DISK RECORDING MEDIUM INCLUDING DATA...

Details DISK RECORDING MEDIUM INCLUDING DATA... DISK RECORDING MEDIUM INCLUDING DATA...

2000-12-27

2002-11-26

Psitos, Aristotelis (Department: 2653)

Dynamic information storage or retrieval

Information location or remote operator actuated control

Selective addressing of storage medium

C369S275300

Reexamination Certificate

active

06487144

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disk recording media such as magneto-optical disks, and disk drive units that perform writing or reading operations adapted for the media.
2. Description of the Related Art
Recently, an increase in the density of recording media has been required, and various technologies for high-density writing and reading have been developed.
For example, magneto-optical (“MO”) disks have been used mainly for writing and reading computer data. As techniques for enabling high density recording on the magneto-optical disks, the magnetically induced super resolution (MSR) technique and the land/groove writing method have been developed.
In the land/groove writing method, both a land and a groove are used as recording tracks.
On a conventional magneto-optical disk, grooves are formed beforehand, and the grooves are used as recording tracks. By also using, as a recording track, the area or the land between one groove recording track and an adjacent groove recording track, the recording density of the disk can be greatly increased.
In the MSR technique, magnetic films having different temperature characteristics are used to read information recorded in a region smaller than the laser spot. Accordingly, from a medium (MSR medium) having recording regions composed of two magnetic films having different temperature characteristics, information written at a high density can be read without reducing the diameter of the laser spot.
The MSR reading method is described below with reference to FIG.
18
.
The top portion (a) of
FIG. 18
shows a recording track Dt of a magneto-optical disk on which write marks M are formed, and a laser spot SP impinging on the track Dt. The bottom portion (b) of
FIG. 18
shows a partial cross section of the magneto-optical disk.
To obtain MSR effects, the magneto-optical disk must have, as shown in the bottom portion (b) of
FIG. 18
, a recording layer, an intermediate layer, and a reading layer that exhibit different magnetic characteristics depending on temperatures.
The reading layer functions as a mask for masking the write mark M from the laser spot SP when reading is performed.
The recording layer holds a written signal or information represented by the write mark M as a magnetization direction.
The intermediate layer controls the coupling between the reading layer and the recording layer.
By applying an external magnetic field to the reading layer when reading is performed, magnetization directions of the reading layer are aligned. This masks the recording layer (front masking). Here, by using the laser spot SP to heat the disk, in part of the laser spot SP which has an intermediate temperature of the heat distribution, the magnetized information on the recording layer, that is, the magnetization direction of the write mark M, is transferred to the reading layer. By observing the magnetization direction transferred to the reading layer, the write mark M, which is written at a high density, can be read, even if the laser spot SP has a large diameter.
In part of the laser spot SP which has a high temperature of the heat distribution, the reading layer and the recording layer are magnetically separated, and the reading layer functions to mask the recording layer from the external magnetic field (rear masking).
By using the above-described MSR technique, high-density writing and reading with a density at least double that of conventional techniques can be performed. This can greatly increase the recording capacity of the magneto-optical disk.
However, in achieving high density, the MSR technique and the land/groove writing method cause the following problems.
Although the MSR technique greatly increases the recording capacity of the magneto-optical disk, it cannot be applied to the entire surface of the magneto-optical disk.
For the magneto-optical disk, data units called “sectors” are employed as a basic data format, and data strings formed on the tracks of the disk consist of the sector units, which are sequential.
Each sector consists of a preformatted header (hereinafter also referred to simply as a “header”) in which preformat data is written by embossed pits, and a write/read area (hereinafter referred to as an “MO area” for convenience of description) as a magneto-optical area in which data can be written or read, as shown in FIG.
19
.
In the header, a sector address, etc., is written by embossed pits.
In the MO area, data including user data are written.
Accordingly, in the sectors of the magneto-optical disk, a recording film adapted for the MSR technique can be formed only in the MO area. The MSR technique cannot be applied to the header.
On the magneto-optical disk, at a predetermined position in an outer peripheral or inner portion, an area in which system information and write information are prewritten is preformatted. The MSR technique cannot be applied to this preformatted area.
In other words, in the preformatted area and the preformatted header of the sector, pre-recorded pits (hereinafter referred to as “prepits”) must be formed at a conventional recording density because the MSR technique cannot be used.
As a result, the length of one byte is physically longer in the preformatted header than in the MO area. The area in the disk in which system information and write information are prewritten has greater redundancy.
In addition, a double-sided 5.2-gigabyte magneto-optical disk has a groove width of approximately 0.55 &mgr;m when employing the land/groove writing method. On a track formed on a groove G, a preformatted header is provided for the start of each sector, as shown in the top portion (a) of FIG.
20
.
In this configuration, a land L between one track (groove G) and an adjacent track (groove G) acts as a shield against crosstalk from a preformatted header on the adjacent track.
In the header, address information that has a single value is written twice as ID
1
and ID
2
.
Referring to the intermediate portion (b) of
FIG. 20
, when the land/groove writing method is also considered which has an identical pitch between groove tracks G and which uses a land L as a recording track in addition to the groove tracks G, the land L has a preformatted header similar to that on the adjacent groove tracks G, and has no shield for the header. Therefore, generated crosstalk makes it very difficult to read sector-address information written in the header on the land L. This causes deterioration in writing/reading performance or seeking performance.
In a general technique for avoiding the deterioration in performance, as shown in the bottom portion (c) of
FIG. 20
, the preformatted headers on the land track L and the groove track G are not radially arranged but either of tracks is arranged to be shifted backward by one length in the track direction. This can prevent the crosstalk from affecting address information to be read.
However, this case causes large redundancy since the start of each sector must have an area which is double the header area.
When the redundancy caused by the preformatted header in the employment of the MSR technique, and the redundancy caused by crosstalk avoidance in the land/groove writing method are taken into consideration, at least 5 percent of the total recording capacity is wasted. In other words, simply employing the MSR technique and the land/groove writing method cannot achieve an effective increase in the recording capacity.
Accordingly, for enabling a large recording capacity, the redundancy caused by the preformatted header in the employment of the MSR technique, and the redundancy caused by crosstalk avoidance in the land/groove writing method must be reduced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a disk recording medium the recording density of which is increased by an effective data arrangement in the header of each sector, using the MSR technique or the land/groove method, and a disk drive unit therefor.
To this end, according to an aspect of the present invention, the foregoing

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