Abstract: The invention relates to an optical disc (35, 36, 37) comprising a magnetic substrate (10, 20, 30) and to an optical recording and/or reproducing apparatus for recording and/or reproducing such an optical disc. By virtue of its magnetic properties, said magnetic substrate is able to clamp the optical disc onto a turntable of said recording and/or reproducing apparatus instead of a hub.

Abstract: The invention relates to a data carrier comprising a first area (12) comprising a rewritable material, said first area being defined as a read-only area by means of type information recorded on said data carrier in an unerasable way.

Abstract: With the disc-shaped recording medium, or the disc manufacturing method according to the present invention, for both the single-layer disc and the multi-layer disc, a recording layer L0, which is to be the first layer, is at the same distance, along the direction of disc thickness, from the surface of the cover layer CVLs on which falls the laser light. For the multi-layer disc, the second layer L1 and the following layer(s) are formed at the locations which are closer to the cover layer CVLs than the first layer L0. Management information may be recorded by mobbling grooves, each layermay have tert areas, defect information, a replacement area. Thus, it is possible to improve compatibility, reliability and accessibility between a single-layer disc and a multi-layer disc. The spherical aberration for the recording/reproducing light may be controlled with respect to the selected layer.

Abstract: An optical record carrier for use in an optical scanning device, the optical record carrier comprising an entrance face (5), an information layer (3) and at least one transparent layer (2), located between the entrance face and the information layer, through which data is to be read from the information layer, wherein the information layer includes a relief structure (31a . . . 31d, 32a . . . 32d; 33) holding data in read-only form. The data held in the relief structure includes thickness variation data indicative of a variation in the thickness of the optical record carrier between the entrance face and the information layer, due to a variation in the thickness of the at least one transparent layer. At the time of manufacturing of the data carriers, the relief structure comprising the thickness varation data is stamped before the transparent layer is formed.

Abstract: An optical data storage medium (10) is described for read out using a focused radiation beam (19) with a wavelength ? sand a Numerical Aperture NA. The medium has a substrate (11) and a first stack of layers named L0 (12) comprising a first information layer and optionally at least one further stack of layers named Ln (13), comprising a further information layer. A radiation beam (19) transparent spacer layer (14) is present between each of L0 and Ln. A transmission stack named TS0 with a thickness dTS0 contains all layers between L0 (12) and an entrance face (16) of the medium (10). A transmission stack named TSn with a thickness dTSn contains all layers between Ln (13) and the entrance face (16). The maximum deviation of dTS0 and when applicable dTSn does not exceed a predetermined value DEVdTS0 or DEVdTSn, measured over the information area of the medium (10) and this value is set in dependency of ? and NA.

Abstract: A description is given of a rewritable optical storage medium (10) comprising a substrate (1), a first dielectric layer (2), a phase-change recording layer (3) on the basis of Ge—Sb—Te, a second dielectric layer (4), and a metal reflective layer (5). The recording layer (3) is an alloy having the composition GexSbyTez, in atom %, wherein 0<x<15, 50<y<80, 10<z<30 and x+y+z=100, and the recording layer (3) has a thickness selected from the range of 7 to 18 nm. Such a medium (10) is suitable for high data rate recording with a data rate of larger than 25 Mb/s while the recording layer (6) remains relatively thin having a relatively high optical transparency.