JPH08161755A - Objective lens mechanism - Google Patents

Abstract

PURPOSE: To effectively measure and adjust inclination by providing a deformation member consisting of a complex of bimetal, shape memory alloy, and an elastic material between an objective lens and an objective lens holder and giving thermal energy to the deformation member. CONSTITUTION: By giving the same amount of thermal energy to both deformation members 21a and 21b consisting of a complex of bimetal, shape memory alloy, and elastic member, an objective lens 6 can be inclined in the direction of an arrow C. With the amount of inclination of the objective lens, by measuring the shape of beams emitted from the objective lens and an angle for the reference surface of the assembly of a flange part 6b by an observation device, the angle can be adjusted to an optimum value. After the adjustment, by adhering and fixing the objective lens 6 to an objective lens holder 6a, the adjustment operation of the inclination of the objective lens can be completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens mechanism of an optical pickup device used for recording, reproducing and erasing information on a magneto-optical disk by irradiating a laser beam.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a magneto-optical disk device which is the background of the present invention. Magneto-optical disk 1
Is rotatably driven by a motor 2, and after a laser beam 7 emitted from a laser light source 3a is reflected by a mirror 3b, it passes through an objective lens 6 and converges on the surface of a disc recording medium 1a incorporated in a magneto-optical disc 1. By doing so, recording, reproducing or erasing of information is performed. The convergence position of the laser light 7 is controlled on the recording track of the disk recording medium 1a by moving the objective lens 6 vertically and horizontally by the objective lens driving device 4. Laser light source 3a and mirror 3b
An optical system such as is housed in a housing 3, and the housing 3 and the objective lens driving device 4 constitute an optical pickup device (optical head). 5 is the recording of information,
It is an electromagnet coil for erasing.

In the above-described magneto-optical disk device, when the objective lens 6 is attached so as to be inclined with respect to the optical axis 7a, an aberration occurs in the laser light traveling from the objective lens 6 to the magneto-optical disk 1 and the laser light is emitted. 7 is not sufficiently converged, and there is a problem in that information comrades on adjacent tracks cause crosstalk. In order to solve this problem, a spacer 8 is interposed between the objective lens driving device 4 and the housing 3 in order to solve this problem. However, the objective lens 6 is adjusted so as not to be tilted with respect to the optical axis 7a. Further, as shown in FIG. 8, a spherical seat 9a is provided on the upper surface of the housing 3, and a spherical projection 9b is provided on the bottom of the objective lens driving device 4 to tighten the screw 10.
Alternatively, the adjustment is performed by injecting an adhesive into the spherical seat 9a.

Japanese Patent Laid-Open No. 4-113521 discloses a method of adjusting the objective lens itself by an inclination adjusting mechanism and then adhering it instead of adjusting the inclination of the entire objective lens driving device.

[0005]

However, in the structure in which the tilt of the objective lens is adjusted by interposing the spacer as shown in FIG. 7, the work of measuring the tilt of the objective lens 6 and the work of tilting cannot be performed at the same time. However, there is a problem in that the work of inserting the spacer takes time because the work of tightening and removing the screw is repeated. Further, as shown in FIG. 8, in the structure in which the spherical projection and the spherical seat are provided to adjust the inclination of the objective lens, the height dimension 12 is necessary for the spherical seat to take a space, and the device can be made thin. It is a disadvantage. On the other hand, in the example disclosed in Japanese Patent Laid-Open No. 4-113521, the objective lens is adjusted from the outside by the tilt angle adjusting device, but since the structure supporting the objective lens is a movable body, an external force may act even a little. It may move.

Further, in order to make the apparatus thinner, it is conceivable to provide an objective lens height adjusting mechanism in addition to the tilt adjusting mechanism. This is because the range of movement of the actuator in the focus direction is mainly determined by the amount of surface vibration of the disc and the assembly error in the focus direction of the actuator, pickup, etc., and these assembly errors are adjusted by adjusting the height of the objective lens. This is because the range of movement of the actuator in the focus direction is reduced and the actuator can be designed in a small size by eliminating it. Regarding this height adjustment, conventionally, the reference surface height of the turntable on the spindle motor that mounts the disc and the focal position of the objective lens are measured, and the assembly error of the actuator, pickup, etc. is calculated and the thickness corresponding to the error is calculated. There is a method of laying the spacers on the spindle motor or a method of absorbing the error by providing a turntable height adjusting mechanism applying a screw to the spindle motor mounting portion. However, again, the work of inserting the spacer takes time because the work of tightening and removing the screw is repeated.
Further, since the height adjusting mechanism of the spindle motor using the screw can be used only for the spindle motor having a special structure such that the motor shaft makes a metal contact with the base or the like, there is a problem that the application is not effective.

[0007]

In view of these problems, the present invention provides an objective lens mechanism of an optical pickup device which records, reproduces, and erases information on a magneto-optical disk by irradiating a laser beam. Comprises an objective lens holder, a deformable member having one end fixed to the objective lens holder and supporting the objective lens at the other end, and an objective lens supported by the deformable member, wherein the deformable member is given thermal energy And the inclination of the objective lens can be adjusted by the deformation.

[0008]

With the above-described structure, in the objective lens mechanism of the present invention, the height of the supporting point of the objective lens supported by the deformable member can be changed by applying heat energy to the deformable member during adjustment, and the objective lens It can be tilted to fit the optical axis.

Further, by adopting a structure in which the objective lens is supported by three or more deforming members, the height of the supporting point of the objective lens supported by the deforming members is increased by applying thermal energy to the deforming members during adjustment. Instead, the objective lens can be tilted to match the optical axis, and at the same time, the height of the objective lens can be adjusted so as to absorb an assembly error in the focusing direction of the actuator, the pickup, and the like.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of an objective lens driving device according to the objective lens mechanism of the present invention. The objective lens 6 is held by an objective lens holder 6a, and the objective lens holder 6a is supported by a parallel plate spring 13 for focus movement, and when the objective lens 6 is bent, the arrow F, which is the optical axis direction of the objective lens 6, is provided. It can swing in any direction. The focus movable parallel leaf spring 13 is connected to the intermediate support 14, and the intermediate support 14 is supported by the radial movable leaf spring 16 fixed to the columnar protrusion 15 a of the base 15.
The intermediate support 14 and the objective lens holder 6a can swing in the arrow R direction which is the radial direction.

Further, since the focus drive coil 17 and the radial drive coil 18 wound on the objective lens holder 6a cross the magnetic flux generated in the gap 19a of the magnetic circuit 19, when each coil is energized, the arrow F
In addition, a force is generated in the R direction, and the objective lens holder 6a and the objective lens 6 can be moved in that direction. In such an objective lens driving device, a method of supporting the objective lens 6 will be described in more detail.

FIG. 2 is a view showing only the objective lens 6 and the objective lens holder 6a in FIG.
2A is a plan view, FIG. 2B is a side view, and FIG. 2C is a sectional view taken along line XX in FIG. Deformation member 21a,
21b is made of a bimetal that deforms when heat energy is applied, or a material in which a shape memory alloy and an elastic body are bonded together, and one end thereof is fixed to the objective lens holder 6a. In this embodiment, the deformable member 21
2a is provided by applying heat energy.
The description will be made assuming that it bends in the direction of arrow A shown in (c). The objective lens 6 is supported by its flange portion 6b by the projecting portion 20 provided on the objective lens holder 6a and the deformable members 21a and 21b. The deformable members 21a and 21b are independently given thermal energy, and the amount of bending can be adjusted depending on the amount of thermal energy. For example, the deformable members 21a, 21
If the same amount of heat energy is applied to both b, the objective lens 6 can be tilted in the direction of arrow B in FIG. 2C, and if more heat energy is applied to the deforming member 21a than to the deforming member 21b. The objective lens 6 can be tilted in the direction of arrow C in (b). Regarding the amount of tilt of this objective lens,
The shape of the beam emitted from the objective lens or the angle of the flange portion 6b with respect to the reference plane (not shown) for assembly can be adjusted to an optimum angle by measuring with an observation device (not shown). After this adjustment, the objective lens 6 is adhered and fixed to the objective lens holder 6a to complete the inclination adjustment work of the objective lens.

FIG. 1 shows a case of irradiating a laser beam as a means for giving the above-mentioned thermal energy. The heating laser beams 100a and 100b are radiated onto the deformable members 21a and 21b, respectively. The tilt angle of the objective lens can be adjusted by adjusting the thermal energy given by the amount of light.

FIG. 3 shows another embodiment as means for giving the above heat energy, which utilizes Joule heat due to electric current. The deformable members 21c and 21d are U-shaped, and the conductive wires 22a and 22b are provided. By energizing these, Joule heat is generated and the deformable members 21c, 21
This is an example in which the temperature of d is raised and deformed to adjust the inclination.

Next, FIG. 4 shows a case where three deforming members are provided in the objective lens mechanism and the objective lens is supported only by the deforming members. FIG. 4 (a) is a plan view and FIG.
4B is a side view, and FIG. 4C is XX in FIG. 4A.
It is sectional drawing. Objective lens support members 21a, 21b, 2
Reference numeral 1c is made of a bimetal that deforms when heat energy is applied, or a material in which a shape memory alloy and an elastic body are bonded together, and one end thereof is fixed to the objective lens holder 6a. Objective lens support members 21a, 2
Heat energy is applied to each of 1b and 21c independently, and the amount of bending can be adjusted depending on the amount of heat energy. Figure 5,
FIG. 6 shows an example in which heat energy is supplied by a laser beam, and the amount of heat energy given by the amount of light is adjusted,
The tilt and height of the objective lens can be adjusted. When the objective lens 6 is inclined by the angle θ with respect to the optical axis 7a as shown in FIG. 5A, the objective lens support members 21a, 21b and 21c are provided.
With respect to the laser beam 100a,
100b and 100c are adjusted and given as shown in FIG. 5B, and the inclination of the objective lens 6 with respect to the optical axis 7a is adjusted as shown in FIG. 5C. The tilt amount of the objective lens is adjusted by measuring the shape of the beam emitted from the objective lens or the angle of the flange portion 6b with respect to the reference plane (not shown) for assembly with an observation device (not shown). be able to. After this adjustment, the objective lens 6
Is bonded and fixed to the objective lens holder 6a, and the tilt adjustment work of the objective lens is completed.

Further, as shown in FIG. 6A, the assembling error in the focus direction of the actuator and the pickup is Δ.
6B, the laser beams 100a, 100b and 100c are applied to the objective lens supporting members 21a, 21b and 21c so as to eliminate the assembly error Δ.
The height of the objective lens 6 is adjusted as shown in FIG. 6C. At that time, if a mirror is provided at the turntable reference height 30 and the height of the objective lens is adjusted so that the mirror is located at the focal point 31 of the objective lens, the mirror surface of the semiconductor laser light source inside the mirror and the pickup (see FIG. (Not shown) forms a resonator and the output of the semiconductor laser light source increases. This output is the stray light detector inside the pickup (not shown)
By monitoring with, the completion of the height adjustment of the objective lens can be seen. After this adjustment, the objective lens 6 is moved to the objective lens holder 6a.
Then, the work for adjusting the height of the objective lens is completed.

The tilt adjustment work and the height adjustment work of the objective lens can be simultaneously performed by adjusting the heat input amount of the laser.

As means for applying heat energy to the deformable member, a Joule heat is generated by providing a conductive wire to the deformable member to energize the deformable member to raise the temperature of the supporting member and adjust the inclination and height of the objective lens. You can also do it.

[0020]

According to the present invention, a deforming member that is deformed by heat is provided between the objective lens and the objective lens holder, and the deforming member is deformed by applying heat energy to the deforming member to adjust the inclination of the objective lens. When adjusting the tilt, external force does not act on the movable part of the objective lens driving device including the objective lens and the objective lens holder, and the focus movable leaf spring and the radial movable leaf spring supporting the movable portion are not deformed. Therefore, the movable part does not move. Therefore, the tilt angle can be easily measured even when the objective lens is tilted, which allows the measurement and the adjustment to be performed at the same time, which improves the workability in the adjustment. Furthermore, by performing adjustment by energization or laser irradiation, adjustment work can be performed without directly touching small parts, and automation is easy. Further, since the thin deformable member is interposed between the objective lens and the objective lens holder, it does not cause a large thickness, which is advantageous for miniaturization of the pickup and the magneto-optical disk device. Also,
By forming the deformable member with a bimetal or a composite of a shape memory alloy and an elastic material, it is possible to increase the amount of displacement with respect to the amount of heat applied compared to mere thermal expansion, and to increase the adjustment range.

Further, by providing three or more objective lens supporting members which are deformed by heat between the objective lens and the objective lens holder, and by supporting the objective lens by the structure, heat energy is externally applied to the supporting members. By giving the support member, the support member is deformed to adjust the inclination of the objective lens, and at the same time, the height of the objective lens can be adjusted, thereby improving the efficiency of the adjustment work. Further, since it serves as both the tilt adjusting mechanism and the height adjusting mechanism, there is no need for any other mechanism for adjusting the height, which is advantageous for downsizing the pickup and the magneto-optical disk device.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an objective lens mechanism according to the present invention.

FIG. 2 is a diagram showing a configuration of an objective lens, an objective lens holder, and a deformable member in FIG.

FIG. 3 is a diagram showing another configuration of the deformable member in FIG.

FIG. 4 is a diagram showing another configuration of an objective lens, an objective lens holder, and a deformable member.

FIG. 5 is a diagram illustrating an inclination adjusting operation of an objective lens according to the present invention.

FIG. 6 is a diagram illustrating the height adjusting operation of the objective lens according to the present invention.

FIG. 7 is a diagram showing a conventional objective lens adjusting mechanism.

FIG. 8 is a diagram showing a conventional objective lens adjusting mechanism.

[Explanation of symbols]

 6 Objective Lens 6a Objective Lens Holder 6b Flange 13 Focus Moving Leaf Spring 16 Radial Moving Leaf Spring 17 Focus Driving Coil 18 Radial Driving Coil 20 Projection 21 Deformation Member 22 Conductive Wire 100 Laser Beam

Claims (1)

[Claims] 1. An objective lens mechanism of an optical pickup device for recording, reproducing and erasing information on a magneto-optical disc by irradiating a laser beam, wherein an objective lens holder and one end fixed to the objective lens holder and the other end objective. A deformable member that supports the lens and an objective lens that is supported by the deformable member. The deformable member is deformed by being given heat energy, and the inclination of the objective lens can be adjusted by the deformation. Objective lens mechanism.