Recent LG Patents Reveal More On Its Plan to Cut Costs of 3D TV Viewing
Recent patent filings uncovered by Consumer Electronics Daily reveal more details of LG’s plan to cut the cost of 3D TV viewing with systems that use inexpensive passive polarization glasses, instead of higher-priced active-shutter eyewear (CED Dec 16 p1). The filings also show that LG is already looking at alternatives to polarization.
US 2010/0007716, which dates back to a 2008 filing by LG Display in Korea, describes a full-resolution alternative to the half resolution passive polarization TV screens that LG currently markets, including to Sky in the U.K. for pub screenings of football matches. Instead of a passive grid of polarizing strips fixed to the front of an LCD panel, the new screen has an active filter fixed over the screen, the filing says. This rapidly switches between left and right circular polarization, while the screen displays a synchronized sequence of left and right images, it says.
The picture is displayed at twice the normal TV rate -- 120Hz instead of 60Hz -- to avoid flicker, the filing says. The advantages are that the viewer still needs to wear only cheaper passive polarizing spectacles, while the screen displays full-resolution images rather than the half resolution images delivered by conventional passive filter screen displays, it says. There is also a better balance between horizontal and vertical viewing angles, it says. This eliminates the “pseudoscopic” phenomenon, in which the polarization states of the left- and right-eye images are interchanged in the direction of the vertical viewing angle so that the left-eye image is seen to the right eye and the right-eye image is seen to the left eye, it says. In practice, this means viewers can watch 3D effectively either standing up or seated low on a sofa.
International W0 2010/079869 was filed only last year, so only a few paragraphs of the Korean text have been translated into English for patent office indexing. But these paragraphs are sufficient to reveal that LG is also now working on a 3D LCD panel that works along broadly similar lines to the Dolby cinema 3D system, using a modern full-color version of the old passive red-green anaglyph process.
The red, green, blue color spectrum bands used for the left- and right-eye images are slightly different and are displayed in rapid sequence, the filing says. The viewer wears passive color filter glasses that match the spectra, so the left eye sees only the left color image and the right eye sees only the right, it says. The color spectrum precision needed for good left/right separation is made possible by using LED backlights for the screen. This system, says LG, can produce a 3D image with better brightness and definition than a 3D LCD using polarization, and 3D viewing is less expensive than with a 3D LCD using time- sequential display and active-shutter glasses. At the factory, the fabrication process is simpler and cheaper because “little-changed conventional LCD production processes” can be used, the patent says.