JPS62236149A - Optical system driving device - Google Patents

Abstract

PURPOSE:To prevent the mixing of foreign matters and to decrease an inter- shaft sliding friction by fixing the closed edge part of an elastic member to an upper edge part of a supporting shaft so that the central shafts of both an elastic member and a supporting shaft are coincident. CONSTITUTION:The aperture edge of an elastic member is fixed to an optical type holding body 2 so that the central shafts of body an elastic member 7 and a bearing 6 are coincident and the closed edge part of the elastic member is fixed to the upper edge part of the supporting shaft so that the central shafts both the elastic member and a supporting shaft 8 are coincident. Thus, in a focus control, a neutral point is held by the restoring force to the whole expansion and reduction centering the central shaft of the elastic member, and also, in the tracking control, the neutral point is held by the restoring force to the whole twisting deformation centering the central shaft of the elastic member. Consequently, the invasion of the foreign matters to a bearing part is prevented and the inter-shaft sliding friction is decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical system drive device, and particularly to a base to which a support shaft is fixed, and a base that is rotatably and vertically slidable about the support shaft. an optical system holder having a bearing; a means for driving the optical system holder in the rotational direction and an axial direction about the support shaft; and a neutral point holder for returning the optical system holder to a neutral position in response to this drive. The present invention relates to an optical system driving device having a mechanism.

[Prior art]

In recent years, with the development of the information society, research and development have been actively conducted on optical information recording and reproducing devices that can accumulate large amounts of information and record or reproduce desired information in a short time. There is.

Hereinafter, an optical disk device will be explained as an example of an optical information recording/reproducing device.

Generally, in an optical disk device, information pits having a width of about 1 to 2 μm and a length of about 1 to 3 μm are formed on an information recording medium. To reproduce information from this information pit, first a light beam is focused onto a minute spot using an objective lens.
Irradiates the information pit. At this time, depending on the presence or absence of information pits, reflected light or transmitted light from the information recording medium changes optically. By detecting this change with a photodetector,
A reproduced signal corresponding to the information pits can be obtained.

In such an optical disk device, it is extremely important that the minute spot always accurately scan the information pit row on the information recording medium.

For this purpose, an autofocus function that corrects a focus shift caused by warpage of the information recording medium and an autotracking function that corrects an irradiation position shift caused by eccentricity of the information recording medium are required.

As a method for realizing this autofocus function and autotracking function, there is an objective lens driving device shown in FIG.

In FIG. 5, a bearing 6 is provided on the central axis of the cylindrical objective lens holder 2 for vertically sliding and rotating the objective lens holder 2 about a support shaft 8, and a bearing 6 is provided parallel to the central axis. An objective lens 1 that focuses the laser beam onto the information recording medium surface is fixed at a position away from the information storage medium 6. A focusing coil 5 is wound around the outer periphery of the objective lens holder 2, and tracking coils 3 and 4 are fixed onto the focusing coil 5.

The support shaft 8 is fixed to the base 13 by press fitting or the like, and the objective lens holder 2 is attached via a bearing 6.

A Teflon resin layer 8a is provided on the shaft surface of the support shaft 8 in order to reduce sliding friction with the bearing 6.

A tracking permanent magnet 9.10 is fixed to the base 13 so as to face the tracking coils 3 and 4, and a focusing permanent magnet 11.12 is fixed to the base 13 so as to face the focusing coil 5. Further, a through hole 14 is formed in the base 13 in accordance with the movable range of the objective lens 1.

The neutral point of the objective lens holder 2 is maintained by the neutral point holding rubber 1.
7, one end of this neutral point holding rubber 17 is attached to a pin 16 fixed to the objective lens holder 2, and the other end is attached to a support shaft 8 and pin 16a fixed to the base 13.
, 16b.

The focus control of the objective lens driving device is performed by controlling the current flowing through the focusing coil 5 and the focusing permanent magnet 11.
．． This is done by sliding the objective lens holder 2 up and down about the support shaft 8 using the magnetic field generated by the magnetic field 12 and the electromagnetic force.

Also, tracking control uses tracking coil 3.4.
This is done by rotating the objective lens holder 2 left and right about the support shaft 8 using the electromagnetic force of the electric current flowing through the tracking permanent magnet 9 and the magnetic field created by the tracking permanent magnet 9 and IO.

Next, the neutral point holding mechanism will be explained.

FIG. 6 is an explanatory diagram of the neutral point holding mechanism of the objective lens driving device, and FIG. 6(a) shows the case of focus control, and FIG. 6(bl shows the case of tracking control).

As shown in FIG. 6 (al), when the objective lens holder 2 is slid upward on the support shaft 8 and displaced by a distance X, the neutral point holding rubber 17 is deformed and a restoring force F is applied in the direction of the support shaft.
, works.

Further, as shown in the sixth opening), when the objective lens holder 2 is rotated left and right about the support shaft 8 and displaced by an angle θ, the neutral point holding rubber 17 is deformed and the restoring force F around the support shaft 8 is work.

[Problem that the invention seeks to solve]

However, in the above neutral point holding mechanism, in the case of focus control, the restoring force F2 acts not only in the direction of the support axis but also in the direction perpendicular to the support axis.
Also, in tracking control, since the holding force F acts from one side, misalignment occurs between the support shaft 8 and the bearing 6.
In addition, since the bearing portion between the support shaft 8 and the bearing 6 is exposed to the outside, foreign matter can enter, increasing the sliding friction between the shafts.
There was a problem that accurate focus servo and tracking servo could not be performed.

Further, since the neutral point holding rubber 17 is provided asymmetrically with respect to the support shaft 8, there is a problem in that a large amount of space must be taken up in the notch inside the cylindrical shape of the objective lens holder 2.

[Means for solving problems]

The above problem consists of a support shaft, an optical system holder having a bearing that is rotatable about the support shaft and slidable up and down, and a support shaft that rotates the optical system holder about the support shaft in a rotational direction and an axial direction. In the optical system driving device, the neutral point holding mechanism has one end open and the other end closed. an open end of the elastic member is fixed to the optical system holder so that the central axis of the elastic member coincides with the central axis of the bearing; The problem is solved by the optical system driving device of the present invention, characterized in that the closed end of the elastic member is fixed to the upper end of the support shaft so that the central axis coincides with the center axis of the support shaft.

[For production]

The optical system drive device of the present invention has a hollow elastic member with one end open and the other end closed, and the elastic member is arranged such that the center axis of the elastic member and the center axis of the bearing coincide with each other. The open end of the elastic member is fixed to the optical system holder, and the closed end of the elastic member is fixed to the upper end of the support shaft such that the center axis of the elastic member and the center axis of the support shaft coincide. As a result, in focus control, the neutral point is maintained by the restoring force against the overall expansion and contraction around the central axis of the elastic member, and also in tracking control, the neutral point is maintained against the torsional deformation of the entire elastic member around the central axis. Since the neutral point is maintained by the restoring force, it is possible to prevent lopsided sliding and tilting of the optical axis that occur between the shaft and the bearing. Since it is provided above the system holder, it is possible to prevent foreign matter from entering the bearing part and further reduce the space occupied by the elastic member of the optical system holder.

If a slit is provided in the side surface of the elastic member in parallel with the central axis of the elastic member, the elastic member will be easily deformed during tracking control, and unnecessary torsional deformation will not occur during focus control.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that an objective lens driving device will be described as an example of the optical system driving device of the present invention.

The same members as those of the objective lens driving device shown in FIG. 6 are given the same reference numerals.

FIG. 1 is an exploded perspective view of an embodiment of the objective lens driving device of the present invention.

In FIG. 1, a bearing 6 is provided on the central axis of the cylindrical objective lens holder 2 for vertically sliding and rotating the objective lens holder 2 about a support shaft 8, and a bearing 6 is provided parallel to the central axis. An objective lens 1 that focuses the laser beam onto the information recording medium surface is fixed at a position away from the information storage medium 6. A focusing coil 5 is wound around the outer periphery of the objective lens holder 2, and tracking coils 3 and 4 are wound around the focusing coil 5.

The support shaft 8 is fixed to the base 13 by press fitting or the like, and the objective lens holder 2 is attached via a bearing 6.

A Teflon resin layer 8a is provided on the shaft surface of the support shaft 8 in order to reduce sliding friction with the bearing 6.

A tracking permanent magnet 9.10 is fixed to the base 13 so as to face the tracking coil 3.4, and a focusing permanent magnet 11.12 is fixed to the base 13 so as to face the focusing coil 5. Further, a through hole is formed in the base 13 in accordance with the movable range of the objective lens 1.

The neutral point of the objective lens holder 2 is maintained by a neutral point holding rubber 7 which is an elastic member. FIG. 2+8) is a perspective view of the neutral point holding rubber 7, and FIG. 2(b) is a partial sectional view of the neutral point holding rubber.

The neutral point holding rubber 7 has a cylindrical shape with one end open and the other end closed, and as shown in FIG. 2(a), there is a slot 7) on the side surface. a are provided at regular intervals, and the shape is such that the neutral point holding rubber 7 is easily deformed. The open end 7b of the neutral point holding rubber 7 is fixed to the objective lens holder 2 so as to be coaxial with the central axis of the objective lens holder 2, and the inner surface of the closed end 7C is as shown in FIG. It is fixed to the upper end of the support shaft 8 so as to be coaxial with the central axis of the support shaft 8.

This neutral point holding rubber 7 holds the neutral point of the objective lens holder 2 and also performs damping, and also has a vibration damping effect. The shape of the neutral point holding rubber 7 is a truncated cone, a triangular prism,
Although it may be a regular prism such as a square prism, a cylindrical shape is most desirable because it generates a uniform restoring force throughout the neutral point holding rubber 7 against rotation about the support shaft and vertical sliding.

Focus control of the objective lens driving device is performed by applying current to the focusing coil 5 and the focusing permanent magnet 1.
This is done by sliding the objective lens holder 2 up and down about the support shaft 8 using the magnetic field and electromagnetic force generated by 1.12.

Also, tracking control is performed by tracking coils 3 and 4.
This is done by rotating the objective lens holder 2 left and right about the support shaft 8 using the electromagnetic force of the current flowing through the tracking permanent magnets 9 and 10 and the magnetic field generated by the tracking permanent magnets 9 and 10.

Next, the neutral point holding mechanism in this embodiment will be explained.

FIG. 3 is an explanatory diagram of the neutral point holding mechanism when tracking drive is performed. Figure 3 (a) is a plan view showing the objective lens holder during tracking drive, and Figure 3 (b) 4$
This is an explanatory diagram showing the state of the neutral point holding rubber at that time, and FIG. 3(e) is an explanatory diagram showing the effect of the neutral point holding rubber.

In FIG. 3(a), when the objective lens holder 2 is rotated by an angle θ due to the tracking drive, the neutral point holding rubber 7 is rotated in the direction of rotation without deformation of the slit portion 7a, as shown in FIG. 3(bl). At this time, a restoring force F4 acts on the neutral point holding rubber 7 as shown in FIG. 3(C).
An attempt is made to return the objective lens holder 2 to the neutral position. Since this restoring force F4 is generated by the torsional deformation of the entire neutral point holding rubber 7, it becomes a rotational force about the central axis of the neutral point holding rubber 7. As mentioned above, in this embodiment, the central axis of the neutral point holding rubber 7 coincides with the central axis of the objective lens holder 2, that is, the central axis of the bearing 6, and also coincides with the central axis of the support shaft 8. There is no deviation between the bearing 6 and the support shaft 8, and extremely stable tracking control is possible.

FIG. 4 is an explanatory diagram of the neutral point holding mechanism when performing focus drive. FIG. 4(a) is an explanatory diagram when the lens is held at the neutral position, and FIG. 4(a) is an explanatory diagram when the focus drive is performed.

The holding position of the neutral point is determined by the distance M from the recording surface of the information recording medium 15 to the upper end of the objective lens 1, as shown in FIG.
xt. Now, due to focus drive, the fourth
As shown in the figure (bl), when distance X1 becomes distance X2,
The neutral point holding rubber 7 deforms symmetrically about the central axis of the cylinder. At this time, the slit portion 7a is bent and deformed outward from the outer circumference of the cylinder, and the diameter of the outer circumference of the neutral point holding rubber 7 changes from A to B as shown in the figure, and the restoring force F5 generated by the land causes the objective lens to be held. The neutral point of the body 2 is maintained. By providing the slit portion in the neutral point holding rubber 7 as described above, the focus driving force is converted into a bending deformation force on the outside of the cylindrical outer circumferential portion, and it is possible to prevent the occurrence of torsional deformation.

〔Effect of the invention〕

As described in detail above, in the optical system driving device of the present invention, the neutral point holding mechanism has a hollow elastic member with one end open and the other end closed, and the center axis of the elastic member is The open end of the elastic member is fixed to the optical system holder so that the center axis of the bearing coincides with the center axis of the support shaft. By fixing the closed end to the support shaft, it is possible to prevent lopsided sliding and tilting of the optical axis that occur between the shaft and the bearing, and it is possible to perform accurate tracking servo and focus servo. In addition, since the elastic member is provided at the top of the optical system holder to cover the upper end of the support shaft, it prevents foreign matter from entering the bearing, improving reliability, and further improving the elasticity of the optical system holder. The space occupied by the members can be reduced, the optical system holder can be downsized, and the response performance of the optical system drive device can be improved.

If a slit is provided in the side surface of the elastic member parallel to the central axis of the elastic member, the elastic member will be easily deformed.
Also, unnecessary twisting deformation does not occur during focus control.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of an embodiment of the objective lens driving device of the present invention. FIG. 2 is an explanatory diagram of the neutral point holding rubber. FIG. 3 is an explanatory diagram of the neutral point holding mechanism when tracking drive is performed. FIG. 4 is an explanatory diagram of the neutral point holding mechanism when performing focus drive. FIG. 5 is an exploded perspective view of an example of a conventional objective lens driving device. FIG. 6 is an explanatory diagram of a neutral point holding mechanism of a conventional objective lens driving device. ■...Objective lens, 2...Objective lens holder, 3.
4... Tracking coil, 5... Focusing coil, 6... Bearing, 7... Neutral point holding rubber, 8...
...Support shaft, 8a...Teflon resin layer, 9. lO...
-Permanent magnet for tracking, 11.12 Permanent magnet for focusing, 13... Base, 14... Through hole. Figure 1 Figure 4 (b) Figure 5

Claims (2)

[Claims] (1) A support shaft, an optical system holder having a bearing rotatably and vertically slidable about the support shaft, and driving the optical system holder in the rotational direction and axial direction about the support shaft. and a neutral point holding mechanism for returning the optical system holder to a neutral position in response to this drive, wherein the neutral point holding mechanism has a hollow hole with one end open and the other end closed. The opening end of the elastic member is fixed to the optical system holder so that the central axis of the elastic member coincides with the central axis of the bearing, and the central axis of the elastic member is aligned with the central axis of the bearing. An optical system driving device characterized in that a closed end of the elastic member is fixed to an upper end of the support shaft so that the central axis of the support shaft coincides with the central axis of the support shaft. (2) The optical system driving device according to claim 1, wherein a slit is provided in a side surface of the elastic member in parallel with the central axis of the elastic member.