JPH0830992A - Biaxial actuator - Google Patents

Abstract

PURPOSE:To reduce the overall thickness of the biaxial actuator and to reduce the cost by parallel holding a lens holder with one pair of leaf springs. CONSTITUTION:In the biaxial actuator 10, the lens holder 11 for supporting an objective lens 11 is supported via the leaf springs 14 by a fixed part 13. Each leaf spring 14 is formed to be folded back halfway in the reverse direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial actuator for an optical pickup used for recording and reproducing signals of an information recording medium for CD, MD, etc. and data storage.

[0002]

2. Description of the Related Art Conventionally, such a biaxial actuator for an optical pickup has been used for recording and reproducing a signal of an information recording medium such as an optical disc. Then, this actuator can move the objective lens provided on the support member in two directions of the focusing direction and the tracking direction.

Such a biaxial actuator is constructed, for example, as shown in FIG. In FIG. 5, the biaxial actuator 1 has a lens holder 2 to which an objective lens 2a is attached at the tip, and a coil bobbin 3 attached to the lens holder 2 by adhesion or the like.

The lens holder 2 has two ends perpendicular to the fixed portion 4 by two pairs of leaf springs 5 having one end fixed to both sides of the lens holder 2 and the other end fixed to the fixed portion 4. That is, it is movably supported in the tracking direction indicated by the reference symbol Trk and the focusing direction indicated by the reference symbol Fcs.

Further, the coil bobbin 3 is wound with a focusing coil and a tracking coil (not shown). By energizing each coil, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 attached to the fixed portion 4 and the magnet (not shown) attached to the yoke 6. .

According to the biaxial actuator 1 configured as described above, when a driving voltage is supplied to each coil from the outside, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 and the magnet. Then, the coil bobbin 3 is moved in the directions Trk and Fcs in the drawing. Thus, the objective lens 2a attached to the lens holder 2 is appropriately moved in the focusing direction and the tracking direction.

In this case, the leaf spring 5 is the lens holder 2
As shown in FIG. 6, parallel links are formed on both sides of each. As a result, the leaf spring 5 can be rocked against the tension of the leaf spring 5 as indicated by an arrow A by fixing the right end portion of FIG. 6 to the fixing portion 4. Therefore, the lens holder 2 supported on the left end of the leaf spring 5 is always moved in parallel without rotating, so that the optical axis of the objective lens 2a is not inclined.

[0008]

However, in the biaxial actuator 1 having such a structure, the two pairs of leaf springs 5 are arranged so as to be displaced by a height H as shown in FIG. Therefore, there is a problem that the biaxial actuator 1 becomes thicker by the height H.

Further, it is necessary to attach two pairs of leaf springs 5 to the lens holder 2 in parallel to each other, and there is a problem that the cost of processing and assembling precision of the leaf springs 5 becomes high. .

In view of the above points, the present invention allows the lens holder to be held in parallel by a pair of leaf springs,
It is an object of the present invention to provide a biaxial actuator which is thin and configured at low cost.

[0011]

According to the present invention, there is provided a lens holder for holding an objective lens, a coil bobbin attached to the lens holder, a focusing coil wound around the coil bobbin, and a tracking coil. A coil, the lens holder is supported by a fixed portion via a leaf spring, and the leaf spring has a portion that deforms in one direction and a portion that deforms in the opposite direction. This is achieved by a biaxial actuator for an optical pickup, which is composed of a pair of leaf springs having

In the biaxial actuator of the present invention,
Preferably, the leaf spring is composed of a portion extending from the fixing portion, a turn-back portion continuing from the fixed portion, and a portion connected to the lens holder from the turn-back portion.

In the biaxial actuator of the present invention, preferably, the leaf spring is connected to the lens holder so as to extend laterally.

Further, in the biaxial actuator of the present invention,
Preferably, the leaf spring, with respect to the lens holder,
It is connected so as to extend in the longitudinal direction.

[0015]

According to the above construction, since the leaf spring supporting the lens holder is formed so as to be folded back in the opposite direction on the way, the lens holder is moved by energizing the focusing coil provided in the lens holder. When the leaf spring is moved along the optical axis direction, the leaf spring is bent in the direction opposite to the portion from the fixed portion to the lens holder from the folded portion. Therefore, the lens holder will essentially always translate.

Since the lens holder is supported by the pair of leaf springs only with respect to the fixed portion, the lens holder and the biaxial actuator as a whole are made thin.

With respect to the lens holder, the leaf spring is
When connected in the lateral direction, the leaf spring will be connected to the lens holder in the same manner as in the past.

The leaf spring is attached to the lens holder,
When connected so as to extend in the longitudinal direction, the overhanging dimension of the leaf spring becomes relatively small on both sides of the lens holder.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to FIGS. In addition, since the Examples described below are preferred specific examples of the present invention, various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

FIG. 1 shows a first embodiment of a biaxial actuator according to the present invention. In FIG. 1, the biaxial actuator 10 includes a lens holder 11 that holds an objective lens 11a, and a coil bobbin 12 that is attached to the lens holder 11 by adhesion or the like.

The lens holder 11 has one end on both sides of the lens holder 11 and the other end fixed by a pair of leaf springs 14 fixed to the fixing portion 13.
Is supported so as to be movable in two directions perpendicular to the above, that is, the tracking direction indicated by the reference symbol Trk and the focusing direction indicated by the reference symbol Fcs.

Further, the coil bobbin 12 is wound with a focusing coil and a tracking coil (not shown). By energizing each coil, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 15 attached to the fixed portion 13 and the magnet attached thereto.

Further, the leaf springs 14 are formed so as to be folded back in the opposite directions on the way. That is, FIG.
As shown in FIG. 7, the leaf spring 14 is a point that is a connection point to the lens holder 11 and a point that is an intermediate point b toward one side.
It is composed of a first portion 14a extending to the point and a second portion 14b extending from the point b toward the opposite side to a point c which is a connecting point to the fixing portion 13. In this case, the first portion 14a of the leaf spring 14 is connected to the lens holder 11 at a portion that extends in the lateral direction.

Biaxial actuator 10 according to the present embodiment
Is configured as described above, and in the case of focusing, by energizing the focusing coil wound around the coil bobbin 12, the magnetic flux generated in the focusing coil and the magnetic flux flowing through the magnet and the yoke 15 are supplied. By the interaction with the lens holder 11
On the other hand, the force in the focusing direction Fcs acts.
As a result, the leaf spring 14 is elastically deformed as shown in FIG.
Is moved in the focusing direction Fcs, and the objective lens 1
Focusing of 1a is performed.

Here, the conditions under which the optical axis of the objective lens 11a of the lens holder 11 is not substantially inclined due to the elastic deformation of the leaf spring 14 as described above, that is, the condition that the moment at point a does not occur are as follows. Are described in. That is, in FIG. 3, the lengths L1 and L2 and the width W of the first portion 14a and the second portion 14b of the leaf spring 14 are equal to each other.
1, W2, the moment at the distance X from the point b is M, and the moment of inertia is I1 = I2.
In 14b, y "1 and y" 2 are

[0026]

[Equation 1]

[Equation 2]

[0027] Also, the slope y′1, at the point b
y'2 is

[0028]

(Equation 3)

[Equation 4]

It becomes In order for point a to be horizontal, y '
It may be 1 = y'2. Therefore,

(Equation 5) Becomes

Here, for example, when L1 = L2, I
1 = I2, and the leaf spring width W1 = W2. In this case, the slope y ′ at the point b is

(Equation 6) Becomes

In the above embodiment, the case where the moment is not generated in the movable portion of the biaxial actuator 10 has been described, but the present invention is not limited to this. In the case of shifting in the jitter direction), each part 14a, 14 of the leaf spring 14 is moved so that the point a moves in parallel, including the generated moment.
This can be dealt with by selecting the width and length of b.

FIG. 4 shows a second embodiment of the biaxial actuator according to the present invention. In FIG. 4, the biaxial actuator 20 includes a lens holder 11 that holds the objective lens 11a, and a coil bobbin 12 that is attached to the lens holder 11 by adhesion or the like.

The lens holder 11 has one end on both sides of the lens holder 11 and the other end fixed to the fixing portion 13 by a pair of leaf springs 21.
It is supported so as to be movable in two directions perpendicular to, namely, the tracking direction and the focusing direction.

Further, the coil bobbin 12 is wound with a focusing coil and a tracking coil (not shown). By energizing each coil, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke attached to the fixed portion 13 and the magnet attached to the yoke.

The above-mentioned structure is similar to that of the biaxial actuator 10 shown in FIG. 1, but in the biaxial actuator 10 according to this embodiment, the leaf spring 2 is further added.
1 is formed so as to be folded back in the opposite direction on the way. That is, the leaf spring 21 extends from the point a, which is the connection point to the lens holder 11, to the intermediate point b toward one side.
It is composed of a first portion 21a extending to the point and a second portion 21b extending from the point b to the opposite side to a point c which is a connecting point to the fixing portion 13. In this case, the first portion 21a of the leaf spring 21 is directly connected to the first portion 21a extending in the longitudinal direction with respect to the lens holder 11.

The biaxial actuator 20 having such a configuration
According to the above, the biaxial actuator 10 shown in FIG.
Since the first portion 21a extending in the longitudinal direction of the leaf spring 21 is directly connected to the lens holder 11, it has a small size as a whole.

Therefore, in the above-described embodiment, since the leaf spring supporting the lens holder is formed so as to be folded back in the opposite direction from the middle, the lens holder is substantially always moved in parallel. Therefore, the structure is simplified, and the processing cost and the assembly cost are reduced. Further, since the lens holder is supported only by the pair of leaf springs with respect to the fixed portion, the lens holder and the biaxial actuator as a whole are made thin.

The thickness or width of the leaf spring can be increased, and conversely, the movable portion of the biaxial actuator can be reduced in weight. When the leaf spring is laterally connected to the lens holder, the leaf spring is connected to the lens holder by a method similar to the conventional one. Therefore, the leaf spring can be easily attached to the lens holder by a method similar to the conventional method.

When the leaf spring is connected to the lens holder in the longitudinal direction, the overhanging dimension of the leaf spring becomes relatively small on both sides of the lens holder. Therefore, the biaxial actuator is compact in size as a whole.

In the above embodiment, the biaxial actuators 10 and 20 are formed in a "U" shape at a point b which is an intermediate point between the leaf springs 14 and 21. It is obvious that the same effect can be obtained without being limited to the “U” shape, or if the entire shape is “V”.

[0041]

As described above, according to the present invention, the lens holder is held in parallel by the pair of leaf springs so that the entire lens holder can be made thin and at low cost. A shaft actuator can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a biaxial actuator for an optical pickup according to the present invention.

FIG. 2 is a schematic plan view showing the configuration of the biaxial actuator shown in FIG.

FIG. 3 is a schematic view showing a deformed state of a leaf spring in the biaxial actuator of FIG.

FIG. 4 is a schematic plan view showing the configuration of a second embodiment of the biaxial actuator for optical pickup according to the present invention.

FIG. 5 is a schematic perspective view showing an example of a conventional biaxial actuator for an optical pickup.

6 is a schematic view showing a deformed state of a leaf spring in the biaxial actuator of FIG.

[Explanation of symbols]

 10 biaxial actuator 11 lens holder 11a objective lens 12 coil bobbin 13 fixed part 14 leaf spring 14a first portion 14b second portion 15 yoke 20 biaxial actuator 21 leaf spring 21a first portion 21b second portion

Claims (4)

[Claims] 1. A lens holder for holding an objective lens, a coil bobbin attached to the lens holder, and a focusing coil and a tracking coil wound around the coil bobbin, wherein the lens holder is a plate. An optical system comprising a pair of leaf springs supported by a fixed portion via springs, wherein the leaf springs have a portion that deforms in one direction and a portion that deforms in the opposite direction. Biaxial actuator for pickup. 2. The leaf spring according to claim 1, wherein the leaf spring includes a portion extending from the fixing portion, a turn-back portion following the turn-back portion, and a portion connected to the lens holder from the turn-back portion. Biaxial actuator. 3. The biaxial actuator according to claim 1, wherein the leaf spring is connected to the lens holder so as to extend laterally. 4. The biaxial actuator according to claim 1, wherein the leaf spring is connected to the lens holder so as to extend in the longitudinal direction.