Angles increase optical storage

Researchers from Imperial College London in England, the University of Neuchâtel in Switzerland, and Aristotle University of Thessaloniki in Greece have devised a way to fit 1,000 gigabytes of data on an optical disk the size of a DVD. One thousand gigabytes, the equivalent of 472 hours of film, is just over 200 times the storage of today's common 4.7-gigabyte DVDs.

DVDs and CDs encode information in pits on a plastic disk. The 1s and 0s of binary information are stored as pits of different lengths, which are read by scanning a laser across the disk surface and noting changes in how the beam is reflected.

Key to the researchers' method is a way to record multiple bits of information in a single pit rather than one. The pits are longer than they are wide, which makes them asymmetrical in terms of rotation. Information is encoded in the angle of a pit, and the method can distinguish among 332 different angles.

The researchers use linearly polarized light and analyze the polarization of the reflected light and the way the surface scatters the light. The system stores ten times the information per number of pits as existing optical storage techniques, according to the researchers.

The multiplexed optical data storage disks would contain four layers of data that each store 250 gigabytes. The storage method could be ready for practical application within ten years, according to the researchers.

The researchers presented the work at the Asia-Pacific Data Storage Conference 2004 in Taiwan on September 26, 2004.