JPS6236752A - Optical head - Google Patents

Abstract

PURPOSE:To decrease the numbers of component parts and manufacturing processes and to prevent effectively the mixture of the harmful light together with improvement of assembling accuracy by using a plastic monolithic molded matter to form an optical element and its holding member and at the same time applying partly the light transmission preventing treatment. CONSTITUTION:A collimator lens 2 and its holding frame 11 are made of a transparent plastic monolithic molded matter. At the same time, a metallic washer 12 is inserted to a place near the incident side of the lens 2 in order to make clear the diameter of the incident luminous flux and to prevent the harmful light from entering the lens 2 through the frame 11. The frame 11 is attached to an optical head main body 13 and a laser diode 1 is attached to an end part of the incident side of the lens 2. The head main body 13 is made of a plastic monolithic molded matter and a reflecting prism 5 is unified with the main body 13. Then a metallic washer 14 is inserted to the periphery of the prism 5 in order to make clear the diameter of the incident luminous flux and to prevent the mixture of the harmful light into the prism 5.

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]

As a conventional optical head, for example, Japanese Patent Application Laid-Open No. 59-20124
There is one described in Publication No. 01. This conventional optical head includes a light source consisting of a laser diode, an optical system that guides the light beam emitted from the light source to an objective lens,
An actuator that performs focusing control and tracking control by displacing the objective lens in the direction of its optical axis and a direction substantially perpendicular to it, and a light receiving element consisting of a photodiode that receives the light beam reflected from the recording medium via the objective lens. It is equipped with

[Problem that the invention seeks to solve]

However, in conventional optical heads, for example, the collimator lens that constitutes the optical system that guides the light beam emitted from the light source to the objective lens is attached to a holding member and fixed to the optical head body via this holding member. This increases the number of parts and assembly man-hours, which increases costs. At the same time, errors accumulate in the mounting between the optical element and its holding member, and between the holding member and the optical head body. However, there is a problem in that the assembly accuracy of the optical system deteriorates. Furthermore, when a reflective prism is attached to an optical head body, for example, the support member is formed integrally with the optical head body using a molded body of metal such as aluminum or zinc, so that the part of the support member that the light beam traverses is It is necessary to form an opening. For this reason, molding becomes troublesome, and when adhering an optical element to this support member, the adhesion area becomes small, the strength becomes weak, and durability is lacking.

A conceivable way to solve this problem is to construct the optical element and its holding member as an integrally molded plastic body. In this way, the number of parts and assembly man-hours are reduced accordingly, and the assembly accuracy can be improved because the mounting error is only between the holding member and the optical head body.

However, if the optical element and its holding member are simply configured as an integrally molded plastic body, the entire body is light-transmissive, and therefore the focusing control and tracking control servos may be affected by harmful light incident from parts other than the optical element. Problems arise in that information becomes inaccurate or information cannot be recorded or reproduced with high precision.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical head that takes full advantage of the advantages of integrally molding an optical element and its holding member from plastic, and effectively solves the problems in this case.

[Means for solving problems]

In order to achieve the above object, the present invention comprises an optical element and its holding member as an integrally molded plastic body, and at least a portion of the optical element is subjected to light transmission prevention treatment.

[For production]

Here, the light transmission prevention treatment is to prevent harmful light from entering the optical element, such as insert molding a metal washer around the optical element, making the area around the optical element sandy, etc.
This can be achieved by applying an impermeable coating, or by mixing black paint as the plastic that constitutes the holding member, or by performing two-color molding using black plastic.

〔Example〕

FIG. 1 is a sectional view diagrammatically 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, and the transmitted light is passed through a 174 wavelength plate 4. Thereafter, the light is totally reflected at right angles by a reflecting prism 5, guided to an objective lens 7 which can be displaced by an actuator 6 in the optical axis direction and in a tracking direction orthogonal thereto, and projected onto an optical disk 8 in the form of a spot. In this embodiment, it is assumed that information recorded on the optical disc 8 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 incident on the polarizing film, but on the returning path, the polarization direction is changed from the polarization direction of the outgoing path due to the action of the 174 wavelength plate 4. Since they are orthogonal, all the returned light is reflected by the polarizing film. The return light from the optical disk reflected by this polarizing film is reflected by a critical angle prism 9 having a reflecting surface 9a 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 10 having a light receiving area divided into four parts, and an information signal, focusing error, and tracking error are detected. Although the internal structure of the actuator 6 is not shown in FIG.
It is disclosed in Japanese Patent No. 4311, and the objective lens 7
is supported by a spring so as to be displaceable in the optical axis direction and in a direction perpendicular to the optical axis direction, and by passing a current in accordance with the focusing error and tracking error through the focusing coil and the tracking coil, the objective lens 7 is moved in the focusing direction and in the tracking direction. It is configured so that it can be displaced in the direction.

In this embodiment, the collimator lens 2 and its holding frame 11 are
In order to clarify the diameter of the incident light beam around the incident side of the collimator lens 2 and to prevent harmful light from entering the collimator lens 2 through the holding frame 11, A metal washer 12 is insert molded. This holding frame 11 is attached to the optical head main body 13, and a laser diode l is attached to the incident side end of the collimator lens 2.

Further, in this embodiment, the optical head main body 13 is constructed of an integrally molded plastic body.
3 is integrally formed with a reflecting prism 5, and a metal washer 14 is inserted around the reflecting prism 5 in order to similarly clarify the diameter of the incident light beam and at the same time to prevent harmful light from entering the reflecting prism 5. Shape.

Here, the plastic material for integrally molding the collimator lens 2 and its holding frame 11 is polycarbonate, if the light beam is an infrared beam with a wavelength of 780 to 800 ntn, which is used for compact discs and video discs, for example. Acrylic or the like can be used. In addition, as the plastic material for integrally molding the reflecting prism 5 and the optical head body 13, it is sufficient that the light beam is reflected by the reflecting prism 5, so in addition to the above-mentioned materials, PPS may be used.
(poly phenyl sulfide), PEEK
(polyether ether ketone), PE5 (polyether sulfone), PEI (polyether imide), epoxy resin, etc. can be used.

According to this embodiment, the collimator lens 2 and its holding frame 11, as well as the reflecting prism 5 and the optical head body 13, are each made of an integrally molded plastic body, so the number of parts and the number of assembly steps are reduced, and the cost can therefore be reduced. . Moreover, since a plastic molded article can be molded extremely accurately as long as the dimensional accuracy of the mold is ensured, assembly accuracy can be easily achieved. Furthermore, collimator lens 2
Metal washers 12 and 14 are insert-molded around the incident side of the reflective prism 5, respectively, so that the diameter of the incident light beam can be defined clearly and the intrusion of harmful light can be effectively prevented. Therefore, optical adjustment can be easily performed, and servo for focusing control and tracking control can be performed accurately, and information can be recorded and reproduced with high precision. Furthermore, since plastic material is about 172 to 173 times lighter than metal, the weight of the optical head can be reduced. Therefore, a low-output power source is sufficient for driving the optical head through the carriage in a direction perpendicular to the information track, that is, in the radial direction of the disk-shaped recording medium, and it can be moved at high speed, reducing access time. It is possible to shorten the time.

Furthermore, since plastic materials have lower thermal conductivity than metals, the heat generated in the coil of the actuator 6 is less likely to be transmitted to the optical head body 13 and reach the laser diode 1, thereby extending the life of the laser diode. can.

In this embodiment, a metal washer 12 is insert-molded around the collimator lens 2 to prevent harmful light from entering, but as shown in FIG. 15, or as the plastic forming the holding frame 11 as shown in Figure 3, black plastic or a material mixed with black paint is used.
This holding frame 11 may be configured with a two-color molded body that is opaque, or the holding frame 11 may be constructed by excluding the collimator lens 2.
A similar effect can be obtained by applying an opaque coat to the inner and/or outer circumference of 1. This can be similarly applied to the reflective prism 5 integrally formed with the optical head main body 13.

FIG. 4 is a diagrammatic sectional view showing another embodiment of the invention. In this embodiment, a laser diode 20 that emits a light beam is attached to an optical system support body 21 made of a plastic molded body, and the light beam is projected toward a diffraction grating 22 . The diffraction grating 22 includes a grating portion 22a in which a large number of grooves are formed and a surrounding annular lens barrel portion 22b that is a holding member for the grating portion 22a.
The lens barrel portion 22b is directly attached to the optical system support body 21. The light beam that has passed through the diffraction grating 22 is split into three light beams, which pass through the half mirror surface 23a of the beam splitter 23 and enter the collimator lens 24. This collimator lens also has a lens section 2 that also performs a lens function.
4a and the surrounding lens barrel part 24b, which is a holding member thereof, are constructed of a transparent plastic molded body integrally molded, and the lens barrel part 24b is directly attached to the optical system support body 21 by adjusting in the optical axis direction. do. The three light beams emitted from the collimator lens 24 are each made into parallel light beams, and the actuator 2
5 to the objective lens 26 which is displaced in the optical axis direction and the tracking direction perpendicular thereto, and the recording medium 27
is irradiated as a spot. In this embodiment, it is assumed that information recorded on the recording medium 27 is to be reproduced. The reflected light beam from the recording medium 27 is focused by the objective lens 26,
The beam splitter 23 passes through the collimator lens 24 again.
The light is reflected by the half mirror surface 23a and enters the concave lens 28. Similarly, the concave lens 28 is composed of a transparent plastic molded body in which a concave lens part 28a and an annular lens barrel part 28b which is a holding member for the concave lens part 28a are integrally molded, and the lens barrel is inserted after adjusting the position in the optical axis direction. The portion 28b is attached to the optical head main body 29 made of a plastic molded body using an adhesive. The light beam transmitted through the concave lens 28 enters a cylindrical lens 30 arranged coaxially with the concave lens 28 . This cylindrical lens 30 also includes a lens portion 30a having a lens function and an annular cylindrical portion 3 that is a holding member for the lens portion 30a.
It is composed of a transparent plastic molded body integrally molded with 0b. The light beams transmitted through the cylindrical lens 30 are incident on a photodiode 31 having a light-receiving area corresponding to each beam, where they are photoelectrically converted and an information signal, a focusing error signal, and a tracking error signal are extracted.

In this embodiment, a molded body in which an optical element and its holding member are integrally molded from plastic, ie, a diffraction grating 22,
A portion of each of the collimator lens 24, concave lens 28, and cylindrical lens 30 is subjected to light transmission prevention treatment in order to prevent unwanted harmful light from entering the optical elements. That is, in the diffraction grating 22, a metal washer 22C is inserted into the inner periphery of the lens barrel portion 22b,
In the collimator lens 24, metal washers 24G, 2 are provided on the inner periphery of the lens barrel portion 24b on both sides sandwiching the lens portion 24a.
4d, and in the concave lens 28, the lens barrel part 2
In the cylindrical lens 30, a metal washer 28c is inserted at the entrance side end of the lens barrel part 30b to define a lens part 30a. Insert 30C.

With this configuration, the same effects as the embodiment shown in FIG. 1 can be obtained. Note that instead of inserting a metal washer, as shown in Figure 3A and B, the periphery of the optical element may be made with sand, or the holding member may be made of opaque plastic and molded in two colors, or the holding member may be made of opaque plastic. An opaque coat may be applied to the inner and/or outer circumference of the member.

5A and 5B are diagrammatic cross-sectional views showing the structure of an optical component in which the concave lens and cylindrical lens shown in FIG. 4 are integrally molded. In the example shown in FIG. 5A, the annular lens barrel portion 40C around the concave lens portion 40a and the cylindrical lens portion 40b are joined together to form an integral body, and the end portion of the lens barrel portion 40C on the incident side is A metal washer 40d is inserted as a light transmission prevention treatment.

Furthermore, the example shown in Fig. 5 shows an example in which the space between the concave lens part and the cylindrical lens part is filled with transparent plastic, and a concave spherical surface 41a for forming the concave lens is formed on the incident side. At the same time, a metal washer 41b for preventing light transmission is inserted to define the spherical surface 41a, and a cylindrical surface 41C constituting a cylindrical lens is formed on the exit side.

Since such a plastic molded body has high molding precision, high precision can be ensured even when two optical elements are integrally molded, and adjustment of the optical axis direction can be made unnecessary.

Note that the light transmission prevention treatment is not limited to the metal washer insert as described above, and of course, sand joints, two-color molding, and opaque coating can also be applied.

FIG. 6 is a diagrammatic sectional view showing the configuration of still another embodiment of the present invention. In this embodiment, the optical system support body and the optical head body that support each optical element and the optical system are constructed of an integrally molded plastic body, and an optical system similar to the optical system shown in FIG. 4 is constructed. have. Therefore, the fourth
The same members as those used in the drawings will be described with the same reference numerals.

In this embodiment, an optical element is formed by providing the following surfaces on each part of the transparent plastic integrally molded body 50. That is, a diffraction grating is formed by providing a large number of strip-shaped grooves 50a on the surface facing the emission surface of the laser diode 20, and a convex spherical surface is provided on the surface from which the light beam is emitted to the objective lens 26 via the beam splitter 23. 50b to form a collimator lens. Further, a concave spherical surface 50C is provided on the surface on which the light beam reflected by the half mirror surface 23a of the beam splitter 23 enters to form a concave lens, and a cylindrical surface 50d is formed on the exit surface to form a cylindrical lens. .

In this way, an impermeable coating layer 51 is provided around the molded body 50 except for the surface on which the optical element is formed and the mounting surface of the beam splitter 23 as a light transmission prevention treatment.

In this way, by simply providing various spherical or strip-shaped grooves on each surface of the plastic molded body 50, the optical head body that supports each optical element, its support member, and the support member that constitute the optical system can be constructed. can do. Note that light transmission prevention treatment is not limited to opaque coating, but can also be achieved by inserting metal to define the optical path, by two-color molding, or by forming sand joints around the surface where optical elements are formed. It can also be applied.

This invention is not limited only to the embodiments described above, and numerous modifications and changes are possible.

For example, there are various types of light sources, optical systems, and light receiving elements that are attached to the optical head body, and there are also various types of actuators. Further, the present invention can also be effectively applied to a case where the objective lens and its holding member are constructed as an integrally molded plastic body. Furthermore, in the above-described embodiments, the optical head main body and the optical system support main body were also constructed of integrally molded plastic bodies, but in the present invention, the optical element and its holding member are integrally molded of plastic, and a part of the optical head body is made of plastic. The optical head main body and the optical system support main body can also be constructed of metal bodies as long as a preventive treatment is applied.

〔Effect of the invention〕

As explained above, according to the present invention, the various optical elements and the holding member are constructed as an integrally molded plastic body, and at least a portion thereof is treated to prevent light transmission, thereby reducing the number of parts and assembling the holding member. Not only can the number of man-hours be reduced, but also the intrusion of harmful light can be effectively prevented.

Therefore, as the number of parts and assembly man-hours are reduced, assembly errors are also reduced, and assembly precision can be improved and the cost can be reduced. Further, since harmful light can be prevented from entering, focusing control and tracking control can be performed with high precision, and information can be recorded and reproduced accurately. Furthermore, if the optical system support body and the optical head body are also made of plastic, the state of the light beam in the optical path can be observed from the outside, and the position adjustment of each optical component becomes easy, making assembly and adjustment work easier.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, FIG. 2 is a partial perspective view of FIG. 1, FIGS. 3A and B are sectional views showing modified examples, and FIG. Diagrammatic cross-sectional view showing another embodiment of the present invention; FIGS. 51A and B are cross-sectional views each showing a modification of FIG. 4; FIG. 6 is a diagrammatic diagram showing still another embodiment of the invention. FIG. 1... Laser diode 2... Collimator lens 3... Polarizing prism 4... 174 wavelength plate 5...
・Reflection prism 6... Actuator 7... Objective lens -... Optical disk 9... Critical angle prism 10... Photodetector 11... Holding frame 12, 1
4... Metal washer 13... Optical head body 15... Sand joint 20...
- Laser diode 21... Optical system support body 22... Diffraction grating 23... Beam splitter 24... Collimator lens 25... Actuator 26... Objective lens 27... Recording medium 28.
...Concave lens 29...Optical head body 30...
・Cylindrical lens 31...Photodiodes 22c, 24c, 24d, 28c, 30c,
40d, 41b - Metal washer 50... molded body
51... Opaque coat layer patent Applicant
Olympus Optical Industry Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Procedure Amendment September 6, 1985 Director General of the Patent Office Michibu Uga 1゜Indication of Case 1985 Patent Application No. 174320 2. Name of the invention Relationship to the case of the person who corrects the optical head 3 Patent applicant (037) Olympus Optical Industry Co., Ltd. 4. Yozenjin Address 7th floor, Kasumiyama Building, 3-2-4 Kasumigaseki, Chiyoda-ku, Tokyo Telephone (581) No. 2241 (representative) 5, Pair of amendments & “Detailed description of the invention” column of the specification, page 2, line 18 of L specification tube, “accumulated” was changed to “accumulated” Corrected to ``I'm sorry.''& Correct "collimator lenses" in lines 2 to δ of the same page to "collimator lens", and correct "total reflection at right angles" to "reflection at right angles" in line 6 of the same page. 8. In the same page, page 16, line 6, "7 plastic" is corrected to "plastic." In the table drawings, "Figure 6 M" is corrected as shown in the attached correction diagram.

Claims (1)

[Claims] 1. In an optical head that records and/or reproduces information by projecting a light beam emitted from a light source as a spot onto a recording medium, an optical element disposed in the optical path of the light beam and its holding member. 1. An optical head comprising: an integrally formed plastic body, and at least a portion of which is treated to prevent light transmission.