Powerful optical disc

1994/11/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Irudiak/Soinuak
• Multimedia

A single disc of twelve centimeters in diameter allows storing the information of the twelve-hour film or the text of two million pages thanks to a procedure that IBM has just devised. The new invention is a multilayer optical disc prepared in laboratories in the California city of San José. It currently has a capacity ten times higher than the discs used for music, video, interactive compact discs, etc. But that's just the beginning. In fact, US researchers claim that duplication or triple of this large accumulation capacity will be available shortly.

The essence of the new invention is very simple. In the usual compact disks the information is recorded on the face of the disc, but in the new disc ten overlapping layers have been prepared to accumulate information. In the previous system, the laser beam affects a point by focusing the surface of the disk through the lentilla and measures the intensity of the ray reflected by a photodiode to know the value of the data inscribed on the disk. However, in the new multilayer disc there is a special mechanism to focus laser rays on different layers.

In order to accumulate as much information as possible in smaller and smaller sizes, the system used so far has been data compression. In the case of sound, for example, the pathway has been to record only the frequencies that the human ear can receive. Another route may be reading with blue laser beams after recording the data to a narrower and smaller extent, but this procedure is still used only in the laboratory. It is an IBM multilayer disk, so for now it has all the advantages. However, it has not yet done more than start the road and within a year they hope to market the album first in two layers. At the moment making a 4 or 6 layer disc costs a lot.