1 to perhaps 1500:1 (they say 15,000:1 but this is clearly impossible), essentially eliminating ghosting (EP 0 820606 B1 from 1999) at the cost of a slight drop in brightness. I do not know if they actually used this method in their few shutter glasses theaters. However, if one uses the highest quality polarizers now available (e.g, Nitto 1220 or others in the G series or those from Sanritsu etc.) there would likely be no advantage since contrast loss due to ellipticity of light passing thru the shutter can be eliminated by an inclined quarter wave plate or other anisotropic means. In any case, given a system with silver screen, dual projectors and active or passive glasses it takes only minutes to place HQ polarizers in front of the lenses to see if it improves ghosting.
This however, will only be effective if the silver screen is high quality (see comments below).

Sedlmeyer’s 2007 patent for AUO on light valve dual polarized projection. There are also numerous patents on new projection technology for active or passive glasses. One promising example is an LC light valve method with the unfortunate acronym PEMFVORD (Programmable, ElectroMagnetic wave Field Vector Orientation Rotating Device), patented by Steven Sedlmayer of Arizona for the Taiwanese display company AUO last year, that appears able to produce very high efficiency native dual polarization (US 7,295,371). This could have a major impact on 3D projection due to low cost, brightness, image quality, energy efficiency and compactness. Of course many new technologies are being developed but they are probably years away. Those who want the bleeding edge might talk to Boeing about their quantum dot 3D displays (GB 2,425,673).

Regarding patents, we can expect numerous variations of every stereo display modality to appear in the next few years and much overlapping tech in the patents and products since the basics are public domain and, insofar as there are novel claims, patents take about 4 years to issue and meanwhile anyone is free to use them. One can also anticipate some complex patent fights since there is a huge and intricate prior art on all methods. The only part of a patent that matters are the claims and the granting of a patent merely says that they appear to be valid—an issue that only the patent courts can decide. I have studied the 3D patent and technical literature for 35 years and I suspect that more than 95% of all granted claims could not withstand a serious challenge.

Copyright Michael Starks
(2008)