This week at the O-Reilly Emerging Technology conference in San Jose CA, Dr. Mary Lou Jepsen, founder and CEO of Pixel Qi (San Bruno, CA; www.pixelqi.com) talked about development of the company’s unique 3T display. It will switch between full color, and a low power display, and is claimed to be as readable in sunlight as electrophoretic displays used in E-book readers. A third mode allows low power but with video.

Paul Beatty
Analyst

Its website mentions e-paper screens with color and video saying "Our first screens will be 10" diagonal screens for netbooks and ebook readers that will sample in Spring 2009 and ship in high volume in Summer 2009. These screens rival the best e-paper displays on the market today but in addition have video refresh and fully saturated color. The e-paper mode has 3 times the resolution of the color HDTV mode allowing for a high resolution reading experience without sacrifice to super color fidelity for graphics. In addition, these screens can be used in sunlight. Look for them in the market in the second half of 2009".

At the conference, Jepsen noted that the triple mode capability was a funded project, but hinted that a product remained some way off.

Pixel Qi has access to Dr. Jepsen’s US Patent Application 2008/0117346 published last May on a dual mode LCD. Sub-pixels only have green rather than all three color filters, and use a reflector that covers about 2/3rds of the pixel. With the backlight off, the display reflects ambient light to create a monochrome display. This architecture does not need a black matrix between color filters, which lowers costs and increases reflectance, but it does require polarizers, which absorb at least half the light (something electrophoretic e-paper does not have to worry about).

But part of each sub-pixel is open to allow light from a backlight to pass through each sub-pixel. Red, blue and white LEDs are used in the color sequential backlight with red and blue light passing through the LCD directly, but the white LED light passes through the a green filter.

Power savings arise from the ability to use the display without a backlight (in monochrome if ambient lighting is good enough), and, if the backlight is used, the LCD runs at a lower frame rate and can run in two-color rather than three-color sequential mode, further saving power. Remember, inmost LCD displays CCFL or LED backlights are on all the time using color filters, which is not the most efficient approach. Other power savings are said to arise from use of transistor-transistor logic (TTL) for LCD interface circuitry.

Overall, Jepsen claims that the total power consumption of a laptop display using her approach is about 7% of the power of a similar CCFL-based laptop display.

Interestingly, we can compare this to Hewlett Packard’s HP Elite Book 6930p (www.bostonpocketpc.com Oct 21st 2008). That notebook ran for 24 hours on a single battery, with the largest saving of 4 hours said to come from use of its HP Illumi-Lite LED display. Most gurus reckon conventional backlights take anywhere from 25 to 50% of the total power, depending on the system and its configuration, but CPUs take the greatest chunk. Regardless of how savings are achieved, the goal is to increase battery life while using the notebook.

For Pixel Qi, combining low cost and its greater power saving features might be attractive to students using e-text books, although color would be lacking in the reflective mode. This might prove to be something of a challenge for aspiring newer e-paper technologies using electrophoretic particles in liquid, that generally struggle with sufficiently fast video and color performance, but offer many days of operation on a single charge and high reflectance.