JPH11265517A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable one pair of carriages to share one fixed optical unit by selectively guiding a luminous flux from the fixed optical unit to either of two carriages. SOLUTION: A selecting mechanism selectively guiding a laser luminous flux from a fixed optical unit 4 to either of two carriages 3a, 3b has a movable prism 50 movable in up and down and this prism 50 is a right-angled isosceles triangle when it is seen from the side face and two planes orthogonally crossing with each other respectively become deflection planes 51, 52. Both planes 51, 52 are respectively inclined by 45 deg. with respect to an incident luminous flux from a galvanomirror 26. When this movable prism 50 is placed at the lower side, the incident luminous flux from the galvanomirror 26 is made incident on the deflection plane 51 of the upper side to be deflected to a vertically upper direction. On the other hand, when it is placed at the side of an upper side, the incident luminous flux is made incident on the deflection plane 52 of the lower side to be deflected to a vertically down direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly, to an optical disk device having a movable portion on which an objective lens for recording and reproducing information is mounted.

[0002]

In recent years, there has been developed an optical disk device in which an objective lens for condensing a light beam on a recording surface of an optical disk is mounted on a movable portion that moves linearly along the recording surface of the optical disk. In such an optical disk device, a relatively heavy module such as a light source unit is
It is configured as a fixed optical unit fixed to the optical disk device main body. Since the moving direction of the movable unit is in the same direction as the direction of the light beam emitted from the fixed optical unit, the emitted light beam from the fixed optical unit reaches the objective lens of the movable unit no matter where the movable unit moves. .

Here, when both sides of the optical disk are recording surfaces, it is necessary to provide a pair of movable parts facing each other on both sides of the optical disk. At the same time, it is necessary to provide two fixed optical units corresponding to each movable part. However, if a plurality of fixed optical units having a relatively complicated configuration are provided, there is a problem that the structure of the entire optical disk device becomes complicated.

The present invention has been made in view of the above circumstances, and has as its object to simplify the structure of an optical disk device.

[0005]

In order to solve the above problems, an optical disk device according to the present invention comprises: (1) a fixed optical unit having a light source unit for emitting a light beam and fixed to the optical disk device; A) first and second carriages each having an objective lens for condensing a light beam on both sides of the optical disc, and moving linearly along both sides of the optical disc;
(3) selecting means for selectively guiding the light beam from the fixed optical unit to one of the first and second carriages.

With this configuration, the pair of carriages can share one fixed optical unit, so that the overall configuration of the optical disk device can be simplified.

The above-mentioned selecting means can be constituted by a movable mirror member. In this case, the movable mirror member is provided with two deflecting surfaces, and when the movable mirror member is at the first position, the light flux from the fixed optical unit is deflected by the first deflecting surface and guided to the first carriage, When is located at the second position, the light beam from the fixed optical unit can be deflected by the second deflecting surface and guided to the second carriage.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the present invention will be described. 1 and 2 are a perspective view and a side sectional view showing a schematic configuration of an optical disk device according to an embodiment. The optical disc 2 as a recording medium has upper and lower surfaces serving as recording surfaces, and is mounted on a rotating shaft 22 of a spindle motor. In the following description, a direction perpendicular to the surface of the optical disk 2 is referred to as a “vertical direction”.

The optical disk device comprises first and second carriages 3a, 3 which are movable parts having objective optical systems (described later) for converging laser light beams on the upper and lower surfaces of the optical disk 2, respectively.
b, and a fixed optical unit 4 fixed to a main body (not shown) of the optical disk device. The first and second carriages 3a, 3b are configured to move straight along the upper and lower surfaces of the optical disc 2. For simplicity, FIG. 1 shows only the second (lower) carriage 3b.

The first and second carriages 3a and 3b are driven by a linear motor system. As shown in FIG. 1, a driving coil 37 is attached to the second carriage 3b, and a magnet (not shown) is provided around the second carriage 3b. When a current is applied to the drive coil 37, the carriage 3b moves straight by the action of a magnet (not shown) with a magnetic field. The position of the second carriage 3b is detected by the positioning sensor 35. Although not shown, the first carriage 3a is also a second carriage.
It is driven by the same linear motor system as the carriage 3b.

First, an optical system mounted on the carriages 3a and 3b will be described. FIG. 3 shows the first carriage 3a.
FIG. 4 is an enlarged view of a tip portion of FIG. First carriage 3a
A floating optical unit 6a including a later-described SIL (solid immersion lens) 11a is provided at the front end of the lens. The floating optical unit 6a is attached to one end of the flexure beam 8a, and the other end of the flexure beam 8a is fixed to the lower surface of the first carriage 3a. When the optical disk 2 rotates, the flexure beam 8a is moved by the balance between the airflow due to the rotation of the optical disk 2 and the elastic force of the flexure beam 8a.
The optical disk 2 follows the surface runout of the optical disk 2 while floating slightly from the surface of the optical disk 2.

An objective lens 10a is provided at the tip of the first carriage 3a, and the floating optical unit 6a has an SI.
L11a is provided. This objective lens 10a and S
The IL 11a constitutes an objective optical system, and the objective lens 1
The laser beam incident on Oa is focused on the surface of the optical disk 2.

A magnetic coil 12a for recording by magneto-optical recording is formed around the SIL 11a so that a required magnetic field can be applied to the recording surface of the optical disk 2 at the time of recording. Objective lens 10a SI
The converged light from L11a and the magnetic coil 12a enable high-density recording and reproduction on the optical disk 2.

Since the first carriage 3a does not follow the surface deviation of the optical disk 2, the objective lens 10a mounted on the first carriage 3a needs to be controlled to move up and down so as to follow the surface deviation of the optical disk 2. Therefore, the objective lens 10a is mounted on a lens frame 34a with a magnet, and the first carriage 3a is provided with a coil 33a surrounding the lens frame 34a. When a current is applied to the coil 33a, the lens frame 34
a moves up and down. The description of the details of the movement control of the objective lens 10a is omitted. Second carriage 3
The optical system at the distal end of b is vertically symmetrical to the optical system at the distal end of the first carriage 3a.

Next, the fixed optical unit will be described. As shown in FIG. 1, the fixed optical unit 4 includes a light source module 7 and a galvanomirror 26.
The light source module 7 includes a semiconductor laser 18 that emits a laser beam, a collimating lens 20 that converts divergent light (from the semiconductor laser 18) into parallel light, a complex prism assay 21, an imaging lens 23, data detection / focus /
It has a tracking detection sensor 24 and an APC sensor 25.

The cross-sectional shape of the parallel light beam emitted from the collimating lens 20 is an elliptical shape due to the characteristics of the semiconductor laser 18, and it is inconvenient to narrow the laser light beam onto the optical disc 2 minutely, so that the light beam is converted into a substantially circular cross-section. There is a need to. For this reason, the entrance surface 21 of the composite prism assay 21
“a” has a predetermined inclination with respect to the incident optical axis, and refracts the incident light to shape the cross-sectional shape of the parallel light beam from an oval shape to a substantially circular shape.

The laser beam emitted horizontally from the light source module 7 is deflected vertically upward by the deflection mirror 27 behind the light source module 7 and enters the galvanomirror 26. For tracking control to be described later, the galvanomirror 26 swings around a horizontal swing axis which is also the center axis of the mirror surface, and changes the direction of the laser beam deflected by the galvanomirror 26 by a small angle.
The description of the configuration for swinging the galvanometer mirror 26 is omitted.

In this embodiment, two carriages 3
a and 3b are configured to share one fixed optical unit 4. Therefore, as shown in FIG. 2, the laser beam from the fixed optical unit 4 is
There is provided a selection mechanism for selectively leading to any one of a and 3b.

This selection mechanism has a movable prism 50 that can move up and down. The movable prism 50 is a right-angled isosceles triangle in side view, and two surfaces orthogonal to each other are deflecting surfaces 51 and 52, respectively. The deflecting surfaces 51 and 52 are each inclined by 45 ° with respect to the incident light beam from the galvanometer mirror 26.

When the movable prism 50 is at the lower position shown in FIG. 2, the incident light beam from the galvanometer mirror 26 enters the upper deflection surface 51 and is deflected vertically upward. on the other hand,
When the movable prism 50 is at the upper position, the incident light beam from the galvanomirror 26 enters the lower deflection surface 51,
It is deflected vertically downward.

Above the movable prism 50, a deflecting surface 51 is provided.
There is provided a relay mirror 53 for deflecting the laser beam from the first carriage 3a toward the first carriage 3a. Similarly, below the movable prism 50, a relay mirror 53 that deflects the laser beam from the deflection surface 52 toward the second carriage 3a.
Is provided. Therefore, when the movable prism 50 is at the lower position, the incident light beam from the galvanomirror 26 is guided to the first carriage 3a. 3b.

The laser beam guided to the first carriage 3a is reflected downward by the deflecting mirror 31a, and is condensed on the upper surface of the optical disk 2 via the objective lens 10a and the SIL 11a. Similarly, the laser beam guided to the second carriage 3b is reflected upward by the deflecting mirror 31b, and is condensed on the lower surface of the optical disk 2 via the objective lens 10a and the SIL 11a.

The returning laser beam reflected from the optical disk 2 returns in the reverse direction to the outward path, returns to the light source module 7, and enters the composite prism assay 21. The half mirror surface 21b of the composite prism assay 21 generates transmitted light and reflected light directed to the data detection / focus / tracking detection sensor 24, and separates the laser beam on the return path.

The data detection / focus / tracking detection sensor 24 is a composite sensor that reads data information recorded on the optical disk 2 and outputs a data signal, and outputs a focus and tracking error signal. To be precise, the focus / tracking error signal and the data signal are generated by a head amplifier circuit (not shown) and sent to a control circuit or an information processing circuit. Since the detection of the focus error is performed by a known method, the description is omitted.

As described above, in the optical disk device of this embodiment, the first carriage 3 is moved by moving the movable prism 50 between the upper position and the lower position.
a and the second carriage 3b can selectively guide the laser beam.

Next, the tracking control will be described. The above-described galvanometer mirror 26 swings around a predetermined swing axis on the mirror surface, thereby moving the objective lens 1.
The fine tracking control is performed by finely adjusting the incident angle of the laser beam with respect to 0a (10b). That is,
In the optical disk device of the embodiment, the carriages 3a, 3b
The access operation is performed over the inner circumference / outer circumference of the optical disk 2 by the movement of the optical disk 2, and the minute tracking control is performed by the rotation of the galvanometer mirror 26. The rotation angle of the galvanometer mirror 26 is detected by an angle detection sensor (not shown) provided near the galvanometer mirror 26.

Here, when the galvanomirror 26 rotates, the center of the laser beam is focused on the objective lens 10a (10b).
Is shifted from the center of the lens.
When such a shift occurs, the objective lens 10a (10
Since the amount of light taken in b) is reduced, there is a problem that the amount of light irradiated on the optical disk is reduced, and the tracking error signal is offset. Therefore, this optical disk device is provided with the movable prism 50 described above.
Is slightly moved up and down so that the center of the laser beam coincides with the center of the objective lens 10a (10b).

FIG. 4 is a schematic diagram showing an optical path from the galvanometer mirror 26 to the objective lens 10a of the first carriage 3a. The total optical path length indicated by L in the figure is the optical path length from the objective lens 10a to the center of the relay mirror 53 and the relay mirror 5
3 to the deflection surface 51 of the movable prism 50;
The length is the sum of the optical path lengths from the deflecting surface 51 to the galvanometer mirror 26. The total optical path length L changes with the movement of the carriage 3a.

When the galvanomirror 26 is rotated counterclockwise in the figure by the angle θ, the emission angle of the laser beam emitted from the galvanomirror 26 changes by 2θ. In this state, the laser beam advances by the optical path length L and the objective lens 1
When reaching 0a, the center of the intensity distribution of the laser beam is shifted upward by Ltan2θ with respect to the optical axis of the objective lens (a so-called offset occurs), as indicated by the straight line C1 in FIG.

Therefore, in this embodiment, the movable prism 50 is determined based on the rotation angle θ of the galvanometer mirror 26 detected by the angle detection sensor and the position L of the first carriage 3a detected by the positioning sensor. Are moved by Ltan2θ (= H). Thereby, the center of the laser beam shown by the straight line C1 in FIG. 4 is translated in parallel as shown by the straight line C2, and is incident on the center of the objective lens 10a. The direction in which the movable prism 50 is moved is a direction in which the laser beam is translated in a direction opposite to the offset, and is a vertical direction in the drawing in this embodiment.

Next, a specific example of prevention of offset due to movement of the movable prism will be described. FIG. 5 shows a state in which information on the upper surface of the optical disk 2 is being read / written, that is, a state in which a laser beam is guided to the first carriage 3a. Here, in order to perform tracking in the outer peripheral direction of the optical disc 2, the galvanometer mirror 26 is rotating counterclockwise. In FIG. 5A, the first carriage 3a is on the outer peripheral side of the optical disk 2, and in FIG. 5B, the first carriage 3a is on the inner peripheral side of the optical disk 2.

The movable prism 50 transmits the laser beam to the first
It is at a lower position for guiding to the carriage 3a, and from that position, the rotation angle of the galvanometer mirror 26 and the first carriage 3a
Finely move up and down according to the position of. When the galvanomirror 26 is rotating counterclockwise, the movable prism 50 moves upward. The moving amount H of the movable prism 50 is H = L.
In accordance with tan2θ, the first carriage 3a
It becomes larger as it is closer to the inner circumference.

FIG. 6 shows a state in which information on the upper surface of the optical disk 2 is being read and written, similarly to FIG. However, to perform tracking in the inner circumferential direction of the optical disc 2, the galvanomirror 26 rotates clockwise. In FIG. 6A, the first carriage 3a is on the outer peripheral side of the optical disc,
In FIG. 6B, the first carriage 3a is located on the inner side of the optical disk. When the galvanomirror 26 is rotating clockwise, the movable prism 50 moves downward. The moving amount H of the movable prism 50 follows H = Ltan2θ, and increases as the first carriage 3a is closer to the inner circumference of the optical disk 2.

FIG. 7 shows a state in which information on the lower surface of the optical disk 2 is being read / written, that is, a state in which a laser beam is guided to the second carriage 3b. Here, in order to perform tracking in the outer peripheral direction of the optical disc 2, the galvanometer mirror 26 is rotating counterclockwise. In FIG. 7A,
The second carriage 3b is on the outer peripheral side of the optical disk 2, and in FIG. 7B, the second carriage 3b is on the inner peripheral side of the optical disk 2.

The movable prism 50 transmits the laser beam to the second
It is located at an upper position for guiding to the carriage 3b, from which the rotation angle of the galvanometer mirror 26 and the second carriage 3b
Finely move up and down according to the position of. When the galvanomirror 26 is rotating counterclockwise, the movable prism 50 moves upward. The moving amount H of the movable prism 50 is H = L.
According to tan2θ, the second carriage 3b is
It becomes larger as it is closer to the inner circumference.

FIG. 8 shows a state in which information on the lower surface of the optical disk 2 is being read and written, similarly to FIG. However, to perform tracking in the inner circumferential direction of the optical disc 2, the galvanomirror 26 rotates clockwise. In FIG. 8A, the second carriage 3b is on the outer peripheral side of the optical disc,
In FIG. 8B, the second carriage 3b is located on the inner circumference side of the optical disc. When the galvanomirror 26 is rotating clockwise, the movable prism 50 moves downward. The moving amount H of the movable prism 50 follows H = Ltan2θ, and increases as the second carriage 3b is closer to the inner circumference of the optical disc 2.

As described above, according to the optical disk device of this embodiment, the pair of carriages 3a and 3b can share one fixed optical unit 4, so that the configuration of the entire optical disk device can be simplified. The movement of the movable mirror 50 causes the first and second carriages 3 to move.
Since the luminous flux can be selectively guided to any of a and 3b, the configuration for switching the optical path is also simplified.

[0038]

As described above, according to the optical disk apparatus of the present invention, a pair of carriages can share one fixed optical unit, so that the configuration of the entire optical disk apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical disk device of an embodiment.

FIG. 2 is a side sectional view of the optical disk device in FIG.

FIG. 3 is an enlarged view showing a leading end portion of a carriage.

FIG. 4 is a schematic diagram showing the principle of offset prevention.

FIG. 5 is a schematic diagram showing a specific example of offset prevention.

FIG. 6 is a schematic diagram showing a specific example of offset prevention.

FIG. 7 is a schematic diagram showing a specific example of offset prevention.

FIG. 8 is a schematic diagram showing a specific example of offset prevention.

[Explanation of symbols]

2 Optical Disk 3a, 3b Carriage 4 Fixed Optical Unit 7 Light Source Module 10a, 10b Objective Lens 11a, 11b SIL (Solid Immersion Lens) 26 Galvano Mirror 50 Movable Prism 51, 52 Deflection Surface 53, 54 Relay Mirror

Claims (8)

[Claims] A light source unit for emitting a light beam; a fixed optical unit fixed to the optical disk device; and an objective lens for condensing the light beam on both surfaces of the optical disk. An optical disc device comprising: first and second carriages respectively moving straight; and selecting means for selectively guiding a light beam from the fixed optical unit to one of the first and second carriages. 2. The optical disk device for an optical disk according to claim 1, wherein the fixed optical unit further includes a light receiving unit that receives a light beam reflected from a recording surface of the optical disk. 3. The fixed optical unit has a galvanomirror, and swings the galvanomirror about a predetermined axis on a mirror surface of the galvanomirror, so that the objective of the carriage selected by the selecting means is provided. The optical disk device according to claim 1, wherein an incident angle of the light beam incident on the lens is finely adjusted. 4. The apparatus according to claim 1, wherein said selecting means includes a movable mirror member having a deflecting surface for deflecting a light beam from said fixed optical unit and movable. An optical disc device according to any one of the above. 5. The movable mirror member has at least two deflecting surfaces, and deflects a light beam from the fixed optical unit by the first deflecting surface when the movable mirror member is at a first position. The optical disk device according to claim 4, wherein when the mirror member is at the second position, the light beam from the fixed optical unit is deflected by a second deflection surface. 6. A first carriage for guiding a light beam from the first deflecting surface of the movable mirror member to a first carriage.
6. The optical disk device according to claim 5, further comprising: a relay mirror, and a second relay mirror for guiding a light beam from the second deflection surface of the movable mirror member to a second carriage. . 7. The apparatus according to claim 1, wherein said selecting means emits a light beam incident on said selecting means from said fixed optical unit in parallel with said light beam and shifted in position. An optical disk device according to claim 1. 8. The apparatus according to claim 1, wherein the directions of the light beams guided from said selecting means to said first and second carriages are substantially parallel to the moving directions of said first and second carriages. 8. The optical disk device according to any one of items 1 to 7,