Active matrix electroluminescent displays show promise
BEAVERTON, Ore. - Active Matrix electroluminescent (AMEL) displays are one of perhaps a dozen competing technologies the emerging miniature display category. But AMEL`s status came up a notch recently when the technology`s developers, engineers at Planar Systems Inc. of Beaverton, Ore., announced they had received a pre-production order to supply VGA-resolution AMEL displays for the U.S. Army`s Land Warrior system. If all goes as planned, the program could require 75,000 to 150,000 displays over
By Chris Chinnock
BEAVERTON, Ore. - Active Matrix electroluminescent (AMEL) displays are one of perhaps a dozen competing technologies the emerging miniature display category. But AMEL`s status came up a notch recently when the technology`s developers, engineers at Planar Systems Inc. of Beaverton, Ore., announced they had received a pre-production order to supply VGA-resolution AMEL displays for the U.S. Army`s Land Warrior system. If all goes as planned, the program could require 75,000 to 150,000 displays over it`s six-year life.
AMEL displays are entirely solid state devices. Designers fabricate underlying drive electronics in traditional silicon integrated circuit foundries, with the light-emitting phosphors deposited in a pixelated matrix on top.
In addition to their small size, AMEL`s main advantage is its inherent environmental ruggedness. AMEL devices can withstand high shock and vibration, as well as wide extremes in temperature: -40 to 75 degrees Celsius for the 0.75-inch VGA display used on the Land Warrior program.
For Land Warrior, Planar experts will supply AMEL displays to designers at Honeywell Sensor and Guidance Products Division in Minneapolis, who are responsible for the development and production of the Integrated Helmet Assembly Subsystem (IHAS), which essentially consists of a combat helmet with an attached display module and a computer in a backpack.
Operators can use daytime and a nighttime modules with IHAS. The monochrome AMEL display can show maps, text, or symbology, which combines with additional imagery for presentation to the soldier.
For the nighttime module, this imagery comes from a night vision tube. For the daytime module, images from the either soldier`s thermal weapon sight or video from a miniature camera, can be displayed. The backpack computer coordinates the display of the imagery and symbology to the IHAS.
Early operational tests of IHADs confirmed that the device was rugged enough to withstand use by ordinary soldiers. Now, contractors are gearing up for the next phase, initial operational test and evaluation, which will start this spring. "This is the phase that evaluates the devices prior to a full production order. We believe that around 100 of the display modules will be evaluated in the field," says Bill Sproull, general manager of Planar`s Miniature Display Business Unit.
Over the last five years, Planar developers have received significant support from the U.S. Defense Advanced Research Projects Agency in Arlington, Va., the Army`s Soldier Systems Command, and the Navy to develop the AMEL technology. These efforts have successfully led to the establishment of a fully qualified ISO 9001 production line for the 0.75-inch VGA AMEL display. That device features pixels that are 24 microns across.
By next summer, Sproull says Planar engineers should be moving their next generation AMEL technology into production. This will halve the pixel spacing to 12 microns, and enable designers to fabricate displays of 1,280-by-1,024-pixel resolution in the same footprint as the current VGA model.
Color displays are coming too. Using a liquid crystal color shutter approach, designers should be able to build VGA color displays by mid-1998. The color subtractive stack adds about a one-fourth inch in thickness but can provide 512 colors, which is sufficient for many mapping and symbology applications. A color filter approach is also under development, but it reduces resolution by one-third.
Systems designers are likewise evaluating AMELs for military gear such as laser rangefinders and mine detection equipment. But to reduce costs, Planar engineers are looking to move AMEL technology into high-volume commercial and industrial applications. For example, VGA development kits now cost $3,000, but prices in the $100-to-$200 range are thought necessary for a sustainable market.
Designers at Kopin Corp. in Taunton, Mass., have recently taken the lead position among the miniature display vendors with the announcement of several major developmental agreements for consumer products. For example, engineers at Japan-based FujiFilm Microdevices Company Ltd. are developing digital camera chipsets that will use Kopin`s one-fourth VGA liquid crystal CyberDisplay. Smartcard viewers and cellphone products are also being developed at Gemplus, Motorola and Siemens. CyberDisplay volume pricing for these customers is thought to be far less than $100.
Planar leaders are closely following progress with Kopin`s partners and will be ready to respond if a mass market becomes a reality. "A year ago most miniature display makers would not have believed a market for one-fourth VGA displays existed. But the market hasn`t proven itself yet with large production orders," Sproull notes.
Glen Kephart, Kopin`s vice president of display marketing, concedes that his designers are still in the early phase of prototype production, and that they have no commitment for volume production. "The intent of these agreements however, is to develop products that can be brought into full production," Kephart notes.