Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1998-10-27
2001-11-20
Hudspeth, David (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S044130, C369S116000
Reexamination Certificate
active
06320839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium, an optical information recording apparatus and an optical information recording method which may be applied to a magnetooptical disc (MO), a compact disc (CD, CD-ROM (compact disc-read-only memory)), a digital video disk (DVD) and a recording method and a recording apparatus of these discs, for example.
2. Description of the Related Art
Heretofore, a recording apparatus for a compact disc made of this kind of optical information recording medium processes recording data and then EFM (eight-to-fourteen modulation)-modulates the processed data to form a pit string having periods
3
T to
11
T with respect to a fundamental period T, thereby resulting in audio data or the like being recorded.
Corresponding thereto, a compact disc player receives a returned light of a laser beam reflected on the surface of a compact disc surface after having irradiated the laser beam on the surface of the compact disc and obtains a reproduced signal the signal level of which changes in response to a quantity of light of this returned light. Then, the compact disc player generates a binary signal by binarizing this reproduced signal with a predetermined slice level. Further, the compact disc player generates a reproducing clock by driving a PLL (phase-locked loop) circuit with this binary signal, and sequentially latches the binary signal by this reproducing clock, thereby resulting in reproduced data of the periods
3
T to
11
T corresponding to the pit string formed on the compact disc being generated.
The compact disc player decodes the reproduced data thus generated by the data processing corresponding to the data processing during the recording mode to reproduce audio data or the like recorded on the compact disc.
Recently, it has becomes customary that such compact disc are recorded at a high density and reproduced at a high transfer rate. In order to realize high-density recording and high-transfer rate reproduction, there has heretofore been used a land groove recording format in which pits are formed on both the lands and the grooves of the disc. According to the land groove recording format, a track pitch may be reduced, thereby making it possible to increase a disc recording capacity.
Also, according to the land groove recording format, when address information is recorded on the disc, the same address information is recorded on an adjacent land and a groove and one of two laser beams is wobbled in such a manner that data, that was recorded at the same address information, may be read out. A reproducing apparatus having a high transfer rate reproduces data at a high speed by rotating a compact disc, for example, at revolutions higher than 8 times a predetermined revolution number. Such high-transfer rate reproducing apparatus is able to reproduce data of the same amount in quite a short period of time as compared with the normal one time.
As shown in
FIG. 1
, when a disc is manufactured, the groove is cut by using spots
201
,
202
of two laser beams. When one of the two laser beam is wobbled, a distance between the two laser beams and the laser powers of the two laser beams have to be adjusted with high accuracy in such a manner that the spot
202
of the wobbled laser beams may not invade the spot
201
of the other laser beam which is not wobbled. To this end, the sizes of the laser beams for use in cutting should be calculated from the distance between the two laser beams relative to the determined groove width. However, as shown in
FIG. 2
, two laser beams
205
(LA
0
, LB
0
) have beam intensity distributions (SA
0
, SB
0
, added distribution S
0
), and hence widths (WA
0
to WB
0
) of the groove
203
are determined by a combination of the beam intensity distributions and disc exposure conditions such as an exposure threshold
206
(TH) in a disc cutting direction
204
. Even though the adjusted beam distance and light intensity are calculated by the above-mentioned factors, when address information is recorded on the groove by wobbling one of the two laser beams, the light intensity of one laser beam is added to the other laser beam, which is not wobbled, by the wobbled amount so that the groove, which should not be modulated by the other laser beam, is modulated by the influence of the offset. As a consequence, upon reproduction, the offset signal is superimposed upon the reproduced signal. There is then the disadvantage that address information cannot be reproduced at a high accuracy.
SUMMARY OF THE INVENTION
In view of the aforesaid aspect, it is an object of the present invention to provide an optical information recording medium, an optical information recording method and an optical information recording apparatus in which the other laser beam may be protected from being affected by an offset of one laser beam and a signal may be stably decoded upon high-density recording.
According to an aspect of the present invention, there is provided an optical information recording apparatus for forming a groove whose one side is wobbled or is formed on an optical recording medium by turning on or off one of two laser beams in accordance with a modulation signal. This optical information recording apparatus comprises a device for wobbling the one laser beam controlled on or off in such a manner that the one laser beam may not affect the other laser beam.
According to another aspect of the present invention, there is provided an optical information recording method in which a groove whose one side is wobbled or modulated is sequentially formed on an optical recording medium by turning on or off one of two laser beams in accordance with a modulation signal and desired data is recorded by the groove. This optical information recording method is characterized in that the one laser beam controlled on or off is wobbled in such a manner that the controlled one laser beam may not affect the other laser beam.
In accordance with a further aspect of the present invention, there is provided an optical information recording medium in which a groove whose one side is wobbled or modulated is sequentially formed on an optical recording medium by turning on or off one of two laser beams in accordance with a modulation signal and desired data is recorded by the groove. This optical information recording medium is characterized in that a groove is formed by wobbling the one laser beam controlled on or off in such a manner that the one laser beam may not affect the other laser beam.
The optical information recording apparatus of the present invention acts as follows.
In the optical information recording apparatus, when one side of groove is wobbled by one laser beam in accordance with a modulation signal, the one laser beam acts in such a manner that a light intensity of the one laser beam is not added to a light intensity of the other laser beam of the other side, which is not wobbled, by a wobbled amount. Thus, the other side of the groove which should not be modulated inherently may be protected from being affected by the offset. Also, one side of the groove is wobbled by one laser beam of two laser beams, whereby adjacent land and groove may have a shared address.
The optical information recording method according to the present invention acts as follows.
In the optical information recording method, when one side of groove is wobbled by one laser beam in accordance with a modulation signal, the one laser beam acts in such a manner that a light intensity of the one laser beam is not added to a light intensity of the other laser beam on the other side of groove, which is not wobbled, by a wobbled amount. Thus, the groove of the other side which should not be modulated may be protected from being affected by the offset. Also, one side of two laser beams is wobbled, whereby adjacent land and groove may form a shared address. Thus, a redundancy in information recording may be lowered.
The optical information recording medium according to the present invention acts as follows.
Fujita Goro
Imanishi Shingo
Tobita Minoru
Chu Kim-Kwok
Hudspeth David
Sonnenschein Nath & Rosenthal
Sony Corporation
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