JP3083068B2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical pickup device.

[0002]

2. Description of the Related Art For example, recorded information on a CD (compact disk) is stored as a pit row (track) provided on a disk surface. Those using a point aberration method are often used.

FIGS. 5 and 6 show the basic structure of an optical pickup device using the three-beam method and the astigmatism method. In these figures, reference numeral 10 denotes, for example, a semiconductor laser as a light source.
Is collimated by a collimating lens 24. This collimating lens 24 is generally built in a semiconductor laser unit (holder) together with the semiconductor laser 10. The parallel light is reflected by the diffraction grating 11.
Are split into three light beams, and these split lights are guided to a total reflection mirror 13 by, for example, a half mirror 12 as a beam splitter. The split light whose optical path is raised by the total reflection mirror 13 is directed to the objective lens 2. The objective lens 2 focuses three light spots on the recording surface of a disk 16 as a recording medium. These three light spots are respectively reflected by the disk 16 and pass through the objective lens 2 and the total reflection mirror 13 again to return to the half mirror 12, and these reflected lights are reflected by the half mirror 12 with the light flux from the semiconductor laser 10. After being separated, the reflected light is directed to a cylindrical lens 27. Astigmatism is created by the cylindrical lens 27, and the reflected light is guided to a photodetector (six-division light receiving element) 18. The photodetector 18 causes, for example, a focus error and tracking. An error or the like is detected.

[0004]

However, the above optical pickup device has the following problems. That is, since the semiconductor laser 10 and the collimating lens 24 are arranged close to each other, the focal length of the collimating lens 24 cannot be increased, for example, to a focal length of 5 mm. There is a problem that the relative distance error becomes large and it becomes difficult to obtain the parallelism of the parallel light.

Further, since the semiconductor laser 10 and the collimating lens 24 are arranged close to each other as described above,
There is also a problem that the distance between the collimator lens 24 and the objective lens 2 becomes longer, the parallelism of the parallel light from the collimator lens 24 deteriorates, and it becomes difficult to obtain the parallelism.

Further, since the collimating lens 24 is built in the holder together with the semiconductor laser 10 as described above, the assembling includes incorporating the collimating lens 24 into the holder and further attaching the holder to the frame. Therefore, there is also a problem that position adjustment such as assembly and optical axis adjustment becomes complicated.

Accordingly, a first object of the present invention is to provide an optical pickup device in which the parallelism of parallel light by a collimating lens is improved and product accuracy is improved.

In addition to the first object, a second object is to provide an optical pickup device in which the mounting and position adjustment of the collimating lens are easily performed and the manufacturing cost is reduced.

[0009]

According to the first aspect of the present invention, there is provided an optical pickup device for achieving the first and second objects.
The emitted light emitted from the light source is collimated by a collimator lens, and the collimated light is condensed on a recording medium by an objective lens. An objective lens holder holding the objective lens has an optical axis toward the recording medium. In an optical pickup device supported rotatably about a support shaft erected on a frame so as to be parallel to and movable along the support shaft, the collimator lens is disposed in proximity to the objective lens. And the collimating lens is attached to a collimating lens holder integrated with a frame that supports the objective lens holder.
The lower part of the objective lens holder.
On the collimating lens side, the objective lens holder is
Notches are formed so that they do not touch the collimating lens.
And the frame is mounted on the support shaft.
The hollow cylindrical portion from the installation surface toward the objective lens side is
The collimating lens is provided along the optical axis.
The holder is used for the phase between the semiconductor laser and the collimating lens.
In order to reduce the distance error, the hollow cylindrical part
It is characterized by being attached to the upper end surface .
According to a third aspect of the present invention, the light emitted from the light source is converted into parallel light by a collimating lens, and the parallel light is condensed on a recording medium by an objective lens. In the optical pickup device, a lens holder is supported so as to be rotatable about a support shaft erected on a frame so as to be parallel to an optical axis toward a recording medium and to be movable along the support shaft. Is arranged close to the objective lens, and a half mirror and a total reflection mirror for bending an optical path of a light beam emitted from the light source are arranged between the light source and the collimating lens. I have.

According to the optical pickup device of the first or third aspect, since the collimating lens is disposed close to the objective lens, the distance between the collimating lens and the objective lens is shortened, and While the fear of deteriorating the parallelism of the parallel light from the lens is reduced, the distance between the light source and the collimator lens is increased, as a result of the collimator lens being disposed closer to the objective lens, and the light source The relative distance error between the lens and the collimating lens is reduced, and the parallelism of the parallel light is easily obtained.

[0011]

Further, according to the optical pickup apparatus in such claim 1, the collimator lens, since it is attached to the collimating lens holder which is integrated in the frame, the collimating lens to a separate holder relative to the frame The attachment and the position adjustment can be easily performed as compared with the case where the holder is attached to the frame after the attachment.

According to a second aspect of the present invention, in order to achieve the second object, in addition to the first aspect, the mounting surfaces for both the collimating lens and the collimating lens holder are provided with an optical axis facing the recording medium. It is characterized in that it is a plane perpendicular to.

According to the optical pickup device of the second aspect, since the mounting surfaces for both the collimating lens and the collimating lens holder are each made to be a plane perpendicular to the optical axis toward the recording medium, the collimating lens can be used. If it is mounted on a collimating lens holder, it will not fall over the optical axis.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The optical pickup device of this embodiment is different from that of the prior art in that the collimator lens 14 is arranged close to the objective lens 2 as schematically shown in FIGS.

Next, a specific example of such an optical pickup device will be described below with reference to FIG. In FIG. 3, reference numeral 30 indicates a frame.
0, a semiconductor laser 10, a diffraction grating 11,
The half mirror 12, the total reflection mirror 13, the cylindrical lens 17, and the photodetector 18 are fixed to respective holders integrated with the frame 30. In FIG. 3, the semiconductor laser 10 and the diffraction grating 11 are arranged on the other side of the half mirror 12 in the drawing.

The upper portion of the frame 30 above the total reflection mirror 13 in the drawing has a hollow cylindrical shape so that a light beam from the semiconductor laser 10 raised by the total reflection mirror 13 can pass therethrough. A collimating lens holder 30B is provided at the upper end of the hollow cylindrical portion 30a in the figure. The collimating lens holder 30B includes an annular flat surface (the upper end surface of the hollow cylindrical portion 30a in the figure) 30b perpendicular to the optical axis X toward the disk 16 and a part of the outer periphery of the annular flat surface 30b. And a protruding arc-shaped projection 30bb. The mounting surface (lower end surface in the figure) 14a of the collimating lens 14 with respect to the collimating lens holder 30B is a plane perpendicular to the optical axis.

Accordingly, the collimating lens 14 is placed so that the mounting surface 14a of the collimating lens 14 faces the flat surface 30b, and the collimating lens 14 is pressed against the convex portion 30bb, whereby the collimating lens 14 is Positioning is performed, and tilting with respect to the optical axis X does not occur. The collimating lens 14 is fixed to the collimating lens holder 30B by, for example, a UV adhesive.

The above-mentioned objective lens 2 is arranged above the collimating lens 14 in the figure. Next, an objective lens driving device for operating the objective lens 2 will be described below with reference to FIGS. 3 and 4, reference numeral 1 denotes a lens holder.
The lens holder 1 is supported so as to be swingable (rotatable) around a support shaft (fixed shaft) 7 and to be movable along the shaft 7 in a direction perpendicular to the paper surface. The axis of the support shaft 7 is parallel to the optical axis X, and is erected on the side of the hollow cylindrical portion 30 a of the frame 30.

The flange of the objective lens 2 is adhered to the pedestal portion 1b of the lens holder 1.
Are arranged such that their optical axes are parallel to the optical axis X. A pair of focusing drive coils 4 and tracking drive coils 3 are fixed to the peripheral wall 1a of the lens holder 1 at symmetrical positions with respect to the shaft 7 respectively.

The shaft 7 is fixed to the bottom of the outer yoke 9. The outer yoke 9 is formed in a fan shape on both sides with the shaft 7 interposed therebetween, and the outer peripheral edge of the fan shape is bent at a right angle and rises so as to face the driving coils 3 and 4. An arc-shaped magnet 6 is fixed to the inner surface of the rising portion of the outer yoke 9. This magnet 6
Is the direction parallel to axis 7 in the middle (focusing direction)
A groove 6c is formed, and is divided into a focusing magnet portion 6a and a tracking magnet portion 6b with the groove 6c as a boundary. The focusing magnet 6a is polarized and magnetized so that the N and S poles are arranged in the direction of the axis 7, while the tracking magnet 6b is perpendicular to the magnetizing direction of the focusing magnet 6a (tracking direction). The N pole and the S pole are formed in the circumferential direction by being polarized and magnetized. The magnets 6 are arranged in pairs symmetrically with respect to the shaft 7.

The focusing drive coil 4 is arranged to face each magnetic pole of the focusing magnet section 6a. In addition, the tracking drive coil 3
Are arranged so as to face each magnetic pole of the tracking magnet section 6b.

On the bottom surface of the outer yoke 9, an inner yoke 5 is provided so as to project from the paper surface toward this side. Like the outer yoke 9, the inner yoke 5 is formed in a fan shape on both sides of the shaft 7, and the outer peripheral edge of the fan shape is bent at a right angle and rises. The rising portions are connected to the magnet portions 6a and 6a with the driving coils 3 and 4 interposed therebetween.
b. As described above, the inner yoke 5, the driving coils 3, 4, the magnet 6, and the outer yoke 9 are respectively arranged along an arc centered on the shaft 7, and a substantially closed magnetic path passing therethrough is formed in this order from the inside. Have been.

When a drive current is supplied to the focusing drive coil 4, a thrust is generated by the drive current and a magnetic flux in the magnetic circuit, and the objective lens 2 moves in the optical axis direction together with the lens holder 1. When a focusing operation is performed and a drive current is supplied to the tracking drive coil 3, a thrust is generated by the drive current and the magnetic flux in the magnetic circuit, and the objective lens 2 swings about the axis 7 together with the lens holder 1. The movement is performed in the tracking direction, that is, the tracking operation is performed.

A notch is formed on the lower collimating lens side of the lens holder 1 so that the lens holder 1 moves up and down in FIG. 3 by a focusing operation, and the lens holder 1 rotates around a shaft 7 by a tracking operation. Even if the lens holder 1 moves, the lens holder 1 does not come into contact with the collimating lens 14.

Reference numeral 8 in FIG. 4 denotes a balancer provided on the opposite side of the objective lens 2 about the axis 7.

Therefore, the divergent light beam from the semiconductor laser 10 is split into three 0th-order and ± 1st-order light beams by the diffraction grating 11, and these split light beams are split by, for example, a half mirror 12 as a beam splitter. Is bent and guided to the total reflection mirror 13, and the total reflection mirror 1 is
The split light whose optical path has been raised by 3 goes to the collimating lens 14 and is made parallel by the collimating lens 14. The parallel light is directed to the objective lens 2 which is arranged in the vicinity, and is focused by the objective lens 2 as three light spots on the recording surface of a disk 16 as a recording medium. At this time, the three light spots on the disk are focused so as to be arranged at a position slightly inclined from the information track.

These three light spots are respectively reflected by the disk 16, pass through the objective lens 2, the collimating lens 14, and the total reflection mirror 13 and return to the half mirror 12. The light beam is separated from the light beam from the laser 10 and travels to the cylindrical lens 17. When this reflected light passes through the cylindrical lens 17, unnecessary astigmatism and coma created by the half mirror 12 are removed, and astigmatism required for the photodetector 18 at the subsequent stage is created. Has become.

The reflected light passing through the cylindrical lens 17 is guided to a photodetector (six-division light receiving element) 18. Here, in the three-beam method, the diffraction grating 11
The objective lens driving device drives the objective lens such that the levels of the reflected light signals (sub-beam signals) from the ± 1st-order diffracted light spots at both ends of the three 0th-order and ± 1st-order light fluxes divided by the above are always equal. 2, a tracking servo is applied to the objective lens 2. The tracking error signal is obtained by receiving the sub-beam signal by each light receiving element and obtaining the output difference of each light receiving element by a subtractor, and driving the objective lens based on the tracking error signal. By applying a tracking servo to the objective lens 2 by the device, the position of the center zero-order light spot is maintained at the center of the track.

In the astigmatism method, the disc 1
6 is applied to the light beam of the reflected light from the cylindrical lens 17.
Creates astigmatism, and the change of the spot shape (the direction of the ellipse and the ellipticity) due to the focus shift is caused by the four-divided light receiving element (light receiving element that receives zero-order light) disposed between the light receiving elements. The outputs of the diagonal light receiving elements are respectively added by the respective adders, and detected by a focus error signal obtained by taking the output difference of each adder by a subtractor. By applying a focusing servo to the objective lens 2, a light spot can be focused on the disk 16.

As described above, in the present embodiment, the collimating lens 14 is arranged close to the objective lens 2,
While the distance between the collimating lens 14 and the objective lens 2 is shortened to reduce the fear of deteriorating the parallelism of the parallel light from the collimating lens 14, the collimating lens 14 is thus moved with respect to the objective lens 2. As a result of the close placement,
Since the distance between the semiconductor laser 10 and the collimating lens 14 is increased, and the relative distance error between the semiconductor laser 10 and the collimating lens 14 is reduced, so that the parallelism of the parallel light can be easily obtained. Collimating lens 1
4, the parallelism of the parallel light can be improved, and the accuracy of the product can be improved.

Further, the collimating lens 14 is mounted on a collimating lens holder 30B integrated with the frame 30, and after attaching the collimating lens 14 to a separate holder with respect to the frame 30, the holder is mounted on the frame 30.
Since the mounting and the position adjustment can be made easier as compared with those mounted on the device, the manufacturing cost can be reduced.

The mounting surfaces 14a and 3a for both the collimating lens 14 and the collimating lens holder 30B are provided.
Since 0b is a plane perpendicular to the optical axis X toward the disk 16, and the collimating lens 14 is mounted on the collimating lens holder 30B so that the optical axis X does not tilt, the above-mentioned effect can be further enhanced. It has become.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof. Needless to say, for example, in the above embodiment, an example is described in which the optical pickup device is applied to the three-beam method. However, for example, the one-beam method that does not require the diffraction grating 11, the half mirror 1
2. The present invention can be applied to a so-called scoop method or the like that does not require the total reflection mirror 13 and the cylindrical lens 17. In short, it is only necessary that the collimating lens 14 can be arranged close to the objective lens 2.

In the above embodiment, the optical pickup device for a CD has been described. However, it goes without saying that the present invention can be similarly applied to an optical pickup device such as a magneto-optical disk.

[0036]

As described above, according to the optical pickup device of the first or third aspect , the collimating lens is arranged close to the objective lens, and the distance between the collimating lens and the objective lens is shortened. While reducing the fear of deteriorating the parallelism of the parallel light from the collimating lens, the arrangement of the collimating lens close to the objective lens in this way increases the distance between the light source and the collimating lens, The collimator lens is designed to reduce the relative distance error between the collimator lens and the collimator lens, thereby making it easier to obtain the parallelism of the collimated light. It becomes possible.

According to the optical pickup device of the first aspect , in addition to the above-described configuration , the collimating lens is mounted on the collimating lens holder integrated with the frame, and the collimating lens is mounted on a separate holder with respect to the frame. Since the mounting and the position adjustment can be facilitated as compared with the mounting of the holder to the frame after the mounting, the manufacturing cost can be reduced.

According to the optical pickup device of the second aspect , in addition to the first aspect, the mounting surfaces for both the collimating lens and the collimating lens holder are each a plane perpendicular to an optical axis toward the recording medium, and When the lens is mounted on the collimating lens holder, the optical axis is not tilted, so that the effect of claim 1 can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic front view illustrating a basic configuration of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of the optical pickup device.

FIG. 3 is a front view showing a specific example of the optical pickup device.

FIG. 4 is a plan view showing an extracted objective lens driving device of the optical pickup device shown in FIG. 3;

FIG. 5 is a schematic front view illustrating an example of a basic configuration of an optical pickup device in a conventional technique.

6 is a schematic plan view of the optical pickup device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens holder 2 Objective lens 7 Predetermined axis 10 Light source 14 Collimating lens 14a Collimating lens mounting surface 16 Recording medium 30 Frame 30B Collimating lens holder 30b Collimating lens holder mounting surface X Optical axis toward recording medium

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 08-7/22 G02B 7/02

Claims (3)

(57) [Claims] A collimating lens (14) converts collimated light emitted from a light source (10) into collimated light, and focuses the collimated light on a recording medium (16) with an objective lens (2). An objective lens holder (1) holding the objective lens (2) is centered on a support shaft (7) erected on a frame (30) so as to be parallel to an optical axis (X) toward a recording medium (16). The collimating lens (14) is disposed close to the objective lens (2), and is rotatably supported as being movable along the support shaft (7). A collimating lens (14) is attached to a collimating lens holder (30B) integrated with a frame (30) supporting the objective lens holder (1).
And the lower collimator in the objective lens holder (1)
The objective lens holder (1) is provided on the lens (14) side.
Do not abut against the collimating lens (14)
A notch is formed, and the frame (30) has an upright surface for the support shaft (7).
Hollow cylindrical portion (30
a) is provided along said optical axis (X),
The collimating lens holder (30B) is
Distance between the laser (10) and the collimating lens (14)
In order to reduce the separation error, the hollow cylindrical portion (30
An optical pick-up device mounted on the upper end surface (30b) of (a) . 2. The optical pickup device according to claim 1, wherein the mounting surfaces (14a, 30b) for both the collimating lens (14) and the collimating lens holder (30B).
Are optical pickup devices, each of which is a plane perpendicular to an optical axis (X) toward a recording medium (16). 3. A collimating lens (14) converts collimated light emitted from a light source (10) into collimated light, and the collimated light is focused on a recording medium (16) by an objective lens (2). An objective lens holder (1) holding the objective lens (2) is centered on a support shaft (7) erected on a frame (30) so as to be parallel to an optical axis (X) toward a recording medium (16). In the optical pickup device supported rotatably and movably along the support shaft (7), the collimating lens (14) is disposed close to the objective lens (2), and Half mirror (12) and total reflection mirror (13) for bending the optical path of the light beam emitted from the light source (10)
Is arranged between the light source (10) and the collimating lens (14).