EP0241978A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Optical record carrier and apparatus for reading the record carrier
Assignee: Philips and Du Pont Optical Co BV
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Filing: 1987-04-03
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Granted: —
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Expires: 2007-04-03
Abstract
Abstract The recording surface of an optical record carrier (1) is divided into first (A) and second annular zones (B) which are situated concentrically around a centre of rotation (4). The annular zones (A) are provided with groups of radially aligned first control structures (13), whilst the annular zones (B) are provided with groups of radially aligned second control structures (14). An optical scanning device for optically scanning the structure of the information carrier (1) at the location of the scanning spot (54) projected on the record carrier by the scanning device comprises a detection circuit (70) which in the case of a radial movement of the scanning spot (54) detects first and second control structures (13; 14) and derives a measurement signal Vm which indicates the passage of the boundaries between the zones A and B during a radial movement of the scanning spot 54. The measurement signal Vm is very suitable for the control of a system for rapidly addressing the scanning spot 54 to one of the annular zones (A; B).
Inventors
- 👤 Johannes Jacobus Verboom
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 02:08
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/007; G11B7/013; G11B7/24; G11B7/2407; G11B7/24085; G11B7/004; G11B7/005; G11B7/08; G11B7/085; G11B7/08505
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
117 words
An optical record carrier which is or can be provided with an information structure arranged along tracks, which tracks are situated substantially concentrically around a centre of rotation, the carrier comprising first and second annular zones which can be distinguished from each other and which are situated concentrically around the center of rotation, characterized in that the record carrier is provided with first and second control structures which can be distinguished from each other and from the information structure, the first zones being provided with groups of radially adjoining first control structures and the second areas being provided with groups of radially adjoining second control structures in order to distinguish between the first zones and second zones.
Claim 2
Dependent Claim
117 words
An optical record carrier which is or can be provided with an information structure arranged along tracks, which tracks are situated substantially concentrically around a centre of rotation, the carrier comprising first and second annular zones which can be distinguished from each other and which are situated concentrically around the center of rotation, characterized in that the record carrier is provided with first and second control structures which can be distinguished from each other and from the information structure, the first zones being provided with groups of radially adjoining first control structures and the second areas being provided with groups of radially adjoining second control structures in order to distinguish between the first zones and second zones.
Claim 3
Dependent Claim
38 words
An optical record carrier as claimed in Claim 1, characterized in that the control structures are arranged along substantially concentric tracks in such a way that along the tracks the structure alternately comprises control structures and information structures.
Claim 4
Dependent Claim
50 words
An optical record carrier as claimed in Claim 1 or 2, characterized in that over the entire width of the annular zones the control structures are situated at locations which are defined by at least one group of radii issuing from the centre of rotation and having equal angular spacings.
Claim 5
Dependent Claim
98 words
An optical record carrier as claimed in Claim 3, characterized in that the first and the second control structures differ from each other in that first and second detectable areas are displaced by a first and a second predetermined angle respectively relative to the radii, the first detectable areas in the first control structures producing a first modulation and the second detectable areas in said first control structures producing a different second modulation of the read beam and said areas in the second control structures producing said second modulation and said first modulation of the read beam respectively.
Claim 6
Independent Claim
182 words
An apparatus for reading a record carrier as claimed in any one of the Claims 1 to 4, which apparatus comprises drive means for rotating the information carrier about the centre of rotation, a radiation source producing a read beam, an objective system for focussing the read beam to form a scanning spot on the record carrier and subsequently directing the read beam to a radiation-sensitive detection system, the scanning spot being radially movable in the plane of rotation of the record carrier under control of a radial actuating device, and the detection system for reading the information structure converting the modulation of the read beam produced by the structure on the record carrier into an electric signal, characterized in that the apparatus comprises a detection circuit for deriving a measurement signal from first and second components of the electric signal corresponding to the modulated radiation beam as it scans the first and the second control structures respectively, which measurement signal indicates the passage of a boundary between the first and the second zones during a radial movement of the scanning spot.
Claim 7
Dependent Claim
95 words
An apparatus as claimed in Claim 5, characterized in that the apparatus comprises a synchronizing circuit for deriving from the electric signal first and second control signals which are synchronous with the incidence of the scanning spot on the first and the second detectable areas respectively, a sample-and-hold circuit for taking first and second samples of the electric signal in response to the first and second control signals, and a circuit for comparing the first and the second samples with each other and for generating the measurement signal depending on the result of the comparison.
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GB1435603A
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GB1516285A
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US4507763A
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EP0081138A2
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EP0097092A1
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WO1985001380A1
Cited
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