JPS61220141A - Device for supporting objective lens - Google Patents

Abstract

PURPOSE:To obtain an effective driving range of high sensitivity throughout a wide range by laminating a sheet-shaped elastic member and damping members to form a flat spring supporting an objective lens and providing a hollow part in the center. CONSTITUTION:An objective lens supporting member 2 is supported displacably by a pair of flat springs 4a and 4b for focusing, a relay member 5, and a pair of flat springs 6a and 6b for tracking. Each of these flat spring members is structured by laminating sheet-shaped elastic members 20 and 21 of high rigidity and a sheet-shaped damping member 22 having a high damping characteristic, and aperture parts 20a and 21a of the hollow part are formed in the center. Thus, resonance is attenuated by the damping member 22, and the effective driving range of high sensitivity is obtained throughout a wide range by elastic members 20 and 21 of high rigidity and the hollow part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an objective lens support device in which an objective lens is movably supported by an elastic support device in order to correct displacement of the objective lens with respect to a recording medium.

(Prior art) Conventionally, an objective lens that irradiates a light spot onto a recording medium is
An objective lens device supported movably in a focusing direction parallel to the optical axis and in a tracking direction perpendicular to this focusing direction is known, for example, in Japanese Patent Laid-Open No. 59
It is described in the publication No.-104733. In this known objective lens support device, a focusing leaf spring and a tracking leaf spring are provided between the objective lens support member that supports the objective lens and the base, and the elasticity of these leaf springs is used to apply force in the focusing direction. It is supported so that it can be displaced in the tracking direction. However, these leaf springs have the disadvantage that they have a high rigidity, which makes it difficult to operate them with uniform force over a wide range, making it difficult to obtain a highly sensitive dynamic range over a wide range. Ta.

Further, Japanese Patent Application Laid-Open No. 59-212807 discloses an objective lens support device in which a square hole is formed in the center of a leaf spring to increase flexibility and enable operation with a weak driving force. By forming square holes in the leaf spring in this manner, the rigidity of the leaf spring itself can be reduced, which has the advantage of providing a highly sensitive dynamic range over a wide range. However, in a leaf spring with a square hole formed in the center, the objective lens is supported by two leaf springs arranged in the same plane, so the thickness, Young's modulus, width, and length of the leaf spring are It is easily influenced by various physical property values such as, and has the disadvantage that the elastic properties as an elastic support member tend to vary. In particular, when driving the objective lens, the leaf spring may enter a micro-vibration state and resonate, and in the case of a leaf spring with a square hole in the center, the resonant frequency f0 tends to change due to fluctuations in the physical properties of the leaf spring, and therefore the driving frequency range The drawback was that the sensitivity of the Furthermore, when assembling the optical head, the method of holding the leaf spring is troublesome, and depending on the way the leaf spring is held, the leaf spring may be deformed, and the elastic properties of the leaf spring may change, making it unusable. For this reason, the best way to assemble is to use air suction to hold the leaf spring with a suction nozzle, but if you form a square hole in the center of the leaf spring, the leaf spring can be held by air suction. This not only makes assembly difficult, but also requires complicated jigs and tools.

(Objective of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks, to obtain a highly sensitive effective driving range over a wide 0 range, to prevent the resonance frequency f0 from fluctuating by 9, and to use air suction. The present invention provides an objective lens support device that can be assembled.

(Summary of the Invention) An objective lens support device according to the present invention is an objective lens support device in which an objective lens is movably supported by an elastic support device in order to correct fluctuations in the position of the objective lens with respect to a recording medium. is constructed by stacking a sheet-like elastic member and a sheet-like damping member extending in a direction perpendicular to the direction of displacement of the objective lens, and the sheet-like elastic member has a hollow portion in the extending direction. It is characterized by the fact that it has been formed.

(Embodiment) FIGS. 1 to 3 show an embodiment of an optical head equipped with an objective lens support device according to the present invention. FIG. 1 is an exploded perspective view of the main parts thereof, and FIG. The plan view and FIG. 3 are side views. An objective lens 1 for irradiating a light spot onto a recording medium such as an optical disk is fitted and attached to the support member 2. The support member 2 is displaced in a focusing direction F parallel to the optical axis of the objective lens 1 to focus a light spot on the recording medium, and is also displaced to the right of the information track on the recording medium and in a tracking direction T perpendicular to the optical axis. The objective lens support member 2 is connected to the base 3 via a support mechanism so that the light spot follows the information track. In the present invention, this support mechanism is formed by a pair of focusing leaf springs 4a.
and 4b, a relay member 5, and a pair of tracking leaf springs 6a and 6b. A pair of focusing leaf springs 4a and 4b are in the focusing direction F.
Focusing direction F while facing parallel to each other
and one end of each is installed in grooves 2a and 2b formed in the side wall of the support member 2 so as to extend in a direction perpendicular to the tracking direction T, and the other end is attached to the relay member 5.
It is installed in the upper and lower grooves 5a and 5b bored in the. Also,
A pair of tracking leaf springs 6a and 6b are connected at one end to each other so as to extend in a direction substantially perpendicular to the focusing direction F and the tracking direction T while facing each other at a certain angle α in the tracking direction T. It is attached to left and right grooves 5C and 5d formed in the member 5, and the other end is attached to grooves 7a and 8a formed in posts 7 and 8 formed integrally with the base 3. The distance between one end of the above-mentioned pair of tracking leaf springs 6a and 6b on the relay member 5 is shorter than the distance between the other ends of the posts 7 and 8, and the angle α formed by these leaf springs 6a and 6b is preferably about 30°, for example. In this way, the objective lens 1 is supported so as to be movable in the focusing direction F and the tracking direction T.

Next, a driving mechanism for driving the objective lens 1 in the focusing direction F and the tracking direction T will be explained. In the present invention, a pair of focusing coils 9a and 9b are provided on the side surface of the support member 2 facing in the tracking direction T.
A pair of tracking coils 10a and 10b are integrally attached to the outside of these focusing coils. Focusing coils 9a and 9b have a "mouth" shape when viewed in the focusing direction F, while tracking coils tOa and 10b have a "U" shape when viewed in the focusing direction F.

A magnetic field generating member that generates a magnetic field that cooperates with these focusing coils 9a, 9b and tracking coils 10a, 10b is a pair of yokes 1 made of a magnetic material.
1 and 12, and the leg portions 11a on both sides of one yoke 11.
and permanent magnets 13a and 1 installed along
3b and the legs 12& and 1 on both sides of the other yoke 120
It is composed of permanent magnets 141 and 14b mounted along the magnet 2b. These yokes 11 and 12 are fixed to pace 3 such that their central legs 11C and 12c are inserted into focusing coils 9a and 9b, respectively. Focusing coils 9a, 9b
The lead wires (only one of which is shown in FIG. 1) connected to the tracking coils 10a and 10b are connected to the terminals provided on the side surface of the support member 2 and the rear leaf springs 4a and 4b.
, 6a, 6b, pass through the hole 5e made in the relay member 5, connect to the terminal of the printed circuit board 15 fixed to the base 3, and connect from there to the circuit.

Now, when a focusing drive current having an amplitude and polarity depending on the magnitude and direction of the focusing error is passed through the focusing coils 9a and 9b, the focusing coils 9a and 9b are supported by interaction with the magnetic field passing through these coils. Member 2 and objective lens 1
receives a force in the focusing direction F, and is displaced in the focusing direction F by the deflection of the pair of focusing leaf springs 4a and 4b, so that the light beam can be focused as a minute light spot on the recording medium.

On the other hand, a tracking drive current having an amplitude and polarity depending on the magnitude and direction of the deviation of the light spot with respect to the information track is applied to the pair of tracking coils 10a and 1.
0b, the tracking coils 10a and 10b, and therefore the support member 2 and the objective lens 1, receive a force in the tracking direction T due to the interaction with the magnetic field, and the deflection of the tracking plate springs 6a and 6b causes the objective lens 1 to move in the tracking direction. It will be displaced to T.

FIG. 4 shows the configuration of an example of a focusing and tracking leaf spring according to the present invention, and FIG.
4B is a plan view, and FIG. 4B is a sectional view taken along line II' in FIG. 4A. In the present invention, a focusing or tracking leaf spring is constructed of a multilayer laminate structure in which a sheet-like elastic member with high rigidity and a sheet-like damping member with high viscosity and high damping characteristics for damping vibration are laminated. In this example, the sheet-like damping member 22 is sandwiched between the sheet-like elastic members 20 and 21. A rectangular opening 20 is formed approximately in the center of the elastic members 20 and 21! and 21a are provided, respectively. The elastic members 20 and 21 are preferably plate spring materials such as phosphor bronze with high rigidity, and the damping member 22 is preferably a rubber material such as butyl rubber or silicone rubber, or a resin such as polyester elastomer or polyurethane elastomer. A type elastic body is suitable. To attach this leaf spring to the objective lens support device, align the longitudinal direction with the direction perpendicular to the focusing direction and the tracking direction, and insert both longitudinal ends into the grooves formed in the objective lens support member and the relay member. Insert and install. If a leaf spring is constituted by a laminate structure in which a highly rigid elastic member with an opening in the center and a damping member are laminated, the rigidity of the leaf spring will be the same as that of the highly rigid elastic members 20 and 21.
, it is possible to secure a highly sensitive effective drive frequency range over a wide range, and also to effectively damp resonance, and furthermore, it is possible to appropriately select the vibration characteristics of the elastic members 20 and 21 and the damping member 22. Then, the resonant frequency f0 can be set outside the effective drive frequency range.

Next, rectangular openings 20 provided in the elastic members 20 and 21! The formation of and 21a will be explained. When forming a rectangular opening, the resonance frequency f0 must be considered in addition to the rigidity of the elastic body. That is, since this resonant frequency f0 also represents the sensitivity characteristic during driving, if the resonant frequency f0 fluctuates, a problem arises in that the sensitivity in the effective driving frequency range changes due to the leaf spring. The resonant frequency of a sheet-like elastic member is expressed by the following formula, where: E: Young's modulus of the elastic sheet m: Mass of the movable part of the elastic sheet l2 Total length of the elastic sheet b = Width of the elastic sheet From equation (1), the resonant frequency is Although f0 varies depending on the overall length, thickness, width, etc. of the elastic sheet, the thickness d of the elastic sheet is determined at the time of manufacturing the material, and the overall length l is determined by the design value of the optical head. On the other hand, elastic parts 20 and 2
The width of No. 1 can be easily changed and its management is also easy. Therefore, the width of the elastic sheet is changed so that the resonant frequency f always remains at a predetermined value. Specifically, this is managed by changing the widths of the openings 20a and 21a. The vibration characteristics of the elastic members 20 and 21 tend to change from loft to loft, and since the same lot has substantially the same characteristics, the size of the rectangular opening may be adjusted for each loft. In addition, if the openings HOa and 21& are formed by etching, they can be formed with high precision without generating any burrs around them.

FIG. 5 shows the configuration of a modified example of the leaf spring according to the present invention, FIG. 5A is a plan view, and FIG. 5B is a view of FIG.
■It is a line sectional view. In this example, one sheet-like elastic member 23 having a rectangular opening and one sheet-like damping member 24 are pasted together to form a leaf spring. In this way, even a two-layer laminate structure can effectively exhibit the rigidity and damping characteristics of a leaf spring.

FIG. 6 is a plan view showing the structure of another modification of the leaf spring according to the present invention. In this example, an example is shown in which the sheet-like elastic member 25 is provided with two openings 25& and 25b extending in the longitudinal direction thereof.

Furthermore, FIG. 7 is a perspective view showing the structure of another modification of the leaf spring according to the present invention. In this example, a three-layer structure is adopted in which a sheet-like damping member 28 is sandwiched between sheet-like elastic members 26 and 27, and each elastic member 26 and 27 is
An example is shown in which hollow portions 26a and 27a (not shown) extending in the longitudinal direction are provided in the shape of a letter.

Furthermore, FIG. 8 is a perspective view showing the structure of another modification of the leaf spring according to the present invention. In this example, four rectangular elastic members 29, 30, 31 and 32 with small widths sandwich both sides of the damping member 33 in the width direction to form a hollow portion extending in the longitudinal direction of the leaf spring. show.

FIG. 9 is a diagrammatic cross-sectional view showing a method of mounting a leaf spring according to the present invention to a lens holder supporting an objective lens.

The lens holder 40 is attached to the holder support member 41, and the holder support member 41 is fixed to the flat plate base 42. This flat plate 4
A leaf spring holding member 44 holding a leaf spring 43 to be mounted is slidably disposed on the lens holder 40 and the holder support member 41. Leaf spring holding member 44
has a suction hole 4 at a position corresponding to the center of the held leaf spring.
4a is formed, and this suction hole 44a is connected to a suction device (not shown) to suction and hold the leaf spring 43. In the leaf spring according to the present invention, a hollow portion is formed in the elastic member, but
Since the sheet-like damping member exists over the entire surface, it can be easily held using a suction holding device. While holding the leaf spring 43 under suction, slide the leaf spring holding member 44 in the directions of arrows a and b to remove the side end 438 of the leaf spring 43.
is inserted into the groove 40a formed in the lens holder 40. In this case, the width of the groove 408 is formed to be slightly larger than the thickness of the plate spring 43, and an adhesive is interposed between the groove 40a and the side end 43a of the plate spring to fix the groove 408. By holding the leaf spring under suction and attaching it to the lens holder in this manner, the attachment can be easily carried out without causing deformation of the elastic member. Furthermore, the plate spring can be attached to the lens holder by simply attaching the plate spring and the lens holder 40 to their respective support members, which is convenient for automating the assembly of the optical head. Note that when attaching the other end of the leaf spring to the relay member, it is similarly attached while being held under suction.

(Effects of the Invention) As explained above, according to the present invention, the leaf spring that displaceably supports the objective lens is laminated with a sheet-like elastic member having high rigidity and a sheet-like damping member, and the elastic member has a middle part. Since the structure includes a cutout, a highly sensitive effective drive frequency range can be ensured over a wide range, and the generation of resonance vibration can be effectively prevented.

In addition, the action of the sheet-like damping member can suppress fluctuations in the resonance frequency f0, making it possible to provide an objective lens support device with little change in sensitivity.

Furthermore, since the sheet-like elastic member with the hollow part formed thereon is bonded to the sheet-like damping member to form a leaf spring without the hollow part, the leaf spring can be held by an air suction device, and the elastic properties of the leaf spring can be improved. The leaf spring can be attached to the objective lens support member without damaging the structure.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the structure of an example of an optical head equipped with an objective lens support device according to the present invention, and FIGS.
4A and 4B are plan views and sectional views showing the configuration of an example of a leaf spring according to the present invention, and FIGS. 5A and B are a modified example of the leaf spring according to the present invention. 6, 7, and 8 are plan views and perspective views showing the structure of another modification of the leaf spring according to the present invention. FIG. 9 is an objective lens according to the present invention. FIG. 3 is a diagrammatic cross-sectional view showing the state of the support device when it is assembled. ■...Objective lens 2...Objective lens support member 3...Base 4a, 4b...Focusing plate spring 5...Relay member 6a, 6b...Tracking plate spring 7.8...・
Posts 9a, 9b...Focusing coil 10a,
lob...Tracking coils 13a, 13b
, 14a, 14b...Permanent magnets 20, 21.23
．． 25.26.27.29.30.31.32-- Sheet elastic member 22, 24.28... Sheet-like damping ms material 40
... Lens holder 41 ... Holder support member 4
2... Flat plate stand 43... Leaf spring 44...
- Leaf spring holding member. Figure 2 Figure 3 Figure 4 Procedure Amendment Written on May 17, 1985 Manabu Shiga, Director General of the Patent Office1, Indication of the incident Patent Application No. 60349 of 19852, Name of the invention Objective lens support device 3. Relationship with the case of the person making the amendment Patent applicant (03?) Olympus Optical Industry Co., Ltd. 4. Column "Explanation of agent" and drawing L #1ms between line t41O and line 11 from the bottom of page 11 Insert "d: Thickness of elastic sheet". λ, page 17, line 4, "22, 24.28... sheet-like damping member" is corrected to "2ZA4.28.88... sheet-like damping member". 3. Correct Figure 1 of the drawing as shown in the attached sheet.

Claims (1)

[Claims] 1. In an objective lens support device in which the objective lens is movably supported by an elastic support device in order to correct fluctuations in the position of the objective lens with respect to the recording medium, the elastic support device includes:
The sheet-like elastic member and the sheet-like damping member are laminated to extend in a direction perpendicular to the direction of displacement of the objective lens, and a hollow portion is formed in the sheet-like elastic member in the extending direction. An objective lens support device characterized by: