JPS60121558A - Optical magnetic reproducing device - Google Patents

Abstract

PURPOSE:To prevent large attenuation of a polarization component of an optical magnetic reproducing device and to improve reproduction sensitivity by giving polarization characteristics to the beam splitter itself. CONSTITUTION:A beam splitter 13 has the following reflection factor R and a transmittivity T for the light which is emitted from a laser diode 1 and passes through a collimator lens 2: In other words, for the S wave having the oscillation face in the paper-face vertical direction and the P wave having the oscillation face inside the paper face, a reflection factor Rp is set to be smaller than Rs, and a transmittivity Ts is set to be smaller than Tp. The polarization face of the laser beam from the laser diode 1 coincides with the S wave. Bu such a constitution, the polarization degree of the laser light which is emitted on a recording medium 5 side increases by Rs/Rp times. For the transmission light which transmits a beam splitter 13 and goes to the light receiver side after having reflected at the recording medium 5, a Kcrr rotational angle is increased by Tp/ts times.

Description

[Detailed Description of the Invention] <Field of Application in the fL Industry) This invention provides a magneto-optical reproducing device with improved reproduction sensitivity by imparting polarization characteristics to the beam splitter itself. A.

(Prior art and its problems) FIG. 1 shows the configuration of a conventional magneto-optical reproducing device.

As shown in the figure, in the conventional magneto-optical reproducing device (
The light emitted from the laser diode 1 is guided through the collimator lens 2 to the polarizer 3, where the accuracy of linear polarization is increased, and then the light transmitted through the polarizer 3 is guided through a half mirror with approximately equal transmission and reflection. After being refracted by 90° toward the recording medium 5 by the constructed beam splitter, it is guided to the recording surface 5a of the recording medium 5 via the converging lens 6.

Next, the reflected light reflected by the recording surface is again converged by the converging lens 6, and then transmitted through the beam splitter 4 and extracted.

Here, as is well known, in the magneto-optical reproducing system, recorded information can be reproduced based on the polarization component of this transmitted light. Specifically, after the transmitted light beam is split into two systems by the beam splitter 7 having the same configuration as described above, one of the beams is guided to the light receiving element 9 via the analyzer 8, and the other is guided to the light receiving element 9 via the analyzer 10. The light is guided to the light receiving element 11 via the.

By calculating the outputs of the light receiving elements 9 and 11 using the differential amplifier 12, it is possible to obtain output information at a stable level regardless of changes in the start-up of the light source.

However, in such a conventional magneto-optical reproducing device, the degree of polarization of the laser diode 1 is generally insufficient, so in order to sufficiently increase the detection sensitivity of Kerr rotation, a polarizer is installed before the beam splitter 4. 3 to increase the accuracy of linearly polarized light.

In addition, since a half mirror is used as the beam splitter 4, in which transmission and reflection are approximately equal, the reflected light reflected by the recording medium 1 is greatly attenuated while passing through the beam splitter 4. Since the rotation of the polarization plane due to the effect is only about 0.3 to 1° relative to that of the incident light, information 11
Was.

(Object of the Invention) The object of the present invention is to eliminate the need for a polarizer in front of the beam splitter to increase the accuracy of linear polarization by J5 in this type of magneto-optical reproducing device, and to
The objective is to prevent polarized light components corresponding to reproduced information from being greatly attenuated while passing through a beam splitter, thereby improving reproduction sensitivity.

(Structure of the Invention) In order to achieve the above object, the present invention reflects light from a laser light source by a beam splitter and then irradiates it onto a magneto-optical recording medium, and the light reflected by the recording medium is directed to the magneto-optical recording medium. A magneto-optical reproducing device that transmits light through a beam splitter and reproduces recorded information based on the polarization component of the transmitted light is characterized in that the beam splitter itself has polarization characteristics.

(Description of Embodiments) FIG. 2 is a schematic diagram showing the configuration of a magneto-optical reproducing apparatus according to the present invention. In this figure, the same reference numerals are used for the same components as in FIG. 1, and the explanation thereof will be omitted.

The feature of this embodiment is that the light emitted from the laser diode 1 and passed through the collimator lens 2 is immediately guided to the beam splitter 13.

That is, this beam splitter 13 has the following characteristics.

For example, for light with a vibration plane perpendicular to the plane of the paper (hereinafter referred to as an S wave for a beam splitter) and light with a vibration plane within the plane of the paper (hereinafter referred to as a P wave), Reflectance: R8: 0.3-0.8 Rp: transmittance smaller than Rs; ]-8: 0.2-0.7 Tp: 0.5-1.0 (Tp>Ts) However, Rs
→−Ts≦1°FLp+Tll≦1.

The plane of polarization of the laser beam from the laser diode 1 is made to match the S wave.

According to such a configuration, the degree of polarization of the laser beam that enters the beam splitter 13, is reflected by the beam splitter, and is emitted toward the recording medium 5 side increases to R8/R11lB.

Also, after being reflected by the recording medium 5, the beam splitter 1
Regarding the transmitted light ray that passes through 3 and reaches the receiver side, K
The err rotation angle can be increased by a factor of TIE/Ts, and therefore the reflected light having a small kerr rotation angle can be sent to the light receiver without weakening.

In addition, °[p is as large as possible, Rp is preferably as small as possible, and Rs or S is preferably 0.
Around 5 is preferable.

Furthermore, it goes without saying that the relationship between S waves and P waves may be completely reversed.

Next, specific experimental examples conducted by the present inventors will be shown.

Using the beam splitter 13 with TS = 41%, T9 = 90%, R8 = 53%, Rp = 3%,
It is possible to increase the err rotation angle by approximately twice, and the S/N
I was able to get a good signal.

In addition, the degree of polarization of the laser light source is increased when it enters the magneto-optical recording material due to the difference in the reflectance of P waves and S waves.
There is no need to provide a polarizer in advance as in the prior art, and in other words, it becomes possible for the beam splitter itself to also serve as a polarizer.

(Effects of the Invention) As is clear from the description of the embodiments above, the magneto-optical reproducing apparatus according to the present invention reflects light from a laser light source by a beam splitter, and then irradiates the light onto a magneto-optical recording medium.
In a magneto-optical reproducing device that transmits light reflected by the recording medium to the beam splitter and reproduces recorded information based on the polarization component of the transmitted light, the beam splitter itself is provided with polarization characteristics. When the light from the Rede light source is reflected by the beam splitter and guided onto the recording medium, in addition to the beam splitting effect, it is possible to increase the degree of polarization of the SEA light, which eliminates the need for a polarizer, which was required in conventional devices. can be made unnecessary.

Furthermore, regarding the configuration in which the reflected light is reflected by the recording medium and transmitted through the beam splitter to reach the receiver, the Kerr rotation angle of the reflected light is amplified while passing through the beam splitter. Therefore, the reproduction sensitivity can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a conventional device, and FIG. 2 is a schematic diagram showing the configuration of the device of the present invention. 1... Laser diode 5... Recording medium 13... Beam splitter Patent applicant Nippon Musical Instruments Manufacturing Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] After light from a laser beam source is reflected by a beam splitter, it is irradiated onto a magneto-optical recording medium, the light reflected by the recording medium is transmitted to the beam splitter, and the transmitted light is In a magneto-optical reproducing device for reproducing recorded information based on polarization components: A magneto-optical reproducing device characterized in that the beam splitter itself is given a polarization characteristic (=l).