The capacity of optical storage discs – CD, DVD or Blu-Ray and HD-DVD – could be increased eightfold with a new trick developed by engineers working for Thomson in Germany. Optical discs are covered with millions of identical microscopic pits, but on the new discs those pits will be differently shaped.
The laser beam used to record each pit on the disc surface is split down the middle, with one side of the beam brighter than the other. This means the beam makes an asymmetrical mark on the disc's surface.
A liquid crystal in the path of the laser beam twists the beam through eight different positions. So the asymmetrical marks on the disc can be rotated through eight steps, potentially leading to a corresponding increase in data capacity.
