JPS60182024A - Objective lens driver - Google Patents

Abstract

PURPOSE:To keep the linearity of displacement of driving force in the optical direction in a good state and to reduce the amplitude of vibration in the track direction at the same time by constituting the driver that an objective lens assembly side and a stationary side are connected by a vibration absorbing member while a rigidity reducing part is clipped. CONSTITUTION:A hole 14 to which the objective lens assembly 3 is inserted is provided to the center of an objective lens support member 2 and four plate springs 17 are provided between the objective lens assembly side 15 and the fixed side 16. The plate springs 17 are prolonged in the same rotation direction on a tangential line of a circle taking the optical axis of the objective lens as the center and arranged in point symmetry. A lengthwise rigidity reducing part 17a is formed by bending a part in the lengthwise direction at right angles. Moreover, a vibration absorbing member 18 made of an elastic body such as rubber is connected to one face of the plate springs 17 while clipping the lengthwise direction rigidity reducing part 17a to connect the lens assembly side and the fixed side.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a driving device for driving an objective lens of an optical disc in the optical axis direction, and is suitable for suppressing vibration in a direction perpendicular to the optical axis. The present invention relates to an objective lens driving device.

[Background of the invention]

Objective lens that drives the objective lens only in the optical axis direction,
The driving device is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-117133 and No. 11? As disclosed in JP-A-58-85939, a lens barrel to which an objective lens is fixed is supported by a thinly wound plate spring. An elastic member having a vibration-absorbing effect is bonded to this thinly wound spring to reduce vibrations in the optical axis direction of the objective lens and in a direction perpendicular thereto, thereby improving focusing and trunk positioning accuracy. However, in the case of a spiral leaf spring, the relationship between the driving force and displacement in the optical axis direction is highly nonlinear, and the gain in the low frequency region of focusing control varies greatly depending on the position in the optical axis direction. There is a problem with this.

On the other hand, the shape of the spring was changed to a spiral shape, for example,
As disclosed in Japanese Patent No. 168021, there is a plate spring made into an elongated straight line.

In this case, the relationship between the driving force in the optical axis direction and the displacement becomes close to linear, which is improved compared to a thinly wound leaf spring.

However, when we assembled a head using this elongated linear leaf spring and measured the frequency characteristics of the amplitude of the objective lens in the track direction (track positioning direction), we found that the vibration absorbing member such as rubber was not bonded. In this case, large peaks occurred in the dragging error near 2500/lt and 3800/A+, and when a vibration absorbing member such as rubber was bonded, a large peak in the tracking error occurred near 38001A. The vibration of 3800//g is a vibration in a mode in which one of the springs facing the track direction is stretched and the other is knitted. It has been found that even if a vibration absorbing member is attached to the leaf spring 1, the vibration is not reduced.

On the other hand, the vibration of the 250 Q IA+ is caused by the fact that when the leaf spring facing the track direction is initially deformed and the leaf spring undergoes bending deformation vibration, the lens barrel attachment part of the leaf spring will be displaced in the track direction. This is caused by e. This vibration can be reduced by attaching a vibration absorbing member such as rubber.

As explained above, in the conventional objective lens support spring,
Vibration absorbing members such as rubber for reducing low vibration: Even when used in combination, it was difficult to maintain good linearity of the driving force and displacement in the optical axis direction, while at the same time suppressing vibrations in the track direction.

[Object of the invention] The object of the invention is to drive the Americas in the J direction! [Summary of the Invention] The object of the present invention is to provide an objective lens drive shell that can maintain good linearity of displacement and at the same time reduce the vibration system at the track position. [Summary of the Invention] Vibration in the 1[Ii direction is caused by the in-plane deformation (stretching or bending) and out-of-plane deformation (bending) modes of the spring, but since it is difficult to reduce vibration in the in-plane deformation mode, emphasis is placed on countermeasures for this f: u
We decided to determine the shape of the spring. In order to reduce vibration, it is essential to increase the proportion of strain energy generated in vibration absorbing members such as rubber among the strain energy during vibration deformation, but countermeasures to this end will lower other characteristics. must not.

In order to compensate for the shortcomings while maintaining the advantages of the elongated straight plate spring from these four points, one end of the spring is bent to reduce the stiffness of the spring in the in-plane deformation mode. Both 1ills sandwiching the 1ill are connected by a vibration absorbing member, and the in-plane deformation mode is allocated by increasing the strain energy generated in the vibration absorbing member during in-plane deformation.

[Embodiments of the invention]

Embodiment f of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram of an optical disk device equipped with a cutting lens driving device according to the present invention.

At the top of the tip of the head body 1, there is an objective lens support member 2.
A lens barrel 4 supporting an objective lens assembly 3 is mounted and connected thereto. Light B emitted from the light source 5 passes through the beam splitter b, is reflected by the galvanometer mirror 7 for adjusting track position, passes through the objective lens assembly 3, is reflected by the optical disk 8, and passes through the same path again to the beam splitter. 6, enters a detection optical system 9, and outputs data on the surface of the optical disk 8, focusing error, and track position error.

In the apparatus of the type shown in FIG. 1, the objective lens assembly 3 is easily movable in the focusing direction, in the track direction and in the jitter direction (direction perpendicular to the track direction and the focus direction).
The amount of movement must be less than the allowable value (approximately 0.1 μ?n). Since the 0 jitter direction is approximately the same as the track direction, the following explanation will be made only in the track direction. In order to satisfy the condition No. 111, the lens support member 2 needs to satisfy the following condition.

(1) The stiffness KA in the focusing direction is small, the damping is large, and it is almost constant in the operating range.

(2) Greater rigidity and damping in the track direction.

The objective lens assembly 3 has a driving force FA for focusing.
It receives acceleration αTitαT2 in the track direction from the L lens barrel. The focusing driving force FA is generated in the voice coil 13 disposed within the magnetic gap formed by the permanent magnet 10 and the yokes 11 and 12. Permanent magnet lO and yoke 11. The head body 1 vibrates due to the reaction force of the force FA of the voice coil 13 generated by IIC, and acceleration αT1+αT2 in the track direction is generated in the lens barrel 4. This acceleration αT1+αT2 is applied to the lens support member 2 to cause the objective lens assembly 3 to vibrate in the track direction.In order to satisfy the conditions (1) and t(2), the objective lens support member 2 is For example, the structure is as shown in FIG.

In FIG. 2, the objective lens support part @2 is provided with a hole 14 in the center into which the objective lens assembly 3 is inserted, and four leaf springs 17 are provided between the objective lens assembly side part 15 and the fixed side part 16. is provided.

This leaf spring 17 extends in the same rotational direction on a tangent to a circle centered on the optical axis of the objective lens, and is arranged in a pair of points. The leaf spring 17 is formed with a longitudinal stiffness reducing portion 17a in which a portion of the longitudinal direction is bent at right angles.

Further, a vibration absorbing member 18 made of an elastic material such as rubber is bonded to one side of the leaf spring 17, sandwiching the longitudinal stiffness reducing portion 17a and connecting the objective lens assembly side and the fixed side portion. It has been done.

The reason why this lens support member is effective and the desirable conditions will be explained below.

Figure 3 shows the objective lens assembly 3 facing downward in the focusing direction.
This figure shows the deformed state of the plate spring 17 and the vibration absorbing member 18 when the plate spring 17 and the vibration absorbing member 18 are displaced. The plate spring 17 is restrained by the tSa portion when the vibration absorbing member 182 is used. At the same time, a relatively large strain is generated in the rubber tSa portion, damping the vibration. Since the leaf spring 17 is restrained from deformation by the vibration absorbing member 18, the portion of the leaf spring 17 that acts as a spring is the La-Lc portion of the leaf spring 17.
If the thickness of 7 is ta and the Young's modulus is Ea, then the length is La
-Lc) stiffness KA of the leaf spring in the focusing direction is CO
Since it is expressed by equation (1) with KA as a constant, KA is selected so as to be small considering other conditions.

In order to reduce the change (nonlinearity) of the stiffness KA depending on the position in the focal direction, it is desirable to increase (La Lc) r 1a. In addition, in order to increase the damping of vibrations in the focusing direction of the objective lens assembly 3, the objective lens assembly 3 should be moved along the dotted line A in the focusing direction as shown in FIG.
It is necessary to increase the ratio of the strain energy generated in the vibration absorbing member 18 to the total strain energy when the state is displaced from the state shown by the solid line B to the state shown by the solid line B, and it is desirable that Lc be large.

If the thickness tb of the vibration absorbing member 18 is small, or if the DC in the gap 18a of the vibration absorbing member 18 is small, the restraint by the vibration absorbing member 18 is too thick and the low dynamic absorbing member 18
deformation is small, and the strain generated in the vibration absorbing member 18 is too small for damping to be effective. In this case, the rigidity KA is also large, which is also undesirable. On the other hand, if 1b is small or DC is small, the stress generated in the vibration absorbing member 18 is small, and damping may or may not be effective, but the rigidity KA
is small, which is desirable in this respect. In between these, there is a range in which damping is effective to some extent and the rigidity KA is also below the allowable value. As mentioned in item iJ, it is desirable to increase the length of La-Lo. From this point, a perpendicular line drawn from the center of the objective lens assembly 3 to the leaf spring 17 and a vertical line drawn from the center of the objective lens assembly 3 to the leaf spring 17
It is advisable to arrange the junction point of the leaf spring 17 with the objective lens assembly side part 16 and the junction point with the fixed foot middle side part 15 on the prescription side, across the intersection of the two.

FIG. 4 shows the deformation state of the leaf spring 17 and the vibration absorbing member 18 in the in-plane deformation mode. In order to suppress the displacement in the track direction to a sufficiently small level, the resonant frequency in the track direction is sufficiently set and the vibration absorption member 18 is sufficiently damped. is required to be large. F3i claimed as a characteristic of the focusing direction
2 conditions of 1 and resonance 1L between tracks: If the only condition is to place a sufficient wave number, it is possible to use an elongated wireless leaf spring and a structure in which a vibration absorbing member is bonded to this leaf spring.
With this method, it was not possible to suppress vibrations in the in-plane deformation mode. This is because the part where the vibration absorbing member is connected is close to the fixed point of the leaf spring, so when the vibration absorbing member undergoes in-plane deformation, the strain on the vibration absorbing member is small, and damping is not effective because it absorbs less strain energy. be. In order to improve this, deformation of the part to which the vibration absorbing member is joined)11. This can be achieved by changing the shape of the spring so that it becomes larger, or by bending the fixed side 117a of the leaf spring 17 at a right angle as shown in FIG. Leaf spring 17 and vibration absorbing member 1
8 is deformed as shown in FIG. 4, the gap portion 18a of the vibration absorbing member 18 has a large strain, and this portion contributes most to vibration suppression. The leaf spring 17 has a stiffness K in the focusing direction.
Since it is elongated to reduce A k, the in-plane bending +N11I property is small, and the rigidity in the longitudinal direction is sufficiently large, so the rigidity KTR when displaced in the TR direction in Fig. 4
is approximately +116 (which can be determined by formula 21. CI is a constant.

Further, the resonance frequency FTa is expressed by equation (8) where M2 is the mass per spring of the objective lens assembly 3.

In order to make the resonant frequency F'TR more than the target value, 1, K
It is necessary to make the TR thicker, but the vibration absorbing member 18
In order to increase the displacement in the track direction (x direction) of the gap portion 18H, KTR must be small.

Make sure that the dimension KTR of the fixed side 17a of the plate spring 17 is not too thick.
The stiffness of the vibration absorbing member 18 is also added to the value of KTR, but it is usually smaller than the stiffness of the leaf spring 17, so it is determined by the leaf spring 17. Ru.

FIG. 5 shows the out-of-plane deformation mode of the leaf spring 17 and the vibration absorbing member 18. The amplitude of the out-of-plane deformation mode is largest near the center of the length of the leaf spring 17 when the width and thickness of the leaf spring 17 are the same. 17, and 7 has a width that becomes wider near the part that bends at a right angle. The vibration absorbing member 18 receives strain by restraining the leaf spring 17 near the bent portion thereof, thereby suppressing vibration.

Even in the out-of-plane deformation mode, the gap portion 18a of the vibration absorbing member 18 receives the largest strain and therefore contributes most to vibration suppression.

It is not preferable to bend the fixed side 17a of the plate spring 17 in the opposite direction to that shown in FIG. 2 because this increases the outer diameter of the spring.

In addition to the embodiments described above, other embodiments based on the same principle are possible. FIG. 6 shows a case where the fixed plate spring 17 of the embodiment shown in FIG. 2 is moved to the objective lens assembly 3 side. In the figure, 19 is a leaf spring, and 19a is a portion corresponding to the above-mentioned 17a. In this case, since the fixed side and the objective lens assembly have been exchanged, if the vibration absorbing member 20 is also placed on the objective lens assembly side, the same function as in the embodiment shown in FIG. 2 can be provided. If the vibration absorbing member 20 is made circular, the leaf spring 17 will be restrained to the outside of the pinion 9, and the leaf spring 17 will be restrained to the outside of the pinion 9.
If 9 is not long, the stiffness KA in the focusing direction will become too large. The thousandth potato map is leaf spring 17 in Figure 2.
The fixed side portion 17a of
This is the case if you can learn. Even in this case, the same effect as in FIG. 2 can be obtained. In the example shown in FIG. 8, the fixed side 21a of the plate spring 21 is not directly joined to the fixed side part, but is fixed via a part 21c bent at a right angle again.
It can be considered that a stiffness reducing part for in-plane deformation by the spring 21b is provided in the middle of the spring having the length of the sum of the leaf springs 21 and 21c, and the leaf spring 17 shown in FIG. All of the examples with 0 or more leaf springs, which are considered to be digitized, have four leaf springs, but in principle, the objective lens extends in the same direction of rotation on the tangent of the same circle centered on the optical axis of the lens. If the supporting members are disposed on the same plane and spaced apart by equal angles, then three or more supporting members can be provided with isodirectional properties instead of four. 2IIIl! In the case of 1, the characteristics are different in the longitudinal direction and the width direction of the spring, so it is generally not preferable.

Although the vibration absorbing members shown in FIGS. 2 and 6 to 8 are all bonded to one side of the leaf spring, the same effect can be achieved even if the vibration absorbing members are bonded to both sides.

Furthermore, as explained in the embodiment shown in FIG. 2, the planar shape of the vibration absorbing member can be any shape as long as it includes the part that contributes most to vibration damping, as long as it does not have any other negative effects on the characteristics. may be plural.

[Effect of the invention J According to the present invention, in a specific direction (focusing direction), 1F4
It is possible to provide a support spring that has low 1J characteristics, excellent linearity, and appropriate damping, and suppresses amplitudes in other directions (track direction, jitter direction) to a sufficiently small level, resulting in highly accurate track position 1. It is possible to realize phase change in loaf determination and furthermore, it is an original disk device with high track density f! : There is an effect that can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical disk device equipped with an objective lens driving device of the present invention, FIG. 2 is a plane mj diagram explaining in detail an example of the objective lens support member in FIG.
Figures 4 and 5 are diagrams for explaining the deformation of the objective lens support when the objective lens support is displaced in the focusing direction. The explanatory diagrams, FIGS. 6 to g8, are diagrams illustrating other examples of the objective lens support member in the objective lens driving device of the present invention. 2... Objective lens support member, 3... Objective lens assembly. 4... Lens barrel, 17.19.21... Leaf spring, 18,
20... Vibration absorbing member. ;1”1 mouth size 2121 year old 4 white 17 omu;li3 figure

Claims (1)

[Claims] 1. In an objective lens drive device comprising a plurality of objective lens support members extending in the same rotational direction on tangents to concentric circles centered on the optical axis of the objective lens, the objective lens support members are arranged on the same plane. At the same time, a part for reducing the stiffness in the longitudinal direction is provided in a part of the longitudinal direction of the linear spring, and the stiffness reducing part described in 11. An objective lens driving device characterized in that the objective lens assembly side and fixed side portions are connected by a vibration absorbing member. 2. The objective lens driving device according to claim 1, characterized in that a part of the substantially linear spring is bent at a substantially right angle to form a part that reduces longitudinal rigidity.