[SID] Qualcomm Subsidiary Introduces Color MEMS Displays

Jun 5, 2009
Tetsuo Nozawa, Nikkei Electronics
James J. Cathey of QMT
James J. Cathey of QMT
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The 2.2-inch color panel
The 2.2-inch color panel
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The 5-inch color panel with a limited number of colors
The 5-inch color panel with a limited number of colors
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Still photo-like panels. Although the images on the screens cannot be changed, "they are not mockups but were produced with the mirasol technology," Cathey said.
Still photo-like panels. Although the images on the screens cannot be changed, "they are not mockups but were produced with the mirasol technology," Cathey said.
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The 4.5-generation glass for use in mass production
The 4.5-generation glass for use in mass production
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A closeup of the above glass. 1.4-inch panels are arranged in an array.
A closeup of the above glass. 1.4-inch panels are arranged in an array.
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Qualcomm MEMS Technologies Inc (QMT) announced June 2, 2009, that it will start the operation of its panel production plant in Taoyuan, Taiwan, June 15, 2009.

The announcement was made at SID Display Week 2009, an international academic conference on display technologies.

In collaboration with Foxlink of Taiwan, QMT has been building the plant for mass-production of panels based on its reflective display technology called "mirasol." The new panel uses the 4.5-generation glass.

Also, QMT announced that the mirasol display, which could only display text in black and white, is now capable of color representation.

Butterflies look more real

The mirasol display enables color representation based on a principle similar to a phenomenon where bubbles or other thin membranes look colorful due to interference of light. Specifically, MEMS-based minute resonators called "interferometric modulator (IMOD)," which serve as pixels of the display, enhance particular wavelength ranges in the reflected light, while attenuating or eliminating light with other wavelengths. The displayed color can be varied by changing the length of resonator (in the light incident direction).

According to QMT, the development of IMOD was inspired by the phenomenon that makes the scales on the wings of a butterfly show many different colors.

"The structure of the resonator is basically the same," said James J. Cathey, Business Development Vice President of QMT. "The only difference is that butterfly wings are not capable of modulation, but our IMOD is."

With color representation, the display is finally like a butterfly wing when compared with the monochrome model. The IMOD allows a short response time of approximately 10μs, which is about 1/1,000 that of the LCD technology, QMT said. This is because the resonator has a length of only several hundred nanometers, according to the company.

Thus far, QMT has developed two types of color panels that can display video images. One of them is a 2.2-inch model with a resolution of 384 x 288 (223ppi) and a frame rate of 30fps. The "mobile color depth" of the panel is 62,415. Mobile color depth is QMT's proprietary performance index that can comprehensively indicate the number of display colors, contrast ratio, etc.

"Video images like those posted on YouTube can be displayed without any problems," the company said.

Another panel is slightly larger than the first one. It is a 5-inch model with a resolution of 720 x 960 (242ppi). It operates at 30fps but has a limited variety of colors. Its mobile color depth is only 22.

In addition, QMT developed a "still picture" panel that is based on the IMOD technology but do not have the modulation function."

New performance index

Concurrently with the development of those color panels, QMT proposed some proprietary indices to indicate the display performance. One of them is the mobile color depth, an index to be used in place of color variation and contrast ratio.

"The existing indices of LCD performance, such as the color variation and contrast ratio, are based on the assumption that displays are used in dark rooms," Cathey said. "In a bright room, it means nothing no matter high these values are. On the other hand, the mobile color depth indicates the screen viewability in a typical usage situation of mobile devices. We should use this new index to compare mobile phones because they are often used outdoors."