US5677903A
Expired / Lapsed
US
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Multi-layer information storage system with improved aberration correction
Assignee: US Philips Corp
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Filing: 1994-09-01
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Granted: 1997-10-14
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Expires: 2014-09-01
Abstract
Abstract An optical information storage system has a multi-recording layer record carrier and a scanner device for the carrier. The scanner produces a radiation beam which is compensated for spherical aberration for a single height of the scanning spot with the stack of layers. The height of the stack is determined by the maximum spherical aberration permissible for the system. The number of layers in the stack is determined by the minimum distance between layers, which depends on the crosstalk in the error signals due to currently unscanned layers.
Inventors
- 👤 Antonius H. M. Holtslag
- 👤 Derk Visser
- 👤 Peter Coops
- 👤 Jacobus P. J. Heemskerk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:04
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/004; G11B7/005; G11B7/08; G11B7/085; G11B7/08505; G11B7/08511; G11B7/09; G11B7/0901; G11B7/0903; G11B7/12; G11B7/135; G11B7/1353; G11B7/1365; G11B7/1369; G11B7/1372; G11B7/1378; G11B7/1392; G11B7/13925; G11B7/14; G11B7/24; G11B7/2403; G11B7/24035; G11B7/24038; G11B2007/0003; G11B2007/0009; G11B2007/0013; G11B2007/13727; G11B7/0908; G11B7/0909; G11B7/0948; G11B7/13
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
97 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that the focusing means introduce such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 2
Dependent Claim
97 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that the focusing means introduce such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 3
Dependent Claim
41 words
An information storage system as claimed in claim 1, characterized in that said stack of information layers has a height no greater than approximately 100 μm, and said focusing means comprises an objective system having a numerical aperture of approximately 0.52.
Claim 4
Dependent Claim
34 words
An information storage system as claimed in claim 1, characterized in that said focusing means comprises a single corrector plate only, placed in an uncollimated part of the radiation beam, for compensating spherical aberration.
Claim 5
Dependent Claim
44 words
An information storage system as claimed in claim 1, characterized in that the thickness of the stack is smaller than 2d which is a function of the refractive index of the material of the stack and of the numerical aperture of the focusing means.
Claim 6
Dependent Claim
34 words
An information storage system as claimed in claim 4, characterized in that 2d is also a function of the maximally admissible decrease of the Strehl intensity of the radiation beam due to spherical aberration.
Claim 7
Dependent Claim
100 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that during reading the focusing means continuously introduces such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 8
Dependent Claim
100 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that during reading the focusing means continuously introduces such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 9
Dependent Claim
40 words
An information system as claimed in claim 6, characterized in that said stack of information layers has a height no greater than approximately 100 μm, and said focusing means comprises an objective system having a numerical aperture of approximately 0.52.
Claim 10
Dependent Claim
33 words
An information system as claimed in claim 6, characterized in that said focusing means comprises a single corrector plate only, placed in an uncollimated part of the radiation beam, for compensating spherical aberration.
Claim 11
Dependent Claim
43 words
An information system as claimed in claim 6, characterized in that the thickness of the stack is smaller than 2d which is a function of the refractive index of the material of the stack and of the numerical aperture of the focusing means.
Claim 12
Dependent Claim
33 words
An information system as claimed in claim 9, characterized in that 2d is also a function of the maximally admissible decrease of the Strehl intensity of the radiation beam due to spherical aberration.
Claim 13
Dependent Claim
200 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that: the thickness of the stack is smaller than 2d which is a function of the refractive index of the material of the stack, of the numerical aperture of the focusing means, and of the maximally admissible decrease of the Strehl intensity of the radiation beam due to spherical aberration, the value 2d is defined by the equation ##EQU4## in which n is the refractive index of the spacer layers, λ is the vacuum wavelength of the radiation beam, NA is the numerical aperture of the focusing means, and r is the maximally admissible decrease of the Strehl intensity due to spherical aberration, and the focusing means introduces such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 14
Dependent Claim
200 words
An information storage system comprising an optical record carrier having a stack of information layers alternating with spacer layers, and a device for scanning the information layers, which device is provided with a radiation source and focusing means for selectively focusing a radiation beam from the radiation source on the separate information layers, characterized in that: the thickness of the stack is smaller than 2d which is a function of the refractive index of the material of the stack, of the numerical aperture of the focusing means, and of the maximally admissible decrease of the Strehl intensity of the radiation beam due to spherical aberration, the value 2d is defined by the equation ##EQU4## in which n is the refractive index of the spacer layers, λ is the vacuum wavelength of the radiation beam, NA is the numerical aperture of the focusing means, and r is the maximally admissible decrease of the Strehl intensity due to spherical aberration, and the focusing means introduces such a fixed, stack-associated spherical aberration in the radiation beam that this aberration compensates the spherical aberration incurred by the radiation beam when it is focused at approximately half the height of the stack of information layers.
Claim 15
Dependent Claim
55 words
An information storage system as claimed in claim 11, in which the record carrier comprises a transparent substrate having an entrance face for the radiation beam at one side and said stack at the other side, characterized in that the thickness of the stack is smaller than 2d minus the thickness tolerance of the substrate.
Claim 16
Dependent Claim
15 words
An information storage system as claimed in claim 11, wherein r is equal to 0.05.
Claim 17
Dependent Claim
15 words
An information storage system as claimed in claim 11, wherein r is equal to 0.01.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-10-13 | 2001-04-14 | 2001-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-10-13 | 2005-04-14 | 2005-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-10-13 | 2009-04-14 | 2009-10-14 | $7700.00 | Window Closed / Lapsed |