Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2000-06-29
2003-10-07
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S044220
Reexamination Certificate
active
06631099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field modulation use magnetic head, a magneto-optical element, and an optical pickup devices used for an optical disk drives for recording or playing back a magneto-optic signal to or from a magneto-optic recording medium and to such an optical disk drive.
2. Description of the Related Art
In recent years, the advances made in the technology for digitally recording moving pictures, static images, or other video data have led to large volumes of data being handled, so magneto-optic disk drives and other optical disk drives utilizing magneto-optic recording capable of further raising the recording density have spread in use in place of floppy disk drives and other magnetic disk drives which have been conventionally generally been widely utilized.
For example, when a magneto-optic disk drive, one type of optical disk drive, records data, it focuses a laser beam on a position on the magneto-optic disk for recording the data to make the temperature of the magnetic material (magneto-optic recording layer) at that position rise up to the Curie temperature and cancel out the coercive force corresponding to data already recorded at that position and further applies a magnetic field corresponding to the data to be newly recorded to that position (position at which the temperature has become the Curie temperature) to thereby record the data.
For example, in the Mint Disc (MD) system or the like which have been already put into practical use as optical disk drives for recording and playing back of information data with respect to a recording medium, here a magneto-optic disk, by a magnetic field modulation system, a magnetic field generation coil (magnetic head) for applying a magnetic field at the time of recording data is arranged at a position facing the optical pickup device emitting the laser beam across the disk.
The magnetic field generation coil and the optical pickup device move to positions for recording the data on the optical disk, then the magnetic field generation coil applies the magnetic field to the predetermined position and the optical pickup device emits the laser beam.
Further, in recent years, as an optical disk drive for recording and playing back of information data with respect to a recording medium, that is, magneto-optic disk, by the magnetic field modulation system, there have been proposed for example a near field optical disk drive made by Tera Stor Co. for recording and playback while arranging the optical disk and the optical lens at a distance between them becomes 200 nm or less, an optical hard disk drive made by Quinta Co. in which the optical lens is mounted on a floating type slider, and other optical disk drives arranging the optical disk and the optical lens or a slider mounting the optical lens or the like at a distance of 200 nm or less to make it possible to raise the numerical aperture NA and further raise the recording density.
In the above near field optical disk drive or other optical disk drive raising the numerical aperture NA, in order to secure an optical skew margin when the numerical aperture NA is raised and a margin of the thickness of the optical disk substrate, the recording layer is arranged on the optical lens side of the optical disk substrate.
In the above optical disk drive, when arranging the magnetic field generation coil at the side of the optical disk opposite to the optical lens, if the inductance of the magnetic field generation coil is made small, that is, the diameter of the magnetic field generation coil is made small, in order to enable a high speed transfer of a large volume of data such as a video signal, it becomes difficult to apply an effective magnetic field of for example about 200 Oe to the recording layer of the optical disk since the spread of the magnetic field is large. Accordingly, in order to make it possible to transfer a large volume of data at a high speed, it becomes necessary to arrange the magnetic field generation coil for applying the magnetic field to the recording layer of the optical disk on the same side of the optical disk as the optical lens.
Further, by integrally constituting the magnetic field generation coil and the optical lens, a reduction of the thickness of the optical disk drive has become possible.
An explanation will be made next of a magneto-optical element integrally constituting the magnetic field generation coil and the optical lens.
FIG. 9
is a plan view of the configuration of a magnetic coil
46
part of a magneto-optic head portion according to the related art, which can be applied as a magneto-optic head of a magneto-optic disk system.
A spiral-shaped thin film coil
48
having a size of for example an inner diameter of 50 to 200 &mgr;m and an outer diameter of about 350 to 400 &mgr;m is formed on the periphery of an emitting portion
44
d
of a coil supporting substrate
44
on a main surface of the coil supporting substrate
44
facing the magneto-optic disk. The thin film coil
48
is covered by an insulation layer
49
.
Further, a magnetic core
47
a
is formed on the coil supporting substrate
44
beneath of the thin film coil
48
. The magnetic core
47
a
acts also as an electrode takeout portion inside the spiral shaped thin film coil
48
.
The emitting portion
44
d
region is the region from which the laser beam L emitted from a not illustrated semiconductor laser is emitted. In this region, an aperture portion Ha is formed in the magnetic core
47
a
and becomes the optical axis of the laser beam L.
The magneto-optical element integrally constituting the magnetic field generation coil and the optical lens emits the laser beam L from the emitting portion
44
d
to the magneto-optic recording layer of the magneto-optic disk and, at the same time, can apply a magnetic field generated by the thin film coil
48
and therefore can record and play back information with respect to the magneto-optic recording layer of the magneto-optic disk.
Summarizing the problems to be solved by the invention, in the optical disk drives of the MD and other magnetic field modulation systems which have already been put into a practical use, however, a bulk head is used for the magnetic head for generating the modulation magnetic field, so it has been difficult to raise the modulation frequency.
Further, in a magneto-optical element raising the numerical aperture by integrally constituting the magnetic field generation coil and the optical lens shown
FIG. 9
, It is necessary to provide the magnetic field generation coil at an outer circumferential portion of the emitting portion region serving as the optical axis of the laser beam and it is necessary to set the diameter of the magnetic field generation coil to a predetermined value or more, therefore it was not possible to configure the magnetic head to improve the efficiency of the magnetic circuit as was used in for example magnetic recording and it was difficult to apply the magnetic field to the recording layer of the optical disk with a low power consumption and a high efficiency.
Further, in order to generate the required magnetic field at the time of recording, a very large current must be passed through the magnetic field generation coil, therefore the amount of heat generated in the magnetic field generation coil becomes large, and, in the worst case, disconnection of the magnetic field generation coil has been sometimes induced.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a magnetic field modulation use magnetic head, a magneto-optical element, an optical pickup device, and an optical disk drive capable of applying a magnetic field to the recording layer of an optical disk with a low power consumption and a high efficiency and capable of preventing the disconnection of the magnetic field generation coil due to heat generation.
To attain the above object, according to a first aspect of the present invention, there is provided a magnetic field modulation use magnetic head for applying a magnetic fiel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Psitos Aristotelis M.
Sony Corporation
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