JPS6247831A - Optical head - Google Patents

Abstract

PURPOSE:To improve both the operability and the productivity of optical heads by using a plastic molded body to form at least a part of a component member and providing a metallic layer to an adhering surface of the plastic molded body where another component member is attached with an adhesive. CONSTITUTION:A laser diode holding frame 10 and an optical head main body 11 are formed with the plastic molded body. Then, a laser diode 1 is fixed to the frame 10 via an adhesive and this frame 10 fixed to the main body 11 with an adhesive. While a collimator lens holding frame 12 is also fixed to the frame 10 by the adhesive in the same way after the inserting position is decided for optical beams. When the member composing of the plastic molded part is fixed by the adhesive, the adhesive needs the low viscosity and a high hardening speed. Furthermore a metallic layer 15 is coated over the surface of the plastic molded body in order to secure the desired adhesive intensity. Thus it is possible to improve both the operability and the productivity of optical heads.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical head for recording and reproducing information on and from optical recording media such as optical discs such as compact discs and video discs, and optical recording media such as magneto-optical discs. It is something.

[Conventional technology]

Conventional optical heads employ a light source consisting of a laser diode, an optical system that guides the light beam emitted from this light source to an objective lens, and force-force control by displacing the objective lens in the direction of its optical axis and in a direction approximately perpendicular to it. The main body of the optical head, which supports the actuator that performs tracking control and the light receiving element consisting of a photodiode that receives the light beam reflected from the recording medium through an objective lens, is made of a molded body of metal such as aluminum or zinc. It is composed of

In this conventional optical head, it is necessary to achieve surface accuracy and dimensional accuracy of the optical head body in order to achieve the desired positional relationship of various parts mounted on the optical head body.
Therefore, cutting is required after molding, which increases the number of steps and increases costs.

Further, the weight of the optical head body made of a metal molded body is heavy, for example, about 30 g, and the weight of the entire optical head is about 60 g. As a result, inertia increases, and a power source with a large output is required to drive the optical head in a direction perpendicular to the tracks of the recording medium, that is, in the radial direction of the disk-shaped recording medium, and high-speed feeding becomes difficult. However, there is a disadvantage that the access time required to move the optical head to a desired track position is long.

A conceivable solution to these drawbacks is to construct the optical head body and various other members from lightweight plastic moldings. If the optical head body and various parts are made of plastic moldings, not only will cutting work to achieve surface and dimensional accuracy become unnecessary, but the weight of the optical head can also be reduced, and problems caused by inertia can be avoided. It has the great advantage of being able to solve problems.

[Problem that the invention seeks to solve]

As mentioned above, an optical head whose optical head body is made of a molded plastic body has various advantages, but for example, when attaching a laser diode mounting member equipped with a laser diode to the optical head body, In order to simplify the assembly process and reduce the number of parts, bonding with adhesive may be considered. In addition to such a laser diode mounting member, for example, a mounting member equipped with a photodiode may be adhered to the optical head body with adhesive, or a collimating lens that converts the light beam emitted from the laser diode into a parallel beam may be supported. It is also conceivable to adhere the lens barrel to the laser diode support member.

In this way, when a part of the optical head component is made of a plastic molded body and other components are fixed to this with an adhesive, it is necessary because plastic generally has poor adhesion to other components. It is difficult to obtain sufficient adhesive strength. In general, adhesives that cure quickly have weak adhesive strength, so it is necessary to use epoxy adhesives to obtain high adhesive strength. However, epoxy adhesives have a slow curing speed,
It requires about 1 hour of curing time and has the disadvantage of poor workability. In addition, in order to shorten the curing time, for example, 70
It is also possible to put it in a furnace at a high temperature of ~120℃,
There is a drawback that mass production is impaired because it is removed from the production line. Furthermore, since the epoxy adhesive has a high viscosity, the adhesive layer becomes thick, which also has the disadvantage of making it difficult to achieve positional accuracy. Particularly in optical heads, various optical systems are required to have extremely high positional accuracy, so it is not preferable to use an adhesive that does not provide high positional accuracy.

The object of the present invention is to eliminate the above-mentioned drawbacks, use an adhesive with a low viscosity and a fast curing speed, and obtain high adhesive strength.
This aims to provide an optical head that is easy to work with and can be mass-produced.

[Means for solving problems]

The present invention provides a light source that includes a light source, an objective lens that projects a light beam emitted from the light source as a spot onto a recording medium, an actuator that drives the objective lens in the direction of an optical axis and a direction substantially perpendicular thereto, and an optical system. In the head, at least the common parts of the constituent members are made of plastic molded bodies, and at least a metal layer is provided on the bonding surface of the plastic molded body to which other constituent members are bonded with an adhesive. It is characterized by:

[For production]

In the optical head of the present invention described above, since the metal layer is provided on the surface to be bonded with an adhesive, strong bonding can be achieved using an adhesive that has a fast curing speed, low viscosity, and good workability. Furthermore, since the curing speed is fast, there is no need to put it in a high-temperature furnace, so there is no need to remove it from the production line, which improves mass productivity. Furthermore, the metal layer can be simply applied to the plastic molded body by plating, so that the above-mentioned effects of using the plastic molded body as a component are not impaired.

〔Example〕

FIGS. 1A and 1B are a sectional view and a plan view showing an embodiment of the present invention. In this embodiment, a light beam emitted from a laser diode 1 constituting a light source is made into a parallel beam by a collimator lens 2 and is made incident on a polarizing prism 3 and transmitted through the polarizing film 3a, and this transmitted light is passed through a reflecting prism 4 at right angles. After being totally reflected, the light is guided through a 174-wavelength plate 5 to an objective lens 7 that can be displaced in the optical axis direction and a tracking direction perpendicular to the optical axis direction by an actuator 6, and is projected onto an optical disk (not shown) in the form of a spot.

In this embodiment, it is assumed that information recorded on an optical disc is to be reproduced. The reflected light from this optical disk follows the same optical path as the outgoing path up to the polarizing prism 3 and is made incident on the polarizing film 3a, but on the returning path, the direction of polarization changes due to the action of the quarter-wave plate 5 relative to the polarizing direction of the outgoing path. Since they are perpendicular to each other, all the returned light is reflected by the polarizing film 3a. The return light from the optical disk reflected by the polarizing film 3a is reflected by a critical angle prism 8 having a reflecting surface 8a set at an almost critical angle with respect to the central ray, as shown in a perspective view in FIG. The light is received by a photodetector 9 having a light receiving area divided into four parts,
Detecting information signals, focusing error signals and tracking error signals.

The laser diode 1 is held in a holding frame 10 and attached to an optical head main body 11. The collimator lens 2 is held in a holding frame 12, and the holding frame 12 is positioned and adhesively fixed within the holding frame IO for the laser diode so that the light emitted from the collimator lens 2 becomes a parallel beam. Further, the polarizing prism 3 and the critical angle prism 8 are integrally constructed, and are attached to the optical head body 11 so as to adjust the angle of incidence of the return light from the optical disk on the reflective surface 8a of the critical angle prism 8 with respect to the center line. Hold it so that it can rotate. Furthermore, the reflection prism 4 and the quarter-wave plate 5 were integrally constructed and fixed to the optical head main body 11, and the photodetector 9 was attached to the optical head main body 11 so as to face the output surface of the critical angle prism 8. It is attached to the holding member 13. The entire optical head is the optical bed body 1.
1 and a cover 14 are formed into a box shape, and an opening 14a is formed in a portion of the cover 14 facing the objective lens 7.

In this embodiment, the laser diode holding frame 10 and the optical head main body 11 are made of plastic moldings, and the laser diode 1 is adhesively fixed to the holding frame 10 using an adhesive. It is adhesively fixed to the head body 11. Further, the collimator lens holding frame 12 is similarly made of plastic, and the collimator lens 2 is adhesively fixed with an adhesive, and the holding frame 12 holding the collimator lens 2 is placed inside the laser diode holding frame 10. The insertion position is determined so that the light beam emitted from the laser diode 1 via the collimator lens 2 becomes a parallel beam, and is similarly adhesively fixed to the laser diode holding frame 10 with an adhesive.

In the present invention, when bonding and fixing a member made of a plastic molded body with an adhesive, an adhesive having a low viscosity and a fast curing speed is used, and in addition, the necessary adhesive strength is obtained. , a metal layer 15 is applied to the surface of the plastic molded body.

Such a gold @ layer 15 can be formed, for example, by depositing a Cu plating layer on the plastic molded body as a preliminary treatment, and then depositing an N1 layer thereon by electroless plating.
A thickness of about 10 Atm is sufficient. In order to adhere such a metal layer 15 to the surface of a component made of a plastic molded body, an adhesive having a fast curing speed, for example, an air-curing modified acrylate adhesive can be used.

Therefore, work efficiency is improved, and there is no need to remove the product from the production line for curing, resulting in improved mass productivity.

In addition, as in this embodiment, the laser diode holding frame 10
When the metal layer 15 is deposited on the surface of the holding frame, the surface of the holding frame will not be charged with static electricity, so that damage to the laser diode due to discharge phenomenon can be effectively prevented.

Note that the holding frame 10, the optical head main body 11, and the holding frame 12
The plastic material that makes up the
Resins such as phenyl sulfide), PEEK (polyether ether ketone), PEI (polyether imide), PC (polycarbonate), PES (polyether sulfone), and epoxy, or to increase strength. It is possible to use these materials mixed with fibers such as glass fibers and carbon fibers.

Next, the configuration of the actuator 6 shown in FIGS. 1A and 1B will be explained with reference to FIG. 3 as well.

FIG. 3 is an exploded perspective view showing the actuator 6 in an enlarged manner. An objective lens 7 that irradiates a light spot onto a recording medium such as an optical disk is attached to a holder 21. This holder 21 is displaced in a focusing direction F parallel to the optical axis of the objective lens 7 to focus a light spot on the recording medium, and is also displaced in a tracking direction T perpendicular to the information track on the recording medium and the optical axis. , is connected to the base 23 via a support mechanism so that the light spot follows the information track. This support mechanism includes a pair of focusing leaf springs 24a and 24b, and a relay member 2.
5, and a pair of tracking leaf springs 26a and 26b.
A pair of focusing leaf springs 24a, 2
4b are the focusing direction F and the tracking direction T while facing each other parallel to each other as seen in the focusing direction F.
Upper and lower grooves 25a are installed in grooves 21a and 21b formed in the side wall of the holder 21 at one end thereof, and formed in the relay member 25 at the other end so as to extend in a direction perpendicular to the direction shown in FIG.
and 25b. The pair of tracking leaf springs 26a and 26b are arranged at one end of each so as to extend in a direction substantially perpendicular to the focusing direction F and the tracking direction T while facing each other at a certain angle α in the tracking direction T. are attached to the left and right grooves 25C and 25d formed in the relay member 25, and the other end is attached to the base 2.
It is attached to grooves 27a and 28a formed in posts 27 and 28 provided in No. 3. The distance between one end of the pair of tracking leaf springs 26a and 26b on the relay member 25 is made shorter than the distance between the other ends of the posts 27 and 28, and the angle α formed by these leaf springs 26a and 26b is, for example, It should be about 30″.

Further, in order to drive the objective lens 7 in the focusing direction F and the tracking direction T, a pair of focusing coils 29a and 29tl are fixed to the side surface of the holder 21 facing the tracking direction T, and a pair of focusing coils 29a and 29tl are fixed to the outside of these focusing coils. tracking coil 30
a and 30b are integrally attached. The magnetic field generating members that generate a magnetic field in cooperation with the focusing coils 29a, 29b and the tracking coils 30a, 30b include a pair of yokes 31 and 32 made of magnetic material, and outer yokes 31a and 31 on both sides of one yoke 31.
Permanent magnets 33a and 33b mounted inside along b
and outer yokes 32a and 3 on both sides of the other yoke 32.
Permanent magnets 34a and 34 mounted inside along 2b
The yokes 31 and 32 are fixed to the base 23 so that their central inner yokes 31c and 32c are inserted into the focusing coils 29a and 29b, respectively.

In this embodiment, the holder 21 and the relay member 25 are made of plastic molded bodies, and the base 23
and bosses) 27 and 28 are constructed from an integrally molded plastic body. In this way, the objective lens 7, the focusing coils 29a and 29b, and the pair of focusing leaf springs 24a and 24b are respectively attached to the holder 2.
Similarly, the other ends of the focusing leaf springs 24a, 24b and one end of the tracking leaf springs 26a, 26b are each adhesively fixed to a predetermined position of the relay member 25. At the same time, the other ends of the tracking leaf springs 26a and 25b are fixed to predetermined locations of the bosses 27 and 28 with an adhesive, and the base 23 is similarly fixed to the optical head body 11 with an adhesive. A metal layer 15 is provided on the bonding surface of the members to be bonded with these adhesives, so that adhesive fixation can be performed accurately and reliably even though a low-viscosity adhesive with a fast curing speed is used.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways.

For example, in the example described above, when bonding members that are both made of plastic molded bodies, a metal layer is coated on the bonding surfaces of both members, but only on the bonding surface of one of the members. You can also wear it. Alternatively, one member may be made of a plastic molded body and the other member may be made of metal. In this case, a metal layer may be applied to the adhesive surface of the plastic member. Bye. That is, in the present invention, at least one of the two members to be bonded to each other is made of a plastic molded body, and a metal layer is attached to the bonding surface.

Furthermore, there are various types of light sources, optical systems, and light receiving elements housed within the optical head body, and there are also various types of actuators. For example, a light source that emits three light beams can be used, and a photodetector that has a light receiving area divided into three or six parts can also be used.

Furthermore, in the above example, the focusing error signal and the tracking error signal are detected using a critical angle prism having a reflective surface set at a critical angle. can also be detected.

〔Effect of the invention〕

According to the present invention described above, since a metal layer is attached to the adhesive surface of a component made of a plastic molded body, a large Adhesive strength can be obtained. Therefore, workability and mass productivity are improved, and manufacturing costs can be reduced. Furthermore, since the adhesive layer can be applied thinly, the positioning accuracy can be improved.

[Brief explanation of drawings]

1A and 1B are longitudinal and transverse sectional views showing the structure of an embodiment of the optical head according to the present invention, FIG. 2 is a perspective view showing the structure of a part of the optical head, and FIG. FIG. 3 is an exploded perspective view showing the configuration. 1...Laser diode 2...Collimating lens 3...Polarizing prism 4...Reflecting prism 5...
・・1/4 wavelength plate 6・Actuator 7・
...Objective lens...Critical angle prism 9...
Photodetector 10...Laser diode holding frame 11...Optical head body 12...Collimator lens holding frame 15...Metal layer procedure? ili Masashi October 24, 1985 Michibe Uga, Commissioner of the Patent Office1, Indication of the case Patent Application No. 189204 of 19892, Name of the invention Optical head 3, Relationship with the person making the amendment Patent application Person (037) Olympus Optical Industry Co., Ltd. 4, Agent 1, Deleted "8 division or" in line 4 of page 15 of the specification, and replaced "and j" with "and j" in line 8 of the same page, and ” is corrected. 2. In the drawing, "Figure 2" is corrected as shown in the attached correction diagram.

Claims (1)

[Claims] 1. In an optical head that includes a light source, an objective lens that projects a light beam emitted from the light source as a spot onto a recording medium, an actuator that drives the objective lens in the optical axis direction and a direction substantially perpendicular thereto, and an optical system. , characterized in that at least the common parts of the constituent members are composed of plastic molded bodies, and that a metal layer is provided at least on the bonding surface of the plastic molded body to which other constituent members are bonded with an adhesive. and a light head.