JPS6212942A - Photomagnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a recording in a photomagnetic recording medium with excellent S/N by disposing, between a polarizing beam splitter and a first laser beam source, a quarter wavelength plate for a second wavelength a filter means which transmits a laser beam of a first wavelength while reflecting that of the second wavelength, and a second wavelength plate in the order of polarizings. CONSTITUTION:Between the polarizing beam splitter 17 and the first collimator lens 12, the quarter wavelength plate 16 for 8,300Angstrom , the filter 15 that totally reflects the laser beam of 8,300Angstrom and totally transmits the laser beam of 7,800Angstrom , and the second wavelength plate 14 are disposed in the herein said order from the splitter-side. The laser beam from an R/P semiconductor laser 10 is made turn its plane of polarization by 90 deg. as it goes through the wavelength plate 14, the filter 15, and the quarter wavelength plate for 8,300Angstrom 16, so that it mainly includes P-polarization component. The wavelength plate 14 is inserted for this purpose. The beam splitter 17, the quarter wavelength plate for 8,300Angstrom 16, and the filter 15 are used for modifying the optical path of a deletion beam.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magneto-optical recording and reproducing device using the magneto-optic effect.

(b) Conventional technology Research has been progressing in the past on perpendicular magnetic recording and reproduction of information by applying magneto-optical effects such as the Faraday effect and the magnetic Kerr effect. Generally, Ga0o, GdFe is used as a recording medium.
, TbFe or the like is used. FIG. 2 is a diagram showing the principle of recording and erasing on a magneto-optical disk. In the case of recording, a semiconductor laser beam (2) 4 is irradiated onto a recording medium (1) whose entire surface has been magnetized in one direction in advance to locally raise the recording medium to around the Curie point, and the area irradiated with the laser beam is Recording is performed by applying a bias magnetic field (3) in the direction opposite to the direction in which the recording medium is magnetized to the area included in the recording medium, thereby creating a magnetized area in the opposite direction to the direction in which the recording medium is irradiated. On the other hand, in the case of erasing, if a bias magnetic field is applied in the opposite direction to that during recording, that is, in the direction of magnetization in advance, and laser light is continuously irradiated, the working area whose magnetization direction was reversed during recording will be reversed again to the original direction. In particular, the information has been erased.

Recording and erasing of magneto-optical disks is performed as described above, but when rewriting information that has already been recorded using a single laser beam, the direction of the bias magnetic field is different for recording and erasing, so the information that was previously recorded is After erasing -e(
must be recorded. Therefore, two beams, a recording/reproducing beam and an erasing beam, are prepared, and each beam is placed in an adjacent recording track, and the direction of the external magnetic field is switched for each predetermined torque. A method has been proposed that allows data to be re-recorded while being erased. (Refer to Japanese Unexamined Patent Publication No. 57-117106) → Problems to be Solved by the Invention And 1. In the present invention, the optical system in the above-mentioned prior art is further improved, and recording, reproducing, and erasing operations in an f magnetic recording and reproducing device are improved. The aim is to do this effectively.

) Means for solving the problem The reflectance for the S-polarized component and the P-polarized component is the ratio of the tool gradient reflection on the one hand (the first polarization component), and on the other hand (the first polarization component).
second polarization component), the reflectance is smaller (e.g. 3
Use a polarizing beam splitter set to a first laser light source having a first wavelength and primarily a first polarization component;

It is placed facing the magneto-optical recording medium with the polarizing beam splitter in between. and a second laser light source having a second wavelength and primarily having a first polarization component.

The polarizing beam splitter should be provided at a position where the incident light to the polarizing beam splitter is reflected toward the first laser beam side.

A second laser light source is provided between the polarizing beam splitter and the first laser light source.
A wavelength plate for a wavelength of , a filter means for transmitting a laser beam having a wavelength of vll and reflecting a laser beam having a second wavelength, and a second wavelength plate are arranged in this order from the polarizing beam splitter side.

Due to these functions, the laser beam emitted from the first laser light source is changed to mainly have the second polarization component when the laser beam is incident on the polarization beam splitter.

The reflected light from the magneto-optical recording medium is reflected once by this polarizing beam splitter and then supplied to an analyzer and a light receiving sensor.

One of the first laser light source and the second laser light source is used for recording/reproduction, and the other is used for erasing.

-) Effect When the laser light from the first laser light source enters the polarizing beam splitter, it is changed into a second polarized light component and passes through the polarizing beam splitter. father.

The Rade light from the second laser light source is once reflected by the polarizing beam splitter, then reflected by the filter means, and enters the polarizing beam splitter again. The plane is rotated and a second polarized component passes through the polarizing beam splitter.

On the other hand, when the plane of polarization of the reflected light from the first magneto-optical recording medium is rotated by the Kerr effect, it also includes the first polarization component. Since the polarizing beam splitter has a high reflectance for the first polarized light component, the apparent Kerr rotation angle of the light introduced into the analyzer increases, and the S/N of the reproduced signal improves.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

Figure $1 is a block diagram showing the optical system (optical head 6I).

In Figure 1, (101 is a recording/erasing (R/P) semiconductor, -4 (first laser light source), and its wavelength is 7
800A, and mainly has an S polarization component for a polarization beam splitter aη described later. (lz is the first collimator lens.

(Ill is a semiconductor laser (second laser light source) for erasing, and has a wavelength of 830OA. In contrast to the i+ beam splitter αη, which will be described later, it mainly has an S polarization component. This is the second collimator lens.

11? ) is a polarizing beam splitter, and 8 polarizing acids (
′! The film (17a) is formed so that the reflectance for the J11 polarized light component is 100% and the reflectance for the P polarized light component (!J2 polarized light component) is 30%. This polarizing beam splitter η improves the degree of linear polarization of the laser beam from the R/P semiconductor laser ELL, and also improves the apparent Kerr rotation angle of the reflected light from the disk (1), which is a magneto-optical recording medium. It has functions that increase

Polarizing beam splitter Qη and first collimator lens σ2
In between is a wavelength plate for the 8300A (lG, 83, a filter that completely transmits the light) and a second wavelength plate a4.

They are arranged in this order from the polarizing beam splitter side.

The laser light from the RZ P-phase semiconductor laser passes through this wavelength plate fi41. By passing through the filter α51, 830OA quarter-wave plate (16), the light planes 90i, (i'm) are rotated and have a P-polarized component as the king.

For this purpose, a wave plate! 141 has been inserted.

Reference numeral 1 denotes an objective lens, which focuses the first (7) beams on the disk.As will be described later, the focusing positions of the R/P beam and the erase beam are set to be different.

The light reflected from the disk (1) is reflected by the polarizing beam splitter αη, which is a wavelength plate that rotates the polarization plane of the laser beam by a predetermined angle. #2D is a dichroic mirror that transmits the 7-dimensional light, ■ is a polarizing beam splitter that serves as an analyzer, [231CI! 4) is the first one for signal reproduction. The second receiving sensor (this part can also be composed of a normal analyzer and one light receiving sensor), and the third receiving sensor for address reading (irradiated with 8300A laser light). .

The emitted π laser beam (8300λ
) mainly has an S-polarized component with respect to the polarizing beam splitter σD, so it is once reflected by the polarizing beam splitter aη toward the R/P semiconductor laser α0 side. Then, it passes through the wave plate α61 for 8300A, and the filter rl
It is totally reflected by S, passes through the wavelength plate again for 8300A, and enters the polarizing beam splitter 117). 85
00 AFIA 1/4 wave plate (passes through 11112 degrees, so the 8 polarized light components are rotated 90 degrees and become the P polarized light component. Therefore, the erase beam (8300A laser source) passes through the polarization beam splitter ση. The light passes through and is irradiated onto the disk (1).

On the other hand, the laser beam from the R/P semiconductor laser (101)
7800A) is equipped with a wave plate (141) and a filter (141) as described above.
By passing through the wavelength plate αe for Is and 81500A, the light is rotated from the daily polarized component to mainly have the P polarized component. Then, by passing through the polarizing beam splitter aη, the R/P beam (7800A laser beam) with an excellent degree of linear polarization is focused onto the disk (1).

A polarizing beam splitter (17), a quarter wavelength plate C161 for 8300A, and a filter (15) are used to change the optical path of the erase beam. Since it is configured like this,
The "beam splitter [equipped], etc." in the above-mentioned conventional technology is no longer needed.

Since the reflected light from disk (1) is a P-polarized component for both the 7800X laser beam and the 8300A laser beam,
It is reflected by the polarizing beam splitter with a predetermined reflectance. Then, the 7800A laser beam is reflected by the dichroic mirror Q11, and the analyzer a0. First light receiving sensor, second light receiving sensor (to), (Introduced in 23.8300X
The laser beam passes through the dichroic mirror (21) and is irradiated onto the third light receiving sensor @.

FIG. 3 is a plan view of the disk (1). (2) is the center hole of the disk (1), (3) is the magneto-optical recording part where the magneto-optical magnetization film is formed, and (4) is the address area where the address of the recording track is recorded in the form of uneven bits. It is.

A spike-shaped guide groove is formed on the disk (1), and this becomes a recording track. That is, the fourth
As shown in the cross-sectional view of Figure (a), a transparent plastic substrate made of polycarbonate or acrylic (PMMA) (with a spiral guide groove formed) (5) on which a guide groove (5a) is formed is vertically disposed. Sputtering the magnetized film (6),
Created by vapor deposition. Furthermore, a fatty electrolyte film (7) is formed for the purpose of protection and the like. The perpendicular magnetization film (6) has
GdT, an amorphous alloy of rare earth metals and transition metals
bFe and T'bFe□o are used.

And in the address area (4) shown in FIG.

As shown in FIG. 4-1, address information indicating the address of the recording track (5a) continuous to the guide groove (5a) is formed simultaneously with the guide groove (5&). This address information is recorded in the form of uneven bits (8) as described above, and can be read out in the same manner as a compact disc. The relationship between the erasing beam spot c111 and the recording/reproducing beam spot C'13 on the disk is shown in FIG. In other words, the erasure beam spot C
3D is arranged so that it precedes the recording/reproducing beam spot C4a by one track. Furthermore, the wavelength of the erase beam (asooi) is the same as the wavelength of the R/P beam (780o
Since the objective lens (19) and the first and second collimator lenses σ21 (131) have the same numerical aperture (NA), the erased beam spot Q
l) is larger than the R/P beam spot. As a result, erasing by the erasing beam is ensured, and the R/p beam spot c3 becomes smaller, thereby improving the recording density.

In addition, the collimator lens (121 (131 aperture ratio (NA)
) t” for R/P (set larger than 13 for erasing a3 or a combination of the above (combination of aperture ratio and wavelength)
Therefore, a method of making the erasing beam spot c111 larger than the Fl/P beam spot Oa can also be considered.

Next, a description will be given of how the erasing operation and the recording operation are performed simultaneously (this is also explained in Japanese Patent Laid-Open No. 57-t17t06). During recording, the RZP semiconductor laser (11
is intensity-modulated according to the information signal (digital signal) to be recorded, but the erasing semiconductor laser a1J is driven with a constant intensity.

When the information from addresses n to m is rewritten (see Figure 5), the outputs of the RZ P semiconductor laser α1 and the erasing semiconductor laser ttn are set to a low output state, and the disk (1 ) without damaging the information recorded on the optical head l! The IG is transported to a predetermined location. When address n is detected by the erase beam (51), the direction of the bias magnetic field corresponding to this address (predetermined 1, for example, the direction shown in FIG. 1, 11))
is set by the bias magnetic field applying means (53), and the output of the erasing semiconductor radar QD is increased to a predetermined value. Then, the track at address n is aligned in the direction of magnetization in the (A1 direction) by the erase beam and the bias magnetic field.

At this time, nothing is done by the R/P beam (52) tracing address n-1.

Next, when the erase beam (51) detects address n+1, the direction of the bias magnetic field is reversed (for example (toward 1), the output of the R/P semiconductor laser αQ is increased, and the output of the R/P semiconductor laser αQ is increased. The conductor αQ is modulated by the information to be recorded.Therefore, the track at address n+1 is aligned with the direction of magnetization in the (b) direction, and the track at address n is recorded with a bias magnetic field in the (c7) direction. That will happen.

When the erase beam detects the next address n-1-2, the bias magnetic field is reversed again, and the track at address n+2 is magnetized in the k) direction, and the track at address n+1 is recorded under the bias magnetic field in the 6S direction. be done. Thereafter, the same operation is repeated.

When the erase beam detects address m+1, the bias magnetic field is reversed, but the output of the erase semiconductor laser (111) is lowered so that the track at address m+1 is not erased. Information is then recorded in the track at address m. Next, when the erase beam detects address m+21, R/
The output of the P-phase semiconductor sensor αα decreases, and the recording operation ends.

The above operation is performed on the spirally formed track tR/
This is accomplished by performing tracking control using a P beam and moving the optical head using known means.

During reproduction, only the R/P semiconductor laser (1G+) is driven at low output in the reproduction state.Then, the P-polarized laser beam that has passed through the polarization beam splitter αD is sent to the disk (1).
As a result, the plane of polarization is rotated according to the direction of magnetization of the disk (1), so that it has an S-polarized component. Since the P polarized light component is reflected by the polarizing beam splitter σ (because the reflectance is 30%), this is equivalent to an increase in the rotation angle of the polarization plane.

The light reflected by the polarizing beam splitter 17) is reflected by a long He plate■
The plane of polarization is rotated by a predetermined angle, and the diklopug mirror c! It is totally reflected at D and is incident on the second polarizing beam splitter αa which serves as an analyzer.

The second polarization beam splitter α separates the light into a P polarization component and an S polarization component, and irradiates each light receiving sensor area 04.

A differential amplifier (c) calculates the difference in the output of each light receiving sensor [with] Q4.
When derived from , the reproduction output of the magneto-optical disk is obtained at the terminal (to). When playing a compact disc, a non-differential amplifier (c) is used.

Note that address detection is performed using an erase beam,
A change in the output of the third light receiving sensor is applied to a control circuit (not shown) via an amplifier Q7). This control circuit controls the above operations (operation of the bias magnetic field applying means (53), operation of each semiconductor laser, etc.).

In the optical head (5(l), semiconductor lasers αC and aυ
Replace the wave plate (lG, filter means tt51.
Even if a second wave plate (including modification of 41) is used, it can be used in the same way.

Furthermore, in the conventional example (Japanese Patent Application Laid-open No. 117106/1983), the polarity of the reproduction signal is switched for each track during reproduction, but in this embodiment, the signal recorded and reproduced is OD (Compact Disk) 7. -j- Not necessary if matte.

(g) Effects of the Invention As described above, according to the present invention, it is possible to reproduce recordings on a magneto-optical recording medium with excellent S/N, and it is possible to use a common laser beam for recording/reproducing and erasing laser beam. This is effective because it can be realized in an optical head.

[Brief explanation of drawings]

Figure 1 is a block diagram of the embodiment. Figure 32 is a diagram explaining the principle.
FIG. 3 and FIG. 4 are diagrams showing magneto-optical disks. FIG. 5 is an explanatory diagram of the operation. αG...Semiconductor laser for R/P, nil...Semiconductor for erasure. Laser, (141...second wavelength plate, a!9...filter means, ue...% wavelength plate, αD...polarized beam splitter, αto...analyzer (second polarized beam splitter) Ivy), CI!11...GuiGrog Mirror, R24)...Light receiving sensor.

Claims (1)

[Claims] (1) A polarizing beam splitter in which the reflectance for the S-polarized light component and the P-polarized light component is set smaller for the other second polarized light component than for the first polarized light component, and this polarized beam splitter is sandwiched. a first laser light source, which is provided at a position facing the magneto-optical recording medium, has a first wavelength and mainly has the first polarization component; and a first laser light source has a second wavelength and mainly has the first polarization component; and a second laser light source provided at a position where light incident on the polarizing beam splitter is reflected toward the first laser light source, the polarizing beam splitter and the first laser light source A quarter wavelength plate for the second wavelength, a filter means for transmitting the laser light of the first wavelength and reflecting the laser light of the second wavelength, and a second wavelength plate are provided between the filter means. , are arranged in this order from the polarizing beam splitter side, and the reflected light from the magneto-optical recording medium is reflected by the polarizing beam splitter and then applied to an analyzer for signal reproduction and a light receiving sensor. .