Pioneer Develops 400GB Optical Disk Technology

Pioneer Corporation has developed a 400GB optical disk with 16 25GB layers, the same layer capacity as a Blu-ray disk. It expects to develop a recordable 16-layer disk. The drive has to focus its laser very precisely indeed to read signals from each separate layer. A technical problem has been in obtaining readable information from the layers, separating this from 'cross talk' data from the other layers in between the target layer and the drive surface, effectively noise, and also transmission loss as the signals have to pass through multiple layers on the drive. Pioneer used DVD-type technology to overcome these issues.

It achieved stability in recorded signal playback by using a wide-range spherical aberration compensator and light-receiving element that can read out weak signals at a high signal-to-noise ratio in the optical pick-up mechanism. Since the optical specifications of the objective lens, such as NA (Numerical Aperture), are the same as those for the existing Blu-ray (BD) discs, it is possible to maintain compatibility between the new 16-layer optical disc and BD discs. (The higher numerical aperture of the objective lens, the smaller diameter of the beam spot focused on a disc surface.)

This amount of data is a third greater than that of the delayed 300GB InPhase holographic disk. Productisation of the 12cm diamter disk could be two or three years away, if the decision is taken to go ahead, and we might see a combined drive supporting the Blu-ray format as well.

By Paul Roberts, Blocks & Files