Patent Pending, natch

Heard of e-paper? If you've been reading this blog for any length of time, I've babbled about it before.

E-Paper is 'Electronic Paper' - where teeny little cells in the 'paper' are switched on or off, light or dark - what appear to be letters and words are actually millions of teeny dots.

The exciting thing about e-paper is that it uses very little power - the Sony PRS500 can perform 7,500 page turns on one battery charge (this is because it only takes power to change the page, not display the page - remember that, it's important).

Now I have an idea for an application of e-paper... It may not be do-able yet, since we've likely not achieved the ability for the required resolution... The Sony e-reader only has a resolution of 170 pixels per inch, I don't know if that's pushing the boundaries of e-paper or not.

How about an e-paper rewritable CD? Instead of burning the data, you actually 'write' the data as minute e-paper dots on the EtchCo E-Paper CD.

This is how a common CD works: (Thank you, Wikipedia!)

Common printing methods for compact discs are screen-printing and offset printing. CD data is stored as a series of tiny indentations (pits), encoded in a tightly packed spiral track moulded into the top of the polycarbonate layer. The areas between pits are known as 'lands'.

Each pit is approximately 100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 μm in length. The spacing between the tracks, the pitch, is 1.6 μm. A CD is read by focusing a 780 nm wavelength semiconductor laser through the bottom of the polycarbonate layer. The difference in height between pits and lands leads to a phase difference between the light reflected from a pit and that from its surrounding land.

By measuring the intensity with a photodiode, it is possible to read the data from the disc. The pits and lands themselves do not directly represent the zeros and ones of binary data. Instead, Non-return-to-zero, inverted encoding is used: a change from pit to land or land to pit indicates a one, while no change indicates a zero. This in turn is decoded by reversing the Eight-to-Fourteen Modulation used in mastering the disc, and then reversing the Cross-Interleaved Reed-Solomon Coding, finally revealing the raw data stored on the disc.

The EtchCo E-Paper CD Writer unit (Bluetooth version available soon) would house the power source and all processing components - once 'written', the CD no longer needs power to maintain the image, so this would allow you to re-write the same CD hundreds of thousands of times.

You could store all of your CDs in the EtchCo E-Paper Writer/CD Changer, and never touch the originals. Just tell the Changer which CD you want, and an E-Paper CD copy will pop out, protecting your originals. You'd only need a handful of e-paper CDs, since they are so re-usable.

E-Paper CDs would work in any CD player, since they would use the same format as all existing CDs... You could write any kind of data you wanted, from MP3s to documents.

You could also re-label the top of the CD each time, since you're not writing on it with a Sharpie, or burning/printing a label - yow!