Toshiba has developed a rewritable optical disc with a capacity of 30GB per layer, per side and a companion read/write optical head that incorporates a blue laser, the company announced today.

The new optical disc has a capacity more than six times that of a standard DVD (digital versatile disc) but is the same size. DVDs have a single-sided capacity of 4.7GB. The new disc can store three hours worth of high-definition digital video, Toshiba said in a statement.

Blue lasers have a wavelength of 405 nanometres, shorter than that of red lasers, which have a wavelength of around 650 nanometres and are used for reading and writing DVD and CD discs.

The shorter wavelength means the laser can register smaller dots on a disc and thus more data can be stored. As a result, blue laser technology has been adopted for the development of next-generation optical discs.

Panasonic also recently announced a system for high-density storage on optical media using blue laser technology.

Other Japanese companies have had similar breakthroughs using blue laser technology at the R&D level. Sony jointly developed a 22.5GB optical disc with Pioneer in 2000.

The capacity of Toshiba's new disc can be doubled with the use of a second layer. However, the company hopes to initially keep it as a single layered disc so that it can be commercialised sooner, said Midori Suzuki, a spokeswoman for Toshiba.

"First of all, we will try to standardise this new development by presenting it at the DVD Forum," she said. Then the company plans to commercialise the product when high-definition digital TV broadcasting starts in Japan, which is expected next year, Suzuki said.

At the same time, the company will also target the format for use in personal computers. Other companies are focusing more on using the discs in audiovisual devices, Suzuki said.