JPH04344352A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide the magneto-optical recording and reproducing device which allows recording at higher densities by using light of a super resolution only at the time of reproduction. CONSTITUTION:This device has a liquid crystal shutter 14 which is provided in the mid-way of the optical path of a laser beam and selectively executes the shutting-off of at least the central part of the section orthogonal with the optical axis of this light and the release of this shutting off and a liquid crystal shutter driving part 3 which operates the liquid crystal shutter 14 so as to execute the above-mentioned shutting off in the case of reproduction of information and to release the shutting off in the case of recording of the information. A magneto-optical disk is irradiated with the laser beam of the super resolution by the above-mentioned shutting off in the case of reproduction of the information.

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 and reproducing apparatus for recording and reproducing information.

0002

[Prior Art] As a method for performing overwrite recording in a magneto-optical disk device for recording and reproducing information,
There is magnetic field modulation recording in which information is recorded by irradiating a magneto-optical disk with a laser beam and changing the direction of a magnetic field applied to the magneto-optical disk. On the other hand, information is reproduced by irradiating the magneto-optical disk with a laser beam and detecting the rotation angle of the polarization direction of the light reflected from the magneto-optical disk.

[0003] When performing magnetic field modulation recording, it is known that as the magnetic field modulation frequency is increased, the length of recording bits becomes shorter and the recording density of information can be increased. However, even if the magnetic field modulation frequency is increased and the recording density is increased, the spot diameter of the conventional laser beam for reproduction cannot be made smaller to accommodate such an extremely short recording bit length, and the recording density densification was limited by the spot diameter of the laser beam.

[0004] In order to achieve higher recording density,
The spot diameter of the laser beam for reproduction must be made smaller. One possible method for reducing the spot diameter is to use super-resolution. It is known that by reducing the transmittance at the center of the aperture of a circular aperture optical system, an extremely small point image can be obtained. This is called super resolution. By utilizing such super-resolution and making the spot diameter of the laser beam for reproduction extremely small,
Information recorded in an extremely short recording bit length can be reproduced.

[0005]

[Problem to be Solved by the Invention] However, it is known that the above-mentioned super-resolution laser beam has side peaks with low intensity in addition to its main peak in its point spread intensity distribution. . In a magneto-optical disk device that uses a laser beam during recording and reproduction, when such a super-resolution laser beam is used during recording,
Since a super-resolution laser beam has multiple peaks, the intensity of the main peak relative to the output of the laser beam is relatively small, so there is a problem that the heating energy required during recording cannot be obtained sufficiently. When increasing the main peak intensity by increasing the laser beam output to obtain more heating energy, the side peak intensity also increases accordingly, and this side peak records information in unnecessary locations. There was a problem that there was a risk.

The present invention was made to solve these problems, and by using a super-resolution laser beam only during reproduction, it is possible to increase the recording density. The purpose of the present invention is to provide a magneto-optical recording/reproducing device that achieves the following.

[0007]

[Means for Solving the Problems] A magneto-optical recording/reproducing device according to the present invention is provided in the middle of an optical path of light irradiated onto a disk, and is orthogonal to the optical axis of the light in order to obtain super-resolution light. means for shielding at least a central portion of a cross section and releasing the shielding; and operating the means to perform the shielding when reproducing information and release the shielding when recording information. When information is to be reproduced, super-resolution light is irradiated onto the disc by the shielding, while when information is to be recorded, non-super-resolution light is irradiated onto the disc. irradiate.

[0008]

[Operation] When reproducing information, at least the center of the cross section perpendicular to the optical axis of the light irradiated onto the disc is shielded.
Super-resolution light is obtained by the optical diffraction phenomenon caused by this shielding, and this light is irradiated onto the disk. Since the spot diameter of super-resolution light is extremely small, high-density recorded information can be reproduced. On the other hand, when recording information, the shielding is released and the disc is irradiated with non-super-resolution light that has a large amount of thermal energy, but by increasing the frequency of the external magnetic field applied to the disc, Information is recorded with high density. In this way, since high-density recorded information can be reproduced by super-resolution light, when recording information, it is necessary to record information at a high density that can be reproduced by the super-resolution light. becomes possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording and reproducing apparatus according to the present invention will be specifically described below with reference to drawings showing embodiments thereof.

FIG. 1 is a block diagram showing the configuration of a magneto-optical disk device which is an example of a magneto-optical recording and reproducing device according to the present invention. A magneto-optical disk has a large number of concentric or spiral recording tracks. A magnetic head 2 equipped with an electromagnetic coil that determines the direction of magnetization of the magneto-optical disk 1 is disposed facing one side of the magneto-optical disk 1, and an optical head 2 is provided at a position on the other side facing the magnetic head 2. an optical head 10 equipped with an optical system that irradiates a laser beam onto a magnetic disk 1 and reads and writes data on the magneto-optical disk 1;
is installed. Further, the optical head 10 is configured to access all the track grooves of the magneto-optical disk 1 by a driving means (not shown).

The optical system has the following configuration. That is, in the emission direction of the semiconductor laser 11 as a light source, there is a collimator lens 12 for collimating the laser beam emitted from the semiconductor laser 11 at a predetermined radiation angle, and the cross-sectional shape of the laser beam perpendicular to its optical axis is approximately A shaping prism 13 that shapes the laser beam into a circular shape, selectively shields and releases a part of the cross section perpendicular to the optical axis of the laser beam, and only when the part is shielded, the laser beam A liquid crystal shutter 14 that converts the image into a super-resolution laser beam.
A beam splitter 15 for separating a beam incident on the magneto-optical disk 1 from a beam reflected therefrom is sequentially arranged. In the transmission direction of the beam splitter 15,
A second beam splitter 16 is provided to separate the beam incident on the magneto-optical disk 1 from the beam reflected therefrom. An objective lens 17 is disposed in the transmission direction of the beam splitter 16 to focus the laser beam incident on the magneto-optical disk 1 into a spot of a predetermined diameter.

A cylindrical lens 18 for condensing the reflected beam and a beam splitter 19 for separating the reflected beam into transmission and reflection directions are provided in the reflection direction of the beam splitter 15. Also, in the transmission direction of the beam splitter 19, there is a shielding plate 20 that shields a part of the reflected beam.
A photodiode 21 is provided which receives the reflected beam partially shielded by the shielding plate 20 on a plurality of light receiving surfaces and detects a focus error, and a beam splitter 19.
In the reflection direction, the reflected beam is received by multiple light receiving surfaces,
A photodiode 21 is provided to detect tracking errors.

In the reflection direction of the beam splitter 16, there are a lens 23 for condensing the reflected beam, and a slit 24 for passing only the main peak portion, which will be described later, in the intensity distribution of the reflected beam condensed by the lens 23. , a lens 25 that condenses the reflected beam passing through the slit 24, and a polarization plane of the reflected beam condensed by the lens 25 as 45.
A λ/2 plate 26 that is rotated by .degree. and a polarizing beam splitter 27 that transmits and reflects reflected beams depending on the plane of polarization are sequentially arranged. In the transmission direction and the reflection direction of the polarizing beam splitter 27, the reflected beam is received by a light receiving surface,
Photodiodes 28 and 29 are provided, respectively, for reproducing the data recorded in the recording pits based on the intensity of the light amount due to the difference in the rotation angle of the polarization plane of the received reflected beam.

Further, the liquid crystal shutter 14 is driven by a liquid crystal shutter driving section 3. The liquid crystal shutter drive unit 3 is configured to receive a shutter drive signal from a control unit (not shown) of the magneto-optical disk device to instruct the drive of the liquid crystal shutter 14 only when performing reproduction. The liquid crystal shutter driving section 3 forms a light shielding image as shown in FIG. 2 on the display surface of the liquid crystal shutter 14 in order to super-resolve the laser beam only when the shutter driving signal is applied. When the shutter drive signal is not applied, the image is not formed.

FIG. 2 is a front view of the liquid crystal shutter 14 showing a light shielding image formed on the display section of the liquid crystal shutter 14. As shown in FIG. The cross section of the laser beam b incident on the liquid crystal shutter 14 perpendicular to its optical axis is circular as shown in this figure. When super-resolving the laser beam b, a light-shielding image of a predetermined width is placed on the square display surface of the liquid crystal shutter 14, connecting the centers of each of a pair of opposing sides of the display surface. A is formed. However, this light-shielding image A is formed with the radial direction of the magneto-optical disk 1 as its longitudinal direction.

Generally, a super-resolution laser beam is obtained by lowering the transmittance at the center of the aperture of a circular aperture optical system. The light-shielding image A is formed so as to pass through the center of the cross section of the laser beam b, and the center of the cross-section perpendicular to the optical axis of the laser beam b is thereby shielded, resulting in a super-resolution laser beam. becomes.

Next, the operation of the magneto-optical disk device configured as described above will be explained. The operation will be explained. When recording information on the magneto-optical disk 1, the light-shielding image A is not formed on the liquid crystal shutter 14, and the optical head 1
From 0, the same laser beam as before is applied to the magneto-optical disk 1.
is irradiated onto the disc surface. When recording information, information is recorded on the magneto-optical disk 1 by continuously irradiating the disk surface with a laser beam from the optical head 10 to heat the disk surface and determining the direction of magnetization with the magnetic head 2. recorded.

On the other hand, when reproducing information recorded on the magneto-optical disk 1, a light-shielding image A is formed on the liquid crystal shutter 14, and a super-resolution laser whose spot diameter is extremely small is emitted from the optical head 10. The beam is irradiated onto the disk surface of the magneto-optical disk 1. When reproducing information, a super-resolution laser beam is continuously irradiated from the optical head 10 onto the disk surface, and the reflected beam is transmitted to the photodiode 21.
, 22 and photodiodes 28, 29.

FIG. 3 is a graph showing the intensity distribution of a super-resolution laser beam, with the vertical axis representing the intensity of the super-resolution laser beam and the horizontal axis representing the distance from the center of the laser beam. The relationship is shown. This intensity distribution is such that sub-peaks S, S exist on both sides of the main peak M. The photodiodes 28 and 29 have
Due to the effect of the slit 24, only the main peak M in the intensity distribution of the reflected beam is detected. The DC component of the amount of light incident on the photodiodes 28, 29 is equal for both light fluxes, and the AC component due to the rotation of the polarization plane, which is a reproduced signal, is the same as that of the photodiodes 28, 29.
9, they appear in opposite phases to each other. Therefore, by obtaining differential signals from the photodiodes 28 and 29 using a differential amplifier (not shown), a reproduced signal corresponding to the recorded pit can be obtained.

Further, a focus error is detected in the photodiode 21, and focus control of the laser beam spot is performed based on this detection result. This focus error detection method is called the knife edge method. A tracking error is detected by the photodiode 22, and tracking control of the laser beam spot is performed based on this detection result.

In the above embodiment, an example was explained in which the detection of information recorded on the magneto-optical disk 1 and the detection of focus error and tracking error are performed using different optical systems. These detections may be performed using a single optical system. FIG. 4 is a block diagram of a magneto-optical disk device showing another embodiment of the present invention. In FIG. 4, the same numbers as in FIG. 1 are given to the same parts, and the description thereof will be omitted.

4 differs from FIG. 1 in that there is no beam splitter 15 and an optical system for its reflection direction, and a prism 30 is attached to the transmission direction surface of the polarization beam splitter 27. A photodiode 31 is provided in the direction of reflection of the polarizing beam splitter 27 to detect the strength of the light quantity and focus error due to differences in the rotation angle of the polarization plane of the reflected beam. A photodiode 32 is provided for detecting the intensity of the light amount and tracking errors due to differences.

In the magneto-optical disk device configured as described above, the DC component of the amount of light incident on the photodiodes 31 and 32 is equal to the two luminous fluxes, and the AC component due to the rotation of the polarization plane, which is a reproduced signal, is the same as that of the photodiodes 31 and 32. 3
2, they appear in opposite phases to each other. Therefore, by obtaining differential signals from the photodiodes 31 and 32 using a differential amplifier (not shown), a reproduced signal corresponding to the recorded pit can be obtained. Along with this, the photodiode 31
The focus error is detected by the wedge prism method, and the focus control of the laser beam spot is
This is done based on this detection result. Photodiode 32
A tracking error is detected from , and tracking control of the laser beam spot is performed based on this detection result.

Although the present invention uses a super-resolution laser beam during reproduction in a magnetic field modulation type magneto-optical disk device, this super-resolution laser beam can also be applied to a light modulation type optical disk device. . FIG. 5 is a block diagram showing the configuration of a light modulation type optical disc device to which the present invention is applied. Components in FIG. 5 that are the same as those in FIG. 1 are given the same numbers, and their explanations will be omitted. The difference between FIG. 5 and FIG. 1 is that the magnetic head 2 is not present, and the other configurations are the same as the magneto-optical disk device of FIG. 1. The operation of this optical disk device during reproduction is the same as that of the magneto-optical disk device shown in FIG. 1, while during recording, information is stored by optical modulation.

In this embodiment, the light-shielding image formed on the liquid crystal shutter 14 is strip-shaped; however, it is not limited to this, and may have a shape as shown in FIG. 6. FIG. 6 is a front view of the liquid crystal shutter 14 showing another example of the light-shielding image formed on the liquid crystal shutter 14. In FIG. 6, a small-diameter circular light-shielding image B is formed at the center of the display surface of the liquid crystal shutter 14 to shield the center of the cross section of the laser beam b. The laser beam is super-resolved.

[0026]

Effects of the Invention As described above, in the magneto-optical recording and reproducing apparatus according to the present invention, when reproducing information, super-resolution light is irradiated onto the disk, and the When recording information, the disc is irradiated with light that is not super-resolution, so when recording information, it is possible to reproduce information recorded with high thermal energy. High-density information can be recorded. In this way, it is possible to reproduce high-density recorded information using super-resolution light. Since the recording density can be increased, the present invention has excellent effects such as making it possible to increase the recording density of information.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a magneto-optical disk device which is an example of a magneto-optical recording and reproducing device according to the present invention.

FIG. 2 is a front view of the liquid crystal shutter showing a light-shielding image formed on a display section of the liquid crystal shutter.

FIG. 3 is a graph showing the intensity distribution of a super-resolution laser beam.

FIG. 4 is a block diagram of a magneto-optical disk device showing another embodiment of the present invention.

FIG. 5 is a block diagram showing the configuration of a light modulation type optical disc device to which the present invention is applied.

FIG. 6 is a front view of a liquid crystal shutter showing another example of a light-shielding image formed on the liquid crystal shutter.

[Explanation of symbols]

1 Magneto-optical disk 2 Magnetic head 3. Liquid crystal shutter drive section 10 Optical head 14 Liquid crystal shutter

Claims (1)

[Claims] Claim 1: Information is recorded by applying an external magnetic field to the disk and irradiating it with light; on the other hand, information is recorded on the disk by irradiating the disk with light and detecting the reflected light. In a magneto-optical recording and reproducing device for reproducing information stored in the optical system, the device is provided in the middle of the optical path of the light, and shields at least the center of a cross section perpendicular to the optical axis of the light in order to obtain super-resolution light; It is characterized by comprising means for canceling the shielding, and means for operating the means to cause the shielding to be performed when reproducing information and to cancel the shielding when recording information. Magneto-optical recording and reproducing device.