JPH06338070A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To provide a stable control system and to prevent life from deteriorating by supporting a movable part with leaf springs to eliminate contact parts without generating friction force and friction dust at the time of performing focusing control and tracking control. CONSTITUTION:The leaf springs 116a and 116b are fixed to a supporting shaft 103 by their inner circumferential parts and to a lens holder 110 by their outer circumferential parts, having an approximately conentric shape with the supporting shaft 103. Then, the leaf springs 116a and 116b are easily positioned to the supporting shaft 103 in the axial direction by a step provided on the supporting shaft 103. Now, at the time of correcting focus displacement of a converged spot 114, an objective lens 111 is driven by electromagnetic force generated by magnets 104a and 104b to perform this correction. Then, as to track-jumping of the converged spot 114, the springs 116a and 116b are deformed into spiral shapes, and then tracking control is performed on the objective lens 111. Moreover, at this time, because of no occurrence of friction dust, deterioration of life is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device mounted on an optical head device for optically recording or reproducing information on an optical information recording medium.

[0002]

2. Description of the Related Art FIG. 11 is a perspective view of a main part of a conventional objective lens driving device shown as a conventional example in Japanese Examined Patent Publication No. 63-53618, and FIG. 12 is a sectional view taken along the line AA of FIG. Is.

In the figure, reference numeral 1 is a base made of a magnetic material, and a shaft 2 is fixed to the central portion of the upper surface. 3 is the shaft 2
The shaft is fitted and held by the shaft 2 and is fixed to the holding cylinder 4 by a bearing cylinder that constitutes a sliding bearing mechanism. 4a is an objective lens 5
The bottom wall 4b for supporting the cylindrical portion 8a, 8b has a focusing coil 6 and a tracking coil 7 fixed to the outer periphery.
Reference numeral b denotes an inner yoke (not shown), 9a and 9b denote outer yokes, and the permanent magnet 10 is bonded and fixed between the outer yokes 9a and 9b and the base 1.

Reference numeral 11 denotes a small shaft that is erected on the upper surface of the base 1, and a neutral position setting damper member 12 formed of rubber or the like is provided between the bearing shaft 3 and the bearing cylinder 3. Reference numeral 13 is a light passage hole for guiding the light incident on the objective lens 5.

Next, the operation will be described. By controlling energization of the focusing coil 6, the position of the holding cylinder 4 is driven in the Y-axis direction in FIG. 11 to perform focusing control. Further, by energizing the tracking coil 7, the position of the holding cylinder 4 is driven in the X-axis direction in FIG. 11 to perform tracking control.

[0006]

However, the conventional objective lens driving device constructed as described above has the following problems. That is, since the slide bearing mechanism is constituted by the shaft 2 and the bearing sleeve 3, a frictional force is generated between the shaft 2 and the bearing sleeve 3 during focusing drive and tracking drive, and the frictional force acts as a non-linear element. In some cases, the control system became unstable.

Further, due to the relative contact movement between the shaft 2 and the bearing sleeve 3, wear is generated, and the scattering of the wear has an optical adverse effect on the objective lens and the optical disk, and the life of the sliding bearing mechanism portion is also increased. There is also a problem that it lowers.

The present invention has been made to solve the above problems, and when performing focusing control or tracking control, a frictional force is generated, a stable control system can be obtained, and wear is generated. An object of the present invention is to obtain an objective lens driving device that does not cause optical adverse effects or shortening of the life of the peripheral portion.

[0009]

An objective lens driving device according to the present invention comprises an objective lens for converging a light beam on an optical disk, a lens holder having the objective lens fixed at one end, and an optical lens for the objective lens. A support shaft having an axis parallel to the axis and a set of planes that are perpendicular to the support shaft and are separated from each other by a certain amount in the axial direction. The support shaft has an inner circumference and the lens has an outer circumference. A pair of leaf springs having a substantially concentric shape with respect to the axis fixed to the holder are arranged.

A balance weight is provided at the other end of the lens holder so that the position of the center of gravity of the movable portion composed of the objective lens, the lens holder and the like is located on the support shaft.

Further, the leaf spring is provided with a bent portion which constitutes a plane portion including the axis of the support shaft.

Further, the above two leaf springs are connected to each other.

Further, an elastic member is provided between the inner peripheral portion of the leaf spring and the support shaft.

[0014]

A pair of leaf springs having a concentric shape with respect to the support shaft deforms like an umbrella when the objective lens is driven in the focusing direction, and is centered on the support shaft when driven in the tracking direction. The lens holder is supported so that it can be driven and controlled in the focusing direction and the tracking direction of the objective lens by being deformed into a spiral shape.

Further, since the position of the center of gravity of the movable part is on the support shaft, no rotational moment about the support shaft is generated with respect to the movable part when seeking the optical disk.

Further, the bent portion of the leaf spring suppresses an unnecessary torsional resonance mode of the leaf spring particularly during drive control in the tracking direction.

Further, the mutually coupled leaf springs reduce variations in the spring constant of the leaf springs.

Further, the elastic member disposed between the inner peripheral portion of the leaf spring and the support shaft reduces the resonance peak of the leaf spring, and particularly the spring constant of the leaf spring in the tracking direction tends to increase. It becomes easy to set the constant to a desired value.

[0019]

【Example】

Example 1. 1 is an exploded perspective view of a main part of an objective lens driving device according to a first embodiment of the present invention, FIG. 2 is a plan view of the main part of FIG. 1, FIG. 3 is a cross-sectional view of the main part of FIG. 1, FIG. 5 is a cross-sectional view of an essential part showing a driving state in the focusing direction of the objective lens driving device of FIG. 1, and FIG. 6 is a detailed view showing the shape of the leaf spring part of FIG.

1 to 6, reference numeral 101 denotes a base, which has a light flux passing hole 101a on the bottom surface thereof so that a light beam 102 emitted from a light source (not shown) can enter from the bottom surface. The lower end portion of the support shaft 103 is held by the fixing hole portion 101b. The focusing magnets 104a and 104b are vertically magnetized, and are fixed to the base 101 together with the focusing yokes 105a and 105b.

Reference numerals 106a and 106b denote tracking magnets which are magnetized in two poles in the left and right directions, and tracking yokes 107a and 107b are provided on the back surfaces thereof.

Reference numeral 110 denotes a lens holder formed of a plastic material, 111 denotes an objective lens fixed to one end of the lens holder 110 in the longitudinal direction, and the light beam 102 is focused on the medium surface 113 of the optical disk 112 to form a focused spot 11.
Focus as 4.

The inner peripheral portions of 116a and 116b are supporting shafts 10.
3 is a set of leaf springs whose outer peripheral portion is fixed to the lens holder 110 and which is substantially concentric with the support shaft 103. Leaf springs 116a, 116 for the support shaft 103
The positioning of b in the axial direction can be easily performed by the step provided on the support shaft 103. 117 is a leaf spring 11
Lens holder 1 so as to be coaxial with 6a and 116b
The focusing coil is fixed with respect to 10, and is arranged at a position facing the focusing yokes 105a and 105b. Reference numerals 118a and 118b denote tracking coils that are adhesively fixed to both side surfaces of the lens holder 110.

Next, the operation will be described. When correcting the focus shift of the focused spot 114, a desired current is applied to the focusing coil 117, and the lens holder 110 is generated by an electromagnetic force obtained by the interaction with the magnetic force generated by the focusing magnets 104a and 104b.
Is moved along the support shaft 103 to drive and control the objective lens 111 in the direction of arrow A in the figure to control the focusing direction.

When correcting the track shift of the focused spot 114, the tracking coils 118a and 11a are used.
A desired current is applied to 8b, and the leaf springs 116a and 116b are deformed in a spiral shape around the support shaft 103 by the electromagnetic force obtained by the interaction with the magnetic force generated by the tracking magnets 106a and 106b, and the lens holder 110 is rotated. Is rotated in the direction of arrow B in FIG. 2 to control the tracking direction of the objective lens 111.

Example 2. 7 is a sectional view of an essential part of an objective lens driving device according to a second embodiment of the present invention, in which the same reference numerals as those in FIG. 3 denote the same parts, and 115 is an objective lens 111 arranged in the longitudinal direction of the lens holder 110. It is a balance weight fixed to one end that is not provided, and is arranged such that the center of gravity of the movable portion composed of the lens holder 110 and the like is arranged on the support shaft 103.

In the second embodiment, the dynamic balance in the rotation direction about the support shaft 103 is ensured, and even when the objective lens driving device performs the seek operation on the optical disk 112, the rotation moment is generated in the movable portion. There is an advantage that it does not occur and unnecessary residual resonance does not occur after seek.

Example 3. FIG. 8 is an enlarged perspective view of a leaf spring of the objective lens driving device according to the third embodiment of the present invention. In the third embodiment, an example is shown in which the leaf springs 119a and 119b have bent portions 119c and 119d that are not only in a plane perpendicular to the support axis but also out of the plane. With this shape of leaf spring, it is possible to suppress an unnecessary torsional resonance mode of the leaf spring particularly during drive control in the tracking direction.

Example 4. FIG. 9 is an enlarged perspective view of a leaf spring of the objective lens driving device according to the fourth embodiment of the present invention. In the fourth embodiment, an example in which two leaf springs are connected to each other is shown. Since the leaf spring 120 of this shape can independently manage the spring constants in the focusing direction and the tracking direction, it is possible to suppress variations in the frequency characteristics of the objective lens driving device and improve mass productivity.

Example 5. 10 is a plan view of a main part of an objective lens driving device according to a fifth embodiment of the present invention, and the same reference numerals as those in FIG. 2 denote the same parts. The fifth embodiment shows an example in which the elastic member 122 is arranged between the inner peripheral portions of the leaf springs 121a and 121b (121b is not shown) and the support shaft 103. In the present embodiment, the resonance peak of the leaf spring can be reduced, and in particular, the spring constant in the tracking direction, which tends to increase the spring constant of the leaf spring, can be easily set to a desired value.

[0031]

As described above, the objective lens driving device according to the present invention has the following effects.

Since the contact portion is eliminated by supporting the movable portion with the leaf spring, it has a stable control system that does not generate a frictional force when performing focusing control and tracking control, and it does not cause wear and wear and the surrounding area. There is an effect that an objective lens driving device can be obtained which does not cause optical adverse effects or shortening of the life of parts.

Further, since no rotation moment about the support shaft as a rotation center is generated with respect to the movable portion when seeking the optical disk, there is an effect that an objective lens driving device in which unnecessary residual vibration after the completion of seeking is suppressed can be obtained.

Further, since it is possible to suppress an unnecessary torsional resonance mode of the leaf spring particularly during drive control in the tracking direction, it is possible to obtain an objective lens drive device having a stable control system.

Further, since it is possible to reduce the variation in the spring constant of the leaf spring, there is an effect that an objective lens driving device having high mass productivity can be obtained.

Further, since the resonance peak of the leaf spring is reduced and it is easy to set the spring constant in the tracking direction where the spring constant of the leaf spring tends to be high, it is easy to set a stable control system. There is an effect that the objective-lens drive device which has is obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a main part of an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a plan view of a main part of the first embodiment.

FIG. 3 is a sectional view of a main part of the first embodiment.

FIG. 4 is a cross-sectional view of an essential part showing a driving state in a focusing direction of Example 1.

FIG. 5 is a cross-sectional view of a main part showing a driving state in a focusing direction of Example 1.

FIG. 6 is a plan view showing the shape of the leaf spring of the first embodiment.

FIG. 7 is a sectional view of a main part of an objective lens driving device according to a second embodiment of the present invention.

FIG. 8 is a perspective view of a leaf spring according to a third embodiment of the present invention.

FIG. 9 is a perspective view of a leaf spring according to a fourth embodiment of the present invention.

FIG. 10 is a plan view of a main part of an objective lens driving device according to a fifth embodiment of the present invention.

FIG. 11 is a perspective view of a main part of a conventional objective lens driving device.

12 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 103 Support Axis 110 Lens Holder 111 Objective Lens 115 Balance Weight 116a Leaf Spring 116b Leaf Spring

Claims (5)

[Claims] 1. An objective lens drive device mounted on an optical disk device for optically recording or reproducing information on an optical disk, for driving and controlling a condensed spot position condensed on the optical disk. An objective lens for converging a light beam on the top, a lens holder having the objective lens fixed at one end, a support shaft having an axis parallel to the optical axis of the objective lens, and a perpendicular to the support shaft A pair of flat surfaces that are substantially concentric with the axis fixed to the support shaft, the inner circumference being fixed to the support shaft, and the outer circumference being fixed to the lens holder. A leaf spring is provided, and focusing control is performed by driving the lens holder along the axis, and focus control is performed by rotating the lens holder about the axis. An objective lens driving device characterized by performing racking control. 2. A balance weight is provided on the lens holder so that the position of the center of gravity of a movable portion composed of a lens holder supported by a leaf spring is located on the support shaft. Item 1. The objective lens driving device according to item 1. 3. The objective lens driving device according to claim 1 or 2, wherein the leaf spring also has an element perpendicular to the plane. 4. The objective lens driving device according to claim 1, wherein the leaf springs are coupled to each other. 5. The objective lens driving device according to claim 1, wherein an elastic member is added to the inner peripheral portion of the leaf spring.