Hitachi announced the development of an optical system that is able to amplify the read-back signal of a optical disc by ten times, allowing the efficient recording/reproduction of multi-layered Blu-Ray discs.
The recording density of an optical disc depends on the size of the optical spot of the laser used for recording. The more narrow the laser spot, the highest density is achieved. Narrowing the laser spot can be done by lowering the wave length of the laser. This was the principle idea behind the Blue laser applications applied in today?s Blu-Ray and HD DVD systems. However, the increasing demand for higher storage capacities required storing information in more than one layer per disc. But multi-layer discs are harder to read since the information is stored on stacked recording layers, limiting the amplitude of the reflective/penetrable signal required for reading/recording. As a result, the laser light that reaches the photodetector of a reader for example, is very weak to allow for accurate retrieving of the stored data.
To solve this issue, Hitachi's Central Research Institute developed a system based on the homodyne detection method. The technology allows for recovering and amplifying the weak optical signal that includes the data information in the reading process of a multi-layer optical disc. Hitachi said that the technology amplifies the reading signal by 10 times. As a result, up to 4~8 layers can be read/recorded, which means that a disc with a capacity of 100~200 GB can become a reality when using a purple/blue wavelength.
Hitachi said that it will be able to commercialize the new optical technology in 2009. For now, attendees of the Optical Data Storage Meeting in Oregon U.S. (May 21st) will have the chance to experience the technology and learn more details from the Hitachi's representatives.