JPS60147948A - Photo-electro-magnetic recording device - Google Patents

Abstract

PURPOSE:To record uniform bits and also to attain reproduction with high S/N by providing a magnetic field generating means where an optical beam irradiating of a magnetooptical recording medium of disc form corresponds and the strength of an auxiliary magnetic field is increased as the outer circumference. CONSTITUTION:A disc 2 as a disc form magnetooptical recording medium is turned by a motor at a prescribed angular velocity. The optical beam modulated based on the information generated from a laser light source 2 of an optical beam irradiating device 14 is collected via an optical head part 13 and a condenser lens 5 into a minute spot and irradiated on the disc 1. A permanent magnet 101 generates an almost uniform magnetic field at an equal interval and the distance between the magnet 101 and the disc 1 is arranged so that the inside of disc 1 is parted in comparison with the outside of the disc 1. Thus, the strength of the auxiliary magnetic field to the disc 1 is increased toward the outer circumference of the disc 1, the same bits are recorded at the inside and outside of the disc 1 and the S/N at reproduction is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording device that magneto-optically records information on a disc-shaped recording medium using a light beam narrowed to a minute spot.

In particular, magneto-optical recording devices that record information on a disc-shaped recording medium using a light beam focused on a minute spot have attracted attention in recent years because they are capable of recording information at high density.

In the above-mentioned magneto-optical recording device, the light beam irradiation means is directed in the radial direction of the disk-shaped recording medium while irradiating the rotating disk-shaped recording medium with a light beam that has been focused into a minute optical beam spot under a bias magnetic field. Information is recorded by moving continuously or gradually in steps.

Recording is performed by irradiating the recording layer of a recording medium with a light beam, heating the irradiated minute part to around the Curie temperature or compensation temperature, and reversing the magnetization direction of the recording medium when cooled by a bias magnetic field and a demagnetizing field from around the heated part. and record.

Here, when recording is performed by rotating a circular recording medium at a constant angular velocity, the recording for a unit time of light beam irradiation is performed depending on when the light beam scans the outer circumference of the disk-shaped recording medium and when it scans the inner circumference. The amount of light energy absorbed by the layers is different, and if the intensity of the light beam is set to be appropriate when scanning the outer circumference of the recording medium, the light beam energy will be too strong at the inner circumference.
A problem arises in that the duty ratio of the pit becomes larger than 50 inches, and the SAJ during reproduction is significantly reduced.

Conversely, if the light beam intensity is adjusted to be appropriate when scanning the inner circumference of the recording medium, a problem arises in that sufficient recording is not performed on the outer circumference.

To this end, a proposal has been reported in which the intensity of the light beam is varied depending on the radial position of the light beam on the recording medium. (For example, JP-A No. 51-23902, JP-A No. 52-69807) However, according to the above recording method, the intensity of the light beam is not constant. There was a drawback that the actual gain was different and the above operation became unstable. In addition, an electric circuit is required to change the intensity of the light beam, which complicates the light beam generation circuit. It is an object of the present invention to provide a magneto-optical recording device which obtains signals and focusing signals, obtains stable tracking and focusing of a light beam, and forms a bit string with a good S/N ratio of a reproduced signal during reproduction.

That is, the present invention rotates a disk-shaped magneto-optical recording medium, focuses a modulated light beam generated from a light beam generator on the magneto-optic recording medium into a minute spot, and records data by applying an auxiliary magnetic field to the magneto-optical recording medium. In the magneto-optical recording device, the outer periphery and inner periphery of the magneto-optical recording medium are arranged such that the intensity of the auxiliary magnetic field increases as it goes toward the outer periphery of the magneto-optical recording medium, corresponding to the light beam irradiation area of the magneto-optical recording medium. The above objective could be achieved by forming equivalent bits regardless of the type of bit.

Embodiments of the present invention will be described below with reference to the drawings.

The principle of the magneto-optical recording device according to the present invention will be explained with reference to FIG.

In FIG. 1, a disc-shaped magneto-optical recording medium (hereinafter referred to as
It is called a disk. ) 1 is, for example, Gd, Tb on a glass disk.
, Fe, Mn, Bi, or the like is deposited by sputtering or the like. During recording, a light beam modulated based on information emitted from a laser light source 2 is made into parallel light by a collimator lens 3,
Polarizer 6. After passing through the beam splitter 4, the light beam is focused using a condensing lens 5 onto the surface of the disk 1 being rotated by the motor 12 as a light beam spot having a diameter of about 1 μm.

Here, the magnetic film of the disk l has been magnetized in advance with its orientation aligned in the vertical direction, and its cue is aligned by irradiating the laser beam under a magnetic field in the opposite direction to that generated by the bias magnetic pole device IO. When the magnet is heated above the temperature and cooled down, the direction of magnetization is reversed by the magnetic field of the magnetic pole device 10, and image information is recorded on the disk as shown in bit 15 in FIG.

Note that the magnetic field generated by the bias magnetic pole device 10 is as follows:
It is generated in accordance with the radial trajectory of the light beam spot on the disk 1, and its intensity increases from the center of the disk 1 to the outer circumference. A bias magnetic field of appropriate strength is generated depending on the radial position of the disk 1, and the light beam energy given to the recording layer of the disk 1 by the light beam spot is balanced with the strength of the bias magnetic field, so that bits of an appropriate size are generated. The rows are formed regardless of the inner or outer circumference of the disk 1.

On the other hand, during reproduction, a laser light source 2 emits a light beam of constant intensity and irradiates the bit string formed on the disk l. Then, the direction of the reflected light from the disk 1, whose plane of polarization has been rotated according to the recorded information due to the magnetic Kerr effect, is changed by beam splitting, and guided to the light receiving element 8 through the condenser lens 11 and the analyzer 7, where the signal is detected. The recorded information is reproduced by the signal processing circuit 9.

In addition, in both the above-mentioned recording and reproduction, focusing signals and tracking signals are obtained by well-known means, and accordingly, for example, the objective lens 5 is moved in the optical axis direction or it is moved in the radial direction. focusing and tracking. Further, reference numeral 18 indicates a collimator lens 3, a polarizer 6. Beam splitter 4. Condensing lens 11, analyzer 7. Light receiving element 8. An optical head section 14 consists of a signal processing circuit 9; an optical head section 18; and a semiconductor laser 2. A light beam irradiation device consisting of an objective lens 5, which is moved continuously or gradually in a stepwise manner in the radial direction of the disk 1 by a well-known means (not shown) during recording or reproduction, to record or record information. Perform playback.

An example of the recording characteristics of the magnetic layer according to the present invention is shown based on FIG. Figure 3 shows that a laser beam with an output of 1-Omw is focused on the disk to 1 μInφ as described above, and Gd,
It shows the bit diameter on the disk obtained by magnetization reversal when the magnetic surface on the disk made of Tb, Fe and rotating at 11,000 rpm is irradiated for 03 μs.

The X-axis direction shows the intensity of the bias magnetic field applied during light beam irradiation, and shows how the bit diameter changes depending on the intensity of the bias magnetic field. Generally, in such recording, magnetization reversal occurs due to the demagnetizing field from the surrounding magnetic layer even if the magnetic layer irradiated by the light beam is not heated to one Curie temperature, but the bias magnetic field assists this demagnetizing field. It is something. The solid line is the radius r on the disk
= 100 (nun), the dotted line is the radius on the disk r = 5
This is the measured value at the point 0 (nun).

For example, under the same conditions as above, the magnetic field exerted by the bias magnetic pole device 10 shown in FIG. 1 on the recording layer of the disk 1 is approximately 110 (Oe
), and approximately 350 (Oe) at a radius of 100 m.
If the radius of disk 1 is 50 m and 10
A 1.0 μm bit is formed at the 0wn position. So, in the same way as this, from the radius of disk 1 xo
If the bias magnetic pole device 10 is configured to apply an appropriate bias magnetic field so that it increases continuously from 110 (Oe) to 350 (Oe) between
．． (It becomes possible to form bits with a bit diameter of 1 μm on the disk 1.

Note that the relationship between the position of the optical beam spot in the radial direction of the disk and the bias magnetic field strength is generally a proportional relationship, but the curve may have a different relationship due to the temperature characteristics of the coercive force Hc of the magnetic thin film medium. shows.

FIG. 4 is an explanatory diagram showing a specific embodiment of the magneto-optical recording device according to the present invention. In the figure, 14 is a light beam irradiation device with the same configuration as shown in FIG. 1, ■ is a disk, and 1o1 is a permanent magnet as the bias magnetic pole device 10 in FIG. By generating a magnetic field and making the distance between the permanent magnet 101 and the disk 1 farther on the inside of the disk 1 compared to the outside of the disk 1, the bias magnetic field effect is made different, and the same effect is generated on the inside and outside of the disk 1. This allows bits to be formed.

In addition, a magnetic material may be attached to the surface of the permanent magnet by changing the thickness of the magnetic material, and of course, the residual magnetization of the permanent magnet may be varied in the radial direction of the disk.

However, in this case, the permanent magnets can be placed equidistant from the disk.

FIG. 5 is an explanatory diagram showing another embodiment of the present invention.

In the figure, 1 is a disk, 4 is a light beam irradiation device having the configuration shown in FIG. 102a, and a sliding section 102b that moves in the radial direction of the disk 10 together with the light beam irradiation device 14 and slides on the fixed resistance section 102a. 103 is a magnetic material provided directly under the disk l corresponding to the locus of the light beam spot formed on the disk 1 by the light beam irradiation device 14; 104 is a coil wound around this magnetic material; The other end is connected to the power supply 10.
Fixed resistance part 102a on the outermost circumference side of the disk 1 via 5
connected to one end of the

As the light beam irradiation device 14 moves from the center to the outer periphery of the disk l, the sliding piece 102 +) also moves in the same direction, and the resistance value of the sliding resistor 102 decreases. As the resistance value decreases, the power supply 105 causes it and the coil 1 to
The current flowing through 04 increases. Therefore, as this current increases, the strength of the magnetic field generated from the magnetic body 103 also increases.

The direction of this magnetic field is opposite to the initially set magnetization direction of the recording layer of the disk 1, and is used as an auxiliary magnetic field for recording.

Therefore, the further the light beam irradiation device 14 goes to the outer periphery of the disk 1, that is, the farther the light beam spot by the light beam irradiation device 14 goes to the outer periphery of the disk 1, the more the sliding variable resistor 102. Magnetic material 108° coil 104. Power supply 1
The magnetic field applied to the recording layer of the disk 1 by the bias magnetic pole device IO composed of 05 becomes stronger. As a result, equivalent bits are formed on the inner and outer circumferences of the disk l.

FIG. 6 is an explanatory diagram showing another embodiment of the present invention. Components with the same reference numerals shown in FIG. There is.

103 is a magnetic material, 104 is a coil wound with a magnetic material, and its position is the same as that described in FIG. 108 is a central processing unit that stores a control amount for adjusting the output of the variable voltage source 109 in response to an address signal from the address reproduction circuit 106. The control amount is read out from the read-only memory (hereinafter abbreviated as ROM) 107 and the variable voltage source 1
Adjust the output of 09. The variable voltage source 109 is connected to the coil 104
This is the power supply for energizing the.

An address number is recorded in advance on the disk l, and the light beam emitted from the laser light source 2 is focused as a light beam spot on the recording layer of the disk l by the objective lens 5 as described above, and information is transferred onto the disk l. While recording, the reflected light is detected by the light receiving element 8 via the beam splitter 4, and the address is read by the address reproducing circuit 106. The central processing unit 108 inputting this address signal from the address reproducing circuit 106 inputs the ROM
Read the control amount according to the address signal from I, 07,
The output of variable voltage source 109 is controlled based on this control amount. The output of the variable voltage source 109 is applied to the coil 104, which is energized in accordance with the output, and a magnetic field is generated from the magnetic body 103 toward the recording layer of the disk 1 in accordance with the amount of energization. The strength of this magnetic field is set so that the position of the light beam spot on the disk 1 becomes higher as the outer circumference increases, so that bits with the same diameter are formed on the disk 1 regardless of whether it is on the inner or outer circumference.

FIG. 7 is an explanatory diagram of another embodiment of the present invention.

Reference numeral 110 denotes a guide bar, which is provided so as to be inclined in the radial direction from the center side directly below the disk 1 to the outer circumferential side, and its position is closer to the disk 1 as the outer circumferential side of the disk 1 approaches. 11
1 is a sliding part that loosely fits into the guide bar 110 and slides on the guide bar 110, and a permanent magnet 1'l is attached to the side thereof.
2 is installed.

The direction of the magnetic field generated by this permanent magnet 112 is
The direction of magnetization in the recording layer of the disk 1 is opposite to the initially set magnetization direction.

Jd, it is desirable that the magnetic pole of this permanent magnet 112 is always placed directly below the light beam spot formed on the disk 1 by the light beam irradiation device 14. Here, the permanent magnet 112 and the sliding part assembly 111 move together with the light beam irradiation device 14 along the guide bar 110 by means not shown. Therefore, as the light beam spot moves toward the outer periphery of the disk 1, the permanent magnet 112
is guided by the guide bar 110 and approaches the disk l,
The strength of the magnetic field applied to the recording layer of the disk 1 by the permanent magnet 112 increases. As a result, bits of the same diameter are stably formed on the recording layer of the disc 1 regardless of whether it is on the inner or outer periphery of the disc 1.

In addition to this, the present invention uses a position meter, a magnet scale, etc. to detect the position of the light beam irradiation device, that is, the position of the light beam spot, instead of detecting the position of the light beam spot using an address signal as shown in FIG. Alternatively, the intensity of the auxiliary magnetic field may be adjusted according to the detected signal.

In each of the above examples, a coil was wound around a magnetic material, but
A coil may be wound around the permanent magnet in the opposite direction, and the magnetic force of the permanent magnet may be reduced by energizing the coil. There is also a device in which a plurality of electromagnets are arranged in the radial direction of the disk and the number of turns of the coil is increased depending on the surface of the disk 1.

Alternatively, the side of the magnetic body facing the disk may be inclined so that a constant amount of current is always applied to the magnetic body, or the width of the magnetic body may be made thinner toward the outer periphery of the disk.

As explained above, a means for irradiating the magneto-optical recording medium with a light beam and a magnetic field generating means for generating a magnetic field with an intensity corresponding to the radial position of the recording medium to which the light beam is irradiated are provided. As a result, stable tracking detection signals and focusing detection signals are obtained, stable tracking and focusing of the optical beam is obtained, and uniform bits are formed on the recording medium 1-, and the S/N ratio of the reproduced signal is extremely high. Improved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the principle of the present invention, Fig. 2 is an explanatory diagram showing a bit string recorded on a disk, and Fig. 3 is an explanatory diagram showing the relationship between bias magnetic field and bit diameter using the disk radius as a parameter. DESCRIPTION OF EMBODIMENTS FIGS. 4 to 7 are explanatory diagrams showing each embodiment of the present invention. ■ is a (magneto-optical) disk, and 2 is a semiconductor laser. 5 is an objective lens, 10 is a bias magnetic pole device, 18 is an optical to rad portion, and 14 is a light beam irradiation device. 101 is a permanent magnet, and 102 is a sliding variable resistor. 103 is a magnetic material, 104 is a coil, and 105 is a power source. 106 is an atlas regeneration circuit, 107 is a ROM, 10
8 is a central processing unit, 109 is a variable voltage source, 110 is a guide bar, 111 is a sliding part shrine, and 12 is a permanent magnet. Patent applicant Canon Co., Ltd. Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] A disc-shaped magneto-optical recording medium is rotated at a constant angular velocity,
In the magneto-optical recording device that records on the magneto-optical recording medium by converging a modulated light beam generated from a light beam generator into a minute spot and applying an auxiliary magnetic field, the magneto-optical recording medium has a light beam irradiated portion. What is claimed is: 1. A magneto-optical recording device comprising magnetic field generating means that increases the intensity of the auxiliary magnetic field toward the outer periphery thereof.