JP2912560B2 - 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 an optical pickup applied to an optical disk device for optically recording and reproducing information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and cost reduction of an optical disk device, integration of optical components of an optical pickup has been advanced, and a laser detector unit (hereinafter abbreviated as LD unit) in which a semiconductor laser and a light receiving element are integrated. ) And a hologram laser unit (hereinafter abbreviated as HL unit) in which optical components are integrated in addition to these.

Normally, a light receiving element receives reflected light from an information track of a disk and converts the light into an electric signal. An LD unit (including an HL unit) includes a light emitting element 1 as shown in FIG. The light receiving element 2 is formed in the same package. For this reason, of the light emitted from the light emitting element 1, the light 7 ′ reflected on the inner surface of the package enters the light receiving element 2, and as shown in FIG. Light 11 spread more than 7
Is irregularly reflected by components in the optical path such as the housing 4 and the actuator 5 of the optical pickup and is incident on the light receiving element 2, so-called stray light increases in comparison with an ordinary bulk-structured optical pickup.

[0004] These stray lights are added to a signal component effective as a DC offset component, and particularly have an adverse effect on a focus error signal and a tracking error signal, thereby causing unstable focus and tracking servo. For this reason, in a conventional optical pickup using an LD unit, as shown in FIG. 6, a light shielding plate 10 for forming an aperture 6 for restricting an opening is provided immediately after the LD unit 3 so that light 11 outside the effective light beam diameter is provided. Cut and figure 5
Are removed.

[0005]

The light-shielding plate 10 having the aperture 6 is usually black and is subjected to a surface treatment with low reflectance, but still has a reflectance of about 2 to 3%. For this reason, in the structure as shown in FIG. 6, the light shielding plate 10 for the light 11 outside the effective light beam diameter of the aperture 6 as shown in FIG.
There is a problem that the light cut in step (2) becomes stray light due to the irregular reflection of the aperture 6 itself and enters the light receiving element 2 (FIG. 7).

When the diameter of the aperture 6 is increased, diffuse reflection of the light shielding plate 10 itself is reduced. However, as shown in FIG. 8, light 11 of diffuse reflection of components such as the housing 4 and the actuator 5 behind the aperture 6 is provided. Affected,
There is a contradiction that the original effect of the aperture 6 is reduced. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical pickup capable of removing the influence of stray light due to irregular reflection in view of the conventional problems.

[0007]

According to a first aspect of the present invention, there is provided an optical pickup having a light emitting element, a unit having a light receiving element arranged in parallel with the light emitting element and oriented in the same direction as the light emitting element, and a light emitting element and a light receiving element. A light-shielding plate having an aperture disposed in front of the light-emitting element to transmit light emitted from the light-emitting element and transmitting light incident on the light-receiving element, the aperture having a large diameter near the light-emitting element and having a large diameter on the side far from the light-emitting element. It is characterized in that it has a shape with a smaller diameter.

According to a second aspect of the present invention, in the optical pickup according to the first aspect, the aperture has a substantially conical shape.

[0009]

According to the optical pickup of the first aspect, the light emitted from the light emitting element and passing through the aperture is incident on the recording medium, and the reflected light from the recording medium is incident on the light receiving element through the aperture. Information is detected. In this case, since the aperture is formed such that the diameter on the side closer to the light emitting element is large and the diameter on the side far from the light emitting element is small, the influence of the reflection on the inner surface of the light shielding plate can be reduced, and the light passing through the aperture can be reduced. Is restricted from passing through the aperture toward the light receiving element. In addition, since the light reflected on the inner surface of the aperture enters the light receiving element through a large number of reflections, the amount of light incident on the light receiving element can be reduced, and there is almost no influence of the irregularly reflected light. Thus, stray light due to irregular reflection of light outside the effective light beam diameter can be removed, and a stable servo signal can be obtained when applied to an optical disk device.

According to the optical pickup of the second aspect, since the aperture in the first aspect has a substantially conical shape, in addition to the operation of the first aspect, the manufacture of the light shielding plate becomes easy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of the first embodiment, and FIG. 2 is an enlarged view of an LD unit. 1, an LD unit 3, that is, a laser detector unit is provided at one end of a housing 4, an objective lens 9 is provided at the center of the housing 4, and the objective lens 9 and L
A reflection mirror 8 is provided to face the D unit 3, and a light shielding plate 10 having an aperture 6 is provided on the front surface of the LD unit 3. 5 is an actuator.

The LD unit 3 has a light emitting element 1 and a light receiving element 2 each of which is a semiconductor laser as an embodiment, and is directed toward the aperture 6 in the same direction. Light 7 is incident on the reflection mirror 8 from the light emitting element 1 through the aperture 6, the reflected light is incident on a recording medium (not shown) via the objective lens 9, and the reflected light of the recording medium is reflected on the reflection mirror 8. The light enters the light receiving element 2 through the aperture 6.

In FIG. 2, the aperture 6 has a substantially conical shape. The diameter on the side closer to the LD unit 3, ie, the area of the opening 6a, is large, and the diameter on the far side, ie, the area of the opening 6b, is small. Although a part of the light emitted from the light emitting element 1 of the LD unit 3 is restricted by the opening 6a of the aperture 6, the size of the opening 6b is substantially equal to the effective light beam diameter. By passing only θ, unnecessary light beams can be cut.

Among the light beams outside the effective light beam diameter and incident on the conical slope 6c, which is the inner peripheral surface of the aperture 6, those having a large spread angle travel in the direction of the arrow 7a and are repeatedly reflected many times. After returning to the original direction. Those having a small divergence angle travel in the direction of the arrow 7 b and pass out of the aperture 6. The light traveling in the direction 7a of the light receiving element 2 is partially reflected and returns to the direction of the LD unit 3. However, since the light is repeatedly reflected many times, the light quantity is considerably reduced as compared with the diffuse reflection by the conventional aperture. . Part of the light traveling in the direction 7b of the reflection plate 8 returns to the aperture 6 again due to irregular reflection from the housing 4. However, the light is reflected in the aperture 6 before passing first, and the amount of light is considerably reduced. In addition, the luminous flux due to the irregular reflection from the housing 4 is also reflected at least once on the slope 6c of the aperture 6, so that the amount returning to the LD unit 3 can be almost ignored.

According to this embodiment, the light 7 emitted from the light emitting element 1 and passing through the aperture 6 enters the recording medium,
The reflected light from the recording medium is incident on the light receiving element 2 through the aperture 6, whereby information on the recording medium is detected.
In this case, since the aperture 6 is formed such that the diameter on the side close to the light emitting element 1 is large and the diameter on the side far from the light emitting element 1 is small, the influence of the reflection on the inner surface of the light shielding plate 10 can be reduced, and the aperture 6 can be reduced. Irregularly reflected light of light passing through 6 is restricted from passing through aperture 6 toward light receiving element 2. Also, a slope 6c which is the inner surface of the aperture 6
In order for the light reflected by the light to enter the light receiving element 2, the light passes through a large number of reflections as described above, so that the amount of light incident on the light receiving element 2 can be reduced, and there is almost no influence of these irregularly reflected lights. . Thus, stray light due to irregular reflection of light outside the effective light beam diameter can be removed, and a stable servo signal can be obtained when applied to an optical disk device.

FIG. 3 shows a second embodiment of the present invention. That is, in this optical pickup, the cross section of the aperture 6 in the optical axis direction is formed in a curved shape. Depending on how this curved shape is selected, it is also possible to cause all of the reflected light 7b of the light incident on the side surface 6c 'of the aperture 6 to escape from the aperture 6, thereby further eliminating the influence of stray light on the light receiving element 2. it can. Others are the first
This is the same as the embodiment.

[0017]

According to the optical pickup of the first aspect, the aperture is formed so that the diameter on the side closer to the light emitting element is large and the diameter on the side far from the light emitting element is small. Can be reduced, and the irregular reflection of the light passing through the aperture is restricted from passing through the aperture toward the light receiving element. In addition, since the light reflected on the inner surface of the aperture enters the light receiving element through a large number of reflections, the amount of light incident on the light receiving element can be reduced, and there is almost no influence of the irregularly reflected light. Thereby, stray light due to irregular reflection of light outside the effective light beam diameter can be removed, and when applied to an optical disk device, there is an effect that a stable servo signal can be obtained.

According to the optical pickup of the second aspect, since the aperture in the first aspect has a substantially conical shape, in addition to the effect of the first aspect, the manufacture of the light shielding plate becomes easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a partial sectional view of an optical pickup according to a second embodiment.

FIG. 4 is an explanatory diagram illustrating stray light due to internal reflection of a conventional LD unit.

FIG. 5 is an explanatory diagram showing stray light due to external reflection of a conventional LD unit.

FIG. 6 is a sectional view of an optical pickup in a conventional example.

FIG. 7 is a partially enlarged view of FIG.

FIG. 8 is an explanatory diagram showing stray light due to external reflection of light passing through an aperture in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 light emitting element 2 light receiving element 3 LD unit 6 aperture 7 light 10 light shielding plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/135

Claims (2)

(57) [Claims] A unit having a light-emitting element and a light-receiving element arranged in parallel with the light-emitting element and oriented in the same direction as the light-emitting element; and a light-emitting element disposed in front of the light-emitting element and the light-receiving element. A light-shielding plate having an aperture for transmitting light emitted from the element and for transmitting light incident on the light-receiving element, wherein the diameter of the aperture is larger on the side closer to the light-emitting element and smaller on the side farther from the light-emitting element. An optical pickup characterized by having a shape. 2. An aperture according to claim 1, wherein said aperture is substantially conical.
Optical pickup as described.