JPH041953A - Magneto-optical reproducing device - Google Patents

Abstract

PURPOSE:To stably reproduce both recording media as mentioned below in simple constitution by keeping the polarization state of light to be incident upon a recording medium unchanged when the recording medium is a magneto-optical recording medium and changing the polarization state of light to be incident upon a recording medium when the recording medium is some recording medium other than a magneto-optical system. CONSTITUTION:Light emitted from a light source (semiconductor laser) 11 is led to a recording medium 16, and its return light is separated from an optical path proceeding the recording medium 16 from the light source 11 by an optical path separating means (beam splitter) 13, and is detected by photodetectors 19a and 19b. Then, when the recording medium 16 is the magneto-optical recording medium, the light emitted from the light source 11 is incident upon the recording medium 16 without changing the polarization state of this light by a polarization state varying means 14. On the other hand, when the recording medium 16 is the recording medium other than the magneto-optical system, the light emitted from the light source 11 is incident upon the recording medium after changing the polarization state of the light by the polarization state varying means 14. By this method, both magneto-optical recording medium and recording medium another than the magneto-optical system are stably reproduced in simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical reproducing apparatus capable of reproducing both a magneto-optical recording medium and a recording medium using a method other than magneto-optical.

[Background Art] In recent years, with the development of information technology, optical recording and reproducing devices have attracted attention as large-capacity storage media.

Among these optical recording and reproducing devices, the magneto-optical type is attracting attention because it is rewritable.

When reproducing information recorded on a recording medium, magneto-optical methods read the rotation of the plane of polarization according to the magnetization direction of the recording surface of the recording medium, whereas methods other than magneto-optical read the rotation of the plane of polarization that corresponds to the direction of magnetization on the recording surface of the recording medium. It is common to read changes in the intensity of the returned light due to changes in reflectance using phase transitions or other factors. Therefore, the optical systems of the reproducing apparatuses are different in both types, and one reproducing apparatus has not been used for both types.

Various types of magneto-optical reproducing devices have been proposed in the past. For example, the applicant filed the previously filed patent application No. 1-2
In No. 06934, the polarization state of reflected light from a magneto-optical recording medium is determined using a first optical means such as a quarter-wave plate.
The elliptically polarized light is converted into clockwise or counterclockwise elliptically polarized light with the same direction and the same size depending on the direction of magnetization, and then this elliptically polarized light is converted into an elliptically polarized light whose major axis is approximately orthogonal depending on the direction of rotation using a second optical means. We have proposed a reproducing device that takes elliptically polarized light that rotates in a direction, separates it into two orthogonal polarized components by a third optical means, detects these components with two photodetectors, and reads out information based on the output difference. There is. This device has the advantage of being able to reduce the reduction in C/N of the reproduced signal due to adjustment errors in the optical system.

By the way, in the above proposed magneto-optical reproducing device, when attempting to reproduce a recording medium other than the magneto-optical method (for example, a CD optical disc), it is conceivable to obtain a reproduction signal by the sum of the outputs of two photodetectors. .

[Problem M to be solved by the invention] When trying to reproduce a magneto-optical recording medium and a recording medium using a method other than magneto-optical using the same playback device, it is necessary to read the rotation of the plane of polarization in the magneto-optical method. Restrictions on the optical system must be adapted to playback of the magneto-optical recording medium. Therefore, in this reproducing apparatus, the arrangement 9 of the optical system is not necessarily optimal for reproducing a recording medium by a method other than magneto-optical.

For example, in a reproducing apparatus for a recording medium using a method other than magneto-optical, - when fishing on a boat, the angle of 1 is set at an angle of 45° with respect to the polarization plane of the emitted light of a semiconductor laser (hereinafter referred to as LD).
The /4 wavelength plate and the polarizing beam splitter form a so-called optical isolator that separates the light returning from the recording medium from the optical path toward the LD, increasing the amount of light in the detection system and reducing the light returning to the LD. Recording media using systems other than magneto-optical have a high reflectance and therefore return a large amount of light, causing backtalk noise of the LD, which affects the reproduction characteristics, so the optical isolator is indispensable. On the other hand, the optical isolator cannot be used to reproduce a magneto-optical recording medium because it is necessary to make linearly polarized light incident on the recording medium. Therefore, when the same reproducing device is used for reproducing a magneto-optical recording medium and reproducing a recording medium using a method other than magneto-optical, the optical isolator cannot be used, so the LD
backtalk noise becomes a problem.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magneto-optical reproducing device that has a simple configuration and is capable of stable reproduction of both magneto-optical recording media and recording media using methods other than magneto-optical. It is an object.

[Means for Solving the Problems] The magneto-optical reproducing apparatus of the present invention includes a light source that emits light to be irradiated onto a recording medium, an optical system that guides the emitted light from the light source to the recording medium, and a light source that returns light from the recording medium. and a light detection means for detecting the returned light separated by the optical path separation means, wherein the recording medium is in the optical system. When the recording medium is a magneto-optical recording medium, the polarization state of the light incident on the recording medium is not changed; when the recording medium is a recording medium using a method other than magneto-optical, the polarization state of the light incident on the recording medium is not changed. A polarization state variable means is provided. The polarization state variable means includes, for example, a wavelength plate provided within the optical system and means for rotating the wavelength plate. In the present invention, when the polarization direction of the light that has passed through the polarization state variable means is rotated while remaining linearly polarized,
It is assumed that the polarization state has not changed, and that the polarization state has changed when linearly polarized light becomes elliptically polarized light or circularly polarized light after passing through the polarization state variable means.

[Function] In the present invention, the light emitted from the light source is guided to the recording medium by the optical system, and the return light from the recording medium is separated from the optical path from the light source to the recording medium by the optical path separation means, and the light is detected by the optical system. detected by means. When the recording medium is a magneto-optical recording medium, the polarization state variable means causes the light emitted from the light source to enter the recording medium without changing the polarization state. This makes it possible to reproduce information using a magneto-optical method. On the other hand, when the recording medium is a recording medium using a method other than magneto-optical, the polarization state variable means changes the polarization state of the light emitted from the light source and causes the light to enter the recording medium. This, combined with the action of the optical path separation means, makes it possible to reduce the amount of light returning to the light source.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure is an explanatory diagram showing the main parts of the magneto-optical/magnetic reproducing device, Fig. 2 is a block diagram showing the configuration of the magneto-optical reproducing device, and Fig. 3 is a 174
A flowchart showing the rotation control of the wavelength plate, Fig. 4 is an explanatory diagram showing the polarization state at each part of Fig. 1 during reproduction from a magneto-optical recording medium, and Fig. 5 shows a case where the orientation of the 1/4 wavelength plate is ±45°. FIG. 2 is an explanatory diagram showing the polarization state at each part in FIG. 1 during reproduction from other recording media.

As shown in FIG. 2, the magneto-optical reproducing apparatus includes an optical pickup 1 arranged to face a disk-shaped recording medium (hereinafter referred to as a disk) 16, and a disk rotation motor that rotates the disk 16. 2. The optical pickup 1 is moved in a direction across the tracks of the disk 16 by an optical pickup moving mechanism 3. Further, the disk rotation motor 2 is
It is designed to be driven by a disk rotation motor drive section 4. The optical pickup moving mechanism 3 and the disk rotation motor drive section 4 are controlled by a basic operation control section 31 within a control section 30. Further, a disk attachment detection section 5 is provided to detect whether or not a disk 16 is attached, and an output signal of this detection section 5 is inputted to the basic operation control section 31. Further, the output signal of the optical pickup 1 is processed by a disk reproduction signal processing section 6, so that an information signal is reproduced and an error signal is generated. Further, the output signal of the disc reproduction signal processing section 6 is inputted to a control track information identification section 33 in the control section 30. The output signal of the control track information identification section 33 is input to the basic operation control section 31. Further, within the control section 30, a wave plate orientation storage section 32 connected to the basic control section 31 is provided.

Further, a semiconductor laser (hereinafter referred to as LD) 11, which will be described later, is provided in the optical pickup 1, and this LD
II is driven by the LD drive section 7. Further, a quarter-wave plate 14, which will be described later, is provided within the optical pickup 1, and the quarter-wave plate 14 is rotated by a wave plate rotation motor 8. This wave plate rotation motor 8 is driven by a wave plate rotation motor drive section 9. The LD drive unit 7 and the wave plate rotation motor drive unit 9 are connected to the basic operation control unit 3.
1.

As shown in FIG. 1, the optical pickup 1 has an LDII as a light source, and on the optical path of the emitted light from the LDII, collimator lenses 12. Beam splitter 13 as optical path separation means. A quarter wavelength plate 14 and an objective lens 15 are provided as polarization state variable means.

Note that the beam splitter 13 has a reflectance for P polarized light as RP and a reflectance for Sli light as R9.
Rp<Rs. Then, the light emitted from the LD 11 is made into parallel light by a collimator lens 12,
Passes through a beam splitter 13 and a quarter wavelength plate 14,
The light is focused onto a disk 16 by an objective lens 15.

The light reflected by the disk 16 passes through the objective lens 15 and the quarter-wave plate 14 and enters the beam splitter 13. The light reflected by this beam splitter 13 passes through a 1/4 wavelength plate 17 and passes through a polarizing beam splitter 1.
8. Said 1/4 wavelength plate 17
is arranged so that the optical axis of the crystal is oriented at 45° with respect to the direction of linearly polarized laser light from LDll. The polarizing beam splitter 18 is configured to transmit the P polarized component and reflect the s(1 completed component).The light transmitted through the polarizing beam splitter 18 is received by a photodetector 19a, and the polarized beam is The light reflected by the splitter 18 is received by a photodetector 19b.The outputs of each photodetector 19a and 19b are connected to each input terminal of a differential amplifier 20 and each input terminal of an amplifier (adder) 21. It is applied to the input terminal.

The 1/4 wavelength plate 14 is connected to a wave plate rotation motor 8. shown in FIG. Wave plate rotation motor drive section 9. Basic operation control section 31
It is rotated about the optical axis of the optical system by a rotation means 24 consisting of a wave plate orientation storage section 32 and a wave plate orientation storage section 32. Further, the rotation means 24 includes a control track information identification section 33 and a basic operation control section 3 shown in FIG.
It is controlled by a recording medium discriminating means 25 consisting of 1.

Next, the operation of this embodiment will be explained with reference to FIGS. 3 to 5.

The magneto-optical reproducing apparatus of this embodiment uses a magneto-optical recording medium as the disk 16 and a recording medium other than magneto-optical (hereinafter referred to as
Described as other recording media. ) can be played. Other recording media include those that record information using uneven pits or changes in reflectance that utilize phase transition. This also includes rewritable types.

When the recording medium discriminating means 25 determines that the disk 16 is a magneto-optical recording medium, the rotating means 24 rotates the quarter-wave plate 14 at 0° or 0° with respect to the linearly polarized direction of the laser beam from the LDll. It is rotated to have a 90° orientation. On the other hand, when the recording medium discriminating means 25 determines that the disk 16 is another recording medium, the rotating means 24 rotates the 1/4 wavelength plate 14 into the LDl.
Oo and 9 for the direction of linear polarization of the laser beam from l
It is rotated to an orientation other than 0°, preferably +45° or -45°.

This operation will be explained using FIG. 3.

First, step Sl (hereinafter, step is omitted, simply S
It is written like l. ), the disk attachment detection section 5 and the basic operation control section 31 determine whether or not the disk 16 is attached. If NO, repeat Sl. YE
In the case of S, in S2, the basic operation control unit 31. The disk rotation motor 2 is rotated (started up) under the control of the disk rotation motor drive section 4 .

Next, in S3, the optical pickup (referred to as optical PU in FIG. 3) 1 is moved to the vicinity of the control track of the disk 16 under the control of the basic operation control section 31 and the optical pickup moving mechanism 3.

Next, in S4, the optical pickup 1 is set to disc read mode (reproduction mode). and.

In S5, optical pickup 1. Disc playback signal processing section 6
Then, the control track information identifying section 33 reads out the disc type information recorded on the control track.

Next, in S6, the type of the disc 16 is determined by the basic operation control 31 from the output of the control track information identification section 33.

Next, in S7, the basic operation control unit 31 determines the setting angle of the azimuth of the quarter-wave plate 14 based on the determined type of disk 16. In addition, 1/ according to the type of disk 16
The orientation of the four-wave plate 14 is stored in the wave plate orientation storage section 32.

Next, in S8, the basic operation control unit 31 confirms the current orientation of the wave plate 14, and determines the amount of rotation of the wave plate 14 from the set angle determined in S7.

Next, in S9, the basic operation control unit 31 determines the rotation amount of the wave plate rotation motor 8 according to the obtained rotation amount. Then, in S10, the wave plate rotation driving section 9 and the wave plate rotation motor 8 rotate the motor 8 according to the amount of rotation of the wave plate rotation motor 8 determined in S8.

Next, when the setting of the orientation of the wave plate 14 is completed at Sll, the process ends.

As described above, when the disk 16 is a magneto-optical recording medium, the 174-wave plate 14 is rotated so that it is oriented at 0° or 90° with respect to the direction of linearly polarized laser light from the LDll. FIG. 4 shows the polarization state at each part A to G in FIG. 1 in this case. As shown in FIG. 4A, the linearly polarized P-polarized light emitted from the semiconductor laser 11 is made into parallel light by the collimator lens 12, and passes through the beam splitter 13 as the P-polarized light. This light passes through the quarter-wave plate 14, but since the direction of the quarter-wave plate 14 is Oo or 90', its polarization state does not change, as shown in B of FIG.

The light that has passed through this 1/4 wavelength plate 14 is transmitted through the objective lens 15.
The light then enters the disk 16, which is a magneto-optical recording medium, and
According to the information recorded on the disk 16, that is, the direction of magnetization, the light is reflected by undergoing Kerr rotation of ±θ as shown in C of the fourth factor.

When this reflected light passes through the objective lens 15 and enters the quarter-wave plate 14 again, this incident light contains an S-polarized light component generated by Kerr rotation, so the S-polarized light component is out of phase with respect to the PJ light component. The light shifted by 90° and rotated by ±θ becomes elliptically polarized light with the same size in the clockwise and counterclockwise directions, as shown in D in FIG.

When the return light from the disk 16 that has passed through this 1/4 wavelength plate 14 is reflected by the beam splitter 13, Rp<R
The shape of elliptically polarized light changes depending on the relationship of s.

When the return light reflected by the beam splitter 13 passes through a quarter-wave plate 17 with an azimuth of 45°, the light that has undergone Kerr rotation of ±θ is directed in the same direction as shown in E of FIG. The light rotates to become elliptically polarized light whose major axes are perpendicular to each other. Here, the direction of the long axis of the elliptically polarized light corresponds to the direction of P or S polarized light, and the direction of the short axis corresponds to the direction of S or P polarized light, respectively.

Therefore, the transmitted light and the reflected light of the polarizing beam splitter 18 have opposite phases as shown in F and G of FIG. 4, respectively. That is, depending on the direction of Kerr rotation, the amount of one of the transmitted light and the reflected light becomes large and the amount of the other becomes small. Therefore, by detecting the output difference between the photodetectors 19a and 19b, which respectively receive the transmitted light and the reflected light, with the differential amplifier 20, a magneto-optical reproduction signal can be obtained.

The above-mentioned operation during reproduction of magneto-optical recording media is described in Japanese Patent Application No. 1999-1-
It is described in detail in No. 206934.

On the other hand, if the disk 16 is another recording medium, 1
/4 wavelength plate 14 is in an orientation other than 0° and 90°, preferably +
It is rotated to have an orientation of 45°. 1/4 wavelength plate 1
Each part A to G in Figure 1 when the direction of 4 is ±45°
FIG. 5 shows the polarization state at . As shown in FIG. 5A, the linearly polarized P-polarized light emitted from the semiconductor laser 11 is made into parallel light by the collimator lens 12, and passes through the beam splitter 13 as the P-polarized light. This light is 1/4
The P-polarized light passes through the wavelength plate 14, but since the orientation of the quarter-wave plate 14 is +45°, the P-polarized light is converted into circularly polarized light, as shown in FIG. 5B. The light that has passed through the quarter-wave plate 14 passes through the objective lens 15 and enters the disk 16, and is reflected by the disk 16 as circularly polarized light, as shown in FIG. 5C. When this reflected light passes through the objective lens 14 and enters the quarter-wave plate 14 again, the circularly polarized light is converted into S-polarized light, as shown in D in FIG. The return light from the disk 16 that has passed through the 174 wavelength plate 14 is incident on the beam splitter 13. Here, the reflectance of the beam splitter 13 for P-polarized light and S-polarized light is R as described above.
If p<R5, the amount of light returning to the LDII can be reduced and the amount of light in the detection system can be increased. The return light reflected by this beam splitter 13 is directed in the direction 45
The light passes through the 1/4 wavelength plate 17 and is converted into circularly polarized light as shown in FIG. As shown in F and G of FIG. 5, the amounts of transmitted light and reflected light are the same. Then, by detecting the sum of the outputs of the photodetectors 19a and 19b, which respectively receive the transmitted light and the reflected light, with the amplifier 21, the information recorded by the pits or the like is reproduced.

For reproduction of other recording media, the orientation of the 174-wave plate 14 is +45° or -45'' with respect to the direction of the linearly polarized light emitted from the LDll, and the direction of the beam splitter 13 is
The effect is greatest when the polarization reflectance is 100%.

As described above, according to the present embodiment, one magneto-optical reproducing apparatus can reproduce a magneto-optical recording medium and other materials by simply rotating the quarter-wave plate 14 according to the type of recording medium. It becomes possible to reproduce both types of recording media.

Moreover, when reproducing other recording media, the amount of light returning to the LDll can be reduced, allowing stable reproduction with less backtalk noise of the LDll. Furthermore, when reproducing magneto-optical recording media, as described in Japanese Patent Application No. 1-206934, it is possible to reduce the reduction in the C/N of the reproduced signal due to adjustment errors in the optical system. However, the reliability of the playback device can be greatly improved.

In addition, simply by rotating the quarter-wave plate 14, it is possible to switch between reproduction of a magneto-optical recording medium and playback of other recording media, compared to the case where a quarter-wave plate is inserted into and removed from the optical path. The optical pickup can be made smaller.

6 to 9 relate to the second embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the main parts of the magneto-optical reproducing device, Fig. 7 is an explanatory diagram showing the optical system between the total reflection mirror and the recording medium, and Fig. 8 is an explanatory diagram showing the optical system between the total reflection mirror and the recording medium. An explanatory diagram showing the polarization state in each part of the figure, Figure 9 shows that the direction of the 1/2 wavelength plate is ±
FIG. 7 is an explanatory diagram showing the polarization state at each part in FIGS. 6 and 7 during reproduction from other recording media at 22.5°.

As shown in FIG. 6, in this embodiment, a 1/2 wavelength plate 22 is provided in place of the 1/4 wavelength plate 14 in the first embodiment. This half-wave plate 22 is rotated about the optical axis of the optical system by a rotating means 24. Also, Dll does not pass through the 1/2 wavelength plate 22.
The light is totally reflected by a total reflection mirror 23, and is focused onto a recording medium 16 by an objective lens 15, as shown in FIG. In addition, the total reflection mirror 2
The reflecting surface 23a of No. 3 has a phase difference of 90° between P-polarized light and S-polarized light.
It is coated so that

In addition, in this embodiment, the 1/2 wavelength plate 22 and the total reflection mirror 2
3 constitutes a polarization state variable means.

The other configurations are the same as in the first embodiment.

Next, the operation of this embodiment will be explained.

When the recording medium determining means 25 determines that the disk 16 is a magneto-optical recording medium, the rotating means 24 rotates the 1/2 wavelength plate 22 in the direction of the linear polarization of the laser beam from the LDll.

Rotated to have an orientation of ±45° or 90°.

On the other hand, when the recording medium discriminating means 25 determines that the disk 16 is another recording medium, the rotating means 25
4, the half-wave plate 14 rotates Oo, ±45° and 90° with respect to the linearly polarized direction of the laser light from the LDII.
azimuth other than, preferably +22.5° or -22.5°
It is rotated so that it has an orientation of °.

When the disk 16 is a magneto-optical recording medium, the half-wave plate 22 is rotated so as to be oriented at 0° ±45° or 90° with respect to the direction of linearly polarized laser light from the LDll. The orientation of the 1/2 wavelength plate 22 is 0° or 90°
FIG. 8 shows the polarization state at each part A to I in FIGS. 6 and 7 at the time. As shown in A of FIG. 8, the linearly polarized P (i light) emitted from the semiconductor laser 11 is made into parallel light by the collimator lens 12, and passes through the beam splitter 13 as the P polarized light. /2 wavelength plate 22, but the direction of this 1/2 wavelength plate 22 is 0''
or 90', the polarization state does not change as shown in B of FIG.

The light that has passed through this 1/2 wavelength plate 22 is reflected by a total reflection mirror 2.
3, but the polarization state does not change because it does not have an S-polarized component. This light passes through the objective lens 15 and is converted into linearly polarized light as shown in C in FIG. 16 and the information recorded on this disk 16, that is, the direction of magnetization,
As shown in , it undergoes Kerr rotation of ±θ and is reflected. This reflected light passes through the objective lens 15 and returns to the total reflection mirror 2.
It is reflected at 3. At this time, since there is an S-polarized component generated by Kerr rotation, the phase of the S-polarized component is shifted by 90 degrees with respect to the P-polarized component, and the light rotated by ±θ is as shown in E in FIG. It becomes elliptically polarized light with the same magnitude in the clockwise and counterclockwise directions. This elliptically polarized light enters the half-wave plate 22 again, and the S-polarized light component has a phase of 180° with respect to the P-polarized light component.
As a result, the direction of rotation of the elliptically polarized light is reversed, as shown at F in FIG. Through this 1/2 wavelength plate 22? When the returned light from the disk 16 is reflected by the beam splitter 13, the shape of the elliptically polarized light changes due to the relationship Rp<Rs. The return light reflected by this beam splitter 13 is
When passing through the quarter-wave plate 17 with an azimuth of 45°, the light that has undergone Kerr rotation of ±θ is rotated in the same direction as shown in G in FIG. Become. The light that has passed through the quarter-wave plate 17 is separated by a polarizing beam splitter 18 into two orthogonal polarized components as shown by H and I in FIG. The information signal is regenerated in the same way as it works during regeneration.

On the other hand, if the disk 16 is another recording medium, 1
The /2 wavelength plate 22 is rotated so as to be in an orientation other than Oo, ±45° and 90°, and an orientation of +22.5° with respect to the direction of the linearly polarized laser light from the LDll.

FIG. 9 shows the polarization state at each part A to {circle around (2)} in FIG. 6 when the azimuth of the half-wave plate 22 is +22.5 degrees.

As shown in FIG. 9A, the linearly polarized P-polarized light emitted from the semiconductor laser 11 is made into parallel light by the collimator lens 12, and passes through the beam splitter 13 as the P-polarized light. This light passes through the 1/2 wavelength plate 22, but this 1/2 wavelength plate 22
Since the orientation of the four-wavelength plate 14 is +22°5°, the P-polarized light is converted into linearly polarized light whose polarization direction is rotated by 45°, as shown in FIG. 9B. The light that has passed through the 172 wavelength plate 22 is totally reflected by the total reflection mirror 23, and the S-polarized light component is shifted in phase by 90 degrees from the P-polarized light component, becoming circularly polarized light as shown in C in FIG. . This circularly polarized light enters the disk 16 through the objective lens 15, and is reflected by the disk 16 as the circularly polarized light, as shown at D in FIG. This reflected light passes through the objective lens 14 and returns to the total reflection mirror 2.
It is reflected at 3. At this time, the phase of the S-polarized light component is shifted by 90 degrees with respect to the P-polarized light component, as shown in E of FIG.
The outgoing linearly polarized light is converted into linearly polarized light rotated by 90 degrees. When this linearly polarized light enters the 1/2 wavelength plate 22, it is converted into 5g14 light as shown in F in FIG. The return light from the disk 16 that has passed through the 1/2 wavelength plate 22 is incident on the beam splitter 13. Here, the reflectance of the beam splitter 13 for P-polarized light and S-polarized light is R
If p<Rs, the amount of light returning to the LDll can be reduced and the amount of light in the detection system can be increased. The return light reflected by this beam splitter 13 is directed in the direction 45
The light passes through the 1/4 wavelength plate 17, is converted into circularly polarized light as shown in G in FIG. 9, and enters the polarizing beam splitter 18. Then, by this polarizing beam splitter 18,
As shown at H and B in FIG. 9, the light is separated into two orthogonal polarization components, and the information signal is reproduced in the same way as in the first embodiment when reproducing other recording media.

For reproduction of other recording media, the direction of the half-wave plate 22 is +22.5° or -22.5' with respect to the direction of the linearly polarized light emitted from the LDll, and the direction of the beam splitter 13 is The effect is greatest when the polarization reflectance is 100%.

As described above, according to this embodiment, one magneto-optical reproducing apparatus can reproduce a magneto-optical recording medium and other materials by simply rotating the half-wave plate 22 according to the plug of the recording medium. This makes it possible to play back both types of recording media.

In addition, when the direction of the 1/2 wavelength plate 22 is set to ±45 degrees when reproducing the magneto-optical recording medium, the polarization direction of the light emitted from the LD11 and passing through the 172-wave plate 22 will be different from that before passing. Although the light becomes linearly polarized light rotated by 90 degrees, even if this light is reflected by the total reflection mirror 23, it remains linearly polarized light. In the present invention, if the polarization direction of the light that has passed through the polarization state variable means is rotated while remaining linearly polarized, it is assumed that the polarization state has not changed, and the linearly polarized light that has passed through the polarization state variable means is converted into elliptically polarized or circularly polarized light. When the light becomes polarized, it is assumed that the polarization state has changed.

Other functions and effects are similar to those of the first embodiment.

Note that the present invention is not limited to the above-described embodiments, and for example, the wave plate may be manually rotated by the user instead of automatically rotating the wave plate after determining the type of recording medium.

[Effects of the Invention] As explained above, according to the present invention, when the recording medium is a magneto-optical recording medium, the polarization state changing means does not change the polarization state of the light incident on the recording medium, and the recording medium When the recording medium uses a method other than magnetism, by changing the polarization state of the light incident on the recording medium,
With a simple configuration, the present invention has the effect of enabling stable reproduction of both magneto-optical recording media and recording media using methods other than magneto-optical.

[Brief explanation of drawings]

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure is an explanatory diagram showing the main parts of the magneto-optical reproducing device, FIG. 2 is a block diagram showing the configuration of the magneto-optical reproducing device, FIG. 3 is a flowchart showing the rotation control of the quarter-wave plate, and FIG. 4 is the optical An explanatory diagram showing the polarization state at each part in Fig. 1 when reproducing a magnetic recording medium, and Fig. 5 shows each part in Fig. 1 when reproducing other recording media when the orientation of the quarter-wave plate is ±45°. 6 to 9 relate to the second embodiment of the present invention, FIG. 6 is an explanatory diagram showing the main parts of the magneto-optical reproducing device, and FIG. 7 is a total reflection mirror. FIG. 8 is an explanatory diagram showing the optical system between the magneto-optical recording medium and the recording medium, FIG. 8 is an explanatory diagram showing the polarization state at each part of FIGS. 6 and 7 during reproduction of the magneto-optical recording medium, and FIG. 9 is a half-wave plate. FIG. 7 is an explanatory diagram showing the polarization state at each part in FIGS. 6 and 7 during reproduction from other recording media when the azimuth is ±22.5°; FIG. 1... Optical pickup 11... Semiconductor laser 1
3...Beam splitter 14...1/4 wavelength plate 16...Recording medium 17.
...1/4 wavelength plate 18...Polarizing beam splitter 19a, 19b...Photodetector 24...Rotating means No. 4121 Fig. 5 Fig. 1 Also see 1. Finished... Figure 6 Figure 8 Figure 9

Claims (2)

[Claims] (1) A light source that emits light to irradiate a recording medium, an optical system that guides the light emitted from the light source to the recording medium, and an optical path separation means that separates the return light from the recording medium from the optical path that goes from the light source to the recording medium. , a magneto-optical reproducing device comprising a photodetecting means for detecting the returned light separated by the optical path separating means, wherein the optical system includes a light beam incident on the recording medium when the recording medium is a magneto-optical recording medium. It is characterized by providing a polarization state changing means capable of changing the polarization state of light incident on the recording medium when the recording medium is a recording medium using a method other than magneto-optical, without changing the polarization state of the light. A magneto-optical reproducing device. (2) The magneto-optical reproducing apparatus according to claim 1, wherein the polarization state variable means includes a wavelength plate provided in the optical system and means for rotating the wavelength plate.