EP0095852A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Focusing control circuitry for an optical memory system
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 n 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. 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
2026-11-06 09:42
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: 12
Claim 1
Independent Claim
147 words
In an optical data storage system including a recording medium, the combination comprising: means providing a radiation beam; 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.
Claim 2
Dependent Claim
147 words
In an optical data storage system including a recording medium, the combination comprising: means providing a radiation beam; 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.
Claim 3
Dependent Claim
14 words
The invention in accordance with claim 1, wherein said beam is a laser beam.
Claim 4
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 5
Dependent Claim
50 words
The invention in accordance with claim 3, wherein said focus error detecting means includes first and second photodetector elements for producing photodetector output signals indicative of the deviation of said focusing means from an in-focus condition, and means for combining said photodetector output signals to produce a focus error signal.
Claim 6
Dependent Claim
40 words
The invention in accordance with claim 4, 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 7
Dependent Claim
72 words
The invention in accordance with claim 4, 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 8
Dependent Claim
31 words
The invention in accordance with claim 6, 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 9
Dependent Claim
90 words
The invention in accordance with claim 3, 4, 5, 6 or 7, 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 10
Dependent Claim
15 words
The invention in accordance with claim 8, wherein said correction signal has a triangular waveform.
Claim 11
Dependent Claim
149 words
In an optical data storage system employing a recording medium and means including movable focusing means for directing and focusing a radiation beam on said medium, the 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; and 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.
Claim 12
Dependent Claim
149 words
In an optical data storage system employing a recording medium and means including movable focusing means for directing and focusing a radiation beam on said medium, the 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; and 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.
References Cited (Backward Citations)
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