JPH06302038A - Magneto-optical recording and reproducing device and magneto-optical disk - Google Patents

Abstract

PURPOSE:To simplify the constitution of an optical system and temp. control and to enhance the recording density in the magneto-optical recording and reproducing device using second harmonic of outgoing light of a solid-state laser excited by laser light for a light source. CONSTITUTION:Emission power of the laser light from an objective lens 5 is always kept constant to be capable of recording, and reproducing is performed by so-called magnetic super-high resolution, and after reproducing, reproduced information is temporarily held, and then based on this information, rerecording is performed by a magnetic field modulation system. Moreover, at the time of operation other than recording and reproducing, the objective lens 5 is defocused by a fixe amt., so as not to erase recorded data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus for writing / reading information with a laser beam.

[0002]

2. Description of the Related Art The recording density and recording capacity of a magneto-optical disk are governed by the diameter of a laser spot focused by an objective lens formed on a magneto-optical recording film. This laser spot diameter is K × NA / λ ( λ is the wavelength of the laser light used for the light source, NA is the numerical aperture of the objective lens, and K is a constant). Therefore, in order to increase the recording density of a magneto-optical disk, the second harmonic (hereinafter, abbreviated as SHG light) of the emitted light of the solid-state laser excited by the laser light is used as a light source for recording or recording. A method has been proposed in which the optical power is controlled by an optical modulator according to reproduction. For example, in Japanese Patent Laid-Open No. 1-138632, an optical switch composed of an electro-optical element is used as the optical modulator, and the optical power is set at the time of recording or reproduction by this optical switch, and further information is recorded. This is done by turning on and off the optical switch based on the signal. Further, in Japanese Patent Laid-Open No. 4-134640, the power of SHG light at the time of recording or reproducing is set by changing the emitted light amount of a semiconductor laser that excites a solid-state laser, and at the time of recording, an information signal to be recorded by an optical modulator. The optical power is modulated based on. In addition, JP-A-4-2631
In 47, a liquid crystal shutter is used as an optical modulator, and the amount of light transmitted through this shutter is changed to set the optical power at the time of recording or reproduction, and at the time of recording, the direction of the external magnetic field is changed based on the information signal. Is recorded at.

[0003]

However, in the above-mentioned conventional technique, since the optical modulator for modulating the optical power of the SHG light is provided, the optical system becomes complicated, the device becomes large, and the cost increases. I have a problem.

Further, in the above-mentioned second conventional example, SHG is used.
The amount of emitted light of the semiconductor laser that excites the solid-state laser is changed in order to change the optical power during recording or reproduction of light. However, if the amount of emitted light of the semiconductor laser is changed, SHG light is obtained due to temperature change. Therefore, there is a problem in that it is very difficult to obtain stable SHG light because the phase matching condition for changing the condition changes.

The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to provide a light source with SHG.
It is an object of the present invention to provide a magneto-optical recording / reproducing apparatus that uses light, can easily adjust the temperature for phase matching, and reproduces a recording magnetic domain smaller than the laser spot diameter without complicating the configuration of the optical system.

[0006]

In the magneto-optical recording / reproducing apparatus of the present invention, the second harmonic of the emitted light of the solid-state laser excited by the laser light incident thereon is used as the light source, and the laser light from the light source is emitted. In a magneto-optical recording / reproducing apparatus that projects information on a magneto-optical disk by projecting it onto a magnetic disk, the intensity of the laser beam from the light source from the objective lens is always the magneto-optical disk. It is characterized by a constant intensity that can be recorded against.

Further, in the magneto-optical recording / reproducing apparatus of the present invention, the operation of focusing the objective lens on the magneto-optical disk is performed in an area of the magneto-optical disk where information is not recorded, and recording / reproducing is performed. When the operation is performed, the distance of the objective lens from the magneto-optical disk is shifted from the focal point by a certain distance.

Further, in the magneto-optical recording / reproducing apparatus, the magneto-optical signal on the recording film of the magneto-optical disk is not erased by the distance by which the objective lens is displaced, and the pre-pit formed on the substrate of the magneto-optical disk. Is characterized by being in a reproducible range.

In the magneto-optical disk of the present invention, the minimum pit length of the track address is set to be at least 1.3 times the minimum domain length of the magneto-optical signal, and the pre-pit portion of the track address is located one track above. It is characterized in that it is provided in one place or in multiple places.

Further, the magneto-optical recording / reproducing apparatus of the present invention is characterized in that it seeks to a target track while reading the track address during a seek operation.

[0011]

EXAMPLES The present invention will be described in detail below based on examples.

(Embodiment 1) FIG. 1 is a diagram showing an embodiment of a magneto-optical recording / reproducing apparatus of the present invention.

In FIG. 1, a control circuit 1 controls the rotation of a spindle 3 for rotating a magneto-optical disk 4 at a predetermined rotation speed, and a radial direction of an optical head 2 for irradiating a target spot with a light spot from an objective lens 5. Seek operation control for moving to
The recording operation or the reproducing operation is controlled.

FIG. 2 is a diagram showing the internal structure of the optical head 2 shown in FIG. Light emitted from the semiconductor laser 21 is incident on a solid-state laser 24 of Nd: YAG via a condenser lens 22 and a mirror 23. Wavelength 1 from this solid-state laser 24
The P-polarized component of the emitted light of 064 nm is emitted by the analyzer 25 and is incident on the nonlinear optical crystal 26 of KTiPO ₄ . Laser light containing a component of wavelength 532 nm is emitted from the nonlinear optical crystal 26, and laser light of 532 nm is transmitted by a mirror 27 that transmits only wavelength 532 nm. Here, the semiconductor laser 21, the condenser lens 22, the mirror 23, the solid-state laser 24, the analyzer 25, the nonlinear optical crystal 26, and the mirror 27 are attached to the temperature control means 37 using a Peltier element, but in the present embodiment, the semiconductor is used. Since the optical power output of the laser 21 is always constant,
Since there is no sudden temperature change of the semiconductor laser 21 and the temperature control only needs to be performed with respect to the change of the ambient temperature, it becomes easy to keep these optical systems at a predetermined temperature by the temperature control means 37. The 532 nm laser light transmitted through the mirror 27 is collimated by the collimator lens 28, and is focused on the recording film of the magneto-optical disk 4 by the objective lens 5 via the deflection beam splitter 29. At the time of recording, the recording data 11 is sent to the magnetic head drive circuit 13 by the switch 12, and recording is performed by modulating the magnetic field applied to the magnetic head 6 based on this data. At the time of reproduction, the reflected light from the magneto-optical disk 4 is incident on the deflected beam splitter 31 via the objective lens 5, the deflected beam splitter 29 and the half-wave plate 30, and the transmitted light and the reflected light thereof are collected by the condenser lens 32. , 33 and photodetector 34,
The reproduction signal 8 is obtained by condensing on the light source 35 and detecting the difference between the outputs of the photodetectors 34 and 35 by the differential amplifier 36. In the present invention, since the optical power emitted from the objective lens 5 is always constant, the recorded data is erased after reproduction. Therefore, in FIG. 1, the reproduced signal 8 is converted into a digital signal by the binarization circuit 9, and the digital signal is held in the temporary storage device 10. Then, after the reproduction operation is completed, re-recording is performed in the same manner as the recording described above.
At this time, as the data sent to the magnetic head drive circuit 13, the data held in the temporary storage device 10 is selected by the switch 12. As a result, the magneto-optical disk 4
The data recorded in is not erased after reproduction.

In addition to the recording or reproducing operation, the magneto-optical recording / reproducing apparatus has a seek operation for moving to a target address on the magneto-optical disk 4 and a pause operation for waiting on a certain track. When the light spot condensed by the objective lens 5 is focused on the recording film of the magneto-optical disk 4 at the time of the operation of, the data will be recorded when the light spot passes over the previously recorded data. Erase it. Therefore, during these seek or pause operations, the recorded data is not erased, and the pre-pit information such as the address may be defocused within the range in which it can be reproduced. In the present invention, during a seek or pause operation, the recorded data is obtained by adding an offset to the focus actuator 7 of the objective lens 5 in FIG. 1 to bring the objective lens 5 away from the magneto-optical disk 4 by 3 μm or away. Was not erased and the pre-pit information could be reproduced. The operation sequence of this magneto-optical recording / reproducing apparatus is shown below. First, 1) the spindle 3 is rotated so that the magneto-optical disk 4 has a predetermined rotation speed, and 2) the objective lens 5 is moved to an innermost area of the magneto-optical disk 4 where data is not recorded, so that the laser light is emitted. Emit and apply focus servo 3)
The objective lens 5 is moved toward or away from the magneto-optical disc 4 by 3 μm or away from the magneto-optical disc 4 for defocusing. 4) When a seek command is received, first move to a certain track, read the track address, and using this as a reference, the track is traversed by the difference from the target track, and seek is performed. 5) When the target address is reached, the light spot condensed by the objective lens 5 is focused on the recording film, and the recording operation or the reproducing and re-recording operation is performed. It will be in focus and wait until the next operation command arrives.

FIG. 5 shows the magneto-optical disk 4 used in this embodiment.
It is a sectional view of FIG. Polycarbonate substrate 51
An AlSiN ceramic layer 52 and an NdDyFeCo magnetic thin film 5 having an easy axis of magnetization in a direction perpendicular to the film surface.
3, an AlSiN ceramic layer 54, and an AlTi reflective layer 55 are laminated in this order by magnetron sputtering, and a protective film 56 is spin-coated on the 86 mm type magneto-optical disk. A track groove having a pitch of 1 μm for tracking servo and pre-pits in which an address and the like are recorded are formed on the surface. The minimum pit length of this pre-pit is equal to the minimum domain length of the signal recorded on the magneto-optical disk 4.
FIG. 6 shows the measurement results of the recording power dependence of C / N of this magneto-optical disk 4. However, the rotation speed is 1800 rpm at a position with a radius of 30 mm, and ± 200 O at 7 MHz.
Recording was performed by modulating the magnetic field of e, and the reproduction power was measured at 1 mW. From FIG. 6, the optical power emitted from the objective lens 5 was set to 4 mW, which is sufficient for recording.

FIG. 3 shows the results of measuring the recording frequency dependence of the C / N of the magneto-optical disk 4 when the reproducing power was set to 4 mW of the present invention and when the reproducing power was set to 1 mW as a comparative example. In FIG. 3, the recording frequency is 7 MH
Below z, C / N is higher when playback power is 1 mW
However, when the recording frequency is 8 MHz or higher, a higher C / N is obtained when the reproducing power of the present invention is 4 mW.
The highest C / N of 49 dB when the recording frequency is 10 MHz
was gotten. This is due to the magnetic super-resolution effect, and this principle will be described with reference to FIG.

In FIG. 4, the laser spot 42 passes over the recording magnetic domain 41 as the magneto-optical disk 4 rotates. If the intensity of the reproducing light is increased during the passage, the magneto-optical recording film is formed due to the temperature rise. There is a region 43 where the magnetization is lost or the Kerr rotation angle of the reflected light becomes almost zero. At this time, since the reflected light from this area 43 does not have magneto-optical information, this area 43 is masked. On the other hand, the temperature of the magneto-optical recording film does not rise in the area other than the masked area of the laser spot 42, and the reflected light from this area has magneto-optical information. Therefore, since only a part of the laser spot 42 contributes to the reproduction of the magneto-optical signal, it is possible to detect a recording magnetic domain smaller than the laser spot 42.

When recording and reproduction were performed on the magneto-optical disk 4 by the magneto-optical recording / reproducing apparatus having the above-mentioned structure, good recording / reproducing without deterioration could be performed.
Further, even when performing a seek or pause operation, the recorded data was not erased, and the functions required of the magneto-optical recording / reproducing apparatus were sufficiently satisfied.

(Embodiment 2) In this embodiment, another embodiment of re-recording after reproduction in Embodiment 1 will be described with reference to FIGS. 1 and 7.

In FIG. 7, the magneto-optical recording film after passing through the laser spot 42 has a laser spot 4 even if the temperature drops.
It does not always return to the direction of magnetization before passage of 2. But,
When a magnetic field is applied from the outside to a portion 44 of the masked portion 43 where the temperature is decreased in the traveling direction of the laser spot 42 due to the temperature rise, in the same direction as the magnetization direction of the recording magnetic domain before reproduction, magnetic field modulation is performed. The reproduced signal can be recorded again in the same manner as the recording by the method. That is, in FIG. 1, the reproduced signal 8 is converted into a digital signal by the binarization circuit 9, and this digital signal is stored in the temporary storage device 10.
The magnetic head driving circuit 13 drives the magnetic head 6 based on the data after delaying the position of the reproduced recording magnetic domain 41 to 44 by the rotation of the disk. Data can be recorded again on the magneto-optical disk by applying it to the position. Therefore, repetitive reproduction can be performed without erasing data during reproduction. In this case, since reproduction and re-recording are performed at the same rotation of the magneto-optical disk, there is no increase in reproduction time due to re-recording as in the first embodiment. When recording and reproducing were performed on the magneto-optical disk 4 with the magneto-optical recording / reproducing apparatus having the above-described structure, good recording / reproducing could be performed without deterioration.

(Embodiment 3) FIG. 8 is a diagram showing an embodiment of the magneto-optical disk of the present invention.

In FIG. 8, on the substrate of the magneto-optical disk 4, there are one or a plurality of pre-pit areas 81 in which only track address information is recorded on one track. The minimum pit length of this portion is the magneto-optical disc. It should be at least 1.3 times larger than the minimum domain length of the signal. If this magneto-optical disk 4 is applied to the magneto-optical recording / reproducing apparatus described in the first embodiment, the track address can be read when the light spot passes through this area 81 as the disk rotates during the seek operation. Therefore, unlike the seek operation described in the first embodiment, it is not necessary to move to a certain reference track at the start of the seek operation, and high-speed seek operation can be performed. The operation sequence of the magneto-optical recording / reproducing apparatus using this magneto-optical disk 4 is shown below. First, 1) rotate the spindle 3 so that the magneto-optical disk 4 has a predetermined rotation speed, and 2) objective lens 5
Is moved to an innermost peripheral area of the magneto-optical disk 4 where data is not recorded, laser light is emitted, focus servo is applied, and 3) the objective lens 5 is moved from the magneto-optical disk 4 to 3 μm.
m Defocus by moving closer or further away. 4) The objective lens 5 is moved in the radial direction to seek the target address while reading the track address. 5) When the target address is reached, the light spot condensed by the objective lens 5 is focused on the recording film, and the recording operation or the reproducing and re-recording operation is performed. It will be in focus and wait until the next operation command arrives.

Good recording and reproduction can be performed by the magneto-optical disk and the magneto-optical recording and reproducing apparatus described above.
A faster seek operation was realized.

The present invention should not be considered to be limited to these examples, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-mentioned embodiment, the track groove for the tracking servo is formed on the substrate of the magneto-optical disk, but there is no problem even if the wobble pit is formed instead of the track groove and the tracking servo is performed by the sample servo system. Absent.

[0026]

As described above, according to the present invention, when the second harmonic of the emitted light of the solid-state laser excited by the laser beam is used as the light source, the recording / reproducing can be performed without complicating the optical system. It is possible to simplify the temperature control of the optical system, and since it is possible to reproduce the recording magnetic domain smaller than the laser spot diameter, it is possible to increase the density of magneto-optical recording. Further, if the magneto-optical disk of the present invention is used, high speed seek is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magneto-optical recording / reproducing apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing an internal configuration of an optical head 2 in FIG.

FIG. 3 shows a reproducing power of 4 mW and 1 m for the magneto-optical disk 4.
It is a figure showing the result of having measured the recording frequency dependence of C / N at the time of reproducing on W.

FIG. 4 is a diagram showing a state when reproducing light passes over a recording magnetic domain on the recording film of the magneto-optical disk 4.

5 is a diagram showing a cross-sectional view of the magneto-optical disk 4. FIG.

FIG. 6 is a diagram showing a result of measurement of recording power dependency of C / N of the magneto-optical disk 4.

FIG. 7 is a diagram showing a state in which reproducing light passes on a recording magnetic domain on the recording film of the magneto-optical disk 4.

FIG. 8 is a diagram showing a magneto-optical disk according to an embodiment of the present invention.

[Explanation of symbols]

1 Control Circuit 2 Optical Head 3 Spindle 4 Magneto Optical Disk 5 Objective Lens 6 Magnetic Head 7 Focus Actuator 8 Playback Signal 9 Binarization Circuit 10 Temporary Storage Device 11 Recorded Data 12 Switch 13 Magnetic Head Drive Circuit 21 Semiconductor Laser 22 Condensing Lens 23, 27 Mirror 24 Solid-state laser 25 Analyzer 26 Non-linear optical crystal 28 Collimator lens 29, 31 Deflection beam splitter 30 1/2 wavelength plate 32, 33 Condensing lens 34, 35 Photodetector 36 Differential amplifier 41 Recording magnetic domain 42 Laser Spot 43 The magneto-optical recording film lost its magnetization due to a temperature rise when passing the laser spot, or the rotation angle of the linearly polarized light was almost zero due to the magneto-optical effect of the reflected light from the magneto-optical recording film of the reproducing light. Part 44 A portion where the reproduced signal is later re-recorded 51 Polycarbonate substrate 52, 54 AlSiN ceramic layer 53 NdDyTbFeCo magnetic thin film having an axis of easy magnetization in the direction perpendicular to the film surface 55 AlTi reflective layer 56 Protective film 81 Only track address information Pre-pit area where is recorded

Claims (5)

[Claims] 1. A light source is the second harmonic of the emitted light of a solid-state laser that is excited by entering laser light, and the laser light from the light source is projected onto a magneto-optical disk by an objective lens to produce the light. In a magneto-optical recording / reproducing apparatus for recording / reproducing information on / from a magnetic disk, the intensity of the laser beam of the light source from the objective lens is always a constant intensity that can be recorded on the magneto-optical disk. Magneto-optical recording / reproducing device. 2. The magneto-optical recording / reproducing apparatus according to claim 1, wherein the operation of focusing the objective lens on the recording film of the magneto-optical disk is performed in an area of the magneto-optical disk where no information is recorded, and recording is performed. The magneto-optical recording / reproducing apparatus is characterized in that, when an operation other than reproduction is performed, a distance of the objective lens from the recording film of the magneto-optical disk is shifted from a focal point by a certain distance. 3. The magneto-optical recording / reproducing apparatus according to claim 2, wherein the magneto-optical signal on the recording film of the magneto-optical disk is not erased by the distance by which the objective lens is displaced, and the substrate of the magneto-optical disk. A magneto-optical recording / reproducing device characterized in that the pre-pits formed above are within a reproducible range. 4. The minimum pit length of pre-pits formed on the substrate of the magneto-optical disk constituting a track address is set to be at least 1.3 times or more the minimum domain length of the magneto-optical signal, and the track is formed. A magneto-optical disk characterized in that one or a plurality of address prepit portions are provided on one track. 5. The magneto-optical recording / reproducing apparatus according to claim 3, wherein recording / reproducing is performed on the magneto-optical disk according to claim 4, wherein the seek operation is performed while seeking the target track while reading the track address. Magneto-optical recording / reproducing device.