JP3518904B2 - 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 used in an optical recording device for recording / reproducing information on / from an optical recording medium.

[0002]

2. Description of the Related Art As a conventional optical pickup, for example,
JP-A-62-197931 and JP-A-62-2
As disclosed in Japanese Patent No. 83430, there is a device in which a beam splitter and a laser diode are integrated and provided on a substrate on which a photodiode is formed, thereby achieving downsizing and cost reduction.

[0003]

However, the above-mentioned JP-A-62-197931 and JP-A-62-2.
When the optical pickup disclosed in Japanese Patent Publication No. 83430 is applied to an infinite optical system using a collimator lens, the optical axis and position of the substrate on which the beam splitter and the laser diode are positioned and fixed and the collimator lens are adjusted. Therefore, an adjustment mechanism for that purpose and a space for parts for adjusting and fixing are necessary. For this reason, even if the beam splitter and the laser diode are integrated on the substrate on which the photodiode is formed, there is a problem that it becomes a major obstacle to downsizing and cost reduction.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup which can adjust the optical axis direction of a collimator lens without adjustment, and is appropriately configured so as to be small in size and low in cost.

[0005]

In order to achieve the above object, the invention according to claim 1 illuminates an optical recording medium through a collimator lens and an objective lens after reflecting a light beam from a laser diode by a beam splitter. In the optical pickup, the return light reflected by the optical recording medium, incident on the beam splitter through the objective lens and collimator lens, and refracted and transmitted through the beam splitter is received by a photodetector. A block in which the beam splitter and the photodetector are mounted on the surface of the same substrate so that a light beam is emitted from the substrate in a direction parallel to the surface; and a base body on which the block and the collimator lens are mounted, Parallel to the optical axis of the light beam emitted from the substrate, which is formed on the side surface of the block. The vertical reference plane, which is perpendicular to the optical plane of the light flux emitted from the sub-plane and the substrate, and the parallel abutting surface for contacting the parallel reference plane, which is formed on the base, and the vertical reference plane. It is characterized in that it has a vertical abutting surface for contact and a mounting surface on which the base is formed in parallel with the vertical abutting surface and for mounting the collimator lens.

According to a second aspect of the present invention, in the optical pickup according to the first aspect, the block has a hermetically sealed structure including the collimator lens, the base and the cover member.

[0007]

According to the invention of claim 1, a laser diode,
The beam splitter and the photodetector are mounted on the surface of the same substrate so that a light beam is emitted from the substrate in a direction parallel to the surface, and the block is formed.
The horizontal reference surface and the vertical reference surface formed on the side surfaces are respectively attached to the horizontal abutment surface and the vertical abutment surface formed on the base body, and are mounted on the base body. here,
Since the vertical contact surface formed on the base body and the mounting surface for mounting the collimator lens are parallel to each other, the distance between the laser diode and the collimator lens can be easily machined accurately, so that There is no need to adjust the optical axis of the collimator lens.

According to the invention of claim 2, the block having the laser diode, the beam splitter and the photodetector mounted on the substrate is sealed by the collimator lens, the base and the cover member. In addition, it is possible to effectively prevent the deterioration of optical characteristics due to humidity and dust of the optical elements forming the block and the occurrence of electrical defects, and it is possible to realize a highly reliable optical pickup. .

[0009]

1A and 1B are a plan view and a partial side view showing the structure of an optical system in a first reference example of an optical pickup developed together with the present invention. In this reference example,
The light emitted from the laser diode 12 is incident on the beam splitter 13, and the light reflected here is collimated by the collimator lens 14 and focused on the optical recording medium 16 by the objective lens 15. In addition, the beam splitter 13
The light that is refracted and transmitted through the beam splitter 13 among the light from the laser diode 12 that is incident on is received by the photodetector 17 for monitoring the light amount, and the light emission output of the laser diode 12 is controlled based on the output thereof. To do.

The light reflected by the optical recording medium 16 is
This beam splitter 1 is made to enter the beam splitter 13 via the objective lens 15 and the collimator lens 14.
The return light from the optical recording medium 16 that refracts and transmits 3 is received by the photodetector 18 for signal detection, and the information signal, the focus error signal and the tracking error signal are detected based on the output thereof.

In this reference example, the laser diode 12
Is mounted on the substrate 11 via the submount 19, and the beam splitter 13 and the photodetector 1 are mounted on the substrate 11.
7 and 18 are also mounted on the board 11, the laser diode 12, the beam splitter 13, and the photodetectors 17, 1.
A block 10 is formed by 8. The submount 19, the beam splitter 13, the photodetectors 17 and 18
When mounting on a substrate 11, for example, in Japanese Patent Application No. 6-162291 (Japanese Patent Laid-Open No. 8-31005), the uppermost surface of the substrate 11 is (110) as previously proposed by the applicant. Anisotropic etching is performed on the substrate 11 by a semiconductor process using a silicon substrate to form vertical grooves having {111} as a side surface at the mounting position of each element, and each element is mounted using these vertical grooves. . In this way, each element can be positioned and mounted with high accuracy.

The substrate 11 of the block 10 is perpendicular to the optical axis 24 of the light emitted from the substrate 11 toward the collimator lens 14 and serves as a reference for mounting the block 10 on a substrate described later. The end surface 21 is formed. For example, when the uppermost surface of the silicon substrate is (110) as the substrate 11, the end face 21 is formed by anisotropic etching, or, as described above,
It can be formed by cutting with a dicer using a precise pattern formed by photolithography.

In this way, if the end face 21 is formed on the substrate 11 and the substrate 11 is anisotropically etched to form a groove, and each element is mounted using the groove, The distance a in the x direction from the light emitting point of the laser diode 12 to the reflecting surface of the beam splitter 13 and the distance c in the z direction from the light emitting point of the laser diode 12 to the end face 21 are set to desired values with high accuracy. You can In this embodiment, the size of the substrate 11 can be set to 5 × 4 mm, for example.

FIGS. 2A and 2B are a plan view and a side view showing a state in which the block 10 and the collimator lens 14 shown in FIGS. 1A and 1B are mounted on a base 20. Base 20
The mounting portion 20a of the block 10 and the mounting portion 20b of the collimator lens 14 having the holes 25 are integrally formed with each other. The attachment surface 23 is attached to the attachment portion 20a.
Then, the end face 21 of the substrate 11 is pressed against the contact surface 23 to position and mount the block 10.
An escape portion 28 is formed below the contact surface 23 so that the end surface 21 of the substrate 11 and the contact surface 23 are surely in surface contact with each other. In addition, the mounting portion 20b has holes 2
5, an attaching surface 22 of the collimator lens 14 is formed, and a flange portion 26 having a hole 26a for attaching the base 20 to the pickup chassis portion or the disc drive body is formed, and a hole 25 is formed in the attaching surface 22. The collimator lens 14 is adhesively fixed so as to be closed.

In the above structure, the collimator lens 14
The distance between the laser diode 12 and the laser diode 12, that is, a + b in FIG. 1A, is determined by the focal length of the collimator lens 14, and if this distance is inaccurate, the light after passing through the collimator lens 14 will be convergent light or divergent light. Therefore, the aberration when the light is converged by the objective lens 14 becomes large, and the recording / reproducing characteristic of information is deteriorated.
Here, the distances a and c on the substrate 11 shown in FIG.
As described above, the position can be accurately obtained by, for example, a positioning method applying a semiconductor process. However, regarding the distance b in the z direction from the reflecting surface of the beam splitter 13 to the mounting surface 22 of the collimator lens 14, the base 20
Depends on the structure of. As shown in FIGS. 2A and 2B, this distance b is set so that when the substrate 11 is fixed to the base 20 by pressing the end face 21 thereof against the base 23, the base 23 and the mounting surface 23 If the distance from 22 is d, it is determined by b = dc. Therefore, if this distance d can be accurately obtained, the adjustment of the collimator lens 14 with respect to the base body 20 in the optical axis direction can be omitted.

Therefore, in this reference example, the mounting surface 22 of the collimator lens 14 and the abutting surface 23 of the substrate 11 are parallel to each other in the same direction in order to make it easy to accurately obtain the distance d therebetween. Face. If the mounting surface 22 and the abutting surface 23 are parallel surfaces facing in the same direction in this way, for example, in machining with a milling machine, without re-fixing the base body 20 and without exchanging the cutting tool. Since the mounting surface 22 and the contact surface 23 can be processed with an accuracy of 10 μm, the optical axis 24
It is possible to realize no adjustment of the collimator lens 14 in the direction.

Therefore, according to this reference example, since the collimator lens 14 can be adjusted in the optical axis direction, the number of assembling steps can be reduced, and the adjustment mechanism and the number of parts can be reduced. The optical pickup can be made smaller and the cost can be reduced. Further, since the mounting surface 22 is a flat surface, the optical axis of the collimator lens 14 in the xy plane can be easily adjusted. That is, when the base body 20 is attached to the pickup chassis portion or the disc drive body, the optical axis 24 of the base body 20 and the optical axis of the objective lens 15 attached to the pickup chassis portion or the disc drive body side must be aligned. In this case, the mounting surface 22 of the collimator lens 14
Is a plane parallel to the xy plane, by pushing the collimator lens 14 with a pin in the xy plane from three directions or four directions, the optical axis of the objective lens 15 and the optical axis 24 of the base 20 are pressed. And can be matched with certainty. further,
In this reference example, since the base body 20 is integrally provided with the flange portion 26 having the hole 26a for attaching the base body 20 to the pickup chassis portion or the disc drive body, the number of parts can be further reduced.

3A and 3B are a plan view and a partial side view showing the structure of the optical system of the optical pickup according to the embodiment of the present invention, and FIGS. 4A and 4B are the block 10 and the collimator lens shown in FIGS. 3A and 3B. 14 and the base 20
FIG. 3 is a plan view and a side view showing a state of being mounted on the board. In this embodiment, the side surface (parallel reference surface) 21a parallel to the optical axis 24 of the substrate 11 is provided with the optical axis 24 of the convex portion 27 formed on the base body 20.
The block 10 is positioned with respect to the base body 20 in the x direction by being applied to a surface 30 (parallel contact surface) parallel to the substrate 20, the submount 19 of the laser diode 12 is protruded from the substrate 11, and the light of the protruding portion is irradiated. A surface (vertical reference surface) 39 perpendicular to the axis 24 is defined as a surface (vertical contact surface) 2 perpendicular to the optical axis 24 of the convex portion 27 of the substrate 20
3, the block 10 is positioned with respect to the base body 20 in the z direction, and other configurations are the same as those of the reference example shown in FIGS. 1 and 2A and 2B. Here, the surface 23 of the convex portion 27 and the mounting surface 22 of the collimator lens 14 are surfaces parallel to each other and oriented in the same direction.

Therefore, also in this embodiment, the distance d in the z direction between the surface 23 for positioning the block 10 of the base body 20 and the mounting surface 22 of the collimator lens 14 can be accurately obtained, so that in the above reference example. In addition to being able to obtain the same effect as, compared to the case of the above reference example,
It is possible to simplify the process of obtaining the distance c in the z direction (see FIG. 1A) from the laser diode 12 to the end face 21 perpendicular to the optical axis 24 of the substrate 11. That is, in this embodiment, since the surface 39 of the submount 19 to which the laser diode 12 is fixed is directly used to position the substrate 11 in the z direction, the distance c shown in FIG. 1A is the distance shown in FIG. 4A. It has nothing to do with d.

FIGS. 5A and 5B are a plan view and a side view showing a partial cross-section of the structure of the main part of the second reference example of the present invention. This reference example corresponds to the block 10 in the first reference example.
Is sealed with the collimator lens 14, the base 20, and the cover 31, and the other configurations are almost the same as those of the first reference example. The cover 31 includes an upper portion 31a and a lower portion 31b, and is attached to the flange portion 26 by adhesion so as to cover the attachment portion 20a.

Further, a plurality of electrically conducting pins 32 are provided in the lower portion 31b so as to penetrate the laser diode 1
2. By connecting the photodetectors 17 and 18 to required pins 32 through wires 33, respectively,
Signals are exchanged between the inside and the outside of the cover 31 via the. In attaching the cover 31, first, the lower portion 31b is adhered to the flange portion 26, the required elements forming the block 10 and the pins 32 are wired by the wires 33, and then the upper portion 31a is covered and adhered. Fix it. At this time, preferably, an inert gas such as argon or nitrogen is sealed inside the cover 31.

According to this reference example, since the block 10 is hermetically sealed, the laser diode 12, the beam splitter 13, and the photodetectors 17 and 18 constituting the block 10 are formed.
It is possible to effectively prevent the deterioration of optical characteristics due to humidity and dust, the occurrence of electrical defects, etc., and thus to realize a highly reliable optical pickup.

The present invention is not limited to the above-described embodiments, but various modifications and changes can be made. For example, also in the above-described embodiment, the block 10 may be covered with a cover to form a closed structure, as in the second reference example.

In the first reference example, the mounting surface 22 of the collimator lens 14 of the base body 20 and the abutting surface 23 of the block 10 are parallel surfaces facing in the same direction. The contact surface 23 and the contact surface 23 may be parallel surfaces facing in opposite directions. That is, FIG.
In FIGS. 2A and 2B, the end face 21 serving as the reference of the block 10 is molded on the left side of the substrate 11 in FIGS.
The contact surface 23 of the base body 20 is formed on the left side. Even in this case, the distance d between the mounting surface 22 of the collimator lens 14 and the abutting surface 23 of the block 10 can be accurately obtained with an accuracy of the order of μm, so that the same effect as the first reference example can be obtained. You can Further, in the first and second reference examples, the laser diode 12 is mounted on the substrate 11 via the submount 19, but the laser diode 12 may be directly mounted on the substrate 11.

[0025]

As described above, according to the invention of claim 1, a laser diode mounted on the surface of a substrate so that a light beam is emitted from the substrate in a direction parallel to the surface,
A block having a beam splitter and a photodetector;
A collimator lens is formed parallel to the vertical mounting surface while forming a horizontal mounting surface and a vertical mounting surface for respectively mounting the horizontal reference surface and the vertical reference surface formed on the side surface of the block on the substrate on which the collimator lens is mounted. Since the mounting surface is formed, the distance between the laser diode and the collimator lens can be easily and accurately obtained by machining. Therefore, adjustment of the collimator lens in the direction of the optical axis can be dispensed with, and the mechanism and parts for adjustment can be reduced, so that the optical pickup can be made compact and low cost.

Further, according to the invention of claim 2, since the block has a closed structure by the collimator lens, the base body and the cover member, in addition to the effect of claim 1, the humidity and dust of the optical element constituting the block are provided. It is possible to effectively prevent the deterioration of the optical characteristics due to the above, the occurrence of electrical defects, etc., and to obtain a highly reliable optical pickup.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical system in a first reference example of an optical pickup developed together with the present invention.

FIG. 2 is a diagram showing a configuration of a main part of a first reference example.

FIG. 3 is a diagram showing a configuration of an optical system in an example of the present invention.

FIG. 4 is a diagram showing a configuration of a main part of the same.

FIG. 5 is a diagram showing a configuration of a main part of a second reference example of an optical pickup developed together with the present invention.

[Explanation of symbols]

10 blocks 11 board 12 Laser diode 13 Beam splitter 14 Collimator lens 15 Objective lens 16 Optical recording medium 17,18 Photodetector 19 submount 20 base 21a Side surface (horizontal reference surface) 22 Mounting surface 23 surfaces (vertical contact surface) 24 optical axis 25 holes 26 Flange 27 convex 30 surfaces (horizontal contact surface) 31 cover 39 planes (vertical reference plane)

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-6-4928 (JP, A) JP-A-59-69986 (JP, A) JP-A-60-187937 (JP, A) JP-A-61- 265743 (JP, A) JP-A-3-44086 (JP, A) JP-A-2-156587 (JP, A) Actual development Sho 63-36923 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 08-7/085 G11B ^7/ 12-7/22

Claims (2)

(57) [Claims] 1. A light beam from a laser diode is reflected by a beam splitter, then irradiated onto an optical recording medium through a collimator lens and an objective lens, reflected by the optical recording medium, and passed through the objective lens and a collimator lens. In an optical pickup in which a photodetector receives return light that is incident on a beam splitter and is refracted and transmitted through the beam splitter, the laser diode, the beam splitter, and the photodetector on the surface of the same substrate, A block mounted so that a light beam is emitted from the substrate in a direction parallel to the surface, a base body on which the block and the collimator lens are mounted, and a light beam of a light beam emitted from the substrate that is formed on a side surface of the block. It is perpendicular to the parallel reference plane parallel to the axis and the optical axis of the light beam emitted from the substrate. A straight vertical reference surface, a parallel abutting surface formed on the base body for abutting the parallel reference surface and a vertical abutting surface for abutting the vertical reference surface, and the vertical abutting surface An optical pickup having the base formed in parallel and a mounting surface for mounting the collimator lens. 2. The optical pickup according to claim 1, wherein the block has a closed structure with the collimator lens, the base and the cover member.