E-paper
From MobileRead
Electronic paper, also sometimes called e-paper or electronic ink, is a display technology designed to mimic the appearance of regular ink on paper. Basically, light is reflected on the display, and no power is used to display a page.
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[edit] The Technology
There are four competing technolgies for e-paper devices:
| Technology | Description |
| EPD | Electrophoretic displays, also wrongly translated as Electronic paper displays |
| ChLCD | Cholesteric LCD displays, also known as BCD = bi-stable cholesteric displays |
| IMOD | Interferometric Modulation |
| IPE | in-plane electrophoretics can achieve color. |
EPD (used by E Ink and SiPix) is a technology that, in the case of E Ink, uses tiny liquid filled bubbles that contain both white and black "ink". Each bubble represents a pixel on the screen display. Electronic charges are applied to the bubble to bring either the white ink or the black ink to the surface. Once the charge is removed the ink will stay at the surface so it can been seen without any power applied. The bubbles are the same size as a pixel on the screen and the connection of all these bubbles can form text characters and images on the surface of the screen. A positive charge will cause white ink to appear while a negative charge will cause black to appear. A charge can be applied to affect a small portion of the bubble instead of the whole bubble. This can be used to cause a mix of white and black (gray) to appear.
SiPix also has developed EPD but in their case, white particles are suspended in black ink that is contained in small microcups. When the white particles are at the viewing surface, the display is white and when they are at the back surface, the display is black. Like E Ink, the particles can be partially switched to achieve gray scale and the display is bistable.
ChLCD (used by Nemoptics, ZBD, and Kent Displays) uses a special spiral arrangement of LCDs to produce the needed bi-stable effect. Nemoptics promotes this technology under the name "BiNem". Like EPD, ChLCD only needs power to update a page. The LCDs remain in either the "white" or "black" state even when no power is applied. This is the reason why they are called Zero-power LCD.
IMOD (Qualcomm calls it "mirasol") is a rather new technology (2008) based on MEMS (micro-electro-mechanical systems). It has a much faster response time than EPD and ChLCD but needs a very small amount of power to display the page. It's not a zero-power technology but very low-power. It is easier to produce colored e-paper with this technology.
Initial e-books were able to show 4 levels of gray (black to white) but the latest technology has been able to achieve 16 levels of gray. Additional apparent gray levels can be done using dithering to achieve more levels than what can be done with the controller. Supporting Gray scale can improve the looks of images in the eBooks and may (depending on the implementation) even be used to smooth font edges that use diagonal lines or curves (this technique is called anti-aliasing). Note that the performance (speed) of the display is better if only 2 colors are used (monochrome).
IPE - Philips technology achieves a color display. It is similar to the E-Ink EPD but relies on two particle-filled capsules for each pixel, one containing yellow and cyan, the other magenta and black. By controlling voltages, the colored particles either spread across the pixel or move out of sight altogether, making it possible to render different colors by controlling the number of colored particles shown. To create white, the particles simply shift to reveal the white substrate beneath the capsules. In-plane electrophoretics research has been maturing and a product is likely soon.
E-paper has sufficient contrast to be read quite well in direct sunlight. E-paper is not transparent so it cannot be backlit, thus it requires external lighting to be read in the dark.
E-paper displays are expected to find applications in signage, on shelving for the display of information, and on packaging for the display of pricing and instructions. These displays are also already used in portable eBook reading devices, in clocks, and in USB sticks.
Currently, there are opportunities in improved color paperlike, fully flexible, low-cost paperlike and self-edge displays, and other labeling applications.
See also: Paper Display
[edit] E-paper Technology Providers
| Provider | Location |
| E Ink | Cambridge, MA |
| Fujitsu Frontech Limited | Tokyo, Japan |
| Hitachi | Tokyo, Japan |
| Kent Displays | Kent, OH |
| Eastman Kodak | Rochester, NY |
| Nemoptic | Magny les Hameaux, France |
| Ntera | West Conshohocken, PA |
| PVI | PVI, Taiwan ROC |
| SiPix | Fremont, CA |
| Xerox | Stamford, CT |
| ZBD | Windsor, UK |
| Bridgestone | Tokyo, JP |
[edit] Limitations
- Current displays are only in greyscale, not color.
- The refresh rate of the screen is very low compared to standard LCD screens : about 1 to 2 seconds, compared to about 30 ms for LCD. Mixing pure text content with Flash or video content is not currently possible. Web browsing using scrolling is not really suitable on E-ink displays
- The refresh of an eInk page creates a black flash and can create temporary "ghosting" effect which can be annoying to some people.
- There is no way to backlight the display as the technology is opaque.
The following data is included from the article E Ink display.
[edit] E Ink Display Specifications
Updated for E Ink Vizplex imaging film.
[edit] Optical
| White State Reflectivity: | 40% (typical) |
| Contrast Ratio: | 7:1 (typical) |
| Viewing Angle: | 180 degree |
| Grayscale Capability: | 4-bit (16 gray levels) |
| Image Update Time: | 740 ms (grayscale mode) 260 ms (1-bit mode) |
In actual practice the grayscale capability is up to the controller hardware and can range from 4 levels to 16 levels in currently shipped devices.
[edit] Mechanical / Dimensional for 6" Display
| Pixel Count: | 800 x 600 (SVGA) 167 ppi |
| Pixel Size: | rectangular, 151 x 153 micron |
| Active Area: | 122.4 x 90.6 mm (4.8" x 3.6") 152.3 mm (6 inches) diagonal |
| Display Thickness: | 1.25 mm |
| Display Weight: | 35 g |
There are other display sizes available.
- 10.2" (207 x 155 mm, 8.15" x 6.1") 1280 x 1024 pixels, 158 ppi
- 9.7" (202.9 x 139.5 mm, 8.0" x 5.5") 1200 x 825 pixels, 150 ppi
- 8.0" (162.6 x 121.9 mm, 6.4" x 4.8") 1024 x 768, 160 ppi
- 5.0" (101.5 x 76.1 mm, 4.0" x 3.0") 800 x 600, 200 ppi
For more details see: http://www.eink.com/products/matrix/High_Res.html
[edit] Environmental
| Operating Temperature Range: | 0 — 50 C |
| Storage Temperature Range: | -27 — 70 C |
[edit] Electrical
| Supply Voltage: | 2.7—3.3 V DC |
| Power Consumption: | Active update peak: 1800 mW Active update typical: 750 mW Standby typical: 1 mW |
[edit] E Ink controllers
The current controllers
- Apollo is the original controller and is still popular and used on many readers.
- IRex builds their own custom controller offering 16 levels of Grayscale.
- Metronome controller currently used on the PRS505
- Epson controller available in late 2008 with improved features. Used on Sony PRS700, Amazon Kindle 2, Kindle DX, Hanlin V5, and others.
- Marvell builds a custom controller for their line of ARM processors.
Here is a discussion of interfacing to these controllers for Linux applications.
[edit] Notes on earlier E Ink devices.
The older display technology has 4 level gray scale and slower update times of 1000 ms for gray scale and 500 ms for 1-bit mode. These were primarily 6" devices. They also had less reflectivity. This causes these devices to appear less white (light grey background) and have less contrast.
The iRex iLiad, on the other hand, uses a custom display controller that achieves 16 levels of gray scale. They are also using an 8.1" display featuring a 1024 x 768 pixel display.
See also E-paper and E Ink
