JPH0810854Y2 - Magneto-optical recording medium reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention relates to an optical system structure for obtaining a reproduction information signal and an automatic focus control signal in a magneto-optical recording / reproducing apparatus.

"Prior Art" As an example of a conventional optical system structure of this type, there is one as shown in FIG. In the drawings, 1 is a laser light source such as a laser diode for generating a laser beam, 2 is a collimator for collimating the light flux of the laser light source 1, and 3 is a collimator.
Is a half mirror for separating the forward and return light beams, 4
Is a magneto-optical disk for recording information by perpendicular magnetization, 5 is an objective lens for forming a light spot on the recording surface of the magneto-optical disk 4, and 6 is 1/2 for changing the direction of the polarization plane. Wave plate, 7 is an analyzer for detecting polarized light, 8A and 8
B is a lens, 9 is a cylindrical lens that generates astigmatism for obtaining an autofocus control (error) signal, and 10
A and 10B are detectors for detecting recorded information, and the detector 10B also detects a focus error signal. 11 and 12 are differential amplifiers.

Next, the operation will be described. The laser light generated by the laser light source 1 becomes a parallel light flux by the collimator 2, and the objective lens 4 through the half mirror 3 forms a light spot on the recording surface of the magneto-optical disk 4. On the other hand, the light flux reflected on the recording surface of the magneto-optical disk 4 is separated by the mirror 3 and is 45 ° with respect to the incident surface of the analyzer 7 by the half-wave plate 6.
The plane of polarization is rotated so that it becomes azimuth. Here, since the information signal recorded on the magneto-optical disk 4 is recorded in the form in which the magnetization directions are reversed in normal and reverse directions, the plane of polarization is rotated by a slight angle due to the Kerr effect, so that the passing light passing through the analyzer 7 is transmitted. And the reflected light is subject to fluctuations in light intensity. The intensity fluctuations of the light are converted into electric signals by the respective detectors 10A and 10B, and the difference signal between the two detectors 10A and 10B is generated by the differential amplifier 11 and becomes the reproduction information signal S.

On the other hand, the shape change of the light flux given astigmatism by the cylindrical lens 9 is converted into an electric signal by the detector 10B composed of a plurality of light receiving elements, and the difference signal is generated by the differential amplifier 12 to focus the light. Error signal Sf
Becomes

"Problems to be solved by the device" As described above, the conventional optical system structure of the magneto-optical recording / reproducing apparatus has a large number of parts and complicates the configuration, so that it cannot be downsized and the cost is high. was there.

The present invention has been made to solve the above-mentioned drawbacks, and provides an optical system structure of a magneto-optical recording / reproducing apparatus having a simple structure by consolidating the functional elements constituting the apparatus. The purpose is to do.

"Means for Solving Problems" The present invention provides means for solving the above-mentioned drawbacks.
It is configured as follows.

That is, in a magneto-optical reproducing device that reads a signal magneto-optically, a light source that emits light, a lens that converges the light from the light source, and a light that is reflected by a magnetic recording medium and that has passed through the lens are S-polarized and Optical means for separating into P-deflection and for imparting astigmatism to one of the separated S-deflection and P-deflection, wherein the optical means comprises:
A first surface that is inclined with respect to the incident light; and a second surface that further transmits the light that has passed through the first surface and guides it to the outside of the optical means.
Surface and a deflecting film applied to the first surface, the first surface being separated by the deflecting film.
One of the deflections is reflected and the other is passed, and the focus light is detected using the passing light.

In the above configuration, the light from the light source is S-polarized and P-polarized.
The polarized light is separated and passed through a means for imparting astigmatism to one of them, but the direction of deflection of the laser light source and the direction of the recording track are parallel or orthogonal to each other. The meridional surface and the incident surface of the point aberration generating analyzer may be oriented in a direction of approximately 45 ° with respect to the above-mentioned deflection and track directions.

That is, in FIG. 1 described later, 1 /
Although it is configured by arranging two wavelength plates, as shown in FIG. 2 described later, the half wavelength plate is omitted and the deflection direction of the laser light source and the track direction are astigmatism generating analyzers. By forming the incident surface at 45 ° with respect to the paper surface of Fig. 2, the deflection surface direction and the analyzer incident surface direction become 45 °, and the light intensity fluctuation noise becomes the same phase and the same amplitude, and the operation amplifier cancels it out. The Rukoto.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical system structure of a magneto-optical recording / reproducing apparatus according to the present invention.

In the above drawings, 21 is a laser light source such as a laser diode for generating a laser beam, 22 is a collimator for making the light flux of this laser light source 21 a parallel light flux, and 23 is a half for separating the forward and return light fluxes. A mirror, 24 is a magneto-optical disk for recording information by perpendicular magnetization, 25 is an objective lens for forming an intersection on the recording surface of the magneto-optical disk 24, and 26 is 1 for changing the direction of the polarization plane. / 2 wave plate, 27 is a lens.

28 is an astigmatism generation analyzer having an astigmatism generation function for obtaining an autofocus control (error) signal by an astigmatism effect and an analyzer function for detecting a magneto-optical signal,
In the drawing, a polarizing film is applied to one side of a double-sided parallel plate, and the P-polarized component is almost 10 as in the polarization beam splitter.
It transmits 0% and reflects almost 100% of the S-polarized component. 29A and 29B are detectors for detecting recorded information, and the detector 29B also detects a focus error signal. Reference numerals 30 and 31 are differential amplifiers.

Next, the operation of the above embodiment will be described.

The laser light generated by the laser light source 21 becomes a parallel light flux by the collimator 22, and the light spot is formed on the recording surface of the magneto-optical disk 24 by the objective lens 25 via the half mirror 23. Further, the light flux reflected on the recording surface of the magneto-optical disk 24 is separated by the mirror 23, and the polarization plane is rotated by the half-wave plate 26 so as to have a 45 ° azimuth with respect to the incident surface of the astigmatism generating analyzer 28. Receive. Here, since the information signal recorded on the magneto-optical disk 24 is recorded in a form in which the magnetization directions are forward / reverse inversion, the plane of polarization is rotated by a small angle due to the Kerr effect. The transmitted light (P-polarized component) and reflected light (S-polarized component) that pass through are subject to light intensity fluctuations, and the recording information signals corresponding to the direction of magnetization are output from the detectors 29A and 29B. The changes in the light intensities of the transmitted light and the reflected light are naturally opposite to each other, so the detector 29
The difference signal of the recording information signals output from A and 29B is applied to the differential amplifier 30 and becomes the reproduction information signal S.

On the other hand, the transmitted light that has passed through the astigmatism generation analyzer 28 is given astigmatism suitable for detection of focus error, and is output together with the recording information signal by the detector 29B, and this output is applied to the differential amplifier 31. The focus error signal Sf is generated.

It should be noted that the reproduction information signal S described above is generated by one detector 29A.
The detector 29B is not an indispensable element because the output from the same can be obtained in the same manner.

Other Examples In the above example, the half-wave plate 2 is placed in front of the lens 27.
Although 6 is arranged, the half-wave plate 26 can be omitted if configured as shown in FIG. That is, the polarization direction of the laser light source 1 indicated by the arrow E and the track direction indicated by the arrow T are both within the plane of the drawing, for example, and the incident surface of the astigmatism generation analyzer 28 is 45 ° with respect to the plane of the paper. By doing so, a good information reproduction signal S can be obtained without the half-wave plate 26, and a focus error signal Sf with less track crossing noise can be obtained.

This is because the polarization plane azimuth and the analyzer entrance plane azimuth are 45 °, so that the light intensity fluctuation noise has the same phase and the same amplitude, so the differential amplifier 30 differentially cancels it and the track is generated. The symmetry axis of the diffracted light pattern
This is because the track crossing noise is reduced because it coincides with one of the light receiving surface dividing lines of B.

 The differential amplifiers 30 and 31 are omitted in the drawing.

Further, in the above-mentioned embodiment, the double-sided parallel flat plate is used as the astigmatism generation analyzer 28, but other various shapes are conceivable, examples of which are shown in FIGS. 3 (a) and 3 (b).

First, (a) in the figure shows a polarizing film on one surface of the wedge substrate 32.
33 is a cube-shaped polarization beam splitter formed by joining base materials n ₁ ≠ n ₂ having different refractive indexes, and (b) in the figure has the same effect as the above embodiment. Play.

[Advantages of the Invention] As described above, the present invention is a magneto-optical reproducing apparatus for reading a signal magneto-optically, in which a light source that emits light, a lens that converges the light from the light source, and a reflection on a magnetic recording medium. Optical means that separates the light that has been transmitted through the lens into S-deflection and P-deflection, and that has astigmatism in either of the separated S-deflection and P-deflection,
The optical means comprises a first surface inclined with respect to incident light;
The second surface further includes a second surface that further transmits the light that has passed through the first surface and guides the light to the outside of the optical unit, and a deflection film formed on the first surface, the first surface including the deflection film. One of the S-polarized light and the P-polarized light separated by the film is reflected and the other is passed, and the focus light is detected using the passing light.

That is, since the single optical element 28 is configured to have the astigmatism generation function and the analyzer function, the entire optical head can be made compact and lightweight, and the number of parts and cost can be reduced. .

Also, in magneto-optical reproduction that uses weak light changes as signal information, the light amount loss due to the optical components in the middle has a great influence on the S / N of the signal, but by reducing the optical components as described above, It can contribute to the reduction of the light amount loss and therefore the improvement of the S / N.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical system structure of a magneto-optical recording / reproducing apparatus according to the present invention, FIG. 2 is a schematic configuration diagram of an optical system structure of another embodiment, and (a) and (b) of FIG. 4) are perspective views of different embodiments of the astigmatism generating analyzer used in the above optical system structure, and FIG. 4 is a schematic configuration diagram of the optical system structure of the conventional magneto-optical recording / reproducing apparatus. 21 ... Laser light source, 22 ... Collimator, 23 ... Half mirror, 24 ... Magneto-optical disk, 25 ... Objective lens, 26 ...
... 1/2 wave plate, 28 ... Astigmatism generating analyzer, 29A, 29B ...
… Detectors, 30, 31… Differential amplifiers.

Claims (1)

[Scope of utility model registration request] 1. A magneto-optical recording / reproducing apparatus for reading a signal magneto-optically, a light source for emitting light, a lens for converging light from the light source, and light reflected by a magnetic recording medium and passing through the lens. Is divided into S-deflection and P-deflection, and optical means for imparting astigmatism to either of the separated S-deflection and P-deflection is provided, and the optical means is inclined with respect to incident light. And the first surface
A second surface that further passes light that has passed through the first surface and guides the light to the outside of the optical means, and a deflection film provided on the first surface, and the first surface is separated by the deflection film. The S
A magneto-optical recording medium reproducing apparatus characterized in that one of the polarized light and the P-polarized light is reflected and the other is passed, and a focus error is detected using the passing light.