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Avionics display tech breaks into TV

Posted: 01 May 2007 ?? ?Print Version ?Bookmark and Share

Keywords:TMOS display technology? display technology for avionics? energy-efficient display technology?

A novel display technology that claims to be simpler in construction than an LCD and better-performing than OLEDs or plasma appears to be inching closer to commercialization.

UniPixel Displays Inc. developed its Time Multiplexed Optical Shutter (TMOS) technology to address display requirements in avionics applications, particularly heads-down cockpit deployments. The U.S. company has engineering prototypes and expects "to have the display in a TV application by Q4," said CFO James Tassone.

Separately, work is progressing on OLEDs as Universal Display Corp. (UDC), in particular, starts to concentrate its phosphorescent OLED technology on lighting applications. With lighting accounting for more than 22 percent of the total electricity produced in the U.S., the inherent characteristics of OLEDs position them as an energy-efficient alternative, according to UDC.

UniPixel has been working with Xerox Palo Alto Research Center, Lockheed and Sandia National Laboratories in developing TMOS, said Tassone.

The company has completed $12 million in private financing with Tudor Investment Corp. "UniPixel's unique TMOS approach to color display technology is both revolutionary and disruptive," said Rob Broggi, a VP at Tudor.

Indeed, "While most new display technologies don't offer a clear and substantial added value to potential customers and end users, UniPixel certainly seems to," said Ken Werner, senior analyst at market research firm Insight Media. "The structure would seem to offer much lower cost than LCD."

20-year rule
But the road to a commercial product may not be smooth, Werner warned. "The fact that the UniPixel proprietary sandwich can be made with roll-to-roll processing is a big plus, but questions of uniformity and cost still have to be answered," he said. "Even if the answers to all these questions are reasonably positive, it typically takes a long time for system makers to assure themselves that they want to take a flyer on a new technology and for panel makers to sign on. My '20-year rule' says that no display technology goes from concept to high-volume application in less than 20 years."

Traditional displays use three closely spaced dots displaying different intensities of red, green and blue to create what the human eye perceives as a single color, in a technique called spatial additive color. UniPixel's TMOS, by contrast, is based on temporal additive color. Short bursts of red, green and blue light are emitted through the same dot so quickly that the eye also sees them as a single color. But in this case, different durations of red, green and blue light create different shades and hues.

According to Killion, a UniPixel display consists of just six layers, compared with 15 for plasma and 30 for LCDs, and takes only 12 steps to manufacture, vs. 128 steps for an LCD. Using a "frustrated total internal reflection" technique, red, green or blue light enters a light guide from the edge of the display. The display structure enables daylight readability.

The colors cycle for an equal amount of time in very rapid succession, reflecting off a mirror at the opposite edge that scatters the light and produces a uniform distribution across the display. Materials used in the construction of the light guide keep light from escaping, so that total internal reflection is achieved, according to the company.

A simple lens/shutter mechanism is constructed above the light guide by sandwiching the microlens and standoff layers between transparent conductors. When the two conductive layers are oppositely charged at any given pixel, they attract. The lens is squeezed down through the standoff layer.

When it touches the light guide, the pixel is activated, and light escapes at that point. The duration of the charge controls the opening and closing of the "shutter." At any given pixel, this duration determines the relative intensity of the color.

UniPixel is so sure that TMOS will have the edge over the entrenched flat-panel technologies that it expects to fight LCDs and plasma for a piece of a market that industry analysts peg at $107.4 billion by 2008.

Volatility of OLED shipments reflects performance of competing flat-panel suppliers.

Solid-state lighting
Meanwhile, the U.S. Department of Energy's Solid-State Lighting (SSL) program is working to accelerate advances in lighting technology.

At the Solid-State Lighting Workshop in February, the U.S. Department of Energy (DOE) recognized Brian D'Andrade of UDC and Mark E. Thompson of the University of Southern California (USC) for their leadership in white OLED technology for lighting.

D'Andrade led a team that achieved record quantum efficiency in a white OLED. The UDC group demonstrated a white OLED device with an external quantum efficiency of 30 percent operating at 850nits. Light extraction was improved by using novel outcoupling fixtures developed under a DOE grant. As a result, UDC was able to obtain an efficacy of 30lumens/Wtwice that of an incandescent bulb. The achievement represents another step toward the DOE's long-term SSL research goal of 160lumens/W in a cost-effective, market-ready, white-lighting OLED product.

Thompson, a research partner with UDC and chairman of the chemistry department at USC, was recognized for leading a team that developed a white OLED device made using a combination of red and green phosphorescent materials with a blue fluorescent material. Thompson's white OLED achieved 24lumens/W, with improved lifetime and color stability over a standard OLED.

"While not large in dollars, this program makes sure UDC is in on the ground floor in solid-state lighting, which is going to be a huge application," said Insight Media's Werner. He noted that the first LEDnot OLEDautomobile headlights are appearing on show cars and could be in production in a year or two.

While the superior characteristics of OLEDs are well-known, manufacturing remains a stumbling block. In Germany, Novaled is leading the way in making OLED manufacturing practicable. The company is working on the so-called Rollex (roll-to-roll production of LEDs on flexible substrates) project, funded by the Federal Ministry of Education and Research, to develop technologies for the production of highly efficient, low-priced OLEDs. The roll-to-roll-concept is expected to lower coating costs for the general lighting market in comparison with the cluster or in-line schemes used for display production.

"Light sources based on organic electroluminescent materials offer the potential to make a high light intensity possible at a low energy consumption on mechanically flexible substrates," said project head Karl Leo.

- Nicolas Mokhoff
EE Times

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