JPH076444A - Magneto-optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To utilize a merit dealing with both systems of optical modulation and magnetic field modulation by providing a single optical head irradiating a light beam on a magnetic field impression part of a medium, cooporating with the impressed magnetic field, recording information on the medium, detecting a reflection beam from the medium and reproducing the recorded information. CONSTITUTION:At the time of recording the information at high speed, a recording signal is impressed through a signal line L1 by the optical modulation system, and a semiconductor laser 1 is driven by a laser driver 2 according to the recording signal, and the light beam is modulated. At this time, a constant DC current flows through a coil 10 from a coil driver 11, and the magnetic field opposite to the direction where a magneto-optical recording medium 6 is magnetized previously is generated, and the magnetization is inverted by local temperature rise by a light beam irradiation part to be recorded. Further, at the time of recording the data at low speed, by switching to the magnetic field modulation system, the light beam with a fixed level is generated from the laser 1 by the driver 2 continuously, and the recording signal is applied to the driver 11 through the signal line L2, and a forward/backward conversion current flows through the coil 10 according to the recording signal, and alternate magnetic field is generated to be recorded. The system is used regardless of the presence of the 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 recording information on a rotating disk-shaped magneto-optical recording medium by using a light beam.

[0002]

2. Description of the Related Art In a conventional magneto-optical recording / reproducing apparatus (also referred to as a magneto-optical disk apparatus), a magnetic field and a light beam are generally applied to a magnetic thin film such as Gd.TbFe or Cd.Co to change the direction of magnetization. Thus, when recording and reproducing an information signal, when irradiating linearly polarized laser light on the magnetic thin film and reflecting or transmitting it, the vibrating surface of the linearly polarized light due to the magnetic Kerr effect or the Faraday effect is magnetized. The recording signal is read by utilizing the rotation according to the direction. The rotation of the light reflected on the surface of the medium is called the magnetic Kerr effect, and the rotation of the transmitted light is called the Faraday effect.

In particular, the magneto-optical recording / reproducing device has many advantages such as extremely large capacity, capable of writing and reproducing at high speed, and erasing / reproducing / writing like a VTR or a magnetic disk. Therefore, it is expected as a recording device for image information.

As described above, as a method of writing a recording signal (data) in the magneto-optical recording / reproducing apparatus, two methods are conventionally known. First, as a first recording method, there is a method of storing information by irradiating a disk surface made of a magnetic thin film with a laser beam modulated according to a recording signal. In this case, generally, an unmodulated magnetic field is applied to the disk surface at the same time as the irradiation of the laser beam to increase the magnetization sensitivity of the disk, thereby enabling recording with a relatively weak laser beam. However, it is needless to say that recording can be performed if the laser beam is strong, without applying such a magnetic field. Below, this first
This recording method is called an optical modulation method.

As a second recording method, an unmodulated light beam is applied to a disk surface made of a magnetic thin film,
At the same time, there is a method of applying a magnetic field modulated according to a recording signal. By making the magnetic field applied at that time a weak magnetic field that cannot be recorded with its own magnetic field strength, information can be accurately recorded only in the portion irradiated with the light beam. The magnetic field is generated by passing a current through a coil arranged near the recording unit according to a recording signal. Hereinafter, this second recording method will be referred to as a magnetic field modulation method.

In the conventional magneto-optical recording / reproducing apparatus, either one of the above-mentioned two recording methods is used. Comparing the above two recording methods, the optical modulation method is more suitable for performing extremely high-speed and high-density recording.

In the magnetic field modulation method, a high-speed recording signal must be given to the coil, but it is difficult to give a high-speed signal because the coil has a predetermined inductance. However, in the light modulation method,
When the recorded data of the already recorded portion is polarized, there are the following drawbacks.

That is, in the light modulation method, new data cannot be directly written in the already recorded portion, but it is necessary to erase the recorded portion once and then write new data. Therefore, two steps of erasing and rewriting are required to change the data.

[0009]

As described above, none of the conventional magneto-optical recording / reproducing apparatuses have the advantages of the optical modulation method and the magnetic field modulation method.

Since the present invention has been made in view of the above points,
It is an object of the present invention to provide a small-sized magneto-optical recording / reproducing apparatus that makes the most of the advantages of the optical modulation method and the magnetic field modulation method.

[0011]

In order to achieve the above object, the present invention provides a magneto-optical recording / reproducing apparatus for recording information on a rotating disk-shaped magneto-optical recording medium by using a light beam. On the medium by applying a light beam to the magnetic field applying means for switching the modulated magnetic field and a constant magnetic field to apply to the medium, and a magnetic field applying part of the medium by the magnetic field applying means in cooperation with the applied magnetic field. And a single optical head that reproduces the information recorded on the medium by detecting the reflected light from the medium.

[0012]

In the present invention, since the optical head is not provided independently for each of the optical modulation method and the magnetic field modulation method, when reading the recorded information, the information can be read by a single optical head. It is not necessary to separately provide an optical head for each of the above two methods.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a magneto-optical recording / reproducing apparatus of the present invention, in which 1 is a semiconductor laser which emits a laser beam, and 2 is a laser driver which drives the semiconductor laser 1. The driver 2 modulates the laser beam according to the recording signal supplied through the signal line L1. Reference numeral 3 is a collimator lens for collimating a laser beam emitted from the semiconductor laser 2 into a parallel light beam, 4 is a reflecting mirror for changing the optical path of the laser beam, and 5 is an objective lens for condensing the laser beam in a spot shape.

Reference numeral 6 denotes a disk-shaped magneto-optical recording medium (magneto-optical disk), the recording surface of which is Gd.TbFe or C.
A laser beam spot formed of a magnetic thin film such as dCo and focused by the objective lens 5 is irradiated. Reference numeral 7 is a drive motor for driving the magneto-optical recording medium 6 at a predetermined rotation speed. 8 is a half mirror that is interposed between the reflection mirror 4 and the collimator lens 3 to split the reflected light of the laser beam reflected on the magneto-optical recording medium 6, and 9 is the above-mentioned reflected light that has passed through the half mirror 8. This is a focus detection optical system that receives light and detects the focus state thereof. The focus detection optical system 9 has, for example, a condenser lens, a wave plate (polarizing plate), and a light receiving element (photoelectric conversion element) such as a CCD.

Further, 10 is a magnetic field generating coil for applying a magnetic field to the irradiation position of the light beam on the magneto-optical recording medium 6, 11 is a coil driver for driving this magnetic field generating coil 10, and the coil driver 11 is a signal line L2. The magnetic field of the coil 10 is modulated according to the recording signal supplied through the.

Next, the operation will be described. The semiconductor laser 1
The light beam emitted from passes through the collimator lens 3, the mirror 4, and the objective lens 5 and is imaged on the magneto-optical recording medium 6 in a spot shape having a diameter of about 2 μm. A part of the reflected light on the surface of the magneto-optical recording medium 6 is guided to the focus detection optical system 9 by the half mirror 8 and the optical signal of the optical system 9 receives the error signal of the distance between the objective lens 5 and the magneto-optical recording medium 6. The objective lens 5 is moved in the vertical direction according to this error signal to accurately form a spot on the magneto-optical recording medium 6.

A magnetic field generating coil 10 is provided in the vicinity of the objective lens 5 as shown in the drawing, while the magneto-optical recording medium 6 is driven by a motor 7 to, for example, 1800 rpm. p. It is rotated by m. Furthermore, a semiconductor laser 1, an optical system 3,
The coils 4, 5, 8, 9 and the coil 10, etc. are housed in a housing (not shown), and are integrally movable in the radial direction of the magneto-optical recording medium 6 as a recording / reproducing head.
Thereby, the recording data can be written in any position of the magneto-optical recording medium 6.

With the above structure, when recording information at a high speed, an optical modulation method is adopted to apply a recording signal through the signal line L1, and the laser driver 2 drives the semiconductor laser 1 in accordance with the recording signal. , Modulate the light beam. At this time, a constant DC current may be passed through the coil 10 from the coil driver 11 to generate a magnetic field in the direction opposite to the direction in which the magneto-optical recording medium 6 is magnetized in advance. It is not necessary to energize the driver 11. As a result, the temperature of the portion hit by the light beam locally rises, the magnetization is inverted, and the signal is recorded.

The magneto-optical recording medium 6 recorded in this way
When the above recording signal is erased, a direct current having a polarity opposite to that described above is applied to the coil driver 2 to generate a magnetic field in the same direction as the pre-magnetized direction, that is, a direction opposite to the recording pit, by the coil 10. The recording signal is erased by irradiating a constant light beam at the same time. in this way,
In order to perform recording by the optical modulation method and rewrite the already recorded portion (recording pit), it is necessary to erase the recording signal in advance.

On the other hand, when recording relatively low-speed data (for example, the above-mentioned management information), switching to a magnetic field modulation method is performed by a switching means (not shown), and a laser driver 2 emits a light beam of a certain level from the laser 1. A current is generated continuously, and at the same time, a recording signal is applied to the coil driver 11 through the signal line L2, and the coil driver 11 generates a current for converting the current in the forward and reverse directions according to the recording signal.
0 is energized to generate an alternating magnetic field according to the recording signal. As a result, the part where the light beam hits is
The direction of magnetization is reversed and information is recorded. When recording with this magnetic field modulation method, it is possible to record regardless of whether or not there is already recorded data in the recording portion,
There is no need to erase recorded information.

As described above, in this embodiment, one device can both record main information such as image information at high speed and rewrite auxiliary information such as management information that may be low speed without erasing. This makes it extremely convenient in practice. When actually used, it is preferable to record the data to be recorded at high speed and rewrite the management information at low speed accordingly.

In particular, when reading the recorded information,
This can be performed by a single optical head, and it is not necessary to provide an optical head independently for each of the above-mentioned two methods. However, it is needless to say that the demodulation of the modulated signal needs to be performed according to the modulation method at the time of recording of each method.

Further, it is effective to divide the areas of the portions to be recorded by the two recording methods according to the present embodiment into the recording medium 6 and divide them according to the recording methods and set them in advance. In this case, the inner central portion of the recording medium 6 may be assigned to the magnetic field modulation method and the outer vicinity of the recording medium 6 may be assigned to the light modulation method.

That is, the limit of the recording speed in the light modulation system is limited by the size of the recording pit on the recording medium 6. That is, it is necessary to record the recording pits formed in accordance with the recording signal within a range that is surely formed independently. Therefore, when the recording medium 6 is rotating at a constant number of revolutions, the linear velocity is higher toward the outer side of the recording medium 6 and high-speed recording becomes possible. On the other hand, in the magnetic field modulation method, the recording speed is limited by the inductance of the coil 10. That is, it is difficult to change the current flowing through the coil 10 at high speed due to the inductance of the coil 10.
This limits the recording speed. Therefore, the upper limit of the recording density is almost unchanged regardless of whether the recording medium 6 is at the inner center or the outer periphery.

Therefore, by setting the portion to be recorded by the magnetic field modulation method inside the recording medium 6, it is possible to record more data on one recording medium 6. Even when the number of revolutions of the motor 7 is changed according to the portion to be recorded, the variable range of the number of revolutions of the motor 7 can be made smaller by dividing and setting the recording area as described above. There is also an advantage that can be done.

[0027]

As described above, according to the present invention,
Since an optical head is not provided independently for each of the optical modulation method and the magnetic field modulation method, it is possible to realize a small-sized magneto-optical recording / reproducing device that makes the most of the advantages of the optical modulation method and the magnetic field modulation method. it can.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Semiconductor Laser 2 Laser Driver 3 Collimator Lens 4 Reflection Mirror 5 Objective Lens 6 Magneto-Optical Recording Medium 7 Motor 8 Half Mirror 9 Focus Detection Optical System 10 Coil 11 Coil Driver L1, L2 Signal Line

Claims (1)

[Claims] 1. A magneto-optical recording / reproducing apparatus for recording information on a rotating disk-shaped magneto-optical recording medium by using a light beam, wherein a magnetic field modulated according to information and a constant magnetic field are switched to the medium. A light beam is applied to the magnetic field applying unit to be applied and the magnetic field applying unit of the medium by the magnetic field applying unit to record information on the medium in cooperation with the applied magnetic field and detect reflected light from the medium. A magneto-optical recording / reproducing device comprising a single optical head for reproducing information recorded on the medium.