The biggest technology roadblock to building the $100 laptop championed by Nicholas Negroponte, founder and chairman of the One Laptop per Child organization, is close to resolution.
That roadblock has been developing a display that is rugged, inexpensive and readable in a wide variety of conditions from low light to bright sunlight. Displays are a traditional barrier to building laptops for use in a variety of conditions. In the past, they tended to use a lot of power and were difficult to read in lowlight and nearly impossible to read in direct sunlight. If you want a really heart-stopping financial moment, call your laptop vendor to find out what it would cost to replace a broken display. Youll most likely find that the display replacement costs more than a new laptop.
Now, the chief technology officer of the One Laptop Per Child program claims to have come up with a display that can be readily mass-produced in standard LCD factories, has a higher resolution than 95 percent of the laptop displays on the market today, runs with about one-seventh of traditional power consumption, costs one-third of the price and can be read in sunlight or room light without backlighting.
In the world of displays, such performance and capabilities would be as big a change as when computer makers figured out you could build computers with flat screens, ushering in the laptop era. Laptop vendors desperately trying to figure out how to run cooler systems to avoid battery requirements that push (and sometimes exceed) engineering thermal capabilities would embrace a display technology that doesnt create a poor trade-off between power consumption and readability.
How did the One Laptop Per Child accomplish a revolution in display technology? The first step was to hire one of the best laptop technologists. Mary Lou Jepsen is the founding CTO of the OLPC organization. Previously she co-founded in 1995 the first company with a singular mission to develop microdisplays. She was also CTO of Intels Display Division. Her résumé reads like a history of display development. And this September she is due to become a professor at the MIT Media Lab, where she will lead an effort in nomadic displays.
So much for her bona fides. I caught up with Jepsen as she was finishing up some work on the OLPC display in Taiwan, just as she was about to head back to the United States for a keynote presentation and also to find time to get married. The following e-mail question-and-answer session and accompanying slide show are the first detailed descriptions of the display that will form the basis of the OLPC project.
What is the fundamental display technology? You mentioned the display would be capable of being able to be fabbed in LCD factories—is it a variation of LCD?
Yes, its a variation on liquid crystal display. Its a rethinking of it. Ive spent 20 years in the display industry and despite making fantastic laboratory demos of holographic video, projection systems, head-mounted displays, microdisplays, city-block size holograms, and even moon-tv, ultimately none of them have achieved mass production in the way CRT did, and LCD has. Many got into production, but the manufacturing infrastructure of LCD is larger than both DRAM and silicon foundries—worldwide—today.
Usually more than 20 years pass from the first demo of a new display technology until mass production can be achieved. As I embarked on finding a display solution in record time, I knew that I had to use an existing manufacturing infrastructure with no process changes whatsoever to have a hope. There was only one choice. Even five years ago there was a question of which technology would “win” for HDTV, even two years ago—but look at the accompanying chart. Which technology would you choose if you were in charge of shipping 5-10M laptops next year and 50-100M laptops the year after?
Is the display the final piece of the technology puzzle?
We had the basic technology for everything else in the laptop, but we needed a high-resolution, low-cost, low-power display. I added the sunlight readability as I spent more time working with the developing world and because I realized that we could get that [sunlight readability] for free.
How do you achieve the higher resolution without higher power consumption? One-seventh the power consumption and one-third the price is quite a claim. Can you elaborate?
What I have done is re-examined the LCD for our laptop. I looked at the cost structure of LCD, and the needs of our users, the kids of the world, half of whom have little or no access to electricity. Many of whom spend much of their time outside. What I came up with: a dual-mode display. Mode 1 is 800×600 (or higher—even 1024×768 looks surprisingly good!) color backlit with 1W MAX power consumption. Mode 2 is high resolution 1200×900 black and white reflective sunlight readable with 0.2W MAX power consumption. Mode 2 is also room light readable with the backlight off at again 0.2W power consumption. There are several keys to making this display work—they all add up to a large impact.
Can you provide more technical details?
One. I changed the pixel layout to diagonal stripes of color—this allowed me to increase and decrease the resolution of the panel horizontally and vertically (not just horizontally, which is what a standard layout would do).
Two. I eliminated part (or all) of the costly color filters with innovative backlight solutions. Truthfully I have a variety of solutions under development right now—the first version of this family of solutions just started working last week. This allows a lot more light throughput and thus much lower power consumption.
Three. I decided to not constrain the pixels to be always a certain color. Any pixel can either be a pre-assigned color or “black and white.” This turns out to be more powerful than it seems. The sharpness (or resolution) of the display can be much higher this way.
Four. I eliminated much of the costly interface electronics. This allowed us to use a lower cost novel-TTL interface instead of the now typical LVDS (Low Voltage Differential Signaling). LVDS [is] expensive and power hungry and required for most LCDs for laptop resolution, but because for my display, each pixel can be color or monochrome we can achieve higher resolution than 95% of the laptops on the market today.
Five. Cutting the cost of the optical films in the LCD through innovative liquid crystal “mode” design while increasing again the efficacy of light through them.
Six. Moving to use LEDs in the backlight rather than traditional CCFLs (very small fluorescent lights). This is also better for the environment.