This profile offers an introduction to what's been variously promoted as 'digital paper', 'electronic paper' and 'electronic ink'. 

     background

Since the 1970s there have been major investments in research regarding new ways of displaying digital information and capturing information using a pen rather than a keyboard. While stylus-based personal digital assistants (PDAs) are gaining significant market acceptance - some studies suggest that 6% of the US online adult population has such a device - work on 'electronic paper' has had little success.

Researchers have aspired to creation of a medium that has the essential characteristics of a sheet of paper - thin, light, flexible, shock-resistant, able to provide a high-resolution display of text and graphics, able to accept handwritten text, use little power and be highly durable. Have we forgotten anything else? Oh yes, have low production costs so that it could be priced as a 'thow-away' item. So far the aspiration has been unfulfilled: most products meet several requirements of that wish list but not all.

     Gyricon and SmartPaper

The prototype 'electronic paper' was developed at Xerox's Palo Alto Research Center (PARC), home of the computer mouse and laptop, in 1975. What's now marketed as SmartPaper was initially labelled 'Gyricon' (after the Greek for "rotating image"). It is currently handled by Xerox's Gyricon Media (GM) subsidiary.

Although the expectation was that it would replace many publications, with commuters for example uploading the daily newspaper onto a sheet of Gyricon for perusal en route to work, it's largely been restricted to corporate signage (particularly for upmarket US retailers).

The technology involves a flexible transparent membrane embedded with microscopic spheres, each with a light-coloured hemisphere and a dark-coloured hemisphere. Small electrical charges result in the spheres rotating to display their light or dark side up, thereby generating a high-contrast image. The technology is 'display only' - the 'screen' does not accept input by pen or paw - and might more aptly be described as electronic cardboard. It's mono-chromal.

     Electronic Ink

An independently-developed product using membranes containing black and white particles within liquid-filled capsules was developed in the late 1990s by E Ink, building on research at MIT. John Jacobson's 1997 paper offers an explanation of the technology.

As with SmartPaper, patterns are created by applying a small charge to the membrane. Like SmartPaper E Ink's Electronic Ink has primarily been used for in-store displays.

E Ink has trademarked the term 'RadioPaper' and is apparently concentrating on research into low-power lightweight monochrome displays for personal assistants and laptops. Its site notes that an electronic ink display can have a much higher resolution than current LCD screens, uses 1/1000th of the power necessary for an LCD display and can preserve its content without power. A consumer for example could switch off the power on an electronic book or laptop while reading a page of text. Electronic Ink is read-only and mono-chromal.

     DataGlyphs and DigiPaper

Xerox developed but has not had much success with DataGlyphs, sometimes promoted as "digital paper." The technology essentially provides a watermark or steganographic identifier on wood-pulp paper. That identifier can be recognised by a scanning device. Under optimal conditions a one-inch square DataGlyph could encode up to 1000 bytes of data. Promoters have claimed that it could be used in a document management system, as the basis of a security scheme (eg the image would be discernable to the scanner but not to the unaided eye if the document was photocopied) or as a barcode-style label in some form of production system.

While humans can write on DataGlyphs paper, that ink/pencil information rests on top of the 'glyph' and is independent of it.a form of encoded data designed to be printed on ordinary paper for later scanning and decoding by a computer.

Xerox PARC also developed DigiPaper, an image-based document representation that uses token-based image processing to obtain very high compression for bitonal images.

     Anoto

For data capture the main contender is Anoto, developed in Sweden. It relies on specially-treated paper and the Anoto pen, a digital device that's tied to a wireless network. Each pen would have a separate IP address; each sheet of Anoto paper - whether sold as a label, a note pad or in some other format - will be unique. Putting pen to paper results in a unique map, that's then (in theory) transferred to and can be retrieved from a digital memory using the wireless network.

Sound excessively complicated? Perhaps. The idea grabbed the attention of geek-lifestyle magazine Wired in early 2001 and has attracted favourable attention from competitors such as the MIT Technology Review. In essence, Anoto is a 2001 wireless update of the graphics slates that appeared (and disappeared) in the late 1980s. It allows data capture - albeit second-hand - but otherwise is traditional paper: the display uses ink on pulp rather than digits on a screen.

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