JPS63181144A - Magneto-optical head - Google Patents

Abstract

PURPOSE:To set a polarized separation angle largely by constituting a detection means by a polarized beam splitter, 1st and 2nd 1/4 wavelength plate and 1st and 2nd mirrors so as to provide polarized light separation function. CONSTITUTION:A polarized light beam splitter 15 has an action to separate incident light into the transmission light of P polarized lights 20, 22 and the reflected light of S polarized lights 16, 26. In making linearly polarized light incident in 1/4 wavelength plates 17, 23 and a mirror, the radiated light is circularly polarized light, the circularly polarized light is reflected in the mirror and made again incident in the 1/4 wavelength plates 17, 23, then the polarized direction is converted into the linearly polarized light whose direction is perpendicular to the original linearly polarized light. In combining the polarized beam splitter, the two 1/4 wavelength plates and two mirrors, the detecting means having the polarized light separating function like a Wollaston prism is obtained. In selecting the tilt of the two mirrors, since the polarized separation angle is selected optionally, the polarized separation angle is selected largely in comparison with a Wollaston prism.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magneto-optical head, and more particularly to a magneto-optical head that detects reproduction data using a differential reproduction method.

[Conventional technology]

Magneto-optical disk memory is about to be put into practical use as a large-capacity, high-density memory that allows information to be rewritten, but magneto-optical heads are less sensitive to reflections and transmission from the recording medium than normal optical heads for original disks. Improving the CN ratio is the most important issue because it is necessary to detect minute changes in the polarization state of the incoming light (Kerr effect, Faraday effect).
If there is a variation in the amount of reflected light on the surface of the recording medium, a sufficient CN ratio cannot be obtained with the direct reproduction method using a single analyzer as a detection means.

Conventionally, CN caused by such fluctuations in the intensity of the reproduced signal
A differential regeneration method is used to prevent ratio deterioration.

In the differential regeneration method, for example, as described in Japanese Patent Application Laid-Open No. 57-44241, a Wollaston prism is used as an analyzer to separate light into two beams with mutually orthogonal polarization planes, and the differential output is A method of reproducing a signal is known.

Also known is a method of using a polarizing beam splitter as an analyzer, as described in Japanese Patent Application Laid-Open No. 57-169947. A configuration using a polarizing beam splitter separates transmitted light and reflected light, but because the separation angle is very large, for example 90 degrees, two light receiving elements are required to detect each light. and T. In contrast, in the configuration used in the Wollaston prism, the polarization separation angle is relatively small; therefore, it is sufficient to use one light receiving element including two light receiving regions, which simplifies the head.

[One point while the invention is trying to solve the problem]

However, the polarization separation angle of the Wollaston prism is, for example, 1
Since it is quite small at 0 to 20 mrad, the
In this case, a signal cross-F-reflection occurs, and the CN using the differential regeneration method
In addition, in the case of a configuration in which a single light-receiving element detects a focus difference signal and a tracking error signal in addition to a reproduction signal, a light-receiving area for this purpose is added. Since the light-receiving area becomes large, the two light-receiving areas for reproduction signals cannot be brought very close to each other.

Moreover, in order to prevent these problems, the distance between the Wollaston prism and the light-receiving element becomes long, and the head becomes larger.

An object of the present invention is to provide a magneto-optical head that has the same polarization separation function as a Wollaston prism and can set a larger polarization separation angle than the Wollaston prism.

[Means for solving problems]

In order to achieve the above object, the present invention includes a linearly polarized light source, an optical means for guiding a light beam emitted from the linearly polarized light source onto the information recording surface of a magneto-optical information recording medium, and In a magneto-optical head comprising a separating means for separating a reflected and transmitted light flux T from the optical means, a detection means for detecting the separated light flux, and a detection means for detecting the light flux, the detection means is a polarizing heam splitter, first and second quarter-wave plates, and a first
and a second mirror, and the detection means includes a first light-receiving area that receives the first light beam polarized and separated by the detection means, and a second light-receiving area that receives the second light beam. and a light receiving area, and the two light receiving areas are integrally formed on substantially the same plane.

[Effect]

The polarizing beam splitter has the function of separating incident light into P-polarized transmitted light and S-polarized reflected light. Also-
Wave plates and mirrors are such that when linearly polarized light enters the 1/4 wavelength plate, the output light becomes circularly polarized, and when the circularly polarized light is reflected by the mirror and enters the 1/4 wavelength plate again, the output light becomes the original linearly polarized light. On the other hand, it has the effect of converting the light into linearly polarized light whose polarization direction is perpendicular.

Due to these effects, if we combine this polarizing beam split, two quarter-wave plates, and two mirrors, we get
It is possible to obtain a detection means having a polarization separation function in the same way as a Wollaston prism.

Furthermore, by setting the inclinations of the two mirrors, the polarization separation angle can be set arbitrarily, so the polarization separation angle can be set larger than in the Wollaston prism.

〔Example〕

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

FIG. 1 is a side view showing a first embodiment of the magneto-optical head according to the present invention. In FIG. 1, scattered light 2 emitted from a semiconductor laser, which is a linearly polarized light source, is converted into parallel light 4 by a frimate lens 3. After passing through the composite polarizing prism 5, the parallel light 4 is focused by an objective lens B, and is irradiated onto an information track 8 on an information recording surface of a disk 7, which is a magneto-optical information recording medium. The reflected light 9 from the disk 7 is converted into parallel light 1 again by the objective lens 6.
0 and reflected by the polarizing film 5& of the composite polarizing prism 5. This parallel light 10 enters a convex lens 12 via a prism 11 and becomes a convergent light 13.

This convergent light 13 enters a polarizing beam splitter 15 via a one-wavelength plate 14.

FIG. 2 is an enlarged view of the polarizing beam splitter 15 of FIG. The light 16 transmitted through the polarizing film 15a of the polarizing beam splitter 5 becomes P-polarized light (linearly polarized light parallel to the plane of the paper). The P-polarized light 16 passes through the quarter-wave plate 17 and becomes circularly polarized light 1.
8 and enters the reflection M19. The circularly polarized light 18 reflected by the reflective film 19 passes through the 1/4 wavelength plate 17 again.
This time, it becomes S-polarized light (linearly polarized light perpendicular to the plane of the paper) 20. S
The polarized light 20 is completely reflected by the polarizing film 15a, and the light receiving element 2
The light is incident on the region 21a of No. 1.

On the other hand, out of the convergent light 13, light 22 reflected by the polarizing film 15a
becomes S-polarized light. The S-polarized light 22 passes through the quarter-wave plate 23 to become circularly polarized light 24 and enters the reflective film 25 . The circularly polarized light 24 reflected by the opposite film 25 passes through the one-wavelength plate 23 again and becomes P-polarized light 26 this time. The P-polarized light 26 is completely transmitted through the polarizing film 15at and passes through the region 21b of the light receiving element 21.
incident on . Output signals 27a, 2 of regions 21a, 21b
7b is input to a differential amplifier 28 to obtain a magneto-optical reproduction signal 29.

This polarizing beam splitter 15, 1/4 wavelength plate 1 Otsu 25
The optical system composed of the reflecting plates 19 and 25 has a polarization separation function in the same way as the Wollaston prism. Furthermore, in order to set the polarization separation angle θ, it is sufficient to set the inclination angle of the reflective film 25 to a certain value, for example, so that the polarization separation angle can be arbitrarily set.

Next, FIG. 6 is a side view showing a second embodiment of the magneto-optical head according to the present invention. In Fig. 5, parallel light 10
is the same as the first embodiment until it is reflected by the polarizing film 5a of the composite polarizing prism 5, and the same reference numerals as those shown in FIG. 1 indicate optical elements having the same function. This parallel light 10 enters a polarizing beam splitter 30 via a prism 11 and a −H wavelength plate 14 .

FIG. 4 is an enlarged view of the polarizing beam splitter 30 of FIG. The light 51 transmitted through the polarizing film 30a of the polarizing beam splitter 30 becomes P-polarized light and enters the region 21a of the light receiving element 21 via the convex lens 12. -10,000 parallel light 10
Of the light, the light source 52 reflected by the polarizing film 30a becomes S-polarized light.

The S-polarized light 32 passes through the quarter-wave plate 33 and becomes circularly polarized light 64.
The light then enters the reflective film 35. The circularly polarized light 34 reflected by the reflective film 35 passes through the quarter-wave plate 33 again, and this time becomes P-polarized light 36.

The P-polarized light 36 completely passes through the polarizing film 50a, passes through the quarter-wave plate 37, becomes circularly polarized light 38, and enters the reflective film 39. The circularly polarized light 38 reflected by the reflective film 39 is again 1/
The light passes through the four-wavelength plate 37 and becomes S-polarized light 40. S
The polarized light 40 is completely reflected by the polarizing film 50a, and is reflected by the convex lens 12.
The light enters the region 21b of the light receiving element 21 through the light receiving element 21. The output signals 27a and 27b of the regions 21&, 21b are inputted to a differential amplifier 28 to obtain a magneto-optical reproduction signal 29.

This polarizing beam splitter 30, 1/4 wavelength plate 33.3
The optical system composed of the 7° reflective films 35 and 39 has a polarization separation function like the Wollaston prism.

In addition, in order to set the deflection separation angle to θ, for example, the reflection film 3
Since it is sufficient to set the tilt angle of 9 to 7, the polarization separation angle can be set arbitrarily.

In addition, in the first and second embodiments, the polarizing beam splitter 15.30 and the reflective film 19.25.35.39
1/4 wavelength plates 17, 25. Although the configuration is such that the two parts are joined together and integrated, the present invention is not limited to this.

For example, as shown in FIG.
On the other hand, the quarter-wave plate 43 on which the reflective film 42 is formed and the quarter-wave plate 45 on which the reflective film 44 is formed may be placed apart from each other without being joined. In this case, 1/4 wavelength plate 43.45
By setting the inclination angle of , the polarization separation angle can be freely set.

Further, as shown in FIG. 6, a quarter-wave plate 4647 is bonded to the polarized beam beam mirror 45 to form a mirror 4B.

aq'f: 11 They may be placed apart without being aligned. In this case, the polarization separation angle can be set arbitrarily by setting the inclination angles of the mirrors 48 and 49. Figures 5 and 6
The illustrated polarizing beam splitters 41, 45 do not need to have each facet inclined.

Note that the composite polarizing prism 5 used in FIGS. 1 and 3
The parallel light 4Ti: is used as an optical means for shaping the beam and guiding it to the disk 7, and a separating means for separating the reflected light beam from the disk 7 from the optical means, but the present invention is not limited to this. Needless to say, many variations are possible. Further, the prism 11 and the convex lens 12 are provided for detecting focus errors and tracking errors, and have no direct relation to the essence of the present invention. Further, the quarter wavelength plate 14 is provided for rotationally adjusting the direction of polarization incident on the polarizing beam splitter 530.
5. If the configuration is such that the 50 is rotated and adjusted, this engineering wave plate 1
4 can be omitted.

〔Effect of the invention〕

As explained above, in the magneto-optical head according to the present invention, the detection means T, that is, the analyzer includes a polarization beam splitter, first and second single-wavelength plates, and first and second single-wavelength plates.
It has a polarization separation function like a Wollaston prism.

Further, by setting the inclination angle T of the first and second mirrors, the polarization separation angle can be arbitrarily set, so the polarization separation angle can be set larger than that of the Wollaston prism. This makes it possible to arrange the two light-receiving regions on the light-receiving element in sufficient layers, and there is an effect that signal crosstalk does not occur and the CN ratio by the differential regeneration method is improved.

Furthermore, since the distance between the detection means and the light receiving element can be shortened, the head can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a first embodiment of the present invention. FIG. 2 is an enlarged view of the polarizing beam splitter 15 in FIG. 1. FIG. 3 is a side view showing a second embodiment of the present invention. , FIG. 4 is an enlarged view of the polarizing beam splitter 30 of FIG. 3, and FIGS. 5 and 6 are enlarged views showing modified examples of the polarizing beam splitter of the present invention. -15...Polarizing beam splitter, j5a...Polarizing film, 17.23...i
Wave plate, 19.25...Reflection film, 16.
26...S polarized light, 20.22...P polarized light,
21... Light receiving element, 21a, 21b...
Light receiving area. Tsumugi 1st 30th plot 40 Tsumugi 5 z 6th 圀

Claims (1)

[Claims] 1. A linearly polarized light source, an optical means for guiding the light beam emitted from the linearly polarized light source onto a magneto-optical information recording medium or an information recording surface, and a reflected or transmitted light beam from the information recording surface. A magneto-optical head comprising a separating means for separating a beam from the optical means, a detecting means for detecting the separated beam, and a detecting means for detecting the beam. and a second 1/4 wavelength plate, and first and second mirrors having arbitrary inclination angles with respect to the polarizing film of the polarizing beam splitter so that the polarization separation angle can be set arbitrarily, and , the detection means includes a first light-receiving area that receives the first light beam polarized and separated by the detection means, and a second light-receiving area that receives the second light beam, and the two light-receiving areas 1. A magneto-optical head characterized in that: are integrally formed on substantially the same plane. 2. The first quarter-wave plate and the first mirror are arranged at an angle of 45° with respect to the polarizing film of the polarizing beam splitter, and the second quarter-wave plate and the first mirror 2. The magneto-optical head according to claim 1, wherein the second mirror is arranged at an angle of more than 45° with respect to the polarizing film of the polarizing beam splitter.