I guess you could call it eye candy. Say hello to what's claimed
as the first—and only—polymer organic light-emitting diode (POLED) microdisplay. Developed by Scotland-based MicroEmissive Displays (MED), the "eyescreen" ME3204 is a full-color,
high-resolution microdisplay on a chip.
The ME3204 delivers ultra-low power dissipation and high-level image quality (in terms of contrast and pixelation). Neither
backlighting nor a driver chip is required. Polarization can be
dismissed as well, since it uses an emissive technology. And
there's no need for complex optics.
The unit provides QVGA resolution of 320 by 240 pixels in a
compact 6-mm (0.24-in.) diagonal array with 230,000 dots. It also
features a 4:3 aspect ratio. A fill factor (the proportion of the area
of each pixel that lights up) of about 80% frees moving color video
images from the distracting flicker and blurring that often are
experienced with other microdisplays. Video frame rates ranging
from 50 to 120 frames/s are possible.
The ME3204 measures a mere 14 by 10 mm with an integrated 50-mm flexible ribbon cable (). It operates from a 2.5-V
supply and dissipates 50 mW—about one-fourth the power dissipated by other competitive LCD microdisplays. That equates to a
theoretical life of 30 hours from a single alkaline AA battery,
which is crucial in the all-important power-consumption category
for microdisplay design. The ME3204 weighs less than other
microdisplays, too.
The product is rated to operate from -20°C to 60°C. It's fully
scalable to widescreen QVGA (WQVGA) resolution with a
widescreen 16:9 aspect ratio, which is something MED plans to
implement in the future (see "Color P-OLEDs Scale Up To 21-in.
TVs,"). Its present aspect ratio is currently the standard for
video glasses for TV on mobile and personal media players.
TIGHT INTEGRATION
The ME3204 integrates the drive
electronics and color filters (). It also contains a serial two-wire RGB interface and a parallel video interface that's compatible with the BT.656 standard, enabling a digital signal path. As such, product design engineers
can focus their efforts on software development.
The digital signal path removes the need for an analog-to-digital
converter (ADC) and eliminates loss in the dynamic range of composite video signals associated with analog-to-digital conversion.
All that's needed, if the application dictates it (e.g., projection displays), are magnifying optics.
HOW IT'S MADE
The ME3204 uses a patented structure
of P-OLED material layered on a silicon chip. The device is
based on a fabless design. The manufacturing process starts
by taking a mirrored and fully processed CMOS wafer that's
supplied by an outside source in Asia. This layer acts as the
active-matrix driver backplane.
Next, a series of nanoscale layers is deposited on the wafer.
One of these layers consists of the P-OLED material, which generates white light when a small current passes through it. The
cathode is then deposited as a thin transparent metallic layer.
After that, a protective inorganic thin-film
encapsulation layer is deposited over the
entire structure for protection from external elements.
The next step is to laminate the silicon
wafer to a glass wafer containing the patterned color filters, which filter the white
light to provide the RGB subpixels that
make up the color display. All of these
steps are performed in MED's manufacturing facility in Dresden, Germany. The final
step is to assemble and integrate the flexible cable, a process that's performed in a
plant in Asia.
P-OLED ROADMAP
Ian Underwood,
cofounder of MED and the company's
strategic marketing officer, sees the
ME3204 competing with transmissive
thin-film-transistor (TFT) LCDs and reflective liquid-crystal-on-silicon (LCOS) displays. He believes TFT LCDs don't scale as
well to small pixel sizes, where a lower
overall optical efficiency and a lower fill
factor (less than 25%) make pixelation artifacts more visible.
Moreover, only low levels of integration
are possible with TFT LCDs, since they
require more support chips. Underwood
also points out that reflective LCOS units
suffer from complicated optics and the
system complication of sequential color.
So where's the "eyescreen" ME3204
headed? Targeted areas include head-mounted displays and electronic viewfinders (). In fact, it already has found a
home in a variety of "near-to-eye" video
imaging products, including digital still
cameras and night-vision systems. Consumer applications for video glasses and
headsets enabled by the ME3204 include
DVD and video-clip viewing via personal
media players, handheld electronic gaming, and watching TV and surfing the net
via mobile phones.
"The confluence of mobile video broadcasting, video iPods, and advances in
microdisplays and optics now means the technology and application are much
more in line for a significant market opportunity in consumer video eyeware to finally
arrive," says Chris Chinnock, founder and
president of Insight Media, a market
research firm specializing in displays.
The product is being manufactured
under license from Cambridge Display
Technology (CDT), a developer of P-OLED
technology based in Cambridge, the U.K.,
and Japan's Sumitomo Chemical. Known
as Sumation, the joint venture allows MED
to manufacture the ME3204 using CDT's
proprietary P-OLED Technology and Sumitomo's materials and high-quality manufacturing expertise.
The "eyescreen" ME3204 costs $15.75
each in quantities of 1000.
MicroEmissive Displays
www.microemissive.com