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LCoS Display Technology Shoot-Out: Part AIntroduction to LCoS Technology
Liquid Crystal on Silicon, LCoS, is a relatively new and obscure display technology that is now making its grand entrance into the HDTV marketplace. What is really impressive is that instead of taking the traditional path of entering at the ground floor with mediocre performance compared to the established technologies and then trying to percolate up to the top tier in picture quality, it is starting out right at the very top. Already, LCoS provides the highest resolutions, the highest non-CRT Contrast Ratios, and the most artifact-free images of any display technology. For people that are sensitive to flicker and eye-fatigue, LCoS operates at the highest refresh rates (120 Hz) for the smoothest most flicker-free images. This article will be an in-depth examination of 5 LCoS HDTVs, all but one of them prototypes, in order to get an early look into this unfolding technology.
Of course, LCoS isnt really brand new because its been under development for more than a decade, and JVC has actually been shipping high-end professional front projectors with this technology since 1998, but its been a relatively low-volume niche market until now. Its also been a very difficult technology to perfect and quite a few companies have either given up or gone bankrupt trying. Thomson (under the RCA brand) produced the first commercial LCoS HDTV in 2001, followed by Toshiba (using Hitachi LCoS chips) and then Philips, but all of them had dropped out by October 2004. Intel shook the industry in January 2004 by announcing that it would begin manufacturing LCoS panels but then abandoned the project in October 2004 before anything was shipped. As a result, the future of LCoS was being questioned by many analysts, but the technology was merely regrouping for its real launch into the HDTV marketplace.
The second generation of LCoS began when JVC launched their first rear-projection 1280×720 High Definition TVs in July 2004. Sony joined in January of 2005 with their high-end 1920×1080 Qualia unit. Next came Brillian, which began shipping their 1280×720 unit in mid-2005. As Im finishing this article there are only a few LCoS HDTV models available for purchase worldwide. However, JVC and Sony recently announced their second generation HDTVs and LG its first (with SpatiaLight LCoS panels). Another major LCoS player is Hitachi, but they postponed (indefinitely) the November 2005 launch of their 60 and 70-inch LCoS HDTVs. For this article we were fortunate to have been able to test and evaluate a number of pre-production prototypes, so this is where our story begins?
Even if youre an expert its hard to find a place where you can evaluate the image and picture quality of an HDTV. At a tradeshow or in a manufacturers showroom youll most likely be watching source material that has been carefully selected and possibly fine-tuned in order to make the particular model look better than it normally does. In a retail showroom the viewing conditions, ambient lighting, video signal quality, and quality of the video source material are often variable and not as good as they should be. The HDTVs themselves are also frequently not properly adjusted (sometimes because a previous customer was playing with them). Frequently, youll see cartoons being played because the saturated colors and artificial images make most TVs look deceptively good.
The best way to evaluate the image and picture quality of any display technology is to bring together as many units as possible and test them simultaneously side-by-side under carefully controlled conditions, with all of them showing exactly the same high quality content. Youll need ideal viewing conditions, D6500 ambient backlighting, outstanding video source material and a state-of-the-art video signal distribution system. Next have the top engineers from each manufacturer carefully setup and adjust their units for optimum image and picture quality. Thats exactly what transpired here during the entire month of July 2005. It was a major undertaking but the results are quite interesting and definitely worth all of the time and effort.
An event like this is called a Shoot-Out. Its not a battle to the end but does present the greatest of all challenges for any display because individual units that may look fabulous when viewed all by themselves will generally look no where near as good when surrounded by many other great sets showing the same high quality content, because even subtle differences really stand out. For the Shoot-Out we started by challenging the units with hundreds of DisplayMate High Definition test patterns (www.displaymate.com) in both the native 1280×720 and 1920×1080 HDTV resolutions. We then carefully measured the photometry and colorimetry for each of the units using two high-end spectroradiometers. For the viewing tests we had 34 Jury Panelists come by to compare and visually evaluate the units by watching a 1+ hour program of very high quality video source material. Figure 1 shows the Shoot-Out setup with the lights turned on. The units were lined up along a 35 foot wall near my home theater.
|Figure 1. The Shoot-Out with the lights turned on. From left to right: JVC Consumer 720, Brillian 720, JVC Professional 1080, CRT Studio Monitor, eLCOS-JDSU 1080, and Brillian 1080 units. Photograph by David Migliori.|
Outline of the Article
This is a four-part article series. In Part A we'll start off with a description of the HDTV units that we tested and then provide an overview of LCoS technology. In Part B we'll continue with a discussion of How We Tested and then examine the photometry and colorimetry of the units in detail, which provides a quantitative assessment of their color and gray-scale accuracy. In Part C we'll start with a revealing Test Pattern analysis followed by a description of the extensive Jury Panel testing and then provide individual Assessments for each of the units, including Jury evaluations and comments. In Part D well start with an Assessment of LCoS technology, followed by detailed technical performance comparisons between all of the major display technologies: CRT, LCD, Plasma, DLP, and LCoS, and well finish with a discussion of the most exciting new developments in display technology that will be the subject of future articles in this series. There are two sidebars: one in Part A for the HDTV manufacturers and one in Part B for the manufacturers that provided supporting hardware and software for the Shoot-Out.
Note that this article is the latest in a series of Display Technology Shoot-Out articles that have covered CRT, LCD, Plasma and DLP display technologies. The topics for the original series are: Part I: The Primary Specs, Part II: Gray-Scale and Color Accuracy, Part III: Display Artifacts and Image Quality, and Part IV: Display Technology Assessments.
The HDTV Units Tested
When we started planning the Shoot-Out there were just two shipping LCoS HDTVs available, so I decided to enlarge the sample by persuading several manufacturers to loan me their precious laboratory prototypes for the article. The goal was to include every LCoS manufacturer that could provide a working unit (that didnt use a color wheel) there were only five candidates: JVC, Sony, Brillian, eLCOS and SpatiaLight. There are other LCoS HDTV brands available but they use components from these manufacturers. We included units from both of the standard HDTV resolutions: 1280×720, which is roughly 1 mega-pixel, and 1920×1080, which is roughly 2 mega-pixels. They will be referred to as 720 or 1080 units throughout the article. (The progressive signal designation ?p is unnecessary here because all of the units are internally progressive devices. See below.)
JVC and Sony require no introduction but the three others are unknown to most consumers. Brillian is small startup company based in Tempe, Arizona and is the only HDTV manufacturer in the USA. They provided a prototype of their 65 inch 720 unit (model 6501m, which is now shipping) and then worked hard to deliver a 1080 prototype unit (model 6580i, which is now shipping) in time for the start of the Shoot-Out. eLCOS is another small startup company that worked with light engine manufacturer JDS Uniphase, screen manufacturer DNP and video processor manufacturer Silicon Optix to deliver a 56 inch 1080 laboratory demonstration unit. Note that their unit is not classified as a prototype because its not engineered to be a mass produced product. SpatiaLight is another small startup company that is supplying the LCoS panels and drive electronics used in the LG 71 inch 1080 HDTV that was announced in September 2005, but as of March 2006 the model is only in limited production, and its future status remains uncertain. SpatiaLight agreed to participate but was unable to deliver a prototype in time for the Shoot-Out.
JVC sent two units: the Consumer division sent their shipping 61 inch 720 HDTV (model HD-61Z886), which has a street price under $4,000, and the Professional Products division sent a prototype of their 48 inch 1080 Reference Monitor (model DLA-HRM1, which is now shipping) designed for television and movie post-production studios. Its priced for the high-end professional market and is competitive with Sonys high-end professional CRTs, with which it is designed to compete (well compare them in Part D). Note that the LCoS technology and devices in the two JVC units are significantly different: the Consumer unit has a digital backplane that controls each pixel with Pulse Width Modulation (see Part III and below), while the Professional unit uses analog voltage to control each pixel (see below). Sony began shipping their 70 inch 1080 Qualia 006 in January 2005, and their second generation 50 and 60 inch XBR units are now shipping. We invited Sony but they declined to participate in the Shoot-Out.
Information about each of the participating manufacturers in the Shoot-Out appears in a special HDTV Manufacturer Sidebar. Basic information for each model is included in Table 1. Note that the order of the units in the table is alphabetical according to resolution. The dual entry for the price of the JVC Consumer unit lists both the Manufacturers Suggested Retail Price and the lowest reliable actual selling price that I could find. All of the other units are expected to sell (in the immediate future) for the prices listed in the table.
LCoS is the newest display technology to use Liquid Crystal for controlling pixel brightness in an image. The most common forms of Liquid Crystal technology are found in the large amorphous silicon LCD panels that are used in direct-view computer monitors, TVs and HDTVs. They typically range in size from 5 inches up to 100 inches (the record holder as of March 2006). Next are the much smaller high temperature polysilicon panels used in video and data projectors. They are only about 1 inch in size and are found in all large screen LCD rear projection TVs and HDTVs. In both of these technologies the light source is behind the panel and light has to travel completely through it, back to front, including through all of the electronic circuitry and components within the panel that are needed to control the individual pixels. These block a lot of the light and create gaps between the pixels. The higher the resolution the greater this problem becomes. A second major issue is that the Liquid Crystal needs to be relatively thick in order to deliver high contrast. That slows its response time, which leads to some smearing when there is motion or change in the image.
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