Optical disk and optical disk drive device

Details Optical disk and optical disk drive device Optical disk and optical disk drive device

2000-05-30

2001-05-22

Neyzari, Ali (Department: 2651)

Dynamic information storage or retrieval

Storage medium structure

Optical track structure

C369S275400

Reexamination Certificate

active

06236637

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an optical disk in which information is recorded both on land and groove tracks.
The invention also relates to an optical disk drive device using such an optical disk.
More particularly, the invention relates to recognition patterns used for recognition of the header part provided in front of each information sector.
In conventional phase-change type optical disks, data is recorded only on grooves, and lands serve to guide the light spot for tracking, and to reduce crosstalk from adjacent groove tracks. If data is recorded on lands as well, the track density can be doubled on condition that the width of the grooves and the width of the lands are both unchanged. It has been discovered that the crosstalk between adjacent land and groove track is reduced if the difference in height between the lands and grooves is &lgr;/6 (&lgr; being the wavelength of the light source). Because of this discovery, the use of both land and groove tracks has become feasible. The use of both land and groove tracks is also advantageous with regard to the ease of mastering of the disk: it is easier to attain a certain recording density by the use of both land and groove tracks than by reducing the track pitch using only the groove tracks.
For instance, in the case of optical disks for use as computer data files, optical disks in which data is recorded both on land and groove tracks, and the tracks are concentric, so that after recording of one revolution (on a groove track, for example), a track jump is effected to start writing on the adjacent track (a land track). Sectors are managed in accordance with the sector addresses. Accordingly, the operation for recording and reproducing data, such as computer data, which need not be continuous, can be carried out without difficulty.
Rewritable optical disks are however also used for recording continuous data such as motion picture, or music. In multimedia applications (where computer data and video and audio data are mixed), spiral tracks, as in compact disks, may be preferred because of the continuity of the tracks.
In this case, the tracks need to be formed into a spiral form rather than a concentric form. However, in an optical disk in which the information is recorded both on lands and grooves and the tracks are spiral, it is necessary, after tracing the entire spiral formed of all the land tracks, for example, and groove tracks, to jump from the end of the land track spiral to the beginning of the groove track spiral. It Is then necessary to access from the inner periphery to the outer periphery of the disk. Such an operation Is time-consuming. In a disk which is divided into annular zones, the track jump is made from the inner periphery of the zone to the outer periphery of the zone, and the time for the jump is shortened but there is still a similar problem.
FIG.
23
A and
FIG. 23B
show details of the header region
4
in a conventional optical disk wherein data is recorded on both groove and land tracks.
FIG. 23A
shows the case where headers are provided separately for the land and groove tracks, and addresses dedicated to the respective tracks are formed.
FIG. 23B
shows the case where headers are provided on an extension of a boundary between land and groove tracks, and each address is shared by the land track and the groove track separated by the boundary. In either case, the headers include address pits.
The header portion is formed of embossments (dents or projections) physically formed for representing the address information and the like of the sector preceded by the header, the sector being a unit for recording data. Specifically, pits having the same height as the lands, or pits having the same depth as the grooves are formed in the header portion where no tracks are formed.
There are several methods for forming prepits suitable for the land/groove recording configuration. Two principal ones are those shown in FIG.
23
A and FIG.
23
B.
In the configuration shown in
FIG. 23A
, dedicated prepits are provided for each sector of the land or groove track. Because the dedicated prepits can record various items of information, such as the one indicating whether the sector following the dedicated prepits is in a land track or a groove track, control in the optical disk drive device is facilitated. However, the width of the prepits must be sufficiently narrower than the track width. This means that the laser beam used for forming the tracks cannot be used for forming the prepits, and the fabrication of the medium is difficult.
In the configuration shown in
FIG. 23B
, the prepits are shared by the land and groove tracks adjacent to each other. The prepits can be formed by using the same laser beam as that used for forming the tracks, and by shifting the laser beam by ½ of the track pitch laterally of the track, i.e., in the radial direction of the disk. However, during writing or reading of the disk, the shared prepits cannot indicate whether the sector following the prepits is in a land track or groove track, so that the optical disk drive device must have a means to find whether a land track or groove track is being traced by the light spot, and the control in the optical disk drive device is difficult.
In the above-described optical disk allowing recording and reproduction, it is also necessary to solve the problem of the track offset. This relates to the fact that the one beam-and-push-pull method is used for the tracking, rather than a three-beam method. This is because the recording requires a greater laser power. Also, in the case of pit-forming recording, such as the one on a write-once disk, the side spots (used in a three-beam method) causes a disturbance to the tracking operation.
In a push-pull tracking, the tracking error is detected using the diffraction distribution of the light spot illuminating the pregrooves as shown in
FIG. 24
, and fed to the servo system, so that offset may occur due to the eccentricity of the disk or tilting of the disk. More particularly, an optical head
10
has a laser diode
66
emitting a laser beam, which is passed through a half-mirror
65
and an objective lens
67
to illuminate an optical disk
8
rotated by a disk motor
9
. The reflected light beam from the light spot on the disk
8
is guided by the objective lens
67
and the half-mirror
65
and is received by a photodetector
11
, and the tracking error is detected using the diffraction distribution of the light spot on the optical disk
8
. The detected tracking error is used to control an actuator coil
64
for driving the objective lens
67
.
For instance, a tilt of 0.7 degrees or an eccentricity of a 100 &mgr;m (equivalent to lateral movement of the objective lens
62
of 100 &mgr;m as indicated by broken lines in
FIG. 24
) causes shifting of a light distribution
12
on the photodetector
11
, and hence an offset of 0.1 &mgr;.
To prevent such a phenomenon, a drive device having higher mechanical and optical accuracy is used, and various other contrivances are adopted.
FIG. 25A
shows the method of mirror surface correction in which a mirror surface part
7
is used.
FIG. 25B
shows the pit configuration of the optical disk used in combination with the wobble pits correction method.
In this method, wobble pit pits
68
and
69
being shifted in the radial direction of the disk by ½ of the track pitch are used. These methods are described in the following publications:
(1) Ohtake, et al. “Composite Wobbled Tracking in the Optical Disk System,” on pp. 181-188 in Optical Memory Symposium '85, held on Dec. 12-13 in 1985, published by Optical Industry Technology Promotion Association,
(2) Kaku, et al. on “Investigation of compensation method for track offset,” pp. 209-214 in Optical Memory Symposium '85, held on Dec. 12-13 in 1985, published by Optical Industry Technology Promotion Association.
FIG. 26
shows a track offset correction circuit used in combination with a disk having the mirror surface portion
7
shown in
FIG. 25A. A
split photodetect

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