Going Beyond the 100-in. Display
This month, we look at some selected topics related to large-area displays. The term is somewhat subjective, especially in an era where flat-panel TV sets 32 in. and larger are commonplace, and practically every public area in the world features at least one 42-in.-or-larger display of some kind. However, it was not that long ago when 21-in. CRT monitors were considered to be large displays, and LCD modules were available mostly in sizes 15 in. and below. The term "large-area display," therefore, has traditionally applied to almost anything greater than 25 in. on the diagonal and to applications ranging from consumer projection television and public signage to cinema screens and giant stadium displays. Historically, there have been several approaches to making large-area displays, including electromechanical technology, projection systems, discrete emitters such as tubes and LEDs, and tiling. Tiling – arranging multiple direct-view panels or projection screens into a seemingly continuous, very large video display – has proven to be one of the most popular, used extensively with both projection systems and CRTs.
In a world where LCDs and plasma-display panels (PDPs) are routinely manufactured in sizes of 50 in. and larger and have been demonstrated in sizes exceeding 100 in. on the diagonal, it may surprise some that tiling technology remains relevant and interesting. However, even at these largest sizes, LCDs and PDPs can serve only a portion of the market for large-area displays. For example, the digital-signage market – with annual revenues of more than $1 billion and better than 30% growth each year – continues to push for ever-larger displays with constantly improving video quality. Accordingly, the traditional solution of tiling continues to garner a great deal of interest and developmental work. I was pleasantly surprised to learn about the latest advances in tiling technology applied to LCDs and even more excited when SID Past President Tony Lowe agreed to write a feature article surveying the state of the art in tiling technology. As you will learn from his article, recent advancements in tiling have helped overcome traditionally difficult problems – notably the dead space between panels that cannot be easily eliminated, disrupting images that cross the boundaries so that they do not compare favorably to a single continuous display. An interesting twist on the story is that because of all the investment in large substrates and the nature of the LCD-panel market, the industry may find that using large numbers of tiled 15–20-in. LCDs rather than fewer larger LCDs may be more economical, opening up a whole new market for notebook- and desktop-sized panels.
Another major challenge facing the large-area-display community is that of color rendering and how to accurately produce the intended color on the display. With numerous benchmark color gamuts being defined in technical standards, and practically every display design having its own native color palette from which to draw, sorting through all the science, standards, and user preferences to design a system that produces the "right" color has become a dizzying problem. The predicament is especially acute when designers implement highly saturated primary colors from sources such as LEDs, or multiple additional primaries such as cyan and magenta, to produce an expanded color gamut that goes beyond traditional CRT phosphors. For example, what does it really mean when a projection system is specified to display "110% of NTSC" color gamut, and how can the mixed colors in the video be reproduced exactly the same as the producer intended? Longtime-industry-expert Matt Brennesholtz explains the science and sorts out some of the mystery of display colorimetry in the first piece of his two-part tutorial series on this vital subject. This month's article sets the foundation of colorimetry for video and display systems. Matt makes some valuable recommendations for improving the specification of color-gamut size in displays as well as unifying their color performance.
While OLEDs are not a large-area technology today, we have seen demonstrations as large as 30 in., and clearly the goal is low-cost production on very large substrates. In this month's Business of Displays column, Steve Sechrist explores the potential significance of DuPont's breakthrough in solution processing of OLED materials. At SID 2006, many significant advances were reported in all aspects of OLED technology, so the large-area part of the OLED story may be quite a bit closer to reality than it was 1 year ago. When that happens, one more technology will be added to the large-area-display equation, one that will continue to bound beyond the largest single-panel LCD or PDP. Of course, challenges remain, but as the articles in this issue demonstrate, the constant demand for larger and larger displays means that the display industry may have just scratched the surface of what large-area displays can become – and that notion should excite everyone in our business.
– Stephen Atwood