Optical disk unit

Details Optical disk unit Optical disk unit

2001-05-24

2003-05-13

Edun, Muhammad (Department: 2655)

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

C369S053100, C369S059100, C369S116000

Reexamination Certificate

active

06563775

ABSTRACT:

BACKGROUND OF THE INVENTION
This application claims the benefit of a Japanese Patent Application No. 2000-161357 filed May 31, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to optical disk units, and more particularly to an optical disk unit which uses a writable (recordable) or rewritable optical disk.
2. Description of the Related Art
Generally, in an optical disk called a compact disk (CD), a spiral track is formed at a constant liner density from an inner periphery to an outer periphery of the disk. In addition, information can be recorded in a CD called a CD-Recordable (CD-R). When recording the information on the CD-R, the information is also recorded at a constant linear density on a spiral track which is formed from the inner periphery to the outer periphery of the CD-R. Information is similarly recorded on a CD called a CD-Rewritable (CD-RW), that is, at a constant linear density on a spiral track which is formed from the inner periphery to the outer periphery of the CD-RW. The information is rewritable in the case of the CD-RW.
Recording and reproducing systems used to record information on and reproduce information from the optical disks such as the CD-R and the CD-RW can generally by categorized into a constant linear velocity (CLV) system and a constant angular velocity (CAV) system. There is also a recording and reproducing system called a zone constant linear velocity (ZCLV) system which is a modification of the CLV system. For example, such recording and reproducing systems are proposed in Japanese Laid-Open Patent Applications No. 11-296858, 2000-11384, No. 2000-48484, No. 7-21585, No. 9-231580, No. 9-270129, No. 10-79124, and No. 11-66726.
According to the CLV system, the optical disk is rotated at a constant linear velocity. Hence, although data management and rotational velocity control become slightly complex, it is possible to maximize a recording capacity by the CLV system. On the other hand, according to the CAV system, the optical disk is rotated at a constant angular velocity, that is, at a constant number of revolutions. For this reason, the data management and the rotational velocity control become simple, but the recording capacity is slightly sacrificed according to the CAV system. According to the ZCLV system, a recording surface of the optical disk is divided into a plurality of zones, and the linear velocity is maintained constant within each of the zones, similarly to the CLV system. The ZCLV system changes the rotational velocity for each zone so that the rotational velocity increases towards the outer periphery of the optical disk.
When recording information on the recordable or rewritable optical disks such as the CD-R and the CD-RW, the CAV system or the ZCLV system is employed by placing priority on the ease of the rotation control of the optical disk. Particularly, the CAV system is desirable in order to satisfy the recent demands to improve the recording velocity (rate) and realize a recording such as a 20-times speed recording.
However, when the optical disk in conformance with the CLV system, such as the CD-R and the CD-RW, is rotated according to the CAV system, the linear velocity increases as a radial position on the optical disk moves towards the outer periphery of the optical disk. But since an optimum recording laser power increases proportionally to the linear velocity, it is not possible to record the information at an optimum recording power in an outer peripheral portion of the optical disk if the recording power is maintained constant.
In addition, a setting of a write strategy (light emission waveform of a semiconductor laser) shown in
FIG. 1
with respect to the CD-R does not lead to an ideal recording mark on the optical disk as shown in
FIG. 2A
when a high-speed write is carried out. Instead, the actual recording mark on the optical disk typically becomes as shown in
FIG. 2B
when the high-speed write is carried out. In
FIG. 2B
, a portion {circle around (
1
)} corresponds to a shape which is formed due to insufficient heat transfer to the optical disk immediately after the irradiation of the laser beam on the optical disk starts, and a portion {circle around (
2
)} corresponds to a shape which is formed due to insufficient heat release immediately after the irradiation of the laser beam on the optical disk ends.
Accordingly, as shown in
FIG. 1
, with respect to a recording clock period T at each linear velocity, the laser power at a leading portion of a recording pulse is set larger than at a trailing portion of the recording pulse, in a form of an extra pulse, and a recording pulse width is set narrower than the actual width which is to be written. With regard to the recording clock period T, 1T denotes a 1 times-speed reproduction of 1.2 to 1.4 m/s, for example, and amounts to 231.4 ns. Such a modification of the write strategy is mainly made by changing a value &thgr;
1
which prescribes the recording pulse width n−&thgr;
1
T indicated by {circle around (
1
)} in FIG.
1
, and/or changing a power &Dgr;P of the extra pulse indicated by {circle around (
4
)} in
FIG. 1
, where n denotes an integer from 2 to 11 of an EFM signal. In
FIG. 1
, a portion {circle around (
2
)} corresponds to a pulse width &agr;T, and a portion {circle around (
3
)} corresponds to a recording power Pw.
In addition,
FIG. 3
shows a write strategy with respect to the CD-RW using multi-recording pulses. In the case of the recent high-speed write with respect to the optical disk, a peak pulse width at a leading portion of the multi-recording pulses is set wide with respect to the recording clock period T for each linear velocity, so as to facilitate heat transfer to the optical disk immediately after the irradiation of the laser beam on the optical disk starts. Moreover, an OFF-pulse width at a last portion of the multi-recording pulses is set narrow so as to adjust the remaining heat effect. In order to form an ideal recording mark on the optical disk, such a modification of the write strategy is mainly made by changing a peak pulse width &thgr;
2
at a portion {circle around (
1
)} shown in
FIG. 3
, and/or changing an OFF-pulse width xn at a portion {circle around (
2
)} shown in FIG.
3
. In
FIG. 3
, a portion {circle around (
3
)} corresponds to an intermediate pulse width.
In any case, the setting of the write strategy is changed for each recording linear velocity. For this reason, in the case of the CD-R, there is a problem in that the recording cannot be made under an optimum recording condition if the value &thgr;
1
which prescribes the recording pulse width n−&thgr;
1
T and the power &Dgr;P of the extra pulse remain constant. In the case of the CD-RW, there is a problem in that the recording cannot be made under an optimum recording condition if the peak pulse width &thgr;
2
and the OFF-pulse width xn remain constant.
Such problems similarly occur when rotating the optical disk, such as the CD-R and the CD-RW, according to the ZCLV system.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful optical disk unit in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide an optical disk unit which can always record information with respect to a recordable or rewritable optical disk at an optimum recording condition, using the CAV system or the ZCLV system which can improve the recording velocity as compared to the CLV system.
Still another object of the present invention is to provide an optical disk unit which can cope with a case where an optical disk used has a low recording sensitivity and/or a case where a light source used has a low maximum power output.
A further object of the present invention is to provide an optical disk unit which can cope with a case where optical disks used are manufactured by different manufacturers.
Another object of the present invention is

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