JPS58196640A - Magnetooptic recording and reproducing device - Google Patents

Abstract

PURPOSE:To ensure good recording without increasing the output of a light source and at the same time to improve the S/N of reproduced light, by providing a beam splitter having different values of transmissivity to the P and S polarizations of the recording/reproducing light to an optical system. CONSTITUTION:A beam splitter 14 is set between a laser diode 1 functioning as a laser light source for recording/reproducing and a recording medium 6. When a laser beam receives P polarization, the transmissivity is set at <=50% for the P polarization component. While the transmissivity of the S polarization component is set at 100%. As a result, the >=50% laser beam is made incident to the medium 6 to ensure the satisfactory writing of information. Furthermore, the polarization component, i.e., the signal component which is turned by a Kerr effect can be led nearly 100% toward a photodetector 11. This process improves the S/N of the reproduced light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording and reproducing device that utilizes the magneto-optical effect, and particularly to means for improving the recording and reproducing efficiency of an optical system.

FIG. 1 is a diagram showing an example of an optical system in a conventional glaze magneto-optical character arrangement M'. In Figure 1, 1 is a Raded diode as a light source that emits a light beam for recording and reproduction, 2 is a collimating lens that collimates the beam into parallel light, and 3 is a collimating lens that collimates the beam output from the Raded diode. It is a polarizer that polarizes light. Further, 4 is a beam splitter that reflects the light from the upper V polarizer 3 toward the recording medium and transmits the reflected light from the recording medium toward the detector, and 5 is the light from the upper F beam splitter 4. 6 is a recording medium made of, for example, a magneto-optical disk, 7 is a bias magnetic field applying coil for applying a 74'' IA magnetic field during recording. A beam splitter that divides the reflected light from the recording medium 6 that has passed through the beam splitter 44 into the thermal signal detector direction and the information signal detector direction, and is used when obtaining a focus error signal using 9d astigmatism. A cylindrical lens 10 indicates a focus error signal and a track error signal.
This is a ti-& system signal detector for detecting system signals. Reference numeral 11 denotes an analyzer for obtaining signal light from the rotational state of the plane of polarization in the reflected light from the recording medium 6, and is composed of a birefringence norism such as the Glan-Thompson rhythm, or a polarized beam ray. Reference numeral 12 denotes an information signal detector which converts the upper P information signal light into an electric signal to obtain an information signal of image information type.

According to the conventional optical system with such a configuration, for example, when P-polarized light is incident on the recording surface of the recording medium 6, the polarization plane of the P-polarized light changes as shown in FIG. 2 according to the direction of magnetization of the recording surface. +θK
Alternatively, it will rotate by a Kerr rotation angle of 1 θ.

Therefore, by detecting the rotational state, an information signal can be obtained. However, the top! Conventional optical systems with the H configuration have the following problems.

In other words, the reflectance of the beam splitter 4 is set to 81, the intensity of the reflected light from the recording medium 6 is calculated, and the transmitted light intensity when this reflected light passes through the beam splitter 4 in the direction of the signal detector 12. is 1, the transmitted light intensity It=(1-Rl)I"□". Therefore, the commonly used R1=5(l
When using a beam splitter, the transmitted light intensity It becomes a bar of reflected light intensity. Note that -1 reflected light intensity is a bar of laser beam intensity. Therefore, when the signal light intensity It, which is the signal light intensity, decreases significantly, it becomes K. In order to improve the above 1'N, the reflectance R1 is made small, and the transmitted light intensity It is relatively
If the value is increased, the amount of light incident on the recording medium 6 during recording will decrease, making it impossible to perform high-quality recording.

Particularly if the sensitivity of the recording medium 6 is relatively low, there is a possibility that the arrangement may not be possible. Another way to improve S/J is to increase the output of the laser diode 1 to increase the intensity 1 of the reflected light from the measuring medium 6. This will have a significant effect on Rubb and shorten the life of the device.

The same can be said about the other beam splitter 8 during the above period fJi,t.

The present invention solves the problems of such conventional devices 1, v-
y'/4o p*o+s. It is an object of the present invention to provide a magneto-optical recording reassignment device with a simple configuration that can perform good recording on 8 chips and 1, and can improve the S/N of reproduction light.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing an optical system according to an embodiment of the present invention. However, the same parts as in FIG. 1 are given the same reference numerals, and detailed explanations of those parts will be omitted. The difference between FIG. 3 and FIG. 1 is that the polarizer 3 is removed, and by providing a multilayer dielectric film on the reflective surface, the transmittance for the P-polarized light component and the 8-polarized light component is different. This is because a beam splitter 14 is used.

That is, the conventional beam sintering device 4 called a half mirror has a transmittance and a reflectance of 5° regardless of the polarization component, but the beam sintering in this device
When the laser beam receives P-polarized light, I4 has a transmittance of 50 cm or less for the Fip-polarized component, and S
The transmittance is set to 100% for polarized light components.

Therefore, when recording, the recording laser beam s
The dower of o4 or more is reflected by the beam series 414 and is focused and irradiated onto the recording medium 6. As a result, sufficiently good writing can be performed regardless of whether the sensitivity of the recording medium 6 is good or bad.

Also, during reproduction, the reproduction laser beam 501
Since the above light is condensed and irradiated onto the recording medium 6, the recorded information can be reliably read.

On the other hand, the reflected light from the recording medium 6 is rotated by only +θK or 1θ due to the Kerr effect, as described above.

FIG. 4 is a diagram showing the state when rotated only to +θ. As is clear from this figure, the light intensity IP of the P polarization component RP and the light intensity [I
S is the intensity 1 of the reflected light from the recording medium 6 when it is not subjected to Kerr rotation, where l is IP = Ias2119K...
・・・・・・・・・(1) I8=1*20K ・・・Song...Song...(2) Therefore, the car rotation angle θ
It is expressed as.

Now, if the light transmittance for the P-polarized light component of the beam currant 14 is TP, and the light transmittance for the 8-polarized acid is TS, then the P-polarized light component RP of the light transmitted through the beam splitter 14 is
'light intensity I P' and light intensity I of S polarization component RS'
S' is obtained from equations (1) and (2), IP' = TP - IP
= TP・■326K・・・・・・・・・(4)I8
'= TS - Is = TS - Igln2θK...
...<5). Here, TP is less than 50% and TS is almost 100%, so IP'≦卜P ・・・・・・・・・・・・・・・・・・
(6) Is'ζIs ・・・・・・・・・・・・
...(7). As a result, as shown in FIG. 4, the apparent Kerr rotation angle θ becomes large. This θ becomes ′.

By the way, if the ellipticalization of the reflected light from the recording medium 6 is ignored, the S-polarized light component Is, which is a signal component, is determined by the following formula: IA is the intensity of light incident on the analyzer 11, θA is the analyzer setting angle, and Kerr rotation angle is When θ, it is given by l5-=IA*2θAg1n2θ. Therefore, the decrease in the intensity IA of the incident light on the analyzer 11 due to the beam snorriter 14 or the like can be compensated for by increasing the Kerr rotation angle θK. In this way, as mentioned above, by increasing the Kerr rotation angle from θK to θ′, it is possible to prevent the intensity of light incident on the analyzer 11 from decreasing 1r-IA, and to improve the S/N ratio. However, as mentioned above, by reducing the transmittance TP of the P-polarized light component, the apparent Kerr(b) turning angle θ increases, but if the transmittance of the P-polarized light component is extremely reduced, the light intensity The absolute value of the signal decreases, and it becomes impossible to obtain a sufficient signal for focus control and tracking. Therefore, it is desirable that the S-polarized light component, which is the signal component in this case, be transmitted as its-signal component, and that the P-polarized light component, which acts as a mere nozzle, be transmitted by an appropriate amount of 50% or less.

In addition, in this device, the transmittance is set to 50- or less, and the transmittance is set to 50- or less.
The reason why this is set as the upper limit is that if a reflection of 50- is obtained during recording, writing to the recording medium 6 can be performed without any trouble, and the signal level for the female system during playback can also be made sufficiently large. be. In the case of the above-mentioned 50 inches, the force is the same as in the case of using a half mirror. The beam splitter 414 of the tsuma-shu book apparatus functions in the same manner as a conventionally used half mirror in directing the radar beam for recording and reproducing, and is characterized in that it functions to transmit approximately 100 beams of signal components.

In addition, in this device, the polarizer 3 shown in FIG.
Another feature is that it can be omitted. That is, the polarizer 3
is provided especially to further improve the degree of polarization of the Rade beam emitted from the Rade diode I during reproduction, but in this device, even if the polarizer 3 is not used, when reproducing using P-polarized light, for example. The S-polarized light is transmitted slowly by the beam sinter 14, and only the P-polarized light component is incident on the recording medium 6. As a result, the polarizer 3 can be omitted.

FIG. 5 is a diagram showing another embodiment of the present invention, in which the same parts as in FIG. 3 are given the same reference numerals. Taking as an example the case where the beam currant 24 shown in FIG.
The reflectance for the P-polarized light component is set to 50- or less, and the reflectance for the S-polarized light component is set to 100-. Therefore, P-polarized light components of 50- or more are incident on the recording medium 6 as in the case of FIG. 3, and the reflected light from the recording medium 6 is 50-
The following P polarized light components and 100- S polarized light components are reflected by the reflecting surface and guided to the detector side. Beam splitter 2 above
The Radhe beam reflected by the cylinder lens 25. The light is supplied to a detector 27 via an analyzer 26. The detector 27 is an integrated detector that simultaneously detects a signal of the circuit C system and an information signal, and the detected signal is separated by a signal processing circuit (not shown).

The apparatus configured as shown in FIG. 5 has the advantage that the beam splitter 8 shown in FIG. 3 for extracting the thermal signals can be omitted.

Note that the present invention is not limited to the embodiments described above. For example, in the first embodiment shown in FIG. 3, a case has been described in which the laser beam from the laser diode I is P-polarized, but even when it is S-polarized, the transmittance of the beam splitter 14 is By setting the polarization component to 50 or less for 10018 polarization components, the same effects as in the above embodiment can be obtained.

In addition, in the first embodiment, Beam Suge IJ, 414
Regarding; only the case where the transmittance for the P-polarized light component and the transmittance for the S-polarized light component are different is illustrated, but the beam sushiri.

The same transmittance settings as in 14 may also be made for 8th. However, in the Beam Sderby 48, if the light incident on the recording medium 6 is P-polarized, it will be S-polarized incident on the reflective surface of the Beam Sderby 418.
In this case, the transmittance of the beam filter 48 for each polarization component may be 100 or less for the P polarization component and 50 or less for the S polarization component.

By doing so, the same effect as that in the beam splitter Z4 will occur in the beam splitter 8 as well. Therefore, it is possible to obtain a signal without reducing the S/N. This means that the amount of light necessary for the system can be secured.

As explained above, according to the present invention, one of the P-polarized component and the S-polarized component of the recorded and reproduced light is transmitted between the light source and the recording medium at a transmittance of 100% (or a reflection of 50- or less). Since we installed a beam splitter with one side having a transmittance of less than 50 degrees (or a reflectance of 100 degrees), the laser beam of more than 50% is incident on the recording medium to obtain sufficient information. It becomes possible to perform writing or reading, and it also becomes possible to guide the polarized light component, that is, the signal component rotated by the Kerr effect, to the approximately 100-detector side with appropriate power. Therefore, it is possible to provide a magneto-optical recording/reproducing device with a simple configuration, which can perform good I-recording without changing the output of a light source such as a laser diode, and can improve the S/N of reproduction light.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an optical system of a conventional device, FIG. 2 is a diagram showing the state of Kerr rotation of the device shown in FIG. 1, and FIG. 3 is a diagram showing the configuration of an optical system in an embodiment of the present invention. Figure 4 showing
The figure is a principle diagram for explaining the operation of the embodiment, and FIG. 5 is a diagram showing the configuration of an optical system in another embodiment of the present invention. 1... Laser diode (light source), 2... Collimator lens, 4.8. It, 24... Beam splitter, 3... Polarizer, 5... Objective lens, 6... Recording medium, 7... Bias magnetic field application coil, '9.25.
... Cylindrical lens, IO... Sir? System signal detector, IZ, 26... Analyzer, 12... Information signal detector, 21... Integrated type detector. Applicant's representative Patent attorney Hikosai Suzue 1 Zusai 2 Section 103 Zusai 4 S S. 5 Procedural amendment 1980 r. January 1; 57-79502 No. 3, Relationship with the case of the person making the amendment Patent applicant (037) Orino Zos Optical Industry Co., Ltd. 4, Agent 6, Full text of the specification to be amended 7, Contents of the amendment

Claims (1)

[Claims] Between the light source and the recording medium, one of the P-polarized light component and the S-polarized light component of the recording/reproduction light has a transmittance of 100- (or a reflectance of 50 or less) and the other has a transmittance of 50% or less. What is claimed is: 1. A magneto-optical recording/reproducing device characterized in that a beam beam is provided with a reflectance of 100 cm (or a reflectance of 100 cm).