By Chris Chinnock
PATUXENT RIVER NAS, Md. - A rigorous U.S. Navy testing program has concluded that naval program managers should continue buying active-matrix liquid crystal displays (AMLCDs) for command, control, and avionics applications.
Officials from the Naval Air Warfare Center Aircraft Division at Patuxent River Naval Air Station, Md., compared the performance of eight 20.1-inch LCD monitors to cathode ray tube (CRT) monitors. Although testers said CRTs still have better overall performance, they judged the deficiencies of the LCDs as "fixed, fixable, or can be reduced in impact."
Managers of several Navy platforms, such as the Lockheed Martin AN/UYQ-70 shipboard workstation and display system, as well as the Northrop Grumman E-2C radar aircraft, are considering the replacement of 19-inch CRT monitors with AMLCDs.
Three groups were interested in conducting the study: military operators, acquisition managers, and LCD monitor integrators, notes principle investigator Ken Sola. "My principle concern was that fielded LCDs would not hamper military operational effectiveness," Sola says. "We concluded that there would not be significant operational degradation with using LCDs."
In addition, acquisition managers needed more information on how well different monitors performed, and ways to specify them more effectively for future buys. LCD integrators wanted performance benchmarks to help improve their products. "I think we have gone a long way toward solving these needs too," Sola says.
The color 20.1-inch, 1,280-by-1,024-pixel displays, including a 10-element backlight, all came from NEC Electronics of Tokyo. Third-party system integrators added interface electronics, which reformat several data inputs for presentation on the display, along with packaging and other features such as shielding against electromagnetic interference.
Eight LCD monitors from seven system integrators were evaluated in the study. Performance was compared to two CRT monitors from different vendors. Operational tests were divided into the following functional areas:
- acoustic signal data;
- video (taped and generated);
- electro-optical live video;
- cold soak testing; and
- display photometric/radiometric characteristics.
Experienced naval operators rated display performance in several categories after viewing extensive data and imagery on LCD and CRT monitors. Evaluators said CRTs perform better overall than LCDs. Despite this, however, "there are no fundamental show stoppers," Sola says. "Many problems have been or are being fixed and others have work-around solutions."
As a result, the study formally endorses the fielding of the 20.1-inch NEC LCDs, providing they are properly packaged, interfaced, and procured form an accredited supplier.
Evaluators apparently were not expecting much from the LCDs, so their favorable ratings appear to have changed some perceptions and alleviated some of their concerns.
The larger viewable area, flat surface, wide viewing angles, and superior image quality with some types of data - particularly for text characters, synthetic-aperture radar imagery, and some acoustic data - are all positive attributes.
"In fact, I think even Ken [Sola] was quite skeptical about the LCDs at the beginning of this program, but he has changed his view now," says Maury Koelemay, strategic marketing manager at rugged display producer Codar Technology in Longmont, Colo.
Evaluators did find some deficiencies in LCDs. As might be expected with AMLCDs, they observed smearing of fast-moving video objects. This is a consequence of the type of liquid crystal material inside the display, as well as the device`s in-plane switching technology.
Unless major LCD manufacturers choose to improve this aspect internally - to produce displays for consumer TVs, for instance - then they must pursue alternative solutions. These alternatives may include modifying the drive electronics, maintaining the LCD at an elevated temperature, changing tactical operations, or supplementing the LCD with a CRT. This latter approach offers the least risk/cost option until the fundamental performance of the LCDs improves.
Evaluators also said the uniformity and dimming ability of the backlights need improvement. In particular, they said the displays are too bright at the lowest-luminance settings, which potentially can cause operator eye fatigue on long missions in darkened crewstations.
Neutral-density filters can help with the brightness problem, but this hinders sunlight readability, evaluators note. New backlight designs are under development, such as dual day/night versions, which should help with uniformity and dimming.
For some acoustic data, many of the LCDs exhibited an annoying flashing with each data update that can also cause eye fatigue. Some LCD integrators reportedly have a fix ready for this anomaly.
Evaluation of shielded and unshielded LCDs also turned up some interesting results. Evaluators found that metal mesh EMI shielding greatly degrades the visual performance of the display. They said a uniform indium tin oxide coating, however, is effective and does not impair the image.
Evaluators said monitor controls are another area for improvement. They say designers must give more thought to how users adjust their displays, including the use of on-screen menus. At a minimum, evaluators recommend that designers include controls for display contrast, brightness, and color saturation.
Testing also pointed out the wide variety in performance of the LCD monitors. Even though they all used the same LCD glass, different implementations of the interface electronics, controls, and other features resulted in enormous differences.
Program managers within the Navy have received the testing program well, Sola says, adding, however, that Navy officials should better coordinate the way they specify and procure LCDs.
He also recommends that the procurement process include LCD prototypes - a proposition that may not sit well with potential vendors. "This could hurt smaller suppliers " says Codar`s Koelemay. "Unless it is a big opportunity, we would be hesitant to make a large investment in a prototype."
The final report is available from the Naval Air Warfare Center Aircraft Division in Patuxent River, Md., report number: NAWCADPAX-98-XX-TM, The Liquid Crystal Display (LCD) Evaluation.
The RFD 251 flat-panel display from Barco Inc. has been rated one of the best for airborne applications by officials of the U.S. Naval Air Warfare Center at Patuxent River Naval Air Station, Md.
