JP3263569B2 - Fixed structure of diffraction grating for optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for fixing a diffraction grating of an optical pickup.

[0002]

2. Description of the Related Art For example, information recorded on a CD (compact disk) is stored as a pit row (track) provided on the disk surface. As an optical pickup device for reading the recorded information, an apparatus using a three-beam method is used. Is often used.

In this three-beam method, a diffraction grating converts a light beam from a light source (semiconductor laser) into zero-order, ±
The light beam is divided into three primary light beams, and the three light spots are focused on the disk so as to be arranged at a position slightly inclined from the information track. Servo is applied so that the levels of the reflected light signals from the ± 1st-order diffracted light spots at both ends are always equal, thereby keeping the position of the center 0th-order light spot at the center of the track.

When the diffraction grating is mounted on a frame (fixed member), since the position of the spot needs to be adjusted, the diffraction grating needs to be mounted rotatable about the optical axis. Various proposals have been made for such a structure for fixing the diffraction grating to the frame. For example, an optical pickup described in Japanese Patent Application Laid-Open No. H2-218028 is known. This is shown in FIG.

In FIG. 1, reference numeral 11 denotes an optical base, and 1 denotes an optical base.
Reference numeral 2 denotes a semiconductor laser having a round seat 12a;
Denotes diffraction grating holders. Optical base 1
1 is provided with a counterbore 11a having the same diameter as the seat 12a for mounting the seat 12a of the semiconductor laser 12, and further provided with a coaxial mounting hole 11b behind the counterbore 11a. Have been.

The diffraction grating holder 14 has a mounting hole 11b.
A first trunk portion 14a larger than the diameter of
1b and a second body 14b having substantially the same diameter as that of the first body 14a.
3 are stored.

The second body 14b of the diffraction grating holder 14
Is inserted into the mounting hole 11b of the optical base 11, and in this state, a leaf spring 15 having a biasing force in the direction of the optical axis 16 is inserted between the first body 14a and the optical base 11. Have been. That is, the diffraction grating holder 14 is
5 is pressed against the optical base 11, but is rotatable. Accordingly, if the diffraction grating holder 14 is manually rotated against the urging force of the leaf spring 15, for example, the position of the spot is adjusted.

[0008]

However, the structure for fixing the diffraction grating has the following problems. That is, the leaf spring 1 is used to press the diffraction grating holder 14.
5, the number of parts increases and the cost increases.

It is an object of the present invention to provide a structure for fixing a diffraction grating of an optical pickup in which the number of parts is reduced and the cost is reduced.

[0010]

According to a first aspect of the present invention, a structure for fixing a diffraction grating of an optical pickup, in order to achieve the above object, divides a light beam emitted from a light source into a plurality of light beams and places it on a disk. The diffraction grating that forms the light spot ,
It is fixed to one end of a substantially cylindrical optical axis (X) direction ,
A projection having a shape along the optical axis direction is provided on a substantially cylindrical outer cylindrical surface, and a diffraction grating holder provided with a plurality of circumferentially provided diffraction grating holders is provided in a hole formed in a frame. be one obtained by press-fitting, the crash <br/> force having a shape along the direction of the optical axis, is cross-sectional shape in a direction perpendicular to the optical axis, the off
Minimum at the pressure contact area with the frame hole ,
The minimum shape has a shape that comes into contact with the frame hole so that the diffraction grating holder can be rotated around the optical axis without difficulty when adjusting the position of the light spot after press-fitting, and the number of protrusions in the circumferential direction is provided. Are four or more.

In order to achieve the above object, the structure for fixing the diffraction grating of the second optical pickup has a projection along the optical axis direction of the diffraction grating holder in addition to the first means. The structure was such that the opening was in line contact with the hole of the frame along the optical axis direction .

In order to achieve the above object, the fixing structure of the diffraction grating of the third optical pickup is provided with the first or second diffraction grating.
In addition to the means, the shape of the diffraction grating holder along the optical axis
The direction of the cross-sectional shape perpendicular to the optical axis direction of the projection having,
Semicircle or triangle.

[0013]

According to the structure for fixing the diffraction grating of the optical pickup in the first means, when the diffraction grating holder having the diffraction grating fixed to one end is press-fitted into a hole formed in the frame. Although a plurality of protrusions along the optical axis direction provided on the outer peripheral cylindrical surface of the diffraction grating holder are pressed against the hole, the entire outer peripheral surface is not pressed against the hole. It is rotated about the optical axis. Therefore, a leaf spring that presses the diffraction grating holder rotatably is not required.

According to the structure for fixing the diffraction grating of the optical pickup in the second means, if the projection of the diffraction grating holder and the hole of the frame are in line contact, the pressure contact portion between the projection and the hole of the frame is formed. At the minimum, the diffraction grating holder can be more easily rotated about the optical axis after the press-fit than the first means. In addition, in the press-fitting of circles that are pressed against each other,
The press-fitting work is difficult due to the strict precision required for the dimensional accuracy of the outer peripheral surface of the diffraction grating holder and the frame hole.However, in line contact at multiple locations due to multiple protrusions, even if there are protrusions there is no problem.

Further, according to the fixing structure of the diffraction grating of the optical pickup in the first means, when at least one of the roundness of the outer peripheral surface and the frame hole of the diffraction grating holder is not Daza, protrusions of the diffraction grating holder If the number is less than three, the diffraction grating holder may be tilted in the frame hole when adjusting the spot position, causing an optical axis shift.
In the case of more than one, the diffraction grating holder is securely pressed into the frame hole and does not tilt.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a diffraction grating holder according to one embodiment of the present invention, FIG. 2 is a cross-sectional view of the diffraction grating holder taken along line AA, FIG.
FIG. 3 is a rear view of the diffraction grating holder, which is applied to a CD optical pickup.

1 to 4, reference numeral 1 denotes a diffraction grating holder made of a substantially cylindrical resin whose axis is coaxial with an optical axis X of a light source (not shown). A stepped through-hole 1d is formed in the core along the axis (optical axis) X. That is, the diffraction grating holder 1 has a substantially hollow cylindrical shape, and a light beam from a light source passes through the through hole 1d.

A plurality of projections 1e are integrally formed on one end face (left end face in FIG. 2) 1b of the diffraction grating holder 1, and a diffraction grating 2 indicated by a virtual line is formed between the projections 1e. The axis is fitted and fixed coaxially with the optical axis X. The diffraction grating 2 divides a light beam emitted from a light source into a plurality of light beams.

On the outer peripheral surface 1c of the diffraction grating holder 1, a large number (12 in this embodiment) of projections 1a are integrally formed along the optical axis X. The cross-sectional shape perpendicular to is semicircular.

The diffraction grating holder 1 thus configured
Are press-fitted into holes 3 indicated by alternate long and short dash lines formed in a frame (not shown) made of resin. Therefore, the frame hole 3 and the projection 1a are in pressure contact with each other by line contact. That is, the pressure contact portion between the projection 1a and the frame hole 3 is minimized, and the diffraction grating holder 1 can be easily rotated about the optical axis X when adjusting the spot position after press-fitting the diffraction grating holder 1. It has become.
When the rotation direction is adjusted, the diffraction grating holder 1 is fixed to the frame hole 3 by, for example, an adhesive.

When the structure of the diffraction grating holder 1 is not provided with the projections 1a, that is, when the outer peripheral surface is circular, the circles are press-fitted, and the outer peripheral surface of the diffraction grating holder 1 and the frame hole 3 are formed. Strict dimensional accuracy is required and press-fitting work is difficult. However, if a plurality of protrusions 1a make line contact at a plurality of places as in the present embodiment, there is no problem because even if there is a protrusion that is not pressed due to some dimensional variation, other protrusions are pressed.

As described above, the diffraction grating holder 1,
Since the frame is formed of resin, it is very difficult to obtain the roundness of the outer peripheral surface of the diffraction grating holder 1 and the frame hole 3, and depending on the number of projections 1a, the diffraction grating holder 1 may not be able to adjust the spot position. There is a fear that the optical axis is tilted in the frame hole 3 to cause an optical axis shift.

Therefore, the present inventor uses the diffraction grating holder 1 and the frame which are not rounded, and uses the diffraction grating holder 1.
The number of protrusions 1a whose spot position can be adjusted without tilting in the frame hole 3 was experimentally examined.
It was confirmed that the spot position can be adjusted without tilting if the number is more than the number.

As described above, in this embodiment, the diffraction grating holder 1 in which the diffraction grating 2 is fixed to one side end (the end surface in this embodiment) 1b is inserted into the hole 3 formed in the frame.
The plurality of protrusions 1a along the optical axis X direction provided on the outer peripheral cylindrical surface 1c of the diffraction grating holder 1 are pressed against the hole 3, and the entire outer peripheral surface is not pressed against the hole 3 so that the diffraction is performed. Since the grating holder 1 is made rotatable about the optical axis X even after press-fitting, and the conventional leaf spring 15 that presses the diffraction grating holder 1 rotatably is not required, the number of parts can be reduced. Thus, cost reduction can be achieved.

Further, in this embodiment, the structure is such that the projection 1a of the diffraction grating holder 1 is in line contact with the hole 3 of the frame, and the pressure contact portion between the projection 1a and the hole 3 of the frame is minimized. Since it is configured to be able to rotate around the optical axis X without difficulty even after press-fitting, it is possible to improve workability. In addition, in the press-fitting of the circles that are pressed against each other over the entire surface, the dimensional accuracy of the outer peripheral surface of the diffraction grating holder 1 and the frame hole 3 is strictly required, and the press-fitting operation is difficult.
The configuration is such that there is no problem even if there is a projection that is not pressed due to some dimensional variation, so that the workability can be further improved.

In this embodiment, if the roundness of at least one of the outer peripheral surface of the diffraction grating holder 1 and the frame hole 3 is not obtained, the number of the projections 1a of the diffraction grating holder 1 is three or less. In some cases, the diffraction grating holder 1 may be tilted in the frame hole 3 when adjusting the spot position, causing an optical axis misalignment. However, the number of the projections 1a of the diffraction grating holder 1 is four or more (12 in this embodiment). ), The diffraction grating holder 1 is securely pressed into the frame hole 3 so as not to be tilted, so that the optical axis does not shift during rotation adjustment, and the detection accuracy of the information signal can be improved. It is possible.

Although the invention made by the present inventors has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, in the above embodiment, the cross-sectional shape of the projection 1a perpendicular to the optical axis X is a semicircle, but is not limited to this shape. May be a triangular shape. In short, any shape may be used as long as the frame hole 3 and the projection come into line contact by press-fitting the diffraction grating holder.

In the above embodiment, the projection 1a and the frame hole 3 are in line contact with each other so that the diffraction grating holder 1 can be easily rotated during adjustment. 1a to change the shape of the frame hole 3
May be brought into surface contact.

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

[0030]

As described above, according to the structure for fixing the diffraction grating of the optical pickup according to the first aspect of the invention , the diffraction grating holder having the diffraction grating fixed to one side end is formed in the frame. Pressing into the hole, pressing a plurality of protrusions along the optical axis direction provided on the outer peripheral cylindrical surface of the diffraction grating holder into the hole,
Since the entire outer peripheral surface is not pressed against the hole, the diffraction grating holder is rotatable around the optical axis even after press-fitting, and a leaf spring for rotatably pressing the diffraction grating holder is unnecessary. Therefore, the number of parts can be reduced, and the cost can be reduced.

According to the structure for fixing the diffraction grating of the optical pickup of the second invention, in addition to the first invention, the projection of the diffraction grating holder and the hole of the frame are in line contact with each other. Since the pressure contact portion of the first embodiment is minimized and the diffraction grating holder can be rotated about the optical axis more easily than the first invention even after press-fitting, the workability is improved in addition to the effect of the first invention. It is possible to improve. In addition, in the press-fitting of the circles that are pressed into the entire surface, the dimensional accuracy of the outer peripheral surface of the diffraction grating holder and the frame hole is strictly required, and the press-fitting work is difficult. Therefore, even if there is a projection that is not pressed, there is no problem, so that the workability can be further improved.

Further, the according to the fixing structure of the diffraction grating of the optical pickup of the first invention, when not out at least one of the roundness of the outer peripheral surface and the frame hole of the diffraction grating holder, protrusions of the diffraction grating holder If the number of is less than three,
The diffraction grating holder may be tilted in the frame hole when adjusting the spot position, causing an optical axis misalignment. However, the number of projections of the diffraction grating holder should be four or more, and the diffraction grating holder should be securely pressed into the frame hole. Since it is configured not to be tilted, in addition to the above-described effects, it is possible to improve the detection accuracy of the information signal without causing the optical axis shift.

[Brief description of the drawings]

FIG. 1 is a front view showing a diffraction grating holder according to an embodiment of the present invention.

FIG. 2 is an AA cross-sectional view of the diffraction grating holder.

FIG. 3 is a sectional view of the diffraction grating holder, taken along the line BB.

FIG. 4 is a rear view of the diffraction grating holder.

FIG. 5 is an exploded perspective view illustrating a main part of an optical pickup according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diffraction grating holder 1a Projection 1b One side end 1c Outer cylindrical surface 2 Diffraction grating 3 Frame hole X Optical axis

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-73495 (JP, A) JP-A-3-152734 (JP, A) JP-A 2-76320 (JP, U) JP-A 64-73 8215 (JP, U) Japanese Utility Model Showa 58-10407 (JP, U) Japanese Utility Model Showa 59-48513 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/135

Claims (3)

(57) [Claims] 1. A diffraction grating for dividing a light beam emitted from a light source into a plurality of light beams to form a light spot on a disk is fixed to one end of a substantially cylindrical optical axis (X) direction. A diffraction grating holder provided with a plurality of projections having a shape along the optical axis direction on the substantially cylindrical outer peripheral cylindrical surface in the circumferential direction, and the diffraction grating holder was press-fitted into a hole formed in a frame. Wherein the projection having a shape along the optical axis direction has a minimum cross-sectional shape in a direction perpendicular to the optical axis at a press-contact portion with the frame hole, and the minimum shape of the projection is after press-fitting. When adjusting the position of the light spot, the diffraction grating holder is rotatable about the optical axis without difficulty.
A fixing structure for a diffraction grating of an optical pickup, characterized in that the fixing structure has a shape that comes into contact with a beam hole and the number of the protrusions in the circumferential direction is four or more. 2. The fixing structure for a diffraction grating of an optical pickup according to claim 1, wherein the projection having a shape along the optical axis direction of the diffraction grating holder is provided.
A structure for fixing a diffraction grating of an optical pickup, wherein the structure is in line contact with the hole of the frame along the optical axis direction . 3. The fixing structure of a diffraction grating of an optical pickup according to claim 1 , wherein the light of the projection having a shape along the optical axis direction of the diffraction grating holder.
A fixing structure for a diffraction grating of an optical pickup, wherein a cross-sectional shape in a direction perpendicular to an axis is a semicircle or a triangle.