Optical disk and optical disk apparatus

Details Optical disk and optical disk apparatus Optical disk and optical disk apparatus

2000-04-26

2004-06-15

Edun, Muhammad (Department: 2653)

Dynamic information storage or retrieval

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

Control of information signal processing channel

C369S044130, C369S053410, C369S275100

Reexamination Certificate

active

06751173

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical disk having lands and grooves both used as data recording tracks and an optical disk apparatus for recording/reproducing information into/from such an optical disk.
BACKGROUND OF THE INVENTION
optical disks, such as magneto-optical disks and phase-change disks, have been known. More precisely, ROM (Read Only Memory) disks used exclusively for reading out data, WORM (write-once, read-many-times) disks, RAM (Random Access Memory) disks used for recording and reproducing data, and so-called partial ROM disks having both a ROM area and a RAM area have been known. The diameters of these disks are: 130 mm and 90 mm for MOs (Magneto Opticals) used in computers; 120 mm and 80 mm for CDs (Compact Discs) and DVDs (Digital Versatile Discs); and 64 mm for MDs (Mini Discs). These optical disks were originally arranged in such a manner that data is recorded into either lands or grooves which are preformed on the disks. However, to meet an increasing volume of recording data in recent years, a so-called land and groove recording technique has been proposed, by which data is recorded in both the lands and grooves. In order to increase a recording density by the land and groove recording technique, a highly reliable clock mark is necessary, so that a clock can be reproduced without depending on the quality of the recording data. Also, as to the structure of the sectors formed on the disk serving as the minimum recording units, such that sector address information can be obtained from the lands and grooves separately has to be given.
Accordingly, Japanese Laid-open Patent Application No. 16216/1999 (Japanese Official Gazette, Tokukaihei No. 11-16216, publishing date: Jan. 22, 1999) discloses a segment structure such that provides {circumflex over (1)} a high-quality clock mark in the land and groove recording technique, and {circumflex over (2)} a one-side wobbling address such that realizes sharing of address information by the lands and grooves.
FIG. 10
is a schematic view showing a disk format proposed by the technique disclosed in the foregoing publication. As shown by (A) in
FIG. 10
, a one-round track used in recording/reproducing data is composed of a plurality of frames denoted as (FRM
0
) to (FRM n). As shown by (B) in
FIG. 10
, each frame is composed of an address segment (ASG) and a total of 46 data segments (DSG
0
) to (DSG
45
). As shown by (C) in
FIG. 10
, the address segment (ASG) is composed of: a preamble (PRA) used for clock phase adjustment when reproducing address; a synchronous signal (SYNC) indicating the start of address information; a frame address (FA) as address information in the disk's tangential line direction (i.e., a direction along which the recording track extends); a track address (TA) as address information in the radius direction of the disk; an error detecting code (CRC: Cyclic Redundancy Check Code) used for detecting an error in reproduced address information; and a postamble (POA).
Shown by (D) in
FIG. 10
is a land/groove format on the disk. More precisely, in an address segment
100
, each of grooves (n) and (n+1) is wobbled at their respective walls at one side to record the address information shown by (C) in FIG.
10
. An address used in this one-side wobbling address represents address information shared by a particular groove and a land adjacent to this particular groove. In other words, a pair of the groove (n) and a land (n) adjacent to the same shares the address information, and so does a pair of the groove (n+1) and a land (n+1) adjacent to the same. Thus, a single address segment can be used as a common address area for the land and groove. This offers a significant effect that redundancy caused when assembling address information can be reduced. The foregoing address information can be detected by a radial push-pull signal.
On the other hand, a data segment
101
is composed of so-called straight grooves and lands each sandwiched by non-wobbled two walls.
With any of the foregoing optical disks, the data area and address area are spaced apart from each other so as to prevent interference between these areas, thereby making it possible to reproduce high-quality signals.
A clock mark
102
is appended at the head of each of the address segment
100
and data segment
101
. The clock marks
102
are convex marks on the grooves and concave marks on the lands, and aligned along the disk's tangential line direction at regular intervals and radially in the radius direction of the disk (that is, along the radius direction of the disk). By this arrangement, the clock marks can be detected with a tangential push-pull signal from both the lands and grooves. Consequently, a clock can be generated in a stable manner without being affected adversely by a tracking offset or a tilt in the radius direction of the disk. A clock generated from this clock mark responds to an error in the number of rotations of the disk and a change in linear velocity caused by decentering. Thus, if this clock is used as a reference clock when recording/reproducing data, data can be recorded/reproduced into/from the disk at an absolute position with high accuracy.
The foregoing one-side wall wobbling address of the optical disk offers an effect that the address information can be shared by the lands and grooves, but it also has a problem that the quality of an address signal is deteriorated by a tilt in the radius direction of the disk, namely, a radial tilt.
FIG. 11
is a graph showing a change in an address signal amplitude (radial push-pull signal) versus a quantity of the radial tilt. In the graph, a solid line represents a rated amplitude of the address signal, and a broken line represents a quantity of crosstalk between the address signal and an adjacent track. The amplitude of the address signal reaches its maximum when the radial tilt position shifts to the minus side from the center of the radial tilt (0° tilt), and the amplitude of the address signal keeps decreasing as the radial tilt position shifts to the plus side. On the other hand, the crosstalk between the address signal and the adjacent track keeps increasing as the radial tilt position shifts to the plus side. Hence, the plus side of the radial tilt becomes weak in this case (that is, the quality of the address signal is deteriorated markedly). Also, the radial tilt polarity that deteriorates the quality of the address signal reverses when the wobbling on the groove wall is switched from the inner side to the outer side of the disk and vice versa, and between the grooves and lands. In order to eliminate this inconvenience, an ASMO format (Advanced Storage—Magneto Optical Disk, April, 1998) adopts a technique, by which the one-side wobbling address for one address segment is divided by two (first address portion and second address portion). To be more specific, according to the above technique, the first address portion is provided as the one-side wobble at the inner side of the disk, and the second address portion is provided as the one-side wobble at the outer side of the disk, so that a larger radial tilt margin will be given.
The optical disks are advantageous over conventional tapes of recording media in that (1) an access time is far shorter and (2) a large volume of data can be recorded/reproduced without physical contact to the recording media. Thus, while the optical disks are used as an install type external storage device for a personal computer, expectations are also rising that the optical disks can realize an apparatus for recording/reproducing digital motion images of a larger volume or a compact portable device.
However, applying the land and groove recording technique which can realize a large volume recording to a disk having a small diameter causes the following problems.
That is, the foregoing disk format is suitable to a 120-mm disk, and a recording/reproducing area extends from 24 mm to 58 mm along the radius of the disk as does in the DVD, and approximately 1200 segments (clock marks) are

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