Pixel Qi - What is It?
Who is Pixel Qi
First the Qi is pronounced "chee."
Ms. Mary Lou Jepsen
The company, Pixel Qi, was founded by Mary Lou Jepsen in 2008 as an LCD display manufacturer. They are based in San Bruno, California. Ms. Jepsen was Chief Technology Officer of the One Laptop per Child (ONPC) project. Prior to working for OLPC she worked as CEO for Microdisplay Corp., a company she started in 1995 that built liquid crystal on silicon chips. These displays were purpose designed for high-definition TVs. She later worked for Intel as Chief Technology Officer (CTO) of it's display division.
Ms Jepsen has earned both a degree in electrical engineering and a Ph.D. in optics at Brown University. She also received a Master of Science in Holography from the MIT Media Lab. One might say her career is centered on display technology.
The company currently manufacturers a unique liquid crystal display (LCD) that can be manufactured on existing LCD equipment, but is capable of displaying a bright back-lit image in poor lighting conditions or a crisp ink on paper image in sunlight. Because the display has a matt finish glare is reduced. For the actual Nit* figures see the specifications below.
In the backlit mode the display draws the amount of power typically associated with back-lighting LCD display. In the reflective mode the display sips power at a miserly rate. This is where Pixel Qi hopes to shine.
In both modes the screen display is sharp and clear with high resolution and lower than normal power consumption. Because it uses both back-lighting and ambient light power consumption can be drastically reduced depending on external lighting.
Currently Pixel Qi is making only one size of display. This is called the 3Qi. The form-factor of this display screen is ten point one (10.1") inches diagonal. This is a very standard size for laptop netbook display screens and the 3Qi is currently being marketed as a ready replacement in a wide variety of laptops (see bullet points below).
Pixel Qi has done this with purpose because at this point in time the company is selling just the displays as a replacement for existing screens in a wide array of computers. The are also working on a seven (7") inch replacement screen which is also a common form factor for a variety of tablet computers.
To date the Pixel 3Qi (10.1") screen fits and functions completely and is verified by Pixel Qi in the:
- Lenovo S10-2 (5.5 hours Battery Time)
- Samsung N130 (4.5 hours Battery Time)
- Samsung N220 Plus (13 hours Battery Time, US: N220-11B)
The Pixel 3Qi (10.1") has been reported to work completely in the following; however, Pixel Qi has not confirmed function in these machines:
- HP 2132-2133-2140 (5 hours with 6 cell)
- Samsung N135 (6 hours Battery Time)
- Samsung NB30 (10 hours with 6 cell)
The Pixel 3Qi screen of choice for the Notion Ink Adam tablet computer.
The first laptop to acquire the new display was an Acer. By switching viewing modes during use Pixel Qi was able to extend battery life by two hours.
The Pixel 3Qi 10.1" screen has a transmissive resolution of 1024 x 600 RGB color. It can also display a reflexive image at 3072 x 600 dpi. Nit brightness in a darkened room is 165 and in a well lighted room 235 nits. In bright sunlight the nit index is well over one thousand (>1,000).
For comparison most computer LCD screens operate in the 200 ~ 250 nit range.
Color saturation is 40% of NTSC. Total power consumption is 2Watts with 0.41Watts at 30Hertz for reflective display and 0.54Watts at 60Hertz for transmissive display. The screen dimensions are 9.25 x 5.62 x 0.2" [235mm x 143mm x 5.2mm]. The interface circuitry, between computer display processor and screen is Low Voltage Differential Signal (LVDS) which is known as a very high-speed yet simple twisted pair interface.
Pixel Qi 3Qi
Transflective & backlighted LCD
Display Resolution LCD
1024 x 600
Display Resolution Trasflective
3072 x 600
0.54 Watthour (30Htz)
0.41 Watthour (30Hz)
Low Voltage Differential Signal
LCD no Backlighting (dark room)
LCD outdoor lighting
Ms. Jepsen went to the IEEE Specturm New York offices to show off the display and demoed the movie Slumdog Millionaire to staff there. Midway into the movie she pressed a button to the left of the screen which caused the video to switch from full color to grayscale. When a kindle notebook was held up to compare the two images, the movie playing had the same crisp "ink on paper" appearance of the eReader
"You can easily cheat in a demo like this,” says Mary Lou Jepsen, the creator of the prototype screen, ”but most movies are shot in very dark conditions, which is hard to display.”
In the process of demonstrating her low power LCD displays Ms. Jepsen won her company a Winner placement in IEEE's Winner and Losers in technology category in 2010.
Because the 3Qi is a true LCD with tranflective technology, the display can show movie quality video in bright light situations, unlike the ubiquitous eInk display (think Kindle or Nook) that virtually stormed the market in eReaders of 2010.
How Qi Works
The best way to describe this is by comparing it to other transmissive display technology. Please refer to the associated graphics to the right.
Traditional LCD Color Display
In the first image the light source is behind the LCD panes. When back-lit, the light is absorbed and therefore reduced as light passes through the LCD color pixels. If lighting is ambient the light is absorbed twice, entering the LCD pixel and bouncing out back through the LCD pixel.
Pixel Qi Display
Because the color LCD pixels are behind the reflective surface light is not absorbed by these pixels, but is instead projected out. This way too the reflective surface can be devoted entirely to grayscale, while the underlying LCD pixels are dedicated to color. The two, when used simultaneously, give the viewer the appearance of higher contrast as well.
Pixel Qi approached the problem as if it were entirely new and unexplored. in the process nearly every light absorbing material in the overall display was investigated. This included the LCDs, polarizers, transistors, filters, masks, and optical retarders.
The original design specification for LCD sub-divided each pixel into a square of red, green, or blue. Within each of these color pixels divisions were made to the subpixel level, where each was tasked with either transmissive or reflective function. This, by itself, reduced the area of each pixel devoted to one of the two functions rather than tasking the entire pixel to reflect or transmit light.
Because the Pixel Qi does not use color filters there is no light loss through those filters. Each rectangular subpixels, is almost entirely devoted to reflection. This means that each subpixel is basically a mirror with a small window centered in each for the transmission of color light.
All of this combined ensures a vibrant display in virtually any ambient light situation. Finally, because there is no need to drive light through filters, power requirements are reduced.
Though this may seem highly technical to many readers the true significance of this display is that it is capable of displaying high-resolution video in both grayscale and color while using less power than other LCD displays traditionally used in laptop and tablet computers.
The power saving is significant because most mobile computing devices in the ten inch range last well under six hours.
I fully expect the Pixel Qi to make significant inroads into the display side of mobile computing.
* Nit: one candela of luminance per square meter. Common LCD screens have backlighting capable of 200 ~ 250 nits. Most High-Definition televisions 400 ~ 450 nits. A higher number is better.
The author was not compensated in any way, either monetarily, with discounts, or freebies by any of the companies mentioned.
Though the author does make a small profit for the word count of this article none of that comes directly from the manufacturers mentioned. The author also stands to make a small profit from advertising attached to this article.
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