JPS6284456A - Photomagnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To efficiently irradiate a light output from a light emitting source by arranging a Faraday rotating element between an information recording medium and a polarized beam splitter and providing a light isolator made of the 2nd polarized beam splitter and a Faraday rotating element. CONSTITUTION:A light beam emitted from the light emitting source 1 is collimated into a parallel beam by a collimate lens 2, and makes incident on the 2nd polarized beam splitter 13. The incident light beam passes through the splitter 12 without being hardly damaged. The light beam passing through the polarized beam splitter 13 makes incident on the Faraday rotating element 14, and the polarization orientation angle of a transmitting beam is rotated by 45 deg. against an advancing direction. After passing through a 1/2 wavelength plate 16, the light beam whose polarization orientation again points the direction of an axis (x) makes incident on the 1st polarized beam splitter 17, and passes through said splitter without being hardly damaged. Finally, the light beam passing through the 1st polarized beam splitter 17 is rotated by the Faraday rotating element 18, after which it is condensed and irradiated on the information recording medium 6 by an objective lens 5.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magneto-optical recording and reproducing device that utilizes the magneto-optical effect, and in particular, to an improvement in light utilization efficiency when recording information signals and when reproducing information signals. This invention relates to improvements in the signal-to-noise ratio (S/N) of reproduced signals and servo signals, and also to improvements in the reliability of the device.

[Conventional technology]

Figure 7 shows various documents and patent specifications (for example, Japanese Patent Laid-Open No. 584
No. 96640, Japanese Patent Application Laid-open No. 129955/1983.

This is an example of an optical system of a conventional magneto-optical recording/reproducing apparatus disclosed in Japanese Patent Application Laid-open No. 172176/1983.

In FIG. 7, 1 is a light emitting source such as a semiconductor laser that generates a light beam for recording and reproduction, 2 is a collimating lens that collimates the diverging light emitted from the light source 1 into parallel light, and 3
4 is a first beam splitter that transmits the parallel light from the collimating lens 2 in the direction of the information recording medium 6 and reflects the reflected light from the information recording medium 6 in the direction of the servo signal detection system 12; 4 is the beam splitter; A second beam splinter 5 transmits the parallel light transmitted through the information recording medium 6 in the direction of the information recording medium 6 and reflects the reflected light from the information recording medium 6 in the direction of the photodetector 11 for reproducing the information signal. This is an objective lens that condenses and irradiates the information recording medium 6 with the parallel light that has passed through the beam splinter 4 .

Further, 6 is an information recording medium such as a magneto-optical disk, and 7 is TbFe, TbFeCo, Gd having a magneto-optical effect.
A magnetic thin film such as Co, 8 is a bias magnetic field applying coil for applying a bias magnetic field during information signal recording. Furthermore, 9 is an analyzer for converting the polarization plane rotation in the reflected light from the information recording medium 6 into an intensity change, and a Glan-Thompson prism, a polarization beam splinter, or the like is used. 10 is a condenser lens for condensing the information signal light that has passed through the analyzer 9 onto a photodetector 11, and 11 is a photodetector for converting the information signal light into an electrical signal.

Next, the operation of the optical system of the conventional magneto-optical recording and reproducing apparatus will be explained. First, when recording an information signal, the diverging light emitted from the light emitting source 1 is collimated into parallel light by the collimating lens 2, transmitted through the beam splinter 3.4, and then passed through the objective lens 5 to the magnetic material inside the information recording medium 6. The thin film 7 is irradiated with focused light, and the temperature of the focused point on the magnetic thin film 7 is increased. Along with this, the coercive force near the focal point position decreases, and the bias magnetic field is applied in the direction perpendicularly penetrating the information recording medium 6 by the bias magnetic field applying coil 8, so that the light emitting source 1 blinks (luminous intensity 1M). Alternatively, the information signal is perpendicularly magnetically recorded in the information recording medium 6 by reversing the direction of the bias magnetic field (magnetic field modulation). Further, the reflected light from the information recording medium 6 passes through the beam splitter 4 again, is reflected by the beam splitter 3, and is transmitted to the servo signal detection system 1.
2 and is used to generate a focus error signal and a tracking error signal.

The operation during information signal reproduction is as described below. The operation of condensing the light beam emitted from the light emitting source 1 onto the information recording medium 6 is the same as the operation when recording information signals, and the optical power condensing and irradiating the information recording medium 6 is the same as that during recording. The only difference is that it is a fraction of the size.

Information signals are recorded in a magnetic thin film 7 in an information recording medium 6 to which a light beam for reproducing information signals is focused and irradiated, with the magnetization direction being either upward or downward with respect to the film surface. Since this magnetic thin film 7 has a Polar Kerr effect,
The polarization plane of the reflected light is rotated by a Kerr rotation angle of +〇length or -〇meng depending on the magnetization direction. Therefore, by detecting the rotational state of this plane of polarization, the information signal can be reproduced. In the conventional optical system shown in FIG. 7, the reflected light from the information recording medium 6 is reflected by the beam splinter 4 and enters the analyzer 9. Since the analyzer 9 converts the rotation of the plane of polarization in the reflected light into a change in light intensity, the light that has passed through the analyzer 9 is received by the photodetector 11, thereby reproducing the information signal as an electrical signal.

[Problem that the invention seeks to solve]

However, the conventional optical system having the above configuration has the following problems. The first problem is that the power of the light emitted from the light emitting source cannot be effectively used for recording information signals. This is because in current magneto-optical information recording and reproducing devices that irradiate an information recording medium with linearly polarized light and detect the rotational state of the polarization plane of the reflected light, the beam splitter that separates the irradiated light and the reflected light cannot be used as a beam splitter. , 1/4 as used in optical pickups for compact discs.
This is because a polarizing beam splinter combined with a wavelength plate cannot be used, so a beam splinter with a power transmittance of 50% to 90% for irradiated light must be used. In this case, 50% to 10% of the reflected light can enter the analyzer.

Now, the power transmittance Tl of the beam splitter 3.4 shown in FIG. 7 with respect to the polarization direction of the irradiated light.

Assuming that both T2 are 100%, the maximum optical power that can be focused on the information recording medium 6 is defined as Pma. Then, in an actual optical system, the maximum optical power that can be irradiated is (
TI ・T2) decreases to Pmaχ.

For example, typical values of Tl and T2 are 80% each.
, 70%, it is calculated that 44% of the optical power is actually wasted.

The second problem is that some of the reflected light from the information recording medium returns to the light emitting source, which may induce intensity-variable noise in the emitted light and disturb the spatial distribution of the output beam. This is a characteristic point. In particular, when a semiconductor laser is used as a light emitting source, the noise level generated by the returned light is higher than that of a gas laser such as a He-Ne laser, so deterioration of the S/H of the reproduction signal and servo signal is a major problem. It becomes. For example, Figure 8 is an example of the return optical noise characteristics of a high-power semiconductor laser reported in Takiguchi et al. [Reduction of Noise in Semiconductor Lasers for Optical Disks], 1981 IEICE Communication Division National Conference, S6-11. It has been shown that the noise intensity of the emitted light increases as the weight of the returned light increases. In the semiconductor laser shown in FIG. 8, as the return light weight increases from 0.01% to 1%, the relative noise intensity increases from 10 to 10'' (Hz-1), i.e.,
The noise level will increase by as much as 30 dB.

Next, the return optical noise level when this semiconductor laser is used in the conventional optical system shown in FIG. 7 will be estimated. The output power from the light source 1 is the collimating lens 2,
When the eclipse rate by the objective lens 5 is η and the output power of the light emitting source 1 is PO, the power of the light focused and irradiated onto the information recording medium 6 is (TI·T2·η) PO. Further, if the reflectance of the information recording medium 60 is ηdif, the reduction rate of the optical power due to diffraction of the irradiated light by the tracking groove carved in the R1 information recording medium 6 is expressed as
The optical power p returned to the light emitting source 1 is Pa=(R・ηdt
f −T1・T,) (T,・T2・η)PO・・
・(1) becomes. Therefore, the return light weight is r, = 'IR・ηdif H('r, -T,)''
・=(2), for example, the power transmittance TI of the beam splinter 3.4 with respect to the polarization direction of the irradiated light,
T2 is the value used in explaining the first problem above (T1-0
．． 8, T2 = 0.7>, and η is 0.4.
Assuming that R is 0.15° and ηdif is 0.67, the returned light weight r is approximately 2%. At this time, the relative intensity of the returned light noise is about 10-1'(Hz-') from Fig. 8, and this value is the minimum noise intensity (10-1') required for digital recording.
It is one order of magnitude higher than 0 (Hz-1)).

The third problem is that the reflected light from the information recording medium cannot be effectively used for reproducing information signals. That is,
If the reflected light power from the information recording medium 6 is Pi, especially the light power incident on the analyzer 9 (equal to the reflected light power of the beam splitter 40), the above Pi is Pi=(1-72)P...・(3
). Here, T2 is the power transmittance of the beam splinter 4 described above. Also, the angle from the extinction position of the analyzer 9 is θa, and the signal current output by the photodetector 11 is I
s, the above Is is I S oc p 1-sin
2θa, 5in2θ ・(41) It is known that it is proportional to the analyzer incident power. Therefore, when a T2-50% beam splinter 4 is used, the analyzer incident light power is 1 of the reflected light power. /2, resulting in a decrease in the S/N of the reproduced signal.

By the way, if the power transmittance T2 of the beam splinter 4 is reduced in order to prevent the S/N reduction of the reproduced signal, a problem arises in that the irradiation power to the information recording medium 6 during information recording is reduced. T2 cannot be reduced unnecessarily.

FIG. 9 shows the electric field vector h of the reflected light from the information recording medium 6 and the electric field vector 11 and the detected electric field after being reflected by the beam splitter 4 when a beam splitter 4 with T=50% is used. It shows the state of the electric field vector E1 after the photon has passed.

However, by using a beam splinter with different transmittances (reflectances) for the p-polarized light component and the s-polarized light component, the decrease in the analyzer incident light power Pi caused by the beam splinter can be compensated for by multiplying the Kerr rotation angle θ ( A method is shown in Japanese Patent Application Laid-Open No. 58-196640, etc. This method is based on the fact that when using the optical system shown in FIG. (p-polarized light with respect to beam splitters 3 and 4), the p-polarized light power transmittance TZ of beam splitter 4 is
Set P to 50% or more (set it to 70% from now on), and set S to
This is a method in which the polarization power reflectance R29 is approximately 100%.

FIG. 10 shows the state of the electric field vector E122± after being reflected by the beam brick 4 and the electric field vector I2 after passing through the analyzer when using the beam splinter 4 having the above characteristics.

Since the beam splitter 4 reflects almost 100% of the signal component (electric field component in the y direction) in the reflected light, the Kerr rotation angle of the light after being reflected by the beam splitter 4 increases from term 6 to θ'. is clearly seen from the figure. However, even if a beam splitter having the above characteristics is used in a conventional optical system, the first. The second problem and the fourth problem described later. The fifth problem cannot be solved.

The fourth problem is that the reflected light from the information recording medium cannot be used effectively for servo signal detection, and this problem reduces the amount of light incident on the servo signal detection system, causing focus error signals and There is a risk that the S/N of the tracking error signal will decrease.

For example, regarding the optical system shown in FIG. 7, the proportion of light reflected from the information recording medium 6 that enters the servo signal detection system 12 is
T2・(1-T1). Here, TI and T2 are the beam splinter 3 for the polarization direction of the irradiated light, respectively.
, 4, and if Tl and T2 are the values 0.7 and 0.8 used in the explanation of the first problem, only about 14% of the reflected light reaches the servo signal detection system. This means that it cannot be input.

The fifth problem is that the arrangement is such that the light irradiating the information recording medium and the light reflected from the information recording medium are separated, and a portion of the reflected light is directed to a photodetector for reproducing the information signal. The problem is the phase shift between s and p polarized light that occurs in a beam splinter. Now, suppose that the reflected light from the information recording medium is linearly polarized light that has been rotated by θ (rotated) with respect to the polarization direction of the irradiated light, and the phase difference generated between the S and P polarized lights of the reflected light by the beam splitter is expressed as δ. Then, the reproduced signal current Is becomes co
It decreases in proportion to sδ. For example, if δ-45°, the reproduced signal current will decrease by 3 dB.

Therefore, it is necessary to select a beam splitter that has a sufficiently small phase shift between S+ and p polarized light in the vicinity of the wavelength used.

This invention was made in order to solve the above-mentioned problems, and at the same time increases the proportion of the light output that can be focused on the information recording medium out of the light output emitted from the light emitting source when recording information signals. It is an object of the present invention to provide a magneto-optical recording and reproducing apparatus that can improve the S/N of a reproduced signal and a servo signal when reproducing an information signal.

Means for Solving Problem C] The magneto-optical recording and reproducing apparatus according to the present invention uses a polarizing beam splitter as a beam splitter that separates light irradiated onto an information recording medium and information signal light from the information recording medium, and A Faraday rotation element is placed between this polarization beam splitter and the objective lens, or in addition to this, an optical isolator consisting of a second polarization beam splitter and a Faraday rotation element is placed immediately after the collimating lens. be.

[Effect]

In this invention, when reproducing an information signal, a Faraday rotation element placed between a polarizing beam splitter and an objective lens rotates the plane of polarization of reflected light, and this polarizing beam splitter functions as an analyzer.

Furthermore, when an optical isolator is placed, the loss of the irradiated light from the polarizing beam splitter placed between the light emitting source and the information recording medium is 0, and the reflected light is transmitted without being reflected by the first polarizing beam splitter. The remainder is all reflected by the second polarizing beam splitter constituting the optical isolator and enters the servo signal detection system.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In the figure, numerals 1, 2.5 to 8, and 10 to 12 are exactly the same as the conventional device shown in FIG. Reference numeral 13 transmits the parallel light from the collimating lens 2 in the direction of the information recording medium 6, and directs all the remaining light reflected from the information recording medium 6 that is not used for information signal reproduction in the direction of the servo signal detection system. This is a second polarizing beam splitter for reflecting light into the beam, and its reflecting surface is coated with a dielectric multilayer film. Further, 14 is a Faraday rotation element whose Faraday rotation angle is set to 45 degrees, 15 is an optical isolator consisting of the second polarizing beam splitter 13 and the Faraday rotation element 14, and 16 is a rotation of the polarization direction of the transmitted light in a predetermined direction. The 1/2 wavelength plate 17 transmits the parallel light that has passed through the isolator 15° 1/2 wavelength plate 16 in the direction of the information recording medium 6, and also increases the intensity of polarization plane rotation in the reflected light from the information recording medium 6. A second polarization beam splitter for converting the polarization into a polarized beam.

A Faraday rotation element 18 provides a difference in polarization azimuth equal to the analyzer angle θa between the light irradiated onto the information recording medium 6 and the light reflected from the information recording medium 6.

Next, the operation of this embodiment shown in FIG. 1 will be explained using FIGS. 2 and 3. FIGS. 2 and 3 schematically represent the polarization azimuth of a light beam propagating through the optical system of this embodiment.

First, the operation when recording information signals will be explained. 1st
In the figure, diverging light emitted from a light emitting source 1 is collimated into parallel light by a collimating lens 2, and enters a second polarizing beam splitter 13. By the way, as shown in FIG. 2, since the polarization direction of the light emitted from the light emitting source 1 is set to be in the p polarization direction (X-axis direction) with respect to the reflective surface of the polarization beam splitter 13, the polarization beam splitter The light beam incident on 13 passes through it with almost no loss. This is because the polarizing beam splitter 13 has an optical property that the p-polarized light power transmittance is approximately 100%. The light beam that has passed through the polarizing beam splitter 13 is incident on the Faraday rotation element 14, and the polarization azimuth of the transmitted light is rotated by 45 degrees toward the traveling direction (z-axis direction) of the light beam, as shown in FIG. 2, for example. be done. The light beam that has passed through the Faraday rotation element 14 is then
/2 wavelength plate 16. The half-wave plate 16 has a function of rotating the plane of polarization of incident light in a predetermined direction by appropriately setting its fast axis. The wavefront is rotated 45 degrees.

After passing through the 1/2 wavelength plate 16, the light beam whose polarization direction becomes the X-axis direction again enters the first polarization beam splinter 17.

The polarization direction of the incident light beam is polarization beam splitter 1.
The polarization beam splitter I7 has a p-polarization direction with respect to the reflective surface of the second polarization beam splitter, and the p-polarization power transmittance of the polarization beam splitter I7 is almost 100%, so the incident light beam has almost no loss. Pass this without getting covered.

Finally, as shown in FIG. 3, the light beam that has passed through the first polarizing beam splitter 13 has a polarization plane of θa/2 (several degrees to
After being rotated (several tens of degrees), the objective lens 5 irradiates the information recording medium 6 with condensed light. The bias magnetic field is applied to the information recording medium 6 by the via large magnetic field applying coil 8, as in the conventional example.

From the above explanation, it can be seen that the first problem in the conventional example is solved in this embodiment.

That is, in the conventional example, the loss of the irradiation light from the beam splitter placed between the light source 1 and the information recording medium 6 was a non-negligible amount of several tens of percent, but in this embodiment, the loss of the irradiation light from the beam splitter is non-negligible. In principle, the loss to light is O. Therefore, if the optical system of this embodiment is used even on an information recording medium having the same recording sensitivity, it is possible to record with a lower output from the light emitting source than in the conventional example. This means that it is possible to further improve the reliability of current magneto-optical recording and reproducing devices, which mostly use semiconductor lasers as light-emitting sources, whose lifetime is rapidly shortened as the light-emission output increases. Conversely, when the light output that can be extracted from the light emitting source is limited, the light output that the optical system of this embodiment can irradiate onto the information recording medium increases compared to the conventional example, resulting in lower sensitivity. It can also be recorded on an information recording medium.

Next, the operation during information signal reproduction will be explained.

The light beam emitted from the light emitting source 1 is focused and irradiated onto the information recording medium 6 in exactly the same way as when recording the information signal; the difference is that the power of the light irradiated onto the information recording medium 6 is lower than when recording. (0.5-2mW) points only. As shown in FIG. 3, the polarization plane of the light irradiated onto the information recording medium 6 is X.
It is rotated by θa/2 with respect to the axis. Therefore, the plane of polarization of the reflected light from the information recording medium 6, which has undergone Kerr rotation of ±θ4 depending on the magnetization direction, is in the direction of θa/2±θ4 with respect to the X axis. This reflected light passes through the objective lens 5 again and enters the Faraday rotation element 18 again. Since the Faraday rotation angle of the Faraday rotation element 18 is set to θa/2, the polarization azimuth angle after passing through the Faraday rotation element for one day becomes θa±θ wide with respect to the X axis.

FIG. 4 shows the state of the reflected light electric field vector after passing through the Faraday rotation element. No. (E, -)
is the reflected light that has undergone Kerr rotation of +θ (−θ4). The reflected light that has passed through the Faraday rotation element 18 is incident on the first polarization beam splinter 17 . Since the polarizing beam splitter 17 has a characteristic of reflecting only the S-polarized light component on its reflecting surface, the polarizing beam splitter 17
If the electric field vector of the light reflected by is τ, then
The electric field amplitude E3±(-103th1) is E 31 =
E RS in (θa±θJ) −(
5) However, ER=lER,1. Therefore, the polarization beam splinter 17 acts as an analyzer that converts the rotation of the plane of polarization in the reflected light into a change in light intensity. Furthermore, it is noteworthy that the reflected light from the information recording medium 6 is incident on the polarizing beam splinter 17, which is an analyzer, without being attenuated. The reflected light from the polarizing beam splinter 17 is focused onto the photodetector 11 by the condensing lens 10, and an information signal as an electrical signal is output from the photodetector 11.

As described above, in this embodiment, it is possible to make all of the reflected light from the information recording medium incident on the analyzer without attenuating it. Therefore, the third problem is solved.

Furthermore, at the end of the reproduction operation, the remaining component of the reflected light from the information recording medium 6 that has passed through the polarization beam splinter 17 passes through the 1/2 wavelength plate 16 and the Faraday rotation element 14 again. As shown in FIG. 2, these two elements cause the polarization direction of the reflected light to point in the y-axis direction, and the reflected light is all reflected by the next second polarization beam splinter 13, which detects the servo signal. This leads us to Corollary 12. Therefore, the reflected light from the information recording medium 6 does not reach the light emitting source 1. In reality, since the extinction ratio of the collimating lens 2 and the polarizing beam splinter 13 is not 0, the return light to the light emitting source 1 is not completely eliminated, but its value is not large enough to cause a problem. Therefore, the noise of the light emitting source induced by the returned light is significantly reduced, and the second
problem is solved.

Furthermore, in this embodiment, the fourth problem mentioned above can also be solved because all of the light reflected from the information recording medium except for the light necessary for reproducing the information signal is guided to the servo signal detection system. .

Furthermore, in this embodiment, since no optical element that could cause a phase shift between orthogonal polarized lights is disposed between the information recording medium and the analyzer, the fifth problem is also solved.

In the above embodiment, a polarizing beam splitter with a dielectric multilayer film applied to the reflective surface was used to separate the light irradiated onto the information recording medium and the light reflected from the information recording medium, but instead of these, a polarizing beam splitter was used. It is clear that it is also possible to use crystal prisms such as , Lochon prisms, Wollaston prisms, etc.

Also, in the above embodiment, a 1/2 wavelength plate is used, but
This is not essential, and can be eliminated by shifting the optical axes of the upper and lower optical systems that sandwich the 1/2 wavelength plate from each other by 45 degrees.

Furthermore, in the above embodiment, an apparatus was described that was equipped with an optical isolator 15 consisting of not only the first polarization beam splinter 17 and the Faraday rotation element 18 but also the second polarization beam splinter 13 and the Faraday rotation element 14.
In the present invention, the above-mentioned optical isolator 15 may be omitted, and in this case also the above-mentioned third. This solves the fifth problem.

Figure 5 is a diagram showing the main parts of the above embodiment.As shown in this figure, the magneto-optic effect can be utilized by simply attaching the main parts to a suitable collimating optical system and servo signal detection system. It becomes possible to reproduce the information signal from the information recording medium.

Further, FIG. 6 shows an optical system in the above embodiment when the polarization direction of the irradiated light is selected to be S-polarized light with respect to the reflection surface of the polarizing beam splitter 16. The optical system in Fig. 6 is a collimating optical system and a servo signal detection system 19.
Fix the objective lens 5. Faraday rotating element 17. Polarized beam splinter 16. Condensing lens 10. Photodetector 1
It is suitable for a magneto-optical recording/reproducing device in which the optical disc 1 is integrally movable.

〔Effect of the invention〕

As described above, according to the present invention, a polarizing beam splinter is used as a beam separation means for separating light irradiated onto an information recording medium and light reflected from the information recording medium, and the information recording medium and the polarizing beam splinter are Since a Faraday rotation element is placed between the two, the polarizing beam splitter also acts as an analyzer when reproducing the information signal, so that all of the reflected light from the information recording medium enters the polarizing beam splitter, which is the analyzer. , there is an effect that a high S/N ratio of the reproduced signal can be obtained. Furthermore, if an optical isolator consisting of a second polarizing beam splitter and a Faraday rotation element is provided, and the polarizing beam splitter is arranged so that the loss to the irradiated light from both polarizing beam splitters is almost negligible, the light output from the light source can be efficiently It has the effect of being able to irradiate the information recording medium well and improving the reliability of the device.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a magneto-optical recording/reproducing apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 show the state of polarization direction of a light beam traveling through the optical system of the above embodiment. FIG. 4 is a diagram for explaining the state of the electric field vector of the reflected light from the information recording medium and the electric field hector of the information signal light reflected by the second polarization beam splinter and directed toward the photodetector in the above embodiment. FIG. 5 is a schematic configuration diagram showing the main parts of the above embodiment, FIG. 6 is a schematic configuration diagram showing another embodiment of the present invention, and FIG. 7 is a conventional magneto-optical recording/reproduction diagram. A schematic configuration diagram showing an example of the device, FIG. 8 is a characteristic diagram showing the relationship between the return light weight and the relative noise intensity of the noise induced by the return light in a high-power semiconductor laser, and FIGS. 9 and 10 are the conventional FIG. 2 is a diagram showing the state of the electric field vector of light before it enters an analyzer and after passing through the analyzer, of the light reflected from the information recording medium in the magneto-optical recording/reproducing device. In the figure, 1 is a light emitting source, 6 is an information recording medium, 11 is a photodetector, 13.17 is a polarized beam splinter, 14.1
8 is a Faraday rotation element, and 15 is an optical isolator. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 001 0.1110 ノCriAζ invasion? (0m) Figure 9 ■ Figure 10 y Procedural amendment (voluntary) 1. Indication of case Patent application No. 60-225899
No. 2, Name of the invention Magneto-optical recording and reproducing device 3, Person making the amendment 5, Detailed description of the invention in the specification to be amended 6, Contents of the amendment + 11 Change rTJ on page 11, line 10 of the specification to “ T2”
Correct to. (2) Delete "At the end of the above playback operation" in the fourth line of page 22. (3) On page 22, line 14, "lens 2" is corrected to "there is reflected light from lens 2."that's all

Claims (6)

[Claims] (1) A magnetic thin film having a magneto-optical effect is used as an information recording medium, and a beam separating means separates a beam irradiated from a light emitting source to the information recording medium and a beam reflected from the information recording medium, and the reflection. In a magneto-optical recording and reproducing device having a photodetector for receiving a beam of light and reproducing an information signal, a polarizing beam splitter that can almost completely separate two orthogonal polarized components without loss is used as the beam separating means. , a Faraday rotation element that rotates the polarization plane of light regardless of the traveling direction of the light is disposed between the information recording medium and the light beam separation means, and the polarization beam splitter acts as an analyzer. A magneto-optical recording and reproducing device. (2) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the polarizing beam splitter as the beam separating means has a dielectric multilayer film applied to a reflective surface. (3) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the polarizing beam splitter as the beam separating means is a Rochon prism or a Wollaston prism. (4) An optical isolator is disposed between the light emitting source and the light beam separating means to prevent reflected light from the information recording medium from returning to the light emitting source. The magneto-optical recording and reproducing device according to item 1. (5) The magneto-optical recording and reproducing apparatus according to claim 4, wherein the optical isolator comprises a second polarizing beam splitter whose reflective surface is coated with a dielectric multilayer film and a Faraday rotation element. . (6) The magneto-optical recording and reproducing apparatus according to claim 4, wherein the optical isolator is composed of a Rochon prism or a Wollaston prism and a Faraday rotation element.