Patent EP0605924A2 successfully refreshed from Google Patents.
EP0605924A2
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EP
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Multiplane information storage system and record carrier for use in such a system
Assignee: Koninklijke Philips NV
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Filing: 1993-12-24
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Granted: —
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Expires: 2013-12-24
Abstract
Abstract An information storage system is described which comprises a reading device (6) and an optical record carrier (5) having at least two information planes (1, 2, 3). The radiation from the record carrier is converted in a detection system (15) into a detection signal (16) which is applied to a detection circuit (17). In order that this circuit can derive the read information from the detection signal in a reliable manner, the interference signals generated by the information planes which are not to be read should comply with a requirement, referred to as the interference requirement, which is characteristic of the detection circuit. Values for the parameters of the record carrier, such as the thickness of the layers between the information planes and the reflection and transmission coefficients of the information planes then follow from this interference requirement.
Inventors
- 👤 Antonius Hendricus Maria Holtslag
- 👤 Derk Visser
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 10:39
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/004; G11B7/005
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
171 words
An information storage system comprising an optical record carrier having at least two information planes, and a reading device for scanning the information planes from one side of the record carrier, said device comprising a first optical system for forming a radiation spot on an information plane to be read, a second optical system for passing radiation from the record carrier to a radiation-sensitive detection system which converts the radiation into an electric detection signal, and a detection circuit electrically connected to the detection system for converting the detection signal into an information signal, characterized in that the distances between the information planes and the optical properties of the information planes comply with the interference requirement of the information storage system, i.e. the ratio between the sum of interference signals in the detection signal generated by the information planes not to be read and a read signal in the detection signal generated by the information plane to be read is smaller than an interference ratio Q determined by the detection circuit.
Claim 2
Dependent Claim
174 words
An information storage system as claimed in Claim 1, characterized in that the interference requirement is defined by in which the summation over j is over all information planes not being the information plane i to be read, and the summation over f is over the frequencies present in the signal received from an information plane, while E j is the power of the radiation in the zeroth diffraction order from information plane j, m j (f) is the modulation factor at frequency f of the information plane j, in which m j (f) for an information plane not to be read is determined with the radiation beam focused on plane j, and in which further MTF(f,d j /n) is the modulation transfer function at the frequency f of the radiation from the information plane j to the detection signal, d j is the distance between the information plane j and the information plane i to be read, and n is the refractive index of the medium between the information planes i and j.
Claim 3
Dependent Claim
30 words
An information storage system as claimed in Claim 1, characterized in that the interference requirement is defined by in which the parameters have the meaning as defined in Claim 2.
Claim 4
Dependent Claim
47 words
An information storage system as claimed in Claim 1, characterized in that the record carrier has at least three information planes and in that the sum in said interference requirement includes imaginary information planes each constituted by mirroring an information plane with respect to another information plane.
Claim 5
Dependent Claim
112 words
An information storage system as claimed in Claim 2 or 3, characterized in that a first information plane has an information structure which is optimally read in a first read mode, and at least a second information plane has an information structure which is optimally read in a second read mode, in that the reading device has the disposal of both read modi and in that in the interference requirement the parameters E j , m j and MTF(f,d j /n) for an information plane which is not to be read have those values which are associated with the read mode in which the information plane i to be read is read.
Claim 6
Dependent Claim
44 words
An information storage system as claimed in Claim 5, characterized in that the radiation source is adapted to supply a radiation beam having a first wavelength in the first read mode and a radiation beam having a second wavelength in the second read mode.
Claim 7
Dependent Claim
48 words
A reading device as claimed in Claim 5 or 6, characterized in that the detection system has the disposal of two detection modi for detecting, in the first and the second read mode, the radiation from the record carrier in the first and the second detection mode, respectively.
Claim 8
Dependent Claim
103 words
An information storage system as claimed in Claim 2 or 3, characterized in that the record carrier has at least three information planes, in that the detection system is arranged in the path of radiation reflected by the record carrier, and in that for an information plane j which is situated closer to the objective system than the information plane i, and for an information plane j which is situated further remote from the objective system than the information plane i, in which R k and T k are the radiation intensity reflection and the radiation intensity transmission, respectively, of information plane k.
Claim 9
Dependent Claim
56 words
An information storage system as claimed in Claim 4, characterized in that the optical properties of the information planes comply with in which d ₁ and d ₂ are the distances between the information planes 1 and 2, and 2 and 3, respectively, and n is the refractive index of the media between the information planes.
Claim 10
Dependent Claim
61 words
An information storage system as claimed in Claim 9, characterized in that the information planes comprise information having a substantially equal frequency spectrum, in that m ₁, m ₂ and m ₃ are equal to each other, d ₁ is equal to d ₂, and in that holds for the radiation intensity reflections and radiation intensity transmissions of the information planes.
Claim 11
Dependent Claim
32 words
An information storage system as claimed in Claim 8, characterized in that the radiation intensity reflection coefficients of the successive information planes with an increasing distance of the objective system comply with
Claim 12
Dependent Claim
165 words
An information storage system as claimed in any one of Claims 2 to 11, characterized in that the information in the information planes is ordered in tracks extending in a tangential direction, denoted by the subscript t, and in that the modulation transfer function MTF(f,d) is given by MTF ( f,d ) = MTF t ( f,d ) F r ( q,d ) in which, expressed in the dimensionless parameters the tangential modulation transfer function is given by with S being the area defined by and in which the radial function is given by in which f c = NA/ λ is the cut-off frequency of the objective system, λ is the wavelength of the radiation beam, NA is the numerical aperture of the objective system at the side of the record carrier, q is the track period, r d is the effective radius of the detection system, and M is the magnification of the optical system from the record carrier to the detection system.
Claim 13
Dependent Claim
36 words
An information storage system as claimed in Claim 2 or 3, characterized in that the radiation received by the detection system is transmitted by the record carrier, and in that E j = E i .
Claim 14
Dependent Claim
131 words
An information storage system as claimed in Claim 2, 3 or 13, characterized in that the optical system comprises a collector lens for passing radiation transmitted by the record carrier to the detection system, in which the numerical aperture of the collector lens is equal to the numerical aperture of the objective system, and in that the information in the information planes is ordered in tracks extending in a tangential direction, denoted by the subscript t, and in that the modulation transfer function MTF(f,d) is given by MTF'(f,d) = MTF' t (f,d) F r (q,d) in which, expressed in the dimensionless parameters, the tangential modulation transfer function is given by with S being the area defined by and in which the other parameters have the meaning as defined in Claim 12.
Claim 15
Dependent Claim
27 words
An optical carrier having at least two information planes and comprising all the technical record carrier features as defined in any one of Claims 1 to 14.
Claim 16
Dependent Claim
42 words
An optical carrier as claimed in Claim 15, characterized in that it comprises three information planes and two intermediate layers separating the information planes from one another, the ratio of the optical thicknesses of the intermediate layers ranging between 1,5 and 3.
Claim 17
Dependent Claim
34 words
An optical record carrier as claimed in Claim 15, characterized in that it comprises information planes with interposed intermediate layers, the successive intermediate layers having thicknesses alternating with each other in two different values.
References Cited (Backward Citations)
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