JP3089200B2 - Optical pickup device - 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 device of an optical disk device for storing data in a computer system or recording and reproducing music and video.

[0002]

2. Description of the Related Art Generally used in an optical disk device,
The semiconductor laser device built in the optical pickup device is
The mainstream is one in which a light receiving element for receiving modulated light from an optical disc is incorporated in the same package as the semiconductor laser. This is usually called a hologram laser.

The hologram laser includes a semiconductor laser (laser light emitting element), a modulated light receiving element for receiving modulated light from an optical disk (optical recording medium), and a hologram diffraction grating. The laser light emitted from the semiconductor laser is guided to the optical disk through the outward path, is reflected and modulated by the optical disk to become modulated light, and returns to the hologram laser through the return path. Then, when the modulated light enters the hologram diffraction grating, the modulated light is diffracted, and the diffracted light is detected by the modulated light receiving element.

FIG. 4 shows a structure of a conventional optical pickup device using the hologram laser. The hologram laser 44 is mounted and fixed to the housing 49 by screws 49b via a spring 49a. The housing 49 is manufactured by aluminum die casting or the like, and has a low reflectance on the inner wall surface.

A laser beam emitted from a hologram laser 44 is diffracted by a hologram diffraction grating 45 to generate a first-order diffracted beam 41 and a -1st-order diffracted beam 41a. The zero-order light 42 guided to the collimator lens 46 is guided to the optical disk 48 by the objective lens 47 via the prism 50. Objective lens 4
Reference numeral 7 denotes an optical disk 4 which is an objective lens actuator 47a.
8 to be focused on.

[0006] The hologram laser 44 is
Has a hologram diffraction grating 45 for bending the modulated light reflected and modulated toward the built-in modulated light receiving element.
Due to the influence of the hologram diffraction grating 45, the outward laser light is also diffracted. The ± 1st-order diffracted lights 41, 41 of this outward path
“a” has not been used conventionally, and has repeatedly attenuated the reflection and scattering in the housing 49 of the optical pickup device. That is, it was light that had been abandoned.

Also, in order for the optical pickup device to operate normally, an auto power control (APC) for keeping the output of the laser beam constant is necessary. A prism 50 is installed at a location, the zero-order light 42 is separated in two directions by the prism 50, and some of the zero-order light 42 is bent to a direction of 90 degrees and guided to the light receiving element 51. Therefore, the zero-order light 4
2 reduces the amount of light reaching the optical disk 48, and compensating for this is a burden on the output power of the semiconductor laser device. This problem was remarkable particularly in a magneto-optical disk device and an optical pickup device used for a recording / reproducing low-reflection disk such as an MD player.

In addition, the use of optical components such as a prism causes an increase in the number of components and an increase in the size, weight, and cost of the optical pickup device, causing problems.

[0009] The above-mentioned problem occurs because auto power control (AP
The method C) is performed since the time when the optical pickup device was designed using a single laser, and even when the design using a hologram laser was made, it was inherited as it was.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention utilizes the characteristics of a hologram laser and guides the first or second order diffracted light to a laser output control light receiving element. Based on the light receiving signal output from the laser output controlling light receiving element, automatic power control control is performed so that the laser light output becomes a target value. Accordingly, it is an object to reduce the number of components of the optical pickup device and to provide a small, lightweight, and inexpensive optical pickup device.

[0011]

As means for solving the above-mentioned problems, an optical pickup device according to a first aspect of the present invention comprises a hologram laser having a hologram diffraction grating, and an optical recording medium comprising the hologram laser. And a housing for shielding the optical path of the laser light emitted to the outside from the outside, wherein the inner wall of the housing receives the diffracted light of the laser light emitted from the hologram laser in the hologram diffraction grating. A light receiving element for controlling the laser output.

An optical pickup device according to a second aspect of the present invention is the optical pickup device according to the first aspect, wherein the light receiving element for controlling the laser output is emitted from the hologram laser. + 1st-order diffracted light of the laser beam in the hologram diffraction grating or -1
It is characterized by receiving the second-order diffracted light.

An optical pickup device according to a third aspect of the present invention is the optical pickup device according to the first or second aspect, wherein the inner wall surface of the housing is configured to reflect the diffracted light. Is formed so as to have low reflectance so as not to generate stray light.

According to a fourth aspect of the present invention, there is provided an optical pickup device comprising: the optical pickup device according to any one of the first to third aspects; An optical element for bending the optical path of the diffracted light and guiding the diffracted light to the light receiving element for controlling the laser output is provided.

An optical pickup device according to a fifth aspect of the present invention is the optical pickup device according to the fourth aspect, wherein the optical element reflects the diffracted light from the hologram diffraction grating. It is a reflecting mirror for guiding to the laser output control light receiving element.

By providing the above-mentioned constitutional means, the optical pickup device according to the first aspect of the present invention has a structure in which the light diffracted by the hologram diffraction grating is received by the light receiving element for controlling the laser output. It is not necessary to split the zero-order light in two directions by a prism as in the above. Therefore, no prism is required, and the size and weight of the optical pickup can be reduced.

The optical pickup device according to the second aspect of the present invention has a structure in which the + 1st-order or -1st-order diffracted light from the hologram diffraction grating is received by the light-receiving element for controlling the laser output as described above. Therefore, processing such as amplification of the detected laser light can be performed using the same circuit as that in the case where the laser light dispersed by the conventional prism is detected and laser output control is performed. Therefore, a low-cost optical pickup device can be provided.

The optical pickup device according to the third aspect of the present invention has a structure in which the inner wall surface of the housing is formed with a low reflectance so that stray light is not generated by reflection of diffracted light as described above. And no stray light due to diffracted light. Therefore, there is no need to provide a circuit for canceling stray light, and a low-cost optical pickup device can be provided.

The optical pickup device described in the fourth aspect of the present invention has a structure in which the optical path of the diffracted light is bent by the optical element and guided to the light receiving element for controlling the laser output as described above. There is no need to install a light receiving element for laser output control at a position where light is directly received. Therefore, the degree of freedom in designing the mechanism of the optical pickup device is increased.

The optical pickup device according to the fifth aspect of the present invention has a structure in which the diffracted light is reflected by the reflecting mirror and guided to the light receiving element for controlling the laser output, as described above. There is no need to install a laser output control light receiving element at a position where light is directly received. Therefore, the degree of freedom in designing the optical pickup device is increased by a simple mechanism.

[0021]

FIG. 1 shows the structure of an optical pickup device according to a first embodiment of the present invention. Housing 9
Is manufactured by aluminum die casting or the like, and the reflectance of the inner wall surface 9d is kept low. Also, the housing 9
Since it is not necessary to provide a prism as compared with the conventional housing 49 of FIG. The hologram laser 4 is mounted and fixed to the housing 9 with screws 9b via springs 9a. Further, a through hole 9c is formed in the inner wall surface of the housing 9 facing the hologram laser 4.
A collimator lens (collimator optical element) 6 that converts the laser light emitted from the hologram laser 4 into parallel light is provided in the through hole 9c. A laser output control light receiving element 3 is provided at a corner 9 e of the surface facing the hologram laser 4. Between the housing 9 and the optical disc (optical recording medium) 8, an objective lens (imaging optical element) 7 that forms a laser beam on the optical disc 8 is provided coaxially with the collimator lens 6. Further, an objective lens actuator 7a for moving the objective lens 7 in the optical axis direction is attached to the objective lens 7.

FIG. 2 shows how the laser beam on the outward path is diffracted by the hologram diffraction grating 5 in the hologram laser 4. The hologram laser 4 has a stem 42
A semiconductor laser and a modulated light receiving element are provided thereon (not shown), and a cap 43 covers the semiconductor laser and the modulated light receiving element. Hologram glass 44 having hologram diffraction grating 5 is embedded on cap 43. Also, from the stem 42,
Leads 41 are provided for supplying a current to the semiconductor laser and extracting a detection signal from the modulated light receiving element.

In the hologram laser 4 described above, the laser light emitted from the semiconductor laser is diffracted by the hologram diffraction grating 5 to generate a first-order diffracted light 1, a -1st-order diffracted light 1a and a 0th-order light 2. In the present embodiment, this + or-first-order diffracted light is used. Although higher-order diffracted light is also generated, the amount of light is extremely small and is not used in the present embodiment.

The zero-order light 2 is guided to a collimator lens 6 and guided to an optical disk 8 by an objective lens 7. The objective lens 7 is driven by an objective lens actuator 7a so as to focus on the optical disk 8. The first-order diffracted light 1 is
The light is guided to the laser output control light receiving element 3, and the laser output control light receiving element 3 outputs a light receiving signal. Based on the light receiving signal of the laser output control light receiving element 3, auto power control is performed so that the output of the semiconductor laser becomes a constant target value. The -1st-order diffracted light 1a is
The reflection / scattering is repeatedly attenuated by the inner wall surface 9d of the second member. Since the reflectance of the inner wall surface 9d of the housing 9 is low, the reflected and scattered laser light does not adversely affect the hologram laser 4.

Here, the intensity of the laser light when the first or second order diffracted light is guided to the laser output control light receiving element and the auto power control is performed is calculated and compared with the conventional example. .

The amount of light incident on the laser output control light receiving element 3 = (hologram coupling efficiency) × (first order diffraction efficiency) = 0.4
3 × 0.08 = 0.034 The hologram coupling efficiency is almost equal to the collimator lens coupling efficiency, and the emission angle of the laser light is (θ
_p , θ _r ) = (11 °, 35 °) and NA (numerical aperture) =
In the case of 0.17, it becomes 0.43. Here, θ _p indicates a radiation angle in a heterojunction plane, and θ _r indicates a radiation angle in a direction perpendicular to the hetero junction. The first-order diffraction efficiency is 8%. From the above,
When the laser output is 3 mw, 3 mw × 0.034 = 0.1
03 mw.

Next, in the conventional optical pickup device of FIG. 4, the amount of light incident on the light receiving element 51 = (hologram coupling efficiency) ×
(0 order diffraction efficiency) × (prism spectral ratio) = 0.43 ×
0.8 × 1/11 = 0.031 Note that the zero-order diffraction efficiency is 80%, and the prism spectral ratio is 10:
It is one. As described above, when the laser output is 3 mw, 3 m
w × 0.031 = 0.093 mw.

As described above, the amount of incident light when the first-order diffracted light of + or-is guided to the light-receiving element for controlling the laser output has an intensity about 10% higher than the amount of incident light when the light is separated by the conventional prism. . Therefore, a conventional circuit can be used as an amplifier circuit for the output of the laser output control light receiving element.

FIG. 3 shows the structure of an optical pickup device according to a second embodiment of the present invention. The housing 39 is manufactured by aluminum die casting or the like, and the reflectance of the inner wall surface 39d is kept low. The hologram laser 34 is mounted and fixed to the housing 39 with a screw 39b via a spring 39a. Further, a through hole 39c is provided on a surface of the inner wall surface of the housing 39 facing the hologram laser 34, and a collimator lens 36 for converting the laser light emitted from the hologram laser 34 into parallel light is provided in the through hole 39c. I have. A laser output control light receiving element 33 is provided on an inner wall surface 39e perpendicular to the hologram laser 34, and a reflecting mirror 30 is provided at a position where the diffracted light from the hologram diffraction grating 35 is guided to the laser output control light receiving element 33. Have been. Between the housing 39 and the optical disk 38, an objective lens 37 that forms a laser beam on the optical disk 38 is provided coaxially with the collimator lens 36. Further, the objective lens 37 has an objective lens actuator 37 for moving the objective lens 37 in the axial direction.
a is attached.

The laser light emitted from the hologram laser 34 is diffracted by the hologram diffraction grating 35 to generate a first-order diffracted light 31 and a -1st-order diffracted light 31a, and the zero-order light 32 is guided to a collimator lens 36. The zero-order light 32 guided to the collimator lens 36 is guided to the optical disk 38 by the objective lens 37. The objective lens 37 is driven by an objective lens actuator 37a so as to focus on the optical disk 38.

The first-order diffracted light 31 is reflected by the reflecting mirror 30 and guided to the laser output control light receiving element 33.
Based on the received light signal of the output of the laser output control light receiving element 33, automatic power control is performed so that the output of the semiconductor laser becomes constant. The -1st-order diffracted light 31
“a” repeatedly attenuates reflection and scattering on the inner wall surface 39 d of the housing 39. Since the reflectance of the inner wall surface 39d of the housing 39 is low, the reflected and scattered laser light does not adversely affect the hologram laser 34.

In this embodiment, the light-receiving element 3 for controlling the laser output is provided by a simple structure using the reflecting mirror 30 and by appropriately changing the installation location and the angle of the reflecting mirror 30.
Third, the degree of freedom in designing the installation place can be increased.

[0033]

As described above, the optical pickup device described in the first aspect of the present invention has a structure in which the light diffracted by the hologram diffraction grating is received by the light receiving element for controlling the laser output. There is no need to split the zero-order light into two directions by a prism as in the conventional case. Therefore, no prism is required, and the size and weight of the optical pickup can be reduced.

The optical pickup device according to the second aspect of the present invention has a structure in which the + 1st-order or -1st-order diffracted light from the hologram diffraction grating is received by the light-receiving element for controlling the laser output. Using the same circuit as that for controlling laser output by detecting laser light split by the prism, processing such as amplification of the detected laser light can be performed. Therefore, a low-cost optical pickup device can be provided.

The optical pickup device according to the third aspect of the present invention has a structure in which the inner wall surface of the housing is formed with a low reflectance so that stray light is not generated by reflection of the diffracted light. No stray light. Therefore, there is no need to provide a circuit for canceling stray light,
An inexpensive optical pickup device can be provided.

The optical pickup device according to the fourth aspect of the present invention has a structure in which the optical element bends the optical path of the diffracted light and guides the diffracted light to the light receiving element for controlling the laser output. There is no need to install a light receiving element for laser output control at the position. Therefore, the degree of freedom in designing the mechanism of the optical pickup device is increased.

The optical pickup device according to the fifth aspect of the present invention has a structure in which the diffracted light is reflected by the reflecting mirror and guided to the light receiving element for controlling the laser output. There is no need to install a light receiving element for controlling the laser output. Therefore, the degree of freedom in designing the optical pickup device is increased by a simple mechanism.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing how a forward hologram laser beam is diffracted by a hologram diffraction grating in the hologram laser.

FIG. 3 is a cross-sectional view illustrating a structure of an optical pickup device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the structure of a conventional optical pickup device.

[Explanation of symbols]

 Reference Signs List 1 1st-order diffracted light 1a-1st-order diffracted light 2 0th-order light 3 laser output control light receiving element 4 hologram laser 5 hologram diffraction grating 6 collimator lens 7 objective lens 7a objective lens actuator 8 optical disk 9 housing 9a spring 9b screw 9c through hole 9d Wall 9e corner

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 5/18 G02B 5/30-5/32 G11B ^7/ 00-7/22 G11B 7/28

Claims (4)

(57) [Claims] 1. An optical pickup device comprising: a hologram laser having a hologram diffraction grating; and a housing for shielding an optical path of laser light emitted from the hologram laser to an optical recording medium from the outside. , the previous bending the light receiving element of the laser output control for receiving the diffracted light in the hologram diffraction grating of the laser beam emitted from the hologram laser, the optical path of the diffracted light from the hologram diffraction grating
An optical pickup device comprising: an optical element that leads to a light receiving element for controlling laser output . 2. The optical element according to claim 1 , wherein the hologram diffraction grating is provided.
For receiving the laser output control by reflecting the diffracted light from the
2. The optical pickup device according to claim 1, wherein the optical pickup device is a reflecting mirror for guiding the device. 3. A light-receiving element for controlling laser output, comprising :
The hologram of laser light emitted from the hologram laser.
+ 1st order diffracted light or -1st order diffraction in Gram diffraction grating
3. The light receiving device according to claim 1, wherein said receiving device receives light.
An optical pickup device according to item 1. 4. An inner wall surface of said housing is provided with said diffracted light.
Is formed with low reflectivity so that stray light does not occur due to reflection of light.
The optical pickup device according to any one of claims 1 to 3, characterized in that they are.