JPH03113839A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To surely realize the control of focusing and tracking by providing a vibration proofing or vibration absorbing means for attenuating the vibration to an objective lens, on a bobbin. CONSTITUTION:In a bobbin 31, plural vibration proofing or vibration absorbing means provided with a weight 74, which are positioned on its outside peripheral surface and formed by superposing a vibration proofing or vibration proofing or vibration absorbing member 73 such as rubber having a damping property, etc., are installed. According to such a constitution, when a current is supplied to a coil, and the bobbin 31 is brought to up-and-down motion or rotation by electromagnetic force, a deformation of the bobbin 31 in a resonance area decreases, and a resonance peak value is also improved relatively. In such a way, positioning of the bobbin 31, that is, an objective lens 34 can exactly be executed, and the control of focusing and tracking is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an objective lens driving device for an optical head used primarily in an optical or magneto-optical information recording/reproducing device.

(Prior Art) This type of optical or magneto-optical information recording/reproducing device records information on an information recording medium such as an optical disk,
When reproducing or erasing recorded information, a beam of light emitted from a light source such as a semiconductor laser is passed through an optical system, in particular an objective lens, onto a recording medium with a diameter of 1 μm.
It has been attempted to focus the light onto a very small spot.

Such information recording and reproducing devices usually use focusing control to correct out-of-focus caused by surface wobbling of the information recording medium, or to correct positional deviation of the light beam spot caused by eccentricity of the center of rotation of the information recording medium. Tracking control is performed for correction. For this reason, in Japan, a device configured as shown in FIG. 2 is known as a device for driving an objective lens.The objective lens 2 is held by a bobbin 6, and the bobbin 6 has a bearing at the center of rotation. 4, and is movable in the rotation direction and axial direction with respect to the rotation center shaft 16 inserted therein. If necessary, a weight 5 is provided on the bobbin 6 axially symmetrically with the objective lens 2 to maintain the weight balance with respect to the rotation center axis 16. A focusing coil 7 is wound around the outer periphery of the bobbin 6, and furthermore, tracking coils 8 are placed on top of this coil 7 at equal intervals in the circumferential direction.
is pasted. Permanent magnets 9a and 9b are installed near the outer periphery of the 5 bobbin 6 facing the coils 7 and 8. The permanent magnet 9a.

9b is the outer yoke 11a, l formed on the bottom yoke 12.
It is attached to the outer yoke lla, llb.
Inner yoke lOa corresponding to.

tab is also on the bottom yoke 12, its permanent magnet 9a,
It is attached inside the position 9b.

The inner yokes 10a, 10b are inserted into half-moon-shaped engagement holes 6a, 6b formed in the bobbin 6. Further, the rotation center shaft 16 described above is embedded in the bottom yoke 12. In this way, the bottom yoke 12, the outer yokes lla, llb, and the inner yokes 10a, 10b,
Electromagnetic yoke 13 (magnetic field generating means) made of ferromagnetic material as a whole
It consists of Therefore, since a magnetic field is generated across the coils 7 and 8, an electromagnetic force is generated when the coils 7 or 8 are energized, and the bobbin 6 is moved to the rotation center axis 1.
6 or in the axial direction.

In the figure, reference numeral 16 denotes an optical head, which has an image shape and has a bearing part 19a that receives the guide rail so that it can move along a parallel guide rail (not shown).
19b. Note that the conventional example shown here employs a separate optical system, in which fixed optical systems such as a light source and a sensor are fixedly arranged separately, and an objective lens 2 and a folding mirror (not shown) as a movable optical system are arranged separately. It is arranged on the optical head 16 side. For this reason, a notch 12a is formed in the bottom yoke 12 so as not to obstruct the light flux to the objective lens 2, and a notch 12a is formed in the optical head 16 to ensure an optical path for the above-mentioned folding mirror disposed inside the optical head 16. The light flux holes 17 and 20 are provided.

The bottom yoke 12 has a mounting hole 14 bored therein.
a, 14b = - to the screw holes 15a, 15 of the optical head 16
It is screwed on with screws etc. according to b...

(Problems to be Solved by the Invention) However, in such an objective lens driving device, the bobbin 6 is moved vertically in FIG.
When controlling the drive in the focus direction, as a result of driving in a high frequency range of 10 kHz or more, there is a risk that resonance may occur because the frequency overlaps with the natural frequency range of the bobbin 6. For this reason, there is a drawback that accurate position detection becomes impossible and control becomes impossible.

A simulation showing the problematic resonance and deformation of the bobbin 6 is shown in FIG. Although it is important here to control the position of the human output beam 61 of the laser beam, it is recognized that bending vibration is acting on the horizontal portion 60 at the center of the bobbin, causing the human output beam 61 to be swayed. It will be done.

(Object of the Invention) The present invention has been made based on the above circumstances, and is designed to prevent the bobbin from resonating in the high frequency range used when performing focusing and tracking control of the objective lens. It is an object of the present invention to provide an objective lens driving device configured to attenuate the vibration and provide good vibration characteristics as an objective lens holder.

(Means for Solving the Problems) Therefore, in the present invention, the objective lens is held on a bobbin that is movable in the rotational direction and the axial direction with respect to the rotation center axis,
The bobbin includes a focusing coil and a tracking coil, and includes magnetic field generating means for generating a magnetic field that crosses each of these coils.

In an objective lens drive device that drives the bobbin in the rotational direction and the axial direction by controlling the current to the coil, the vibration isolating or vibration absorbing means includes a vibration isolating or absorbing member and a weight for attenuating vibrations to the objective lens. is arranged on the above bobbin.

(Function) Therefore, the vibration characteristics of the bobbin in the high frequency range used can be improved, and by attenuating the resonance peak, the objective lens can be positioned accurately, and focus control and tracking control are not hindered.

(Example) An example of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, in which a bobbin 31 is provided with a bearing portion 32 at its rotation center, and the bearing portion 32 is fitted onto a rotation center shaft 33. and can be driven in the rotational and axial directions.

An objective lens 34 and a weight 35 are provided axially symmetrically on the bobbin 31, and a focusing coil 36 is wound around the outer periphery, and tracking coils 37a are arranged on the bobbin 31 at equal intervals in the circumferential direction. .

37b... is pasted. In addition, the coil 36
, 37a, 37b-=, the bobbin 31
Permanent magnets 47a and 47b are installed near the outer periphery of. The permanent magnets 47a and 47b are electromagnetic yokes 46a formed by bending plate-shaped ferromagnetic plates.

46b, the electromagnetic yoke 46
a and 46b are permanent magnets 47a, respectively.

An outer yoke portion 48a located outside of 47b.

48b and bottom yoke parts 53a, 53b, and inner yoke parts 54a, 54b located between the permanent magnets 47a, 47b.
a, 47b are the outer yoke 48a.

48b and the bottom yoke portions 53a and 53b.

Further, the inner yoke portions 54a, 54b are inserted into the engaging holes 31a, 3Ib of the bobbin 31. Further, the rotation center axis 33 is implanted on the upper surface of the carriage 38 of the optical head, so that each electromagnetic yoke 46a, 46b can be correctly positioned and fixed on the carriage 38. For this reason, the electromagnetic yokes 46a, 46b
The bottom surface of the carriage 38, that is, the bottom surface of the bottom yoke portions 53a, 53b, is provided with positioning pins 52a, 52b, . . .
, 50b and the positioning slot 51a.

51b is formed. Further, the carriage 38 has mounting holes 43a and 43b, through which screws 49a and 49b are screwed onto the electromagnetic yokes 46a and 46b, so that the electromagnetic yokes 46a and 46b are properly mounted on the carriage 38.
46b can be installed. Note that the carriage 38 is provided with bearing parts 44a, 44b that can be slid by fitting into a guide rail (not shown), and a light flux hole 41 corresponding to the optical path 39 to the objective lens 34 is provided.゜4
2, and a folding mirror 40 is disposed inside.

In particular, in the present invention, the bobbin 31 includes:
A plurality of vibration isolating or absorbing means are located on the outer circumferential surface thereof and have a weight 74 superimposed on a vibration isolating or absorbing member 73 made of rubber or the like having vibration damping properties.

I am wearing it.

With such a configuration, when current is supplied to the coil 7 or 8 and the bobbin 31 is moved up and down or rotated by electromagnetic force, deformation of the bobbin 31 in the resonance region is reduced,
The resonance peak value is also relatively improved, for example, by about 5 to 20 dB. Therefore, due to vibration damping, the positioning of the bobbin, that is, the objective lens, can be performed accurately, and focusing and tracking control can be ensured.

In another embodiment of the present invention shown in FIG. 4, the weight of the vibration isolating means or vibration absorbing means is also used as a weight 35 arranged axially symmetrically with respect to the objective lens 34. It is supported by the bobbin 31 via a vibration damping member 73.

In still another embodiment of the present invention shown in FIG. It is attached to the bobbin 31 via a member 73.

The above-mentioned vibration isolating means or vibration absorbing means in the present invention is prepared in order to achieve damping that depends on the resonance region of the bobbin, and its shape and configuration are other than those realized in the above-mentioned embodiments. It can be modified in various ways, and can be widely applied without departing from the technology of the present invention, such as by adding a spring member.

(Effects of the Invention) The present invention has been described in detail above, and since a vibration isolating or vibration absorbing means for attenuating vibrations to the objective lens is provided on the bobbin, current is applied to the focusing coil and the tracking coil in the high frequency range. Even if the objective lens position is not determined due to resonance, it is possible to avoid situations where the objective lens position cannot be determined even when focusing is performed.

The effect is that tracking control can be reliably realized.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing an embodiment of the present invention, Fig. 2 is an exploded perspective view of a conventional example, and Fig. 3 is a bobbin vibration (resonance region).
4(a) and (bl) are perspective views of another embodiment of the present invention and a cross-sectional perspective view of A-All in the same figure, and FIG. 5 is still another embodiment. It is a perspective view of 3I... Bobbin, 32... Bearing portion, 33-... Rotation center axis, 34-... Objective lens, 35-... Weight, 36
...Focusing coil, 37a, 37b--...Tracking coil, 46a, 46b...Electromagnetic yoke, 47a. 47 b--Permanent magnet, 73... Vibration isolating or vibration-absorbing member, 74...- Weight.

Claims (1)

[Claims] An objective lens is held on a bobbin that is movable in a rotational direction and an axial direction with respect to a central axis of rotation, a focusing coil and a tracking coil are provided on the bobbin, and a magnetic field generating means is provided for generating a magnetic field that crosses each of these coils. , an objective lens drive device that drives the bobbin in the rotational direction and the axial direction by controlling the current to the coil, which includes a vibration isolation or vibration absorption member and a weight for damping vibrations to the objective lens; An objective lens driving device characterized in that means is disposed on the bobbin.