JP2793582B2 - Objective lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device for recording and reproducing information on an optical recording medium. 2. Description of the Related Art A high-density recording / reproducing apparatus using a laser beam, which has been put into practical use in recent years, generally has a sound recorded in a spiral or concentric fine groove on a rotating recording disk with irregularities. Information such as images and images is read using the diffraction phenomenon of laser light, which is coherent light controlled to focus on the groove. Alternatively, information to be recorded is formed on the groove by the energy of laser light. In an apparatus similar to this, it is one of the important techniques to accurately focus a laser beam on a fine groove. In particular, when an external storage device such as a computer is used for high-speed recording and high-speed reproduction of a large amount of information such as image information, it is necessary to minimize recording and reproduction errors of the information. For that purpose, accurate and stable two-dimensional control in a wide frequency band of the objective lens is required. [0003] Also, searching for recorded information quickly is an important technical problem in performing high-speed computer information processing. This high-speed retrieval of information on a recording medium requires that the position control of the objective lens be quickly switched from one groove to another distant groove. At this time, the objective lens needs to be rapidly accelerated and stopped, and at the time of acceleration, a large kinetic energy is mechanically given. This becomes an obstacle when the position control once released is quickly returned to the control state in the target groove. FIGS. 6 (a) and 6 (b) show an example of an objective lens driving device currently in practical use. The objective lens 1, the focus driving coil 5, the radial driving coil 6, and the holding cylinder 12 are supported on the fixed part 11 by four parallel metal wires 7 as elastic supporting members. The metal wire 7, which is an elastic member, also serves as a coil lead wire and a support spring. The metal wire 7 is covered with a rubber tube 22 so as to add a damping effect. In such a structure, the damping effect when the metal wire 7 is displaced from the neutral position as shown in FIG. 6A to FIG. 6B is generated in the rubber tube 22 with the bending deformation of the metal wire 7. Of bending moment having the same shape as the metal wire 7 to be bent 1
8 depends on the energy consumed in each part.
However, since the curvature of the bending deformation of the metal wire 7 is very small, the deformation of each part of the rubber tube 22 deformed accordingly is also very small, the damping effect is not sufficient, the mass of the support member is increased, and the entire support mechanism is increased. Only increases the spring constant of. In the case where a leaf spring is used as the elastic support member instead of the metal wire 7, a structure in which a damping sheet in which rubber is coated in a plate shape on the surface of the leaf spring is provided.
When the leaf spring is bent, a damping force is generated by the shear deformation of the damping sheet. [0007] Even when a leaf spring is used as described above, the damping sheet is not effectively deformed because the leaf spring is slightly deformed, and sufficient damping cannot be obtained. Further, it is difficult to attach the above-described damping sheet uniformly to a small leaf spring in manufacturing. Further, when a rubber-based damping sheet is generally used, a material having good temperature characteristics, such as silicon rubber, has a small damping effect, while butyl rubber, etc. has a large damping effect. Rates also vary greatly. Therefore, since the objective lens driving device having such a structure cannot sufficiently absorb the large kinetic energy received at the time of high-speed search, high-speed control is difficult, and depending on the environment, the state of the control system changes, and information reading error occurs. Is likely to occur. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and makes it possible to attenuate kinetic energy applied to a movable portion including an objective lens at an appropriate speed. It is an object to provide an objective lens driving device. In order to achieve the above object, according to the present invention, there is provided an objective lens, a movable portion on which the objective lens is mounted, and a plurality of elastic members which elastically support the movable portion with respect to a fixed portion. A leaf spring, driving means for drivingly displacing the movable portion with respect to the fixed portion at least in the optical axis direction of the objective lens, a leaf spring insertion portion through which the leaf spring is inserted, and An objective lens drive including an intermediate member that keeps the gap length in the moving direction of the leaf spring substantially constant together with the leaf spring insertion portion, and a viscous body filled in a space defined by the leaf spring insertion portion and the intermediate member. The device. According to the present invention having such a configuration,
An intermediate member that forms a part of the fixed portion is interposed between the plurality of leaf springs, so that the leaf spring efficiently deforms the viscous body around the plate spring in response to deformation within its moving range. Let it increase the damping effect. That is, the intermediate member regulates the gap length in the moving direction of the leaf spring to be substantially constant. Therefore, according to the structure of the present invention, when the objective lens is driven in the direction of the optical axis (focus direction), the leaf spring is deformed as if stirring the viscous body.
This means that the viscous material is always stirred in the direction of the degree of freedom given by the leaf spring, and a large damping effect can be expected. By the above operation, the large kinetic energy received at the time of high-speed retrieval of information on the recording medium can be absorbed at an appropriate speed, and the control state can be quickly brought into control. Further, even if the objective lens vibrates largely in the direction of the optical axis due to disturbance or the like acting on the apparatus, excessive vibration may occur due to the leaf spring contacting the intermediate member. Can be suppressed. That is, the risk that the objective lens collides with the disk or the like is avoided because the intermediate member functions as a kind of stopper. Also, an objective lens, a movable part on which the objective lens is mounted, a plurality of support members for elastically supporting the movable part with respect to a fixed part, and at least the objective lens for moving the movable part with respect to a fixed part Driving means for driving and displacing in the optical axis direction, a support member insertion portion for commonly inserting the support members which are arranged in parallel in the optical axis direction of the objective lens, and filling the support member insertion portion. It is also possible to provide an objective lens driving device having a viscous body. Hereinafter, a reference example and an example of an objective lens driving device according to the present invention will be described with reference to the drawings. 1 and 2 are a perspective view and a sectional view, respectively, of a reference example of an objective lens driving device according to the present invention. The objective lens 1 and the holding cylinder 12 for the objective lens 1
And a movable part 13 including a focus drive coil 5 and a radial drive coil 6 for applying a driving force to the holding cylinder 12.
Are supported by a metal wire 7, which is four elastic support members and also serves as a lead wire of the coil, via a fixed portion 11 and a positioning member 10. The metal wire 7 as the four elastic support members is
The periphery is partially covered with a viscous body 8, and the periphery is covered with a cylindrical covering member (support member insertion portion) 9 of a relatively rigid material fixed to the fixing portion 11. The covering member 9 is provided such that its opening is along the holding cylinder 12 side, that is, along the surface including the optical axis direction of the objective lens 1. Viscous body 8
Is a viscosity that does not flow out of the opening of the covering member 9 and does not significantly increase the spring constant of the entire support mechanism. The movable section 13 can be displaced by adjusting a magnetic flux generated by a magnetic circuit composed of the permanent magnet 2, the yoke 3 and the center pole 4 and a current flowing through the drive coils 5 and 6 of the movable section 13. The movable part 13 is shown in FIG.
When the metal wire 7 is displaced from the neutral position shown in FIG. 2A as shown in FIG. 2B, a part of the metal wire 7 serving as the elastic support member is generated in the viscous body 8. Then, when the objective lens 1 is driven in the direction of its optical axis (focus direction) and in the direction perpendicular to it (radial direction), the metal wire 7 is deformed as if stirring the viscous body 8. This means that the viscous material 8 must be
Means that a stir operation occurs. The pressure distribution 17 which the metal wire 7 receives from the surrounding viscous body 8 has a phase lag with respect to the dynamic displacement of the metal wire 7 and has a great effect on energy dissipation.
Further, since the viscous body 8 has an adhesive property even in a high frequency region where deformation is relatively small, the viscous body 8 is in close contact with the metal wire 7 and sufficiently absorbs partial resonance and the like. The driving characteristics of such an objective lens driving device are as follows.
9 shows the transfer characteristics of a simple second-order lag system with moderately effective attenuation. This facilitates the design of the objective lens driving device when it is used as one element of a control system of the entire recording / reproducing device. Next, an embodiment of the present invention will be described with reference to FIGS. In the drawings, the same or corresponding portions as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the leaf spring 1 is attached to the elastic support member.
4, the movable portion 13 is attached to two parallel leaf springs 14a for focusing, and is the same as the surface including the optical axis of the objective lens 1 bonded to the leaf springs 14a for focusing. One radial leaf spring 14b having a surface
Is fixedly supported by being sandwiched by the fixing portion 11. The support system by the leaf springs 14 is covered by the two covering members 9 and the fixed portion 11 arranged at the upper and lower portions, except for the portion facing the movable portion 13 near the fixed portion 11. . These gaps are filled with a viscous body 8. That is, in this embodiment, the support member insertion portion is formed by the two covering members 9 and the fixing portion 11. Also in the case of this embodiment, the covering member 9 is provided such that its opening is along the holding cylinder 12 side, that is, the surface including the optical axis direction of the objective lens 1. An intermediate member 19, which is a part of the fixed portion 11, is interposed between the two leaf springs 14a for focusing. Is used for efficiently deforming the surrounding viscous body 8 to enhance the damping effect. That is, the intermediate member 19 and the covering member 9 define the focus leaf spring 14a so that the gap length in the moving direction is kept substantially constant. Also in this embodiment, when the objective lens 1 is driven in the optical axis direction (focus direction), the focus leaf spring 14a is deformed like stirring the viscous body 8. This is the leaf spring 14a for focusing.
This means that the stirring operation of the viscous body 8 always occurs in the direction of the degree of freedom given by. FIG. 4 shows a case where the movable part 13 is displaced in the focusing direction. The reaction force received by the deformed focusing leaf spring 14a from the viscous body 8 around the movable part 13 is like a damping pressure distribution 20. Become. FIG. 5 shows a case where the movable portion 13 is displaced in the radial direction. At this time, the reactive force received by the deformed radial leaf spring 14a from the surrounding viscous body 8 is as follows.
It becomes like a damping line shear force distribution 21. These reaction forces have a phase lag with respect to the dynamic displacement of the leaf spring 14, and have a great effect on dissipation of kinetic energy. Further, the viscous body 8 around the leaf spring 14 has an adhesive property even in a high frequency region where the deformation is relatively small, so that the viscous body 8 is in close contact with the leaf spring 14 and sufficiently absorbs partial resonance. In the case of this embodiment, since the substantial opening of the covering member 9 is made sufficiently small by the intermediate member 19, the viscous body 8 is prevented from flowing out from this opening.
This makes it possible to maintain the damping effect over a long period of time. Further, even if the objective lens 1 vibrates largely in the optical axis direction due to a disturbance or the like acting on the device, an excessive amount is generated by the contact of the focusing leaf spring 14 a with the intermediate member 19. Vibration can be suppressed. That is, since the intermediate member 19 serves as a kind of stopper, the risk of the objective lens 1 colliding with a disk or the like is avoided. Further, two focus leaf springs 14a are provided.
Are commonly inserted into a space formed by the covering member 9 and the intermediate member 19. By arranging a plurality of elastic support members arranged in parallel in the optical axis direction in one space in this manner, even if the filling amount of the viscous material or the like varies at the time of manufacturing, the elastic support members have uniform uniformity. Since the damping force acts, the inclination of the optical axis of the objective lens 1 can be suppressed as much as possible. In the case of a metal wire and a leaf spring,
The closer to the movable part than the vicinity of the fixed part, the greater the deformation of the surrounding viscous body and the greater the damping effect. It is determined by The present invention is not limited to the above embodiment, and the supporting member may be any elastic member other than the metal wire and the leaf spring. Further, the driving means of the movable section is not limited to the moving coil method, but may be a driving method such as a moving magnet method. As described above, according to the present invention, an intermediate member which is disposed between a plurality of leaf springs and maintains the gap length in the moving direction of the leaf spring together with the leaf spring insertion portion is provided. Therefore, when the objective lens is driven and displaced in the optical axis direction, the viscous body is surely stirred, and a large damping effect can be expected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a reference example of an objective lens driving device according to the present invention. FIG. 2 is a sectional view showing a reference example of the objective lens driving device of the present invention. FIG. 3 is a perspective view showing an embodiment of the objective lens driving device of the present invention. FIG. 4 is a sectional view showing an embodiment of the objective lens driving device of the present invention. FIG. 5 is a sectional view showing an embodiment of the objective lens driving device of the present invention. FIG. 6 is a sectional view showing a conventional objective lens driving device. [Description of Signs] 1 Objective lens 2 Permanent magnet 5 Focusing drive coil 6 Radial drive coil 7 Metal wire (supporting member) 8 Viscous body 9 Covering member 11 Fixed part 12 Holding cylinder 13 Movable part 14a, 14b Leaf spring (supported) Member) 19 Intermediate member

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akira Matsuura 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute Co., Ltd. (56) References JP-A-61-258346 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/09

Claims (1)

(57) [Claims] An objective lens, a movable part on which the objective lens is mounted, a plurality of leaf springs elastically supporting the movable part with respect to a fixed part, and the movable part with respect to the fixed part at least in the optical axis direction of the objective lens Driving means for driving displacement, a leaf spring insertion portion for passing the leaf spring, and an intermediate member disposed between the leaf springs and maintaining a gap length in the moving direction of the leaf spring together with the leaf spring insertion portion substantially constant; An objective lens driving device comprising: a viscous body filled in a space defined by the leaf spring insertion portion and the intermediate member.