JPS63140431A - Spring supporting structure for objective lens driving device - Google Patents

Abstract

PURPOSE:To fix tightly a tracking spring and a focus spring with thin adhesives and to improve stability in a servo system by dividing some of a lens supporting member, an intermediate supporting body and a fixed supporting body with the fitting part of a tracking spring and a focus spring as a part of a boundary. CONSTITUTION:An objective lens lens-barrel 11 is divided into an inside part 11a and an outside part 11b with the fitting part of a tracking direction moving parallel spring 12 as a boundary, and to the part, the upper edge part of a tracking spring is respectively bonded. In this case, while the inside part 11a and the outside part 11b are divided, respective parts can be processed independently, and therefore, they can be processed to an arbitrary thickness in accordance with the thickness of the tracking spring 12. Thus, the thickness of the adhesives to bond the tracking spring 12 can be made very thin, the spring constant of the adhesives can be much larger than the spring constant in the focus direction of the tracking spring 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an objective of a so-called optical disk device that optically records, reproduces, erases, etc. information by irradiating a recording medium with a light beam such as a laser. The present invention relates to a lens drive device, and particularly to a spring support structure that supports an objective lens in a floating manner.

Prior Art First, the structure of a conventional objective lens driving device, which is the background of the present invention, will be explained with reference to FIGS. 3 to 6.

FIG. 6 is a schematic diagram of a magneto-optical disk device, in which a magneto-optical disk 6 is rotationally driven by a motor 9, and a laser beam 4 emitted from a laser light source 3 is reflected by a mirror 5.
The light passes through the objective lens 2 and converges onto the surface of a disk recording medium 6° built into a magneto-optical disk 6, where information is reproduced and written.

1 drives the objective lens 2 vertically and horizontally to adjust the convergence position of the laser beam to the disk recording medium 6. An objective lens driving device is used to perform follow-up control on the recording track, 7 is an optical heald housing the above-mentioned optical system, and 8 is a coil for recording and erasing.

The above-mentioned objective lens drive device moves the objective lens 2 in a direction perpendicular to the surface of the recording medium 61 of the magneto-optical disk 6 (in the focus direction) using a focus drive means (to be described later), or by a magneto-optical drive means (to be described later). The disk recording medium 6. is moved in the radial direction (tracking direction) of the disk 6. This system displaces the objective lens 2 in accordance with the surface wobbling of the disk and the eccentric rotation of the disk, and continuously and precisely focuses the laser beam on the information trunk.The conventional general structure is shown in Figs. 3 and 4. has been done.

That is, the conventional objective lens drive device 1 includes an objective lens barrel 11 (lens support member) that houses and supports the objective lens 2.
is movable in the optical axis direction of the objective lens 2,
This objective lens barrel 11 is attached to an intermediate support 13 by a pair of tracking direction movable springs 12, 12 (tracking springs) which are movable only in the tracking direction.

Therefore, the objective lens 2 is supported so as to be swingable in the tracking direction.

A rubber-like elastic body 14 is bonded to the inside of the parallel spring 12 movable in the tracking direction to damp vibrations of the spring. Reference numeral 15 denotes a tubular counterbalance weight fitted around the lower portion of the outer periphery of the objective lens barrel 11.

On the other hand, the fixed support body 17 constituting the outer shell of the objective lens driving device 1 is formed into a hollow cylindrical shape, and the tracking magnetic circuit 16 fixed to the inside thereof is, as shown in FIG.
It is composed of a tracking yoke 18 and a tracking magnet 19, and a tracking magnetic gap 20 is formed between them.

In this tracking magnetic air gap 20, this air 8i2
A tracking drive coil 21 whose one end is fixed to the objective lens barrel 11 is inserted so as to cross 0. The above-described tracking magnetic circuit 16 and tracking drive coil 21 are provided as a set symmetrically with the optical axis of the objective lens 2 interposed therebetween.

Therefore, when the input current to the tracking drive coil 21 is changed, an external force acts on the tracking drive coil 21 due to electromagnetic action, displacing the objective lens barrel 11 and the objective lens 2 supported by it in the tracking direction. .

The tracking drive means is configured with the above configuration.

Next, the focus driving means will be explained.

A focusing magnetic circuit 23, which is a component of the focus driving means, includes a focusing yoke 24, a focusing permanent magnet 25. and a focusing yoke plate 26, which form a closed magnetic path. The focusing magnetic circuit 23 is attached to the fixed support 17 by fitting and fixing the focusing yoke 24 into the lower part of the inner wall of the fixed support 17.

A focusing magnetic gap 27 is provided between the focusing yoke plate 26 and the focusing yoke 24. A focusing magnetic gap 27 is provided between the focusing yoke plate 26 and the focusing yoke 24. A drive coil 28 is arranged. This focus drive coil 28 and the focus magnetic circuit 23° form a focus drive section.

The intermediate support 13 is swung only in the focus direction by a pair of upper and lower focus direction movable springs 29 (focus springs), which have -m fixed to the intermediate support 13 and the other end fixed to the fixed support 17. It is movable. Furthermore, a rubber-like elastic body 30 is bonded to one side of the focus direction movable spring 29 to damp vibrations of the spring.

In the above configuration, when a focus control current is passed through the focus drive coil 28, the focus drive coil 28. Focus movable part 31 consisting of intermediate support 13 and tracking direction movable parallel spring 12
The objective lens barrel 11 and the objective lens 2 supported by
The trunking movable part 22, which is made up of the following, is displaced only in the focus direction.

The focus drive means is configured with the above configuration.

Conventionally, the tracking direction movable parallel spring 12 in the objective lens drive device 1 configured as described above has one end glued to a parallel hole 32 formed in the objective lens barrel 11 in the optical axis direction, as shown in FIG. The other end is fixed through a parallel hole 34 in the optical axis direction formed in the intermediate support 13.
It was fixed to with an adhesive 35. FIG. 5 is an enlarged view of the parallel hole 32.

Further, the outer peripheral end of the focus direction movable spring 29.29 is
It is fixed via an adhesive 37 to an annular hole 36 perpendicular to the optical axis formed on the inner surface of the fixed support 17, and the inner peripheral end thereof is
It is fixed through an adhesive 39 to an annular hole 38 formed in the intermediate support 13 and perpendicular to the optical axis.

Problems with the Prior Art However, in the case of the objective lens driving device 1 using the parallel springs 12 movable in the trafking direction and the movable springs 29 in the focusing direction, which are shaped like leaf springs, as described above, when each leaf spring is bent, the flexure Resonance occurs when a force is applied in a direction perpendicular to the direction.

For example, if we consider the movement model in the focus direction using the structure shown in FIG. 3 as an example, the vibration will be a two-degree-of-freedom system as shown in FIG. resonance (−order resonance), and resonance in the focus direction of the trunking direction movable parallel spring 12 that is movable in the tracking direction (secondary resonance).
occurs.

However, here, ml + m2 is the mass of the movable part consisting of the leaf spring 29.12 in the focus direction and the tracking direction, respectively, and k is the spring constant in the focus direction of the focus movable spring 29 movable in the focus direction. k2
is the spring constant in the focus direction of the tracking direction movable parallel spring 12 that is movable in the tracking direction, cl and c2 are the viscosity coefficients of the respective spring systems, Xl+X2 are the focus direction and the displacement in the focus direction of the movable part in the tracking direction, respectively. f is a force in the focus direction that is applied to the movable part in the focus direction.

At this time, the frequency fr2 of the secondary resonance is expressed as follows.

The spring constant 2 in equation +11 means that the parallel spring 12 movable in the tracking direction is actually connected to the objective lens barrel 11 at one end with an adhesive 33 and to the intermediate support 13 at the other end with an adhesive 35. 7 (1) ), these springs can be considered as a model connected in series.

At this time, the overall spring constant is 2, which is k2-ko1 redundant.
...(2) It is expressed as kh+ku, and at the time of )C2b-flash, it becomes k2-k2m.

That is, it is sufficiently thick for k2 to 2 m (if this is not possible, the overall spring constant will be reduced by the adhesive).

As in the conventional apparatus shown in FIG. 3, the objective lens barrel 11. Intermediate support 13. Parallel holes 32, 34, respectively formed in the fixed support 17. With a structure such as the annular holes 38 and 36, the width of each hole cannot be precisely machined, and the width of a certain hole becomes wide, resulting in an increase in the thickness of the adhesive layer.

Therefore, 2k cannot be increased, and the overall spring constant will decrease by 2.

Further, depending on the type of adhesive, the temperature may affect the adhesive 2 to a large extent, resulting in a phenomenon in which the frequency fr2 of the secondary resonance varies greatly depending on the temperature.

These phenomena cause instability in the servo system, so it is necessary to make the spring constant of the adhesive as thick as possible (2+) to suppress their influence.

For this purpose, it is necessary to provide a structure that allows the thickness of the adhesive to be made as small as possible.

In the above description, the bonding of the parallel spring 12 movable in the tracking direction has been described, but the same problem exists in bonding the parallel spring movable in the focus direction.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a spring support structure for an objective lens drive device in which a tracking spring and a focus spring can be fixed with a thin adhesive.

Structure of the Invention In order to achieve the above object, the main means adopted by the present invention is to replace the lens support member that supports the objective lens whose optical axis is perpendicular to the disk recording surface with a tracking spring that is movable only in the disk radial direction. The lens support member is supported by an intermediate support via a lens support member, and the intermediate support is supported by a fixed support via a focus spring that is movable only in a direction perpendicular to the disk recording surface, and the lens support member is connected to the fixed support. A tracking drive section interposed between the lens support members drives the disk in the radial direction, and a focus drive section interposed between the fixed support body and the intermediate support moves the intermediate support body in a direction perpendicular to the recording surface of the disk. In the objective lens driving device, any or some of the lens support member, intermediate support, and fixed support is divided with the attachment part of the tracking spring or the focus spring as part of the boundary. This is a spring support structure for an objective lens drive device.

Effect: With the structure described above, the adhesive that attaches the parallel spring in the trunking direction and/or the movable spring in the focus direction
Since iFI- can be attached to the minimum necessary level, it is possible to prevent a decrease in the spring constant due to the adhesive layer, and also to suppress fluctuations in the resonance frequency due to temperature, thereby increasing the stability of the servo system.

Next, an embodiment embodying the present invention will be described with reference to FIGS. 1 and 2 to provide an understanding of the present invention.

The second figure is a side sectional view of the entire objective lens driving device having a spring support structure according to an embodiment of the present invention, and FIG.
1 and (bl are main part sectional views showing a specific example of a spring support structure for the objective lens barrel in the same embodiment.

Note that the following example is only one specific example of the present invention, and is not intended to limit the technical scope of the present invention.

Also, Figures 3 to 51! The same reference numerals are used for elements common to the conventional device shown in FIG.

In the objective lens driving device+ shown in FIG.
The differences from the conventional device shown in FIGS. and FIG. 4 are as follows.

The objective lens barrel 11 that supports the objective lens 2 has an inner portion 11. The mounting of the tracking direction movable parallel spring 12 is divided into the outer portion 11b and the outer portion 11b, and the upper end portions of the tracking direction movable parallel springs 12 and 12 are bonded to the divided portions, respectively.

In this case, the contact portion between the tracking direction movable parallel spring 12 and the inner portion 11m and the outer portion 11 of the objective lens barrel 11 is the inner portion 11. Since the outer portion 11F and the outer portion 11F can be processed independently in a divided state, they can be processed to any thickness depending on the thickness of the tracking direction movable parallel spring 12. Therefore, the tracking direction movable parallel spring 12 to the inner part 11. And the thickness of the adhesive for adhering to the outer portion 11 can be made extremely thin. Therefore, the spring constant of this adhesive can be made much larger than the spring constant of the tracking direction movable parallel spring 12 in the focus direction.

The lower end of the tracking direction movable parallel spring 12 has an inner portion 13.similar to the upper end. and an outer portion 13h, which are connected to and bonded to a divided portion of the intermediate support 13. In this case, as before, the inner portion 13. and outer portion 131. Since the processing dimensions of the abutting portion between the movable parallel spring 12 and the tracking direction movable spring 12 can be arbitrarily selected, the layer of adhesive filling this abutting portion can be made extremely thin.

Next, the support structure for the focus direction movable spring 29 will be explained.

The fixed support body 17 that supports the focus direction movable spring 29 at its outer circumferential portion supports the focus direction movable spring 2
9 is attached to the upper part 171 and the lower part 1.
7I, and the outer circumferential end of the focus direction movable spring 29 is fixed to this divided portion via a presser ring 291 with an adhesive (not shown).

The inner peripheral end of the focus direction movable spring 29 is sandwiched between the outer peripheral protrusion 13c of the intermediate support 13 and a presser ring 29 that abuts the outer peripheral protrusion 13c via the inner peripheral end of the focus direction movable spring 29. and is fixed to the intermediate support 13 with an adhesive.

Various structures are conceivable as a structure in which the tracking direction movable parallel spring 12 and the focus direction movable spring 29 as described above are supported by separate supports via an adhesive.

For example, Figure 2! What is shown in a+ is an example of how the tracking direction movable parallel spring 120 is attached to the objective lens barrel 11, but in this case, the end of the tracking direction movable parallel spring 12 is exposed to the outside of the objective lens barrel 11. The end of the parallel spring 12 movable in the tracking direction is inserted into the objective lens barrel 11 so that the tracking direction movable parallel spring 12 is inserted into the objective lens barrel 11.

On the other hand, the structure shown in FIG. 2) is similar to that shown in FIG. This is an example of a case where the end of the parallel spring 12 movable in the tracking direction comes into contact with this contact llc, thereby making the positioning accurate.

Effects of the Invention As described above, the present invention provides a lens support member that supports an objective lens whose optical axis is perpendicular to the disk recording surface.
The lens is supported by an intermediate support via a tracking spring that is movable only in the radial direction of the disk, and the intermediate support is supported by a fixed support via a focus spring that is movable only in a direction perpendicular to the recording surface of the disk. The support member is driven in the disk radial direction by a tracking drive unit interposed between the fixed support member and the lens support member, and the intermediate support member is driven by a focus drive unit interposed between the fixed support member and the intermediate support member. In the objective lens drive device configured to drive in a direction perpendicular to the disk recording surface, any or some of the lens support member, intermediate support, and fixed support may be attached with a tracking spring or a focus spring. Since the spring support structure of the objective lens driving device is characterized by dividing the area into parts as part of the boundary, the dimensional accuracy and machining accuracy of the holes for attaching the tracking spring and focus spring are improved, so the dimensions can be reduced. The dimensions of each spring can be matched, thereby making it possible to make the layer of adhesive as thin as possible, improving the spring constant of the adhesive and obtaining a stable servo system. Furthermore, by minimizing the thickness of the adhesive layer, the strength of the adhesive can be maximized.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of the entire objective lens drive device having a spring support structure according to an embodiment of the present invention, and FIG. FIG. 3 is a view corresponding to FIG. 1 regarding a conventional objective lens driving device, FIG. 4 is a sectional view taken along the line A-A in FIG. 3, and FIG. 5 is a conventional device. FIG. 6 is a cross-sectional view of the attachment of the parallel spring movable in the tracking direction to the objective lens barrel; FIG. Figure 7 (al is an explanatory diagram for explaining the movement model in the focus direction, No. 7FXJ) is an explanatory diagram for explaining the spring effect of the adhesive. (Explanation of symbols) 11...Objective lens drive Device 61...Disc 2...Objective lens 11.
...Objective lens m cylinder (lens support member) 111...Inner part 11+,...Outer part 12...Tracking direction movable parallel spring (tracking spring) 13...Intermediate support body 131...Inner part 13...outer part 17
... fixed support body 17, ... upper part 17h ... lower part 29
... Focus direction movable spring (focus spring) 29a, 29b... Presser ring.

Claims (1)

[Claims] A lens support member supporting an objective lens whose optical axis is perpendicular to the disk recording surface is supported by an intermediate support via a tracking spring movable only in the disk radial direction, and the intermediate support the lens support member is supported by a fixed support via a focus spring movable only in a direction perpendicular to the disk recording surface, and the lens support member is controlled to adjust the disk radius by a tracking drive unit interposed between the fixed support and the lens support member. In the objective lens driving device, the intermediate support is driven in a direction perpendicular to the disk recording surface by a focus drive section interposed between the fixed support and the intermediate support. 1. A spring support structure for an objective lens driving device, characterized in that one or more of the member, intermediate support, and fixed support is divided with the mounting portion of a tracking spring or a focus spring as part of the boundary.