JPH08147738A - Objective lens driving device - Google Patents

Abstract

PURPOSE: To reduce adverse effects of higher harmonics resonance by setting a gain increase amount of the natural resonance frequency of an actuator movable part at a low level. CONSTITUTION: An elastic member 7 is provided between driving coils 5 and 6 and a lens holder 2 or between an objective lens 1 and the lens holder 2. By using the elastic member 7, the actuator movable part is displaced toward the objective lens 1 and the driving coils 5 and 6 with phase shifts in relation to frequencies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device in an optical pickup.

[0002]

2. Description of the Related Art As is well known, an objective lens driving device provided in an optical pickup for optically reading or writing a signal using a laser beam is generally known as a focusing coil mounted on a lens holder on which an objective lens is mounted. And the drive coil of the tracking coil is installed,
The objective lens is driven while performing focus control and tracking control according to the drive signals respectively supplied to the drive coils.

In the objective lens driving device, the actuators for displacing the objective lens have natural resonance frequencies in the focus control system and the tracking control system, respectively. This natural resonance frequency is directly related to the higher-order resonance of the objective lens driving device, and since this higher-order resonance gives harmful vibration to the objective lens, the natural resonance frequency of each control system is taken into consideration in the objective lens driving device. The high-order resonance of each control system is designed to be outside each servo band.

[0004]

By the way, in the optical disk device using the optical pickup, the standard speed of 2 is used.
The speed of rotating the disk is doubled and quadrupled, and the signal is read at high speed by the optical pickup.
Alternatively, it has become necessary to write data. When the speed of reading and writing signals is increased, each servo band of each control system must be widened and expanded to a high range, so a margin between each servo band and high-order resonance must be secured. Becomes difficult and higher-order resonance easily occurs, which causes a problem.

Further, in the objective lens driving device of the optical pickup used for the standard speed optical disk device, unless the gain increase of the natural resonance frequency of the actuator moving part itself is set low by a good design, the circuit phase compensation is performed. In addition to increasing the load due to, the adverse effect of higher-order resonance is likely to be large, which is disadvantageous for improving the characteristics.

In view of this problem, the present invention sets the gain increase amount of the natural resonance frequency of the actuator movable portion to be low, and obtains good servo characteristics.

[0007]

According to the present invention, an elastic member is interposed between the drive coil and the lens holder or between the objective lens and the lens holder to connect them.

Further, according to the present invention, the bobbin portion for mounting the drive coil of the lens holder is separated from the lens holding portion to which the objective lens is fixed, and the bobbin portion and the lens holding portion are interposed by an elastic member. Are connected.

[0009]

According to the present invention, the elastic member is used to displace the actuator movable portion between the objective lens side and the drive coil side with a phase shift in relation to the frequency so that the frequency is lower than the natural resonance frequency of the actuator movable portion. The resonance point is formed at. By doing so, the driving force generated in the driving coil is attenuated and transmitted to the objective lens, and the increase in the gain of the natural resonance frequency of the actuator movable portion is suppressed to a low level.

[0010]

1 is a perspective view showing an embodiment of the present invention, in which a magnetic circuit portion and a frame which are not directly related to the gist of the present invention are omitted and only an actuator movable portion is shown.

In FIG. 1, a lens holder 2 on which the objective lens 1 is mounted is connected with four supporting wires 3 for suspending the lens holder 2 so that the lens holder 2 can be displaced with respect to a frame (not shown). Pieces 4 are provided so as to project from both upper and lower surfaces of the lens holder 2 on both sides of the objective lens 1 depending on the installation position of each support wire 3.

Further, the lens holder 2 has a focusing coil 5 having a winding center axis in the optical axis direction of the objective lens 1 and a winding center axis in a direction orthogonal to the optical axis of the objective lens 1, A pair of tracking coils 6 which are divided into two by sandwiching the lens 1 are wound, and the lens holder 2 is also used as a bobbin.

By the way, an elastic member 7 such as a silicone rubber or a butyl rubber is attached to the portion of the lens holder 2 around which the focusing coil 5 is wound. Then, the focusing coil 5 is wound. Therefore, focusing coil 5
Will be mounted on the lens holder 2 with the elastic member 7 interposed.

In the objective lens driving device constructed as described above, the objective lens 1 is related to the frequency in the focusing control system of the actuator movable portion by the elastic member 7.
A phase shift of each displacement is generated between the side of the lens holder 2 on which the lens is mounted and the side of the focusing coil 5, and a resonance point is formed due to the phase shift.

Here, the resonance point is set outside the focus servo band due to the material and thickness of the elastic member 7 and at a frequency lower than the natural resonance frequency of the actuator movable portion in the focusing control system. Therefore, the driving force generated in the focusing coil 5 is attenuated (-12 dB / oct) without deteriorating the gain characteristic in the focus servo band, and the lens holder 2
The gain increase of the natural resonance frequency of the actuator movable portion in the focusing control system is suppressed to a low level by being transmitted to the objective lens 1 via

Therefore, it is possible to reduce the adverse effect of higher-order resonance in the focusing control system. still,
Although FIG. 1 shows the objective lens driving device in which the elastic member 7 is interposed only in the portion of the lens holder 2 around which the focusing coil 5 is wound, the lens holder 2
Even in the portion where each tracking coil 6 is wound, the elastic member 7 is interposed at the position where the tracking coil 6 comes into contact, so that the gain increase of the natural resonance frequency of the actuator movable portion in the tracking control system is increased in the same manner as the focusing control system. Can be kept low,
It goes without saying that this may be done.

If an adhesive having elasticity, for example, a silicone rubber adhesive or a modified acrylic adhesive is used to mount the focusing coil 5 and each tracking coil 6, the adhesive is used as the elastic member 7. You can

In FIG. 1, the elastic member 7 is interposed between the drive coil and the lens holder 2, but the objective lens 1 and the lens holder 2 are described.
An elastic member 7 may be interposed between the objective lens 1 side and the drive coil side so that the objective lens 1 side and the drive coil side are displaced with a phase shift in relation to the frequency.

FIG. 2 shows an objective lens driving device showing another embodiment. In FIG. 2, the lens holder 8
Is a lens holder 10 to which the objective lens 9 is attached, a focusing coil 11 and each tracking coil 12
Is formed separately from the bobbin portion 13 around which is wound,
The bobbin portion 13 is bonded and bonded to the lens holding portion 10 by an elastic member 14 made of an adhesive.

The lens holding portion 10 and the bobbin portion 13 have
Holes 10a and 13a are formed, respectively, and a permanent magnet 15, an outer yoke 16 and an inner yoke 17, which form a magnetic circuit that generates a magnetic field applied to the focusing coil 11 and each tracking coil 12, are inserted. ing.

Further, the bobbin portion 13 is provided with a connecting piece 20 for connecting each supporting wire 19 for movably suspending with respect to the frame 18 in accordance with a position where each supporting wire 19 is installed. The lens holding unit 10 is displaceably supported via the unit 13.

In the objective lens driving device of FIG. 2, as described above, the lens holding portion 10 and the bobbin portion 13 which are separate bodies are connected by the elastic member 14. For that reason,
In both the focusing control system and the tracking control system of the actuator movable part, a phase shift of each displacement between the lens holding part 10 side and the bobbin part 13 side is generated in relation to the frequency, and due to the phase shift. A resonance point is formed.

Here, the resonance point in each control system is set outside each servo band and at a frequency lower than the natural resonance frequency of the actuator moving part in each control system. Therefore, the driving force generated in each driving coil is attenuated and transmitted to the objective lens 9 via the lens holding unit 10 without deteriorating the gain characteristic in each servo band, and the actuator moving unit in each control system is The gain increase of the natural resonance frequency of can be suppressed low.

Therefore, the bobbin portion 13 is preferably formed as a separate body without independently interposing an elastic member in the focusing coil 11 and each tracking coil 12 and in view of workability of winding each drive coil. The adverse effect of higher order resonance in each control system can be reduced only by performing the work of coupling to the lens holding unit 10.

[0025]

As described above, according to the present invention, an elastic member is used to displace the actuator movable portion between the objective lens side and the drive coil side with a phase shift in relation to the frequency. Since the resonance point is formed at a frequency lower than the natural resonance frequency of the movable part of the actuator, the driving force generated in the drive coil is attenuated and transmitted to the objective lens. It is possible to suppress the gain increase amount of 1 to be low, and to reduce the adverse effect of higher-order resonance.

Further, according to the present invention, the bobbin portion, which is preferably formed as a separate body in view of workability for winding the drive coils, is formed separately from the lens holding portion on which the objective lens is mounted,
Since the bobbin portion and the lens holding portion are coupled by interposing an elastic member therebetween, a single driving coil of a plurality of control systems such as a focusing coil and a tracking coil can be formed independently without interposing an elastic member. At the same time, the increase in the gain of the natural resonance frequency of the movable portion of the actuator in each control system is suppressed to a low level by the elastic member, and it is possible to provide an objective lens driving device which has good workability and reduces adverse effects due to higher order resonance.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a main part of the present invention.

FIG. 2 is a plan view showing another embodiment of the present invention.

[Explanation of symbols]

 1,9 Objective lens 2,8 Lens holder 5,11 Focusing coil 6,12 Tracking coil 7,14 Elastic member 10 Lens holding part 13 Bobbin part

Claims (2)

[Claims] 1. An objective lens driving device, wherein a driving coil is mounted on a lens holder on which an objective lens is mounted, and the objective lens is driven according to a driving signal supplied to the driving coil. An objective lens driving device, characterized in that an elastic member is interposed between a holder or between the objective lens and the lens holder. 2. An objective lens driving device, wherein a driving coil is mounted on a lens holder on which an objective lens is mounted, and the objective lens is driven according to a driving signal supplied to the driving coil. An objective lens driving device characterized in that a bobbin portion for mounting a coil is provided separately from a lens holding portion for mounting an objective lens, and the bobbin portion and the lens holding portion are coupled with an elastic member interposed.