JPH1069665A - Optical head device - Google Patents

Abstract

(57) [Problem] To provide a lens holder having sufficient rigidity and a high resonance frequency of its own while maintaining a light weight even when an optical disk device becomes smaller and thinner, thereby improving focusing and tracking control. Provided is an optical head device that performs with high accuracy. SOLUTION: A part of a lens holder 2 for holding an objective lens 1 in an optical disk device is made of magnesium, and the magnesium part and a synthetic resin are integrally molded to form a lens holder 2. The contact surface of the lens holder 2 with the supporting member 8 that movably supports the lens holder 2 is made of synthetic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used for an optical disk device, and more particularly, to a lens holder for holding an objective lens.

[0002]

2. Description of the Related Art In an optical disk device for driving an optical recording medium such as an optical disk or a magneto-optical disk, an optical head is used as means for recording and reproducing information. The optical head includes a light source such as a semiconductor laser, and condenses a light beam emitted from the light source on an information recording surface of a medium via an objective lens, and also reflects a light beam reflected from the information recording surface. Recording and reproduction of information are performed by detection by a light detection element via an objective lens.

In such an optical head, an objective lens and a lens holder for holding the objective lens are integrally formed in the direction of the optical axis of the objective lens (focusing direction) and the direction orthogonal to the optical axis (tracking direction). A mechanism for displacing is provided. By such a mechanism, the light beam is controlled so as to accurately scan the recording track on the information recording surface of the medium.

As a material of a lens holder for holding an objective lens, a synthetic resin is generally used from the viewpoint of cost.

[0005]

In controlling the focusing direction and the tracking direction in the optical disk device, it is desired that resonance is not generated at a frequency lower than a specific frequency. However, when the lens holder is made thinner in accordance with the demand for smaller and thinner optical disk devices, the rigidity of the lens holder made of synthetic resin is insufficient, and the resonance of the lens holder itself becomes low. There is a problem that can not be performed. Also, when it is necessary to increase the frequency range where there is no resonance in accordance with the demand for higher density of the optical disk device, the resonance of the lens holder itself becomes a problem.

The present invention has been made in view of such circumstances, and even if an optical disk device is reduced in size and thickness, it is provided with a lens holder having sufficient rigidity and a high resonance frequency of its own, and is provided with a focusing direction. It is another object of the present invention to provide an optical head device capable of controlling a tracking direction with high accuracy.

[0007]

According to the present invention, there is provided an optical head device comprising a lens holder for holding an objective lens, wherein the lens holder is made of magnesium and synthetic resin. It is characterized by.

In the optical head device of the present invention, magnesium is used for a part of the lens holder, and the lens holder is composed of magnesium and a synthetic resin. In this case, a magnesium portion is used as a core, and the core is integrally formed of a synthetic resin.

As described above, in the lens holder according to the present invention, since magnesium is partially used, sufficient rigidity can be obtained as compared with the conventional example in which the whole is made of a synthetic resin even if it is thin. Further, since magnesium, which is a light metal, is used, it is lighter than when other metals are used. The rigidity of the lens holder is related to the ratio between the Young's modulus and the density of the material forming the lens holder, and the weight is related to the density of the material forming the lens holder. In FIG.
The Young's modulus E and the density ρ of four kinds of substances (magnesium, aluminum, iron, and synthetic resin (PPS: polyphenyl sulfide)) are shown.

Magnesium has a density of 1.74 g / cm ³ , which is not much different from the density of synthetic resin PPS of 1.66 g / cm ³ , but its Young's modulus is 4.23 × 10 ¹⁰ Pa
Which is much larger than the Young's modulus of the synthetic resin PPS of 1.5 × 10 ¹⁰ Pa. Magnesium has a smaller density than other metals such as aluminum and iron, but there is no great difference in the ratio between Young's modulus and density. Therefore, in the lens holder of the present invention in which magnesium is partially used, the rigidity can be increased while the weight is reduced.

By the way, since synthetic resin is more workable than metal, synthetic resin is used for a part of the lens holder of the present invention that requires high dimensional accuracy, for example, a part for mounting an objective lens. The contact surface of the support member made of an elastic material for supporting the lens holder is made of a non-conductive synthetic resin, so that the support member and the lens holder are electrically insulated from each other, and the second surface for focusing control is formed. Electrical conduction between the first electromagnetic coil, the second electromagnetic coil for tracking control, and the support member can be achieved. Further, by forming the magnesium portion into a structure having a constriction or a projection, strong bonding with the synthetic resin portion can be achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

FIG. 1 is a perspective view showing the structure of an optical head device according to the present invention. In FIG. 1, reference numeral 10 denotes a flat, flat base. At the longitudinal end of the base 10, two fixing members 9 are provided at predetermined intervals in the width direction. Reference numeral 1 denotes an objective lens, and the objective lens 1 is mounted and supported on a lens holder 2. Lens holder 2
Is a focusing coil 3 for driving the objective lens 1 and the lens holder 2 integrally in the optical axis direction (focusing direction) of the objective lens 1, and the light of the objective lens 1 integrating the objective lens 1 and the lens holder 2. A pair of tracking coils 4 for driving in a direction perpendicular to the axis (tracking direction) are provided on both sides of the objective lens 1. A magnet 5 and a yoke 7 are arranged corresponding to the focusing coil 3 and the tracking coil 4.

The lens holder 2 includes a support member 8 composed of a total of four wires, two of which are fixed at one end to each fixing member 9.
, So as to be movable in the focusing direction and the tracking direction. Further, below the lens holder 2, a rising mirror 6 for guiding a light beam from a light source (not shown) to the objective lens 1 is provided.

The light beam emitted from the light source is reflected by the rising mirror 6, guided to the objective lens 1, and applied to a recording medium (not shown). At this time, a current is supplied to the focusing coil 3 to displace the lens holder 2 in a direction parallel to the optical axis, so that focusing control is performed, and
An electric current is supplied to the tracking coil 4 so that the lens holder 2
Is displaced in a direction orthogonal to the optical axis to perform tracking control.

FIG. 2 is a perspective view of the lens holder 2 shown in FIG. 1, which is a feature of the present invention. Lens holder 2
Has a substantially H-shape in plan view, and a hole 22 for mounting the objective lens 1 is formed in the center of the horizontal bar portion 21. Further, the horizontal bar portion 21 slightly protrudes from the two vertical bar portions 23 to form a protruding portion 24. The other end of the support member 8 (wire) is attached to the protrusion 24.

The lens holder 2 is formed by integrally molding a magnesium core 25 (shown by a broken line in FIG. 2) with a synthetic resin. FIG. 3 is a perspective view of the core 25.
Shown in The core portion 25 has an H-shape obtained by reducing the lens holder 2 to a substantially similar shape, and a hole 26 having substantially the same diameter as the hole 22 is provided at the center thereof.
Are formed. The lens holder 2 is formed by molding the periphery of the core portion 25 with a synthetic resin. However, the projecting portion 24 to which the support member 8 is attached does not contain magnesium, and is entirely made of a synthetic resin.

Such a lens holder 2 can be easily manufactured by molding a magnesium core portion 25 by die casting or by sheet metal, and integrally molding the core portion 25 and a synthetic resin. Mass production is also possible at low cost. A hole 22 for mounting the objective lens 1 is provided.
In the vicinity of, and the parts requiring dimensional accuracy, such as the protruding part 24 to which the support member 8 is attached, are difficult to manufacture by die casting of magnesium. I can do it.

In the optical head device of the present invention, as described above, a part of the lens holder 2 (the broken line in FIG. 2 and the core part 25 shown in FIG. 3) is made of magnesium, and the part and the synthetic resin are integrated. Since the lens holder 2 is formed by molding, the rigidity of the lens holder 2 can be increased as compared with the conventional example, and the resonance frequency can be increased. Further, since the metal used is low-density magnesium, the weight can be kept low as in the conventional example, and there is no need to supply a large current to the focusing coil 3 and the tracking coil 4 when driving the lens holder 2. .

FIG. 4 shows the measurement results of the frequency characteristics of the gain and phase in the focusing direction in the optical head device of the present invention provided with the lens holder 2 partially using magnesium as described above. As a comparative example, FIG. 5 shows a similar measurement result in a conventional optical head device including a lens holder made of only synthetic resin. 4 and 5, it can be seen that the higher order resonance frequency is higher when magnesium is added. Therefore, as a result, in the optical head device of the present invention, focusing control and tracking control can be performed with high accuracy.

In this embodiment, since the contact surface (projection 24) between the support member 8 and the lens holder 2 is made of a synthetic resin having no conductivity, each terminal of the focusing coil 3 and the tracking coil 4 is formed. By connecting the terminals of the conductive support member 8 with the respective terminals, electrical conduction can be achieved. Therefore, when the support member 8 is energized, an electric current flows through the focusing coil 3 and the tracking coil 4 to perform both the focusing control and the tracking control.

If the focusing coil 3 and the tracking coil 4 are simultaneously formed integrally with the lens holder 2, the rigidity is increased and the number of steps is reduced. Further, if the support member 8 is also integrally formed, the number of steps can be further reduced.

Although the shape of the magnesium core 25 in the lens holder 2 is H-shaped, this is merely an example, and other shapes may be used. 6 to 9 show perspective views of a core portion 25 having another shape. FIG. 6 shows an example of a core 25 having a square shape, FIG. 7 shows an example of a core 25 having a U shape, FIG. 8 shows an example of a core 25 having an I shape, and FIG. 9 shows an L shape. Core part
25 examples are shown, and each example has the same effect as the example of FIG.

FIGS. 10 and 11 are perspective views showing still another example of the core portion 25 made of magnesium. In the example shown in FIG. 10, a constriction 30 is formed in a part of a core 25 which is entirely H-shaped. In the example shown in FIG. 11, a projection 31 is formed on a part of the core 25 which is entirely H-shaped. In this way, the magnesium core 25 is constricted 30 or the projection 31
With such a structure, the bond with the synthetic resin portion can be strengthened.

Although a wire is used as the elastic material of the support member 8 in the example shown in FIG. 1, a leaf spring may be used. Further, as a method of supporting the lens holder 2, a configuration is adopted in which a support member made of an elastic material movable in the focusing direction and a support member made of an elastic material movable in the tracking direction are connected via an intermediate portion. May be. Further, in the example of FIG. 1, the focusing coil 3 and the tracking coil 4 are provided as a pair on both sides of the objective lens 1, but may be provided on only one side.

[0026]

As described above, in the optical head device of the present invention, a part of the lens holder for holding the objective lens is made of magnesium, and the lens holder is made of magnesium and synthetic resin, so that the weight is reduced. The rigidity of the lens holder can be increased while focusing and tracking can be controlled with high accuracy.

Further, since the contact surface of the lens holder with the support member is made of a non-conductive synthetic resin, electrical conduction between the focusing coil and the tracking coil and the support member can be achieved. In addition, since there is a constriction or projection on the magnesium part of the lens holder,
Strong bonding with the synthetic resin portion can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an optical head device according to the present invention.

FIG. 2 is a perspective view of a lens holder in the optical head device of the present invention.

FIG. 3 is a perspective view of a magnesium core part of the lens holder.

FIG. 4 is a graph showing a measurement result of a frequency characteristic in a focusing direction in the optical head device according to the present invention.

FIG. 5 is a graph showing measurement results of frequency characteristics in a focusing direction in a conventional optical head device.

FIG. 6 is a perspective view showing another example of a magnesium core part of the lens holder.

FIG. 7 is a perspective view showing still another example of a magnesium core portion of the lens holder.

FIG. 8 is a perspective view showing still another example of a magnesium core portion of the lens holder.

FIG. 9 is a perspective view showing still another example of the magnesium core of the lens holder.

FIG. 10 is a perspective view showing still another example of a magnesium core portion of the lens holder.

FIG. 11 is a perspective view showing still another example of a magnesium core part of the lens holder.

FIG. 12 is a table showing Young's modulus and density in four kinds of substances.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Focusing coil 4 Tracking coil 8 Support member 24 Projection part 25 Core part 30 Constriction 31 Projection

Claims (1)

[Claims] 1. An optical head device comprising a lens holder for holding an objective lens, wherein the lens holder is made of magnesium and synthetic resin.