JPH11328700A - Optical disk drive - Google Patents

Abstract

(57) [Problem] To make an incident position of a light beam to an objective lens constant in an optical disk device. A deflection mirror (5) is provided in accordance with a rotation angle of a galvanometer mirror (26) and a position of a carriage (3a, 3b).
0) is moved to offset the shift of the light beam incident on the objective lenses (10a, 10b) due to the rotation of the galvanomirror.

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.

[0002]

In recent years, the areal recording density has become 1
Optical disk devices exceeding 0 Gbit / (inch) ² are being developed. In such an optical disk device, an objective lens for condensing a light beam on a recording surface of the optical disk is provided in a movable portion that moves in a direction intersecting a track of the optical disk, and the movable portion moves to access the inner circumference / outer circumference of the optical disk. It is configured to perform an operation. Furthermore, fine movement tracking is performed by finely adjusting the angle of incidence of the light beam on the objective lens by a deflecting unit such as a galvanometer mirror.

However, as shown in FIGS. 9A and 9B, when the incident angle of the light beam to the objective lens 500 is changed by a deflecting means (not shown) such as a galvanometer mirror, the light beam to the objective lens 500 is changed. Also changes the incident position. Therefore, a part of the light beam that should enter the objective lens 500 is blocked by an obstacle or a stop (indicated by A in the figure) existing around the objective lens 500.

When such a phenomenon (so-called vignetting) occurs, as shown in FIG. 9B, the intensity D of the light reaching the recording surface of the optical disk is reduced, so that fine tracking may not be performed normally. There is. Therefore, it has been desired to make the incident position of the light beam on the objective lens constant during the fine movement tracking.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to make an incident position of a light beam on an objective lens constant during fine movement tracking in an optical disk device.

[0006]

In order to solve the above-mentioned problems, an optical disk apparatus according to the present invention moves a deflecting mirror according to the rotation angle of a galvanomirror and the position of a carriage, so that the light beam from the galvanomirror is changed. , (Irrespective of the rotation angle of the galvanometer mirror), the light is incident on the same position of the objective lens. With this configuration, it is possible to prevent a part of the light beam to be incident on the objective lens from being blocked (vignetting) by the peripheral members.
Therefore, it is possible to prevent the light intensity of the light beam reaching the optical disk from decreasing, and it is possible to always perform fine movement tracking normally.

The direction of movement of the deflecting mirror is substantially parallel to the light beam incident on the galvanometer mirror. Further, assuming that the rotation angle of the galvanometer mirror is θ and the distance from the rotation axis of the galvanometer mirror to the objective optical system is L, the movement amount H of the deflection mirror is H = L · tan (2θ).

Further, the optical disk of the present invention can be applied to an optical disk apparatus in which two sets of objective lenses for condensing a light beam on each surface of the optical disk are mounted on first and second carriages. In this case, the light source unit is configured as a fixed optical unit fixed to the optical disk device main body. Further, the above-mentioned deflection mirror may be configured as a movable mirror driven to guide the light beam from the fixed optical unit to one of the first and second carriages.

[0009]

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, the direction perpendicular to the surface of the optical disk 2 is referred to as “vertical direction”, and the direction along the surface of the optical disk 2 is referred to as “horizontal direction”.

The optical disk apparatus comprises first and second carriages 3a, 3 which are movable parts having an objective optical system (described later) for focusing a laser beam 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 voice coil motor system. As shown in FIG.
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. Also, the second
The position of the carriage 3b is detected by a positioning sensor 35. Although not shown, the first carriage 3a
Is also driven by the same voice coil motor system as the second 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.
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
Due to the convergent light from L11a and the magnetic coil 12a, high-density recording / reproduction on the optical disk 2 becomes possible.

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 down the laser light beam onto the optical disk 2. 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 galvanometer mirror 26. The galvanomirror 26 oscillates about a horizontal oscillating axis which is also the center axis of the mirror surface (by a mirror rotating mechanism 28 shown by a block in FIG. 2) for fine movement tracking control described later, and changes the direction of the laser beam. Change the angle slightly.

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 triangular prism having a right-angled isosceles triangle in a side view, and two surfaces orthogonal to each other are deflecting surfaces 51 and 52, respectively. Deflection surfaces 51, 5
2 are inclined by 45 ° in the horizontal direction (that is, with respect to the incident light beam from the galvanometer mirror 26).

The movable prism 50 is driven up and down by a drive mechanism 29 shown by a block in FIG. When the movable prism 50 is at the lower position, the incident light beam from the galvanomirror 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 deflecting surface 51 and is deflected vertically downward.

Above the movable prism 50, a deflection 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 return laser beam reflected from the optical disk 2 and returned returns to the light source module 7 in a direction opposite to the outward path, 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 disc 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. That is, only one fixed optical unit 4 is required. Therefore, the overall configuration of the apparatus is simpler than that of an optical disk apparatus having a plurality of fixed optical devices 4 (as many as the number of carriages).

Next, 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 (indicated by reference numeral 27 in FIG. 2) provided near the galvanometer mirror 26.

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 10a, as shown by the straight line C1 in FIG.

When the incident position of the laser beam on the objective lens shifts, a part of the laser beam to be incident on the objective lens is blocked by members around the objective lens as shown in FIG. There is a problem that the light intensity on the surface is reduced. In order to solve such a problem, the optical disk device of this embodiment is configured to finely move the movable prism 50 so as to cancel a change in the incident position of the light beam to the objective lens due to the rotation of the galvanometer mirror 26. I have.

That is, in this embodiment, the movable prism 5 is controlled based on the rotation angle θ of the galvanometer mirror 26 detected by the above-described angle detection sensor and the position L of the first carriage 3a detected by the above-described positioning sensor.
0 is moved by Ltan2θ (= H). Thereby, the center of the laser beam shown by the straight line C1 in FIG. 4 is translated as shown by the straight line C2,
The light enters the center of the objective lens 10a. The direction in which the movable prism 50 is moved is a direction that cancels a change in the incident position of the laser beam (to the objective lens) due to the rotation of the galvanomirror 26, and is a vertical direction in FIG.

With this configuration, the galvanomirror 2
The light beam from 6 enters the same position of the objective lens 10a (10b) regardless of the rotation angle of the galvanometer mirror 26.

Hereinafter, a specific configuration for making the incident position of the laser beam on the objective lens 10a (10b) constant 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. FIG. 5 (A)
In FIG. 5, 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 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 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 the second carriage 3b is on the inner peripheral side of the optical disk 2 in FIG.

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 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, by moving the movable mirror 50 according to the rotation angle of the galvanometer mirror 26 and the position of the first carriage 3a (or the second carriage 3b), the laser beam is Can be made incident on the same position of the objective lens 10a (10b). That is, the laser beam to be incident on the objective lens 10a (10b) is not blocked by the peripheral members. With this configuration, it is possible to prevent a decrease in the light intensity of the laser beam reaching the optical disk, so that fine movement tracking can always be normally performed.

In the above embodiment, the movable prism 5
0 is moved in a direction substantially parallel to the direction of incidence of the laser beam on the galvanometer mirror 26 (the vertical direction in FIG. 4).
The laser beam may be moved in a direction substantially parallel to the emission direction of the laser beam from the galvanometer mirror 26 (the left-right direction in FIG. 4). Also, relay mirrors 53 and 54 are used instead of the movable prism 50.
Can also be moved.

[0041]

As described above, according to the optical disk apparatus of the present invention, it is possible to prevent a part of the light beam to be incident on the objective lens from being blocked by peripheral members (so-called vignetting). For this reason, it is possible to prevent the light intensity of the light beam reaching the optical disk from decreasing, so that fine movement tracking can always be normally performed.

[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 a principle of making a light beam incident position on an objective lens constant.

FIG. 5 is a schematic diagram showing a configuration for keeping a light beam incident position on an objective lens constant.

FIG. 6 is a schematic diagram showing a configuration for making a light flux incident position on an objective lens constant.

FIG. 7 is a schematic diagram showing a configuration for making a light beam incident position on an objective lens constant.

FIG. 8 is a schematic diagram showing a configuration for making a light flux incident position on an objective lens constant.

FIG. 9 is a schematic diagram showing a problem of the related art.

[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 (5)

[Claims] 1. An optical disk device for causing a light beam emitted from a light source unit to enter an objective lens via a galvanometer mirror and a deflecting mirror and condensing the objective lens on an optical disk surface, wherein the objective lens is a recording surface of the optical disk. Mounted on a carriage that moves along the axis, and configured to rotate the galvanometer mirror about a predetermined rotation axis on the mirror surface to finely adjust the incident angle of the light beam incident on the objective lens. In the above, by moving the deflecting mirror according to the rotation angle of the galvanometer mirror and the position of the carriage, the light flux from the galvanometer mirror is placed at the same position of the objective lens regardless of the rotation angle of the galvanometer mirror. An optical disk device characterized by being configured to be incident. 2. The optical disk device according to claim 1, wherein a direction of movement of the deflecting mirror is substantially parallel to a light beam incident on the galvanomirror. 3. Assuming that the rotation angle of the galvanomirror is θ and the distance from the rotation axis of the galvanomirror to the objective lens is L, the moving amount H of the deflecting mirror is H = Ltan (2θ). The optical disk device according to claim 1, wherein: 4. An optical disk having first and second carriages which respectively move linearly along both surfaces of an optical disk, and comprising two sets of objective lenses for converging a light beam on each surface of the optical disk.
In the optical disk device mounted on the carriage, the light source unit is fixed to the optical disk device body,
The deflecting mirror is configured as a fixed optical unit independent of the first and second carriages, and is driven to guide a light beam from the fixed optical unit to one of the first and second carriages. The optical disk device according to any one of claims 1 to 3, wherein the optical disk device is a movable mirror. 5. An optical disk device for causing a light beam emitted from a light source unit to enter an objective lens via a galvanomirror and a deflecting mirror and to condense it on an optical disk surface, wherein the galvanomirror is mounted on the mirror surface. In a configuration in which the light beam is rotated about a predetermined rotation axis to finely adjust the incident angle of the light beam incident on the objective lens, a change in the incident position of the light beam to the objective lens due to the rotation of the galvanometer mirror is offset. An optical disk device configured to move the deflection mirror so as to move the deflection mirror.