JPS59140655A - Photomagnetic recording type writing and reading device - Google Patents

Abstract

PURPOSE:To use both writing and reading systems in common with each other and at the same time to attain the additional writing by using two lasers having the same polarizing direction and forming the same beam form and the same optical path with an optical means (polarized beam splitter) which secures the coincidence among optical paths of output beams and a 1/2 wavelength plate which secures the coincidence among beam shapes. CONSTITUTION:A 1/2 wavelength 33 is inserted only to an optical system of one side, and the polarizing direction is set vertical. At the same time, a polarized beam splitter 34 is used for connection of the plate 33 to obtain the same optical path and the same beam form. At the time of writing, only the semiconductor laser 31 of one side is oscillated intensively so that the temperature at the position of a beam spot on a disk 7 is set higher than the Curie point. Then the information is written on the disk 7. While at the time of reading, only the semiconductor laser 11 of the other side is oscillated with reduced intensity to read the information written on the disk 7. Then both lasers 11 and 31 are simultaneously oscillated at the time of additional writing. Then the additional writing is carried out with the beam of the writing laser 31 while the tracking control is performed with the beam of the reading laser 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a writing/reading device for an information recording/reproducing apparatus using a magneto-optical disk memory of a magneto-optical recording type.

Prior Art A so-called magneto-optical disk memory generally has a disc-shaped base made of glass or plastic.

It consists of a perpendicularly magnetized film, usually e microns thick, fixed on the substrate. The perpendicularly magnetized film is made of a magnetic material such as an amorphous alloy, and has the property of being magnetized in a direction perpendicular to the film surface.

To record information on such a magneto-optical disk memory, first, the magnetization direction of the perpendicular magnetization film of the magneto-optical disk memory is aligned in one direction, and then a laser beam beam (digitally modulated by an information signal) is used.
irradiates the perpendicularly magnetized film to raise the temperature of the perpendicularly magnetized film to more than one Curie point. Then, the magnetization direction of the portion irradiated by the laser beam spot is reversed due to the influence of the surrounding magnetic field, and a logic "°1°" (or "0") is recorded.

In addition, in order to read the information recorded on the magneto-optical disk memory in this way, the perpendicularly magnetized film is irradiated with a linearly polarized reading beam spot, and the reflected beam is polarized due to the difference in the magnetizing force direction of the perpendicularly magnetized film. It utilizes the magneto-optical Kerr effect in which the surface rotates.

In the conventional apparatus for recording and reading information using a magneto-optical disk memory as described above, separate optical systems are used for writing and reading. Because the Kerr rotation angle (rotation angle of polarized light due to the Kerr effect) of magneto-optical disk memory is very small, the tracking control required for the reading optical system uses the far-field method used for optical disks. However, since the so-called three-beam method is used for tracking, the writing optical system and the reading optical system cannot be made the same.

FIG. 1 shows an example of an optical system of such a conventional magneto-optical recording type writing/reading device. First, to explain the writing optical system (recording system), a laser beam emitted from a self-modulating semiconductor laser 1 is collimated (converted into a parallel beam bundle) by a collimator lens 2, and a polarizing beam splitter 3
incident on .

In this polarizing beam splitter 3, P(Parallel
) polarization is transmitted, and 5 (Senkrecht) polarization is reflected. Now, assuming that the polarization direction of the semiconductor laser 1 is placed so that it is aligned with the plane of the paper, the laser beam is transmitted through the laser beam splitter 3 and a quarter-wave plate (l/4
The circularly polarized light enters the optical wave plate) 4 and becomes circularly polarized light.The circularly polarized light is further reflected 90' by the reflecting mirror 5, passes through the objective lens 6, and is imaged on the surface of the disk (magneto-optical disk memory) 7. The magnetization direction of the perpendicular magnetization film fixed on the surface is reversed.

The beam reflected by the surface of the disk 7 passes through the objective lens 8 and the reflection mirror 5 again, and is made S-polarized by the 1/4 wavelength plate, so it is reflected by the polarization beam splitter 3 and enters the detector. do. The light incident on the detector 8 is photoelectrically converted.

It is used as a servo signal (autofocus signal) to always control the focus of the objective lens 6 to a normal position. At this time, the disk 7 is rotated by a drive motor 10 via a spindle 9 at a predetermined speed.

Next, the reading optical system (reproduction system) will be explained. The laser beam emitted from the other semiconductor laser 11 is collimated (converted into a parallel beam) by the collimator lens 12 and enters the polarizing plate 13. The polarizing plate 13 improves linear polarization, and the grating (diffraction grating) 14 splits the light beam into three. Each light beam passes through a half mirror 15, is reflected by a tracking mirror 1B, and is reflected by an objective lens 17 onto the disk 7 surface. is imaged.

The polarization direction of the reflected beam of the light beam hitting the disk 7 is rotated by the Kerr effect described above, and the light beam hits the objective lens 1 again.
7 to the tracking mirror 16 and the half mirror.
15 and is split into two beams by a half mirror 18. One beam passes through a polarizing plate 19 and enters one detector 20, and the other beam passes through a polarizing plate 21 and enters another detector 22. The deflection plates 18 and 21 have their deflection directions shifted from each other by a predetermined angle. Further, trunking and autofocus of the reading system are performed by a known system. The signals photoelectrically converted by the detectors 20 and 22 are sent out as read signals by the comparator 23.

As described above, the conventional apparatus has a separate writing optical system and reading optical system, which makes the optical system complicated, and it has the disadvantage that additional writing cannot be performed because tracking control is only possible during writing.

OBJECTIVES The objective of the present invention is therefore to eliminate the above-mentioned drawbacks and to: 1
It is an object of the present invention to provide a magneto-optical recording type write-read device which uses a /2 wavelength plate, has a relatively simple optical system configuration, and enables additional writing.

Example □ Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an example of the configuration of the writing/reading device of the present invention, where 31 is a writing semiconductor laser whose polarization direction is the same as that of the reading semiconductor laser 11, and 32 is a beam from the semiconductor laser 31. A collimator lens 33 is a 1/2 wavelength plate (1/2 wavelength plate) that changes the polarization direction of the linearly polarized laser beam that has passed through the collimator lens 32 by 80 degrees to make it S-polarized. ), 34
is an optical means that reflects the beam that has passed through the 1.72 wavelength plate 33, such as a polarizing beam splitter.
15. Therefore, the laser beam sent out from the semiconductor laser 31 is reflected by the polarizing beam splitter 34, passes through half mirrors 15 to 17, and is directed to the disk 7.
imaged on the surface of Further, the laser beam sent out from the other reading semiconductor laser 11 passes through the polarizing beam splitter 34, passes through half mirrors 15 to 17, and forms an image on the surface of the disk.

In this way, in this example, the polarizing beam splitter 34 and the 172-wavelength plate 33 are used because it is necessary to share the writing optical system and the reading optical system. However, if you just want the light to follow the same optical path, you can use just a polarizing beam splitter, but in that case, as shown in Figure 3 (A),
The shapes of the collimated beams emitted from the semiconductor lasers 11 and 1 are shown in Figure 3 (
B) As shown in view A, they will be shifted by 80 degrees from each other and will not match.

Therefore, the polarization directions of the two semiconductor lasers 11 and 31 are made the same in advance so that the beam shapes are the same when they are on the same optical path, and a 1/2 wavelength plate 35 is installed in only one optical system. By inserting the beams to make the polarization direction perpendicular and connecting them with the polarization beam splitter 34, the same optical path and beam shape can be achieved. That's what I do. Therefore, according to this example, the reading optical system and the writing optical system can be used in common as will be described later, and it is also possible to write while tracking. Note that the other configurations are almost the same as the conventional device shown in the first figure, so a detailed explanation thereof will be omitted.

Next, the operation of the present device will be described in more detail with reference to FIGS. 4A and 4B, which show the main components shown in the second figure, together with the polarization directions. The polarization direction of the beam emitted from the semiconductor laser 31 during writing is in the direction of an arrow 52 in the figure, as water f on the page, but when it passes through the 172 wavelength plate 33, its polarization direction becomes a direction 53 perpendicular to the page. Therefore, since the beam becomes S-polarized for the polarizing beam splitter 34, it is reflected by the polarizing beam splitter 34. Furthermore, since the polarization direction of the beam emitted from the semiconductor laser 11 during reading is also in the direction of the arrow 51 in the drawing, which is horizontal to the plane of the paper, it becomes P-polarized light for the polarization beam splitter 34 and is transmitted through the polarization beam splitter 34 . Therefore,
On the output side optical axis of the polarizing beam splitter 34.

In the B view seen along the line, the beam shapes of both beams match as shown in FIG. 4(B). The beam emitted from the polarizing beam splitter 34 passes through a half mirror 15, is reflected by a tracking mirror 16, and is imaged onto the disk 7 by an objective lens 17 as a beam sponde. At this time, the disk 7 is rotated at a predetermined speed by the drive motor IO via the spindle 8 in the same manner as described above.

The reflected light reflected from the disk 8 passes through the objective lens 17,
After being reflected by the tracking mirror 16 and further reflected by the half mirror 15, it is divided into two by the primary nof mirror 18, and the two divided beams pass through the respective polarizing plates 18 or 21, detector 2
0 or 22. Although not shown in FIG. 3, the detection section that receives signals from the detectors 20 and 22 includes a known tracking detector and focus control means.

Also, during writing, one of the semiconductor transistors 31
oscillates strongly to raise the temperature at the position of the beam beam (y) on the disk 7 to more than one Curie point.
Write information to H. Further, during reading, only the other semiconductor laser 11 oscillates with its intensity weakened,
Read the information written on the disk 7. Furthermore, during additional writing, both semiconductor lasers 11 and 31 are oscillated simultaneously, tracking control is performed using the beam of the semiconductor laser 11 for reading, and additional writing is performed using the beam of the semiconductor laser 31 for writing. conduct.

Effects As explained above, according to the present invention, two lasers with the same polarization direction are used, and an optical means (polarizing beam splitter) for matching the optical paths of the output beams and a 1/2 wavelength plate for matching the beam shapes are used. Since the same beam shape and the same optical path are configured, it is possible to share the writing system and the reading system, and it is possible to perform additional writing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a conventional device, FIG. 2 is a diagram showing an example of the configuration of the writing/reading device of the present invention, and FIG.
) is a diagram used to explain the present invention in detail, and FIG. 3 (
B) is a diagram showing the shape of the beam as seen from the direction of the arrow in FIG. 3(A), FIG. 4(A) is a diagram showing the main configuration of the device shown in FIG. 2 along with the polarization direction, Figure 4 (B) is shown in Figure 4 (
FIG. 3 is a diagram showing the shape of the beam seen from the direction of arrow B in A). 1.11.31...Semiconductor laser, 2.12.32...Collimator lens, 3.34...
・Polarizing beam splitter, 4...1/4 wavelength plate. 5... Reflection mirror, 6.17... Objective lens, 7... Disk (magneto-optical disk memory). 8.20.22...Detector, 8...Spindle, 10...Drive motor, 13.1111.21...Polarizing plate, 14...Grating, 15.18...Half mirror-1 16...Tracking mirror, 23...Comparator, 33...172 wavelength plate. Figure 2 22 Figure 3 (A) CB)

Claims (1)

[Scope of Claims] 1) In an information recording and reproducing apparatus that records and reproduces information using a magneto-optical disk memory, first and second halves outputting beams having the same polarization direction; an l/2 wavelength plate that changes the polarization direction of the beam output from the first semiconductor laser; ! A magneto-optical recording method characterized by comprising an optical means for making the beam passing through the A172 wavelength plate and the beam output from the second semiconductor laser incident thereon and reflecting or transmitting them on the same optical path. reading device. 2. In the device according to claim 1. A magneto-optical recording type writing/reading device, wherein the optical means is a polarizing beam splitter.