JPS6247878A - Guide mechanism for optical head - Google Patents

Abstract

PURPOSE:To reduce the weight of a guide mechanism for optical head and also to eliminate the play produced between a bearing part and a guide shaft, by using the plastic to form a bearing block which supports the optical head and at the same time forming an elastic projection in a body with the bearing part of the bearing block. CONSTITUTION:A bearing block forming a guide mechanism for optical head is made of plastic and two opposite bearing parts 12 and 13 are formed together with through holes respectively. Then a guide shaft 14 is put slidably into both through holes of the parts 12 and 13. The elastic circular projections 30 and 31 are formed near the edge parts of both through holes for the shaft 14 unitedly with the end faces of both parts 12 and 13. These projections 30 and 31 generate the elastic force to the entire surface of the shaft 14 in the direction toward the center axial line of the shaft 14 when the shaft 14 is put through both through holes since the plastic projections 30 and 31 have the elastic force. As a result, the shaft 14 is supported elastically and therefore the play can be avoided between the inner walls of both through holes and the shaft 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a guide frame structure for an optical head that records or reproduces information by projecting a light beam toward a recording medium.

[Conventional technology]

2. Description of the Related Art Optical information recording and reproducing devices that record and reproduce information by emitting a light beam toward an optical recording medium such as an optical disk have been widely put into practical use. In this optical information recording/reproducing device, an optical head is equipped with a light source that emits a light beam, an optical system composed of various optical elements, a photodetector that receives a light beam from a recording medium, etc. The recording medium is supported by a guide mechanism so as to be movable, and is moved relative to the recording medium to record information at a desired position on the recording medium or reproduce information at a desired position.

In a conventional optical recording/reproducing device, the guide mechanism that slidably supports the optical head is provided with a bearing block made of a metal molded body on the optical head body, and a metal tungsten plate is attached to the bearing block.
A guide shaft is inserted through the metal bushing to support the optical hood in a slidable manner.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional optical head guide mechanism, the bearing block through which the guide shaft is inserted is made of a metal molded body, which increases the weight of the optical head and increases the inertia accordingly. A power source with a large output is required to drive the optical head in the 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, making it difficult to move the optical head to the desired track position. The disadvantage is that it takes a long time to access.

In addition, since metal molded objects cannot be molded with high precision,
It had to be supported on the guide shaft via an expensive metal bushing machined with high precision, which had the disadvantage of increasing the number of parts and increasing costs.

One possible solution to these drawbacks is to construct the bearing block from a lightweight plastic molded body. If the bearing block is made of lightweight plastic, the weight of the optical head can be reduced and problems caused by inertia can be solved, and plastic molded bodies can be molded with high precision, making it easier to connect the bearing block and bearing. It can be molded in one piece from plastic and has the advantage of eliminating the need for expensive metal bushings.

However, even if a highly precisely molded plastic body is used, there is a clearance between the guide shaft and the inner wall of the fitting portion, making it difficult to drive the optical head smoothly.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical head guide mechanism that can eliminate the above-mentioned drawbacks, reduce the weight and cost of an optical head, and drive the optical head smoothly.

[Means for solving problems]

The optical head guide mechanism according to the present invention includes a bearing that supports an optical head movably in a direction orthogonal to an information track, which records and/or reproduces information by projecting a light beam as a spot toward an optical recording medium. In a guide mechanism for an optical head comprising a main body and a guide shaft that slidably supports the bearing main body, the bearing main body is made of plastic, and the guide shaft is inserted into the bearing main body made of plastic. A through hole is provided, and an elastic protrusion is integrally molded near the edge of the through hole to restrict the position of the guide shaft inserted therein in a direction orthogonal to the central axis of the guide shaft.

[For production]

In the present invention, the bearing block provided on the optical head is made of plastic, and the bearing part of the bearing block is integrally formed with an elastic protrusion that elastically regulates the position of the guide shaft. It is possible to reduce the weight and cost of the optical head, and also to effectively eliminate looseness between the guide shaft and the inner wall surface of the bearing part, so that the optical head can be driven more smoothly along the guide shaft.

(Embodiment) Fig. 1 shows an embodiment of an optical head equipped with a guide mechanism according to the present invention, and Fig. 1A shows the configuration of a laser diode, a photodiode, an optical system, etc. arranged inside. FIG. 1B is a perspective view showing the configuration of the guide mechanism section.

As shown in FIG. 1A, 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 the polarizing film 3a, passes through the quarter-wave plate 4, and enters the objective lens 6, which is displaced by the actuator 5 in the optical axis direction and in the tracking direction orthogonal to the optical axis direction, and forms a spot on the recording medium 7. irradiated. 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 1/4 wavelength plate 4 again, and enters the polarizing prism 3. Since this light beam passes through the quarter-wave plate 4 twice, the plane of polarization rotates 906 times, 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 is incident on 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. Although the internal structure of the actuator 5 is not shown in FIG. 1A for clarity, the objective lens 6 is supported by a leaf spring so as to be movable in the direction of its optical axis and in a direction perpendicular thereto, and a focusing coil. The objective lens 6 is configured to be able to be displaced in the optical axis direction and the tracking direction by passing a current in accordance with the focusing error and the tracking error through the tracking coil. 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. Furthermore, 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 that integrally includes a laser diode 1, a collimator lens 2, a polarizing prism 3, a quarter-wave plate 4, and a detection prism 8, and an optical system that supports an actuator 5 and a photodiode 9 are used. The head body 10 is constructed from an integrally molded plastic body.

This main body 10 is made of PPS (poly phenyl sulfide), PEEK (poly ether ether ketone), PE5 (poly ether sulfone), PEI (
polyether imide), PC (polycarbonate)
, an integral molded body of plastic such as epoxy resin, or a plastic whose strength is increased by mixing these materials with fibers such as carbon fiber or glass fiber.

Such a molded body of a plastic material can be molded extremely accurately as long as the dimensional accuracy of the mold is ensured, so there is no need to perform cutting after molding to achieve dimensional accuracy. Therefore, the cutting process can be omitted from the manufacturing process, and manufacturing costs can be reduced. Furthermore, since plastic material is about 1/2 to 1/3 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 in the direction perpendicular to the information track, that is, in the radial direction of the disk-shaped recording medium, and since it can move at high speed, the access time can be shortened. I can do it.

Furthermore, since plastic materials have lower thermal conductivity than metals, it becomes difficult for the heat generated in the coil of the actuator 5 to travel through the optical head body 10 and reach the laser diode 1, effectively suppressing the temperature rise of the laser diode. can extend the life of the laser diode.

A bearing block 11 constituting a first guide mechanism is provided on one side of the optical head 10. This bearing block 11 is made of plastic like the optical head main body 10,
As shown in FIG. 1B, two "bearing parts 12 and 13 facing each other are formed. Circular through holes 12a and 13a having the same diameter and on the same axis are formed in these two bearing parts 12 and 13. The guide shaft 14 is slidably inserted into these through holes 12a and 13a.

Therefore, these through holes 12a and 13a constitute a bearing. Since the processing precision of the plastic molded body is high and the coefficient of friction on its surface is extremely small, it is sufficient to perform the function of a bearing simply by forming a circular through hole, and a metal bushing is completely unnecessary. Furthermore, a rack 15 is formed on the side surface of the substrate 11a of the bearing block 11.

This rack 15 is engaged with a binion 11 driven by a motor 16, and the entire optical head is connected to the disk-shaped recording medium 7.
It is configured to be movable over a predetermined range in the radial direction. For example, when used in a compact disc player, this movement range is about 40 mff1, and therefore the length of the rack 15 is also about 40 mm. Further, a back cover 16 is fixed to the bottom of the optical head main body 10 with screws 17.
The other end of i16 is held down by the bearing block 11. A guide portion 10a is integrally formed on one side of the optical head main body 10, and as shown in FIG.
9 will be provided. This bearing block 19 constitutes the second guide tEIHit of the optical head, and is made of a molded plastic body. A through hole 19a is formed in this bearing block 19, and a guide shaft 20 is slidably inserted into this through hole 19a. In this example, screw 1
By adjusting 8a and 18b, the optical head body 1
0 can be rotated about the guide shaft 20 in the plane of the paper of FIG. 1A, thereby making it possible to adjust the optical axis of the objective lens 6 in the tangential direction of the information track.

2A and 2B are a sectional view and a front view showing the detailed structure of the guide mechanism of the optical head. In this example, annular elastic protrusions 30 and 31 are integrally formed in the vicinity of the edge portions of the circular through holes 12a and 13a that fit with the guide shaft 14 on one end surface of the bearing parts 12 and 13, respectively. . The inner diameters of these annular elastic protrusions 30 and 31 are configured to be slightly smaller than the outer diameter of the guide shaft 14. The elastic protrusions made of plastic have elasticity, so when the guide shaft 14 having a diameter slightly larger than the inner diameter of the elastic protrusions 30 and 31 is inserted, the elastic protrusions 30 and 31 extend around the entire circumference of the guide shaft 14. An elastic force toward the center axis acts on the guide shaft 14, and as a result, the guide shaft 14 is elastically supported by the elastic protrusions 30 and 31, and the play between the guide shaft 14 and the inner wall of the through hole formed in the bearing parts 12 and 13 is eliminated. will be done.

Such elastic protrusions can be easily integrally formed by plastic molding.

FIG. 3 is a front view showing the configuration of a modified example of the guide mechanism according to the present invention. In this example, a plurality of elastic projecting pieces 40' and 41 are integrally formed in the vicinity of the edges of the through holes 12a and 13a of the bearing parts 12 and 13, which fit into the guide shaft 14, respectively. It is elastically supported over its entire circumference. By providing a plurality of such elastic protrusions in a circumferential manner, the force acting on the guide shaft 14 is dispersed, and the optical head can be driven more smoothly.

FIG. 4 shows the configuration of another modified example of the guide mechanism, and in this example, elastic protrusions 40 and 41 in the shape of a spring are integrally molded on the end surfaces on both sides of each bearing portion 12 and 13, respectively. Give an example. By forming elastic protrusions on both end faces of the bearing portion in this manner, the position of the guide shaft 14 can be more uniformly regulated.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the above-mentioned embodiment, the guide shaft is elastically pressed by an annular elastic protrusion or a plurality of elastic protrusion pieces to regulate the position of the guide shaft. It is also possible to remove backlash by providing elastic protrusions integrally with each other to elastically restrict the position of the guide shaft in one direction.

Further, there are various types of optical heads, and for example, a three-beam type head that emits three light beams as a light source can also be used. Further, as a method for detecting focusing and tracking error information, focusing errors can also be detected by an astigmatism method using a cylindrical lens.

Furthermore, the optical head main body and the bearing block can be integrally molded from a plastic molded body.

(Effects of the Invention) As explained above, according to the present invention, the bearing block that is slidably supported by the guide shaft is constructed using plastic nuts, and the position of the guide shaft inserted into the bearing portion is elastically adjusted. Since it is formed with elastic protrusions that restrict the movement of the optical head, it is possible to reduce the weight and cost of the optical head body, and the play that occurs between the bearing and the guide shaft is eliminated, allowing the optical head to slide smoothly. can be moved.

[Brief explanation of the drawing]

FIGS. 1A and B are line diagrams and perspective views showing the configuration of an embodiment of an optical head equipped with a guide mechanism according to the present invention, and FIGS. 2A and B are sectional views and front views showing the detailed configuration of the guide mechanism. 3 is a front view showing the structure of a modified example of the guide mechanism, and FIG. 4 is a front view showing the structure of another modified example of the guide mechanism. 1...Laser diode 2...Collimator lens 3...Polarizing prism 4...1/4 wavelength plate 5...
-Actuator 6...Objective lens 7...Recording medium 8...Detection prism 9...Photodiode 10...Optical head main body 11.19...Bearing block 12, 13...Bearing section 14 .20... Guide shaft 15... Rack 16... Motor 17... Binion 18a, 18b.
... Screw patent applicant Olympus Optical Industry Co., Ltd. Figure 2A Figure 3 Figure 4

Claims (1)

[Claims] 1. A bearing body that supports an optical head that records and/or reproduces information by projecting a light beam as a spot toward an optical recording medium so as to be movable in a direction perpendicular to the information track; A guide mechanism for an optical head comprising a guide shaft movably supported, wherein the bearing body is made of plastic, and the bearing body made of plastic is provided with a through hole for inserting the guide shaft, An optical head guide mechanism characterized in that an elastic protrusion is integrally molded near the edge of the through hole to regulate the position of the guide shaft inserted therein in a direction orthogonal to the central axis of the guide shaft.