JP3971022B2 - Optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc apparatus, and more particularly, to an optical disc apparatus having a movable part equipped with an objective lens for recording / reproducing information.
[0002]
[Problems to be solved by the invention]
In recent years, an optical disc apparatus has been developed in which an objective lens for condensing a light beam on a recording surface of an optical disc is mounted on a movable part that moves linearly along the recording surface of the optical disc. In such an optical disc apparatus, a relatively heavy module such as a light source unit is configured as a fixed optical unit fixed to the optical disc apparatus main body. Since the linear movement direction of the movable part coincides with the direction of the light beam emitted from the fixed optical unit, the light beam emitted from the fixed optical unit reaches the objective lens of the movable part no matter where the movable part moves. .
[0003]
Here, when both surfaces of the optical disk are recording surfaces, it is necessary to provide a pair of movable parts that face both surfaces of the optical disk. At the same time, it is necessary to provide two fixed optical units corresponding to the respective movable parts. However, providing a plurality of relatively complex fixed optical units has a problem that the structure of the entire optical disc apparatus becomes complicated.
[0004]
The present invention has been made in view of the circumstances described above, and aims to simplify the structure of an optical disc apparatus.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, an optical disc apparatus according to the present invention includes (1) a fixed optical unit that includes a light source that emits a light beam and is fixed to the optical disk device, and (2) collects the light beam on both surfaces of the optical disk. First and second carriages that respectively move linearly along both surfaces of the optical disc, and (3) selectively guide the light beam from the fixed optical unit to one of the first and second carriages. Selecting means.
[0006]
With this configuration, since the pair of carriages can share one fixed optical unit, the overall configuration of the optical disc apparatus can be simplified.
[0007]
Said selection means can be comprised by a movable mirror member. In this case, the movable mirror member is provided with two deflection surfaces, and when the movable mirror member is at the first position, the light beam from the fixed optical unit is deflected by the first deflection surface and guided to the first carriage. When the lens is at the second position, the light beam from the fixed optical unit can be deflected by the second deflection surface and guided to the second carriage.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
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 the optical disc apparatus according to the embodiment. The optical disc 2 as a recording medium has recording surfaces on the upper and lower 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 disc 2 is referred to as a “vertical direction”.
[0009]
The optical disc apparatus includes first and second carriages 3a and 3b which are movable parts each having an objective optical system (described later) for condensing a laser beam on the upper and lower surfaces of the optical disc 2, and a main body (not shown) of the optical disc apparatus. It is comprised by the fixed optical unit 4 fixed to. The first and second carriages 3 a and 3 b are configured to move straight along the upper and lower surfaces of the optical disc 2. For simplicity, only the second (lower) carriage 3b is shown in FIG.
[0010]
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 passed through the drive coil 37, the carriage 3b moves straight due to the action of a magnetic field by a magnet (not shown). The position of the second carriage 3b is detected by a positioning sensor 35. Although not shown, the first carriage 3a is also driven by the same linear motor system as the second carriage 3b.
[0011]
First, the optical system mounted on the carriages 3a and 3b will be described.
FIG. 3 is an enlarged view of the tip portion of the first carriage 3a. A floating optical unit 6a including a later-described SIL (solid immersion lens) 11a is provided at the tip of the first carriage 3a. 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. Then, when the optical disk 2 rotates, the flexure beam 8a floats slightly from the surface of the optical disk 2 due to the balance between the air flow caused by the rotation of the optical disk 2 and the elastic force of the flexure beam 8a. Follow.
[0012]
An objective lens 10a is provided at the tip of the first carriage 3a, and a SIL 11a is provided in the floating optical unit 6a. The objective lens 10a and the SIL 11a constitute an objective optical system, and the laser beam incident on the objective lens 10a is condensed on the surface of the optical disc 2.
[0013]
A magnetic coil 12a for recording by the magneto-optical recording method is formed around the SIL 11a, and a magnetic field necessary for recording can be applied to the recording surface of the optical disc 2. The convergent light from the objective lens 10a / SIL 11a and the magnetic coil 12a enable high-density recording and reproduction on the optical disc 2.
[0014]
Since the first carriage 3 a does not follow the surface shake of the optical disc 2, the objective lens 10 a mounted on the first carriage 3 a needs to be controlled to move up and down to follow the surface shake of the optical disc 2. Therefore, the objective lens 10a is attached to 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 passed through the coil 33a, the lens frame 34a moves up and down by the action of the magnetic field generated by the magnet. Note that a detailed description of the movement control of the objective lens 10a is omitted.
The optical system at the tip of the second carriage 3b is configured vertically symmetrically with the optical system at the tip of the first carriage 3a.
[0015]
Next, the fixed optical unit will be described.
As shown in FIG. 1, the fixed optical unit 4 is provided with a light source module 7 and a galvanometer mirror 26. The light source module 7 includes a semiconductor laser 18 that emits a laser beam, a collimator lens 20 that converts divergent light (from the semiconductor laser 18) into parallel light, a composite prism assay 21, an imaging lens 23, a data detection / focus / tracking detection sensor. 24, and an APC sensor 25.
[0016]
The cross-sectional shape of the parallel light beam emitted from the collimating lens 20 is oval due to the characteristics of the semiconductor laser 18, and it is inconvenient to narrow the laser light beam finely on the optical disk 2, so it is necessary to convert it into a substantially circular cross-section. is there. Therefore, the incident surface 21a of the composite prism assay 21 has a predetermined inclination with respect to the incident optical axis, and the cross-sectional shape of the parallel light beam is shaped from an oval shape to a substantially circular shape by refracting the incident light. .
[0017]
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. For tracking control described later, the galvanometer mirror 26 swings about a horizontal swing axis that is also the center axis of the mirror surface, and changes the direction of the laser beam deflected by the galvanometer mirror 26 by a slight angle. Note that description of the configuration for swinging the galvanometer mirror 26 is omitted.
[0018]
In this embodiment, the two carriages 3 a and 3 b are configured to share one fixed optical unit 4. Therefore, as shown in FIG. 2, there is provided a selection mechanism that selectively guides the laser beam from the fixed optical unit 4 to one of the two carriages 3a and 3b.
[0019]
This selection mechanism has a movable prism 50 that can move up and down. The movable prism 50 is a right-angled isometric triangle in a side view, and two surfaces orthogonal to each other are deflection surfaces 51 and 52, respectively. The deflecting surfaces 51 and 52 are inclined by 45 ° with respect to the incident light beam from the galvanometer mirror 26, respectively.
[0020]
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 in the upper position, the incident light beam from the galvanometer mirror 26 enters the lower deflection surface 51 and is deflected vertically downward.
[0021]
Above the movable prism 50, a relay mirror 53 that deflects the laser beam from the deflection surface 51 toward the first carriage 3a is provided. Similarly, a relay mirror 53 that deflects the laser beam from the deflection surface 52 toward the second carriage 3 a is provided below the movable prism 50. Therefore, when the movable prism 50 is in the lower position, the incident light beam from the galvano mirror 26 is guided to the first carriage 3a, and when the movable prism 50 is in the upper position, the incident light beam from the galvano mirror 26 is the second carriage. 3b.
[0022]
The laser light beam guided to the first carriage 3a is reflected downward by the deflection mirror 31a, and is condensed on the upper surface of the optical disc 2 through the objective lens 10a and the SIL 11a. Similarly, the laser beam guided to the second carriage 3b is reflected upward by the deflection mirror 31b, and condensed on the lower surface of the optical disc 2 through the objective lens 10a and the SIL 11a.
[0023]
The return laser beam reflected from the optical disc 2 returns to the light source module 7 in the reverse direction of the forward 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 toward the data detection / focus / tracking detection sensor 24, and separates the laser beam on the return path.
[0024]
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. More precisely, 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 focus error is detected by a known method, the description is omitted.
[0025]
As described above, in the optical disk apparatus according to this embodiment, the movable prism 50 is moved between the upper position and the lower position, so that the laser is selectively applied to either the first carriage 3a or the second carriage 3b. A light beam can be guided.
[0026]
Next, tracking control will be described.
The galvanometer mirror 26 described above performs fine tracking control by finely adjusting the incident angle of the laser beam to the objective lens 10a (10b) by swinging about a predetermined swing axis on the mirror surface. is there. That is, in the optical disc apparatus of the embodiment, an access operation over the inner circumference / outer circumference of the optical disc 2 is performed by the movement of the carriages 3 a and 3 b, and extremely small tracking control is performed by the rotation of the galvano mirror 26. The rotation angle of the galvanometer mirror 26 is detected by an angle detection sensor (not shown) provided in the vicinity of the galvanometer mirror 26.
[0027]
Here, when the galvanometer mirror 26 rotates, the center of the laser beam enters the objective lens 10a (10b) and the center of the beam deviates from the center of the lens. When such a deviation occurs, the amount of light taken into the objective lens 10a (10b) is reduced, so that there is a problem that the amount of light irradiated onto the optical disk is reduced or an offset occurs in the tracking error signal.
Therefore, this optical disc apparatus is configured to make the center of the laser beam coincide with the center of the objective lens 10a (10b) by finely moving the movable prism 50 described above.
[0028]
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, the optical path length from the relay mirror 53 to the deflection surface 51 of the movable prism 50, and from the deflection surface 51 to the galvanometer mirror 26. The total length of the optical path. The total optical path length L changes as the carriage 3a moves.
[0029]
When the galvano mirror 26 rotates counterclockwise in the figure by an angle θ, the emission angle of the laser beam emitted from the galvano mirror 26 changes by 2θ. In this state, when the laser beam advances by the optical path length L and reaches the objective lens 10a, 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, as indicated by a straight line C1 in FIG. (So-called offset occurs).
[0030]
Therefore, in this embodiment, the movable prism 50 is moved to Ltan2θ (based on the rotation angle θ of the galvano mirror 26 detected by the angle detection sensor and the position L of the first carriage 3a detected by the positioning sensor. = H). As a result, the center of the laser beam indicated by the straight line C1 in FIG. 4 is translated as indicated by the straight line C2, and enters the center of the objective lens 10a. Note that the direction in which the movable prism 50 is moved is a direction in which the laser light beam is translated in the direction opposite to the offset, and in this embodiment, is the vertical direction in the figure.
[0031]
Next, a specific example of prevention of offset due to movement of the movable prism will be described. FIG. 5 shows a state where information on the upper surface of the optical disk 2 is being read and written, that is, a state where the laser beam is guided to the first carriage 3a. Here, in order to perform tracking in the outer circumferential direction of the optical disc 2, the galvanometer mirror 26 rotates counterclockwise. In FIG. 5A, the first carriage 3a is on the outer peripheral side of the optical disc 2, and in FIG. 5B, the first carriage 3a is on the inner peripheral side of the optical disc 2.
[0032]
The movable prism 50 is at a lower position for guiding the laser beam to the first carriage 3a, and finely moves up and down according to the rotation angle of the galvano mirror 26 and the position of the first carriage 3a. When the galvanometer mirror 26 rotates counterclockwise, the movable prism 50 moves upward. The amount of movement H of the movable prism 50 follows H = Ltan 2θ, and increases as the first carriage 3 a is located on the inner peripheral side of the optical disc 2.
[0033]
FIG. 6 shows a state where information on the upper surface of the optical disc 2 is being read and written as in FIG. However, in order to perform tracking in the inner peripheral direction of the optical disc 2, the galvanometer mirror 26 rotates clockwise. In FIG. 6A, the first carriage 3a is on the outer peripheral side of the optical disc, and in FIG. 6B, the first carriage 3a is on the inner peripheral side of the optical disc. When the galvanometer mirror 26 is rotating clockwise, the movable prism 50 moves downward. The amount of movement H of the movable prism 50 follows H = Ltan 2θ, and increases as the first carriage 3 a is located on the inner peripheral side of the optical disc 2.
[0034]
FIG. 7 shows a state where information on the lower surface of the optical disk 2 is being read and written, that is, a state where the laser beam is guided to the second carriage 3b. Here, in order to perform tracking in the outer circumferential direction of the optical disc 2, the galvanometer mirror 26 rotates counterclockwise. 7A, the second carriage 3b is on the outer peripheral side of the optical disc 2, and in FIG. 7B, the second carriage 3b is on the inner peripheral side of the optical disc 2.
[0035]
The movable prism 50 is at an upper position for guiding the laser beam to the second carriage 3b, and finely moves up and down depending on the rotation angle of the galvano mirror 26 and the position of the second carriage 3b. When the galvanometer mirror 26 rotates counterclockwise, the movable prism 50 moves upward. The amount of movement H of the movable prism 50 follows H = Ltan 2θ, and increases as the second carriage 3 b is located on the inner peripheral side of the optical disc 2.
[0036]
FIG. 8 shows a state where information on the lower surface of the optical disc 2 is being read and written as in FIG. However, in order to perform tracking in the inner peripheral direction of the optical disc 2, the galvanometer mirror 26 rotates clockwise. 8A, the second carriage 3b is on the outer peripheral side of the optical disc, and in FIG. 8B, the second carriage 3b is on the inner peripheral side of the optical disc. When the galvanometer mirror 26 is rotating clockwise, the movable prism 50 moves downward. The amount of movement H of the movable prism 50 follows H = Ltan 2θ, and increases as the second carriage 3 b is located on the inner peripheral side of the optical disc 2.
[0037]
Thus, according to the optical disk apparatus of this embodiment, since the pair of carriages 3a and 3b can share one fixed optical unit 4, the configuration of the entire optical disk apparatus can be simplified. Further, since the light beam can be selectively guided to one of the first and second carriages 3a and 3b by the movement of the movable mirror 50, the configuration for switching the optical path is simplified.
[0038]
【The invention's effect】
As described above, according to the optical disc apparatus of the present invention, since a pair of carriages can share one fixed optical unit, the configuration of the entire optical disc apparatus can be simplified.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical disc apparatus according to an embodiment.
FIG. 2 is a side sectional view of the optical disc apparatus shown in FIG.
FIG. 3 is an enlarged view showing a front end portion of a carriage.
FIG. 4 is a schematic view showing the principle of offset prevention.
FIG. 5 is a schematic diagram illustrating 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 illustrating a specific example of offset prevention.
FIG. 8 is a schematic diagram illustrating a specific example of offset prevention.
[Explanation of symbols]
2 Optical disks 3a and 3b Carriage 4 Fixed optical unit 7 Light source modules 10a and 10b Objective lenses 11a and 11b SIL (solid immersion lens)
26 Galvano mirror 50 Movable prism 51, 52 Deflection surface 53, 54 Relay mirror

Claims (6)

A fixed optical unit that includes a light source unit that emits a light beam and is fixed to the optical disc device;
First and second carriages each having an objective lens for condensing a light beam on both sides of the optical disc, each moving linearly along both sides of the optical disc;
Selecting means for selectively guiding a light beam from the fixed optical unit to one of the first and second carriages;
The fixed optical unit has a galvanometer mirror, and the light incident on the objective lens of the carriage selected by the selection means by swinging the galvanometer mirror about a predetermined axis on the mirror surface. Fine-tune the incident angle of the beam,
The selection means is a movable mirror member having a deflecting surface for deflecting the light beam from the fixed optical unit and configured to be movable, and is incident on the objective lens regardless of the oscillation of the galvanometer mirror. An optical disc apparatus comprising: a movable mirror member configured to move in accordance with the swing of the galvano mirror so that the center of the light beam coincides with the center of the objective lens.   The optical disk apparatus 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. The movable mirror member moves based on the rotation angle of the galvanometer mirror and the distance between the galvanometer mirror and the objective lens provided on the carriage, which is determined by the position of the carriage selected by the selection means. 3. The optical disc apparatus according to claim 1, wherein the optical disc apparatus is configured as described above. The movable mirror member has at least two deflection surfaces;
When the movable mirror member is in the first position, the light beam from the fixed optical unit is deflected by the first deflection surface;
4. The optical disc apparatus according to claim 1, wherein when the movable mirror member is at the second position, the light beam from the fixed optical unit is deflected by the second deflection surface. The selection means includes a first relay mirror for guiding a light beam from the first deflection surface of the movable mirror member to a first carriage;
A second relay mirror for guiding a light beam from the second deflection surface of the movable mirror member to a second carriage;
The optical disc apparatus according to claim 4, further comprising:   6. The optical disc apparatus according to claim 1, wherein the selection unit emits a light beam incident on the selection unit from the fixed optical unit in parallel with the light beam and shifted in position. .

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