TeleRead: Bring the E-Books Home

News & views on e-books, libraries, publishing and related topics
January 5th, 2008

Why I favor Mary Lou’s OLPC screen tech over E Ink—at least for MY purposes

By David Rothman

maryloujepsen2Given a choice between E Ink and One Laptop Per Child’s screen technology, which might you choose? Well, in case anyone else is curious, I favor the latter because:

1. The OLPC tech is cheaper, at least for now. The  display developed by Mary Lou Jepsen (photo) costs just $35 a screen to make.

2. Yes, her special LCD can glow in the dark, not just be usable in the sun.

3. It’s color, which kids love. I’m still a kid in that way, among others. Judging from the photo, betcha Mary Lou is, too. Makes for more imaginative engineering.

4. The mix of the glow and the reflective stuff can be pretty easy on the eye.

5. Mary Lou’s screen is better for interactive e-books right now. No delay when you’re entering text. Video potential for the same reason. Of course, E Ink in the future will be much more fleet.

The negative of the OLPC screen tech, compared to E Ink, is that it probably eats up more battery power—-which means the gizmos may have to be larger. But in the reflective mode, it’s still far, far ahead of backlit LCDs in the power consumption department.

No single “best” display

Yes, those impressions are from my perspective.

If E Ink is easier on batteries than the OLPC system, even when the latter uses the black and white reflective mode—I’ll welcome facts and opinions from readers, since this isn’t a simple issue!—then many people may prefer E Ink. What if they spend most of their time away from AC outlets. I don’t. Nor am I bothered as much by the several pounds of the OLPC laptop, far heavier than, say, the Sony Reader. Since the OLPC machine is a real computer, not just an e-book reader, I got a lot back for the weight.

Please note that neither screen technology is going away, and I suspect that some companies may offer both, especially now that Mary Lou Jepsen seems eager to commercialize the display technology of her past employer. A Good Thing, by the way. I believe in profit-nonprofit synergy as long as things are on the up and up, which they appear to be in this case, with Mary Lou’s new company paying licensing fees.

A little more background on OLPC tech

More on Mary Lou Jepsen appears in an IEEE publication, with tidbits, too, about her display:

“According to Jepsen, the display her team eventually marshaled into existence requires, depending on the mode, only between 2 percent and 14 percent of a typical laptop display’s power consumption.

The power needed is low enough to be provided easily by a pull cord or other manual means, charging a nickel-metal-hydride battery pack; 1 minute of charging suffices for 10 minutes of use. To save watts, the display can switch between color with the backlight on, in low light, and black-and-white with the backlight off, in sunlight. OLPC’s engineers trimmed battery usage further by, among other things, adding memory to the ­timing-­controller chip, which decides how often a display refreshes. That trick enables the display to update itself continually without using the CPU if nothing changes on the screen.”

And speaking of gizmos: Put buyers first? What a concept, from the New York Times via Mike Cane.

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7 Responses to “Why I favor Mary Lou’s OLPC screen tech over E Ink—at least for MY purposes”

  1. Details of the OLPC display are here:

    http://wiki.laptop.org/go/Display

    Interesting stuff, IMHO.

  2. Oops. Meant to add this link about the display controller:

    http://wiki.laptop.org/go/DCON

  3. Thanks, Cerebus. What I found especially interesting is the reminder that the effective res even in color is higher than widely circulated stats would have you believe. Exactly. I’m happy with res in both monochrome and color even if the former is better. David

  4. David, I look forward to a post from you after a long day’s binge reading. I have more trouble with the back-lighted LCD displays than those without the backlight. I suspect that it’s a question of flickering CFL lights strobing with flickering CCFL backlights at a frequency too high for me to recognize consciously but somehow bothersome and eye-strainy. (”eye-strainy”?)

    Congrats on your new device.

  5. [...] Finally Change The World? David Rothman over at the esteemed Teleread blog has finally given his opinion of the unique screen being used by the One Laptop Per Child XO [...]

  6. Well, this is interesting. OLPC wonders if a Toshiba notebook I covered uses the same screen tech!

    OLPC:
    http://www.olpcnews.com/hardware/screen/toshiba_portege_r500_display.html

    My old blog (you must scroll waaaaay down in the pics to see the Toshi):
    http://mikecane.wordpress.com/2007/09/28/photo-album-digitallife-expo-2007/

  7. No. The Toshiba is a straight transflective screen. You can tell by noting the slight color apparent in the Toshiba screen when the backlight is off. Because the reflective layer is *below* the color filters, the reflected screen remains in color mode.

    The difference is in construction. Transflective screens have the reflective layer above the backlight but behind the color filter layer. The OLPC dual-mode screen moves the reflective layer above the color filter layer, just behind the LCD layer, so reflected light is monochrome. In addition, each pixel of the OLPC screen is single color, vs. three sub-pixels of three colors.

    These may seem like minor differences but the result is that the OLPC screen can leverage higher native resolution when viewed under reflected light. This, when combined with the lower resolution color coming through the backlight, gives the visual impression of higher resolution. The OLPC screen is 1200×900 monochrome (reflected light only, backlight off), but instead of being ~700×500 as you would expect with normal pixel grouping it appears as 800×600 (backlight only, no reflected light) or higher (with backlight *and* reflected light).

    Yeah, it doesn’t make sense, but when you *see* it in operation all becomes clear. :)

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