JPH07201064A - Mirror for optical pickup - Google Patents

Abstract

PURPOSE:To reduce the height of an optical pickup without limitation by the focul distance of an optical system and to reduce the number of components by integrating the plural components in one body. CONSTITUTION:The mirror 1 for the optical pickup is integrally molded with a plastic as a whole and provided with two reflection surfaces. The angle made by two reflection surfaces 2, 3 is >90 deg.. The grating is formed on one reflection surface 3. A mounting reference surface 4 is provided for mounting a light emitting/receiving unit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror for an optical pickup capable of miniaturizing an optical head of an optical disk device.

[0002]

2. Description of the Related Art In order to miniaturize an optical disk device,
It is essential to downsize the optical pickup. Further, in miniaturization of the optical pickup, there is a strong demand for lowering the height.

In a conventional optical pickup optical system, the optical axis is generally arranged vertically, as disclosed in, for example, Japanese Patent Laid-Open No. 5-250718. In such a pickup, the height is dominated by the focal length of the optical system, and the height cannot be shorter than the optical path length. However, since the optical pickup has to have an optical system with a NA that is fixed to some extent, the focal length is also fixed to some extent, so there is a limit to reducing the optical path length. Here, it is desired to bend the optical path to shorten the height of the optical pickup.

[0004]

However, when the optical path is bent in the optical pickup, how to highly accurately support the components such as the diffraction grating necessary for detecting the focus error and the tracking error. Is a problem. Moreover, not only a structure with a small number of parts, easy assembly and low cost is required, but also durability against vibration and environmental changes is required.

The present invention has been made in view of the above problems, and the height of the optical pickup can be reduced without being limited by the focal length of the optical system, and a plurality of parts can be integrated to reduce the number of parts. An object of the present invention is to provide an optical pickup mirror that can be reduced.

[0006]

In order to achieve the above object, an optical pickup mirror of the present invention is an optical pickup mirror which is integrally molded entirely of plastic and has two reflecting surfaces. The angle between two reflective surfaces is 9
It is characterized in that it is larger than 0 degree and a grating is formed on one reflection surface, and that a mounting reference surface for mounting a light emitting and / or light receiving unit is provided.

[0007]

In the optical pickup mirror of the present invention having the above structure, the optical path is bent at the reflecting surface to shorten the height of the optical pickup. Further, a grating is formed on the reflecting surface to act as a diffraction element to reduce the number of parts. However, when the grating is injection-molded, it is necessary to release the grating in the direction perpendicular to the grating surface.
Therefore, make the angle between the two reflecting surfaces larger than 90 degrees,
This prevents rubbing from occurring on the other reflecting surface when the mold is released in the direction perpendicular to the grating surface. Further, by providing a mounting reference surface for mounting the light emitting / receiving unit, the assembly can be performed accurately and easily.

[0008]

Embodiments of the optical pickup mirror according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an optical pickup mirror, and FIG. 2 is a sectional side view.

The optical pickup mirror 1 has a trapezoidal recess formed on one side surface of a rectangular parallelepiped, and is entirely manufactured integrally by injection molding of plastic, and has a length of 5 mm and a height. It is as small as 1.5 mm. An aluminum reflection film is provided on each of the two surfaces corresponding to the hypotenuses of the trapezoid, one of which is a flat reflection surface 2 and the other of which is a grating surface 3. The grating surface 3 has a pitch of 20μ in the direction parallel to the paper surface.
A large number of linear grating grooves having a depth of m and a depth of 0.3 μm (the depth measured in the direction normal to the surface) are formed, and are used for detecting a tracking error described later.

A mounting reference surface 4 is formed on the upper surface on the right side of the optical pickup mirror 1, and the light emitting / receiving unit 6 is adhered thereto. The light emitting / light receiving unit 6 includes a laser diode 6a for emitting light and a photodiode 6b for receiving light. The optical pickup mirror 1 also has a mounting reference surface 5 for mounting the diffraction grating 7. The diffraction grating 7 is used for detecting a focus error, which will be described later, and has a power with which a grating having a pitch of 5 μm and a depth of 0.4 μm is formed in a direction perpendicular to the paper surface.

When using the optical pickup mirror of the embodiment having the above-mentioned structure, a tracking error is detected by the three-beam method using the grating surface 3.
The focus error is detected by the beam size method using the diffraction grating 7.

First, the detection of tracking error will be described. The laser light emitted from the laser diode 6a is reflected by the grating surface 3 and simultaneously causes a diffraction phenomenon to generate three beams. Each beam reaches the optical disc 9 by the reflecting surface 2, the objective lens 8 and 3
Focus on one spot. The reflected light from the disk surface goes back through the above path and is detected by the photodiode of the light emitting / receiving unit 6 to obtain a tracking error signal by the known three-beam method.

In the optical pickup mirror of this embodiment,
Since the function of bending the optical path on the grating surface 3 and the function of the diffractive element are combined, the number of parts can be reduced as compared with the conventional technique which requires an independent diffraction grating for the three-beam method.

Next, the detection of the focus error will be described. The light returned from the optical disc enters the diffraction grating 7 via the objective lens 9 and the reflecting surface 2. And
By the diffraction grating 7, the + 1st order and the 1st order in the vertical direction of the paper,
Generates -1st-order diffracted light. Each diffracted light is reflected by the grating surface 3 and received by the photodiode 6b. Here, the diffraction grating 7 is designed by a known beam size method. That is, the beam sizes of the + 1st-order diffracted light and the -1st-order diffracted light on the photodiode 6b are changed oppositely before and after the focusing, and the focus error signal is changed by the output difference of each photodiode 6b. Is obtained.

In the optical pickup mirror of this embodiment,
Since the light emitting / receiving unit 6 is adhesively fixed through the mounting reference surface 4, the positional relationship between the reflecting surface 2 and the grating surface 3 and the laser diode 6a and the photodiode 6b becomes accurate and stable.

In order to manufacture the optical pickup mirror of the embodiment constructed as described above, a molding die as shown in FIG. 3 is used. As shown in the figure, this molding die has an insert 11a for forming the grating surface 3 above the parting surface 10 and an insert 11b for forming other recessed portions (including the reflecting surface 2). Sleeve 11 forming the outer periphery
The upper mold 11 composed of c and
A lower die 12 is disposed below the.

When a grating is injection-molded with such a molding die, it must be released in a direction perpendicular to the grating surface 2. However, in the optical pickup mirror 1 of this embodiment, as shown in FIG. 2, since the angle formed by the reflecting surface 2 and the grating surface 3 is 100 degrees, the reflecting surface 2 is not undercut, The mold can be released only by pulling up the mold 11 perpendicularly to the grating surface 3, and at this time, the reflecting surface 2 is not rubbed. As mentioned above, the optical pickup mirror is small,
If a complicated slide mechanism or the like is provided, the cost of the molding die rises. Therefore, it is important that such a simple mold structure can be easily manufactured at low cost.

The present invention is not limited to the above embodiment, but may be implemented as follows, for example. (1) The direction of the grooves on the grating surface 3 is arbitrary. That is, in the above-described embodiment, the groove of the grating surface 3 is vertical and the groove of the diffraction grating 7 is horizontal, but in FIG. 4, this direction is reversed. Further, in the embodiment, the reflecting surface 2 and the disk surface form an angle of 45 degrees, but the grating surface 3 and the disk surface may be changed to 45 degrees as shown in FIG.

(2) As shown in FIG. 5, the reflecting surface 2 and the grating surface 3 may be provided at opposite positions. In this case, contrary to the above embodiment, the tracking error detection is performed by the three-beam method using the diffraction grating 7, and the focus error detection is performed by the beam size method using the grating surface 3.

(3) Although the grating surface and the diffraction grating are provided in order to detect the focus error and the tracking error in the above embodiment, the diffraction grating may not be provided as shown in FIG. This is because this also functions as an optical head depending on the application.

(4) Although the material of the mirror for optical pickup of the present invention is arbitrary, if a material having excellent heat resistance such as polycarbonate is selected, it is suitable for use in a high heat environment such as vehicle mounting. , Zeonex (trade name), which has a small change in water absorption, can be used to obtain parts suitable for use in a humid environment.

[0022]

As described above, according to the optical pickup mirror of the present invention, since the optical path is bent by the reflecting surface, the height of the optical pickup can be reduced without being limited by the focal length of the optical system. it can. Moreover, since the grating is formed on the reflecting surface, the number of parts of the diffraction element can be reduced. Further, since the mounting reference surface for mounting the light emitting / receiving unit is provided, the assembly is accurate and easy. Moreover, it is inexpensive because the whole is manufactured by integral molding of plastic.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional side view showing an optical pickup mirror of Example 1.

FIG. 3 is a diagram illustrating a molding die used for manufacturing the optical pickup mirror of Example 1.

FIG. 4 is a sectional side view showing a first modified example of the optical pickup mirror.

FIG. 5 is a sectional side view showing a second modified example of the optical pickup mirror.

FIG. 6 is a sectional side view showing a third modified example of the optical pickup mirror.

[Explanation of symbols]

 1 Optical pickup mirror 2 Reflecting surface 3 Grating surface 4 Mounting reference surface 5 Mounting reference surface 6 Light emitting / receiving unit 6a Laser diode 6b Photodiode 7 Diffraction grating 8 Objective lens 9 Optical disk 10 Parting surface 11 Upper die 12 Lower die

Claims (1)

[Claims] 1. The whole is integrally molded of plastic and is 2
An optical pickup mirror having two reflecting surfaces,
An angle formed by the two reflecting surfaces is larger than 90 degrees, a grating is formed on one reflecting surface, and an attachment reference surface for mounting a light emitting and / or light receiving unit is provided. For mirror.