Shift to 3D Reignites TV Image Quality Competition
Three-dimensional (3D) TV is finally coming to the home, with sales making a strong start and expected to keep rising sharply. The trend has reignited the competition for better image quality, though, with manufacturers striving to slash crosstalk and boost screen brightness as a result. Japanese manufacturers are banking on their experience in creating beautiful imagery to put them back in the game.
"We've only just released it to the market, but it's selling a lot better than we hoped," says Shiro Nishiguchi, Executive Officer of Digital AVC Products Marketing Division of Panasonic Corp. of Japan.
The first 3D televisions, capable of displaying 3D imagery, hit the shelves six months ago, carrying with them manufacturer hopes for a new hot product to help them escape from a hopeless price competition (Fig. 1). All the involved manufacturers agree that sales are off to a great start.
The major TV manufacturers began releasing a flood of 3D sets to the market in 2010, all claiming superior image quality. From late 2010 through early 2011, new faces in the industry are also expected to begin announcing 3D TVs.
Samsung Electronics Co., Ltd. of Korea was the first off the blocks, selling 600,000 units as of the end of June 2010, and rising its annual sales target for 2010 upward as a result. The company simultaneously released fifteen models, from LCD to plasma display panel (PDP), in the key US market. In LCD TVs, the 240Hz-drive system that is their core product can be switched to support 3D, but the price tag has only been boosted by about US$300 to support 3D imagery. This pricing strategy seems to have paid off big.
Companies like Panasonic, Sony Corp. of Japan and LG Electronics, Inc. of Korea, on the other hand, have not disclosed concrete sales numbers, but are just as optimistic about the market. Panasonic's Nishiguchi reveals "In the second quarter of 2010, 3D accounts for about forty percent of sales for 50-inch and larger TVs, for sets that are available in 3D models.
The situation is similar at Sony, according to Satoru Kuge, Senior Manager of Consumer AV Marketing Div.of Sony Marketing (Japan), who says "Since we began sale in June 2010 we have continued to hold the largest share in the domestic market by volume." Minimum 2010 sales targets are 2.5 million units for Sony, 2.0 million for Samsung, and 1.0 million apiece for Panasonic and LG.
A New Era of Intense Competition
Determined not to lag behind in the 3D boom, TV manufacturers both in Japan and overseas are joining in.
Sharp Corp. of Japan, which holds the top share of the domestic market by volume, announced 3D-capable sets in May 2010, followed by third-ranked Toshiba Corp. of Japan in July of the same year. Mitsubishi Electric Corp. of Japan is involved, as it Hitachi Consumer Electronics Co., Ltd. of Japan. From the 2010 Christmas shopping season a host of new TV manufacturers will join the competition, such as VIZIO, Inc. of the US.
Survey firm DisplaySearch of the US, according to Hisakazu Torii, Vice President of TV Market Researchof the firm's Japan office, predicts that demand for 3D TVs in 2010 will easily top 3.4 million units (Fig. 2). The forecast as of May 2010 was about 2.5 million units, so this DisplaySearch figure is based on surging demand. DisplaySearch's Torii adds "The market will continue to grow at a healthy pace as 3D functionality gradually becomes a standard feature."
Panasonic, in fact, already offers 3D display functions standard on all 42-inch and larger sets, except for some low-price models, according to the firm's Nishiguchi. DisplaySearch predicts that total global demand for 3D TVs will reach about 43 million units in 2014, with about 37% of all sets 40-inch and larger (thought the best size for 3D imagery viewing) supporting 3D display.
Global market demand for 3D TVs in 2010 was about 3.4 million sets, but this is expected to rise to about 43 million in 2014. Only 5% of 40-inch and larger TVs were 3D-capable in 2010, rising to an estimated 37% in 2014.
Getting Set with Content
The major TV manufacturers are clearly pinning their hopes on 3D, but there's no denying a certain degree of worry that it may all be just a flash in the pan. It is clear that the technology will spread to some areas, such as movie theaters, but the environment is simply not ready for regular viewing in the home.
The 3D TVs sold by Samsung are called "3D ready," with no 3D viewing glasses packaged in the carton with the set. It is possible that consumers may be snapping them up just to be ready for the future in style, even though they are not watching any 3D content. Any widespread adoption of 3D television will require a much broader array of 3D content, and technological improvement (Fig. 3).
Further improvements in content selection and display technology will be needed to prevent the 3D TV boom from petering out. TV manufacturers are especially interested in improving 3D image quality.
It will take some time before content is up to snuff, but progress is being made. 3D broadcasting, viewed by many as the biggest key to success, is already planned for rollout by Panasonic, Sony and others, in cooperation with primarily American broadcasters. Panasonic and DIRECTV, Inc. of the US launched a suite of 3D channels on July 1, 2010. The firm says that 3D viewing is now possible to about 11 million households in the US.
Sony plans to begin broadcasting in 2011 in the United States, establishing a 3D-only broadcasting company together with Discovery Communications, Inc. of the US and IMAX Corp. of Canada, among others.
Manufacturers are also pushing ahead with cameras and camcorders capable of shooting 3D images, and 3D-capable game software, as well as building 2D-3D conversion functions into 3D sets to automatically convert 2D images into 3D.
Key Issues are Crosstalk and Brightness
With the emergence of 3D as a new axis of competition, TV manufacturers are once again forced into competition to deliver higher image quality, this time in 3D.
At present, they all use the frame sequential method of displaying 3D images (Fig. 4). Full high-definition (HD) images, each 1920 pixels x 1080 pixels, are alternated between left and right eyes each frame, using glasses with synched liquid crystal shutters to alternately block left and right eye vision, simulating 3D. In principle, anyone can make a "3D" television with just a display running at 120Hz or higher, glasses with liquid crystal shutters, and a sensor to keep them in synch.
3D TV principle of operation for frame sequential design. Anyone can make one with a 120Hz-drive display, glasses with liquid crystal shutters, and IR sensor to synch the two.
There is still considerable room for improvement in 3D image quality, but technological expertise will be needed to make the imagery good enough for consumers to enjoy without stress. The biggest problems of the frame sequential method are crosstalk and reduced brightness (Fig. 5).
Many firms are developing technology to resolve problems with frame sequential 3D TV, namely crosstalk and reduced brightness.
Crosstalk refers to the overlap between the left and right eye images. Crosstalk not only degrades 3D image quality, it can also cause discomfort through eye fatigue and even motion sickness. Many manufacturers have made reducing crosstalk their top priority.
The other problem is image brightness. Shigeaki Mizushima, Executive Managing Officer of Sharp comments "Brightness with PDPs and LCD panels can drop to as low as 10% of regular 2D screen brightness." This is because in addition to dimming caused by the transparency of the polarized viewing glasses, light loss is also increased by measures designed to reduce crosstalk, as detailed below. The difference in image quality from these two causes is clearly visible to consumers.
Until recently, TV manufacturers have been competing in technologies to boost image quality far beyond the point that most consumers even notice, but with 3D TV these technologies may directly earn consumer appreciation. And as a source at Sharp explains, manufacturers newly entering the business are unable to easily duplicate image quality technologies even when concrete methods are disclosed.
Many 3D TV "test drive" rooms have been set up, mostly at mass merchandisers, and as consumers crowd to experience the new technology, Japanese manufacturers see an opportunity to regain market share through their expertise in creating beautiful imagery.
Already television manufacturers are beginning to claim the superiority of their own 3D TV imagery, splitting into PDP and LCD groups, just as happened when flatscreens were first released. The competition between PDPs and LCDs is back, as intense as ever.
PDPs Boast of High-Speed Response
The biggest problem mentioned by the TV manufacturers is crosstalk, and resolving it demands a very fast response by the device itself.
Panasonic, defending the PDP TV all by itself, strongly pushes the high-speed response of the technology. Plasma display panels are impulse displays, with very short emission and afterglow times. As Panasonic's Nishiguchi explains, "Response is much faster than LCD TVs, and that alone means crosstalk is much less of a problem."
Panasonic has developed ways to minimize crosstalk in its 3D TVs (Fig. 6). The firm developed a new phosphor with an afterglow time only one-third that of the company's own 2009 product. Panasonic also improved the way PDP gradations are controlled by overlaying light pulses.
Previously they emitted the shortest pulses first, overlaying pulses in increasing duration, but the new models have reversed this order. Between them, the two improvements significantly reduce residual image duration, thereby reducing superimposition of left and right eye images.
Panasonic has modified its PDP to minimize crosstalk, developing a phosphor with a shorter afterglow time and changing the emission control method.
LCDs Require 240Hz Drive
The LCD TV manufacturers, however, also claim their crosstalk countermeasures are up to snuff. LCD panels are hold displays, with relatively long emission and afterglow times. In general, they are more susceptible to crosstalk than PDPs. Manufacturers have boosted the LCD panel drive frequency from 120Hz to 240Hz, as well as incorporating other measures including improvements to the LED backlight emission method.
Concrete crosstalk suppression implementations vary by company. Sony, for example, displays the same frame twice in a row, for left and right eyes (Fig. 7a). The LCD backlight is turned on only for regions where there is no overlap between left and right eye images within the frame, and the liquid crystal shutter in the glasses opened accordingly.
Crosstalk can be suppressed in LCDs by driving the panel at 240Hz and using scan technology in the LED backlight. Sony addresses the problem by displaying the same frame twice in a row (a), while Samsung inserts a black screen (b).
Sharp uses the same approach, but with finer control of LED backlight emission. The image is split into five or six regions vertically, and emission controlled independently for each to minimize crosstalk.
Samsung and Toshiba Use Black
Samsung, on the other hand, interlaces a black image into both left and right eye image streams (Fig. 7b). The LED backlight emits in synch with image write. While the LED backlight is not using area emission control at present, the firm plans to split it into about eight regions vertically for individual control.
Toshiba also inserts black images in both left and right eye imagery. "This approach reduces crosstalk more effectively than showing the same frame twice," claims Yuji Motomura, Chief Specialist of Visual Products Companyat the firm. The LED backlight is controlled in sixteen vertical regions for the direct illumination type mounted on the rear of the panel, or two in the edge light type.
Sharp Offers the Brightest Imagery in the Industry
Many manufacturers have declined to discuss concrete measures being taken to address the problem of reduced brightness. Sony, for example, boosts the emission efficiency of the LED light source in the backlight higher for 3D imagery than for 2D. The number of LCD panel polarizers in the glasses has also been cut from two to only one to increase brightness, but no specific measurements have been disclosed.
The only company to disclose luminance data for 3D TVs is Sharp, which claims a brightness of 100cd/m2 or better, the highest in the industry, through viewing glasses. "Compared to 2D imagery, the surrounding luminance is cut to 18% through glasses with polarizers," says the firm's Mizushima. "Luminance would have to be increased to at least 90cd/m2 in order to achieve the same apparent brightness as a 2D display, which is 500cd/m2. Even the brightest 3D TVs announced by our competitors only achieve about 60cd/m2."
Sharp has developed four proprietary technologies for its 3D TVs: ultraviolet induced multi-domain vertical alignment (UV2A), the use of four primary colors, frame-rate enhanced driving (FRED) and scanning LED backlights. Together, they not only minimize crosstalk, but also increase luminance 1.8 times.
Adopting Four Key Technologies
Of these, UV2A and the switch to four primary colors have already been tapped for use in LCD TVs handling conventional 2D imagery. UV2A is a type of photo-alignment technology utilizing UV light to control the orientation of the liquid crystal molecules. When irradiated with UV light, the main chain of the polymers tilts accordingly, in a polymer thinfilm orientation film. This approach makes it possible to eliminate the slits and ribs necessary for alignment of liquid crystal molecules in the conventional vertical alignment (VA) method, which increases the panel's aperture ratio 1.2 times. Response is also improved to no more than 4ms, which is about half the standard time, helping suppress crosstalk.
The fourth primary color, added via an LCD panel color filter, is Y (yellow), added to the existing red, green and blue (RGB) colors. The Y wavelengths of the LED backlight are utilized, increasing optical utilization 1.2 times.
FRED and the scanning LED backlight are new technologies. FRED makes it possible to drive the display at 240Hz with one source line per pixel, which improves the aperture ratio 1.1 times. Until now, says a source at Sharp, 240Hz-drive LCD panels required two source lines per pixel. The scanning LED backlight primarily reduces crosstalk, using LEDs 1.1 times brighter than prior designs for improved screen brightness.
Continuing Improvements to Vertical Alignment
With the surging popularity of 3D TVs, LCD panel manufacturers in Korea and Taiwan are accelerating the development of technologies to improve response and aperture ratio for TVs using vertical alignment (VA), which is the most common approach. VA designs have been somewhat inferior to in-plane switching (IPS) designs in terms of display performance, but today they are at least as good, if not better.
Panel manufacturers are especially interested in developing and volume producing a display technology called polymer sustained alignment (PSA). Volume production is already under way at AU Optronics Corp. (AUO) of Taiwan and Samsung, and being considered by Chimei Innolux Corp. (CMI) of Taiwan.
Like Sharp's technology, PSA also uses UV light to control liquid crystal polymer orientation, eliminating the need for ribs and slits. It utilizes a liquid crystal material that has been mixed with a UV-setting plastic. The UV-setting monomers are injected into the panel together with the liquid crystal molecules, and the panel then irradiated with UV light while voltage is input, controlling molecule alignment.
According to a source at AUO, display performance is comparable with photo-alignment, achieving a response time of 4ms and a panel aperture ratio improvement of 20% over existing technology3). The cost of modifying an existing LCD panel manufacturing line to handle the new technology is less than that needed for photo-alignment technology.
The problem is that residual monomers degrade reliability. If the monomers do not set fully, the LCD panel will exhibit uneven image quality.
Higher Reliability than PSA
Sony is developing a proprietary display technology called field-induced photo-reactive alignment (FPA). Like PSA, it irradiates the panel with UV light while voltage is applied, controlling liquid crystal molecule alignment. The main chain of the orientation film has two parts, one with strong affinity for liquid crystal molecules and the other which sets under UV light. The orientation film was developed in-house, and evaluation of prototype cells showed characteristics as good as or better than PSA.
One of the advantages of FPA is that it can be manufacturing with the same process as PSA, but there is little worry of reliability deterioration due to residual monomers. As Shunichi Suwa, Device Engineer of Core Device Development Group of Sony explains, "It can be manufactured by any panel fab already using PSA. In the future, we hope to provide it to panel manufacturers under license."
Improving Glasses Performance with OCB Liquid Crystal
Improving 3D TV image quality with frame sequential technology will require improving the performance of the glasses as well as that of the displays. The LCD panels used in glasses packaged with 3D TVs are mostly the same super-twisted nematic (STN) designs used in monochromatic displays, such as in calculators. They are inexpensive, but require a drive voltage of about 20V to achieve a response time of a few ms. In addition, they have a narrow viewing angle, with degraded display performance except when viewed straight-on.
In an effort to resolve these problems, Toshiba Mobile Display Co., Ltd. (TMD) of Japan has developed a new LCD panels specifically for glasses, using the optically compensated bend (OCB) method for fast response. Response is 0.1ms from shutter open to closed, and 1.8ms in the other direction, for minimal crosstalk.
"Even STN liquid crystal can deliver fast response if the drive voltage is boosted, but boosting it to 20V is just not practical. OCB liquid crystal is driven at about 6V, which is practical even in relatively low-power designs," says Tatsuya Miyazaki, Group Manager of LCD Divisionof TMD.
Panel transparency is a high 33%, which helps improve 3D imagery brightness. The contrast ratio is 5000:1 from the front, and 1000:1 at the maximum viewing angle of ±30°.
TMD has been volume producing OCB LCD panels since 2004, but prices are still high because they have been targeting commercial applications. TMD's Miyazaki believes that for the sizes used in 3D glasses, costs will drop when volume production hits 10 million units.
Xpol Support for Full HD Resolution
In addition to the frame sequential method, there are also display technologies designed for use in home 3D TVs, one of which is the Xpol method using a circular polarizing film.
Xpol technology offers low crosstalk thanks to a special polarizing film called Xpol, developed by Arisawa Manufacturing Co., Ltd. of Japan, on the front of the LCD panel. Odd pixel lines (running horizontally) are rotated clockwise, and even pixels line counter-clockwise, using circular polarization. Viewing glasses make it possible for the right eye to see only the odd lines, and the left only the even lines, again using polarizing films, producing the 3D image. The technology is already in use in 3D TVs from LG and Hyundai IT Corp. of Korea, and in commercial 3D displays manufactured by Victor Co of Japan, Ltd. of Japan, Panasonic and Sony.
Because both left and right eye images are present in the same frame in Xpol technology, there is minimal crosstalk. There is no time multiplexing of left and right eye images, unlike the frame sequential method, which is said to reduce the load on the human brain as it tried to synthesize the 3D image. Viewing glasses weigh only about 20g, no more than half as much as those used with frame sequential.
The problem is that resolution in the vertical direction is halved. It is possible to use "4K x 2K" display (a display about 4000 pixels x 2000 pixels in size) to minimize definition loss, but this is impractical considering the poor manufacturing yield possible.
Arisawa Manufacturing and Victor Co. of Japan have jointly developed the HR-Xpol technology capable of displaying 3D imagery at Full HD resolution, without a 4K x 2K display. The technology was announced in May 2010 (Fig. 8), and makes use of a liquid crystal layer that can be switched between left and right rotation, again with circular polarization.
Arisawa Manufacturing and Victor Co. of Japan have jointly developed a way of viewing 3D imagery at Full HD 1080i resolution, using circular polarizing film. A liquid crystal shutter alternates the polarization between left and right eye images one frame at a time.
In HR-Xpol the first frame is allocated in the same way as in the existing technology, with odd lines for the right eye and even lines for the left. The second frame uses the reverse, and the polarization state of the glasses is switched in synch. Two frames are synthesized to give show 1080i resolution Full HD 3D imagery.
By Shinya Saeki, Nikkei Business Publications
