Pixel Qi is a display company that was started about a year ago by Mary Lou Jepson, the former chief technology officer of the One Laptop Per Child project. The company is focused on adapting liquid crystal display technologies into new configurations and applications. The first product is a ten inch dual-mode display that operates in a full color mode with backlight, or in a passive monochrome mode with full readability in sunlight. Some recent press has framed Pixel Qi’s display technology as a possible threat to Amazon’s Kindle business, but the technology is presumably just as available to Amazon as to any other manufacturer or vendor.
Pixel Qi has recently been working around the clock to produce full-functioning prototypes of this new style of multi-mode liquid crystal display in time for demonstrations this week at Society for Information Display conference in Austin and the Computex trade show now opening in Taipei. First photographs of prototype displays appeared late last week.
At this time, we have little information about the full-color mode of the Pixel Qi display, but color performance will be a key issue for many potential applications. Of particular interest will be parameters like spurious reflectivity, color saturation, and backlight power requirements for color operation.
This post will instead focus on the display’s monochrome reflective mode that Pixel Qi is promoting for use in e-readers. We will examine photographs that have been posted on Ms. Jepson’s blog and on Time.com’s NerdWorld blog. These photos are of the Pixel Qi display prototypes operating in monochrome mode without backlight.
The first is a high resolution photo posted on Ms. Jepson’s blog that shows the Pixel Qi display side-by-side with an Amazon Kindle 1. At a first glance, the photo seems to illustrate higher contrast and substantially clearer text on the Pixel Qi display than on the Kindle. However, some major footnotes are less apparent:
- The camera’s line-of-sight is not perpendicular to the Pixel Qi display (in a vertical plane) even though the display is hinged and could be easily adjusted to perpendicular. In fact, the display’s front surface is set to specularly reflect ambient light from above the camera, which for all we know could be a black screen or a non-illuminated area of the room. The tilt of the Kindle is a bit less clear.
- Judging by specular reflections from wrinkles in a plastic liner on the bottom bezel, the Pixel Qi display appears to be illuminated from the left side of the camera. This could be a bit disadvantageous for the comparative background tint of the Kindle’s display which is positioned to the camera’s right, further away from the light source.
- The camera is sharply focused on a right side section of the Pixel Qi display (which is in the center of the field-of-view) but the Kindle’s display is positioned well to the side and is not well focused.
- The Pixel Qi display has a black bezel, whereas the Kindle’s is white. This provides an optical illusion that makes it difficult to eyeball the comparative brightness of backgrounds for the two displays. In specific, this illusion makes the Kindle’s display background appear darker than the Pixel Qi’s. Actual pixel gray values, however indicate that the Kindle’s background is on average slightly brighter.
- The specific Kindle in the photo might not be generally representative of the performance of current Kindle displays. For example, in testing at Origin Instruments, two later model Kindle 2 units exhibit a noticeably whiter background than a Kindle 2 that was purchased at that product’s introduction.
Thus, this photograph does not indicate that the Pixel Qi display will exhibit superior contrast to current Kindle displays. However, the apparent performance of the Pixel Qi prototype is very impressive. It seems to exhibit excellent monochrome contrast when viewed from a roughly perpendicular perspective.
Another photo, however, is a bit more problematic for the Pixel Qi technology. This photo is provided at lower resolution, but it shows the Pixel Qi display at an oblique angle to the camera and, in the background, a Kindle 1 at an even more oblique angle. The structure of ambient illumination is not apparent, but the photo allows us to make two rough judgments:
- The Kindle’s display offers substantially higher contrast than the Pixel Qi display at oblique angles.
- Contrast for the Pixel Qi display varies strongly with angle at oblique angles, as can be seen from the obvious right-to-left variation over the display surface in the photo. Yet for the Kindle, display contrast is largely unaffected by viewing angle.
We conclude that the Pixel Qi display could be an especially interesting option for use in netbooks and notebooks, where a friction-hinged display can be adjusted and the keyboard base can be rotated for the best viewing angle in any given ambient light environment. It is not surprising that netbook displays are the first market that Pixel Qi is addressing.
However, the display’s monochrome mode could be a bit less attractive in handheld applications like media tablets and e-readers, because these devices are sometimes used at a wide variety of viewing angles. A very typical use case for e-readers involves an oblique viewing angle, with the display lying flat on a table or desk for reading during a meal or while in use as a reference for activities that are progressing on another screen.
For applications in e-readers, key disadvantages of the Pixel Qi display as compared to the Kindle’s current E-Ink display seem to be:
- Somewhat darker background and lower contrast at best viewing angles
- Significantly less display contrast at oblique viewing angles
- Order-of-magnitude higher power consumption, even in the lowest power monochrome mode
The Pixel Qi display’s key advantages seem to be:
- Higher pixel resolution for a given panel size
- Much faster display response that could enable greatly improved UI’s for organizing, selecting, and navigating e-books
- An integrated full color mode, albeit one that operates at reduced resolution and likely much increased power consumption
From what we know today, the Pixel Qi display appears to be a possible but not a clear win as compared to the current E-Ink displays for use in devices like the Kindle that are optimized for long-form reading.
We look forward to definitive information about power consumption for the Pixel Qi displays. However, we should note that Ms. Jepson’s enthusiasm has sometimes shaded the truth about pesky issues like power consumption, so it may be prudent to discount performance estimates from Pixel Qi until independent test results are available.
A useful 13 minute video demo of the Pixel Qi prototype is now available on YouTube: