Multi-layer information recording medium and information recording and reproducing apparatus

Abstract

A multi-layer-information-recording medium is applied to an information recording and reproducing apparatus capable of recording or reproducing information on and from either of a single-layer-information-recording medium having a single recording layer on one side, and a multi-layer-information-recording layer having a plurality of recording layers layered on a spacer layer on one side as a change in reflectivity by irradiating a light beam. The multi-layer-information-recording medium is compatible in terms of at least reproducing and recording with a single-layer-information-recording medium having a cover layer having a predetermined refractive index “n” and a thickness “t” disposed on a recording layer on a light incident side surface. The multi-layer-information-recording medium includes a deepest recording layer deepest from the light incident side surface. The deepest recording layer is formed at an optical distance d 1 from the light incident side surface satisfying an equation d 1 =nt. The multi-layer-information-recording medium also includes at least one shallow recording layer formed at an optical distance d 2 satisfying an inequality d 2 <nt from the light incident side surface.

1. A multi-layer-information-recording medium having a plurality of recording layers layered on a spacer layer on one side and adapted to an information recording and reproducing apparatus capable of recording or reproducing information on a single-layer-information-recording medium having a single recording layer and a cover layer on one side as a change in reflectivity  by irradiating a light beam through the cover layer onto the recording layer, said multi-layer-information-recording medium comprising:
 a deepest recording layer disposed deepest from a light incident side surface at an optical distance d 1  satisfying an equation d 1 =nt wherein “n” denotes a predetermined refractive index of the cover layer of the single-layer-information-recording medium compatible in terms of at least reproducing and recording with said multi-layer-information-recording medium and “t” denotes a thickness of said cover layer; and  
 at least one shallow recording layer disposed at an optical distance d 2  satisfying an inequality d 2 <nt from the light incident side surface.  
 
     
     
       2. A multi-layer-information-recording medium according to  claim 1 , wherein said multi-layer-information-recording medium consists of said deepest recording layer and said shallow recording layer as only two layers. 
     
     
       3. A multi-layer-information-recording medium according to  claim 1 , wherein said multi-layer-information-recording medium includes physical address information recorded sequentially from said shallow recording layer to said deepest recording layer in a shallower order from the light incident side surface. 
     
     
       4. A multi-layer-information-recording medium according to  claim 1 , wherein said multi-layer-information-recording medium includes physical address information sequentially recorded in order from an inner periphery to an outer periphery of said deepest recording layer. 
     
     
       5. A multi-layer-information-recording medium according to  claim 4 , wherein said multi-layer-information-recording medium includes the physical address information sequentially recorded alternately in a forward direction from the inner periphery to the outer periphery and in an opposite direction from the outer periphery to the inner periphery in each of the recording layers from said shallow recording layer to said deepest recording layer in the shallower order from the light incident side surface. 
     
     
       6. A multi-layer-information-recording medium according to  claim 1 , wherein said multi-layer-information-recording medium includes predetermined content information related to all contents on said shallow recording layer recorded in said deepest recording layer. 
     
     
       7. An information recording and reproducing apparatus capable of recording or reproducing information on either of a single-layer-information-recording medium having a single recording layer and a multi-layer-information-recording medium having a plurality of recording layers layered on a spacer layer on one side by irradiating a light beam thereto, said information recording and reproducing apparatus comprising:
 an optical pickup having an objective lens which irradiates a light beam to a multi-layer-information-recording medium which includes a deepest recording layer disposed deepest from a light incident side surface at an optical distance d 1  satisfying an equation d 1 =nt wherein “n” denotes a predetermined refractive index of the cover layer of the single-layer-information-recording medium compatible in terms of at least reproducing and recording with said multi-layer-information-recording medium and “t” denotes a thickness of said cover layer, and at least one shallow recording layer disposed at an optical distance d 2  satisfying an inequality d 2 <nt from the light incident side surface; and  
 a focus servo circuit which controls the objective lens to first of all focus the light beam to said deepest recording layer at the optical distance d 1 , and executes an initial focus servo operation.  
 
     
     
       8. An information recording and reproducing apparatus according to  claim 7 , wherein said focus servo circuit executes a focus servo operation for jumping a focused position to said shallow recording layer at the optical distance d 2  after executing said initial focus servo operation. 
     
     
       9. An information recording and reproducing apparatus according to  claim 7 , wherein said objective lens has a numerical aperture equal to or larger than 0.8 for producing a focused spot of the light beam. 
     
     
       10. An information recording and reproducing apparatus according to  claim 9 , further comprising an wave aberration correcting portion which varies the amount of wave aberration included in said focused spot. 
     
     
       11. An information recording and reproducing apparatus according to  claim 9 , wherein said objective lens comprises a group of lenses which minimizes the amount of wave aberration in the light beam when the spot is focused at a position spaced by the optical distance d 1 . 
     
     
       12. A multi- layer - information - recording medium that is compatible with a single - layer - information - recording medium in terms of reproducing or recording, the single - layer - information - recording medium having a cover layer having a refractive index “n” and a thickness “t” on the light incident side,      said multi - layer - information - recording medium comprising a first recording layer and a second recording layer that are layered in order from the light incident side surface of the multi - layer - information - recording medium,        wherein the second recording layer is disposed at an optical distance “d 1 ” from the light incident side surface satisfying an equation d 1 =n×t; and        wherein the first recording layer is disposed at an optical distance “d 2 ” from the light incident side surface satisfying an inequality d 2 <n×t.     
     
     
       13. A multi- layer - information - recording medium that is compatible with a single - layer - information - recording medium in terms of reproducing or recording, the single - layer - information - recording medium having a cover layer having a refractive index “n” and a thickness “t” on the light incident side,      said multi - layer - information - recording medium comprising a cover layer, a first recording layer, a spacer layer, and a second recording layer that are layered in order from the light incident side surface of the multi - layer - information - recording medium,        wherein on condition that the cover layer has a refractive index “nC” and a thickness “tC” and the first recording layer has a refractive index “nL 1 ” and a thickness “tL 1 ” and the spacer layer has a refractive index “nS” and a thickness “tS”, the second recording layer is disposed at an optical distance “d 1 ” from the light incident side surface satisfying an equation d 1 =n×t=nC×tC+nL 1 ×tL 1 +nS×tS; and        wherein the first recording layer is disposed at an optical distance “d 2 ” from the light incident side surface satisfying an equation d 2 =nC×tC<n×t.     
     
     
       14. A multi- layer - information - recording medium that is compatible with a single - layer - information - recording medium in terms of reproducing or recording, the single - layer - information - recording medium having a cover layer having a refractive index “n” and a thickness “t” on the light incident side,      said multi - layer - information - recording medium comprising a deepest recording layer and one or more shallow recording layers shallower than the deepest recording layer that are layered in order from the light incident side surface of the multi - layer - information - recording medium,        wherein the deepest recording layer is disposed at an optical distance “d 1 ” from the light incident side surface satisfying an equation d 1 =n×t; and        wherein the shallow recording layer is disposed at an optical distance “d 2 ” from the light incident side surface satisfying an inequality d 2 <n×t.     
     
     
       15. A multi- layer - information - recording medium according to    claim 14   , wherein said multi - layer - information - recording medium consists of said deepest recording layer and said shallow recording layer as only two layers.   
     
     
       16. An information reproducing apparatus capable of reproducing information on either of a single- layer - information - recording - medium and a multi - layer - information - recording medium,      wherein the single - layer - information - recording - medium having a cover layer having a refractive index “n” and a thickness “t” on the light incident side, and        wherein said multi - layer - information - recording - medium comprises a deepest recording layer and one or more shallow recording layers shallower than the deepest recording layer that are layered in order from the light incident side surface of the multi - layer - information - recording - medium, and        wherein the deepest recording layer is disposed at an optical distance “d 1 ” from the light incident side surface satisfying an equation d 1 =n×t; and        wherein the shallow recording layer is disposed at an optical distance “d 2 ” from the light incident side surface satisfying an inequality d 2 <n×t;        said information reproducing apparatus includes a focus servo circuit that executes an initial focus servo operation first of all for said deepest recording layer at the optical distance d 1 .     
     
     
       17. An information reproducing apparatus according to  claim 16 , wherein said focus servo circuit executes a focus servo operation for jumping a focused position to said shallow recording layer at the optical distance d 2  after executing said initial focus servo operation. 
     
     
       18. An information reproducing apparatus according to  claim 16 , further comprising an objective lens having a numerical aperture equal to or larger than  0 . 8  for producing a focused spot of the light beam. 
     
     
       19. An information reproducing apparatus according to  claim 18 , further comprising a wave aberration correcting portion which varies the amount of wave aberration included in said focused spot. 
     
     
       20. An information reproducing apparatus according to  claim 18 , wherein said objective lens comprises a group of lenses which minimizes the amount of wave aberration in the light beam when the spot is focused at a position spaced by the optical distance d 1 . 
     
     
       21. An information recording apparatus capable of recording or reproducing information on either of a single- layer - information - recording - medium and a multi - layer - information - recording medium,      wherein the single - layer - information - recording - medium having a cover layer having a refractive index “n” and a thickness “t” on the light incident side, and        wherein said multi - layer - information - recording - medium comprises a deepest recording layer and one or more shallow recording layers shallower than the deepest recording layer that are layered in order from the light incident side surface of the multi - layer - information - recording - medium, and        wherein the deepest recording layer is disposed at an optical distance “d 1 ” from the light incident side surface satisfying an equation d 1 =n×t; and        wherein the shallow recording layer is disposed at an optical distance “d 2 ” from the light incident side surface satisfying an inequality d 2 <n×t;        said information recording apparatus includes a focus servo circuit that executes an initial focus servo operation first of all for said deepest recording layer at the optical distance d 1 .     
     
     
       22. An information recording apparatus according to  claim 21 , wherein said focus servo circuit executes a focus servo operation for jumping a focused position to said shallow recording layer at the optical distance d 2  after executing said initial focus servo operation. 
     
     
       23. An information recording apparatus according to  claim 21 , further comprising an objective lens having a numerical aperture equal to or larger than  0 . 8  for producing a focused spot of the light beam. 
     
     
       24. An information recording apparatus according to  claim 23 , further comprising a wave aberration correcting portion which varies the amount of wave aberration included in said focused spot. 
     
     
       25. An information recording apparatus according to  claim 23 , wherein said objective lens comprises a group of lenses which minimizes the amount of wave aberration in the light beam when the spot is focused at a position spaced by the optical distance d 1 . 
     
     
       26. An information reproducing apparatus for reproducing information from a multi- layer - information - recording medium according to    claim 12   .   
     
     
       27. An information reproducing apparatus for reproducing information from a multi- layer - information - recording medium according to    claim 13   .   
     
     
       28. An information reproducing apparatus for reproducing information from a multi- layer - information - recording medium according to    claim 14   .   
     
     
       29. An information reproducing apparatus for reproducing information from a multi- layer - information - recording medium according to    claim 15   .