JPS60263348A - Objective lens driver - Google Patents

Abstract

PURPOSE:To avoid a shift of the optical axis of an objective lens despite the displacement of a mobile member by dividing vertically an objective lens supporter comprising a mobile member, an intermediate connection member and a pair of hinge parts into two parts centering on an optical axis. CONSTITUTION:The 1st objective lens supporter 20 contains a mobile member 21 fixing an objective lens 2 and a drive coil 30, an intermediate connection member 22, a support member 23 and a hinge member 24. The member 22 is connected to a hinge part 42 of the 2nd objective lens supporter 40. The member 21 is displaced in the direction X by the force F2 just by the flexion of the part 42 together with the drive of the coil 30, a magnet 60 and a yoke 70. Thus the rotary movement can be prevented round the axis Z. This eliminates a shift of the optical axis of the lens 2. In addition, the number of component parts is decreased since the component member of the supporter 20 is vertically divided into two parts. This simplifies the assembling and adjustment and improves the stable quality for an objective lens driver.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an objective lens driving device, and more specifically, the present invention relates to an objective lens driving device, and more particularly, to The present invention relates to an objective lens driving device that drives an objective lens in the optical axis direction of the objective lens and in a direction perpendicular to the optical axis in order to accurately correct and control the position of a light spot.

(Background of the Invention) In the original school type reproduction pupil system that uses laser light, the laser light is focused on a minute spot by a lens, etc., and the signal recorded on the "1d information track of the disc-shaped disk that is the recording medium is detected. However, in order to detect signals correctly, it is necessary to control the focus to accurately focus the light spot on the recording medium and to always use the correct signal to detect the light spot, depending on the unevenness of the recording medium and vibrations caused by rotation. Tracking control is required to follow the track.

This type of optical information playback device has been put into practical use as a video disc and a digital audio disk, and its application is also expanding to high-density information recording and playback devices such as converters.

This is a method in which encoded video signals, audio signals, or other signals are recorded as information on the trunk of a disk, which is a recording medium, and the disk is not rotated at high speed so that it cannot be exposed to a light source such as a laser beam. A device that reproduces recorded information by focusing light on a trunk on a disk and detecting reflected light from the disk surface,
Recently, it has been rapidly used as a device that can reproduce high-quality information with little noise.

(Prior art and problems with the invention) Figures 4 and 5 are main part ff1+ perspective views showing an objective lens driving device for an optical pickup used in a conventional optical reproducing device. To explain using the objective lens driving device A shown in FIG. A drawing plate spring 3.4 is connected by an intermediate connecting member hole so as to be deflected in the X-X/ direction by a pair of parallel-opposed and parallel-opposed plate springs 4 of the same length, and the plate spring 4 is deflected in the x-x' force direction. The end portion of is fixed to the fixing member 6. In addition,
Although not shown, this objective lens driving device is
A drive mechanism that generates a force F in the Y' force direction and a force F in the X-X' force direction, for example, an electromagnetic drive mechanism using a coil and a magnetic circuit is provided.

Next, the operation of this objective lens drive device A will be explained. First, when a Y-Y' force direction force F1 is applied to the movable member 1 by a drive mechanism (not shown), the plate spring 4
1), Y-Y'force direction) K has a strong rigidity, so the intermediate connecting member 5 does not displace in the Y-Y' direction,
Only the leaf spring 3 has a force F1 and a torque T generated by the force F1.
1 causes a deflection in the Y-Y' force direction, and this deflection displaces the movable member 1 in an arc around the Y-axis in the Y-Y' force direction. At this time, compared to the distance (i, )
Since the objective lens is at a close distance (ls) (l<i,) with respect to K, the deflection due to the torque T1 of the leaf spring 3 is extremely small compared to the deflection due to the force F, which originates from the rotation around the Y axis. 20 The tilt of the optical axis can be ignored.

Furthermore, when F in the X-X/direction is similarly applied to the movable member 1, the leaf springs 3 & 1 have strong rigidity in the X-X' force direction, so the force F is applied to the intermediate connecting member 5 via the leaf spring 3. , and force F
, the torque T caused by , is added, and this torque Tt
Since the leaf spring 4 is deflected in the x-x' force direction, the movable member 1 is displaced in the x-x' force direction while drawing an arc around the Y axis. However, in this structure, since the driving point of the movable member 1 is located at a remote distance from the leaf spring 4 via the leaf spring 3, the combined mass of the movable member 1 and the intermediate connecting member 5 Deflection stiffness in the X-X/direction of 4 and K
The first resonance due to the rotational torque T! Because two resonances occur: a second resonance due to the resultant moment of inertia of the movable member (A) and the intermediate connecting member 5 around the Y-axis caused by the rotational stiffness of the leaf spring 4 around the Y-axis, The drawback was that the servo was difficult to apply.

In addition, to explain the objective lens driving device B in FIG. The other ends are fixed to the fixing member 8, either in close contact with each other or with a sufficiently small interval.The bending direction of the two leaf springs constituting the supporting member 7 is in the X-X/direction. The leaf spring 3 and the support member 7 are as follows.
They are connected so as to be orthogonal to each other via an intermediate connecting member 5, and the optical axes of the objective lenses 2 are aligned in the Y-Y' force direction.

In the drive device configured as described above, two resonances occur due to linear motion and rotational motion when the movable member 1 of drive device A is driven in the x-x' force direction, whereas in drive device B, two resonances occur due to linear motion and rotational motion.
In this case, it becomes possible to limit the resonance only to resonance caused by rotational motion. For this reason, drive device B has a structure that is effective in eliminating the dual resonance related to the X93 plane, which has been difficult to solve with the structure of drive device #.

However, these methods do not focus on the influence of the rotational torque T generated around the Z-axis;
It has the disadvantage that it is almost invulnerable to the tilt of the optical axis of the objective lens 2 caused by the rotation of the movable member 1 around the Z-axis caused by FC.

In addition, in the drive device B, the movable member (A')
Also, when displacing in the Y-Y/force direction or the X-X/ direction by one force F, the movable member (A'), objective lens (B'), and FIG. Although not shown, there may be a difference due to various causes between the combined center of mass (hereinafter referred to as the "center of gravity") in the XY plane of the drive system member consisting of the drive coil wound and fixed around the movable member (A') and the drive center. When a positional shift occurs, Z passing through the drive center of the drive system member
Rotational torque T3 due to the moment of inertia) K is generated around the axis, which causes resonance with the torsional stiffness of the leaf spring (C') in the XY plane, and as a result, the movable member (
The objective lens (B') derived from the rotation of A') around the Z axis
) causes the optical axis to tilt.

In the structure of the drive device B, as a method of preventing the optical axis of the objective lens (B') from tilting due to the rotation of the movable member (A') around the Z axis, the first K rotational torque T,
There are various ways to make adjustments to eliminate the misalignment between the center of gravity of the drive system components and the drive center, which is the biggest cause of It is difficult to completely eliminate dimensional errors in the mounting of parts and the mounting of parts.On the other hand, when a weight balancer (not shown) is used to adjust the center of gravity, mounting the Mt balancer itself requires time and effort to adjust the position. However, there are many disadvantages such as the weight of the entire drive system member being increased more than necessary. Second, a leaf spring (C') that connects and supports the movable member (A')
) can be considered to increase the rigidity in the torsional direction to make it less susceptible to deformation due to the rotational torque T, but each method has its advantages and disadvantages. That is, as a method to increase the rigidity of the leaf spring (C') in the torsional direction, for example, (1) use a material with a high spring constant, or (11) increase the thickness of the leaf spring (C/). (+++) Make the leaf spring (C') wider (1■) Leaf spring (C')
Possible options include making the length of the spring (V) in the Z-axis direction shorter, or increasing the distance between the two parallel and opposing leaf springs (C').

However, in the methods (1) and (11), the leaf spring (C'
) also increases at the same time, the Y-Y/force direction driving force F of the drive member (A') increases, and (m) is the width of the objective lens drive device. (X-X/direction) becomes large, which makes it difficult to miniaturize the device, and as a result of being subject to dimensional constraints, there is a limit to its effectiveness. Also, (1v) is a leaf spring (C'
) If the length of the leaf spring ( C')
Since the deflection due to the torque T of
') can no longer be ignored, and as a result of being subject to dimensional constraints, there is a limit to its effectiveness. Furthermore, (V) is
Since the thickness of the objective lens driving device (Y-Y' force direction increases), there is a problem in making the device thinner and subject to dimensional restrictions.

Of course, this also applies to the drive device A'.

(Object of the Invention) The object of the present invention is that when the movable member that holds and fixes the objective lenses in the x-x' and Y-Y' force directions is displaced, the rotational movement of the movable member around the Z axis occurs. An object of the present invention is to provide an objective lens driving device that prevents the optical axis of an objective lens from tilting.

(One Embodiment of the Invention) An embodiment of the present invention will be described in detail using the drawings of FIGS. 1 to 3. FIG. 3 is a perspective view showing the principle structure of the objective lens driving device C. Figure 1 is.

A perspective view showing one embodiment of the present invention, FIG. 2 is an exploded perspective view of FIG. 1.

In the figure, reference numeral 21 denotes a movable member, and the movable member 21 is formed with a fixing part 25 for fixing the objective lens 2 and a fixing part 26 for fixing the drive coil 30. 23
are a pair of parallel and opposing rigid support members,
The support member 23 is arranged in the optical axis direction (Y-Y/
Equipped with hinge members 24 at both ends that are movable only in the force direction,
One end is connected to the movable part 21 via the hinge part 24, and the other end is connected in a direction perpendicular to the optical axis of the objective lens 2 (X-X
/direction) is provided with a hinge member 42 that is movable only in
The intermediate connecting member 22 is connected and fixed to the intermediate connecting member 22 which is engaged by a connecting portion 41 formed on the objective lens driving support 40 . The first objective lens drive support 20 is composed of the above-mentioned movable member 21, intermediate connection member 22, support member 23, and hinge member 24, and is fixed via the second objective lens drive support 40. It is supported by a support body 5.

Further, the first objective lens driving support 20 can be divided into two parts that can be fitted together and integrated together on a plane substantially perpendicular to the optical axis of the objective lens 2 (X-Z plane).

When assembling this first objective lens drive support 20 and fitting and integrating it, one drive support 20a and the other drive support of the first objective lens drive support 20 which is divided into two are prepared in advance. A drive coil 30 and the like are arranged between the body 20b and the pair of drive supports 20a and 20b are then fitted together. At this time.

The drive coil 30 is a movable member 21a divided into two parts.

21bK are fixed to fixing portions 26a and 26b for fixing the drive coil 30 formed therein.

Note that at this time, the second objective lens drive support 40
The coupling portion 41 is formed in the recess 27 in the intermediate connecting member 22.
is engaged with. 43 is a fixed part, 50 is a rigid fixed support, 60 is a permanent magnet made of ferrite or the like, and 70 is a yoke that holds the permanent magnet 60.

The operation of the objective lens drive device configured as described above will be explained.

Now, the movable member 21 is connected to the drive coil 3 as shown in FIG.
0. When displaced in the Y-X/direction or the X-X/direction by the force F1 or the force F generated by the electromagnetic drive mechanism consisting of the magnet 60 and the yoke 70, the drive including the objective lens 2 and the drive coil 30 to be aligned is controlled. When the first and second drive supports are moved, a positional shift occurs between the center of the combined mass (center of gravity) in the X and Y planes of 40 and the drive center (inside the magnetic drive mechanism 11L). This positional displacement generates a rotational torque T due to a moment of inertia around the Z axis passing through the drive center of the drive support 20°40. However, the hinge portion 24.4 of each drive support 20, 400
Since the other members except 2 are formed of rigid bodies, they are not affected by deformation due to the rotational torque T3. Therefore, the rotational torque T is a torsional stress around the Z axis on the hinge @24.42. acts in a concentrated manner. however,
Each hinge portion 24.42 has a Z
Axial length ljl, l! X of hinge part 24 against *
Effective length in 1111 direction.

Since the relative ratio (L+#t, L*/Vt) of the effective length of the hinge portion 42 in the Y-axis direction is extremely large, the deformation due to the torsional stress is negligibly small, and the It almost acts as a rigid body. Therefore, Z of the movable member 21 due to the rotational torque T3
Almost no rotational movement due to the moment of inertia around the axis occurs, and the inclination of the optical axis of the objective lens 20 can be suppressed to a negligible level.

The material of the hinge portion 24.42 may be, for example, a highly elastic synthetic resin material such as polyacetal or polypropylene resin, phosphor bronze, spring steel alloy such as aluminum copper, copper titanium, or nickel silver, or spring material. Highly elastic metal materials such as stainless steel can be considered. 1%, when the high elastic metal material is used for the hinge portion 24.42, it can be used in combination with various moldable synthetic resins by insert molding etc. The projecting part) can be used as a hinge part, and one synthetic resin part can be used as a rigid body. Further, at this time, if the material of the synthetic resin is selected in accordance with the purpose and in the appropriate summer, it is possible, for example, to efficiently absorb the resonance occurring in the elastic material with the synthetic resin.

(Effects of the Invention) As described above, in the objective lens driving device of the present invention, the displacement in the x-x' force direction due to the forces F' and VC of the movable member 210 is caused by the deflection of the hinge portion 42 of the second objective lens driving support 40. Since it is performed only by rotational movement, the x-x of the conventional movable member
It is possible to prevent secondary resonance caused by linear motion and rotational motion in the force direction, and it is also possible to prevent secondary resonance in the Y-Y force direction and x
It is possible to prevent rotational movement around the 5z axis due to displacement in the -x' force direction, and the optical axis of the objective lens held and fixed to the movable member can be almost completely shifted.

Further, in this objective lens driving device, the four constituent members of the moving member 21, the intermediate connecting member 22, the supporting member 23, and the hinge portion 24 are divided into two parts, and since these are integrally formed, Not only is the number of parts reduced, but also the complicated position adjustment during assembly work between these constituent members can be simplified.

Therefore, this objective lens drive device! Not only is it stable and high quality, but it is also extremely effective in terms of productivity.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an objective lens driving device showing one embodiment of the present invention, FIG. 2 is an exploded perspective view of FIG. 1, and FIG.
FIG. 1 is a perspective view showing the main part configuration, and FIGS. 4 and 5 are perspective views showing the main part structure of a conventional objective lens driving device. 2... Objective lens, 20... First objective lens drive support, 21... Movable member, 22
...Intermediate connection member, 23...Supporting member, 24.42...Hinge part Fig. 3Y Fig. 4

Claims (1)

[Claims] a movable member for fixing the drive coil; an intermediate connecting member coupled to a support member having a hinge portion that is movable only in a direction perpendicular to the optical axis of the objective lens; A pair of movable hinge parts,
A lens drive device comprising an objective lens and an objective lens drive support body comprising a pair of rigid support members, one end of which is connected to the movable member and the other end of which is connected to the intermediate connection member via the hinge portion. In the objective lens driving device, the objective lens driving support body is divided into two parts on a plane substantially perpendicular to the optical axis of the objective lens.