JPS61182641A - Device for supporting objective lens - Google Patents

Abstract

PURPOSE:To improve vibration characteristics in focusing and tracking directions and to access a subject at a high speed by small force by setting a pair of parallel elastic members, whose one end is fixed on an objective lens unit and whose other end is fixed to a movable member moving in the direction vertical against an optical axis, to the prescribed shape. CONSTITUTION:A current corresponding to a tracking error is flowed into a tracking drive coil 8, whereby an objective lens 5 moving integrally with a turning member 68 is rotatably driven in a tracking direction 1002. Moreover a current corresponding to a focusing error is flowed into a focus drive coil 64, whereby an objective lens 60 is driven in a focusing direction 1001. In this case the elastic members 66 having center lines 96 and 98 are disposed in a V-shape with an angle theta, whereby external force F acts by splitting it into F1 and F2, and the rigidity with respect to bending of the elastic member 66 in the direction 1002 is improved. The elastic member 66 having a center line 97 and that having center lines 96 and 98 comprise a pair of upper and lower parallel springs to improve the rigidity in the torsion direction and the vibration characteristic.

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. This is related to a device that performs defocus correction to correctly project a light spot, that is, correction of relative positional deviation between the focusing and information track and the light spot projected by the objective lens, that is, tracking. The present invention relates to an objective lens driving device that drives in a direction perpendicular to an information track.

2. Description of the Related 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 Laid-Open No. 58-53035, in order to correct focusing and tracking with good responsiveness.

FIG. 7 shows this principle. In the figure, 1
0o1 indicates the focusing direction, and 1o02 indicates the tracking direction.

Reference numeral 2 denotes an objective lens, which is supported movably in parallel to the optical axis only in a 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.

Reference numeral 8 denotes a focus drive magnet fixed to the objective lens 2, which causes the objective lens 2 to move by passing a current corresponding to the force socing error amount to the focus drive coil/l/10.
to drive. The plate spring fixing base 3 is fixed to the optical system 18,
Further, the optical system 18 rotates around the rotation axis 14 integrally with the tracking arm 12.

16 is a balancer, which includes an objective lens 2, an optical system 181, a tracking arm 12. Tracking drive carp/l/22
The dynamic balance of the parts including the 2
o is a tracking drive magnet, which generates magnetic flux in a direction parallel to the focusing direction 1001, and which drives the tracking drive coil 1 attached to the tracking arm 12.
The tracking arm 12 is driven by passing a current corresponding to the amount of tracking error through V22.

Problems to be Solved by the Invention However, in this device, the tracking direction is 10°.
2, the plate springs 4 and 6 are configured so that force is applied in the compression and tension directions, so the plate spring fixing base 3 must be placed at the tip of the tracking arm 12. 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 moves integrally with the objective lens, and that moves in a direction perpendicular to the optical axis of the objective lens. a movable member; 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. the pair of elastic members are located on two planes parallel to the optical axis of the objective lens, and have a shape that matches the shape of the objective lens. Parallel straight line parts having their starting points at the intersection of the first straight line parallel to the optical axis and the two planes, and a V-shaped straight line having the intersection as the apex and located line-symmetrically with the straight line part. The structure is such that the two parts are located on each center line.

Operation The present invention has the above-mentioned configuration, so that the fore-force shinging direction,
Figure υ shows the improvement of vibration characteristics in the tracking direction and tracking direction.
However, by reducing the moment of inertia of the rotating body, high-speed access can be achieved with a small force.

EXAMPLE Hereinafter, an objective lens support device according to an example of the present invention will be described 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. Fig. 1 is a perspective view of the entire embodiment, and Fig. 2 is a perspective view of the entire embodiment.
3(B) and 3(B) are a plan view and a front view showing details of the structure of the embodiment, respectively.

1001 indicates the focusing direction, and 1oo2 indicates the tracking direction.

Reference numeral 5o denotes an objective lens, which is fixed to an objective lens fixing base 62 so that its optical axis is parallel to the focusing direction 1001. Reference numeral 66 denotes a pair of upper and lower elastic members, which are arranged in two planes perpendicular to the 7 orcasing direction 1o○1, one end of which is connected to the objective lens fixing base 52, and the other end of which is connected to the rotating member 68.
Fixed. A tracking drive magnet 74 is fixed to a rotating yoke 69 that rotates around the rotating shaft 62 integrally with the rotating member 68, and generates magnetic flux in the focusing direction 10o1. The tracking drive coil 78 fixed to
Driven by o2. Note that the coil yoke 77 is fixed to the housing 76.

The rotation shaft 62 is supported by the housing 76 by two bearings 92 and 94 parallel to the optical axis 1oo of the objective lens 6o, and a hole 8o is provided in the center of the rotation shaft 62.

A laser beam 86 emitted from a fixed optical system 82 passes through a hole 80 and passes through a prism 84 fixed on a rotating member 68.
It is totally reflected at both end surfaces 8B and 90 and guided to the objective lens 5o.

64 is a focus drive magnet, yoke 56.5
In the gap 6o formed by 8, magnetic flux is generated in directions perpendicular to each of the tracking direction 1o02 and the focusing direction 10o1. The gap 6o is formed in an arc shape, and the center of the arc coincides with the rotation center of the rotation shaft 62.

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

As shown in FIG. 3, the elastic member 66 is movable in the focusing direction 1001 as a pair of upper and lower parallel springs. The elastic member 66 has three center lines 96, 97, 98
have. The center line 97 is a straight line connecting the center 99 of the objective lens and the center of rotation of the rotating member 68, and the center line 96.98
is symmetrical about the center line 97 and the point 7 on the center line 97
0, intersect at an angle θ to form a V-shape. Intersection point 70 of center lines 96, 97.98 of the pair of upper and lower elastic members 66
A straight line 71 connecting the objective lenses 50 and 71 is parallel to the optical axis 100 of the objective lens 5o. Objective lens fixing stand 52. The center of gravity 72 of the focus drive coil 64 passes through the center of gravity, and the two intersection points 7o are located at symmetrical positions with respect to the center of gravity 72.

In the device configured as above, the current corresponding to the tracking error is
The objective lens 60, which moves integrally with the rotary member 68, is rotatably driven in the tracking direction 1o02 by flowing a current into the focus drive coil 1L/64, and a current corresponding to the focusing error is caused to flow through the focus drive coil 1L/64. The objective lens 5o can be driven in the forcing direction 1o01.

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 10o1 and the tracking direction 1002.

In FIG. 6, only a bending moment in the tracking direction 1002 acts on the leaf spring 11° in response to the external force F. Generally, leaf springs have low rigidity against bending, but extremely high rigidity against compression or tension. Particularly in devices that require high rigidity in the tracking direction 1002, the arrangement of the leaf springs 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 11o, the resonant frequency in the racking direction 1002 increases;
Since the rigidity of the lens is high, a large driving force is required when driving in the focusing direction 1001.

As shown in FIG. 4, by arranging the elastic members 66 having a center line 96.98 in a V-shape at an angle θ,
The external force F acts as component forces Fl and F2. Therefore, not only a bending moment but also a component in the compression and tension direction acts on the elastic member 66, and the rigidity of the elastic member 66 against bending in the tracking direction 1002 becomes high. Next, FIG. 6 shows a cross-sectional view of BB' in FIG. 4(B). The elastic member 66 having the centerline 97 has the effect of increasing the rigidity when subjected to a force in the torsional direction 10Q3. Elastic member 6
If the mutual lengths and widths of the elastic members 66 differ slightly due to errors during processing or assembly, a deviation occurs between the mechanical action point of the elastic member 66 and the center of gravity 72. Therefore, when the external force F acts, the objective lens fixing base 52 is rotated in the rotation direction 100.
The power of 3 works.

In this case, each elastic member 66 for the direction of rotation 10o3
The stiffness of each of the elastic members 66 has the largest section modulus with main axes z, m, and n.Among the elastic members 66, the elastic portion 66 having the main axis m has the largest section modulus. Therefore, by the elastic member 66 having the center line 97, the direction of rotation 1 is
The rigidity for o03 is improved.

In the forcing direction 1001, the elastic member 66 is a general parallel spring and exhibits conventional characteristics.

As described above, according to this embodiment, the elastic member 66 is arranged on two planes perpendicular to the optical axis 1oo of the objective lens 6o, and furthermore, the elastic member 66 is located at the intersection 70 of the center line 96°97.98.
is placed on a straight line 71 passing through the center of gravity 72 and parallel to the optical axis 100, and by intersecting the center lines 96 and 98 symmetrically with respect to the center line 9 at an angle θ, the focusing direction 1001 and the tracking direction can be determined. 1002 and the rotational direction 1003 can be obtained favorably. Here, the best characteristics can be obtained when the angle θ=900.

In addition, by arranging as described above, the rotating member 6
Since the length in the radial direction of 8 can be shortened, the moment of inertia can be reduced.

Effects of the Invention The apparatus of the present invention includes an objective lens unit that moves integrally 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; a forcing driving means for driving the objective lens unit in the optical axis direction of the objective lens; and a tracking drive for driving the movable member. the pair of elastic members are located on two planes parallel to the optical axis of the objective lens, and the shape of the elastic members is a first straight line parallel to the optical axis of the objective lens and a first straight line parallel to the optical axis of the objective lens; and a V-shaped straight line portion having the intersection point as the apex and being located line-symmetrically with the straight line portion, each having a center line. Force direction of objective support device,
)' It is possible to improve the vibration characteristics regarding the F-cking direction and the rotation direction.

[Brief explanation of drawings]

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 seen from the entrance direction of FIG. 1, and FIGS. 3 and 4 are This figure shows an objective lens support device in one embodiment, where (m) is a plan view,
In addition, (B) is a front view, FIG. 5 is a BB' cross-sectional view of FIG. 4 (B), FIG. 6 is an explanatory diagram when receiving only a bending moment, and FIG. 7 is a conventional objective lens support device. It is a perspective view showing an example of the composition used. 2...Objective lens, 4, 6...Plate spring, 8...Four force ag dynamic McNet, 1o...
... Focus drive coil, 12 ... Tracking arm, 14 ... Rotation axis, 16 ...
... Balancer, 18 ... Optical system, 52 ...
...Objective lens fixing base, 66...-elastic member, 68... Rotating member, 69... Rotating yoke, T. ...Intersection, 72...Center of gravity, 74...
...Tracking drive magnet, 76...
・Housing, 77... Coil yoke, 78・
...Tracking drive coil, 8o...
・Hole, 82...Fixed optical system, 84...
Prism, 92.94...Bearing, 96,97°98...Center line, 100...Optical axis. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure σo---Text↑waLns゛62-1! h# 84--Bliss Figure 3
91-Voice sound munsu゛<Bt Figure 4 (B) Mei 6 Figure

Claims (3)

[Claims] (1) An objective lens unit that moves integrally 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 fixed to the movable member. a pair of mutually parallel elastic members, a focusing drive means 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 elastic members are located on two planes parallel to the optical axis of the objective lens, and each of the elastic members has a shape starting at the intersection of the two planes and a first straight line parallel to the optical axis of the objective lens. An objective lens support device characterized in that each center line has a parallel straight line part and a V-shaped straight part whose apex is the intersection point and is located line-symmetrically with the straight line part. (2) The objective lens support device according to claim 1, wherein the first straight line parallel to the optical axis is configured to pass through the center of gravity of the objective lens unit. (3) The angle formed by the two sides of the V-shape located symmetrically is 9
The objective lens support device according to claim 1, characterized in that the angle is 0°.