Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-04-29
2001-09-18
Hindi, Nabil (Department: 2753)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S059200, C369S124060, C369S032010
Reexamination Certificate
active
06292449
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk apparatus having a plurality of heads (multi-heads) which can move independently in the radial direction of an optical disk.
2. Description of the Related Art
As a conventional optical disk apparatus of this type, there has been proposed an optical disk apparatus having a plurality of heads which can move independently in the radial direction of an optical disk as disclosed in Japanese Unexamined Patent Publication No. 3-260918 or No. 4-61050. With this configuration, since each of the plurality of heads can access a different track on the optical disk, both read and write operations, a plurality of write operations, and a plurality of read operations can be performed for one optical disk at the same time.
Methods for performing read and write operations while an optical disk is rotating include a constant angular velocity (CAV) method and a constant linear velocity (CLV) method. The above conventional optical disk apparatus handles a CAV-method disk. Since the linear velocity of a disk against each head differs unless the plurality of heads are disposed on the same track in the CLV method, signals read by the heads, which do not access at a constant linear velocity, have been compressed or expanded in the time domain. Therefore, the multi-head method cannot be applied to a CLV-method disk.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an optical disk apparatus that allows the multi-head method, in which a plurality of heads independently access different tracks on an optical disk, to be applied to a CLV-method disk.
The foregoing object of the present invention is achieved through the provision of an optical disk apparatus including: a first head capable of moving in the radial direction of an optical disk; a second head which can be moved in the radial direction of the optical disk independently from the first head and which performs at least reproduction for the optical disk; disk-rotating means for rotating the optical disk at a constant linear velocity against the first head; and time-axis expansion and compression means for expanding and compressing the time axis of a signal read by the second head, according to the track position of the second head such that the time axis matches that obtained at a constant linear velocity.
An optical disk apparatus according to the present invention is configured such that the time axis of a signal read by a head which does not access at a constant linear velocity is compressed or expanded according to the track position of the head so as to match the time axis obtained at a constant linear velocity. With this configuration, since a signal compressed or expanded in the time domain by reading by the head which does not access at a constant linear velocity is corrected, the multi-head method, in which each of a plurality of heads independently accesses a different track, can be applied to a CLV-method disk.
The optical disk apparatus may be configured such that the first head serves for recording only and the second head serves for reproduction only. Both of these first and second heads may serve for recording and reproduction. In this case, the time-axis expansion and compression means needs to expand and compress the time axis of a signal read by a head performing reproduction, according to the track position of the head such that the time axis matches that obtained at a constant linear velocity.
REFERENCES:
patent: 4972396 (1990-11-01), Rafner
patent: 5886967 (1999-03-01), Aramaki
patent: 5940352 (1999-08-01), Moriguchi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Hindi Nabil
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