Optical data storage medium and use of such medium

Details Optical data storage medium and use of such medium Optical data storage medium and use of such medium

G - Physics

11

B

G11B 7/24 (2006.01) G11B 7/007 (2006.01) G11B 7/09 (2006.01)

Patent

CA 2473550

An optical data storage medium (20) for recording by means of a focused radiation beam (29) is described. The radiation beam having a wavelength .lambda. enters through an entrance face (28) of the medium during recording. The medium has a substrate (21) with a surface (24) including a guide groove with a depth g. An inverted stack of layers is present on the substrate (21) including a reflective layer (24a) with a complex refractive index ñM.lambda. = nM.lambda. - i*kM.lambda., in substantial conformity with the surface (24) of the substrate, a transparent layer (22) through which the radiation beam (29) is incident with a complex refractive index ñT.lambda. = nT.lambda. - i*kT.lambda. and a recording layer (25) of a material having a complex refractive index ñR.lambda. = nR.lambda. - i*kR.lambda. and having a thickness dRG in the groove portion and a thickness dRL in the portion between grooves. The recording layer is interposed between the reflective layer (24a) and the transparent layer (22). When 0.25/(3.0+ kM.lambda.2) + 0.17 < g*nT/.lambda. < 0.22/(3.0 + kM.lambda.2) + 0.45 and 0.2 < (dRG - dRL)/g < 0.5 and 0 < dRG < .lambda./nR.lambda. and kR.lambda. < 0.5 and 2 < nR.lambda. < 2.6 the sign of the push pull tracking signal is reversed. In such way the inverted recording stack is tracked properly without modifications to the optical drive and backwards compatibility is achieved.

L'invention concerne un support de stockage de données optiques (20) permettant d'enregistrer au moyen d'un faisceau de rayonnement focalisé (29). Ce faisceau de rayonnement possède une longueur d'onde .lambda. traversant une surface (24), notamment une rainure guide ayant une profondeur g. Un empilement de couches inversées est présent sur le substrat (21), notamment une couche rétroréfléchissante (24a) à indice de réfraction complexe ñ<sb>M.lambda.</sb> = n<sb>M.lambda.</sb> - i*k<sb>M.lambda., </sb>en quasi conformité avec la surface (24) du substrat, une couche transparente (22) à travers laquelle le faisceau de rayonnement (29) est incident à indice de réfraction complexe ñ<sb>T.lambda.</sb> = n<sb>T.lambda.</sb> - i*k<sb>T.lambda.,</sb> et une couche d'enregistrement (25) d'un matériau possédant un indice de réfraction complexe ñ<sb>R.lambda.</sb> = n<sb>R.lambda.</sb> - i*k<sb>R.lambda. </sb>et une épaisseur d<SB>RG</SB> dans la partie rainure et une épaisseur d<SB>RL</SB> dans la partie située entre ces rainures. La couche d'enregistrement est intercalée entre la couche rétroréfléchissante (24a) et la couche transparente (22). Lorsque 0,25/(3,0+ k<sb>M.lambda.</sb><sp>2</sp>)+0,17<g*n<SB>T</SB>/.lambda.<0,22/(3,0+ k<sb>M.lambda.</sb><sp>2</sp>)+0,45 et 0,2<(d<SB>RG</SB>-d<SB>RL</SB>)/g<0,5 et 0<d<SB>RG</SB><.lambda./n<sb>R.lambda.</sb> et k<sb>R.lambda.</sb><0,5 et 2<n<sb>R.lambda.</sb><2,6 le signe du signal de poursuite symétrique est inversé. Ainsi, l'empilement d'enregistrement inversé est poursuivi avec efficacité sans modification de l'unité de disques optiques, la compatibilité descendante étant atteinte.

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