Patent EP0550097A2 successfully refreshed from Google Patents.
EP0550097A2
Expired / Lapsed
EP
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Optical reading device and optical recording device
Assignee: Koninklijke Philips NV
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Filing: 1992-12-17
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Granted: —
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Expires: 2012-12-17
Abstract
Abstract An optical reading device for reading information recorded on a track (2) of an optical record carrier (1) is disclosed. A radiation source (10) generates a radiation beam (11) which is directed onto a radiation-sensitive detector (12) via the track (2). The radiation beam then produces a scanning spot (15) on the record carrier. The scanning spot (15) is displaced at a given scanning rate in the longitudinal direction of the track. A signal-regaining circuit (17) regains the recorded information on the basis of a detection signal (V1) supplied by the radiation-sensitive detector (12). A load circuit (18) loads the regained information into a output buffer memory (19) at a given load rate. A signal retrieval circuit (20) retrieves the information loaded into the output buffer memory (19) at a retrieval rate which is lower than the load rate. The storage of the regained information in the buffer memory is interrupted as soon as the filling level of the output buffer memory (19) has reached a given maximum filling level. As soon as the filling level approaches a given minimum value during the interruption, the scanning spot is displaced back to the track portion where the loading operation was interrupted. The storage of the regained signal is resumed at an instant when the scanning spot reaches a track position which corresponds to the position at which the loading of the buffer memory was interrupted. The radiation source (10) is switched off during time intervals in which the storage of regained information is interrupted.
Inventors
- 👤 Johannes Leopoldus Bakx
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 16:19
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B20/00; G11B20/10; G11B27/00; G11B27/005; G11B7/085; G11B2220/00; G11B2220/20; G11B2220/25; G11B2220/2525
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
255 words
An optical reading device for reading information recorded in a track of an optical disc carrier, which device comprises a radiation source for generating a radiation beam, an optical system for directing the radiation beam via the track onto a radiation-sensitive detector, the radiation beam producing a scanning spot on the record carrier, a driving device for displacing the scanning spot with respect to the disc carrier in a longitudinal direction of the track at a given scanning rate, a signal regaining circuit for regaining recorded information on the basis of a detection signal supplied by the radiation-sensitive detector, a load circuit for loading the regained information in an output buffer memory at a given load rate, a signal retrieval circuit for retrieving the information stored in the buffer memory at a given retrieval rate which is lower than the load rate, control means for interrupting the loading of the regained information in the buffer memory for displacing the scanning spot after a given time interval to the track portion where loading was interrupted and for subsequently resuming the storage of the regained signal at an instant when the scanning spot reaches a track position which corresponds to the position where the loading of the buffer memory was interrupted, such that a filling level of the buffer memory remains between given limits, characterized in that the device comprises means for switching off at least the radiation source in at least part of the time intervals in which the loading of the buffer memory is interrupted.
Claim 2
Dependent Claim
126 words
A device as claimed in Claim 1, characterized in that the device comprises focusing means for focusing the radiation beam, and a focus control for maintaining a focal point of the focused radiation beam in the plane of the track, said focus control comprising a focus actuator for displacing the focal point in a direction perpendicular to the record carrier, and a control circuit for applying a control signal dependent on a focus error signal to the focus actuator, the device comprising means for maintaining the control signal, during the time intervals when the radiation source is switched off, at a value which is substantially dual to the average value of the control signal in a time interval directly before the radiation source is switched off.
Claim 3
Dependent Claim
149 words
A device as claimed in Claim 2, characterized in that the focus control comprises means for deriving a focus error signal which is indicative of the focus error within a given measuring range of the focal point position, and in that the device comprises focus capturing means for bringing the focal point within the measuring range, said focus capturing means comprising means for reciprocating the focal point between two extreme values, a focus capturing detector for supplying a capturing detection signal indicating that the focal point is within the measuring range, and switching means for switching on the focus control in response to the capturing detection signal, the focus capturing means comprising means for reciprocating the focal point within a range of displacement surrounding a position which corresponds to the retained focus control signal, said range of displacement being smaller than the range fixed by the two extreme values.
Claim 4
Dependent Claim
119 words
A device as claimed in Claim 1, characterized in that the device comprises focusing means for focusing the radiation beam, and a focus control for maintaining a focal point of the focused radiation beam in the plane of the track, said focus control comprising a focus actuator for displacing the focal point in a direction perpendicular to the record carrier, and a control circuit for applying a control signal dependent on a focus error signal to the focus actuator, said focus control comprising means for taking samples of the focus error signal during time intervals when the loading of the buffer is interrupted, and switching means for temporarily switching on the radiation source while the samples are being taken.
Claim 5
Dependent Claim
48 words
A device as claimed in Claim 1, characterized in that the focus control has a first bandwidth when the buffer memory is being loaded, and a second bandwidth which is smaller than the first bandwidth in the time intervals in which the loading of the buffer is interrupted.
Claim 6
Dependent Claim
236 words
An optical recording device for recording information in a track of an optical record carrier, which device comprises write means for providing a information pattern in the track in response to a write signal, for which purpose the recording means comprise a radiation source for generating a radiation beam, an optical system for directing the radiation beam via the track onto a radiation-sensitive detector, the radiation beam producing a scanning spot on the record carrier, the device further comprising a driving device for displacing the scanning spot with respect to the record carrier in a longitudinal direction of the track at a given scanning rate, an input buffer memory for storing information to be recorded at a given load rate, a retrieval circuit for retrieving the information from the input buffer memory at a retrieval rate which is higher than the load rate, a control circuit for converting the retrieved information into the write signal, control means for interrupting the retrieval of the information from the input buffer memory for displacing the scanning spot after a given time interval to the track portion where the retrieval was interrupted and for subsequently resuming the retrieval of the information, such that a filling level of the input buffer memory remains between given limits, characterized in that the device comprises means for switching off the radiation source in time intervals in which the retrieval of the information is interrupted.
Claim 7
Dependent Claim
99 words
A device as claimed in Claim 6, characterized in that the device comprises focusing means for focusing the radiation beam, and a focus control for maintaining a focal point of the focused radiation beam in the plane of the track, said focus control comprising a focus actuator for displacing the focal point in a direction perpendicular to the record carrier, and a control circuit for applying a control signal dependent on a focus error signal to the focus actuator, the device comprising means for retaining the control signal during the time intervals when the radiation source is switched off.
Claim 8
Dependent Claim
149 words
A device as claimed in Claim 7, characterized in that the focus control comprises means for deriving a focus error signal which is indicative of the focus error within a given measuring range of the focal point position, and in that the device comprises focus capturing means for bringing the focal point within the measuring range, said focus capturing means comprising means for reciprocating the focal point between two extreme values, a focus capturing detector for supplying a capturing detection signal indicating that the focal point is within the measuring range, and switching means for switching on the focus control in response to the capturing detection signal, the focus capturing means comprising means for reciprocating the focal point within a range of displacement surrounding a position which corresponds to the retained focus control signal, said range of displacement being smaller than the range fixed by the two extreme values.
Claim 9
Dependent Claim
119 words
A device as claimed in Claim 6, characterized in that the device comprises focusing means for focusing the radiation beam, and a focus control for maintaining a focal point of the focused radiation beam in the plane of the track, said focus control comprising a focus actuator for displacing the focal point in a direction perpendicular to the record carrier, ad a control circuit for applying a control signal dependent on a focus error signal to the focus actuator, said focus control comprising means for taking samples of the focus error signal during time intervals when the loading of the buffer is interrupted, ad switching means for temporarily switching on the radiation source while the samples are being taken.
Claim 10
Dependent Claim
48 words
A device as claimed in Claim 9, characterized in that the focus control has a first bandwidth when the buffer memory is being loaded, and a second bandwidth which is smaller than the first bandwidth in the time intervals in which the loading of the buffer is interrupted.
References Cited (Backward Citations)
No citation records indexed.
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