JPH0690816B2 - Magneto-optical recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for recording or reproducing information with a magneto-optical recording medium by using light.

2. Description of the Related Art In order to record / reproduce information, a laser beam emitted from a laser light source is converged to irradiate each of a plurality of recording layers stacked on a magneto-optical recording medium, and from an irradiation portion of the magneto-optical recording medium. A magneto-optical recording / reproducing apparatus of the type in which the reflected light or the transmitted light is detected by an optical sensor has been considered. For example, the apparatus described in Japanese Patent Application No. 59-228744 filed by the applicant of the present application is that. The magneto-optical recording / reproducing apparatus of this type is characterized in that the information recording density per unit area of the magneto-optical recording medium is dramatically increased.

However, in such a conventional device, a plurality of types of light source units corresponding to the number of recording layers including a laser light source and a collimator lens in the optical head, and laser lights of a plurality of types of wavelengths are formed on a common optical path. Consists of a dichroic mirror for combining or separating the combined light into respective wavelengths, a half mirror or a polarization beam splitter for separating reflected light or transmitted light from the magneto-optical recording medium and irradiation light, an objective lens, etc. Since the light detecting portion including the objective portion, the convex lens, the cylindrical lens, and the optical sensor is arranged, the shape and weight of the optical head becomes large, and the access time cannot be shortened sufficiently. Further, since there are many optical components, there is a drawback that the loss of light amount becomes large and the efficiency is reduced, and it becomes expensive because it is necessary to increase the precision of the optical components and mutual position between them.

On the other hand, as described in JP-A-55-29886, the irradiation light is transmitted by a single optical fiber by using an optical multiplexer that multiplexes a plurality of types of laser light having different wavelengths. As described in JP-A-58-150146, the irradiation light and the reflected light are transmitted between a light source and a photodetector whose position is fixed and a movable head portion which is movable relative to the recording medium. By providing the optical fiber, the light source part such as the laser light source and the collimator lens can be independently fixed in position with respect to the movable part (objective part) movably provided with respect to the magneto-optical recording medium. Since the alignment of the light source part and the objective part is not necessary, the frame is made smaller, the optical head becomes smaller and lighter and cheaper, and the movable part becomes smaller and the inertial weight becomes smaller. Can be shortened There is an advantage.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in the magneto-optical recording / reproducing apparatus configured as described above, the information recorded on the magneto-optical recording medium is such that the irradiation light is emitted from the end face of a single irradiation light transmitting optical fiber. The information is recorded along a predetermined track on the magneto-optical recording medium while being reproduced by the reflected light from the magneto-optical recording medium at the time of recording, and the relative position of the magneto-optical recording medium with respect to the optical head during reproduction. Since the distance fluctuates, focusing control for maintaining the focused diameter of the irradiation light at a predetermined value and tracking of the focused position of the irradiation light are performed during the period for reproducing the information recorded on the magneto-optical recording medium. Tracking control is performed so as to follow the information storage area.

However, in the conventional magneto-optical reproducing apparatus, since the reflected light from the magneto-optical recording medium is detected at a position provided on one side of the light irradiation position, a sufficient signal may not always be obtained. It was That is, the reflected light containing the recorded information signal is reflected in the same optical path as the irradiation light, but the reflected light used as the tracking signal is diffracted light due to light wave interference. Since it is emitted obliquely from the irradiation point, the diffracted light in the oblique direction cannot always be detected as a signal having a sufficient magnitude.

The present invention has been made in the background of the above circumstances,
The purpose is to obtain a diffracted light reflected in an oblique direction, that is, a reflected light used as a tracking signal, out of the reflected light reflected from the magneto-optical recording medium, as a signal having a sufficient magnitude. It is to provide a magnetic recording / reproducing apparatus.

Means for Solving the Problems The gist of the present invention for achieving the above-mentioned object is to provide a laser beam of a plurality of types of wavelengths respectively output from a plurality of types of laser light sources in order to record or reproduce information. In a magneto-optical recording / reproducing apparatus of the type in which a plurality of recording layers in a magneto-optical recording medium are focused and irradiated, (a) a plurality of types of laser light respectively output from the plurality of types of laser light sources are combined. And a single irradiation light transmission light for guiding the laser light output from the optical multiplexer and irradiating the laser light toward the magneto-optical recording medium from an end face through an objective lens. A fiber, and (c) injecting reflected light from the magneto-optical recording medium to detect an information signal, a focusing signal, and a tracking signal included in the reflected light from the magneto-optical recording medium. A plurality of reflected light transmission optical fibers bundled in a state of surrounding the irradiation light transmission optical fiber so that the end face is located around the end surface of the irradiation light transmission optical fiber on the side of the magneto-optical recording medium. To include.

As a result, the light reflected from the magneto-optical recording medium, particularly the oblique direction from the magneto-optical recording medium, is reflected by the reflected-light transmitting optical fibers that are bundled in a state of surrounding the irradiation optical transmission optical fiber. Since the diffracted light (reflected light used as a tracking signal) to be emitted is sampled and guided, the diffracted light can be obtained as a sufficiently large signal.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a main configuration 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 from each other is a single-core relay optical fiber 14 and
16 fixed entrance end faces 18 and 20 with lens 22 and
The light beams are respectively collected by 24, and thereby the relay optical fibers 14 and 16 and the semiconductor laser devices 10 and 12 are optically coupled. The laser lights having different wavelengths that have respectively propagated in the relay optical fibers 14 and 16 are multiplexed into one optical path by the optical multiplexer 26, and then transmitted through the single-fiber irradiation light transmission optical fiber 28. The first recording layer of the magneto-optical recording medium 34 from the exit side end face 30 through the objective lens 32.
The light is focused on the 36 and the second recording layer 38, respectively. Since the laser light beams having different wavelengths have different focal positions in the thickness direction of the magneto-optical recording medium 34 even through the common objective lens 32,
The first recording layer 36 and the second recording layer 38 are formed at their focal positions. Therefore, the information recorded on the first recording layer 36 or the second recording layer 38 is read or the first recording layer 36 thereof is read.
Alternatively, when information is recorded on the second recording layer 38, laser spots are respectively formed at desired positions on the tracks of the first recording layer 36 or the second recording layer 38.

The reflected light from the magneto-optical recording medium is received by the incident side end face 42 of the large number of reflected light transmitting optical fibers 40 bundled on the outer circumference of the irradiation light transmitting optical fiber 28. The optical fiber 40 for reflected light transmission is branched into two bundles, and the light transmitted in the optical fiber 40 for reflected light transmission is a fixed-position information signal detection light from the output side end faces 44 and 46 of each bundle. It is led to a sensor 48 and an optical sensor 50 for detecting a focusing or tracking signal. In the present embodiment, the optical fiber 40a bundled on the inner peripheral side of the optical fiber 40 for reflected light transmission.
Is branched to the optical sensor 48 side, and the optical fiber 40b bundled on the outer peripheral side is branched to the optical sensor 50 side. Of the reflected light from the magneto-optical recording medium 34, the one that represents the information signal is the optical fiber 40 for transmitting the reflected light by reversing the same optical path as the irradiation light.
Although incident on the incident side end surface 42a of a, the reflected light from the magneto-optical recording medium 34 is used for detecting the focusing or tracking signal is diffracted light,
It is incident on the incident side end face 42b of the reflected light transmitting optical fiber 40b.

The optical sensor 48 includes a photodetector element that receives laser light transmitted through the reflected-light transmission optical fiber 40a and converts it into an electric signal representing information, and requires an analyzer for detecting the Kerr rotation angle. Prepared accordingly. The optical sensor 50 is provided with a plurality of photo-detecting elements that receive the laser light transmitted through the reflected-light transmitting optical fiber 40b, convert the laser light into an electrical signal representing focusing or tracking information, and output the electrical signal to the controller 51. Further, the optical sensor 48 and the optical sensor 50 each include a dichroic mirror for separating laser light of two kinds of wavelengths and a photodetector element corresponding to each kind of laser light inside, and the first recording layer 36 and the first recording layer 36 The laser beams of two kinds of wavelengths reflected from the two recording layers 38 are detected respectively. However, since the semiconductor laser devices 10 and 12 can be operated selectively and in a time-division manner, in such a case, the dichroic mirror is removed and the laser light of two kinds of wavelengths is shared by the common photodetector. Can be detected.

The objective lens 32 is provided in the head movable portion 52 which is driven along the direction intersecting with a track (not shown) of the magneto-optical recording medium 34, and the end portions of the optical fibers 28 and 4 are connected to the movable portion. Is small and lightweight. The head movable part 52 is, for example, as shown in FIG.
It is fixed to a movable plate 58 which is guided by a pair of guide rods 54 and 56 which are fixedly provided while facing the magneto-optical recording medium 34. A moving coil 60 is fixed to the movable plate 58,
The moving coil 60 receives a driving force by the magnetic field formed by the permanent magnets 62 and 64. Therefore, the head moving part
52 is positioned at a position corresponding to one of many tracks by controlling the excitation state of the moving coil 60.

The head movable part 52 is provided with a focusing mechanism for moving the objective lens 32 in the optical axis direction and a tracking mechanism for moving 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, fluctuations in the distance between the magneto-optical recording medium 34 and the objective lens 32 and the magneto-optical recording medium 34
A laser beam spot having an optimum size is preferably formed on the track of the magneto-optical recording medium 34 regardless of the positional deviation of the upper track. That is, as shown in FIG. 3, the objective lens 32 is attached via a leaf spring 70 to a movable member 68 supported by a leaf spring 66 so as to be movable in the optical axis direction. And is supported so as to be movable in a direction perpendicular to the optical axis (direction intersecting with the track of the magneto-optical recording medium 34). The magnetic field of the permanent magnet 74 is applied to the focusing coil 72 fixed to the movable member 68, and the objective lens 32 corresponds to the current supplied from the controller 51 to the focusing coil 72.
The position in the direction of the optical axis is controlled. In addition, the magnetic field of the permanent magnet 78 is also applied to the frame-shaped magnetic member 76 that directly supports the objective lens 32.
The position of the objective lens 32 in the direction perpendicular to the optical axis is controlled according to the current supplied from the 51 to the tracking coil 80. The tracking coil 80 is arranged so as to change the magnetic force acting on the magnetic member 76 by the magnetic field of the permanent magnet 78. The ends of the irradiation light transmitting optical fiber 28 and the reflected light transmitting optical fiber 40 are fixed in a cylindrical fiber holder 82, and the irradiation light transmitting optical fiber 28 substantially coincides with the optical axis of the objective lens 32. As described above, the fiber holder 82 is fixed to the head movable portion 52.

The first recording layer 36 and the second recording layer 38 are made of, for example, GdTb.
It is made of a magneto-optical material such as Fe, and is formed by sandwiching a non-magnetic intermediate layer such as SiO ₂ . Then, the wavelengths of the laser beams output from the semiconductor laser elements 10 and 12 are set so that the information recorded on the first recording layer 36 and the second recording layer 38 can be read regardless of the perpendicular magnetization direction. Is set to about 8300Å and 7800Å, and the thickness of the first recording layer 36 is set to about 100Å, for example. As a result, as described in detail in Japanese Patent Application No. 59-228744, the first
By perpendicularly magnetizing the recording layer 36 and the second recording layer 38, the stored information can be reproduced separately. Also,
2 output from each of the semiconductor laser devices 10 and 12
Since the depth of focus (distance in the optical axis direction of the focus) of each type of laser light is made smaller than the thickness of the intermediate layer sandwiched by the first recording layer 36 and the second recording layer 38, the first recording is performed when recording information. When irradiating one of the layer 36 and the second recording layer 38, the magnetization of the other is not eliminated.

According to the apparatus configured as described above, the semiconductor laser elements 10 and 12 and the light source unit including the lenses 22 and 24, and the information signal detecting optical sensor 48 and the focusing or tracking signal detecting optical sensor 50 are included. The detection unit is fixedly provided, and the objective unit including the objective lens 32 and the like is fixed to the head movable unit 32 which is driven along the recording surface of the magneto-optical recording medium in the direction perpendicular to the track. Therefore, as compared with the conventional case in which the light source unit, the detection unit, and the objective unit are integrally fixed while maintaining a constant mutual positional accuracy, a half mirror for separating the irradiation light and the reflected light, or Since the optical components such as the polarization beam splitter and the quarter-wave plate are not needed, the number of components is reduced, so that the optical transmission efficiency of the optical head is improved and the size is reduced. In addition, the laser elements 10 and 12, the collimator lens 22
Since the relative positions of the light sources such as and 24 and the convex lens, the cylindrical lens, and the optical sensor can be independently arranged with respect to the objective, it is not necessary to align the light source and the detector with the objective. Therefore, the high-rigidity frame body for maintaining the relative positional accuracy between the components is made small, and the head movable portion 52 becomes small, lightweight and inexpensive. Further, since the optical head is small and lightweight, the inertial weight is small, and the access time can be greatly shortened.

Further, according to the present embodiment, a large number of reflected light transmission optical fibers 40a, 40b bundled in a state of surrounding the irradiation light transmission optical fiber 28, the light reflected from the magneto-optical recording medium 34, especially the magneto-optical Since the diffracted light (reflected light used as a tracking signal) that is emitted obliquely from the recording medium is sampled and guided, there is an advantage that the diffracted light can be obtained as a sufficiently large signal.

Although only the objective section is provided in the head movable section 52, even if the light source section and the detection section are additionally provided, the relative positional relationship between the light source section and the detection section and the objective section is independently provided. Since the arrangement is the same, the tentative effect of the present invention can be obtained.

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

The end faces of the optical fibers 28 and 40 may be flat, convex, or concave as shown in FIGS. 4, 5, and 6, and the laser light emitted from the end faces of the optical fibers 28 may be In order to focus on the magneto-optical recording medium 34, FIGS.
It may be configured as shown in FIGS. In the apparatus shown in FIG. 7, the laser beam is made parallel by one convex lens 84 and then focused on the magneto-optical recording medium 34 by the other convex lens 86. The apparatus shown in FIG. 8 focuses the laser light on the magneto-optical recording medium 34 by a light focusing waveguide 88 such as a SELFOC lens. In the device shown in FIG. 9, the end face of the irradiation light transmitting optical fiber 28 is formed in a convex shape, and the laser light is focused on the magneto-optical recording medium 34 by the convex lens action of the convex surface.

The optical fiber 40 for transmitting reflected light may be branched in a fan-shaped cross section with a radial straight line as a boundary as shown in FIG. 10, or may be branched randomly. Further, as shown in FIG. 11, by using a photodiode array 90 in which a large number of photodetector elements are arranged, laser light transmitted through the individual optical fibers constituting the optical fiber 40 for reflected light transmission is transmitted. You may make it detect.

Between the optical sensor 48 and the optical fiber 40a for reflected light transmission,
Further, between the optical sensor 50 and the reflected light transmitting optical fiber 40b, as shown in FIG. 12, a convex lens 92 for converging laser light on the photodetector element of the optical sensor 48, and a Kerr rotation angle are detected. Analyzer 93, and a convex lens 94 and a cylindrical lens 96 for condensing the laser light on the photodetection element of the optical sensor 50.
Optical parts such as may be provided respectively.

The reflected light transmission optical fiber 40 may be configured by a multi-core optical fiber used for a so-called image guide, but as shown in FIG. 13, a plurality of bundles of multi-core light are provided around the irradiation light transmission optical fiber 28. It may be configured by arranging the fiber 98, or may be configured by bundling a plurality of single-core optical fibers 100 around the irradiation light transmitting optical fiber 28 as shown in FIG.

The optical fibers 28, 40, 98 and 100 are generally made of quartz, but can be made of plastic and are lightweight.
In this case, the head movable portion 32 becomes even lighter. Also,
The optical fibers 28, 40, 98, 100 may also be composed of polarization-maintaining fibers. In this case, the rotation of the polarization plane is prevented during the transmission of the irradiation light and the reflected light, so that the information stored in the magneto-optical recording medium 34 can be read more accurately.

Further, in the above-described embodiment, it is described that the irradiation light for writing and the irradiation light for reproduction are output from the same device, but the irradiation light for writing and the irradiation light for reproduction are different from each other. It may be configured to be output.

Further, in the above-described embodiment, laser light of two kinds of wavelengths is used, but laser light of three or more kinds of wavelengths corresponding to the number of recording layers may be used. In such cases,
An optical multiplexer that multiplexes laser light of three or more wavelengths into one optical path is required.

The above description is merely an example of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is a perspective view showing an attached state of the head movable portion of FIG. FIG. 3 is a sectional view showing the structure of the head movable portion of FIG. 4 to 6 are views showing other examples of the end face shapes of the irradiation light transmission optical fiber and the reflected light transmission optical fiber, respectively. FIG. 7 to FIG. 9 are diagrams showing other examples of the structure for irradiating the magneto-optical recording medium from the irradiation light transmitting optical fiber. FIG. 10 and FIG. 11 are diagrams showing other branched structures of the reflected-light transmission optical fiber, respectively. FIG. 12 is a diagram showing another system in which the light emitted from the optical fiber for reflected light transmission is received by the optical sensor. FIG. 13 and FIG. 14 are diagrams showing another configuration example of the reflected-light transmission optical fiber. 10, 12: Semiconductor laser device (laser light source) 26: Optical multiplexer 28: Irradiation light transmission optical fiber 32: Objective lens 34: Magneto-optical recording medium 40a: Reflected light transmission optical fiber (inner circumference side reflected light transmission) Optical fiber) 40b: Optical fiber for transmitting reflected light (optical fiber for transmitting reflected light on the outer circumference side)

Claims (2)

[Claims] 1. In order to record or reproduce information, laser beams of a plurality of types of wavelengths output from a plurality of types of laser light sources are focused and irradiated onto a plurality of recording layers in a magneto-optical recording medium. A magneto-optical recording / reproducing apparatus of the type, wherein an optical multiplexer that multiplexes a plurality of types of laser light respectively output from the plurality of types of laser light sources, and a laser beam output from the optical multiplexer, A single irradiation light transmission optical fiber for irradiating a laser beam toward the magneto-optical recording medium from an end face through an objective lens, and an information signal included in reflected light from the magneto-optical recording medium,
In order to detect the focusing signal and the tracking signal, the end face on which the reflected light from the magneto-optical recording medium is made incident is located around the end face on the magneto-optical recording medium side of the irradiation light transmitting optical fiber. A magneto-optical recording / reproducing apparatus comprising: a plurality of reflected-light transmission optical fibers bundled in a state of surrounding the optical-transmission optical fiber. 2. A plurality of reflected light transmission optical fibers bundled in a state of enclosing the irradiation light transmission optical fiber, and are bundled on the inner periphery side to guide the reflected light to an information signal detecting optical sensor. The optical fiber for reflected light transmission and the optical fiber for reflected light transmission on the outer peripheral side which is bundled on the outer peripheral side and guides the reflected light to the optical sensor for detecting the focusing signal and the tracking signal. A magneto-optical recording / reproducing apparatus according to item.