JPS6240637A - Optical head - Google Patents

Abstract

PURPOSE:To decrease distortion or twisting, to attain dimension accuracy and light weight by making an optical head main body with a plastic molding of honey-comb structure having lots of throughholes. CONSTITUTION:The optical head main body 10 storing an optical system comprising a laser diode and a collimator lens or the like an actuator 5 and a photodiode 9 is formed by an incorporate molding of honey-comb structure having lots of throughholes 10x made of a plastic. When the accuracy of the dimension of a die is ensured, the accuracy of dimension of the plastic molding is kept high. Further, distortion or twisting is reduced by the honey-domb structure, light weight is attained as 5g for the head main body 10 and nearly 35g for the entire optical head.

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 tip axis and in a direction approximately perpendicular to it. The optical head body, 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 the above-mentioned 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 attached to the optical head body, and for this reason, after molding, This method requires cutting, increases the number of steps, and has the disadvantage of increasing 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.

Normally, the actuator that drives the objective lens is equipped with a coil, and a current is passed through this coil to drive the objective lens in the optical axis direction or tracking direction. Since the conductivity is high, the heat generated by the coil is transferred to the laser diode of the light source through the optical head body, which has the disadvantage of shortening the life of the laser diode. It is desirable to suppress the temperature rise of this laser diode to about 3° C. or less, and in order to meet this requirement, the magnitude of the drive current flowing to the coil of the actuator is limited, which is one of the constraints in the design of the optical head.

In order to eliminate the various drawbacks mentioned above, an optical head has been proposed in which the optical head main body is made of plastic that can be integrally molded, thereby achieving surface accuracy and dimensional accuracy as well as weight reduction.

[Problem that the invention seeks to solve]

However, in the case where the optical head body is made of the above-mentioned plastic molded body, since the plastic molded body is formed by integral molding, the inside is a solid molded product, and the optical head is subject to temperature, humidity, etc. This has the disadvantage that distortion and twisting occur in the optical head due to changes in the atmosphere to which it is exposed, significantly impairing the performance of the optical head. moreover,
If the optical head body was made thicker in order to provide strength, there was a drawback that it was not possible to reduce the weight sufficiently.

The purpose of the present invention is to eliminate the above-mentioned problems, reduce distortion and twist caused by a solid plastic molded body, and
It is an object of the present invention to provide an optical head having a lightweight and high-strength optical head body.

[Means for solving problems]

The optical head of the present invention 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, an optical system, etc. The optical head main body supporting the optical head is constructed from a plastic molded body having a large number of through holes.

[For production]

According to the above-described optical head of the present invention, since the optical head main body is constituted by a honeycomb-shaped plastic molded body having a large number of through holes, distortion and twisting of the optical head main body can be reduced. It can have rigidity and does not impair the performance of the optical head. In addition, since the optical head body is constructed from a honeycomb-structured plastic molded body, there is no need for cutting down to achieve surface accuracy and dimensional accuracy, which reduces the number of manufacturing steps, making manufacturing easier and cheaper. . Further, the weight of the optical head main body made of plastic is, for example, about 5 g, and the weight of the entire optical head is about 35 g, making it extremely lightweight. Therefore, the inertia is reduced, the movement can be performed at high speed by a low-output power source, and the access time is shortened. Additionally, honeycomb plastics have particularly low thermal conductivity, which means that the heat generated in the actuator coil is not transferred to the laser diode, extending the life of the laser and eliminating constraints on drive current, allowing greater design freedom. increases.

Further, in the present invention, as will be clear from the embodiments described below, the optical head body alone is not limited to being made of a plastic molded body, but the bearing portion,
The rack part, guide part, etc. can also be integrally molded.

〔Example〕

FIG. 1 shows the configuration of an embodiment of an optical head according to the present invention, and FIG. 1A is a diagram showing the arrangement of a laser diode, a photodiode, and an optical system arranged inside. B-E is a plan view, front view, right side view, and back view of the optical head main body, and FIG. 1F is a perspective view showing the overall structure of the optical head.

As shown in FIG. 1, a light beam emitted from a laser diode 1 constituting a light source is focused into a parallel beam by a collimator lens 2, and enters a polarizing prism 3 having a polarizing film 3a. The incident light beam is reflected by this polarizing film 3a, passes through a 174-wavelength plate 4, and enters an objective lens 6 that is displaced by an actuator 5 in the optical axis direction and in the tracking direction orthogonal thereto, and is irradiated onto the recording medium 7 as a spot. be done. In this example, it is assumed that an information track recorded on the recording medium 7 is to be reproduced. This information track 7
The reflected light beam from the recording medium 7 modulated by the information is focused by the objective lens 6, passes through the 174 wavelength plate 4 again, and enters the polarizing prism 3. Since this light beam passes through the 174-wavelength plate 4 twice, the plane of polarization rotates by 90 degrees, passes through the polarizing film 3a, and the reflective surface 8a is set at an almost critical angle with respect to the optical axis of the incident light. The light enters the detection prism 8. The light beam reflected by the reflecting surface 8a is made incident on a photodiode 9 constituting a light receiving element having a light receiving area divided into four parts.

In FIG. 1A, actuator 5 is shown for clarity of drawing.
Although the internal structure of the objective lens 6 is not shown, the objective lens 6 is supported by a leaf spring so that it can be displaced in the direction of its optical axis and in a direction perpendicular thereto, and a current corresponding to the focusing error and the tracking error is applied to the focusing coil and the tracking coil. The objective lens 6 is configured to be able to be displaced in the optical axis direction and the tracking direction by flowing. The detailed structure of such an actuator is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-94311, and is not an essential part of the present invention, so a detailed explanation thereof will be omitted. Further, a focusing error and tracking error detection mechanism including a detection prism 8 whose reflective surface 8a is set at approximately a critical angle and a light receiving element 9 divided into four parts is also disclosed in, for example, Japanese Patent Laid-Open No. 57-66533.
Since it is disclosed in the above publication, further detailed explanation will be omitted.

In this embodiment, an optical system including a laser diode 1, a collimator lens 2, a polarizing prism 3, a 174 wavelength plate 4, and a detection prism 8, and an optical head body supporting an actuator 5 and a photodiode 9 are used. 10 is constructed of a honeycomb-structured plastic molded body having a large number of through holes 10×.

FIGS. 1B to 1E show the structure of an optical head main body 10 of the present invention. This main body 10 is made of PPS (poly phenyl sulfide), PEIEK (poly ether ether ketone), PBS (poly ether sulfone), PH1 (poly ether imide), PC
(polycarbonate), epoxy resin, or a plastic whose strength is increased by mixing these materials with fibers such as carbon fiber or glass fiber.

The cross-sectional shape of the through hole 10X may be any shape such as a circle, triangle, quadrangle, hexagon, etc., but each part should be made with the same shape and dimensions to minimize distortion during molding. There is. Further, the through hole 10x may be made by machining an integrally molded plastic body using a manufacturing machine, but it is preferable to manufacture the through hole 10x at the same time as integrally molding. Furthermore, although the arrangement direction of the through-holes 10× is a direction perpendicularly penetrating from the upper surface to the lower surface of the optical head main body 10 in the above-mentioned embodiment, it is not limited to this.

Moldings made of plastic materials like this can be molded extremely accurately as long as the dimensional accuracy of the mold is ensured. There is no need to perform processing to achieve dimensional accuracy. Therefore, the cutting process can be omitted from the manufacturing process, and manufacturing costs can be reduced. moreover,
Since plastic material is about 172 to 173 times lighter than metal, the weight of the optical head can be reduced. Therefore, the optical head is moved in a direction perpendicular to the information track.
That is, a low-output power source is sufficient for driving the disk-shaped recording medium in the radial direction, and the access time can be shortened since the disk-shaped recording medium can be moved at high speed. Furthermore, plastic materials have lower thermal conductivity than metals, and in this embodiment there is an air insulating layer formed by the through hole 10 This makes it difficult to reach the laser diode, effectively suppressing the temperature rise of the laser diode, and extending the life of the laser diode.

The optical head main body 10 has a box shape as a whole and is open at the bottom. As shown in FIG. 1B, a substantially circular hole 10a is formed in the upper surface, into which the lower end of the actuator 5 fits, as shown in FIG. 1F. Further, screw holes 10b to 10e into which screws 11 for fixing the actuator 5 are screwed are formed on the top surface. Further, a step 810f is formed on the inner wall of the optical head main body 10, as shown in FIG.
Screw holes 10g and 10h are formed for fixing the lens barrel 12 (FIG. 1A) that supports the. As shown in the first diagram, a rectangular notch 1 is formed on the right side wall of the optical head main body 10.
0i is formed, and the photodiode 9 is made to face the inside of the main body 10 from this cut. On this right side wall is a plate 1 that supports the photodiode 9.
Screw holes 10j and 10k are formed for fixing 3 with screws 18.

Furthermore, as shown in FIGS. 1B and 1C, the optical head main body 1
On the front wall of 0, screw holes 101 and 101'Il are provided with screw holes 101 and 101'Il for screwing terminal boards (not shown) of lead wires connected to the laser diode 1, the coil of the actuator 5, and the photodiode 9. , On and 10
0, respectively.

Furthermore, a notch 10p for guiding these lead wires into the interior of the main body 10 is formed at the bottom edge. Furthermore, Figure 1E
As shown in the figure, a screw hole 10q for fixing the back cover 14 with a screw 15 is formed in the bottom surface. This back cover 1
The other end of 4 is held down by a bearing block 16, and screw holes 10r and 10s for fixing this bearing block to the main body 10 with screws 17 are formed. A bearing 19 is provided in the bearing block 16, and this bearing 1
9 into which the guide shaft 20 is slidably inserted. Further, a plate 21 is fixed to the upper surface of the bearing block 16, and a rack 21a is formed on the side surface of this plate. This rack 21a is engaged with a pinion 23 driven by a motor 22, so that the entire optical head can be moved over a predetermined range in the radial direction of the disk-shaped recording medium 7. For example, when used in a compact desk player, this movement range is about 40 mm, and therefore the length of the rack 21a is also about 40 mm.

An example of the optical head main body 10 is integrally formed with a guide portion 10t, and as shown in FIG. 1A, a bearing block 25 having screws 24a and 24b is provided to sandwich the guide portion 10t. A bearing 26 is attached to 25, and a guide shaft 27 is slidably inserted into this bearing 26. In this example, by adjusting the screws 24a and 24b, the optical head main body 10 can be rotated about the guide shaft 20 within the plane of the paper in FIG. Can be adjusted in the tangential direction of the track.

〔Effect of the invention〕

As is clear from the detailed explanation above, in the optical head of the present invention, since the optical head main body is constructed of a plastic molded body having a plurality of through holes, distortion and twisting of the optical head main body can be reduced. It is possible to obtain an optical head which can be made flexible and rigid, and whose performance does not deteriorate under any conditions. Furthermore, since plastic molded bodies have good surface precision and dimensional precision, cutting after molding is not necessary, reducing the number of manufacturing steps and reducing manufacturing costs. Furthermore, even if the honeycomb structured plastic molded body is made thicker to increase its mechanical strength, it is still light in weight, so the overall weight of the optical head is also reduced, and the inertia is reduced. Therefore, the output of the power source that drives the optical head in the radial direction of the disk-shaped recording medium only needs to be small, and the optical head can be moved at high speed, so that the access time is shortened and the access accuracy is improved. Furthermore, since plastic has a lower thermal conductivity than metal, the heat generated in the actuator coil is not transmitted through the optical head body to the laser diode, which can suppress the temperature rise of the laser diode and extend the life of the laser diode. becomes longer. This also allows a large current to flow through the actuator coil,
This has the advantage that restrictions on optical head design are significantly relaxed.

[Brief explanation of the drawing]

FIGS. 1A to 1F are diagrams showing the structure of an embodiment of an optical head according to the present invention. ■...Laser diode 2...Collimator lens 3...Polarizing prism 4...1/4 m long plate 5...
...Actuator 6...Objective lens 7...Recording medium...Detection prism 9...Photodiode 10...Optical head body 10X...Through hole 14...
...Back cover 16.25...Bearing block 1
9, 26... Bearing 20. 27... Guide shaft 21... Rack B 21a -... Rack 22... Motor 23... Pinion Master Applicant Olympus Optical Industry Co., Ltd. Continued from page 1 Akira Hideyuki Komamura 2nd Hatagaya Co., Ltd., Shibuya-ku, Tokyo Takashi Hirayama 1) Kazuyuki Kazuyuki 2nd Hatagaya Co., Ltd., Shibuya-ku, Tokyo Takashi Hirayama

Claims (1)

[Claims] 1. A light source, an objective lens that projects the light beam emitted from this light source as a spot onto a recording medium, an actuator that drives this objective lens in the optical axis direction and a direction approximately perpendicular thereto, and an optical head that supports the optical system, etc. An optical head characterized in that a main body is made of a plastic molded body having a large number of through holes.