EP0225258A2
Expired / Lapsed
EP
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Focus servomechanism control system of optical disc system having offset setting means
Assignee: Fujitsu Ltd
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Filing: 1986-11-27
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Granted: —
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Expires: 2006-11-27
Abstract
Abstract A system for controlling a light focusing unit to adjust a focus of light impinging on a track in a rotatable optical disc (1). This control system includes a unit (27) for moving the light focusing unit (25) in a direction perpendicular to a plane of the optical disc (1); a unit (25, 24a, 23, 22, 29a, 29) for producing a focus error signal and a track error signal; and a unit (4) for controlling a position of the light focusing unit (25) through said moving unit (27) in response to the focus error signal and the offset parameter. The system further includes an offset setting unit for continuously setting, during an offset adjustment mode, a plurality of offset parameters to the position control unit (4), to determine a maximum amplitude of the track error signal, and to set the offset parameter producing the maximum amplitude of the track error signal to the position control unit (4). In a normal operation, the system effects the focus control in response to the set offset parameter and the focus error signal.
Inventors
- 👤 Akira Minami
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 16:43
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/085; G11B7/08505; G11B7/08517; G11B7/094; G11B7/0908; G11B7/0917; G11B2007/0919
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
222 words
A focus servomechanism control system in an optical disc system including a rotatable optical disc having at least one track storing data therein, a unit for focusing light for data write and read onto said track and a unit for sensing light reflected from said track, for controlling said light focusing unit to adjust a focus of said light on said track, comprising: means, operatively connected to said light focusing unit, for moving said light focusing unit in a direction perpendicular to a plane of said optical disc; means, operatively connected to said light sensing unit, for producing a focus error signal; means, operatively connected to said light sensing unit, for producing a track error signal; means, operatively connected to said focus error signal producing means and receiving an offset parameter, for controlling a position of said light focusing unit through said light focusing unit moving means in response to said focus error signal and said offset parameter; and means, operatively connected to said position control means and said track error signal producing means, during an offset adjustment mode, for continuously setting a plurality of offset parameters to said position control means, to determine a maximum amplitude of said track error signal, and to set the offset parameter producing said maximum amplitude of said track error signal to said position control means.
Claim 2
Dependent Claim
222 words
A focus servomechanism control system in an optical disc system including a rotatable optical disc having at least one track storing data therein, a unit for focusing light for data write and read onto said track and a unit for sensing light reflected from said track, for controlling said light focusing unit to adjust a focus of said light on said track, comprising: means, operatively connected to said light focusing unit, for moving said light focusing unit in a direction perpendicular to a plane of said optical disc; means, operatively connected to said light sensing unit, for producing a focus error signal; means, operatively connected to said light sensing unit, for producing a track error signal; means, operatively connected to said focus error signal producing means and receiving an offset parameter, for controlling a position of said light focusing unit through said light focusing unit moving means in response to said focus error signal and said offset parameter; and means, operatively connected to said position control means and said track error signal producing means, during an offset adjustment mode, for continuously setting a plurality of offset parameters to said position control means, to determine a maximum amplitude of said track error signal, and to set the offset parameter producing said maximum amplitude of said track error signal to said position control means.
Claim 3
Dependent Claim
123 words
A focus servomechanism control system according to claim 1, wherein said offset setting means comprises a processor; a largest amplitude detection circuit, operatively connected between said track error signal producing means and said processor, for detecting a largest amplitude of said track error signal and for sending said largest amplitude to said processor; and an offset outputting circuit, operatively connected between said position control means and said processor, for outputting the offset parameter from said processor to said position control means; said processor continuously outputting said plurality of said offset parameters, receiving said largest amplitude from said amplitude detection circuit for each offset parameter, determining a maximum amplitude from among said received largest amplitudes, and setting the offset parameter producing said maximum amplitude.
Claim 4
Dependent Claim
78 words
A focus servomechanism control system according to claim 2, wherein said amplitude detection circuit comprises a sample holder and an analog-to-digital (A/D) converter connected thereto, said processor outputting a sample hold signal to said sample holder in a short period shorter than a frequency of said tracking error signal to hold said tracking error signal for another short time sufficient for A/D conversion in said sample holder, said A/D converter operating in response to said sample hold signal.
Claim 5
Dependent Claim
28 words
A focus servomechanism control system according to claim 3, wherein said offset outputting circuit comprises a digital-to-analog (D/A) converter outputting an analog signal corresponding to the offset parameter.
Claim 6
Dependent Claim
78 words
A focus servomechanism control system according to claim 3, wherein said offset outputting circuit comprises a plurality of resistors and a plurality of switches selectively shorting said resistors to change a total resistance of said resistors, and said processor selectively energizing said switches in response to the offset parameter, said offset outputting circuit substantially changing a signal used for controlling the position of said light focusing unit in response to said offset parameter and said focus error signal.
Claim 7
Dependent Claim
57 words
A focus servomechanism control system according to claim 2, wherein said amplitude detection circuit comprises a peak holder and an analog-to-digital (A/D) converter connected thereto, said processor energizing said A/D converter before an output of a next offset parameter, receiving an A/D converted value in response to completion of an A/D conversion, and resetting said peak holder.
Claim 8
Dependent Claim
28 words
A focus servomechanism control system according to claim 6, wherein said offset outputting circuit comprises a digitalto-analog (D/A) converter outputting an analog signal corresponding to the offset parameter.
Claim 9
Dependent Claim
78 words
A focus servomechanism control system according to claim 6, wherein said offset outputting circuit comprises a plurality of resistors and a plurality of switches selectively shorting said resistors to change a total resistance of said resistors, and said processor selectively energizing said switches in response to the offset parameter, said offset outputting circuit substantially changing a signal used for controlling the position of said light focus unit in response to said offset parameter and said focus error signal.
Claim 10
Dependent Claim
73 words
A focus servomechanism control system according to claim 2, wherein said amplitude detection circuit comprises an envelope detection type amplitude detection circuit, an integrator integrating said detected signal at said amplitude detection circuit, and an analog-to-digital (A/D) converter connected to said integrator, said processor energizing said A/D converter before an output of a next offset parameter, receiving an A/D converted value in response to completion of an A/D conversion, and resetting said integrator.
Claim 11
Dependent Claim
28 words
A focus servomechanism control system according to claim 9, wherein said offset outputting circuit comprises a digital-to-analog (D/A) converter outputting an analog signal corresponding to the offset parameter.
Claim 12
Dependent Claim
78 words
A focus servomechanism control system according to claim 9, wherein said offset outputting circuit comprises a plurality of resistors and a plurality of switches selectively shorting said resistors to change a total resistance of said resistors, and said processor selectively energizing said switches in response to the offset parameter, said offset outputting circuit substantially changing a signal used for controlling the position of said light focus unit in response to said offset parameter and said focus error signal.
Claim 13
Dependent Claim
30 words
A focus servomechanism control system according to claim 1, wherein said offset setting means continuously sets said plurality of offset parameters in response to each rotation of said optical disc.
References Cited (Backward Citations)
No citation records indexed.
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