JPH08287509A - Optical pickup - Google Patents

Abstract

PURPOSE: To improve detection sensitivity and to make the optical pickup thin on the other hand by fitting a hologram laser unit and a mirror onto a pedestal so as to provide a fixed angle on a surface parallel with the face of a disk. CONSTITUTION: The light emitted from a hologram laser unit 1 parallelly with the face of a disk 5 is diffracted by a diffraction grating part 2 and afterwards, the direction of diffraction on the disk 5, namely, a straight line 7c connecting sub-beams 7a and 7b is matched with a projection 10a from the hologram laser unit 1 to the face of the disk 5 of an optical axis 10 directed toward a mirror 3 having the angle of 45 deg. to the face of the disk 5 by the mirror 3. Namely, the straight line 7c connecting the sub-beams 7a and 7b has an angle θ to a straight line direction 11 of a track 6 and in such a state, tracking detection sensitivity can be made maximum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical disk recording / reproducing apparatus.

[0002]

2. Description of the Related Art In recent years, with the reduction in size and cost of optical disk devices, the integration of optical components of optical pickups has progressed, and a hologram laser unit in which a semiconductor laser, a light receiving element and an optical element are integrated has been used. became. An example of a conventional optical pickup will be described below with reference to the drawings.

FIG. 4 shows an optical configuration of a conventional optical pickup. In the figure, reference numeral 21 denotes a hologram laser unit having a diffraction grating portion 22 which constitutes a diffraction grating for generating a sub beam for tracking detection,
23 is a mirror, 24 is an objective lens, 25 is a disc, 2
6 is a track on the disc, 27 is a main beam, 27
Reference symbols a and 27b are tracking detection sub-beams.
The package shape of the hologram laser unit 21 is a rectangular shape in which one side has arc shapes 28a and 28b whose rotation can be adjusted and whose other side is a short side for the purpose of thinning the optical pickup.

A light beam B emitted from the hologram laser unit 21 parallel to the disk surface (its optical axis is A) has a mirror 23 having an angle of 45 ° with respect to the disk surface.
Is reflected in the direction perpendicular to the disc by the objective lens 2
It is focused on the disk by 4. FIG. 5 is a plan view of FIG. 4, and in FIG.
The optical axis A from the mirror to the mirror 23 is the tangential direction 2 of the track.
It matches 9. Further, the angle θ between the straight line 27c connecting the sub-beams 27a and 27b and the track tangent line 29 normally maximizes the tracking detection sensitivity. Therefore, when the sub-beam pitch is L and the track pitch is P, θ = arcsin (P / 2L ) The hologram laser unit 21 is adjusted so that the angle becomes
The optical axis A is rotated around the center for adjustment.

[0005]

However, as shown in FIG. 6, there is provided a hologram laser unit in which the diffraction direction 30 of the diffraction grating portion 22 in the hologram laser unit 21 is parallel to the short side direction 31 of the hologram laser unit package. When used, in order to incline the sub beam direction 27c and the track tangential direction 29 by the angle θ, the hologram laser unit 21 should be rotated by α with respect to the plane parallel to the disk 25 as shown in FIG. Therefore, there is a problem in that the thickness of the optical pickup 33 is increased by the protrusion H of the hologram laser unit 21 with respect to the optical base 32.

To alleviate this problem, a means for inclining the diffraction grating portion 22 by a certain angle in advance with respect to the package of the hologram laser unit 21 is used as shown in FIG. Since the numerical value of L, that is, the numerical value of θ varies depending on the magnification specification of the lens, it is impossible to strictly prevent the hologram laser unit 21 from protruding.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art with the object of providing a thin optical pickup.

[0008]

In order to solve the above-mentioned problems, an optical pickup according to the present invention is integrally provided with a diffraction grating for generating a sub beam for tracking detection, and the diffraction direction thereof is the short side direction of the package. With a hologram laser unit, a base on which the hologram laser unit is rotatably mounted about its optical axis, and a light beam fixed to the base and emitted from the hologram laser unit perpendicular to the disk surface. A mirror that reflects in a direction and an objective lens that is arranged between the mirror and the disk surface, and the optical axis direction of the light beam from the hologram laser unit toward the mirror and the tangential direction of the track on the disk The angle between the hologram laser unit and The mirror those attached to the base.

In the optical pickup of the present invention, the angle θ between the projection of the optical axis from the hologram laser unit toward the mirror onto the disk surface and the tangential direction of the track on the disk is such that the sub beam pitch is L and the track pitch is P
Then, the hologram laser unit and the mirror are attached to the base so that θ = arcsin (P / 2L).

[0010]

According to the present invention, the hologram laser unit is arranged so as to be parallel to the disk surface and the straight line between both sub-beams with respect to the track of the disk is tilted at a constant angle by only adjusting a small amount thereof. Therefore, the optical pickup can be made thinner.

[0011]

Embodiments of the optical pickup of the present invention will be described in detail below with reference to FIGS. 1 is a perspective view of an optical system of an optical pickup according to an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a side view of the optical pickup.

In the figure, reference numeral 1 is a hologram laser unit having a diffraction grating portion 2 which constitutes a diffraction grating for generating a sub beam for tracking detection, and has a light emitting element and a light receiving element therein. . 3 is a light beam B from the hologram laser unit 1 (its optical axis 1
0) is a mirror for reflecting the light beam in the vertical direction, 4 is an objective lens for condensing the light beam B, 5 is a disk for irradiating the condensed light beam, and 6 is a track on the disk 5. Reference numeral 7 is a main beam of the light beam B focused on the disk 5, 7a and 7b are sub-beams for tracking detection, 7c is a straight line connecting the sub-beams 7a and 7b, and 11 is a tangential direction of the track 6. . The package shape of the hologram laser unit 1 is a rectangular shape with one long side and the other short side in order to make the optical pickup thin, and the diffraction direction of the hologram laser unit 1 is the short side direction 8 of the package. It is parallel to (vertical direction). Further, the hologram laser unit 1 has arcuate shapes 9a and 9b capable of rotationally adjusting the hologram laser unit 1 in the short side direction 8 and serves as an adjustment guide when the hologram laser unit 1 is attached to the base 12 constituting the optical pickup 13. .

Here, the hologram laser unit 1 is
The optical axis 10 is attached so as to be parallel to the surface of the disk 5. Then, in the plane parallel to the disc 5, as shown in FIG. 2, the angle between the projection 10a of the optical axis 10 from the hologram laser unit 1 toward the mirror 3 onto the disc surface and the tangential direction 11 of the track 6 is θ, When the sub-beams 7a and 7b pitch is L and the track pitch (not shown) is P, the hologram laser unit 1 and the mirror 3 are placed on the optical pickup base 12 so that θ = arcsin (P / 2L). It is attached. It should be noted that θ in FIG. 1 represents an angle between the optical axis 10 and a line 11a parallel to the tangential direction 11 of the track 6 and is the same as θ in FIG.

The operation of the optical pickup constructed as described above will be described below. In FIGS. 1 and 2, the light emitted from the hologram laser unit 1 in parallel with the surface of the disk 5 is diffracted by the diffraction grating portion 2 and then perpendicular to the disk 5 by the mirror 3 having an angle of 45 ° with respect to the surface of the disk 5. It is reflected in the direction and is focused on the disk 5 by the objective lens 4. At this time, the diffraction direction on the disk 5, that is, the sub-beams 7a and 7b
A straight line 7c connecting the lines coincides with the projection 10a of the optical axis 10 from the hologram laser unit 1 toward the mirror 3 onto the disk 5 surface. That is, the straight line 7c connecting the sub-beams 7a and 7b has an angle θ with respect to the tangential direction 11 of the track 6, and the tracking detection sensitivity can be maximized in this state.

According to the present embodiment described above, the package of the hologram laser unit 1 needs to be rotationally adjusted by a very small amount in the arc shapes 9a and 9b due to the error of each component in practice. Compared to the example, the hologram laser unit 1 can be kept substantially parallel to the surface of the disk 5, and the protrusion from the base 12 in FIG. 3 can be eliminated.

[0016]

As described above, according to the optical pickup of the present invention, the hologram laser is integrally provided with the diffraction grating for generating the sub beam for tracking detection, and the diffraction direction thereof coincides with the short side direction of the package. A unit, a base on which the hologram laser unit is rotatably mounted about its optical axis, and a mirror fixed to the base for reflecting a light beam emitted from the hologram laser unit in a direction perpendicular to the disk surface. And an objective lens disposed between the mirror and the disk surface, and the angle between the optical axis direction of the light beam from the hologram laser unit toward the mirror and the tangential direction of the track on the disk is the disk surface. The hologram laser unit and the mirror on the base so that they have a certain angle on a plane parallel to Since Attach, you can keep a hologram laser unit relative to the disk surface, substantially parallel,
It is possible to reduce the thickness of the optical pickup.

When the sub-beam pitch is L and the track pitch is P, the angle θ between the projection of the optical axis from the hologram laser unit toward the mirror onto the disk surface and the tangential direction of the track on the disk is θ = By attaching the hologram laser unit and the mirror to the base so as to be arcsin (P / 2L), the hologram laser unit can be arranged so that the tracking detection sensitivity is maximized.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical system of an optical pickup according to the present invention.

FIG. 2 is a plan view of the optical system.

FIG. 3 is a side view of the optical pickup.

FIG. 4 is a perspective view of an optical system of an optical pickup in a conventional example.

FIG. 5 is a plan view of the optical system.

FIG. 6 is a front view of the hologram laser unit cited in the present invention.

FIG. 7 is a side view of an optical pickup in a conventional example.

FIG. 8 is a front view of a hologram laser unit in another conventional example.

[Explanation of symbols]

 1 Hologram Laser Unit 2 Diffraction Grating Part 3 Mirror 4 Objective Lens 5 Disk 6 Tracks on Disk 7a, 7b Sub-beam for Tracking Detection 8 Short Side Direction 10 Optical Axis 11 Track Tangent Direction 12 Base

Claims (2)

[Claims] 1. A hologram laser unit in which a diffraction grating for generating a sub-beam for tracking detection is integrally provided, and the diffraction direction thereof coincides with the short side direction of the package, and the hologram laser unit is centered on its optical axis. A rotatably mounted base, and a mirror that is fixed to the base and reflects a light beam emitted from the hologram laser unit in a direction perpendicular to the disk surface,
An objective lens arranged between the mirror and the disk surface is provided, and an angle between an optical axis direction of a light beam from the hologram laser unit toward the mirror and a tangential direction of a track on the disk is parallel to the disk surface. An optical pickup characterized in that the hologram laser unit and the mirror are attached to the base so as to have a constant angle on a flat surface. 2. The angle θ between the projection of the optical axis from the hologram laser unit toward the mirror onto the disk surface and the tangential direction of the track on the disk is θ = when the sub beam pitch is L and the track pitch is P. The optical pickup according to claim 1, wherein the hologram laser unit and the mirror are attached to the optical base so as to be arcsin (P / 2L).