Qualcomm MEMS Technologies (QMT) has been showing its mirasol 5.7-inch, 1024 x 768, reflective color display for more than two years, but design wins were slow in coming. In fairness, the introduction of the original iPad caused many people in the eReader and tablet PC space to rethink (or cancel) product plans. Nonetheless, the long delay has caused some display watchers to think dystopian thoughts, with at least a couple of them wondering if Qualcomm’s purchase of Pixtronix meant QMT was giving up on mirasol and looking for an alternative MEMS technology.

Not so, QMT executives told me at CES 2012. There are now three European eReaders with mirasol displays, along with the Korean-market Kyobo eReader. In addition, Chinese content provider Shanda will soon be offering the Kyobo hardware, but renamed Bambook.

QMT has been limited to relatively low-volume customers because all displays are made on the company’s Gen 4.5 pilot line, which has limited capacity. QMT is spending $2 billion on the production fab, which has four Gen 4.5 lines and will ramp up later this year. High-volume customers will have to wait for that. It will probably be 2013 before mirasol-containing products will reach the U.S. market.

Qualcomm’s Emily Kilpatrick told me that the $2 billion investment should be convincing evidence that Qualcomm is serious about mirasol. "We have a long-term commitment," she said. When I mentioned the speculation of some analysts that manufacturing yield might be a problem, Kilpatrick said "We are where we should be. The processes are healthy and robust."

In the Kyobo eReader, the mirasol display is used as a color eBook display. Although optical response time is inherently fast, frame rate seems to be quite low to extend battery life. I was told that 30 minutes of reading per day results in about 3 weeks of battery life between charges.

I have come into possession of a Kyobo e Reader (by a circuitous but entirely legal route). There things the device won’t do outside of South Korea, but it is possible to load ePub and PDF files directly onto an micro SD card for the device to display.

So what is it like using a mirasol display over a period of time. By default in the Kyobo eReader, the mirasol display is illuminated by a front edgelight. The edgelight dims as the ambient becomes brighter. The display was clearly readable outdoors yesterday here in New England, when the sky was cloudy but quite bright.

As manufacturers experiment with various cross-breedings of eReaders and tablets, some with unconventional display technologies optimized in various ways, it will not be reasonable to expect every display to have the color depth, color gamut, and viewing angle of a TFT-LCD. Mirasol doesn’t, but it gives you extended battery life, a reasonable amount of color, and sunlight readability instead.

The display has a pinkish white point when viewed straight on, which turns lightly greenish at relatively low horizontal viewing angles. At relatively low vertical viewing angles, the white point goes to greenish gray. The effect is somewhat different when viewed under primarily reflective external light compared to primarily edge-lit. This shouldn’t be surprising. Color is produced by optical interference in the mirasol, and changing the angle of incidence will change the optical path.

There is a glass face on the Kyobo eReader, which seems to have a slightly matte surface. Even so, there are significant reflections.

As the mirasol color display appears in its first group of customer products, it offers an interesting assortment of attractive features, as well as some weaknesses. It will certainly find a place in suitable customer products, but it will not be a universal solution. It is, however, an interesting intermediate between E Ink displays (excellent print readability, low power, low refresh speed) and TFT-LCDs and AMOLEDs (beautiful color, high refresh, but relatively high power consumption).

Reply to the author