JP2001319349A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the optical axis shift of an objective lens to an incident optical axis and to perform tracking and tilt compensation simultaneously. SOLUTION: Supporting wires 8a, 8b (8c, 8d) are arranged in roughly a chevron-shape on a plane (xy plane of projection) parallel to the recording face of a recording disk. As these supporting wires 8a, 8b (8c, 8d) warp, the holder 5 rotates on which the objective lens 1 and a deflecting mirror 3 are fixed, with the intersection on the extension of each supporting wire 8a, 8b (8c, 8d) as a reference 11 of rotation. As the holder 5 is rotated, the positions of the objective lens 1 and the deflecting mirror 3 shift in the x direction, thereby making it possible to perform, through the rotation of the holder 5, the tracking by the displacement of the objective lens 1 and the coma-aberration compensation by the change in the incident angle of the objective lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical pickup device mounted on a disk drive for recording / reproducing on / from an optical disk.

[0002]

2. Description of the Related Art As in an apparatus described in Japanese Patent Application Laid-Open No. 10-228653, a movable portion of an objective lens actuator is configured to be inclined with movement in a tracking direction to change the center of a tracking operation amplitude. There is known an optical disc which can correct coma aberration of a light spot on an optical disc.

[0003]

In the structure of the conventional apparatus, the moving range of the objective lens actuator in the tracking direction becomes large, and the optical axis shift of the objective lens with respect to the incident optical axis becomes large. The diameter of the light beam going to the objective lens needs to be larger than the lens diameter by the amount of the optical axis shift. Therefore, an increase in the optical axis shift leads to a decrease in the amount of light incident on the lens because the diameter of the light beam increases. .

Further, the position of a light spot on a photodetector that receives reflected light from an optical disk also shifts in accordance with the shift of the optical axis, causing an error in a tracking error signal and the like. This leads to an increase in error.

An object of the present invention is to provide an optical pickup device which solves the above-mentioned conventional problems, suppresses the optical axis shift of the objective lens with respect to the incident optical axis, and enables simultaneous tracking and tilt correction. Is to do.

[0006]

According to a first aspect of the present invention, a light emitted from a light source to an inside of a plane substantially parallel to the optical disk is reflected by the rising mirror on the surface of the optical disk. In an optical pickup device which deflects light in the direction and collects the deflected light as a light spot on the surface of the optical disk by an objective lens, an optical axis of the light incident on the rising mirror in a tracking direction of the light spot. A deflection mirror that is set substantially perpendicular to the light source and deflects light inward from a plane substantially parallel to the optical disc between the light source and the rising mirror; and the deflection mirror is integrated with the objective lens and the optical disc. The objective lens and the deflecting mirror are freely rotatable as a unit, with the objective lens and the deflecting mirror being rotatable about a rotation reference perpendicular to a plane substantially parallel to the object. Since supporting, it is possible to perform a coma correction by tracking the objective lens incident angle changes by the objective lens displaced by rotation alone.

According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the objective lens is a lens that does not satisfy a sine condition. Can be set arbitrarily, and coma aberration can be corrected more effectively.

According to a third aspect of the present invention, in the optical pickup device of the first aspect, the distance from the objective lens to the rotation reference is longer than the distance from the objective lens to the deflection mirror. With this configuration, it is possible to further reduce the optical axis shift that occurs when the objective lens is displaced.

According to a fourth aspect of the present invention, in the optical pickup device according to the third aspect, when the tracking amplitude is t and the allowable variation of the light incident angle in the objective lens is θ radian, the optical pickup device rotates from the objective lens. The distance L ₁ to the reference satisfies L ₁ ≧ 2 × t / θ. With this configuration, the distance from the objective lens to the rotation axis is sufficiently long, so that coma aberration fluctuation due to tracking falls within an allowable value. Fits.

According to a fifth aspect of the present invention, in the optical pickup device according to the first aspect, the objective lens and the deflecting mirror are provided on the same holder, and the holder is at least two.
The two support members are supported by two rod-shaped support members, and the two support members are disposed at an angle to each other in a plane substantially parallel to the optical disk. With this configuration, the two support members are arranged in a substantially C-shape. Since the objective lens and the deflecting mirror are integrally and rotatably supported by the supporting member, even if the distance from the objective lens to the rotation axis is increased, the size of the apparatus is not increased.

According to a sixth aspect of the present invention, in the optical pickup device according to the first aspect, the deflection mirror and the objective lens are integrally rotationally driven and controlled based on the tracking error signal, and the tilt error related to the tilt of the optical disk is controlled. It is characterized by controlling the center of the drive amplitude based on the signal, by this configuration, to control the rotational drive of the holder of the objective lens based on the tracking error signal and to control the center of the drive amplitude based on the tilt error signal,
Tracking servo and tilt servo can be performed simultaneously by rotation of the holder.

According to a seventh aspect of the present invention, in the optical pickup device according to the first or sixth aspect, a coarse movement mechanism for moving the entire optical pickup device in a radial direction of the optical disk, and a light spot of a light spot condensed on the optical disk. A coma aberration detecting means for detecting a coma aberration, wherein the deflection mirror and the objective lens are integrally rotationally controlled based on a tracking error signal, and a coarse movement mechanism is controlled based on a detection signal of the coma aberration detecting means. With this configuration, the rotation of the objective lens holder is controlled based on the tracking error signal and the coarse movement mechanism is controlled based on the coma aberration detection signal, so that the tracking servo and the tilt servo are controlled by the rotation of the holder. Can be done simultaneously.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an optical pickup for explaining a first embodiment of the present invention. Reference numeral 1 denotes a light spot S for irradiating a recording surface of an optical disk D with a light spot S during recording / reproduction. Objective lens for condensing the light beam L on the
Is a rising mirror which is disposed below the objective lens 1 and deflects the light beam L toward the objective lens 1; 3 is a deflecting mirror which deflects the light beam L toward the rising mirror 2; A light source such as a semiconductor laser that emits a beam L;
Is a holder to which the objective lens 1 and the deflecting mirror 3 are fixed, and 6 is a support provided on both sides of the holder 5.

7, a rising mirror 2 and a light source 4 are fixed,
Further, a pickup base on which a stem 9 for supporting the support portion 6 of the holder 5 via four support wires 8a, 8b, 8c, 8d made of an elastic body is provided upright. This is a coarse movement mechanism including a motor (not shown) and a driving force transmission mechanism for moving in the direction (x direction).

In the optical pickup having the above-described structure, the light beam L emitted from the light source 4 in the x direction is deflected by the deflecting mirror 3 in the direction (y direction) orthogonal to the tracking direction on the optical disk, and then rises. The light is deflected in a direction (z direction) perpendicular to the recording surface of the optical disk D by the optical disk 2, and is condensed as a light spot S on the optical disk D through the objective lens 1.

FIGS. 2A and 2B are explanatory views for explaining the support structure and operation of the holder. The support wires 8a to 8d are, as shown in FIG. Are arranged in a substantially C-shape on a plane parallel to the recording surface (xy projection plane), and the holders 5 rotate the intersections of the extension lines of the support wires 8a to 8d by bending the support wires 8a to 8d. The reference 11 is freely rotatable. When the holder 5 rotates, the positions of the objective lens 1 and the deflecting mirror 3 move in the x direction as shown in FIG. The holder 5 is driven to rotate by a drive motor (not shown).

FIG. 3 is a perspective view for explaining a state in which the angle of incidence of the light beam on the objective lens changes when the holder rotates, and the holder 5 rotates in the direction of arrow A about the rotation reference 11. Then, the angle of the deflecting mirror 3 changes, and the optical path from the deflecting mirror 3 to the rising mirror 2 is xy.
The optical path from the rising mirror 2 to the objective lens 1 is also swung in the direction of arrow B in the zx plane.

As described above, by rotating the holder 5, the position of the objective lens 1 can be moved in the x direction, and the angle of incidence of the light beam L on the objective lens 1 can be changed in the zx plane. . When the objective lens 1 moves in the x direction, the light spot S on the optical disc D also becomes x.
Move in the direction. Further, when the incident angle of the light beam L to the objective lens 1 changes, the coma of the light spot S on the optical disk D changes.

The coma of the light spot S on the optical disk D is also generated when the optical disk D is tilted. However, the coma due to the tilt of the optical disk D is changed in the opposite direction to the incident angle of the light beam L to the objective lens 1. , Can be offset.

The condition of the objective lens 1 is such that the amount of change in coma aberration generated when the holder 5 is rotated and oscillated by causing the light spot S to follow a slight deflection of the track caused by eccentricity of the optical disk D is an allowable value. Is set to fit in. In the present embodiment, by changing the objective lens 1 to a lens that does not satisfy the sine condition, the amount of change in coma aberration due to the angle of incidence on the objective lens 1 can be set arbitrarily.
The above conditions are easily satisfied.

In the first embodiment, the tracking servo can be performed by controlling the drive of the holder 5 based on the tracking error signal. At the same time, the coma aberration can be corrected by controlling the center of the tracking amplitude based on the tilt error signal. The angle of incidence of the light beam L on the objective lens 1 also fluctuates due to the tracking amplitude, and the coma aberration fluctuates slightly, but this is actually an allowable value.

In the first embodiment, when the tilt detecting means detects a change in the light spot S due to the tilt of the optical disk D, for example, a coma aberration, the tracking amplitude center is determined based on the tilt error signal. Instead of controlling, the coarse movement mechanism 10 for moving the pickup base 7 may be controlled.

FIGS. 4 (a) to 4 (c) are schematic illustrations of the structure and operation of a main part of an optical pickup according to a second embodiment of the present invention for controlling the coarse movement mechanism as described above. Members corresponding to those described in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

When the drive of the holder 5 is controlled based on the tracking error signal at the time of recording / reproducing on the optical disk D, the light spot S is formed on the track due to the eccentricity of the optical disk D as shown in FIG. It gradually moves from the inner circumference to the outer circumference or from the outer circumference to the inner circumference while following small vibrations.

As shown in FIG. 4B, when the amount of movement of the light spot S increases, the angle of incidence on the objective lens 1 also shifts greatly and coma occurs. Coma due to the tilt of the optical disk D at the destination of the light spot S and the objective lens 1
The sum of the coma and the coma due to the shift of the incident angle is detected by a suitable coma aberration detector such as an optical differential element (not shown).

As shown in FIG. 4C, when the coarse movement mechanism 10 is controlled based on the detection signal of the coma aberration detecting means and driven in the direction in which the coma aberration decreases, the angle of incidence on the objective lens 1 is reduced. Instead, pickup base 7 is light spot S
Move to the position where the coma aberration at becomes minimum.

The advantages of the conventional mechanism will be described below based on a specific design example of the second embodiment.

The target system conditions are set as follows. Track swing amplitude: ± 0.1 mm, Allowable coma aberration: equivalent to disk tilt ± 0.05 deg, Maximum generated coma aberration: equivalent to disk tilt ± 0.5 deg, FIG. 5 according to the present embodiment that satisfies the above system conditions FIG. 4 is an explanatory view showing a design example, which is basically the same as the configuration of the first embodiment, but specifically: a distance from the objective lens 1 to the deflection mirror 3: L ₂ = 5 m
m, distance from objective lens 1 to rotation reference 11: L ₁ = 2
29.2 mm, · Equivalent value of disc aberration angle of coma aberration / incident angle deviation: 1 de
g / 1 deg., movable range of holder 5 = rotation angle β ₍ max ₎ : ± 0.3 deg, effective diameter φ of objective lens 1: 4 mm.

When the displacement amount of the objective lens 1 is T, the optical axis deviation amount is a, and the rotation angle of the holder 5 is β, the following formula is established.

[0031]

## EQU1 ## T = L ₁ × β

[0032]

A = L ₂ × β Therefore, from both equations (Equation 1) and (Equation 2),

[0033]

A = (L ₂ / L ₁ ) × T The equation of the equation (3), in order to suppress the optical axis shift a, relative to the distance L ₂ from the objective lens 1 to the deflection mirror 3, increasing the distance L ₁ from the objective lens 1 to the rotational reference 11 It turns out that it is good to do.

In the design example shown in FIG. 5, the allowable coma aberration ±
The allowable variation θ of the incident angle of the objective lens 1 satisfying 0.05 deg is ± 0.05 deg. At this time, the rotation angle of the holder 5 is θ / 2. In order to follow the track shake amplitude t within this rotation angle, the distance L1 from the objective lens 1 to the rotation reference 11 may be set as in (Equation 4) from (Equation ₁ ).

[0035]

L ₁ ≧ 2 × t / θ FIGS. 6 (a) to 6 (c) are explanatory views showing a design example of a conventional mechanism satisfying the system conditions as a comparative example. 6 shows a light beam of a light beam incident on the objective lens 21.
6A and 6C, the lens holder 20 is tilted and the optical axis of the objective lens 21 is shifted with respect to the optical axis of the light beam 22 with respect to the state shown in FIG. It indicates that

In the conventional design example shown in FIG. 6, the movable range of the lens holder 20: ± 1.2 mm, the inclination angle / movement of the lens holder 20: 0.5 deg / 1 mm, and the effective diameter φ of the objective lens 21: 4 mm It is.

Table 1 shows the characteristics of the design example according to the present embodiment and the design example of the conventional mechanism.

[0038]

[Table 1]

In the design example according to the present embodiment, the optical axis shift of the objective lens due to the lens displacement is small, and even if the objective lens is displaced by 1 mm in order to correct the coma aberration generated when the optical disk is tilted by 0.5 deg. Axis shift is 0.0
Only 2 mm is generated.

On the other hand, in the design example of the conventional mechanism, the objective lens optical axis shift occurs by the amount of the lens displacement, and the lens is displaced by 1 mm in order to correct the coma aberration generated when the optical disk is tilted by 0.5 degrees. The optical axis shift also occurs by 1 mm.

By the way, even if the optical axis shift is ± 1 mm, in order to make the light beam incident on the entire effective diameter of the objective lens (4 mm), the incident light diameter needs to be 6 mm. However, since only a light beam having an effective diameter of the objective lens of 4 mm out of the incident light diameter of 6 mm is condensed on the optical disk, the light use efficiency is reduced.

Further, since it is necessary to secure an optical path through which a light beam having a light diameter of 6 mm passes, the apparatus becomes large. Further, the light reflected from the optical disk is guided to a photodetector for detecting an information signal or a control error signal, but the incident position on the photodetector is also shifted according to the optical axis shift. Normal,
It is difficult to realize a detection system that allows an optical axis shift of as much as 1 mm.

However, as described above, according to the configuration of the optical pickup of the present embodiment, the above-mentioned problem caused by the optical axis shift does not occur.

In the configuration of the optical pickup of this embodiment, as shown by the real numerical values in the above-mentioned design example, it is desirable that the distance from the objective lens to the rotation axis be 200 mm or more.
If this distance is short, the fluctuation of coma during the tracking operation becomes large.

However, like a shaft-sliding type actuator as shown in FIG. 7, a movable magnetic circuit section 30 composed of focusing and tracking coils is provided around the periphery, and an objective lens 31 is held at one end. The lens holder 32 has a configuration in which a central portion of the lens holder 32 is vertically movable and rotatably supported by a rotating shaft 35 erected on a base 34 having a fixed magnetic circuit portion 33 composed of a magnet and a yoke. When the distance between the objective lens 31 and the rotating shaft 35 is set to 200 mm or more, the actuator itself becomes 200 mm or more, and the size of the device is significantly increased.

On the other hand, in the present embodiment, as described in the first embodiment, the support wires 8a
8d, the distance from the objective lens 1 to the rotation reference (rotation axis) 11 is 2
Even if it secures more than 00 mm, this part does not increase in size.

[0047]

As described above, according to the present invention,
The objective lens and the deflecting mirror are integrally rotatably supported by a holder or the like, so that tracking by displacement of the objective lens and correction of coma aberration by changing the incident angle of the objective lens can be performed by a single rotation operation. By rotating, an optical pickup device having a simple structure, such as performing tracking servo and tilt servo simultaneously, achieving downsizing, and having good pickup characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an optical pickup for explaining a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for describing a support structure and an operation of a holder according to the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a state in which the angle of incidence of the light beam on the objective lens changes when the holder rotates in the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a schematic configuration and operation of a main part of an optical pickup for describing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a design example according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a design example of a conventional mechanism which is a comparative example with the design example of FIG. 5;

FIG. 7 is an exploded perspective view showing an example of a conventional shaft sliding type actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Rise mirror 3 Deflection mirror 4 Light source 5 Holder 7 Pickup base 8a, 8b, 8c, 8d Support wire 10 Coarse movement mechanism 11 Rotation reference

Claims (7)

[Claims] 1. A light emitted from a light source inward in a plane substantially parallel to the optical disk is deflected in the direction of the surface of the optical disk by a rising mirror, and the deflected light is reflected on the surface of the optical disk by an objective lens. An optical pickup device for converging light as a spot, wherein an incident optical axis of the light to the rising mirror is set substantially perpendicular to a tracking direction of the light spot, and light is optically transferred between the light source and the rising mirror. A deflecting mirror for deflecting inward in a plane substantially parallel to the optical disk, and supporting the deflecting mirror integrally with the objective lens and rotatably about a rotation reference perpendicular to a plane substantially parallel to the optical disk. An optical pickup device, comprising: 2. The optical pickup device according to claim 1, wherein the objective lens is a lens that does not satisfy a sine condition. 3. The optical pickup device according to claim 1, wherein a distance from the objective lens to the rotation reference is longer than a distance from the objective lens to the deflection mirror. 4. When the tracking amplitude is t and the allowable variation of the light incident angle on the objective lens is θ radian, the distance L from the objective lens to the rotation reference is L.
_1, the optical pickup apparatus according to claim 3, wherein a satisfying _{L 1 ≧ 2 × t / θ} . 5. The object lens and the deflecting mirror are provided on the same holder body, and the holder body is supported by at least two rod-shaped support members, and the two support members are supported on a surface substantially parallel to the optical disk. 2. The optical pickup device according to claim 1, wherein the optical pickup devices are arranged at an angle to each other. 6. The method according to claim 1, wherein the deflection mirror and the objective lens are integrally rotationally driven and controlled based on a tracking error signal, and a drive amplitude center is controlled based on a tilt error signal relating to the tilt of the optical disk. The optical pickup device according to claim 1. 7. A coarse movement mechanism for moving an entire optical pickup device in a radial direction of an optical disk, and a coma aberration detecting means for detecting a coma of a light spot condensed on the optical disk, and based on a tracking error signal. 7. The method according to claim 1, wherein the deflecting mirror and the objective lens are integrally rotationally driven and controlled, and the coarse movement mechanism is controlled based on a detection signal of the coma aberration detecting means.
An optical pickup device as described in the above.