JPH0827964B2 - Optical recording / reproducing device - Google Patents

Description

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

2. Description of the Related Art In order to record / reproduce information, a format in which laser light output from a laser light source is converged and applied to an optical recording medium, and reflected light from an irradiated portion of the optical recording medium is detected by an optical sensor. The optical recording / reproducing apparatus of is known. The optical recording / reproducing apparatus of such a type has a complicated and precise structure for focusing the laser beam to irradiate the optical recording medium and detecting the reflected light from the irradiation portion of the optical recording medium by the optical sensor. Equipped with an optical head. For example, as shown in FIG. 29, the laser light output from the laser light source 200 is collimated by the collimator lens 202, passes through the polarization beam splitter 204, the 1/4 wavelength plate 206, and the optical recording medium by the objective lens 208. Focused on 210. Optical recording medium 210
The reflected light from passes through the objective lens 208 and the 1/4 wavelength plate 206, is reflected by the polarization beam splitter 204, and then enters the optical sensor 216 via the convex lens 212 and the cylindrical lens 214. The optical sensor 216 includes a plurality of photo-detecting elements and outputs not only an information signal but also a tracking signal and a focusing signal. Then, an objective lens optical axis direction drive device is provided which drives the objective lens 208 in the optical axis direction based on the focusing signal in order to follow the fluctuation of the laser beam spot in the optical axis direction of the recording surface of the optical recording medium 210, Further, an objective lens optical axis vertical direction driving device for swinging the laser beam spot so as to follow the track of the optical recording medium 210 based on the tracking signal, or a tracking mirror and its driving device are provided.

Problems to be Solved by the Invention However, in such a conventional apparatus, in the optical head, a laser light source, a collimator lens, a half mirror or a polarization beam splitter, a quarter wavelength plate, an objective lens, a convex lens, a cylindrical lens, an optical Since various optical components such as sensors and a high-rigidity frame that holds their relative positions with high precision are arranged, the overall 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 lowered, and the optical components and the mutual positional accuracy between them are required to be highly accurate, which makes the apparatus expensive. In particular, when a plurality of types of laser light sources are used or when laser light is applied to a plurality of locations on the optical recording medium, such inconvenience becomes remarkable.

On the other hand, as recorded in Japanese Patent Application Laid-Open No. 58-150146, laser light output from a laser light source is guided by a first optical fiber to irradiate an optical disk, and reflected light from the optical disk There has been proposed an optical disc pickup in which a second optical fiber arranged in parallel with one optical fiber is guided to a light receiving element. According to this, compared to an optical head having various lenses such as a laser light source, a collimator lens, a half mirror or a polarization beam splitter, a 1/4 wavelength plate, and an objective lens inside, the weight of the movable part becomes smaller. There is an advantage that the access time can be shortened, the light amount loss is reduced, the efficiency is maintained, and the size and cost are reduced.

However, according to such a conventional optical pickup device, in order to make the reflected light from the optical disc enter the second optical fiber, a polarization beam splitter (calcite plate) is used.
It is necessary to provide an optical element such as a 1/4 wavelength plate or the like in the optical head portion, and the optical head is not sufficiently small and lightweight,
The access time could not be shortened sufficiently, and the light transmission efficiency could not be sufficiently obtained.

Further, as described in Japanese Patent Laid-Open No. 61-3335, irradiation is performed in which one end surface receives and transmits laser light output from a laser light source, and the other end surface irradiates the optical recording medium with laser light. The optical transmission optical fiber and one end face thereof are arranged so as to surround the other end face of the irradiation optical transmission optical fiber,
A read head for an optical memory has been proposed, which has four optical fibers for transmitting signal light, which guides the signal light from the irradiation portion of the optical recording medium to one end of the optical sensor. According to this, compared to an optical head having various lenses such as a laser light source, a collimator lens, a half mirror or a deflecting beam splitter, a 1/4 wavelength plate, and an objective lens inside, the weight of the movable portion becomes smaller. There is an advantage that the access time can be shortened, the light amount loss is reduced, the efficiency is maintained, and the size and cost are reduced.

However, according to such a conventional read head,
When the area of the end faces of the four signal light transmitting optical fibers arranged so as to surround the irradiation light transmitting optical fiber is small, a sufficient amount of reflection from the optical recording medium to each signal light transmitting optical fiber is performed. Light cannot enter, and the electrical signal output from the photosensor that converts the light into an electrical signal, that is, the electrical signal representing information and the electrical signal representing focusing or tracking information becomes small, so the detection accuracy of the electrical signal is sufficient. However, the reliability of signal reading is reduced. Further, since the small end face of the optical fiber for signal light transmission is locally located, there is a problem that continuous changes in focusing and tracking signals cannot be detected.

Means for Solving the Problems The present invention has been made in view of the above circumstances, and its gist is to focus laser light output from a laser light source in order to record and reproduce information. An optical recording / reproducing apparatus of a type in which an optical sensor is used to irradiate the optical recording medium and the signal light from the irradiated portion of the optical recording medium is detected by an optical sensor. An optical fiber for irradiation light transmission that receives and transmits laser light and emits the laser light from the other end surface toward the optical recording medium, and (2) continuously surrounds the other end surface of the irradiation optical transmission optical fiber. And an optical fiber for transmitting signal light, which is configured by a multi-core optical fiber whose one end face is arranged so as to receive the signal light from the irradiation portion of the optical recording medium and guides it to the optical sensor. is there.

With this configuration, the signal light from the optical recording medium passes through the signal light transmission optical fiber that is a multicore optical fiber arranged so as to continuously surround the irradiation light transmission optical fiber. Since it is transmitted to the optical sensor by the optical recording medium, a sufficient amount of reflected light can be incident on the end face of the optical fiber for signal light transmission from the optical recording medium,
It is possible to sufficiently obtain the detection accuracy of the electric signal output from the optical sensor that converts light into an electric signal, that is, the electric signal representing information and the electric signal representing focusing or tracking information. Further, of the reflected light from the optical recording medium, the light that is diffracted light from the pits and guide grooves on the optical recording medium and is used to detect the focusing or tracking signal is directly transmitted through the optical fiber for signal light transmission. Since it can be transmitted to the optical sensor, continuous changes in focusing and tracking signals can be detected.

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 part configuration of an optical head of an optical recording / reproducing apparatus. A laser beam emitted from a semiconductor laser device 10 having a fixed position is incident on an end face of a single irradiation light transmission optical fiber 12. The light is focused on the lens 14 by the lens 15, whereby the irradiation light transmission optical fiber 12 and the semiconductor laser element 10 are optically coupled. The laser light propagating in the irradiation light transmitting optical fiber 12 is diffused from the emitting end face 16,
The light is focused on the recording surface of an optical recording medium (not shown) by the objective lens 18. That is, when reading the information recorded on the optical recording medium or recording the information on the optical recording medium, the desired position of the track formed on the recording surface of the optical recording medium is irradiated with the laser beam spot. .

The reflected light from the optical recording medium is received by the incident-side end face 22 of the large number of reflected light transmitting optical fibers 20 bundled on the outer circumference of the irradiation light transmitting optical fiber 12. The reflected light transmission optical fiber 20 is branched into two bundles, and the light transmitted in the reflected light transmission optical fiber 20 is the information signal detection light whose position is fixed from the emission side end faces 24 and 26 of each bundle. Sensor
28 and the focusing and tracking signal detecting optical sensor 30. In this embodiment, the fiber 20a bundled on the inner peripheral side of the reflected light transmission optical fiber 20 is branched to the optical sensor 28 side, and the fiber 20b bundled on the outer peripheral side is branched to the optical sensor 30 side. There is. Of the reflected light from the optical recording medium, the one that represents the information signal is the light-incident end face 22a of the reflected-light transmitting optical fiber 20a that travels backward in the same optical path as the irradiation light.
Of the reflected light from the optical recording medium used for detecting the focusing or tracking signal is the diffracted light from the pits or the guide grooves on the optical recording medium. Incident side end face 22b
Incident on. By receiving light at a position slightly distant from the focus point by the objective lens 18 toward the outer peripheral side in this way, the influence of the change in the light amount corresponding to the information signal is reduced, and the shift of the focus position in the optical axis direction or from the track is reduced. A change in light amount due to a lateral shift can be easily detected. The optical sensor 28 includes a photodetector element that receives laser light transmitted through the reflected-light transmission optical fiber 20a and converts it into an electrical signal representing information. The optical sensor 30 includes a plurality of photo-detecting elements that receive the laser light transmitted through the reflected-light transmitting optical fiber 20b, convert the laser light into an electrical signal representing focusing or tracking information, and output the electrical signal to the controller 46.

Then, the objective lens 18 is provided in the head movable portion 32 that is driven along the direction intersecting the track of the optical recording medium (not shown), and the end portions of the fibers 12 and 20 are connected, so that the movable portion is small and small. It is said to be lightweight. For example, as shown in FIG. 2, a moving coil 40 is fixed to a movable plate 38 guided by a pair of guide rods 34 and 36 that are fixed in position, and the moving coil 40 has permanent magnets 42 and 44.
The driving force is received by the magnetic field formed by Movable plate
The head movable part 32 is fixed to 38, and the moving coil 40
The head movable portion 32 is positioned and the track is selected by controlling the excitation state of.

The head movable part 32 is provided with a focusing mechanism for moving the objective lens 18 in the optical axis direction and a tracking mechanism for moving the objective lens 18 in the direction perpendicular to the optical axis, and the controller 46 includes the focusing mechanism and the tracking mechanism. By controlling, a laser beam spot of an optimum size is formed on the track of the optical recording medium regardless of the variation of the distance between the optical recording medium and the objective lens 18 and the variation of the track position. . That is, as shown in FIG. 3, the objective lens 18 is attached via a leaf spring 60 to a movable member 58 supported by a leaf spring 56 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 optical recording medium). A magnetic field of a permanent magnet is applied to the focusing coil 62 fixed to the movable member 58, and the objective lens 18 corresponding to the electric current supplied from the controller 46 to the focusing coil 62.
The position in the direction of the optical axis is controlled. Further, the magnetic field of the permanent magnet 68 is also applied to the frame-shaped magnetic member 66 that directly supports the objective lens 18,
The position of the objective lens 18 in the direction perpendicular to the optical axis is controlled in accordance with the current supplied from the tracking coil 72 to the tracking coil 72. The tracking coil 72 is arranged so as to change the magnetic force acting on the magnetic member 66 by the magnetic field of the permanent magnet 68. The end portions of the irradiation light transmission optical fiber 12 and the reflected light transmission optical fiber 20 are fixed in a cylindrical fiber holder 70, and the irradiation light transmission optical fiber 12 substantially coincides with the optical axis of the objective lens 18. As described above, the fiber holder 70 is fixed to the head movable portion 32.

According to the apparatus configured as described above, the light source unit including the semiconductor laser element 10 and the lens 15 and the detection unit including the information signal detecting optical sensor 28 and the focusing or tracking signal detecting optical sensor 30 are fixed in position. The objective portion including the objective lens 18 and the like is provided in the head movable portion 32 which is driven along the recording surface of the optical recording medium in the direction perpendicular to the track. For this reason,
Irradiation light and reflected light are separated from each other as compared with the conventional case in which the light source unit, the detection unit, and the objective unit of the optical head are integrally fixed while maintaining a certain mutual positional accuracy. Therefore, optical components such as a polarization beam splitter and a 1/4 wavelength plate are not required, and the number of components is reduced, so that the optical transmission efficiency of the optical head is increased and the size is reduced. In addition, a laser element 10, a light source unit such as a collimator lens 15,
Since the relative position of the detection unit such as the convex lens, the cylindrical lens, and the optical sensor can be independently arranged relative to the objective unit, the alignment between the light source unit and the detection unit and the objective unit becomes unnecessary, and The high-rigidity frame for maintaining the relative position accuracy is reduced, and the head movable portion 32 is 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, the signal light from the optical recording medium is
Since it is transmitted to the optical sensors 28, 30 via the fiber 20 which is a multi-core optical fiber arranged so as to continuously surround the fiber 12, a sufficient amount of reflected light from the optical recording medium to the end face of the fiber 20 is generated. Sufficient detection accuracy is obtained for the electrical signals that can be incident and output by the optical sensors 28 and 30. Further, of the reflected light from the optical recording medium, the light that is diffracted light from the pits or guide grooves on the optical recording medium and is used for detecting the focusing or tracking signal is directly transmitted to the optical sensor 30 via the fiber 20. Since it can be transmitted, it is possible to detect continuous changes in the focusing and tracking signals.

In addition, in the present embodiment, the head movable portion 32 is configured only by the objective portion, but even if the head movable portion 32 is provided with the light source portion and the detection portion, the temporary effect of the present invention can be enjoyed.

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

The end faces of the fibers 12 and 20 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 fiber 12 is optically recorded. It may be configured as shown in FIGS. 7, 8 and 9 for focusing on medium 76. The apparatus shown in FIG. 7 collimates the laser beam by one convex lens 78 and focuses it on the optical recording medium 76 by the rearward convex lens 80. The apparatus shown in FIG. 8 focuses laser light on the optical recording medium 76 by means of a light focusing waveguide 82 such as a SELFOC lens. In the apparatus shown in FIG. 9, the end face of the irradiation light transmitting optical fiber 12 has a convex shape, and the convex lens action of the convex surface focuses the laser light on the optical recording medium 76.

The reflected light transmission optical fiber 20 may be branched in a fan-shaped cross section with a radial straight line as a boundary, or may be branched randomly, as shown in FIG. Also, the 11th
As shown in the figure, a reflected light transmission optical fiber 20 is formed by using a photodiode array 84 in which a large number of photodetector elements are arranged.
It is also possible to detect the laser light transmitted through the individual fibers constituting the.

Between the optical sensor 28 and the reflected light transmission optical fiber 20a, and between the optical sensor 30 and the reflected light transmission optical fiber 20.
Between b and, as shown in FIG. 12, a convex lens 86 for condensing the laser light on the photodetection element of the optical sensor 28, and a convex lens for condensing the laser light on the photodetection element of the optical sensor 30. Optical components such as 88 and cylindrical lens 90 may be provided respectively.

The fibers 12 and 20 are generally made of quartz, but may be made of plastic and are lightweight. In this case, the head movable portion 32 becomes even lighter. The fibers 12, 20 can also be constructed from polarization-maintaining fibers.
In this case, when the optical recording medium 76 is a magneto-optical disk, the information stored in it can be read out by utilizing the polarization plane of the fiber.

Next, an example of using laser light of two kinds of wavelengths and irradiating laser light to two irradiation places will be described.

In FIG. 13, laser light emitted from semiconductor laser elements 100 and 102 for information recording and information reproduction, which have different wavelengths, are single-core irradiation optical transmission optical fibers 104.
A lens 112 and an incident end surface 108 and 110 of
The light beams are respectively condensed by 114, and thereby the optical fibers 104 and 106 for transmitting the irradiation light and the semiconductor laser devices 100 and 102 are optically coupled. The laser light propagating in the irradiation light transmitting optical fibers 104 and 106 is diffused from the emission side end faces 116 and 118, but is condensed on the recording surface of the optical recording medium by the objective lens 18. That is, when reading the information recorded on the optical recording medium or recording the information on the optical recording medium, as shown in FIG.
A desired position on a track 120 formed on the recording surface of the optical recording medium 76 is irradiated with a laser beam spot 122 for reading information and a laser beam spot 124 for information recording, which have different wavelengths, simultaneously or alternatively. It is.

The reflected light from the optical recording medium is similar to the embodiment of FIG. 1, and the incident side end surface 132 of the plurality of reflected light transmitting optical fibers 130 bundled on the outer circumference of the irradiation light transmitting optical fibers 104 and 106.
Accepted by. Therefore, of the reflected light from the optical recording medium, the reflected light that represents the information signal travels backward in an optical path substantially similar to the irradiation light and is incident on the incident end surface 132a of the reflected light transmitting optical fiber 130a.
Incident on the optical sensor 126 and transmitted to the optical sensor 126, the reflected light from the optical recording medium that is used to detect the focusing or tracking signal is the diffracted light from the pits or guide grooves on the optical recording medium. Therefore, the light sensor 128 is incident on the incident side end surface 132b of the reflected light transmission optical fiber 130b.
Is transmitted to. Optical sensor 126 and optical sensor 128
Are equipped with dichroic mirrors (not shown) and detect only the light of the required wavelength, and output the information signal, the tracking signal, and the focusing signal, respectively.

A fiber holder 70 is fixed to one end of each of the single-core optical fibers 104 and 106 and a multi-core optical fiber 130 bundled on the outer periphery thereof, as in the above embodiment, and the fiber holder 70 is shown in FIG. It is attached to a movable head 32 similar to that shown in. The fiber holder 70 has a flange portion 1 in which an arc-shaped elongated hole 134 is formed as shown in FIG.
It is equipped with 36 and is inserted into the movable head 32 so as to be rotatable about an axis. A screw 138 is fastened to the movable head 32 by penetrating the elongated hole 134 to prevent the fiber holder 70 from coming off and to restrict the rotation around the axis within a certain range. The flange 136 is provided with a protrusion 140 protruding in the outer peripheral direction, and the protrusion 140 is a movable head.
At 32, it is locked while being sandwiched by a pair of positioning screws 142 that are screwed in opposite directions.

According to this embodiment, similarly to the above-described embodiments, the light source unit and the detection unit are provided in fixed positions, and the head movable unit 32 that is the objective unit is movable, so that the movable unit is small. And the inertial weight is reduced, and a polarization beam splitter for separating irradiation light and reflected light, 1 /
The optical transmission efficiency of the optical head is improved because the number of components is reduced by eliminating the need for optical components such as a four-wave plate. In addition, since the relative positional relationship between the light source unit, the detection unit, and the objective unit can be independently arranged, the positional alignment between the light source unit, the detection unit, and the objective unit becomes unnecessary, and the relative position information between the parts is retained. The high-rigidity frame for this purpose is made smaller, the head movable part 32 becomes smaller and lighter and cheaper, and the optical head becomes smaller and lighter, so that the inertial weight becomes smaller and the access time can be greatly shortened.

Further, according to this embodiment, since the rotational position of the fiber holder 70 about the axis is adjusted, the laser beam spot 12
The operation of adjusting the parallelism between the line connecting 2 and 124 and the track 120 can be performed very easily, and since the ends of the irradiation light transmitting optical fibers 104 and 106 are fixed to each other, the laser beam spot 122 There is an advantage that the interval adjustment operations of 124 and 124 are unnecessary.

Further, the signal light from the optical recording medium is transmitted through the fibers 104 and 106.
Since it is transmitted to the optical sensors 28, 30 via the fiber 130 which is a multi-core optical fiber arranged so as to continuously surround the
A sufficient amount of reflected light can be incident on the end face of the fiber 130 from the optical recording medium, and the optical sensor 28, 3 converts the light into an electric signal.
The detection accuracy of the electric signal output at 0 is sufficiently obtained. Further, of the reflected light from the optical recording medium, the light that is diffracted light from the pits or the guide grooves on the optical recording medium and is used for detecting the focusing or tracking signal is directly transmitted to the optical sensor 30 via the fiber 130. Since it can be transmitted, it is possible to detect continuous changes in the focusing and tracking signals.

The end faces of the fibers 104, 106 and 130 have a sixteenth shape.
As shown in FIGS. 17, 17 and 18, it may be a flat surface, a convex surface or a concave surface, and the ends of the irradiation light transmitting optical fibers 104 and 106 may be separated as needed as shown in FIG. Alternatively, as shown in FIG. 20, three or more irradiation light transmission fibers may be provided if necessary. Therefore, on the track 120 of the optical recording medium 76, for example, in the case of three single-core irradiation light transmission optical fibers shown in FIG. 20, three optical fibers are provided as shown in FIG. 21 or FIG. A laser beam spot is formed. In the case of FIG. 22, three laser beam spots are formed on a straight line obliquely intersecting the track 120 for three-beam tracking. In addition, the multiple laser beam spots are located in adjacent tracks as shown in FIG.
One may be formed on each of the 120, or a plurality of laser beam spots may be formed on each of the adjacent tracks 120 as shown in FIG.

Further, in order to focus the laser light emitted from the end faces of the fibers 104 and 106 on the optical recording medium 76, FIG. 25,
It may be configured as shown in FIG. The apparatus shown in FIG. 25 focuses the laser light on the optical recording medium 76 by the light focusing waveguide 144 such as a SELFOC lens. In the apparatus shown in FIG. 26, the end faces of the irradiation light transmitting optical fibers 104 and 106 are formed in a convex shape, and the laser light is focused on the optical recording medium 76 by the convex lens action of the end faces.

In FIG. 13, two semiconductor laser elements 100 and 102 having different wavelengths are used, but these elements may output laser beams having the same wavelength,
As shown in FIG. 27, the laser light output from the single element 146 is divided into optical fibers 10 for transmission of each irradiation light by using the demultiplexer 148.
You may branch to 4,106.

Further, as shown in FIG. 28, an optical fiber for irradiation light transmission
It is also configured by bundling multi-core optical fibers 152 and 154 around 104 and 106, respectively.

The above 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 and FIG. 13 are schematic views respectively showing the constitution of an embodiment of the present invention. FIG. 2 is a perspective view showing a mounting state of the head movable portion of FIG. 1 or 13. FIG. 3 is a sectional view showing the structure of the head movable portion of FIG. FIGS. 4 to 6 and FIGS. 16 to 18 are views showing other examples of the end face shapes of the irradiation light transmitting optical fiber and the reflected light transmitting optical fiber, respectively. FIG. 7 to FIG. 9, FIG. 25, and FIG. 26 are diagrams showing other examples of the configuration for irradiating the 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. 14 is a diagram showing the formation state of the laser beam spot in the embodiment of FIG. FIG. 15 is a perspective view showing a state in which the head movable portion and the optical fiber of FIG. 2 are attached. 19 and 20 are diagrams showing other examples of the optical fiber for transmitting irradiation light. 20 to 24 show the other formation states of the laser beam spot, respectively.
FIG. 14 is a view corresponding to FIG. 14. FIG. 27 is a diagram showing another example of the light source device for transmitting the laser light to the two irradiation light transmitting optical fibers in the embodiment of FIG. FIG. 29 is a schematic diagram showing the structure of an optical head of a conventional optical recording / playback apparatus. 10,100,102: Semiconductor laser device (laser light source) 26: Optical recording medium 20,104,106: Optical fiber for irradiation light transmission 22,130: Optical fiber for reflected light transmission (optical fiber for signal light transmission) 94,150: Single-core optical fiber (optical light for signal light transmission) Fiber) 92,152,154,156: Multi-core optical fiber (optical fiber for signal light transmission) 96,157: Optical fiber for transmitted light transmission (optical fiber for signal light transmission)

Claims (1)

[Claims] 1. In order to record / reproduce information, a laser beam output from a laser light source is focused and irradiated onto an optical recording medium, and a signal light from an irradiated portion of the optical recording medium is detected by an optical sensor. An optical recording / reproducing device of a detection type, which is an irradiation light transmitting light for transmitting and receiving laser light output from the laser light source on one end surface and irradiating the laser light from the other end surface toward the optical recording medium. A fiber and a multicore optical fiber whose one end face is arranged so as to continuously surround the other end face of the irradiation light transmission optical fiber,
An optical recording / reproducing apparatus comprising: an optical fiber for transmitting signal light, which receives the signal light from the irradiation portion of the optical recording medium and guides the signal light to the optical sensor, on one end surface thereof.