JPH04212745A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To stably carry out recording and erasing of information by providing a magnetic bias imparting device driving means maintaining distance from a magneto-optical recording medium constantly fixed according to focal differential between an objective lens and the magneto-optical recording medium. CONSTITUTION:The beams from a semiconductor laser 1 for recording and reproducing of information and a semiconductor laser 2 for erasing of information form minute optical spots for information recording and reproducing 16 and 17 by the laser 1 and the laser 2 on the same track of the magneto-optical recording medium 10 moving in the direction T with the objective lens 8 after being passed through a mirror 7 together. Transmitted beam reflected by a medium 10 makes incidence on a dichroic mirror 11, and is separated into two at a. half mirror 12, with one making incidence on a photodetector 14 after being passed through an analyzer 13, and the other makes incidence on a differential signal detection optical device 15, the focal differential and tracking differential generated with movement of the medium 10 is detected, focal control is carried out by moving an objective lens actuator 9 in the direction P after calculating this electrically and amplifying it, and tracking control is carried out by moving it in the direction Q vertical to the paper surface.

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 device capable of recording, reproducing, and erasing information.

0002

BACKGROUND OF THE INVENTION The present age is called the information age, and the technological development of high-density, large-capacity memory, which is the core of the information age, is actively being developed. In addition to the above-mentioned high density and large capacity, the capabilities required of memory include high reliability and high speed access, and optical disk memory is attracting the most attention as a device that satisfies all of these requirements. An optical disk memory is a device that optically records information on a recording medium, and recently there has been a remarkable amount of research into magneto-optical recording media and recording/reproducing devices thereof, which are capable of repeatedly erasing and recording recorded information.

Conventionally, for example, the 7th Japanese Society of Applied Magnetics Academic Conference ``Research on magneto-optical disk recording and reproducing optical systems'' (
There was a magneto-optical recording/reproducing device as shown in the system block diagram of FIG. 1 of Nakamura et al., November 1983.

[0004] The conventional magneto-optical recording and reproducing apparatus as described above will be explained below with reference to the drawings.

FIG. 2 is a schematic diagram of the main parts of a conventional magneto-optical recording and reproducing apparatus. In FIG. 2, 10 is a magneto-optical recording medium, 8 is an objective lens facing the magneto-optical recording medium 10, and 9 is an objective lens that faces the magneto-optical recording medium 10.
2 is an objective lens actuator that drives the objective lens 8 in a direction perpendicular to the magneto-optical recording medium 10 (direction of arrow P in the drawing) and in a radial direction of the magneto-optical recording medium 10 (direction of arrow Q in the drawing);
5 is one minute optical spot formed on the magneto-optical recording medium 10 by the objective lens 8, and 26 is a minute optical spot 25.
27 is an error detection block that detects a focus error and tracking error between the objective lens 8 and the magneto-optical recording medium 10; 28 is an information detection block 26, an error detection block 27, a linearly polarized light source, etc. 29 is a minute light spot 25
an electromagnet as a magnetic bias applying device that applies a magnetic field perpendicular to the magneto-optical recording medium 10 in opposite directions (in the direction of arrows M and N in the drawing) during recording and erasing of information at the position;
Reference numeral 30 denotes a moving block to which an optical head 28 and an electromagnet 29 are attached, and which moves in the radial direction of the magneto-optical recording medium 10 (in the direction of arrow R in the figure).

The operation of the conventional magneto-optical recording/reproducing apparatus constructed as described above will be explained below.

Light emitted from one linearly polarized light source within the optical head 28 passes through various optical elements and the objective lens 8, and forms one minute optical spot 25 on the magneto-optical recording medium 10. At this time, the reflected light from the magneto-optical recording medium 10 enters an error detection block 27 to detect a focus error and a tracking error, and each error signal is input into the objective lens actuator 9 after calculation and amplification. The objective lens actuator 9 moves the objective lens 8 in the direction of arrow P based on the focus error signal and in the direction of arrow Q based on the tracking error signal.
The objective lens 8 is always driven at a constant distance to the track of the magneto-optical recording medium 10. To record information, when the initial magnetization direction of the magneto-optical recording medium is in the direction of arrow N, an external magnetic field in the direction of arrow M is applied by the electromagnet 29, and a minute light spot 25 is created by intensity modulation of the linearly polarized light source. When the light intensity is at its peak, the temperature of this part is higher than the Curie point based on the characteristics of the magneto-optical recording medium.
The local magnetization is reversed in the direction of the arrow M by the position of the minute optical spot 25, and a minute magnetic domain of about several μm is formed to obtain a recorded state. While continuing this state, the moving block 30
By moving in the fixed direction of arrow R, only recording operation can be obtained continuously.

To reproduce information, a small optical spot 25 is formed without modulating the linearly polarized light source, with a light intensity lower than that for recording and erasing, and without raising the temperature to the Curie point. The micromagnetic domains in the recorded state are detected. The reflected light from the magneto-optical recording medium 10 enters the information detection block 26 to obtain the information reproduction state. At this time, the electromagnet 29 is not driven. By continuing this state and moving the moving block 30 in the direction indicated by the arrow R, only the reproduction operation can be obtained continuously.

Information is erased by applying an external magnetic field in the direction of arrow N, which is the opposite direction to that during recording, using the electromagnet 29, and without modulating the linearly polarized light source. When the temperature of the light spot 25 reaches the Curie point or higher, the minute magnetic domain, which is in the recorded state with the magnetization direction M, is reversed to the initial magnetization direction N, and an erased state is obtained. If this state is continued and the moving block is moved in a fixed direction in the direction of arrow R, it is possible to continuously perform an operation of only erasing.

0010

[Problems to be Solved by the Invention] However, in the above configuration, the electromagnet 29 which is the magnetic bias applying device
is fixed to the moving block 30, so when surface wobbling occurs in the magneto-optical recording medium 10, a distance variation occurs in the positional relationship between the magneto-optical recording medium 10 and the electromagnet 29.

For this reason, the strength of the external magnetic field for recording and erasing applied to the position of the minute optical spot 25 on the magneto-optical recording medium 10 changes, resulting in a problem that stable information recording and erasing cannot be achieved. It had a point.

In the conventional example shown in FIG. 2, so-called optical modulation recording was described as a recording/erasing mechanism. However, it goes without saying that the same problem also occurs in magnetic field modulation recording in which the magnetic field intensity of the electromagnet 29 is modulated by irradiating a linearly polarized light source with a constant light intensity when recording information.

In view of the above-mentioned problems, the present invention solves the problems caused by surface wobbling, which is a variation in the position of the objective lens in the optical axis direction of a magneto-optical recording medium, and provides a magneto-optical recording and reproducing system that enables stable recording and erasing of information. It provides equipment.

[0014]

[Means for Solving the Problems] In order to achieve this object, the magneto-optical recording and reproducing apparatus of the present invention includes a magneto-optical recording medium,
an objective lens that converges the light emitted from the light source to form a light spot on the medium; a signal detection means that detects an information signal, a focus error signal, and a tracking error signal using reflected light from the medium; and this signal detection means. objective lens driving means for driving an objective lens in accordance with a signal from the optical recording medium; a magnetic bias that maintains a constant distance to the magneto-optical recording medium by driving a magnetic bias applying device in a direction perpendicular to the surface of the magneto-optical recording medium in response to an electric signal detected in response to a focal error between the magneto-optical recording medium and the magneto-optical recording medium; The configuration includes additional device driving means.

[0015]

[Function] With this configuration, the position of the minute optical spot on the magneto-optical recording medium formed by the linearly polarized light source with high optical intensity without modulation is above the Curie temperature, and the external magnetic field for erasing is applied by the magnetic bias applying device. is added to achieve the erased state of information. Furthermore, if a linearly polarized light source with intensity modulation is used, an external magnetic field for recording is applied by the magnetic bias applying device at the position of the minute optical spot on the magneto-optical medium, so when the optical intensity reaches its peak, When the temperature reaches the Curie point or higher, the local magnetization is reversed and minute magnetic domains of about several μm are formed, thereby obtaining information recording state.

[0016] The magnetic bias applying device, which is located near a minute optical spot on an information recording medium and forms an external magnetic field during recording and erasing, reduces the applied external magnetic field due to distance fluctuations caused by surface wobbling of the magneto-optical recording medium. Since the strength fluctuates greatly, the signal detecting means uses a magnetic bias adding device drive means to perform magneto-optical recording in response to the electric signal detected in accordance with the focal error between the objective lens and the magneto-optical recording medium. By driving the magnetic bias applying device in the vertical direction so as to maintain a constant distance from the medium, it is possible to always apply the necessary constant magnetic field strength.

Therefore, under the action of the optical head and magnetic bias applying device as described above, the intensity of the external magnetic field applied when recording and erasing information at the minute spot position of the magneto-optical recording medium must always be maintained at a constant value. This makes it possible to always and stably erase and record information.

[0018] Although the effect in optical modulation recording has been described here, the effect of recording and recording in magnetic field modulation recording is similar.
Erasing can be performed stably.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of a magneto-optical recording/reproducing apparatus according to an embodiment of the present invention. In this embodiment, two semiconductor lasers are used to record two beams of light onto a magneto-optical recording medium. An example of forming a spot is given.

In FIG. 1, 1 is a semiconductor laser a having a wavelength of λa, 2 is a semiconductor laser b having a wavelength of λb, 3 is a collimating lens a, 4 is a collimating lens b, 5 is a mirror, 6 is a dichroic mirror, 7 is a half mirror, 8 is an objective lens, 9 is an objective lens actuator, 10 is a magneto-optical recording medium, 11 is a dichroic mirror, 12 is a half mirror, 13 is an analyzer, 14 is a photodetector, 15 is for error signal detection In the optical device, 16 is a minute light spot a, and 17 is a minute light spot b. 18 is a magnet, 19 is a yoke a, and 20 is a yoke b, which constitute a magnetic bias applying device 24. 22 is a magnetic bias adding device actuator, and 23 is a conversion amplifier, which converts a detection signal by an optical device for error signal detection into a drive signal for the magnetic device adding device actuator.

The operation of one embodiment of the magneto-optical recording and reproducing apparatus constructed as described above will be explained below. In the figure, a diverging light having a wavelength λa emitted from a semiconductor laser a1 for recording and reproducing information is converted into parallel light by a collimating lens a3 and transmitted through a dichroic mirror 6. Divergent light with a wavelength λb emitted from the semiconductor laser b2 for erasing information is converted into parallel light by the collimating lens b4, reflected by the mirror 5, and then transmitted through the dichroic mirror 6 to become a light beam with the wavelength λa. Then, the light beam is reflected by the dichroic mirror 6 to become a light beam having a small angle. After passing through the half mirror 7, the two light beams with wavelengths λa and λb are directed by the objective lens 8 onto the same track of the magneto-optical recording medium 10 moving in the direction of T. A spot a16 and a minute optical spot b17 for information erasing are formed by the semiconductor laser b2. The light reflected by the magneto-optical recording medium 10 is
After passing through the objective lens 8, the light is reflected by the half mirror 7 and enters the dichroic mirror 11 which transmits only the light having the wavelength λa. A light beam with a wavelength λb for erasing information is blocked by the dichroic mirror 11, and a transmitted light beam with a wavelength λa for recording and reproducing information is separated into two by a half mirror 12, one of which passes through an analyzer 13 and becomes a light beam. incident on the detector 14.

The other signal enters the error signal detection optical device 15, detects the focus error and tracking error that occur as the magneto-optical recording medium 10 moves, and electrically calculates and amplifies the errors. , the objective lens actuator 9 is moved in the P direction to control the focus, and the objective lens actuator 9 is moved in the Q direction perpendicular to the paper surface.
Tracking control is performed by moving in the direction.

The magnetic bias applying device 24 has a shape in which the magnet 18 is sandwiched between the yoke a19 and the yoke b20, and in the direction perpendicular to the plane of the paper, the magnet 18 is placed between the magnets 18 and 18, and the magnetic bias applying device 24 has a structure in which the magnet 18 is sandwiched between the yoke a19 and the yoke b20. It has a sufficiently large shape even for the maximum amount. The distance between the yoke a19 and the yoke b20 is approximately the same as the distance between the minute light spot a16 and the minute light spot b17.

Here, an error detection method is used for detecting the focus error and tracking error that occur with the movement of the magneto-optical recording medium 10 using a light beam having a wavelength λa which is reflected light from the magneto-optical recording medium 10. Among the detection signals from the optical device, the detection signal corresponding to the focus error of the objective lens is electrically calculated and amplified by the conversion amplifier 23 and converted into a drive signal for the magnetic bias adding device actuator 22. By driving the yoke a19 and the yoke b20 in the P direction, control is performed to maintain a constant distance between the yokes a19 and yoke b20 and the magneto-optical recording medium 10.

Magnet 1 of magnetic bias applying device 24
8 is magnetized in the direction of arrow T, and the yoke a19 generates a magnetic field in the direction of arrow N near the optical spot a16.
Further, due to the yoke b20, a magnetic field in the direction of the arrow M is obtained near the optical spot b17. When recording information, first, a minute light spot b1 for erasing having DC-like light intensity is created.
7, the minute optical spot b17 of the magneto-optical recording medium 10
The irradiated portion is raised to a temperature above the Curie point, and is magnetized perpendicularly in the direction of arrow M by the magnetic field in the direction of arrow M by the yoke b20. As described above, the portion of the magneto-optical recording medium 10 erased by the minute optical spot b17 moves in the direction of the arrow T. and semiconductor laser a1
Due to the intensity modulation, the portion of the magneto-optical recording medium 10 irradiated with the minute light spot a16 becomes
When the light intensity is at its peak, the temperature is above the Curie point,
A magnetic field in the direction of arrow N by the yoke a19 causes perpendicular magnetization in the direction of N to obtain a recording state.

When reproducing information recorded on the magneto-optical recording medium 10, the erasing semiconductor laser b2 stops emitting light,
The optical output of the semiconductor laser a1 is set small so that the temperature of the magneto-optical recording medium 10 is sufficiently lower than the Curie point due to the minute optical spot a16. At this time, photodetector 1
4, the information signal is reproduced.

As described above, according to this embodiment, the detection signal corresponding to the focus error of the optical device for error signal detection is electrically calculated and amplified by the conversion amplifier 23 to generate a drive signal for the actuator 22 of the magnetic device attachment device. By converting the signal into a signal, the magnetic bias applying device 24 is driven in the direction of arrow P by the magnetic bias applying device actuator 22, and the distance between the magnetic bias applying device 24 and the magneto-optical recording medium 10 is controlled to be constant. As a result, the intensities of the external magnetic fields in opposite directions can be maintained at a constant value at the positions of the minute optical spot a16 and the minute optical spot b17, and the operations of erasing and recording information can always be performed stably.

Furthermore, there is no need for a special distance detector for detecting surface wobbling of the magneto-optical recording medium 10. Since the distance detector is generally larger in shape and cost than the conversion amplifier 23, this embodiment allows the entire device to be made smaller, lighter, and cheaper.

Note that as an effect peculiar to this embodiment, the semiconductor laser a1 and the semiconductor laser b2 cause the magneto-optical recording medium 1 to
A minute light spot a16 and a minute light spot b1 on 0
7, and apply external magnetic fields in opposite directions to the portions of the minute light spot a16 and the minute light spot b17, which are located on the opposite side of the objective lens 8 across the magneto-optical recording medium 10. By providing the magnetic bias applying device 24, the recorded magneto-optical recording medium 1
0, it is possible to immediately record new information without performing the operation of only erasing information, and for this reason, the magneto-optical recording medium 10 is in a recordable state, that is, the direction of perpendicular magnetization of the medium surface is adjusted in advance. This has the advantage that it is not necessary to align them in a fixed direction.

Further, in this embodiment, the magnetic bias applying device 24 has a shape in which the magnet 18 is sandwiched between the yoke a19 and the yoke b20, but it may be an electromagnet with the yoke a19 and the yoke b20 as magnetic poles. In this case, the minute light spot a16 and the minute light spot b1
With respect to the external magnetic field in the opposite direction applied at the position 7, the set value of the required magnetic field strength determined based on the characteristics of the magneto-optical recording medium 10 can be easily selected by changing the current applied to the electromagnet. be.

[0032]

Effects of the Invention The present invention provides an optical head that forms a minute light spot on a magneto-optical recording medium, a magnetic bias applying device that applies an external magnetic field when recording or erasing information at the position of this minute light spot, and a In the signal detection means, by providing a magnetic bias applying device drive means for driving the magnetic bias applying device in response to an electric signal detected in accordance with a focus error between the objective lens and the magneto-optical recording medium, the external magnetic field can be reduced. Since the intensity can always be kept at a constant value, it is possible to perform information erasing and recording operations in a stable manner at all times.

Furthermore, by driving the magnetic bias applying device driving means using the detection signal from the signal detecting means, it is possible to achieve a reduction in size and weight and cost of the entire device. The above effects apply not only to so-called optical modulation recording but also to magnetic field modulation recording. As described above, the present invention makes it possible to realize a magneto-optical recording and reproducing device that can obtain a number of excellent effects.

[Brief explanation of the drawing]

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

[Figure 2] Schematic configuration diagram of a conventional magneto-optical recording/reproducing device

[Explanation of symbols]

1 Semiconductor laser a 2 Semiconductor laser b 3 Collimating lens a 4 Collimating lens b 5 Mirrors 6, 11 Dichroic mirrors 7, 12 Half mirror 8 Objective lens 9 Objective lens actuator 10 Magneto-optical recording medium 13 Analyzer 14 Photodetector 15 Error signal Detection optical device 16 Minute light spot a 17 Minute light spot b 18 Magnet 19 Yoke a 20 Yoke b 22 Magnetic bias applying device actuator 23
Conversion amplifier 24 Magnetic bias adding device 25 Minute light spot 26 Information detection block 27 Error detection block 28 Optical head 29 Electromagnet 30 Movement block

Claims (1)

[Claims] 1. An objective lens that converges light emitted from a light source to form a light spot on a magneto-optical recording medium, and an information signal, a focus error signal, and a tracking error signal using reflected light from the magneto-optical recording medium. Signal detection means for detecting;
objective lens driving means for driving the objective lens in response to a signal from the signal detection means; a magnetic bias applying device located near the optical spot and applying an external magnetic field to the optical spot position when recording or erasing information; The magnetic bias applying device is driven in a direction perpendicular to the surface of the magneto-optical recording medium in response to an electric signal detected in the signal detection means in response to a focal error between the objective lens and the magneto-optical recording medium. 1. A magneto-optical recording and reproducing apparatus comprising: a magnetic bias applying device driving means for always maintaining a constant distance from the magneto-optical recording medium.