JPS598151A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform reproduction with a high S/N ratio, by extending the space for interaction between a laser beam and magnetic recording to rotate a plane of polarization sufficiently. CONSTITUTION:A beam 31 which a laser 30 generates becomes linearly polarized light by a polarizing plate 19 and is flowed along a magnetic recording track 3 and is inputted to a photoelectric converter 21 through an approximately orthogonal polarizing plate 18. Since the plane of polarization is rotated by magnetic recording, a reproduced output is obtained from the converter 21. Since the rotation angle of the plane of polarization due to this Faraday effect is proportional to the length of the optical path where the magnetic field is changed, the rotation face is enlarged to improve the S/N ratio when a long recording track is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording/reproducing device that records a magnetic recording medium by rotating the plane of polarization of a laser beam.

A method of performing high-density recording by locally increasing the temperature of a magnetic medium using a laser is being developed.

In this reproduction, a laser beam is applied to the recording medium and the rotation of the polarization plane of the laser beam due to recording magnetization is detected, but the rotation angle is 20' and the grain size is 87N, which is not good. It is characterized by expanding the space for interaction and performing reproduction with good S/N by sufficiently rotating the plane of polarization.

FIG. 1 shows magnetic recording traces according to the present invention.

1 is a magnetic medium, on which magnetic recording is performed in a relatively wide and uniform manner, for example from the top to the bottom of 1, like a song. Such recording is performed using a wide magnetic head, but in order to achieve high density recording, a laser beam and a signal coil with a rectangular cross section may be used. A laser method for obtaining such a beam cross section will be described below.

FIG. 2 shows a case where the recording medium is tilted with respect to the laser beam 11 to obtain a beam with an effective elliptical spot.

With respect to the beam 11 emitted by the laser 10, the magnetic medium 1
When the laser beam is tilted by 1, an elliptical spot as shown by 13 is generated on the surface 1, and its major axis is D.
/sin θ, and the major axis can be arbitrarily increased by decreasing θ. Along with this, the laser output is also increased.

In FIG. 3, a columnar lens 15 is used, and in this case, a beam with an elliptical cross section is naturally obtained. These means are as described in Japanese Patent Application No. 18583 of 1982 issued by the inventor. In the present invention, laser beam reproduction is performed from a wide magnetic recording trace recorded by such a method. Of course,
A wide recording trace can be obtained by rapidly deflecting a dotted laser beam by some method, but this is difficult because reproduction is performed simultaneously as described below.

FIG. 4(b) shows a reproduction device according to the invention.

(a) is a front view, and (1)) is a side view. A beam 31 generated by the laser 30 is first converted into linearly polarized light by a polarizing plate 19, flows along the magnetic recording trace 3, and then enters the photoelectric conversion element 21 through the polarizing plate 18, which is oriented approximately orthogonally. Since the plane of polarization is rotated by optical recording, a reproduced output is obtained from 21. The angle of rotation of the plane of polarization due to the Faraday effect is proportional to the optical path length, which is replaced by the magnetic field.
When a long recording trace is used as in the present invention, the rotating surface can be enlarged and the S/N ratio can be improved.

Furthermore, as shown in figure (b), when an optical glass 33 is brought into contact with a medium and a laser beam is passed through it, the speed of light decreases inside the glass body, so it is exposed to a magnetic field for a sufficiently long time, and the plane of polarization changes. The rotation angle increases.

Even if the part 33 through which the beam passes is an optical fiber, and only the part other than the polarizing part is used between the laser and the optical element, a mode-dependent fiber is used as necessary to make the plane of polarization accurate.

Reference numeral 34 is a thin film made of garnet or GdFe, which is used to transfer information on a magnetic medium as is well known, and which has a smooth surface to reduce bass sounds. Of course, a magnetic medium covered with such a thin film may also be used.

FIG. 5 shows a reproduction device according to the invention.

The beam 31 of the laser 30 was recorded (using the Kerr effect, in which the plane of polarization is rotated by reflection on the surface of the R-type surface 200, together with the Faraday effect. 43 is a glass body with the thin film described above on the lower surface.

Polarizing plate 17. 18, again, the amplitude changes depending on the recording magnetization in a nearly orthogonal relationship. The surface of the glass body has a large area where the magnetic recording medium interacts with the light beam, which prevents reflection with a film that is 1/4 of the laser wavelength, so the S/N ratio is higher than before. Although it is not necessary, if the glass body 43 is provided, the rotation angle will be increased as in the case of FIG. 4.

FIG. 6 also shows a reproduction device according to the invention. Laser beam 1
The light 1 passes through the diplexer 27, is opposed by the magnetic plane, passes through the polarizing light 17, is reflected by the mirror 36, is reflected again by the 200 plane, is reflected by 27, and enters the light receiving element 21. If the rotation angle of the analyzer 17 is set to 45 degrees, the analyzer 17 will rotate approximately 90 times in a round trip, and the other analyzer 18 will produce a modulated output.

FIG. 7 shows a known method for reducing playback noise. The beam entering the photoelectric conversion element 21 is
The beam is split into a beam 31'' by the polarizing plate 18' and the conversion element 21' to produce an output, and these two outputs are outputted by the differential amplifier 52. This causes a difference of about 40 dB.
However, this method can be applied to any of the photoelectric conversion optical paths mentioned above.

FIGS. 8(a) and 8(b) show another method of obtaining a light beam with a rectangular cross section in front and end views, respectively. laser 10
The output of is converted into a cross section as shown at 56 by a toroidal conversion optical fiber 55.

9(a) and 9(b) show the optical system shown in FIG. 8 applied to a magneto-optical recording head, viewed from the side F+-, from the front,
Shown in bottom view. The flat portion of the optical fiber directly constitutes the gap portion of the magnetic head 63. The circular cross section of the fiber may pass through the head arc hole 62 as shown at 1°C. During recording, the head 63 is irradiated with the laser 10 while applying a signal.

An optical system as shown in FIG. 9 may also be used during reproduction. 1st
When reproduction is performed using a combination head as shown in Fig. 0, the low frequency is obtained from the magnetic head and the squid is obtained from the laser beam as described above, so magnetization can be improved by combining the two.

Since the optical recording and reproducing apparatus according to the present invention can be applied to magnetic recording having a width, it can be applied with a lower recording refocusing rate of 87N than that of a normal VTR.

The present invention is not limited to the above specific example, and can be modified in various ways.

[Brief explanation of drawings]

FIG. 1 shows magnetic recording according to the invention. Figure 2 and 3rd grade
The figure shows an optical circuit χ used in the present invention. FIG. 4 shows an optical recording 1Q recording apparatus according to the present invention, in which a) is a front view, and (1) is a side view. Figure 5.6 shows an optical recording and reproducing device according to the invention. FIG. 7 shows 11 raw circuits that can be used in the present invention. FIG. 8 shows a side view (a) and an end view (b) of an optical system that can be used in the invention. FIG. 9 is a front view (a) of a composite magnetic head that can be used in the present invention.
) and bottom view (b).

Claims (1)

[Claims] A means for producing a wide recording trace in a direction substantially perpendicular to the direction of travel of the medium on a magnetic recording medium, a means for applying a light beam substantially across the recording trace in the width direction, and by the action of a magnetic field generated by the recording trace. 1. An optical recording and reproducing apparatus comprising: a polarization plane rotating means for rotating a polarization plane of a light beam; and a means for detecting the rotation of the polarization plane by the polarization plane rotation means and reproducing a signal.