Home Theater: Plasma vs Projection Display
Larry Weber, Plasmaco and Ed Stupp, Stupp Associates
(Moderated by Terry Nelson, Panasonic Technologies, Inc.)
Digital television systems are beginning to be available as consumer products. To take maximum advantage of the improved picture quality afforded by such systems, larger displays are also needed. CRTs will probably continue to be used below screen diagonals of 40-inches. For home-theater applications requiring screen diagonals in excess of 40 inches, plasma displays and projection systems currently seem to offer the most promise.
A panel discussion on the relative merits of these two technologies was held during an evening meeting of the Mid-Atlantic Chapter of the Society for Information Display (SID-MAC) on February 17, 1999 at Schott Corp. in Yonkers, NY. About 45 people attended, and a lively discussion went on for 2 hours. Numerous discussions were still going on in parallel at least a half-hour after that. Attendees also enjoyed a very nice complimentary Chinese food buffet before the meeting, and it was clear that the arrangements provided by Schott and by SID-MAC's Chair M. Anandan of FED Corp. and Secretary Ravi Rao of Plasmaco were much appreciated.
The debate featured two well-known experts on these subjects. Larry Weber (left) is an SID Fellow who began researching plasma displays at the University of Illinois in 1969. He founded Plasmaco in 1987 and has given tutorials on plasma displays in SID's annual seminar program numerous times. Ed Stupp (right) was Research Department Head, Display Systems, at Philips Research in NY until he founded Stupp Associates in 1998. Ed has given SID seminars on projection components and displays, and he co-authored (with Matt Brennesholtz) a recent book  on the subject for the Wiley SID Series in Display Technology.
Larry Weber spoke first, and he agreed that 40 or 42-inch VGA (640x480) plasma monitors currently cost more than $10k. He said that about 70% of this cost is for the panel itself and the rest is for the electronics. Larry expects this ratio to be reversed eventually. The reason that the panels are so expensive now is that they are unlike any other mass-produced article except possibly CRT shadow masks. When the cost of the electronics becomes dominant, Larry thinks cost can be pushed down some more with more efficient discharges and better internal optical coupling to the phosphors.
Larry expects the home theater-market for plasma displays to take off when they can be sold for about $2500 because this is what people are willing to spend for a state-of-the-art personal computer. The conventional wisdom of learning curves  suggests that cumulative production will have to double about 6 times from the current level of perhaps 15,000 units. Thus it appears that a moment of truth may come when cumulative production reaches about 1 million units. Unfortunately, current panels are not as versatile as one could wish because their phosphor screens are easily damaged by static images. This limitation will make it harder to find non-television applications that might support the initial high cost for these displays.
Another highlight of the plasma story was the demo. Jane Birk had arranged for a Plasmaco 42-inch, 4x3 VGA panel to be in the conference room where the meeting was held. The demo seemed to have been done right, with a Panasonic D5 digital tape unit serving as a source of progressive-scan video (480p). Even from 2 or 3 feet away, the picture quality still looked good, and at that distance the display area seemed huge.
Ed Stupp emphasized the need for 16x9 displays if the FCC's vision of the market pans out. Ed said the factory cost of what he calls SD, 4x3 rear-projection displays (704x480 pixels) that are based on CRTs is about $1200 now. This may be an interesting price point, but these sets are relatively large and heavy. Even using a light-valve approach, it is hard to get the depth of a large-screen, rear-projection system less than about18 inches. This is about the same depth as today's 27-inch direct-view CRT TV sets. Ed pointed out that consumers traditionally do not rearrange their furniture to accommodate a new TV, regardless of its screen size. This means that HDTV will require screens measuring at least 55-inches diagonally for viewers to be able to resolve the increased detail at the usual (US) viewing distance of 3 meters.
Ed gave the highest marks to front-projection units built with 3 light-valves, one for each color, to maximize the light output. The light output of these systems is high enought for a contrast ratio of 40 to 60 to be achieved in a lighted room. This is comparable to the contrast ratio today's direct-view and rear-projection systems achieve. Good contrast in an lighted room is necessary because people often read at the same time they watch TV.
Ed sees different technologies at different price points in future home-theater systems. He expects the lowest price (1st quartile) digital receivers to be 34 or 36-inch, direct-view CRTs or rear projectors using 3 CRTs. Rear-projection systems will likely occupy the 2nd quartile, mainly using 3 CRTs but possibly single light-valve systems as well. Light-valve systems may dominate the 3rd quartile, mainly using a single light valve, but there could be some systems using 3 light valves. In the 4th quartile, Ed expects to find HD projectors using 3 light valves and plasma displays of comparable resolution. He defines HD resolution to include 1280x720 as well as true HDTV resolution of 1920x1080 pixels. Ed said that 4th-quartile, home-theater projectors should cost around $4500 five years from now.
In rebuttal, Larry said he believed that plasma displays will probably not be cheaper than projection displays, but they will provide a higher performance alternative that will be attractive for HDTV applications. Maybe the sharpest disagreement came when Ed said that people actually prefer the bright center and dim edges that are characteristic of CRTs and, to a lesser extent, projection systems. Larry said that, in his experience, people are surprised to see how non-uniform CRTs look when placed next to a plasma display showing the same images. On the other hand, Larry conceded that the infrastructure for making masks for plasma displays larger than about 60-inches in diagonal does not exist yet.
By the way, IBM's Bob Melcher said there is an unsolved question about the inherent (dark-room) contrast required for video projection in a lighted room. You would guess that 100 to 1 should be enough, but projectors typically do 350 to 1 now, and the video quality is noticeably better.
The debate seemed to end in a draw. Projection systems have been sold for many years, but production still lags that of direct-view CRT TVs by a large factor. Large-area plasma monitors may have better performance in certain respects, but they are still much too expensive. The one thing that seems clear is that the improved picture quality provided by digital television systems makes the race to develop bigger screens worth keeping an eye on.
By the way, an interesting controversy erupted in December when Forrester issued a press release  claiming that "standard definition digital television (SDTV) will succeed where HDTV fails by offering an affordable digital TV experience." The Consumer Electronics Manufacturer's Association responded referring to a press release  of its own, saying CEMA's research indicates the opposite is true.
1. Edward H. Stupp and Matthew S. Brennesholz, Projection Displays, Wiley SID Series in Display Technology, John Wiley & Sons, New York, 1998.
2. Shlomo Maital, MIT Advanced Study Program, Economic Concepts for Engineers and Managers, Session #8 Learning Curves.
3. Michael Shirer, " Forrester Research Predicts HDTV Will Fail", Cambridge, MA (December 8, 1998).
4. "Consumers Want HDTV," Consumer Electronics Manufacturers Association (CEMA), Arlington Heights, VA (January 8, 1998).
(last updated August 17, 1999)
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Copyright 2003, Terence J. Nelson