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Colour, e-ink’s final frontier

V. Sridhar and
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The problem of electronically rendering in colour is on the verge of being cracked

The printed book, which has not faced a serious contender since the 15th century, now faces serious competition from e-readers.

The recent announcement at the Consumer Electronics Show (CES) 2013 that e-ink technology is on the verge of cracking the problem of electronically rendering in colour offers some hope that the upstart is at the final frontier of its assault on the printed word.

Despite the spectacular rise of the tablet, the e-reader still offers some compelling advantages.

Fundamentally, this has to do with what reading is all about. You read, not watch, as you would a movie, for instance. The LCD screen, which is what goes into most display devices, is more suited to displaying graphics, which e-readers have been unable to thus far; this is why the recent announcement at CES 2013 is so exciting.

Longer battery life

The fact that when you read, you linger on a page till you have actually read it, means that the device, unlike a tablet, is much less energy demanding, – implying much longer battery life.

E-ink displays, which do not use any backlight, but only ambient light make reading on a screen a soothing experience. Moreover, unlike tablets, which require to be charged every day, e-book readers such as Amazon’s Kindle and Barnes&Noble’s Nook are usually good enough for two weeks on a single charge.

The prolonged battery life and the paper-like reading experience of the e-reader are consequences of a recent technology that has been quickly adapted — electrophoretic ink, better known as e-ink, which is based on research at the Massachusetts Institute of Technology Media Labs in 1996. Companies such as E-ink Holdings Inc., and Xerox realised the revolutionary potential of e-ink displays on the publishing industry and have made considerable progress in the last few years.

The e-ink magic

The patterns created by e-ink on the surface of an e-book reader can be compared to the designs made of Lego blocks. A lot of effort is required to create the design with Lego blocks, but little effort is needed to sustain the same design.

Likewise, in e-ink displays, the display has a field with minute alterable cavities, microcapsules, which are analogous to the Lego blocks, and also form the smallest entity (pixels) on the display field.

When an electric charge is applied, the corresponding microcapsule, either turns black or white, depending on whether it is positively or negatively charged. After an image is rendered or a layout of text is rendered on the screen, there is no need for continued power supply. This is unlike in LCD displays, where even if the same picture is being stared at for hours, the display drinks the same amount of power as it needs for loading a fresh picture.

To change content on e-ink displays, the display field is flushed out, in a sense, and screen refresh happens.

The screen refresh in e-ink displays is a slow process, compared to the electronic circuit speeds, which appears like a blink to go blank for the new page to be loaded.

These transitions take a noticeable amount of time, and this is one aspect which e-ink technologists are focussing on; to make e-ink have smoother and faster transitions.

Colourless e-ink displays

E-ink displays have seen widespread deployment in e-book readers, and most of the commercially available e-ink displays can render only gray scale content.

This has already been a major factor of criticism that e-ink displays cannot display colour images, as one might miss this feature when reading a magazine or a textbook with graphic content.

At CES 2103, E-ink Corporation showcased one of the first products with an e-ink colour display.

Although it still retains the power advantage, the colour saturation and responsiveness levels are yet to match those available on LCD screens. The available E-ink colour display called the Triton supports a maximum of 4,096 different colours, compared to LCD displays, which render up to 16 million colour variations.

The E-ink colour displays are not technically very different from the grey scale displays. The alternate charging of microcapsules still forms the basic technique to render text or images. On top of the grey scale display, grid of red, green, blue colour filters and one clear filter is placed to render colours. That is to say, each e-ink pixel comprises of 4 subpixels. This filtered approach to render colour is like looking through tinted sunglasses. Obviously, the rich colours of a National Geographic magazine would be unavailable on such a device.

E-ink for the future

For smartphones that are in dire need of a display technology that will consume less power, e-ink with critical improvements such as response time and true colour support may be the solution. But e-ink displays will not see mainstream smartphone or tablet implementations for a few more years, unless these improvements have been accomplished.

Publishing in future could be e-ink printed on e-paper, with dynamic content that can be reloaded or refreshed on a flexible surface, much like a newspaper.

As the debate rages on, about whether the e-book can replace books as we have known them for over 600 years, clearly the upstart still has a few aces up its sleeve.

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