A DVD can store 4.7GB of data on a single data-recording layer. Next generation DVDs like Blu-Ray will have more capacity on two data layers. I tell you this so that you will be suitably impressed when I tell you that Ricoh has developed technology that will allow them to store 200GB of data on 8 data layers of a single optical disc. That is enough room to store 18 hours of HD TV programming.
Up until now it was impossible to use more than two layers because light reflecting between layers would cause interference. Ricoh employs a special glass plate technology that filters out the problem rays to overcome this problem. The technology was developed at Tohoku University.
The new technology may hit the market as soon as 2008. Luckily for us, it uses basically the same optical head as next-generation DVDs use, so we should hopefully only have to replace our systems one more time in the next few years, not twice.