Patent EP0349439A2 successfully refreshed from Google Patents.
EP0349439A2
Expired / Lapsed
EP
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System for obtaining optimum focusing position in optical disc system
Assignee: Panasonic Holdings Corp
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Filing: 1989-06-29
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Granted: —
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Expires: 2009-06-29
Abstract
Abstract A system for obtaining an optimum focusing position in an optical disc system, wherein an optical beam is impinged onto a track of an optical disc (1), and a reflection signal having information of an intensity of a optical beam reflected by an optical disc (1), is obtained. A predetermined frequency component (DRF1), which component is generated in a reflecting signal (SVa, SVb, SVc, SVd) by a modulation caused by an existence of a pit on a track of the optical disc (1), is extracted from the reflection signal (SVa, SVb, SVc, SVd), and then a focus position wherein a maximum intensity of the above extracted component is obtained, is searched by changing the focus position of the optical beam. Further, the above system is incorporated in a focus servo control system for maintaining an optimum focusing position in an optical disc system during reading and writing operations, to determine an optimum offset value (VF) which is to be adjusted to compensate an error arisen from a construction of the focus servo control system, during an offset adjusting operation.
Inventors
- 👤 Shigenori Yanagi
- 👤 Akira Minami
- 👤 Masateru Sasaki
- 👤 Shigeru Arai
- 👤 Toshitaka Iwamoto
- 👤 Hidenori Saitoh
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 17:13
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/094; G11B7/0945; G11B7/0908
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
162 words
A system for obtaining an optimum focusing position in an optical disc system, comprising: an optical beam impinging means (20, 21a, 22, 24a, 25) for impinging an optical beam on a track of an optical disc; a reflection signal obtaining means (22, 24a, 25, 21b, 28) for obtaining a reflection signal (SVa, SVb, SVc, SVd) having information of an intensity of an optical beam reflected bv an optical disc (1); a filtering means (51) for extracting a predetermined frequency component (DRF1) from said reflection signal (SVa, SVb, SVc, SVd), which component is generated in a reflecting signal by a modulation caused by an existence of a pit on a track of said optical disc (1); a focus position changing means (27) for changing said focus position of said optical beam; and an optimum focusing position searching means for searching for a focus position wherein a maximum intensity of the output of said filtering means (51) is obtained by scanning said focusing position.
Claim 2
Independent Claim
162 words
A system for obtaining an optimum focusing position in an optical disc system, comprising: an optical beam impinging means (20, 21a, 22, 24a, 25) for impinging an optical beam on a track of an optical disc; a reflection signal obtaining means (22, 24a, 25, 21b, 28) for obtaining a reflection signal (SVa, SVb, SVc, SVd) having information of an intensity of an optical beam reflected bv an optical disc (1); a filtering means (51) for extracting a predetermined frequency component (DRF1) from said reflection signal (SVa, SVb, SVc, SVd), which component is generated in a reflecting signal by a modulation caused by an existence of a pit on a track of said optical disc (1); a focus position changing means (27) for changing said focus position of said optical beam; and an optimum focusing position searching means for searching for a focus position wherein a maximum intensity of the output of said filtering means (51) is obtained by scanning said focusing position.
Claim 3
Dependent Claim
15 words
A system according to claim 1, wherein said filtering means comprises a differentiating means (51).
Claim 4
Dependent Claim
27 words
A system according to claim 1, wherein said optimum focusing position searching means comprises: an enveloping means (52) for obtaining the output of said filtering means (51).
Claim 5
Dependent Claim
30 words
A system according to claim 3, wherein said optimum focusing position searching means further comprises: a sampling means (53, 54, 55) for sampling the output of said enveloping means (52).
Claim 6
Dependent Claim
39 words
A system according to claim 5, wherein said sampling means (53, 54, 55) carries out said sampling at a portion on a track where a common predetermined pattern (VFO) is written, for all focusing positions in said scanning operation.
Claim 7
Dependent Claim
40 words
A system according to claim 1, further comprising a track servo control means (3) for maintaining a position of the surface of said optical disc (1) where said optical beam is impinging onto, in an optimum position on a track.
Claim 8
Dependent Claim
15 words
A system according to claim 6, wherein said filtering means comprises a differentiating means (51).
Claim 9
Dependent Claim
27 words
A system according to claim 6, wherein said optimum focusing position searching means comprises: an enveloping means (52) for obtaining the output of said filtering means (51).
Claim 10
Dependent Claim
30 words
A system according to claim 8, wherein said optimum focusing position searching means further comprises: a sampling means (53, 54, 55) for sampling the output of said enveloping means (52).
Claim 11
Dependent Claim
39 words
A system according to claim 9, wherein said sampling means (53, 54, 55) carries out said sampling at a portion on a track where a common predetermined pattern (VFO) is written, for all focusing positions in said scanning operation.
Claim 12
Dependent Claim
219 words
A focus servo control system for maintaining an optimum focusing position in an optical disc system during reading and writing operations, comprising: an optical beam impinging means (20, 21a, 22, 24a, 25) for impinging an optical beam on a track of an optical disc; a reflection signal obtaining means (22, 24a, 25, 21b, 28) for obtaining a reflection signal (SVa, SVb, SVc, SVd) having information of an intensity of an optical beam reflected by an optical disc (1); a focus position changing means (27) for changing said focusing position of an optical system; a servo control means (4) for controlling said focus position changing means (27) according to said reflection signal; an offset adjusting means (46) for adjusting an offset (VF) which is used to compensate an error arising from a construction of said focus servo control system; a filtering means (51) for extracting a frequency component (DRF1) from said reflection signal (SVa, SVb, SVc, SVd), which component is generated in a reflecting signal by a modulation caused by a pit located on a track of said optical disc; and an optimum offset value obtaining means for obtaining an optimum value of said offset (VF) whereby a maximum intensity of the output of said filtering means (51) is obtained by scanning said offset (VF), during an offset adjusting operation.
Claim 13
Dependent Claim
219 words
A focus servo control system for maintaining an optimum focusing position in an optical disc system during reading and writing operations, comprising: an optical beam impinging means (20, 21a, 22, 24a, 25) for impinging an optical beam on a track of an optical disc; a reflection signal obtaining means (22, 24a, 25, 21b, 28) for obtaining a reflection signal (SVa, SVb, SVc, SVd) having information of an intensity of an optical beam reflected by an optical disc (1); a focus position changing means (27) for changing said focusing position of an optical system; a servo control means (4) for controlling said focus position changing means (27) according to said reflection signal; an offset adjusting means (46) for adjusting an offset (VF) which is used to compensate an error arising from a construction of said focus servo control system; a filtering means (51) for extracting a frequency component (DRF1) from said reflection signal (SVa, SVb, SVc, SVd), which component is generated in a reflecting signal by a modulation caused by a pit located on a track of said optical disc; and an optimum offset value obtaining means for obtaining an optimum value of said offset (VF) whereby a maximum intensity of the output of said filtering means (51) is obtained by scanning said offset (VF), during an offset adjusting operation.
Claim 14
Dependent Claim
15 words
A system according to claim 11, wherein said filtering means comprises a differentiating means (51).
Claim 15
Dependent Claim
27 words
A system according to claim 11, wherein said optimum offset value obtaining means comprises: an enveloping means (52) for obtaining the output of said filtering means (51).
Claim 16
Dependent Claim
28 words
A system according to claim 13, wherein said optimum offset value obtaining means further comprises: a sampling means (52) for sampling the output of said enveloping means (52).
Claim 17
Dependent Claim
40 words
A system according to claim 14, wherein said sampling means (53, 54, 55) carries out said sampling at a portion on a track where a common predetermined pattern (VFO) is written, for all offset values used in said scanning operation.
Claim 18
Dependent Claim
39 words
A system according to claim 11, further comprising a track servo control means (3) for maintaining a position of the surface of said optical disc where said optical beam is impinging onto, in an optimum position on a track.
Claim 19
Dependent Claim
15 words
A system according to claim 16, wherein said filtering means comprises a differentiating means (51).
Claim 20
Dependent Claim
27 words
A system according to claim 16, wherein said optimum offset value obtaining means comprises: an enveloping means (52) for obtaining the output of said filtering means (51).
Claim 21
Dependent Claim
30 words
A system according to claim 18, wherein said optimum offset value obtaining means further comprises: a sampling means (53, 54, 55) for sampling the output of said enveloping means (52).
Claim 22
Dependent Claim
40 words
A system according to claim 19, wherein said sampling means (53, 54, 55) carries out said sampling at a portion on a track where a common predetermined pattern (VFO) is written, for all offset values used in said scanning operation.
References Cited (Backward Citations)
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