JP2002150634A - Method and device for read and write of magneto-optical medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for reading information from and writing information to a magneto-optical disk. SOLUTION: This device is provided with a first object lens placed between a first face of the magneto-optical disk and a first source of laser light. The device is provided also with a first floating magnetic head which is placed between the first object lens and the first face of the magneto-optical disk and includes a first coil for supply of a first magnetic field. The first coil prescribes a light channel through the first floating magnetic head so that laser light may reach the magneto-optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the field of disk drive mechanisms for reading data from and writing data to data storage disks. More particularly, the present invention relates to the field of magneto-optical (MO) disk drives.

[0002]

BACKGROUND OF THE INVENTION Conventional magneto-optical (MO) disk drives record data by locally heating a portion of the disk. MO disks or media include a recording layer of magnetic material. The coercivity of the heated portion of the media decreases when heated by the laser beam. This allows the magnetic polarity in that area to be reversed by the applied magnetic field. In such a disk drive, data is read from the medium by illuminating an area of the storage medium with a linearly polarized laser beam. The plane of polarization of the irradiation beam is rotated by the Kerr rotation effect. The direction of rotation is determined by the magnetic polarity in the irradiation area of the storage medium. As the disk is read, the polarization rotation is determined by a pair of optical detectors and a polarizing beam splitter to generate an output data signal. MO disk drive limitations include data access time and data density for storing data.

FIG. 1 is a diagram of a conventional MO recording system 100 commonly used with 130 millimeter (mm) diameter MO media. The system 100 is “substrate incident”
It is an example of a recording system. In a substrate injection system, a laser beam is incident on a thick substrate, travels through the substrate, and is focused on a recording layer below the substrate. System 100
Includes an objective lens 102 for focusing a parallel beam on a disk 116. The disk 116 is an example of a typical double-sided MO disk. The MO disk 116
Includes base layers 104 and 114 that form outer layers at opposing sides of the disk 116. Base layers 104 and 114
Is made of a material such as plastic or polycarbonate and has a thickness of about 1.2 mm. The recording layer 106 is the base layer 10
4 and the recording layer 112 is above the base layer 114.
Recording layers 106 and 112 can be made from any of a number of well-known materials, such as Tb-Fe-Co and rare earth transition metal alloys. The laser beam passing through the objective lens 102 penetrates the base layer 104 as shown, and enters a focal point on the surface of the recording layer 106.

[0004] System 100 has several disadvantages. One of the drawbacks of the system 100 is that the data must be erased by applying energy to the recording layer before writing new data. This is because a large fixed magnetic coil (not shown) having a large inductance is located on the opposite side of the disk 116 with respect to the objective lens 102 to assist in the writing process. Since the coil is kept at a relatively long distance from the media surface and has a relatively large inductance, the magnetic field cannot be reversed at high frequencies. Therefore, it is necessary to erase data before writing new data. The process of writing data to disk 116 slows down because it must be erased before writing.

Another drawback of system 100 is that disk 1
16 is relatively low in data density. Another disadvantage of system 100 is that only one side of disk 116 can be accessed at a time. This is because a relatively large coil occupies the space on the disk surface opposite to the objective lens. Therefore, this space cannot be used for another lens and actuator. To access different sides of disk 116, remove disk 116, flip it, and
00 must be reinserted. However, the disks 116 provide sufficient data security because the relatively thick base layers 104 and 114 allow the disks 116 to be handled without risk of data loss or difficulty reading the data due to contamination.

FIG. 2 shows another conventional MO recording system 20.
FIG. The parallel light beam 202 is
04 and reaches the disk 216. Disk 21
6 includes a base layer 206 typically 0.6-1.2 mm thick. The disk 216 further includes a base layer 206 and a protective layer 21.
It also includes the recording layer 208 between zero. In the system 200, the large fixed coil of the system 100 has been replaced by a relatively small coil in the floating magnetic recording head 214. The flying height 212 is maintained by an air bearing created as the disk 216 passes below the flying magnetic recording head 214. When writing to disk 216, the magnetic field generated by magnetic recording head 214 is used with parallel light beam 202 passing through objective 204. The smaller coil of the magnetic recording head 214 has less inductance than the larger fixed coil of the system 100. Since the inductance has been reduced, data can be transferred to disk 2 by switching the magnetic field.
16 can be directly overwritten.

However, system 200 still has the disadvantage of relatively low storage density. Further, the disk 216
Are single-sided rather than double-sided disks, reducing overall storage capacity.

[0008] System 200 also has the disadvantage of requiring a mechanical connection between the light beam on one side of disk 216 and the magnetic recording head 214 on the other side of disk 216. Typically, this coupling is achieved by mechanical linkage around the disk 216 from the objective lens 202 to the magnetic recording head 214. Mechanical linkage cannot be allowed to interfere with the movement (during focusing) of the objective lens 202 or the disc 216.

FIG. 3 is a diagram of a conventional MO recording system 300. The system 300 is an example of an “air-entry” design, where the lens is kept very close to the media and the laser beam is incident on a very thin protective layer 309 on the recording layer 308 of the disk 318. The system 300 includes a floating magnetic recording head 316, a lens 314 and a lens 3
A two-piece objective lens of 12 is adopted. Prior art systems similar to system 300 utilize other lens designs, for example, three-piece objective lens designs. Lens 314 is kept very close to disk 318. The collimated light beam 302 is coupled to lenses 312 and 312
Go through 14. Lens 312 and lens 314 are
It is integrated with the slider 304 and the magnetic recording head 316. The floating height 306 for the system 300 is typically
It is shorter than the wavelength of the laser beam used to read from and write to the MO disk 318.

The disk 318 has an MO on the base layer 310.
It has a recording layer 308. In system 300, the need for a focus actuator is eliminated because the floating objective lens 314 is close to the disk 318. As is well known, focus actuators are mechanisms that adjust the height of the objective lens above the disk during read and write operations. In the case of the system 300, the height of the floating objective, and thus the focus of the floating objective 314, is determined by the air bearing created between the slider 304 and the recording layer 308 during floating.

By keeping the distance between the floating objective lens 314 and the recording layer 308 shorter than the wavelength of the laser beam used, the laser beam can be focused in near-field mode of operation. As is well known, the near-field mode of operation utilizes the phenomenon of evanescent coupling. This requires that the objective lens be kept very close to the recording layer. Recording using evanescent coupling allows for a smaller spot size, and thus a higher recording density and better data throughput.

System 300 has several disadvantages. For example, the surface of the layer 309 and the surface of the lens 314 closest to the disc become dirty,
Permanent damage to the drive system can occur.

Another disadvantage of the system 300 stems from the fact that the floating height must be tightly controlled because there is one objective lens and no focus actuator. Floating height and protective layer 30 over recording layer
Variations in the thickness of 9 (and possibly without a protective layer) must be controlled within the depth of focus tolerance of the floating lens. Generally, the tolerance of the height of the floating height 306 and the thickness of the protective layer 309 is a ratio of the nominal thickness. Therefore, in order to reduce the tolerance, the protective layer 30
Nominal thickness of 9 must be reduced. For example, the depth of focus tolerance is typically around 0.5 microns. Protective layer 3
A typical tolerance for adding 09 is 10 percent thickness of the protective layer. Therefore, in order for the thickness variation of the protective layer 309 to be less than 0.5 μm, the floating height 306 is required.
And the thickness of the protective layer 309 must be very small.

In the case of a near-field system such as the system 100, the floating height (the bottom surface of the floating lens 314 and the recording layer 308)
Must be shorter than the wavelength of the laser beam. The wavelength of the laser beam is typically 700 nanometers. Therefore, the thickness of the protective layer on the recording layer 308 must be about 25 nanometers. It is extremely thin and cannot protect the data on the recording layer 308 from manual handling in removable disk applications or from corrosion or contamination during storage. Even with the protection of the cartridge covering the disk 318, any fouling from particles in the air or from humidity or corrosive gases cannot be avoided over time.

[0015] All conventional disk drives share similar drawbacks regarding accessing data on storage disks. Current disk drives, even those designed to access double-sided media, are limited to accessing one side of the media at a time. It has not been possible in the past to simultaneously and independently access either side of a double-sided disc. One reason for this is that the read / write head mechanisms on both sides of the disk are constructed to move together or not at all. Thus, current disk drives have limited data access speeds. This shortcoming is shared by conventional MO drives and drives that use other technologies, such as those used in computer hard disk drives.

[0016] Techniques exist for making multiple disk drives appear as a single drive to a client device. Redundant array of independent drives (redu
ndant arrays of independent drives (RAID)
The input data is divided into a plurality of streams, which are simultaneously written to a plurality of drives. RAID drives can be used to increase throughput by splitting a single input data and writing each portion to multiple drives. RAID also
Different copies of the same data can also be used to achieve data redundancy by sending them to multiple drives simultaneously. Although the use of RAID can increase access speeds, they are expensive because they are simply devices that include replicas of conventional disk drives, each having the limitations discussed above with respect to current disk drives. And complicated.

[0017]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an MO drive for higher density data storage on single or double sided media coated to handle the media without risk of data loss. It is.

Another object of the present invention is to provide an MO drive capable of directly overwriting data without initial erasure.

Another object of the present invention is to provide an MO drive that simultaneously and independently accesses both sides of a double-sided disc.

[0020]

SUMMARY OF THE INVENTION A method and apparatus for reading from and writing to a magneto-optical disk is described. The apparatus includes a first objective lens located between a first surface of a magneto-optical disk and a first source of a laser beam. The apparatus further comprises a first floating magnetic head located between the first objective lens and the first surface of the magneto-optical disk and including a first coil for supplying a first magnetic field. The first coil has a beam channel through the first floating magnetic head to allow the laser beam to reach the magneto-optical disk.

[0021]

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a magneto-optical (MO) disk drive and an MO disk. In one embodiment, recording is performed using a farfield technique with a single objective lens that focuses the collimated laser beam. The collimated laser beam passes through an objective lens and then through an aperture through a floating magnetic head floating above the MO disk. Using a protected MO disk, an improved data storage density over conventional storage technology is achieved. In one embodiment, the MO disk drive includes two opposing recording layers covered by a coating layer.
In this embodiment, both the floating magnetic head and the objective lens are located on each side of the MO disk and are operated independently to allow simultaneous and completely independent access to both sides of the MO disk.

FIG. 4 is a diagram of an MO data storage / retrieval system 400 according to one embodiment of the present invention. In FIG.
Except for "a" or "b", like-numbered elements are identical or functionally equivalent. For example, objective lens 414a is the same or functionally equivalent to objective lens 414b.

The objective lens 414a focuses the parallel laser beam 402a. The flying height 406a of the magnetic recording head 418a above the disk 420 can be between 0.05 and 5.0 microns, depending on the particular embodiment. The magnetic recording heads 418a and 418b
Creates a magnetic field with a relatively low inductance,
Data can be directly overwritten when switching the magnetic field. Higher storage densities can be achieved by modulating the magnetic fields created by the magnetic storage heads 418a and 418b during the writing and reading processes.

The magnetic recording head 418a has a light channel 416, which is an opening through the center of the magnetic recording head 418a.
a. The slider 404a is connected to the magnetic recording head 418.
a, and when the disk 420 is rotating, the magnetic recording head 418a
20 is floated on. System 40
0 is the MO disk 42 using well-known far-field technology.
Record data on 0. In far-field technology, the focal length (the distance from the objective lens to the focal point on the recording layer) is relatively long, so that the objective lens is not in contact with or close to the recording layer.

In this embodiment, the MO disk 420 has spiral grooves in both recording layers. The spiral groove on the opposite recording layer spirals in the opposite direction, so that the rotating disk can be accessed simultaneously from both sides. Other embodiments use double-sided MO disks with concentric grooves. Spiral grooves are preferred when the data to be stored and accessed has a continuous nature. Concentric grooves are preferred when the data stored and retrieved has lower continuity and more "random" nature.

The MO disk 420 includes a central base layer 412. The recording layers 410a and 41 are provided on both sides of the base layer 412.
0b are provided respectively. Coating layer 408
a forms one surface of the MO disk 420 and covers the recording layer 410a. The coating layer 408b is an MO
The opposite surface of the disk 420 is formed, and the recording layer 410 is formed.
cover b.

In this embodiment, the actuator for controlling the objective lens 414a and the magnetic head 418a is
It is completely independent of another actuator that controls the objective lens 414b and the magnetic head 418b. Actuators are well known in the art and are not shown for clarity. The system 400 reads and writes to each side of the MO disk 420 completely independently. For example, each head assembly reads the recording layer 410b at the same time as the recording layer 410a is written.

In the embodiment of FIG. 4, MO data storage / retrieval system 400 includes two magnetic heads 418 and two lenses 414 for independently accessing each side of MO disk 420. In other embodiments, the MO data storage / retrieval system may include only one magnetic head 418 and one lens 414.

FIG. 5 is a diagram of a slider / magnetic recording head suspension assembly 1000 according to one embodiment. A suspension assembly such as the suspension assembly 1000 floats each slider 404 and the magnetic head 418. The magnetic recording head suspension assembly is not shown in FIG. 4 for clarity. The slider / magnetic recording head suspension assembly 1000 is loaded by rotating the disk and engages or loads the slider / magnetic recording head suspension assembly 1000 prior to read and write operations. An air bearing is formed between the slider / magnetic recording head assembly 1010 and the rotating disk;
The slider surface never contacts the disk surface. In another embodiment, the slider stops on the disk surface when the disk is not moving. In these embodiments, the slider stops on the disk surface until the disk reaches a constant rotational speed, after which an air bearing is formed and the slider is pulled away from the disk surface.

During read and write operations, laser beam 1008 passes through objective lens 1006 and beam channel 1013 in slider / magnetic recording head assembly 1010. The light channels 1013 are rectangular in this embodiment, but may be circular or irregular in other embodiments. Light channel 1013 is
It is surrounded by 12. The slider / magnetic recording head assembly 1010 and the winding 1012
4 and load beam 1002. Gimbal 1004 also has an aperture that allows light rays to pass through gimbal 1004. The openings in gimbal 1004 are rectangular in this embodiment, but may be circular or irregular in other embodiments.

FIG. 6 is a top view of a disk drive 700 according to one embodiment of the present invention. In this embodiment, disk drive 700 includes two optical pickup / front end electronics assemblies 716a and 716b. The assembly 716 is moved back and forth on each side of the MO disk 710 by a linear actuator in this embodiment. In other embodiments, other actuators may be used, for example, a rotary actuator.

The optical pickup / front end electronics assembly 716a is located on one side of the MO disk 710 and the assembly 716b is located on the MO disk 710.
Located on the opposite side of. Each assembly 716 is an integrated optics assembly. As is well known, an integrated optics assembly has a focus unit in one unit.
Includes actuators, tracking actuators, coarse actuators, optical components, and front-end electronics. In the embodiment shown in FIG. 6, the integrated optics has been partially selected for ease of assembly. Extreme precision is required to align the optical components of the mechanism. When integrated optics are utilized, alignment with an assembly, such as assembly 716a, is performed on another station before assembling the disk drive. This results in faster and cheaper assembly.

In another embodiment, separation optics are utilized. The separation optics includes a moving part and a fixed part. The moving part moves over the disk and includes an objective lens, a mirror, a fine actuator, a coarse actuator, and a focus actuator. The fixed part includes the laser diode, detector, optical components, and front end optics.

In that embodiment, the focus actuator and the fine actuator are coupled to the coarse actuator. The coarse actuator performs a relatively large motion transversely across the surface of the disk. The focus actuator moves axially relative to the disk to focus the laser beam. The fine actuator performs small lateral movements or microsteps to keep the focused laser beam on the tracks of the disk.

In this embodiment, the magnetic head is coupled to the coarse actuator by suitable flexible means. In this embodiment, the magnetic head is separated from the focus actuator and the fine actuator. In an alternative embodiment, the magnetic head is coupled to both a focus actuator and a fine actuator, both of which are coupled to a coarse actuator.

The disk drive 700 includes a carriage coil 702, a return magnetic path assembly 704, and a magnet 706. Spindle motor 708 engages MO disk 710 as described more fully below.
In this embodiment, dimension 718 is approximately 200 mm, dimension 7
14 is about 140 mm, and 712 is about 130 mm. Other embodiments of the disk drive 700 can operate with MO disks of various shape factors. For example,
Disk drives incorporating the present invention may be used with the MO disks described herein,
mm, 90 mm, 120 mm and other dimensional shape factors.

Disk drive 700 is an embodiment that includes two optical pickup / front-end electronics assemblies. In another embodiment, the MO disk 7
Includes only one optical pickup / front-end electronics assembly with access to 10 single sides. These embodiments only read or write to one side of the disk at a time.

FIG. 7 is a side view 800 of the disk drive of FIG. Disk drive 700 is partially surrounded by a top cover 802, a bottom cover 804, and a printed circuit board (PCB) 808. The objective lens 810 of the assembly 716a is shown. Assemblies 716a and 716b are the same or functionally equivalent. A magnetic head and suspension 818 for assembly 716b is shown.
In this embodiment, the magnetic head is designed as a magnetic field modulation head. Magnetic field modulation techniques are well-known in the art. Coarse carriage coil 814 for assembly 716b is shown. A spindle motor 816 that engages the disk 812 is shown. Reference number 8
06 indicates a spindle motor at a remote position. Spindle motor 708 is remote during insertion or removal of disk 812. Spindle motor 7
08 rises after the MO disk 710 is inserted, and engages with the MO disk 710.

FIG. 8 is a side view 900 of the disk drive 700. The side view 900 associates one magnetic head / suspension assembly 902 and objective 904. In this embodiment, the magnetic head / suspension assembly 902 is mounted on the coarse actuator body and not mounted on the focus actuator.

[0040] Top cover 906, bottom cover 912, and PCB assembly 908 are also shown. Optical Pickup / Front-End Electronics Assembly 9
16 are shown on both sides of the MO disk 910. A carriage coil 914 for one assembly 916 is shown. In this embodiment, the dimension 924, ie, the thickness of the MO disk 910, is between 0.6 and 2.4 mm. In this embodiment, dimension 918 is 5 mm, dimension 92
2 is 10 mm and dimension 920 is 41.3 mm.

The illustrated embodiment performs parallel processing of data or redundant processing of data in one disk drive. The optical pickup / front end electronics assembly 716 of FIG. 6 is operated by independent actuators, and the incoming data stream is split between the two assemblies and read independently on both sides of the MO disk 710. And / or writing is performed. Thus, the user may choose to utilize parallel processing to improve throughput or reduce access time. Alternatively, the user may choose to redundantly access both sides of the MO disk 710 to make a backup copy of the data. When the parallel access mode is selected, command queuing client devices can be serviced more quickly because commands in the queue are executed smoothly even if they are not of the same type. . For example, if the write operation is
10 on one side and at the same time read the MO disk 7
10 on the opposite side.

The illustrated embodiment is an MO using far field technology with increased data density, simultaneous and independent access to the two data storage surfaces, and direct overwrite capability.
Make a record. Other embodiments include only one optical pickup / front-end optics assembly and therefore do not have simultaneous and independent access to the two data storage surfaces.

The present invention has been described in terms of a particular embodiment. For example, the illustrated embodiment provides an MO for a particular shape factor.
Includes a disk and a disk drive having integrated optical and linear actuators. However, one of ordinary skill in the art can make modifications and variations to the specific embodiments shown without departing from the spirit and scope of the invention as set forth in the appended claims.

[Brief description of the drawings]

FIG. 1 is a diagram of a prior art magneto-optical (MO) data storage / retrieval system.

FIG. 2 is a diagram of a prior art MO data storage / retrieval system.

FIG. 3 is a diagram of a prior art MO data storage / retrieval system.

FIG. 4 is a diagram of an MO data storage / retrieval system according to one embodiment of the present invention.

FIG. 5 is a diagram of a magnetic head suspension assembly according to one embodiment.

FIG. 6 is a top view of the MO drive according to one embodiment.

FIG. 7 is a partial side view of the MO drive of FIG. 6;

FIG. 8 is a partial side view of the MO drive of FIG. 6;

[Explanation of symbols]

 400 MO data storage / retrieval system 402a Parallel laser beam 404a Slider 406a Floating height 408a Coating layer 408b Coating layer 410a Recording layer 410b Recording layer 412 Base layer 414a Objective lens 414b Objective lens 416a Light channel 418a Magnetic recording head 418420 Magnetic recording head MO disk

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[Procedure amendment]

[Submission date] May 7, 2001 (2001.5.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/105 566 G11B 11/105 566A 586 586C

Claims (18)

[Claims] A first objective lens located between a first surface of the magneto-optical disk and a first source of the laser beam; and a first objective lens located between the first objective lens and the first surface of the optical disk. And a first floating magnetic head including a first coil for supplying a first magnetic field, wherein the first coil causes the laser beam to reach the magneto-optical disk Apparatus for reading from and writing to a magneto-optical disk with a light channel passing through said first floating magnetic head. 2. The method according to claim 1, wherein a focal length between the first objective lens and a focal point on a first recording layer of the magneto-optical disk is a distance suitable for recording using a far-field technique. The described device. 3. The first coil according to claim 2, wherein the first coil has an inductance such that when the polarity of the first magnetic field is switched, data is directly overwritten on the first recording layer. Equipment. 4. The optical pickup according to claim 1, further comprising a first optical pickup assembly including the first objective lens, the first floating magnetic head, and first front end electronics. An assembly moves linearly over the first surface of the magneto-optical disk under the control of a first linear actuator during reading and writing to the first recording layer of the magneto-optical disk; Claim 3
An apparatus according to claim 1. 5. A second objective lens functionally identical to the first objective lens, a second floating magnetic head functionally identical to the first floating magnetic head, and the first objective lens. Further comprising a second optical pickup assembly comprising a second front end electronics functionally identical to the front end electronics of the second optical pickup assembly;
An optical pickup assembly linearly moves over a second surface of the magneto-optical disk under control of a second linear actuator during read and write operations on a second recording layer of the magneto-optical disk. 5. The apparatus of claim 4, wherein the apparatus moves and the first and second optical assemblies operate simultaneously and independently. 6. The magneto-optical disk, wherein the magneto-optical disk is in contact with a central base layer between the first recording layer and the second recording layer, and the first recording layer; A first coating layer forming a surface; and a second coating layer in contact with the second recording layer and forming the second surface of the magneto-optical disk, wherein the first and second coatings are included. 6. The apparatus of claim 5, wherein each of the layers has at least a thickness sufficient to allow manual handling of the magneto-optical disk without damaging data. 7. The apparatus according to claim 6, wherein said magneto-optical disk has a diameter of 130 mm. 8. The apparatus according to claim 6, wherein said magneto-optical disk has a diameter of 130 mm. 9. A first optical disk positioned between a first surface of a magneto-optical disk and a first source of a laser beam and used to read from and write to the magneto-optical disk.
The first objective lens and the first of the magneto-optical disk
A first floating magnetic head located between the
A magneto-optical device, wherein the first floating magnetic head supplies a first magnetic field, so that data written to a first recording layer of the magnetic disk is directly overwritten when the polarity of the first magnetic field is switched. A device for reading from and writing to disks. 10. The apparatus according to claim 1, wherein a focal length between the first objective lens and a focal point on the first recording layer is a distance suitable for recording using far-field technology. 11. The first floating magnetic head is formed with a light beam channel through the floating magnetic head that allows the laser beam to reach the first surface of the magneto-optical disk. 10. The apparatus of claim 9, including a first coil that is located. 12. The first optical pickup further comprising: a first optical pickup assembly including the first objective lens, the first floating magnetic head, and first front-end electronics. Moving on the first surface of the magneto-optical disk under control of a first actuator during read and write operations on the first recording layer of the magneto-optical disk. apparatus. 13. A second objective lens positioned parallel to a second surface of the magneto-optical disk and functionally identical to the first objective lens; And a second optical pickup assembly comprising a second floating magnetic head that is identical to the first and second front-end electronics functionally identical to the first front-end electronics; The second
Moving the optical pickup assembly over a second surface of the magneto-optical disk under control of a second actuator during a read or write operation on a second recording layer of the magneto-optical disk; 5. The apparatus of claim 4, wherein one optical assembly and said second optical assembly operate simultaneously and independently. 14. The magneto-optical disk, comprising: a central base layer between the first recording layer and the second recording layer; and a first surface of the magneto-optical disk, in contact with the first recording layer. And a second coating layer that contacts the second recording layer and forms a second surface of the magneto-optical disk.
An apparatus according to claim 3. 15. The method of claim 1, further comprising transmitting a parallel laser beam to a focal point on a first magnetic layer through a first objective lens and through a first ray channel through a first floating magnetic head. Reading from a first recording layer; passing the parallel laser beam through the first objective lens and through the first ray channel to a focal point on the first recording layer; and Writing to said first recording layer by modulating a magnetic field produced by one of said floating magnetic heads, and retrieving information therefrom. 16. The method of claim 1, further comprising transmitting a parallel laser beam through a second objective lens and through a second ray channel through a second floating magnetic head to a focal point on the second recording layer. Reading from a second recording layer of the magneto-optical disk while writing to the recording layer; passing the second light beam through the second objective lens and through the second light beam channel of the second floating magnetic head. Transmitting the parallel laser beam to the focal point on a recording layer, and modulating a magnetic field generated by the first floating magnetic head, thereby writing the second recording while writing to the first recording layer. Writing to the layer. 17. The method according to claim 17, wherein the step of reading and the step of writing independently move the first floating magnetic head and the second floating magnetic head so that the first floating magnetic head and the second floating magnetic head move on the first recording layer and the second recording layer. 17. The method of claim 16, including locating each of the data. 18. The first objective lens, wherein the reading and writing steps are performed such that a first focal length and a second focal length are each longer than a quarter of the wavelength of the parallel laser beam. 17. The method of claim 16, including positioning the second objective lens.