EP0189932A2
Expired / Lapsed
EP
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Track servo system for controllably projecting an optical beam to an optical disk
Assignee: Fujitsu Ltd
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Filing: 1986-01-31
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Granted: —
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Expires: 2006-01-31
Abstract
Abstract An optical storage apparatus having an improved track servo means substantially eliminating "beam shift" effect of a laser beam (60) is disclosed. The track servo system comprises an objective lens (2) transferrable in a tracking direction (T) in parallel with the relevant rotating optical disk (1) and a tilting mirror (21) for deflecting the laser beam (60) for tracking. Tracking of the laser beam (60) is accomplished by controlling both of lens transfer (T) and mirror rotation in co-operation to center the laser beam (60) on the target track. Simultaneously, the laser beam (60) striking the disk (1) is controlled such that the laser beam (60) passes the back focal point (P o ) of the lens (2) locating at the opposite side to the disk (1) with respect to the lens (2), resulting in the elimination of "beam shift". The track servo system further comprises a skew detecting means (100), by which a skew signal is obtained and the laser beam (60) striking the disk (1) is controlled to pass the virtual back focal point (P') of the lens (2), eliminating the adverse effect of the skew of the disk (1) on the beam shift.
Inventors
- 👤 Shigeru Arai
- 👤 Toshitaka Iwamoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 19:29
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/095; G11B7/0956
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
312 words
An optical storage apparatus wherein information is stored on the surface of a rotatable optical disk (1), and said information is read out and or write in by scanning a track formed on said disk (1) with a first optical beam (60) which is controllably centered on said track by an optical track servo means (3; 22) driven by a track error signal generated in an optical track servo system, said optical track servo system comprising: a first photosensor (5; 26) comprising a plurality of sub-photosensors (A, B; A, B, C, D) for converting a part of said first optical beam (60) incident thereon into photoelectric currents for outputting a track error signal; an objective lens (2),being mounted movably in a plane substantially parallel with said optical disk (1), facing to said optical disk (1) for focusing said optical beam (60) onto said optical disk (1), and having a back focal point (P) at the opposite side to said optical disk (1) with respect to said objective lens (2); a lens actuating means (3) having a lens electromagnetic coil (32) for driving said objective lens (2) in said plane; a tilting mirror (21) for deflecting said first optical beam (60) for centering said first optical beam (60) on said track of said optical disk (1); a mirror actuating means (22) having a mirror electromagnetic coil (34) for driving said tilting mirror (21), characterized in that said optical track servo system further comprising an electrical control means for controllably driving said lens actuating means (3) and said mirror actuating means (22) in co-operation, during track servo operation, said first optical beam (60) being controllably directed by driving said tilting mirror (21) and said objective lens (2) in co-operation through said electrical control means such that said first optical beam (60) always passes said back focal point (P ) of said objective lens (2).
Claim 2
Dependent Claim
312 words
An optical storage apparatus wherein information is stored on the surface of a rotatable optical disk (1), and said information is read out and or write in by scanning a track formed on said disk (1) with a first optical beam (60) which is controllably centered on said track by an optical track servo means (3; 22) driven by a track error signal generated in an optical track servo system, said optical track servo system comprising: a first photosensor (5; 26) comprising a plurality of sub-photosensors (A, B; A, B, C, D) for converting a part of said first optical beam (60) incident thereon into photoelectric currents for outputting a track error signal; an objective lens (2),being mounted movably in a plane substantially parallel with said optical disk (1), facing to said optical disk (1) for focusing said optical beam (60) onto said optical disk (1), and having a back focal point (P) at the opposite side to said optical disk (1) with respect to said objective lens (2); a lens actuating means (3) having a lens electromagnetic coil (32) for driving said objective lens (2) in said plane; a tilting mirror (21) for deflecting said first optical beam (60) for centering said first optical beam (60) on said track of said optical disk (1); a mirror actuating means (22) having a mirror electromagnetic coil (34) for driving said tilting mirror (21), characterized in that said optical track servo system further comprising an electrical control means for controllably driving said lens actuating means (3) and said mirror actuating means (22) in co-operation, during track servo operation, said first optical beam (60) being controllably directed by driving said tilting mirror (21) and said objective lens (2) in co-operation through said electrical control means such that said first optical beam (60) always passes said back focal point (P ) of said objective lens (2).
Claim 3
Dependent Claim
152 words
An optical storage apparatus by claim 1, characterized in that said electrical control means controls said objective lens (2) by said lens actuating means (3) to transfer in tracking direction (T) by the distance B, and said tilting mirror (21) by said mirror actuating means (22) to rotate by an angle e in co-operation with aforesaid transfer of said objective lens (2) such that the relation between the transfer distance B of said objective lens (2) and said angle e of said tilting mirror (21) satisfies the following equation: whereby, ℓ denotes the distance between the center of said rotation of mirror (72) and back focal point (P ) of said lens (2) and the measuring origin of the transfer distance B and rotating angle e is the neutral position wherein said optical beam (60) is deflected by said tilting mirror (21) by 90 degree to proceed to said optical disk (1).
Claim 4
Dependent Claim
102 words
An optical storage apparatus according to claim 1 or 2, characterized in that an optical system for detecting the angle position of said tilting mirror (21) comprising: an optical source (27) for emitting a second optical beam (29); a reflecting surface formed on the surface of said tilting mirror (21); a photosensor (28) comprising a plurality of sub-photosensors on which said second optical beam (29) reflected by said reflecting surface falls, and thus generating photocurrents; and a comparing means for comparing said photocurrents generated in said sub-photosensors and outputting the differential currents as said angle position signal of said tilting mirror (21).
Claim 5
Dependent Claim
127 words
An optical storage apparatus according to one of the preceeding claims, characterized by a skew detecting means (100) for detecting a skew of said optical disk (1) and outputting a skew signal (P 3 ) of said optical disk (1), said skew detecting means comprising: an optical source (101) for emitting a third optical beam (105) which is directed to strike the surface of said optical disk (1); a photosensor comprising a plurality of sub-photosensors (102, 103) on which said third optical beam (105) reflected by said optical disk (1) falls, and thus generating photocurrents; and a comparing means (104) for comparing said photocurrents generated in said sub-photosensors (102, 103) and outputting the differential currents as said skew signal (P 3 ) of said optical disk (1).
References Cited (Backward Citations)
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