Dolby Patents Hint at Consumer Version of Its 3D Cinema System

Although Dolby has filed applications for 3D patents recently, the 3D extension of Dolby Digital Cinema is based on technology brought in from Germany’s Infitec. The company’s name stands for “interference filter technology.” Its 3D format is called spectral separation. As used in Dolby 3D, narrow-band interference filters over the projector lens send slightly different red, green and blue frequency spectra to each eye for the left and right image views. When a viewer wears passive glasses with matching filters, the left eye sees only the left image, the right eye sees only the right image, and the brain unites the images to create a natural color balance.

In July 2006, Infitec and Dolby agreed to integrate Infitec’s 3D with Dolby Digital Cinema. Since then Dolby has filed for several of its own 3D patents in the U.S., most naming Martin Richards as an inventor. Dolby’s 2010/0060857 filing acknowledges and addresses practical problems with viewing glasses. There can be wavelength shift, especially on blues, if the screen is viewed from an angle. This can cause crosstalk between the left and right images, Dolby said. One remedy is to introduce a deliberate wavelength mismatch between the projection filters and eye filters. Another is to curve the lenses and make the glasses’ lenses thicker near the edges.

Intriguingly, the May 2008 filing refers to large screen TVs and PC monitors with spectral separation 3D. That suggests the Dolby-Infitec system may one day be marketed for home use.

The wavelength-shift remedies “are also applicable to large screen televisions, computers, virtual reality systems, and other display devices,” Dolby’s application said. The solutions also can be included on a “storage medium” for playback from “a media player coupled to a display device,” the filing said. “The storage medium is, for example, prepackaged with at least one pair of shaped glasses and available for purchase via a retail outlet.” That statement seems to imply the extension of spectral separation as a home 3D format for prerecorded media, like Blu-ray 3D. A future for spectral separation in home 3D viewing seems reinforced by the filing’s claim that “Any components of the present invention … may be embodied as an electronic signal broadcast (or transmitted) at any frequency in any medium including, but not limited to, wireless broadcasts, and transmissions over copper wire(s), fiber optic cable(s), and co-axial cable(s), etc."

An Infitec spokesman told us, “Infitec policy is to protect business partners. Information on business relationships can only be given as on a mutual basis. … We cannot give any further information.” The reply skirted our question about licensing arrangements with Italian TV manufacturer SIM2, which told us in December that it plans to release 3D projectors this year “based on technology by Infitec which is the same technology that Dolby will be using,” (CED Dec 3 p3).

Infitec is a private German company, spun off from DaimlerChrysler in early 2003 to exploit DaimlerChrysler’s “Wavelength multiplex visualization system” research project. All the IP and patents, developed by DaimlerChrysler, are now owned by Infitec, its spokesman told us. DaimlerChrysler’s involvement with displays goes back to the early 1990s, when the company was known as Daimler-Benz and it formed a 50-50 joint venture with German CE maker Schneider Electronics called Laser Display Technologies.

Schneider first showed “Laser TV” for HD at the 1993 IFA show in Berlin. It was then claiming that the first products would come to market in three years, initially for professional applications. Improved but still prototype models appeared at the 1995 IFA show, by which time Schneider had folded its laser TV technology into the Daimler-Benz joint venture. Schneider declared bankruptcy in May 2002. Its CE interests were bought for $8 million in September 2002 by TCL International Holdings, of Hong Kong, to accelerate TCL’s entry into the European CE market. LDT became Infitec shortly after.

Infitec’s IP on spectral separation has roots in LDT’s work from the late 1990s. Infitec’s website refers to a paper on a “new stereoscopic visualization tool by wavelength multiplex imaging” given by Infitec CEO Helmut Jorke and colleague Markus Fritz at the Electronic Displays Seminar in Wiesbaden, Germany, in September 2003. Our searches show that Jorke and DaimlerChrysler had before then filed several patent applications in Germany on spectral separation. Granted U.S. patent 6283597 is based on German filings from April 1997 and February 1998. U.S. patents 6698890 and 7001021 date from May 1999, and U.S. 6867775 stems from a German filing in February 2000. The latter patent describes a virtual reality system that offers different perspective views depending on people’s positions in a room.

Other applications filed by Jorke but not yet granted include international WO 2009/026888 from 2007 and 2004/038457 from 2002, and U.S. application 2010/0066813 and international WO 2008/061511 from 2006. The latter two applications, which are both based on the same German filing in November 2006, claim an idea for reducing the high cost of the interference filter glasses that viewers must wear. Instead of tightly filtering three slightly-different color bands for each eye -- red, green and blue -- one eye uses only two filters which overlap the blue/green and red/green color bands.

Among other Dolby patents we found, two relate to light transmission for projectors. That’s sometimes an issue for 3D in theaters, because two images are projected, and the special eyewear sometimes reduces the brightness to viewers. Dolby’s U.S. 2009/0316114 filing of June 2008 describes a light-channeling rod for a projector, with mirrored surfaces to recycle light that bounces off the filter wheel and would otherwise be wasted.

Other companies have been claiming their own variations on the spectral separation theme.

U.S. 2007/0146880, filed by JVC Americas in December 2005, describes a complex optical system that combines color filtering with the polarization needed for JVC’s D-ILA reflective LCD projection system.

Kodak has been active too. Its U.S. 2009/0190095 filing, from January 2008, offers a rundown on the basic patents for various 3D systems. The document says that “it has been proposed that the Infitec system would work best as a projection system using laser sources, however, this is not known to have been actually implemented in practice.” Kodak then claims a display for home use with two sets of color emitters that can be used either separately for color separation 3D, or together for 2D with enhanced color rendition.