JPH0576705B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for reading information by projecting a reading light spot onto an information track recorded spirally or concentrically on a recording medium. It relates to a device that performs focusing and information tracking to correctly project a light spot, and corrects a relative positional shift between the light spot projected by the objective lens, that is, tracking. and an objective lens drive device for driving in a direction perpendicular to the information track.

BACKGROUND ART In recent years, many video and audio recording and reproducing devices using optical disks have been announced, and related technologies have also progressed accordingly. In particular, various methods have been proposed for optical pickup, but at present they are somewhat inferior in terms of high-speed access compared to magnetic disks, and technological development in this field is desired.

In an optical reading device, a mechanism for two-dimensionally driving an objective lens is disclosed in Japanese Patent Application Laid-open No. 53035/1983, in order to correct focusing and tracking with good responsiveness.

FIG. 7 shows this principle. In the figure, 1001 is the focusing direction, and 1001 is the focusing direction.
02 indicates the tracking direction.

Reference numeral 2 denotes an objective lens, which is supported movably in parallel to the optical axis only in the focusing direction 1001 by a pair of parallel leaf springs 4 and 6 whose one end is fixed to a leaf spring fixing base 3.

A focus drive magnet 8 is fixed to the objective lens 2, and drives the objective lens 2 by passing a current in a focus drive coil 10 in accordance with the amount of focusing error. The plate spring fixing base 3 is fixed to an optical system 18, and the optical system 18 rotates about a rotation axis 14 integrally with the tracking arm 12.

16 is a balancer, objective lens 2 and optical system 1
8. The parts including the tracking arm 12 and the tracking drive coil 22 are dynamically balanced. A tracking drive magnet 20 generates a magnetic flux in a direction parallel to the focusing direction 1001, and performs tracking by passing a current corresponding to the amount of tracking error through a tracking drive coil 22 attached to the tracking arm 12. The arm 12 is driven.

Problems to be Solved by the Invention However, in this device, when driven in the tracking direction 1002, force is applied to the leaf springs 4 and 6 in the compression and tension directions. Tracking arm 1
It must be placed at the tip of 2. Therefore, the distance from the center of rotation of the rotation shaft 14 becomes longer, and the moment of inertia becomes larger. Therefore, there was a problem in that a large force had to be generated when driving at high speed in the tracking direction 1002.

Means for Solving the Problems In order to solve the above problems, the objective lens support device of the present invention includes an objective lens unit that is movable to move in a direction perpendicular to the optical axis of the objective lens. a pair of mutually parallel elastic members having one end fixed to the objective lens unit and the other end fixed to the movable member, and a focuser for driving the objective lens unit in the optical axis direction of the objective lens. and a tracking drive means for driving the movable member, the pair of elastic members are respectively located on two planes parallel to the optical axis of the objective lens, and have a shape that matches the light of the objective lens. Parallel straight line portions having their starting points at the intersection of a first straight line parallel to the axis and the two planes, and a V-shaped straight line portion having the intersection as the apex and located line-symmetrically with the straight line portion. It is constructed so that each center line has a .

Effect: With the above-described structure, the present invention improves the vibration characteristics in the focusing direction and the tracking direction while reducing the moment of inertia of the rotating body, thereby allowing high-speed access with a small force. be able to.

Embodiment An objective lens support device according to an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show the structure of an apparatus using an embodiment of the objective lens support apparatus according to the present invention. Figure 1 is a perspective view of the entire embodiment, Figure 2 is a perspective view of the entire embodiment.
The figure is a sectional view taken from the direction of arrow A in FIG. 1, and FIGS. 3A and 3B are a plan view and a front view, respectively, showing details of the structure of the embodiment.

1001 indicates the focusing direction; 1001 indicates the focusing direction;
02 indicates the tracking direction.

Reference numeral 50 denotes an objective lens, which is fixed to an objective lens fixing base 52 so that its optical axis is parallel to the focusing direction 1001. A pair of upper and lower elastic members 66 are arranged in two planes perpendicular to the focusing direction 1001, and one end is fixed to the objective lens fixing base 52 and the other end is fixed to the rotating member 68. 74 integrally with the rotating member 68, the rotating shaft 6
A tracking drive magnet fixed to a rotating yoke 69 that rotates around 2 generates magnetic flux in the focusing direction 1001.
It is driven in a tracking direction 1002 about a rotation shaft 62 (FIG. 2) by a tracking drive coil 78 fixed to a coil yoke 77. Note that the coil yoke 77 is fixed to the housing 76.

The rotation axis 62 is moved parallel to the optical axis 100 of the objective lens 50 by two bearings 92 and 94 in the housing 7.
6, and a hole 8 is provided at the center of the rotation shaft 62.
0 is set. A laser beam 86 emitted from a fixed optical system 82 passes through a hole 80 and reaches both end surfaces 8 of a prism 84 fixed on a rotating member 68.
It is totally reflected at 8 and 90 and guided to the objective lens 50.

A focus drive magnet 54 generates magnetic flux in a direction perpendicular to the tracking direction 1002 and the focusing direction 1001 in a gap 60 formed by the yokes 56 and 58. The gap 60 is formed in an arc shape,
The center of the arc coincides with the rotation center of the rotation shaft 62.

64 is a focus drive coil with a gap of 60
, and is fixed to the end surface of the objective lens fixing base 52 opposite to the part where the objective lens 50 is attached, with an appropriate gap between the yokes 56 and 58.

As shown in FIG. 3, the elastic member 66 is configured as a pair of upper and lower parallel springs in the focusing direction 100.
It is movable at 1. The elastic member 66 has three center lines 96, 97, and 98. center line 97
is a straight line connecting the center 99 of the objective lens and the rotation center of the rotation member 68, and the center lines 96 and 98 are the center line 97.
and intersect at a point 70 on the center line 97 at an angle θ to form a V-shape. A first straight line 71 connecting the intersection 70 of the center lines 96, 97, and 98 of the pair of upper and lower elastic members 66 is parallel to the optical axis 100 of the objective lens 50, and is parallel to the optical axis 100 of the objective lens 50, and is connected to the objective lens 50, the objective lens fixing base 52, and the focus drive coil. 64, and the two intersections 70 are located at symmetrical positions with respect to the center of gravity 72.

In the apparatus configured as described above, the objective lens 50, which moves integrally with the rotating member 68, is rotated in the tracking direction 1002 by passing a current corresponding to the tracking error to the tracking drive coil 78. The objective lens 50 can be driven in the focusing direction 1001 by driving the focus driving coil 64 to flow a current corresponding to the focusing error.

In this case, the rigidity of the elastic member 66 is a point to be noted in order to stably control tracking and focusing.

FIG. 4 shows an example of the objective lens support device of the present invention, and FIG. 6 shows a conventional support device. Here, let us consider the rigidity in the focusing direction 1001 and the tracking direction 1002.

In FIG. 6, the leaf spring 11 is
0, only the bending moment in the tracking direction 1002 acts. Generally, leaf springs have low rigidity against bending, but extremely high rigidity against compression or tension. Especially tracking direction 10
02, the arrangement of the leaf spring 110 as shown in FIG. 6 is disadvantageous because the resonance frequency of the bending mode appears low.
Furthermore, by widening the width W of the leaf spring 110, the resonance frequency in the tracking direction 1002 becomes higher, but on the other hand, the rigidity in the focusing direction 1001, which requires low rigidity, becomes higher. When trying to drive it, a large driving force is required.

As shown in FIG. 4, by arranging the elastic member 66 having center lines 96 and 98 in a V-shape at an angle θ, the external force F acts as component forces F ₁ and F ₂ . Therefore, not only a bending moment but also a component in the compressive and tensile direction acts on the elastic member 66.
The rigidity of the elastic member 66 against bending in the tracking direction 1002 is increased. Next, Figure 5 is Figure 4B
BB′ cross-sectional view is shown in FIG. The elastic member 66 having the centerline 97 has the effect of increasing the rigidity when subjected to a force in the torsional direction 1003. If the mutual lengths and widths of the elastic members 66 differ slightly due to errors during processing or assembly, the elastic members 6
A shift occurs between the mechanical point of action 6 and the center of gravity 72. Therefore, when the external force F acts, a force in the rotational direction 1003 acts on the objective lens fixing base 52. In this case, the stiffness of each elastic member 66 in the rotation direction 1003 is based on the section modulus with main axes l, m, and n. Among the elastic members 66, the one with the largest section modulus is the main axis m The elastic portion 66 has the following characteristics. Therefore, the elastic member 66 having the centerline 97 improves the rigidity in the rotational direction 1003.

Furthermore, in the focusing direction 1001, since the elastic member 66 is a general parallel spring, it exhibits the same characteristics as before.

As described above, according to this embodiment, the elastic member 66 is arranged on two planes perpendicular to the optical axis 100 of the objective lens 50, and the center line 96 of the elastic member 66,
The optical axis 10 passes through the center of gravity 72 through the intersection 70 of 97 and 98.
0 on the first straight line 71 parallel to the center line 9
6 and 98 are symmetrically intersected with respect to the center line 97 at an angle θ, good vibration characteristics in the focusing direction 1001, the tracking direction 1002, and the rotation direction 1003 can be obtained. Here, the best characteristics can be obtained when the angle θ=90°.

Moreover, by arranging as described above, the length of the rotating member 68 in the radial direction can be shortened, so that the moment of inertia can be reduced.

Effects of the Invention The apparatus of the present invention includes an objective lens unit that moves in conjunction with the objective lens, a movable member that moves in a direction perpendicular to the optical axis of the objective lens, one end of which is fixed to the objective lens unit, and the other end of which is fixed to the objective lens unit. a pair of mutually parallel elastic members whose ends are fixed to the movable member; focusing drive means for driving the objective lens unit in the optical axis direction of the objective lens; and tracking drive means for driving the movable member. , the pair of elastic members are each located on two planes parallel to the optical axis of the objective lens, and the shape thereof is formed between a first straight line parallel to the optical axis of the objective lens and the two planes. By configuring each center line to have parallel straight line parts starting from the intersection of the lines, and a V-shaped straight line having the intersection as the apex and positioned line-symmetrically with the straight line parts. The vibration characteristics of the objective lens support device in the focusing direction, tracking direction, and rotation direction can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an apparatus using an embodiment of the objective lens support device of the present invention, FIG. 2 is a sectional view taken from direction A in FIG. 1, and FIGS. 3 and 4 are The objective lens support device in one embodiment is shown in which A is a plan view, B is a front view, and the fifth
The drawings are a sectional view along BB' of FIG. 4B, FIG. 6 is an explanatory view when only bending moment is applied, and FIG. 7 is a perspective view showing an example of a configuration using a conventional objective lens support device. 2... Objective lens, 4, 6... Leaf spring, 8...
Focus drive magnet, 10... Focus drive coil, 12... Tracking arm, 14
... Rotation axis, 16 ... Balancer, 18 ... Optical system, 52 ... Objective lens fixing base, 66 ... Elastic member, 68 ... Rotation member, 69 ... Rotation yoke, 7
0...Intersection, 72...Center of gravity, 74...Tracking drive magnet, 76...Housing, 77
... Coil yoke, 78 ... Tracking drive coil, 80 ... Hole, 82 ... Fixed optical system, 84
...Prism, 92,94...Bearing, 96,9
7, 98...center line, 100...optical axis.

Claims (1)

[Scope of Claims] 1. An objective lens unit that moves integrally with the objective lens, a rotating member that moves the objective lens in a direction perpendicular to the optical axis of the objective lens, and a rotating member that has one end fixed to the objective lens unit. , an elastic member having the other end fixed to the rotating member, focusing drive means for driving the objective lens unit in the optical axis direction of the objective lens, and tracking drive means for driving the rotating member. The elastic members are located on two planes perpendicular to the optical axis 100 of the objective lens, and the shape thereof is a first straight line 71 parallel to the optical axis 100 of the objective lens and the two planes. straight line portions 97 starting from the intersection 70 of and substantially perpendicular to and parallel to the tracking direction;
and a V-shaped straight line 9 having the intersection 70 as its apex and arranged symmetrically with respect to the straight line portion 97.
6 and 98 on each center line. 2. The objective lens support device according to claim 1, wherein the first straight line 71 parallel to the optical axis is configured to pass through the center of gravity of the objective lens unit. 3 V arranged line symmetrically with respect to the straight line portion 97
2. The objective lens support device according to claim 1, wherein the angle formed by the straight lines 96 and 98 is 90 degrees.