EP0246597A2
Expired / Lapsed
EP
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Method of reproducing signals from optical disk
Assignee: Panasonic Holdings Corp
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Filing: 1987-05-18
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Granted: —
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Expires: 2007-05-18
Abstract
Abstract A method of reproducing signals formed in slant surfaces of a V-shaped track groove formed in an optical disk. The beam reflected from each slant surface has a portion having a small crosstalk component and a portion having a large crosstalk component, the portions existing separately. The beam reflected from the V-shaped track groove is detected by a photodetector which is composed of two photodetector units. Thus, the output from the first photodetector unit has a small crosstalk component, while the output from the second photodetector unit has a large crosstalk component. The reproduced signal is obtained by subtracting, from a signal formed by amplifying the output of the first photodetector unit, a signal formed by amplifying the output of the second photodetector unit, so that the crosstalk component in the signal from the first photodetector unit is negated by the crosstalk component in the signal from the second photodetector unit, so that the reproduced signal can have a reduced crosstalk component. At the same time, the strictness of requirement for design and positional accuracy of the photodetector is reduced. It is also to arrange such that signals are simultaneously and independently reproduced from adjacent slant surfaces of the V-shaped track groove by a single laser beam spot.
Inventors
- 👤 Michiyoshi Nagashima
- 👤 Yoshinari Takemura
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 04:38
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/004; G11B7/005; G11B7/24; G11B7/2407; G11B7/24073; G11B7/24076
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
103 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: using, as said photodetector, a split-type photodetector having first and second photodetector units; and obtaining the reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit.
Claim 2
Independent Claim
103 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: using, as said photodetector, a split-type photodetector having first and second photodetector units; and obtaining the reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit.
Claim 3
Independent Claim
37 words
A method of reproducing signals from an optical disk according to Claim l, wherein said first and second photodetector units are arranged in symmetry with each other with respect to the neutral axis of the reflected beam.
Claim 4
Independent Claim
47 words
A method of reproducing signals from an optical disk according to Claim l or 2, wherein the amplification factor by which the output from said first photodetector unit is amplified is greater than the amplification factor by which the output from said second photodetector unit is amplified.
Claim 5
Independent Claim
182 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: dividing a single laser beam by means of a diffraction grating into a plurality of portions so as to form three beam portions such that three beam spots are arrayed on said track groove; effecting a tracking control such that the central beam spot follows the crest or the valley of said track groove while allowing other two beam spots to follow opposing slant surfaces of said track groove thus enabling these two spots as reading spots; receiving the reflected beams from said reading spots by first and second photodetector units, respectively; and obtaining the reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit.
Claim 6
Independent Claim
182 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: dividing a single laser beam by means of a diffraction grating into a plurality of portions so as to form three beam portions such that three beam spots are arrayed on said track groove; effecting a tracking control such that the central beam spot follows the crest or the valley of said track groove while allowing other two beam spots to follow opposing slant surfaces of said track groove thus enabling these two spots as reading spots; receiving the reflected beams from said reading spots by first and second photodetector units, respectively; and obtaining the reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit.
Claim 7
Independent Claim
163 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: focusing said laser spot on the crest or valley of said track groove; receiving the reflected beam by first and second photodetector units; determining a first reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit; and determining a second reproduced signal by subtracting, from a signal obtained by amplifying the output of said second photodetector unit, a signal obtained by amplifying the output of said first photodetector unit; whereby signals are simultaneously and independently reproduced from adjacent slant surfaces by a single laser beam spot.
Claim 8
Independent Claim
163 words
A method of reproducing signals from an optical disk with a track groove having a V-shaped radial section defined by opposing slant surfaces each of which carry signals recorded therein, the reproduction being conducted by focusing a laser beam on said track groove in said optical disk and receiving the reflected beam by a photodetector, said method comprising: focusing said laser spot on the crest or valley of said track groove; receiving the reflected beam by first and second photodetector units; determining a first reproduced signal by subtracting, from a signal obtained by amplifying the output of said first photodetector unit, a signal obtained by amplifying the output of said second photodetector unit; and determining a second reproduced signal by subtracting, from a signal obtained by amplifying the output of said second photodetector unit, a signal obtained by amplifying the output of said first photodetector unit; whereby signals are simultaneously and independently reproduced from adjacent slant surfaces by a single laser beam spot.
References Cited (Backward Citations)
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