JPH0249243A - Magneto-optical memory device - Google Patents

Abstract

PURPOSE:To heighten recording density and to increase recording capacity by making the end part of a recording mark in a direction of relative movement with an optical head conform to the second code of digital information consisting of two codes. CONSTITUTION:A laser beam from a semiconductor laser 11 passes a polarizing beam splitter 12 and an objective lens 13, and is made incident on a magneto- optical disk 1. Reflected light passes the lens 13, and part of it is distributed at the splitter 12, and is sent to a signal detection circuit via a convergence lens 14 and an optical detector 15. The optical head 2 records the recording marks A and B of a pair of (i) corresponding to data (h) by projecting the laser beam on the disk 1. The mark A corresponds to the data (h), and the marks A and B are recorded on the disk 1, and the mark A is recorded so that the edge part can correspond to 1 enclosed with 0 in the data (h). The edge part and the part between the edge parts of the mark B correspond to 1, and the mark B is recorded with width narrower than that of the mark A. In such a way, the recording density can be heightened and the recording capacity can be increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to recording information on a magneto-optical recording medium, erasing and reproducing recorded information, etc. by projecting a light beam onto a magneto-optical recording medium. The present invention relates to a magneto-optical memory device that performs.

[Conventional technology]

A magneto-optical memory device is a magneto-optical recording medium in which information can be recorded and erased.
A laser beam focused to a diameter of approximately μm is projected to record information on the magneto-optical recording medium, read out and erase the recorded information, etc., and a signal detection circuit detects the reproduced signal obtained from the optical head. A digital reproduction signal is obtained. The signal detection circuit has a peak position detection circuit that detects the peak position of the information pulse in the reproduced signal, or an amplitude detection circuit that detects the length and interval of the information pulse. A digital reproduction signal can be obtained from the signal.

As shown in FIG. 7, a conventional magneto-optical memory device uses a magneto-optical disk 101 as a magneto-optical recording medium, and records information on the magneto-optical disk 101, reads recorded information, erases information, etc. The optical head 102 is also provided.

The optical head 102 includes a semiconductor laser 111, a beam splitter (half mirror) 112, and an objective lens 113.1.
/2 wavelength plate 116, analyzer 117, condensing lens 114,
and a photodetector 115. A light beam emitted from the semiconductor laser 111 passes through a beam splitter (half mirror) 112, is focused by an objective lens 113, and is irradiated onto the magneto-optical disk 101. The reproduction light reflected by the magneto-optical disk 1.01 passes through the objective lens 113.
A portion of the beam is bent at right angles by a beam splitter (half mirror) 112.

The polarization direction of this light is tilted at a predetermined angle by the 1/2 wavelength plate 116, passes through the analyzer 117, and passes through the condenser lens 11.
4 and is incident on the photodetector 115. The reproduced light is converted into an electrical signal in the photodetector 115, and sent to a signal detection circuit to reproduce data.

The magneto-optical disk 101, that is, the magneto-optical recording medium, includes a magnetic thin film having an axis of easy magnetization perpendicular to the film surface, and recording on this magneto-optical recording medium is performed as follows. . That is, when a laser beam is irradiated from the optical head 102 to a magnetic thin film of a magneto-optical recording medium, the temperature of the area irradiated with the laser beam locally increases and the coercive force decreases. Therefore, when a magnetic field is externally applied to this region, the magnetization can be reversed in a desired direction, thereby recording information.

On the other hand, the reproduction operation is performed as follows. In other words, when a laser beam with a linear polarization weaker than that used during recording is projected onto a magneto-optical recording medium, the polarization plane of the reproduction light, which is reflected light or transmitted light from the magneto-optical recording medium, changes depending on the magnetization direction of the magneto-optical recording medium. Rotate by a predetermined angle. This rotation of the plane of polarization is caused by the Faraday effect for transmitted light and by the Kerr effect for reflected light. For example, if the vector of reflected light with respect to a certain magnetization direction of the magneto-optical recording medium is R+, and the vector of reflected light with respect to a magnetization direction that is opposite to the above-mentioned magnetization direction is R-, then as shown in FIG. The rotation angles of the polarization planes corresponding to the lights R+ and R- are +θ and -θ with respect to the incident polarization plane, respectively. Then, by detecting the detection polarization plane components Rα+ and Rα− of the reflected lights R+ and R− with the detection polarization plane set at 45° with respect to the incident polarization plane, a reproduced signal as an electrical signal is obtained. It is now possible to At this time, Rα- is at low level, R
α+ becomes high level.

The operation of the magneto-optical memory device based on the above principle is explained in the ninth section.
A specific explanation based on the figures is as follows.

For example, recording marks shown in FIG. 9B are recorded on the magneto-optical recording medium by magnetization reversal for the digital data shown in FIG. 9A. Here, if the vector of the reflected light from the recording mark is R-2 and the vector of the reflected light from the non-mark area other than the recording mark is R+, then the optical head 102 that has received the reflected light from the magneto-optical recording medium A reproduced signal (c) is obtained. In this reproduced signal (C), a pulse in the negative direction is generated by the reflected light R- from the recording mark, and becomes high level by the reflected light R0 from the non-mark portion.

Next, if the signal detection circuit has a peak position detection circuit, the signal detection circuit into which the above reproduction signal (C) is input will output a digital reproduction signal (d ) is obtained. On the other hand, when the signal detection circuit includes an amplitude detection circuit, the signal detection circuit obtains a digital reproduction signal (e) that becomes high level at a predetermined width with respect to the peak position in the negative direction. Digital data (f) as reproduction information is obtained from these digital reproduction signals (d) or (e).

[Problem to be solved by the invention]

However, the conventional configuration described above has a problem in that it is difficult to increase the recording density and recording capacity of the magneto-optical recording medium.

That is, in the case of the above configuration, in order to increase the recording density of the magneto-optical recording medium, the size of the recording mark must be further reduced. However, the smaller the recording mark, the harder it is to record on the magneto-optical recording medium. For example, when recording a recording mark by focusing a laser beam onto a magneto-optical recording medium, the smaller the recording mark becomes, depending on the focusing degree of the laser beam, the characteristics of the magneto-optical recording medium, the ambient temperature, etc. Therefore, it is difficult to increase the recording density by reducing the size of the recording mark, and the conventional configuration is not suitable for increasing the recording density.For convenience of explanation, , a recording mark is explained as an isolated mark corresponding to one code, but even if the recording mark is made to correspond to multiple codes and is formed to have the same dimensions as parts other than the recording mark. Similarly,
This is insufficient in terms of increasing recording density.

[Means to solve the problem]

In order to solve the above-mentioned problems, the magneto-optical memory device of the present invention provides a magneto-optical memory device that is provided movably relative to an optical head, and in which a first recording mark and a second recording mark as information are recorded. During the recording operation on the medium and the magneto-optical recording medium, the end portion in the direction of relative movement between the medium and the optical head is
The first and second recording marks are recorded so as to correspond to the second code of digital information consisting of codes, and the second recording mark has a portion between both ends corresponding to the second code, and While recording in a width narrower than one recording mark,
During the playback operation, the width of the first recording mark is smaller than the width of the first recording mark.
A light beam having a focused spot having a diameter larger than the width of the second recording mark is projected onto the magneto-optical recording medium, and a reproduction light containing reproduction information is input from the magneto-optical recording medium to output a reproduction signal. At the same time, only when the reproduction light is input when the light beam is irradiated to the end of the first or second recording mark, the interference of the reproduction light between the first or second recording mark and the non-mark area causes the above-described An information pulse corresponding to the second code is generated in the reproduced signal, and the light beam is
When the area between both ends of the recording mark is irradiated, the second
An optical head that outputs a reproduction signal at a level lower than a reference value due to interference in the reproduction light between recording marks and non-mark areas, an information pulse of the reproduction signal obtained from this optical head, and an information pulse when the reproduction signal is below the reference value. This configuration includes a signal detection circuit that detects the portion between the information pulses as a second code and converts the above-mentioned reproduced signal into a digital reproduced signal.

[For production]

According to the above configuration, the first recording mark is recorded by the optical head so that the end in the direction of relative movement with the optical head corresponds to the second code of digital information consisting of two codes. The second recording mark has an end corresponding to the second code in the direction of relative movement with the optical head, a region between both ends corresponding to the second code, and a width narrower than that of the first recording mark. Ru. Further, during a reproducing operation, a light beam having a focused spot having a diameter smaller than the width of the first recording mark and larger than the width of the second recording mark is projected from the optical head onto the magneto-optical recording medium, The optical head outputs a reproduction signal by inputting the reproduction light. Then, only when the reproduction light is input when the light beam is irradiated to the end of the first recording mark and when the light beam is irradiated to the end of the second recording mark, the first or second recording mark is different from the first or second recording mark. An information pulse corresponding to the above-mentioned second code is generated in the reproduction signal by interference of the reproduction light with the mark portion.

Further, when the light beam is irradiated to a region between both ends of the second recording mark, a reproduction signal of a level lower than the reference value is output due to interference in the reproduction light between the second recording mark and the non-marked part. . The signal detection circuit detects the information pulses of the reproduced signal obtained from the optical head and the portion between the information pulses when the value is below a reference value as a second code, and converts the reproduced signal into a digital reproduced signal.

By such recording and reproducing operations of the first and second recording marks, it is possible to include a large amount of information in each recording mark, thereby making it possible to increase the recording density. The above information pulse can be generated by forming the first recording mark longer and wider than the diameter of the condensed spot in the light beam, and by forming the second recording mark longer than the diameter of the condensed spot. It becomes easier. Further, by forming the first and second recording marks in a large size in this way, it becomes easy to form the image recording marks in an appropriate shape.

[Embodiment] An embodiment of the present invention will be described below based on FIGS. 1 to 6.

As shown in FIG. 1, the magneto-optical memory device according to the present invention includes a magneto-optical disk 1 as a magneto-optical recording medium, and a magneto-optical disk 1 that is capable of recording information, reading out and erasing recorded information, etc. The optical head 2 is provided with an optical head 2 that performs the recording, and a signal detection circuit 3 that converts the reproduced signal obtained from the optical head 2 into a digital reproduced signal.

The above magneto-optical disk 1 includes a magnetic thin film having an axis of easy magnetization in a direction perpendicular to the film surface, and can record and erase first and second recording marks as information by reversing the direction of magnetization. It is movable relative to the optical head 2.

In the above optical head 2, as shown in FIG.
Laser light emitted from the semiconductor laser 11 passes through a polarizing beam splitter 12, is focused by an objective lens 13, and is incident on the magneto-optical disk 1. The reflected light passes through the objective lens 13 again, and the optical path of a part of it is dispersed by the polarizing beam splitter 12. Further, this polarizing beam splitter 12 is arranged so that its polarization plane is perpendicular to the incident polarization plane, and also serves as an analyzer. This reflected light is collected by a condensing lens 14, converted into an electrical signal by a photodetector 15, and sent to a signal detection circuit.

As shown in FIG. 4, the optical head 2 projects a laser beam as a light beam onto the magneto-optical disk 1.
Recording mark A as the first recording mark shown in (i) for digital data (h) as digital information
And a recording mark B as a second recording mark is recorded. The end portion of the recording mark A in the relative movement direction with respect to the optical head 2, that is, the edge portion corresponds to one 1 surrounded by 0s. Note that 0 constitutes the first code, and l constitutes the second code. On the other hand, record mark B is
The edge part and the part between the edge parts correspond to 1,
The recording mark B as a whole corresponds to 1111. Furthermore, the recording mark B is formed to have a narrower width than the recording mark A. On the other hand, the portion between the edge portions of recording mark A and the non-mark portion, which is a portion other than recording mark AB, corresponds to 0. Furthermore, the recording mark A is formed in an oval shape with a length and width larger than the diameter of the condensed spot 4 of the laser beam during reproduction, and the recording mark B is formed in a length longer than the diameter of the condensed spot 4 mentioned above. This makes it easier for information pulses, which will be described later, to be generated.

In addition, the optical head 2 records the recording mark A during the reproduction operation.
A laser beam having a focused spot 4 with a diameter smaller than the width of the recording mark B and larger than the width of the recording mark B is projected onto the magneto-optical disk l, and a reproduced signal is output by inputting the reflected light. ing. Then, only when the reflected light when the laser beam is irradiated to the end of recording mark A or recording mark B is input, recording mark A or recording mark B is
The second
An information pulse corresponding to the code 1 is generated in the reproduced signal, and when the laser beam is irradiated to the area between both ends of the recording mark B, an information pulse corresponding to the code 1 is generated due to interference in the reflected light from the recording mark B and the non-mark area. , the reproduction signal is output at a level lower than the reference value.

In this embodiment, as shown in Fig. 3, there is an analyzer arranged so that the detection polarization plane is perpendicular to the incident polarization plane, and a photodetector that converts the output of this analyzer into an electrical signal. The optical head 2 has the following. When the laser beam is irradiated onto the edge portion of recording mark A or B, the polarization planes of the reflected light from recording mark A or B and the non-marked portion are in opposite directions with respect to the incident polarization plane of the laser beam. By rotating, the detected polarization plane components of both reflected lights are out of phase by 180 degrees, so that an information pulse or a portion of a level lower than the reference value is generated in the reproduced signal that is the output of the photodetector. It has become.

The signal detection circuit 3 detects the information pulse of the reproduced signal input from the optical head 2 and the portion where the value between the information pulses is equal to or less than the reference value as a second code 1, and converts the reproduced signal into a digital reproduced signal. . That is, the signal detection circuit 3 includes a peak position detection circuit that detects the peak position of the information pulse in the reproduced signal, and an amplitude detection circuit that detects the length and interval of the information pulse that is equal to or less than a reference value.
A digital reproduction signal can be obtained from the above-mentioned reproduction signal by these two circuits.

In the above configuration, during the recording operation of this magneto-optical memory device, a laser beam is projected from the optical head 2 onto the magneto-optical disk 1, and magnetization reversal of the irradiated area of the laser beam causes the magneto-optical memory device to perform a recording operation as shown in FIG. Then, recording marks A-B shown in (i) are recorded on the magneto-optical disk 1 corresponding to the digital data (h). At this time, recording mark A is recorded so that the edge portion of recording mark A corresponds to 1 surrounded by 0 in digital data <h). In addition, in recording mark B, the edge portion and the portion between the edge portions correspond to 1,
The width of the recording mark A is narrower than that of the recording mark A.

On the other hand, during a reproducing operation, a laser beam having a focused spot having a diameter smaller than the width of the recording mark A and larger than the width of the recording mark B is projected from the optical head 2 onto the magneto-optical disk 1. The reflected light is input to the optical head 2, and a reproduced signal (j) is obtained.

Here, when the laser beam projected from the optical head 2 is irradiated onto a non-mark part of the magneto-optical disk 1 other than the recording marks A-B, it is reflected according to the magnetization direction of the non-mark part due to the Kerr effect. The plane of polarization of light rotates. At this time, if this plane of polarization is rotated by +θ as shown in FIG. 3, the vector of the reflected light becomes R+. Since the detection polarization plane of the analyzer is arranged perpendicular to the incident polarization plane of the laser beam, Rα+, which is the detection polarization plane component of the reflected light R+, is obtained by detection by the analyzer, and the photodetector The reproduced signal (j) obtained from is at a high level.

Furthermore, when the laser beam is irradiated between the edge parts of the recording mark A, the magnetization of the recording mark A is reversed with respect to the non-marked part, so the polarization plane of the reflected light is rotated by 1θ, and the reflected light The vector of is R-. Then, Rα-, which is a detected polarization plane component of the reflected light R-, is obtained by detection with an analyzer, and the reproduced signal (j) obtained from the photodetector becomes high level. The reason why the level of the reproduction signal N) at this time is slightly lower is that the light reflected from the non-mark portion interferes with the light reflected from the recording mark A to some extent.

Furthermore, when the laser beam is irradiated onto the edge portion of the recording mark A as shown in Fig. 4, the polarization planes of the reflected light from the recording mark A and the non-mark portion are rotated by −θ3 and 10θ, respectively. Therefore, the detected polarization plane components of both reflected lights are 180°
The phase will be shifted. Therefore, the output of the photodetector becomes minimum at the time when the focused spot 4 of the laser beam evenly irradiates the recording mark A and the non-marked area, and the output of the photodetector becomes the minimum, and the reproduction signal (j
) produces a negative information pulse.

On the other hand, when the laser beam projected from the optical head 2 is irradiated onto the edge portion of the recording mark B on the optical disc 1, the reproduced signal (D
An information pulse in the negative direction is generated. Furthermore, when the above laser beam is irradiated between the edge portions of recording mark B,
Since the diameter of the focused spot of the laser beam is larger than the width of recording mark B, interference occurs between the reflected light from recording mark B and the non-marked area, and the reproduced signal (j) becomes at a lower level than the reference value. .

Here, FIG. 5 and FIG. 6 show an example of the results of computer simulation regarding the reproduced signal.

FIG. 5 is an explanatory diagram showing the relationship between the recording mark C and the focused spot 4 in a computer simulation of the reproduced signal of FIG. 6. In the same figure, recording mark C is
The length is 4 μm, the width is W, and the radius of the curved edge is W/2.
It is a semicircle. The focused spot 4 is a Gaussian beam, and its radius (the radius of a circle that is 1/e2 times the beam center intensity) is 0.65 μm. Focusing spot 4
The scanning direction is the long sleeve direction of the recording mark C, and the distance between the center of the recording mark C and the center of the focused spot 4 is shown in the upper part of the figure. In addition, the optical disc 1 on which the recording mark C is formed
The refractive index of the substrate is 1.5, the pitch between adjacent tracks in the vertical direction of the paper is 1.6 μm, the aperture ratio of the objective lens is 0.55, and the wavelength of the laser beam forming the focused spot 4 is 0.5 μm. It is 78 μm.

FIG. 6 is a diagram showing simulation results, in which the horizontal axis is the scanning direction of the condensed spot 4, and the distance between the center of the recording mark C and the center of the condensed spot 4 is shown. The vertical axis indicates the intensity of the reproduction light incident on the photodetector. The value is 1.0 when the focused spot 4 is located completely outside the recording mark C, and 0.0 when the reproduction intensity is O. A corresponding reproduced signal is obtained at the photodetector. Then, the width W of the recording mark C (and 2 of the radius of the curved part of the edge part
times), 0.4 μm, 0.6 μm, 0.8 μm, 1.0
μm, 1.4 μm, and 1.8 μm, and reproduced waveforms were simulated for these seven types. As a result, W=1
．． At 4 μm and 1.8 μm, pulses were noticeable at the edge portion of recording mark C.

In terms of the width W of the recording mark C (and twice the radius of the curved part of the cut and groove parts), W = 1.8 μm and 1.4 μm.
When W = 1.0 μm and 0.8 μm, the information pulse is noticeable, and the pulse at the edge still remains, and the level at the center of the recording mark C is gradually decreasing. I understand.

Additionally, although this simulation was conducted under the conditions described above, if other conditions such as the refractive index of the substrate, the wavelength λ of the laser beam, or the aperture ratio of the objective lens were changed, it would naturally be possible to The optimal recording mark C according to this
The width also changes.

Next, a method of recording by changing the width W of the recording mark C will be explained. For example, the diameter of the focused spot 4 is kept the same, and the strength of the externally applied magnetic field is weakened. In this way, it is possible to record the recording mark C with a smaller width. Conversely, if the magnetic field applied from the outside is strengthened, the width of the recording mark C increases.

Furthermore, instead of changing the strength of the magnetic field, the light intensity of the focused spot 4 during recording may be changed. That is, when the light intensity is decreased, the width of the recording mark C becomes smaller, and conversely, when the light intensity is increased, the width of the recording mark C becomes larger.

Incidentally, in the focus servo system for focusing the light spot 4 on the magneto-optical disk 1, the same effect can be obtained even if the focus point is electrically shifted. In other words, by adding an offset to the focus point, the focal spot 4
It is to expand.

Next, the reproduced signal (j) is input to the signal detection circuit 3, and the peak position detection circuit outputs a digital reproduction signal whose rising edge coincides with the peak position in the negative direction of the information pulse of the reproduced signal (j). A signal (k) is obtained. On the other hand, the amplitude detection circuit obtains a digital reproduction signal (l) which becomes high level in a predetermined width with respect to the peak position in the negative direction of the information pulse of the reproduction signal (H) and a portion having a level lower than the reference value. Since the pulses of these digital reproduction signals (k) and (2) correspond to 1 of digital data (h), both signals (k) and (2) correspond to 1 of digital data (h).
・From (2), digital data (m
) is obtained.

The configuration for obtaining the above digital data (m) uses the information pulse generated corresponding to the edge portion of recording mark A-B as a reproduction clock, and the reproduction of information is performed between the edge portion of recording mark B. It is also possible to detect based on the level of .

Further, in this embodiment, a configuration is shown in which reproduction is performed by utilizing the rotation of the polarization plane of the reflected light from the magneto-optical disk 1 due to the Kerr effect, but the present invention is not limited to this. Reproduction may be performed by utilizing the rotation of the polarization plane of the light transmitted through the disk 1 due to the Faraday effect.

Furthermore, although an example has been shown in which the detection polarization plane of the analyzer is perpendicular to the incident polarization plane of the laser beam, in the present invention, the edge portion of recording mark A-B and the edge portion of recording mark B are It is sufficient that interference occurs between the reflected light or the transmitted light from the recording mark A-B and the non-marked portion between them, and the two do not necessarily have to be perpendicular to each other.

〔Effect of the invention〕

As described above, the magneto-optical memory device according to the present invention includes a magneto-optical recording medium that is provided movably relative to the optical head and on which a first recording mark and a second recording mark as information are recorded; During the recording operation on the magneto-optical recording medium, the first code is set so that the end in the direction of relative movement with the optical head corresponds to the second code of digital information consisting of two codes.
and a second recording mark is recorded, and the second recording mark has a portion between both ends corresponding to the above-mentioned second symbol, and is recorded in a narrower width than the first recording mark. , a light beam having a focused spot having a diameter smaller than the width of the first recording mark and larger than the width of the second recording mark is projected onto the magneto-optical recording medium, and reproduction including reproduction information from the magneto-optical recording medium is performed. By inputting light, a reproduction signal is output, and only when the reproduction light is applied manually when the light beam is irradiated to the end of the first or second recording mark, the first or second recording mark and non-mark are detected. An information pulse corresponding to the above-mentioned second code is generated in the reproduction signal by interference in the reproduction light with the second recording mark, and when the light beam is irradiated to the area between both ends of the second recording mark, the second recording mark and an optical head that outputs a reproduction signal at a level lower than a reference value due to interference of the reproduction light with the non-marked portion;
A signal detection circuit detects the information pulse of the reproduced signal obtained from the optical head and the part between the information pulses when the value is below a reference value as a second code, and converts the reproduced signal into a digital reproduced signal. The configuration is as follows.

Therefore, the edges of the first and second recording marks and the width of the second recording mark correspond to the information, and one recording mark can contain a large amount of information. It becomes possible to increase the density and increase the recording capacity. Furthermore, since the recording density is not increased simply by reducing the size of the recording mark, it becomes possible to form the recording mark in a larger size, which facilitates the formation of the recording mark. Furthermore, for example, the half-wave plate 116 and analyzer 117 shown in FIG. 7 can be omitted, and a polarizing beam splitter can be placed in place of the beam splitter 1120. Therefore, the number of parts can be reduced, and the optical system can be simplified.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the present invention, in which FIG. 1 is a schematic block diagram showing the main parts of a magneto-optical memory device, and FIG. An explanatory diagram specifically showing the configuration of the magnetic memory device, FIG. 3 is an explanatory diagram of the reproducing operation in the optical head, and FIG. 4 is an explanatory diagram showing the relationship between recording marks and signal waveforms in each part of the magneto-optical memory device. , FIG. 5 is an explanatory diagram showing the relationship between the recording mark and the focused spot in the computer simulation for the reproduced signal shown in FIG. 6, and FIG. Graphs 7 to 9 showing the relationship between the position of the light beam and the intensity of the reproduction light incident on the photodetector show conventional examples,
FIG. 7 is an explanatory diagram showing the configuration of the magneto-optical memory device, FIG. 8 is an explanatory diagram of the reproducing operation in the optical helad, and FIG. 9 is a diagram showing the relationship between recording marks and signal waveforms in each part of the magneto-optical memory device. It is an explanatory diagram. 1 is a magneto-optical disk (magneto-optical recording medium), 2 is an optical head, 3 is a signal detection circuit, and 4 is a condensing spot. Te ° Itsuta IL i Kui Rola I S Fushi (, Q) τ Isital (m) Arc r] "-1m-==1 r-1r-1+-+J
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Claims (1)

[Claims] 1. A magneto-optical recording medium that is provided to be movable relative to an optical head and in which a first recording mark and a second recording mark as information are recorded, and recording on the magneto-optical recording medium. During operation, the first and second recording marks are recorded so that the ends in the direction of relative movement with the optical head correspond to the second code of digital information consisting of two codes, and the second recording mark The area between the two ends corresponds to the second symbol above, and the width is narrower than that of the first recording mark.
Projecting a light beam having a focused spot with a diameter smaller than the width of the recording mark and larger than the width of the second recording mark onto the magneto-optical recording medium, and inputting reproduction light containing reproduction information from the magneto-optical recording medium. By doing so, a reproduction signal is output, and only when the reproduction light is input when the light beam is irradiated onto the end of the first or second recording mark, the connection between the first or second recording mark and the non-mark area is detected. Interference in the reproduction light generates an information pulse corresponding to the above-mentioned second code in the reproduction signal, and when the light beam is irradiated to the area between both ends of the second recording mark, the second recording mark and the non-mark area are separated. An optical head that outputs a reproduction signal with a level lower than the reference value due to interference in the reproduction light of 1. A magneto-optical memory device, comprising: a signal detection circuit that detects the two codes and converts the reproduced signal into a digital reproduced signal.