Patent US20030194508A1 successfully refreshed from Google Patents.
EP0096969A1
Expired / Lapsed
EP
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Optical memory system having improved positioning and focusing control circuitry
Assignee: Unisys Corp
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Filing: 1983-05-17
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Granted: —
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Expires: 2003-05-17
Abstract
Abstract An optical storage system employing a laser beam which is directed and focused onto an optical disk for reading and/or writing data in a track of the disk. Positioning control is achieved by providing for track following and track seeking using a plurality of interactive servo-loops. Proper focusing is maintained using focusing control circuitry which produces a focus error signal that is applied to a focus motor. This focusing control circuitry is able to return the objective lens assembly to its in-focus position so long as the objective lens assembly remains within a predetermined capture range. In the event that the objective lens assembly is outside of this capture range, a waveform generator is enabled which produces a correction signal that causes the focus motor to move the objective lens assembly back within the capture range with a velocity and for a time period sufficient to permit the focusing control circuitry to regain control and return the objective lens assembly to its in-focus position.
Inventors
- 👤 Der-Chang Hsieh
- 👤 Edward V. Labudde
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 08:47
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/085; G11B7/08505; G11B7/08523; G11B7/09; G11B7/0901; G11B7/0908; G11B7/0946
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
277 words
In an optical data storage system including a recording medium having a large plurality of tracks containing stored data, the combination comprising: means providing a radiation beam for reading data recorded in a track; means including a movable focusing means for directing and focusing said beam on said medium; focus error detecting means for detecting a focusing error; focus error correction means responsive to the detection of a focus error by said focus error detection means for returning said focusing means to an in-focus condition so long as said focusing means remains within a predetermined capture range; out-of-range detecting means for detecting when said focusing means is outside of said capture range; and capture range return means responsive to the detection by said out-of-range detecting means that said focusing means is outside of said capture range for moving said focusing means back within said capture range whereby said focus error correction means is able to return said focusing means to an in-focus condition; means providing for relative movement of said radiation beam along said track; track following means for causing said beam to accurately follow a selected track on said medium; and track seeking means for moving said beam from a current track being followed to a new track, said track seeking means including short seek moving means and long seek moving means, said short seek moving means being operative to move said beam when the number of tracks to be moved is equal to or less than a predetermined value and said long seek moving means being operative to move said beam when the number of tracks to be moved is greater than said predetermined value.
Claim 2
Dependent Claim
277 words
In an optical data storage system including a recording medium having a large plurality of tracks containing stored data, the combination comprising: means providing a radiation beam for reading data recorded in a track; means including a movable focusing means for directing and focusing said beam on said medium; focus error detecting means for detecting a focusing error; focus error correction means responsive to the detection of a focus error by said focus error detection means for returning said focusing means to an in-focus condition so long as said focusing means remains within a predetermined capture range; out-of-range detecting means for detecting when said focusing means is outside of said capture range; and capture range return means responsive to the detection by said out-of-range detecting means that said focusing means is outside of said capture range for moving said focusing means back within said capture range whereby said focus error correction means is able to return said focusing means to an in-focus condition; means providing for relative movement of said radiation beam along said track; track following means for causing said beam to accurately follow a selected track on said medium; and track seeking means for moving said beam from a current track being followed to a new track, said track seeking means including short seek moving means and long seek moving means, said short seek moving means being operative to move said beam when the number of tracks to be moved is equal to or less than a predetermined value and said long seek moving means being operative to move said beam when the number of tracks to be moved is greater than said predetermined value.
Claim 3
Dependent Claim
14 words
The invention in accordance with claim 1, wherein said beam is a laser beam.
Claim 4
Dependent Claim
122 words
The invention in accordance with claim 1, wherein said track following means includes first position control means for causing said beam to accurately follow a selected track on said medium, wherein said short seek moving means is operative to temporarily disable the operation of said track following means during which time said first position control means is used for performing a short seek operation, and wherein said long seek moving means includes second position control means for moving said beam to a new track, said second position control means also being operable during operation of said track seeking means to move said first position control means in a direction which reduces the movement required thereby for maintaining said beam following said track.
Claim 5
Dependent Claim
23 words
The invention in accordance with claim 1 including means for disabling normal operations when said focusing means is outside of said capture range.
Claim 6
Dependent Claim
46 words
The invention in accordance with claim 1, wherein said focus error detecting means includes means for producing a focus error signal, and wherein said focus error correction means includes driving means responsive to said error signal for moving said movable focusing means towards an in-focus condition.
Claim 7
Dependent Claim
49 words
The invention in accordance with claim 5, wherein said focus error detecting means includes first and second photodetector elements for producing photodetector output signals indicative of the deviation of focusing means from an in-focus condition, and means for combining said photodetector output signals to produce a focus error signal.
Claim 8
Dependent Claim
40 words
The invention in accordance with claim 6, wherein said focus error correction means includes a non-linear amplifier responsive to said focus error signal for increasing the dynamic range of said focus error signal prior to application to said driving means.
Claim 9
Dependent Claim
72 words
The invention in accordance with claim 6, wherein said out-of-range detecting means includes means for combining said photodetector output signals to produce a focusing range signal indicative of the amount that said focusing means is removed from its in-focus position, and wherein said out-of-range detecting means also includes threshold means responsive to said focusing range signal for producing an out-of-range signal indicating when said focusing means is outside of said capture range.
Claim 10
Dependent Claim
31 words
The invention in accordance with claim 8, wherein the first-mentioned means for combining operates to subtract said photodetector outputs and the second-mentioned means for combining operates to add said photodetector outputs.
Claim 11
Dependent Claim
92 words
The invention in accordance with claim 3, 4, 5, 6, 7, 8 or 9, wherein said capture range return means includes waveform generating means responsive to the detection of an out-of-range condition by said out-of-range detecting means for applying a correction signal to said driving means, said correction signal being chosen so as to cause said driving means to move said focusing means back within said capture range with a velocity and for a time sufficient to permit said focus error correction means to return said focusing means to an in-focus condition.
Claim 12
Dependent Claim
15 words
The invention in accordance with claim 10, wherein said correction signal has a triangular waveform.
Claim 13
Dependent Claim
277 words
In a high density data storage system including a recording medium having a plurality of spaced tracks and providing a focused radiation beam on said medium for reading data stored in a track as said beam follows said track, an improved method of maintaining the focusing of said beam as well as providing for movement of said beam from one track to another track, said method comprising the steps of: detecting when said focusing means is not in an in-focus position and producing a focus error signal representative thereof; moving said focusing means in response to said focus error signal to return said focusing means to an in-focus position so long as said focusing means remains within a predetermined capture range; detecting when said focusing means is outside of said capture range; moving said focusing means back within said capture range in response to detecting that said focusing means is outside of said capture range for a sufficient time period and with a velocity chosen so that said focusing means is able to be returned to an in-focus position in response to said focus error signal; moving said beam in a controlled track following relationship with respect to a track on said medium; disabling said controlled track following relationship when said beam is to be moved to a different track; generating a signal of predetermined shape based on the number of tracks to be moved and the mechanical characteristics of the means provided for moving the beam; moving said beam in response to the generated signal; and enabling said controlled track following relationship after completion of said moving of said beam in response to the generated signal.
Claim 14
Dependent Claim
277 words
In a high density data storage system including a recording medium having a plurality of spaced tracks and providing a focused radiation beam on said medium for reading data stored in a track as said beam follows said track, an improved method of maintaining the focusing of said beam as well as providing for movement of said beam from one track to another track, said method comprising the steps of: detecting when said focusing means is not in an in-focus position and producing a focus error signal representative thereof; moving said focusing means in response to said focus error signal to return said focusing means to an in-focus position so long as said focusing means remains within a predetermined capture range; detecting when said focusing means is outside of said capture range; moving said focusing means back within said capture range in response to detecting that said focusing means is outside of said capture range for a sufficient time period and with a velocity chosen so that said focusing means is able to be returned to an in-focus position in response to said focus error signal; moving said beam in a controlled track following relationship with respect to a track on said medium; disabling said controlled track following relationship when said beam is to be moved to a different track; generating a signal of predetermined shape based on the number of tracks to be moved and the mechanical characteristics of the means provided for moving the beam; moving said beam in response to the generated signal; and enabling said controlled track following relationship after completion of said moving of said beam in response to the generated signal.
References Cited (Backward Citations)
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