EP0210330A2
Expired / Lapsed
EP
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Method and apparatus for composite wobbled tracking servo system
Assignee: Hitachi Ltd
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Filing: 1986-03-29
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Granted: —
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Expires: 2006-03-29
Abstract
Abstract A composite wobbled tracking servo system uses a rotary optical disc (10) which has a header field (123) and a data field (122) alternately arranged along the direction of rotation to provide a sector, and which includes pregrooves (15-1, 15-2) formed in at least the data field and at least one pair of wobbled track marks (20-1, 20-2) disposed in the header field in relation wobbled relative to the center of a track. A light spot (11) is directed toward and onto the optical disc to detect a push-pull tracking error signal (16) from the reflection of the light spot diffracted by the pregroove (15), and a wobbled tracking error signal (24; 45) is detected from the reflection of the light spot traversing the wobbled track marks. The push-pull tracking error signal is corrected on the basis of the wobbled tracking error signal to attain the tracking control with higher accuracy, thereby eliminating an undesirable track offset attributable to tilting or eccentricity of the optical disc.
Inventors
- 👤 Seiji Yonezawa
- 👤 Masatoshi Ohtake
- 👤 Masaru Ito
- 👤 Toshiaki Tsuyoshi
- 👤 Kazuo Ichino
- 👤 Harushige Hachimanyama-Apartment 312 Nakagaki
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 18:16
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/2407; G11B7/24085; G11B7/08; G11B7/09; G11B7/094; G11B7/0948; G11B7/095; G11B7/0956; G11B7/0901; G11B7/0904
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
159 words
A tracking control method for a composite wobbled tracking servo system, comprising the steps of: preparing a rotary recording medium (10) having a first field (123) and a second field (122) alternately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) being provided at least in said second field, said first field including at least one pair of wobbled track marks (20-1, 20-2) disposed in a relation wobbled relative to the center of a track; irradiating the recording surface of said recording medium with a light spot (11); detecting a first tracking error signal (16) from the reflection of said light spot diffracted by said pregrooves (15) on said recording medium; detecting a second tracking error signal (24; 45) from the reflection of said light spot traversing said wobbled track marks; correcting said first tracking error signal on the basis of said second tracking error signal; and using the corrected signal for the tracking control.
Claim 2
Dependent Claim
159 words
A tracking control method for a composite wobbled tracking servo system, comprising the steps of: preparing a rotary recording medium (10) having a first field (123) and a second field (122) alternately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) being provided at least in said second field, said first field including at least one pair of wobbled track marks (20-1, 20-2) disposed in a relation wobbled relative to the center of a track; irradiating the recording surface of said recording medium with a light spot (11); detecting a first tracking error signal (16) from the reflection of said light spot diffracted by said pregrooves (15) on said recording medium; detecting a second tracking error signal (24; 45) from the reflection of said light spot traversing said wobbled track marks; correcting said first tracking error signal on the basis of said second tracking error signal; and using the corrected signal for the tracking control.
Claim 3
Dependent Claim
58 words
A method as claimed in Claim 1, wherein a dc offset of said first tracking error signal (16) is removed by a band-limited low-cut filter, and high frequency components of said second tracking error signal (24) are removed by a band-limited low-pass filter (28), said two different tracking error signals covering different frequency ranges of said servo system.
Claim 4
Dependent Claim
63 words
A method as claimed in Claim 1, wherein the gain of said second tracking error signal (24) in a low frequency range is selected to be larger than that of said first tracking error signal (16), and said second tracking error signal whose high frequency components are removed by a band-limited low-pass filter (28) is used to correct said first tracking error signal.
Claim 5
Dependent Claim
40 words
A method as claimed in Claim 1, wherein said light spot (11) is positioned on one of the center of said pregroove (15-1, 15-2) and the center of a land (15-3) between said pregrooves, under control of said corrected signal.
Claim 6
Dependent Claim
57 words
A method as claimed in Claim 1, wherein said wobbled track mark (20-1, 20-2) is recognized by pattern recognition means (35, 47),' and, only when the result of pattern recognition proves that said wobbled track mark is normal, said second tracking error signal (24) is delivered as an output signal of a sample and hold circuit (38).
Claim 7
Dependent Claim
76 words
A method as elaimed in Claim 5, wherein, when the result of pattern recognition proves that said wobbled track mark (20-1) is normal, said first tracking error signal (16) corrected by said second tracking error signal (24) is stored in a memory - (61), but, when the result of pattern recognition proves that said wobbled track mark (20-2) is abnormal, said corrected first tracking error signal stored in said memory is used for the tracking control.
Claim 8
Dependent Claim
204 words
A tracking control apparatus for a composite wobbled tracking servo system, comprising: a rotary recording medium (10) having a first field - (123) and a second field (122) altemately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) being provided at least in said second field, said first field including at least one pair of wobbled track marks (20-1, 20-2) disposed in a relation wobbled relative to the center of a track; irradiating means (4, 5, 9) for irradiating the recording surface of said recording medium with a light spot (11); first detecting means (25) for detecting a first tracking error signal (16) from the reflection of said light spot diffracted by said pregroove (15) on said recording medium; second detecting means (26, 27; 35, 36, 37, 38, 39) for detecting a second tracking error signal (24; 45) from the reflection of said light spot traversing said wobbled track marks; means (28, 32) for correcting said first tracking error signal on the basis of said second tracking error signal; and means (29; 27, 29) for driving tracking control means (7; 30) disposed in said irradiating means in response to the application of an output signal (33) of said correcting means.
Claim 9
Dependent Claim
204 words
A tracking control apparatus for a composite wobbled tracking servo system, comprising: a rotary recording medium (10) having a first field - (123) and a second field (122) altemately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) being provided at least in said second field, said first field including at least one pair of wobbled track marks (20-1, 20-2) disposed in a relation wobbled relative to the center of a track; irradiating means (4, 5, 9) for irradiating the recording surface of said recording medium with a light spot (11); first detecting means (25) for detecting a first tracking error signal (16) from the reflection of said light spot diffracted by said pregroove (15) on said recording medium; second detecting means (26, 27; 35, 36, 37, 38, 39) for detecting a second tracking error signal (24; 45) from the reflection of said light spot traversing said wobbled track marks; means (28, 32) for correcting said first tracking error signal on the basis of said second tracking error signal; and means (29; 27, 29) for driving tracking control means (7; 30) disposed in said irradiating means in response to the application of an output signal (33) of said correcting means.
Claim 10
Dependent Claim
37 words
An apparatus as claimed in Claim 7, wherein the detection sensitivity of said second-detecting means (26, 27; 35, 36, 37, 38, 39) in a low frequency range is higher than that of said first detecting means (25).
Claim 11
Dependent Claim
49 words
An apparatus as claimed in Claim 8, wherein said correcting means includes a low-pass fitter - (28) limiting the band of said second tracking error signal (24; 45) and adder means (32) for adding an output signal (31) of said low-pass filter to said first tracking error signal (16).
Claim 12
Dependent Claim
90 words
An apparatus as claimed in Claim 7, wherein said second detecting detects said second tracking error signal (45) on the basis of the relating intensity of the reflections of said light spot traversing said wobbled track marks respectively and includes third means (36) for generating con- trot pulse signals (42, 43) on the basis of said reflections, and fourth means (38) operative in response to said control pulse signals for sampling the signal indicative of the difference between the reflections of said light spot traversing said wobbled said sampled signal.
Claim 13
Dependent Claim
61 words
An apparatus as claimed in Claim 10, wherein said second detecting means further in- dudes fifth means (4 7 ) for recognizing the pattern of said wobbled track marks on the basis of the reflections of said light spot traversing said wobbled track marks, and generating an output signal (49) to control the sampling and holding operation of said fourth means.
Claim 14
Dependent Claim
69 words
An apparatus as claimed in Claim 11, further comprising memory means (61) for storing said corrected first tracking error signal, switching means (63) for switching over between the output signal of said memory means and the output signal of said fourth means, and means (56, 60) for generating a signal controlling the switching operation of said switching means on the basis of the output signal of said fifth means.
Claim 15
Dependent Claim
106 words
A rotary optical-information recording medium comprising a first field (123) and a second field (122) alternately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) disposed in at least said second field .and extending in thd direction of rotation of said disc while being spaced apart in the radial direction of said disc, and at least one pair of wobbled track marks (20-1, 20-2) previously disposed in said first field in a relation wobbled relative to the centerline extending in parallel to and between said pregrooves, whereby recording and reproduction of information can be done along said centerline extending between said pregrooves.
Claim 16
Dependent Claim
106 words
A rotary optical-information recording medium comprising a first field (123) and a second field (122) alternately arranged along the direction of rotation to provide a sector, pregrooves (15-1, 15-2) disposed in at least said second field .and extending in thd direction of rotation of said disc while being spaced apart in the radial direction of said disc, and at least one pair of wobbled track marks (20-1, 20-2) previously disposed in said first field in a relation wobbled relative to the centerline extending in parallel to and between said pregrooves, whereby recording and reproduction of information can be done along said centerline extending between said pregrooves.
Claim 17
Dependent Claim
31 words
A recording medium as claimed in Claim 13, wherein at least an address pit (14) for identifying said sector is previously formed along said centerline extending between said pregrooves (15-1, 15-2).
Claim 18
Dependent Claim
24 words
A recording medium as claimed in Claim 14, wherein said pregrooves (15-1, 15-2) extend to the area where said address pit (14) is formed.
Claim 19
Dependent Claim
26 words
A recording medium as claimed in Claim 14, wherein said wobbled track marks (20-1, 20-2) serve also as sactor marks indicating the head of said sector.
References Cited (Backward Citations)
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