JPS61198455A - Otpomagnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the efficiency of optical transmission by providing an optical multiplexer multiplexing laser light outputted from plural laser light sources and a single optical fiber transmitting light from the optical multiplexer and irradiating the light source from one end face toward an optical magnetic recording medium. CONSTITUTION:The linearly polarized laser light irradiated from a couple of laser elements 10, 12 with fixed position and different wavelength is condensed respectively by lenses 22, 24 on incident end faces 18, 20 with fixed position of single core repeater optical fibers 14, 16 so as to couple the repeater optical fibers 14, 16 and the leaser elements 10, 12 optically. The laser light is multiplexed into one optical path by an optical synthesizer 26, transmitted through a single core irradiated light transmission optical fiber 28 and condensed respectively on the 1st recording layer 36 and the end recording layer 38 of the photomagnetic recording medium 34 through an objective lens 32 from an irradiation end face 30. Thus, number of components is reduced, the optical transmission efficiency of an optical head is improved and miniaturization is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an apparatus for recording or reproducing information with a magneto-optical recording medium using light.

Prior Art In order to record and reproduce information, a laser beam output from a laser light source is converged and irradiated onto each of a plurality of recording layers stacked on a magneto-optical recording medium, and a laser beam is emitted from the irradiated area of the magneto-optical recording medium. A magneto-optical recording and reproducing apparatus has been considered in which the reflected light or transmitted light of the light is detected by an optical sensor. For example, patent application No. 59-22874 filed earlier by the present applicant.
This is the device described in No. 4. This type of magneto-optical recording/reproducing device is characterized by a dramatically increased information recording density per unit area of the magneto-optical recording medium.

Problems to be Solved by the Invention However, in such conventional devices, the optical head includes a plurality of types of light source parts, the number of which corresponds to the number of recording layers, each consisting of a laser light source and a collimator lens, and a plurality of types of light source units with different wavelengths. A gicroic mirror for combining laser light into a common optical path or separating the combined light into respective i lengths, and a half mirror for separating reflected light or transmitted light from a magneto-optical recording medium from irradiated light. Alternatively, since a polarized e-muslinometer, an objective section consisting of an objective lens, etc., and a light detection section consisting of a convex lens, a cylindrical lens, an optical sensor, etc. are arranged, the shape and weight of the optical head become large, making it impossible to sufficiently reduce the access time. Furthermore, since there are many optical components, there is a drawback that the loss of light quantity increases and the efficiency decreases, and the apparatus becomes expensive because it is necessary to increase the precision of the optical components and their relative positions.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist of this is that, in order to record or reproduce information, laser beams of multiple wavelengths output from multiple types of laser light sources are focused and applied to multiple recording layers in a magneto-optical recording medium. A magneto-optical recording and reproducing device of the irradiation type, comprising: (1) an optical multiplexer that multiplexes multiple types of laser beams respectively output from the multiple types of laser light sources; and (2) a A single optical fiber that transmits light and emits a laser beam from one end face toward the magneto-optical recording medium.

Operation and Effect of the Invention With this method, multiple types of light irradiated from multiple laser light sources to each recording layer of a magneto-optical recording medium are combined into one optical path by an optical multiplexer and then combined into a single light beam. Transmitted via fiber. Therefore, at least a light source section such as a laser light source or a collimator lens is positioned relative to an objective section such as an objective lens that is positioned facing the magneto-optical recording medium and moves along the recording surface of the magneto-optical recording medium. Since the positional relationship can be arranged independently, there is no need to align the light source part and the objective part, and the highly rigid frame that maintains the relative positional accuracy between parts can be made smaller, resulting in a smaller optical head. It is lightweight and inexpensive. Furthermore, since the optical head is small and lightweight, its inertial weight is reduced and access time can be shortened. In particular, if only the objective part of the optical head is made a movable head movable part, the inertial weight is further reduced and the access time can be significantly shortened. Furthermore, it eliminates the need for dichroic mirrors to combine and separate multiple types of laser beams, and also eliminates the need for half mirrors or polarizing beam splitters to separate irradiated light and reflected light, reducing the number of parts. Since the optical head is reduced in size, the optical head can be made more compact and has an increased optical transmission efficiency.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram showing the configuration of the main parts of an optical head of a magneto-optical recording/reproducing apparatus. Linearly polarized laser light emitted from a pair of semiconductor laser elements 10 and 12 that are fixed in position and have different wavelengths is transmitted through a single-core relay optical fiber 4.
The light beams are focused by lenses 22 and 24 on incident-side end faces 18 and 20 of fixed positions 16 and 16, respectively, thereby optically coupling relay optical fibers 14 and 16 to semiconductor laser elements 10 and 12. The laser beams having different wavelengths propagated through the relay optical fibers 14 and 16 are combined into one optical path by an optical multiplexer 26, and then transmitted through a single-core irradiation light transmission optical fiber 28, The objective lens 32 is
The light is focused on the first recording layer 36 and the second recording layer 38 of the magneto-optical recording medium 34, respectively. Even though the laser beams having different wavelengths pass through a common objective lens 32, their focal positions differ in the thickness direction of the magneto-optical recording medium 34.
The recording layer 36 and the second recording layer 38 are formed at the focal position. Therefore, when reading information recorded on the first recording layer 36 or the second recording layer 38 or recording information on the first recording layer 36 or the second recording layer 38, the first recording layer 36 or the second recording layer Laser spots are formed at desired positions on each of the 38 tracks.

The reflected light from the magneto-optical recording medium is received by the emission side end face 42 of a large number of reflected light transmission optical fibers 400 Å which are bundled around the outer periphery of the irradiated light transmission optical fiber 28 . The optical fiber 40 for transmitting reflected light is branched into two bundles, and the light transmitted within the optical fiber 40 for transmitting reflected light is emitted from the output side end faces 44 and 46 of each bundle into light for detecting information signals at a fixed position. It is guided to a sensor 48 and an optical sensor 50 for detecting focusing or tracking signals. In this embodiment, the optical fibers 40a bundled on the inner circumferential side of the optical fibers 40 for transmitting reflected light are branched to the optical sensor 48 side,
Optical fibers 40b bundled on the outer circumferential side are branched toward the optical sensor 50 side. Of the reflected light from the magneto-optical recording medium 34, the information signal representing the information signal travels in the opposite direction along substantially the same optical path as the irradiated light and reaches the incident side end face 42 of the reflected light transmission optical fiber 40a.
However, among the reflected light from the magneto-optical recording medium 34, the one used to extract the focusing or tracking signal is diffracted light, so the incident side end face 42b of the reflected light transmission optical fiber 40b It is incident on .

The optical sensor 48 includes a photodetecting element that receives the laser beam transmitted through the reflected light transmission optical fiber 40a and converts it into an electrical signal representing information, and also requires an analyzer for detecting the Kerr rotation angle. We are prepared accordingly. The optical sensor 50 includes a plurality of photodetecting elements that receive the laser beam transmitted through the optical fiber 40b for transmitting reflected light, convert it into an electrical signal representing focusing or tracking information, and output it to the controller I/roller 51. There is. Further, the optical sensor 48 and the optical sensor 50 are equipped with a dichroic mirror for separating laser beams of two types of wavelengths and a photodetecting element corresponding to each type of laser beam, and the first recording layer 36 and 2 reflected from the recording layer 38, respectively.
Laser beams of different wavelengths are detected. However, it is also possible to operate the semiconductor laser elements 10 and 12 selectively and in a time-divisional manner, so in such a case, the dichroic ink mirror can be removed and two types of wavelengths can be detected using a common photodetector. Laser light can be detected.

A head movable section 52 that is driven along a direction intersecting a track (not shown) of the magneto-optical recording medium 34 is provided with the objective lens 32 and the optical fiber 2.
8.40 ends are connected, making the movable parts small and lightweight. For example, as shown in FIG. 2, the head movable section 52 is fixed to a movable plate 58 that is guided by a pair of guide rods 54 and 56 that are fixedly provided facing the magneto-optical recording medium 34. A moving coil 60 is fixed to the movable plate 58, and the moving coil 60 receives a driving force from a magnetic field formed by permanent magnets 62, 64. Therefore, the head movable section 52 is positioned at a position corresponding to one of the many tracks by controlling the excitation state of the moving coil 60.

The head movable section 52 is equipped with a focusing mechanism that moves the objective lens 32 in the optical axis direction and a tracking mechanism that moves the objective lens 32 in a direction perpendicular to the optical axis direction, and these focusing mechanism and tracking mechanism are controlled by the controller 51. As a result, a laser beam of an optimal size is placed on the track of the magneto-optical recording medium 34 regardless of variations in the distance between the magneto-optical recording medium 34 and the objective lens 32 or displacement of the track on the magneto-optical recording medium 34. Spots are preferably formed. That is, as shown in FIG.
A movable member 68 supported movably in the optical axis direction by
The objective lens 32 is supported movably in the optical axis direction and in a direction perpendicular to the optical axis (a direction intersecting the tracks of the magneto-optical recording medium 34). A magnetic field from a permanent magnet 74 is applied to a focusing coil 72 fixed to a movable member 68.
The position of the objective lens 32 in the optical axis direction is controlled in accordance with the current supplied from the controller 51 to the focusing coil 72. Further, a permanent magnet 7 is also attached to a frame-shaped magnetic member 76 that directly supports the objective lens 32.
8 is applied, and the position of the objective lens 32 in the direction perpendicular to the optical axis is controlled in accordance with the current supplied from the controller 51 to the tracking coil 80. The tracking coil 80 is arranged so that the magnetic force acting on the magnetic member 76 is changed by the magnetic field of the permanent magnet 78. The optical fiber 28 for transmitting irradiated light and the optical fiber 40 for transmitting reflected light
The end portion of the fiber holder 82 is fixed within a cylindrical fiber holder 82, and the fiber holder 82 is fixed to the head movable portion 52 so that the optical fiber 28 for transmitting irradiated light substantially coincides with the optical axis of the objective lens 32. .

The first recording layer 36 and the second recording layer 38 are made of a magneto-optical material such as GdTbFe, and are formed with a non-magnetic intermediate layer such as SiC2 in between. And the first
Regardless of the perpendicular magnetization direction of one of the recording layer 36 and the second recording layer 38, information recorded in the other can be read out.
The respective wavelengths of the laser beams output from the semiconductor laser elements 10 and 12 are, for example, about 8,300 and 7,800, and the thickness of the first recording layer 36 is, for example, about 100.
It is determined by the number of people. As a result, the patent application No. 59-2
As detailed in No. 28744, the first recording layer 36
By perpendicularly magnetizing the second recording layer 38, the stored information can be individually reproduced. Further, the depth of focus (distance in the optical axis direction of the focal point) of the two types of laser beams output from the semiconductor laser elements 10 and 12, respectively, is determined by the thickness of the intermediate layer sandwiched between the first recording layer 36 and the second recording layer 38. Since the magnetization is also made small, when one of the first recording layer 36 and the second recording layer 38 is irradiated when recording information, the magnetization of the other is not canceled.

According to the apparatus configured as described above, a light source section consisting of a semiconductor laser element O and 12, lenses 22 and 24, etc., an optical sensor 48 for detecting an information signal, and an optical sensor 50 for detecting a focusing or tracking/knocking signal.
The detection unit consisting of etc. is installed in a fixed position, and
An objective section consisting of an objective lens 32 and the like is fixed to a gutter movable section 32 that is driven along the recording surface of the magneto-optical recording medium in a direction perpendicular to the track. For this reason, compared to the conventional case in which the light source section, detection section, and objective section are fixed integrally while maintaining a certain mutual positional accuracy, a half mirror or a Since optical parts such as a polarizing beam splitter and a quarter-wave plate are not required, the number of parts is reduced, so that the optical head can be made more compact and has higher optical transmission efficiency. Furthermore, since the light source sections such as the laser elements 10 and 12 and the collimator lenses 22 and 24 and the detection section such as the convex lens, cylindrical lens, and optical sensor can be arranged independently with respect to the objective section, the light source section, In addition, positioning between the detection section and the objective section is no longer necessary, and the highly rigid frame for maintaining relative positional accuracy between parts is made smaller, making the head movable section 52 smaller, lighter, and less expensive. Furthermore, since the optical head is small and lightweight, the inertial weight is reduced, and access time can be significantly shortened.

Although the head movable section 52 is provided with only an objective section, even if a light source section and a detection section are additionally provided, the relative positional relationship between the light source section and detection section and the objective section can be determined independently. Since there is no change in the arrangement, the effects of the present invention can be obtained to some extent.

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The shape of the end face of the optical fiber 28, 40 may be flat, convex, or concave, as shown in FIGS. 4, 5, and 6. For focusing on the magneto-optical recording medium 34, the seventh
The structure may be configured as shown in FIG. 8, FIG. 9, and FIG. 7th
In the apparatus shown in the figure, one convex lens 84 collimates the laser beam, and the other convex lens 86 collimates the laser beam onto the magneto-optical recording medium 3.
Focus on the top. The apparatus shown in FIG. 8 focuses laser light onto the magneto-optical recording medium 34 using a light-focusing waveguide 88 such as a Selfoc lens. In the apparatus shown in FIG. 9, the end surface of the optical fiber 28 for transmitting irradiated light is formed into a convex shape, and the laser beam is focused onto the magneto-optical recording medium 34 by the convex lens action of the convex surface.

The branching method of the reflected light transmission optical fiber 40 is as follows.
As shown in the figure, the cross section may be branched into a fan-shaped cross section along a straight line in the radial direction, or may be branched randomly. Also, the first
As shown in FIG. 1, a photodiode array 90 in which a large number of photodetecting elements are arranged is used to detect laser light transmitted through individual optical fibers constituting an optical fiber 40 for transmitting reflected light. You can also do it.

As shown in FIG. 12, an optical sensor 4 is provided between the optical sensor 48 and the optical fiber 40a for transmitting reflected light, and between the optical sensor 50 and the optical fiber 40b for transmitting reflected light.
a convex lens 92 that focuses the laser beam onto the photodetector element 8;
, an analyzer 93 for detecting the Kerr rotation angle, and optical components such as a convex lens 94 and a cylindrical lens 96 for condensing laser light onto the photodetection element of the optical sensor 50 may be provided, respectively.

The optical fiber 40 for transmitting reflected light may be composed of a multi-core optical fiber used for a so-called image guide.
As shown in FIG. 3, it may be constructed by arranging a plurality of bundles of multi-core optical fibers 98 around the optical fiber 28 for transmitting irradiated light, and as shown in FIG. A plurality of single-core optical fibers 100 may be bundled around the optical fiber 28.

Further, the optical fiber 28.40.98.100 is generally made of quartz, but may also be made of plastic to reduce weight. In this case, the head movable section 32 becomes even lighter. The optical fiber 28.40.98.100 can also be composed of a polarization maintaining fiber. In this case, since rotation of the plane of polarization during transmission of the irradiated light and reflected light is prevented, the information stored in the magneto-optical recording medium 34 can be read out more accurately.

Furthermore, since information can be reproduced by detecting transmitted light instead of reflected light from the magneto-optical recording medium 34, as shown in FIG. , an optical fiber 102 for transmitting transmitted light configured similarly to the optical fiber 40 for transmitting reflected light, and a convex lens 104 that focuses the transmitted light from the magneto-optical recording medium 34 on the end face of the optical fiber 102 for transmitting transmitted light. may be provided on the opposite side to the objective lens 32.

Further, in the above embodiment, it is explained that the writing irradiation light and the reproduction irradiation light are output from the same device, but the writing irradiation light and the reproduction irradiation light are output from different devices. It may be configured to be output.

Furthermore, although laser beams with two types of wavelengths are used in the above embodiments, laser beams with three or more types of wavelengths corresponding to the number of recording layers may be used.

In such a case, an optical multiplexer that combines laser beams of three or more wavelengths into one optical path is required.

Note that the above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a perspective view showing how the head movable part of FIG. 1 is attached. FIG. 3 is a cross-sectional view showing the configuration of the head movable section shown in FIG. 1. FIGS. 4 to 6 are diagrams showing other examples of end face shapes of the optical fiber for transmitting irradiated light and the optical fiber for transmitting reflected light, respectively. FIGS. 7 to 9 are diagrams respectively showing other configuration examples in which the irradiation light is irradiated onto the magneto-optical recording medium from the optical fiber for transmitting the irradiation light. FIGS. 10 and 11 are diagrams respectively showing other branching structures of the optical fiber for transmitting reflected light. FIG. 12 is a diagram showing another method in which a light sensor receives light emitted from a reflected light transmission optical fiber. FIGS. 13 and 14 are diagrams showing other configuration examples of the optical fiber for transmitting reflected light. FIG. 15 is a diagram showing an example of detecting transmitted light instead of reflected light. 10.12: Semiconductor laser element (laser light source) 26: Optical multiplexer 28: Optical fiber for transmitting irradiated light (optical fiber) 34: Magneto-optical recording medium Applicant Brother Industries, Ltd. @3 Figure 10 and 12

Claims (1)

[Claims] In order to record or reproduce information, laser beams of a plurality of wavelengths output from a plurality of laser light sources are focused and irradiated to a plurality of recording layers in a magneto-optical recording medium, respectively. A magneto-optical recording and reproducing device of the type, comprising: an optical multiplexer that multiplexes multiple types of laser beams respectively output from the multiple types of laser light sources; and an optical multiplexer that transmits the light from the optical multiplexer; A single optical fiber that emits a laser beam from the magneto-optical recording medium toward the magneto-optical recording medium.