WO2001013368A1

WO2001013368A1 - Device for driving object lens

Info

Publication number: WO2001013368A1
Application number: PCT/JP1999/004423
Authority: WO
Inventors: Yoshio Akeda
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 1998-02-18
Filing date: 1999-08-17
Publication date: 2001-02-22
Also published as: JP3757603B2; CN1323437A; CN1154988C; JPH11232671A

Abstract

A device for driving an object lens that optically reads information recorded on a rotating disk. A lens holder (2) is held on an intermediate holder (71) by means of four first metal wires (61), and the intermediate holder (71) is held on a fixed part (72) by means of four second metal wires (62). The sensitivity to the acceleration acting on the lens holder (2) increases in the different frequency bands of disk rotation corresponding to the different resonance frequency bands associated, respectively, with the first free vibration system composed chiefly of the first metal wires (61) and the second free vibration system composed chiefly of the second metal wires (62). Thus, the sensitivity of an optical tracking spot to displacements of the information tracks increases in at least two frequency bands of disk rotation.

Description

Objective lens drive

Technical field

The present invention provides an objective lens for optically reading information recorded on a rotationally driven disk-shaped recording medium, in a focusing direction parallel to the optical axis of the objective lens and a tracking direction perpendicular to the optical axis. The present invention relates to an objective lens driving device for driving the lens.

Akira Background technology

For example, four metal wires are used as one supporting means of an objective lens holding member in an objective lens driving device used in an information reproducing device that optically reads information recorded on a rotationally driven disk-shaped recording medium. There is a cantilever support method in which one end of each is fixed to the objective lens holding member and the other end is fixed to a fixing portion. In this cantilever support method, the primary resonance frequency of the objective lens driving device is determined by the mass of the movable body including the objective lens holding member and the spring constant of the metal wire.

In this primary resonance frequency band, the drive sensitivity to the current applied to the objective lens driving device is significantly increased, and therefore the design should be performed so that the primary resonance frequency band substantially matches the rotation frequency band of the recording medium. Accordingly, the light spot generated by the objective lens fixed to the objective lens holding member generates an acceleration required for following the displacement of the information recording track in the focusing direction and the trunking direction due to the rotation of the recording medium. As a result, the focusing and tracking servo required for reading the optical information of the information reproducing apparatus can be secured.

In recent years, in CD-ROM playback devices, data transfer speeds such as 4x, 8x, and 16x have been promoted compared to the standard transfer speed of recorded information conventionally used for music program playback, etc. , _u speed of such data transfer became so that the mainstream of the CD- ROM playback device market is an information recording medium disc The acceleration sensitivity required for the light spot generated by the objective lens to accurately follow the displacement of the information track on the disk at such a rotation speed is achieved. However, there is a demand for an optical lens drive for optical lenses that reads information.

In order to satisfy this requirement, in the conventional objective lens driving device, the primary resonance frequency is increased in accordance with the increase in the rotation speed of the disk, and the maximum displacement of the information recording track in the focusing and tracking directions occurs. The design was made so that the maximum level of acceleration sensitivity could be obtained in the rotational frequency band.

However, in the conventional objective lens driving device, the objective lens driving device has the following resonance frequency in accordance with an increase in the rotation speed of the disk for the purpose of speeding up data transfer. In the rotational frequency band of the disk, the acceleration sensitivity for the optical spot generated by the objective lens to follow the displacement of the information recording track is reduced, and the standard of the CD-ROM reproducing device is reduced. There is a problem in that the operation performance at the standard transfer speed of data applied to music playback, which is a function, is hindered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the conventional objective lens driving device, and has a capability of following the displacement of the information recording track of the optical spot in at least two disk rotation frequency bands. The objective is to provide an objective lens drive that can increase the sensitivity. Disclosure of the invention

An objective lens driving device according to the present invention includes an objective lens holding device, a forcing force coil for generating a driving force in a forcing direction parallel to an optical axis of the objective lens, and a light source for the objective lens. An objective lens holding member around which a tracking coil that generates a driving force in a tracking direction perpendicular to the axis is wound, and four ends having one end fixed to the objective lens holding member and the other end fixed to a relay holding member A first metal wire, four second metal wires having one end fixed to the relay holding member, and the other end fixed to a fixing portion; the second metal wire and the second metal wire Through before A magnetic circuit member disposed on the fixed portion so as to form a magnetic field for generating a driving force by Lorentz force by supplying a current to the focusing coil and the tracking coil; The objective lens holding member is movably supported by the relay holding member by the elastic deformation of the first metal wire, and the relay holding member is movably supported by the fixing portion by the elastic deformation of the second metal wire. I have supported it. Thus, the first mass of the first metal wire and the total mass of members such as the objective lens holding member movably supported by the elastic deformation of the first metal wire and the spring constant of the four first metal wires are determined. The relay holding member is held on the fixed portion by the free vibration system and the four second metal wires, and the objective lens holding member and the relay are movably supported by the elastic deformation of the second metal wire. And two free vibration systems based on the total mass of the members such as the members and the spring constants of the four second metal wires. The masses of these constituent members and the gold厲 By optimizing the spring constant of the wire, a resonance phenomenon specific to the second free vibration system is caused in a band lower than the resonance frequency provided by the first free vibration system. As a result, the acceleration sensitivity acting on the objective lens holding member in the objective lens driving device in each band of the resonance frequency provided by the first free vibration system and the resonance frequency provided by the second free vibration system is different. As a result, the resonance frequency inherent to the first free vibration system is substantially matched with the high-speed rotation frequency of the disk for the purpose of high-speed data transfer. The tracking performance is improved, and the resonance generated in the second free vibration system further reduces the displacement of the information recording track of the optical disk in the rotation frequency band of the disk at the standard data transfer speed. The tracking performance is improved, and the information recording track of the optical spot is recorded in at least two disk rotation frequency bands. It is possible to enhance the follow-up sensitivity to the position. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plan view of an objective lens driving device according to the present invention. FIG. 2 is a perspective view of the objective lens driving device according to the present invention. Fig. 3 shows a conventional objective lens. FIG. 4 is a diagram illustrating an example of an acceleration frequency characteristic of the driving device. FIG. 4 is a diagram showing an example of a conventional acceleration frequency characteristic of an objective lens driving device corresponding to a higher data transfer speed by increasing a primary resonance frequency. FIG. 5 is a diagram showing an example of an acceleration frequency characteristic of the objective lens driving device according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings, taking an objective lens driving device of an optical pickup used in a CD-ROM reproducing device as an example. In FIGS. 1 and 2, a focusing coil 3 for generating a driving force in a focusing direction parallel to the optical axis of the objective lens 1 is provided on an outer periphery of an objective lens holding member 2 for holding the objective lens 1. And a tracking coil 4 for generating a driving force in a tracking direction perpendicular to the optical axis of the objective lens are wound therearound. Printed circuit boards 5 are fixed to both side surfaces of the objective lens holding member 2, and are interposed therebetween. The two terminals of the focusing coil 3 and the tracking coil 4 are connected to one end of the four first metal wires 61 by soldering 13 so that the two terminals are connected to each other. Electrical continuity is established, and the other end of the metal wire 61 is soldered to the printed circuit board 81 fixed to the relay support block 71 in advance by solder 13 to establish electrical continuity between the two. It is connected and fixed while being.

That is, the objective lens holding member 2 is movably supported by the fiber support block 71 by elastic deformation of the four first metal wires 61. Further, one end of each of the four _ th metal wires B 2 is connected and fixed to the printed circuit board 81 fixed to the relay support block 71, so that the electrical connection with the first metal wires 61 is established. Electrical conduction is established, and the other end of the second metal wire 62 is fixed to the printed circuit board 82 fixed in advance to the support block 72 by screws 11 and the electrical connection between the two by the solder 13 The connection is fixed while electrical continuity is achieved. A static damping member 14 made of silicon or the like for stopping vibration is fitted into a portion of the fixed support block 72 to which the second metal wire 62 is fixed. The fixed support block 72 is fixed to a fixed portion such as a device base. That is, the relay support broke 71 is movably supported by the fixed portion by elastic deformation of four second metal wires 62 parallel to the first metal wire 61. Reference numeral 10 denotes a magnet fixed to the magnetic yoke 9 fixed to the fixed portion so as to oppose a gap between the focusing coil 3 and the tracking coil 4 with a predetermined gap. These form a magnetic circuit member. The magnet 10 generates a driving force due to Lorentz force on the focusing coil 3 and the tracking coil 4 by a predetermined driving current supplied through the first metal wire 61 and the second metal wire 62. A magnetic field is generated to cause this to occur. Thereby, the objective lens holding member 2 in a focusing direction parallel to the optical axis of the objective lens 1 and a tracking direction perpendicular to the optical axis in response to the current supply to the focusing coil 3 and the tracking coil 4. Is obtained, and the focus servo and tracking servo operations are performed.

Fig. 3 shows the acceleration frequency characteristics found in a conventionally used objective lens driving device. According to this, a remarkable increase in the acceleration gain was observed in the primary resonance frequency band. By making this frequency band substantially coincide with the rotation frequency band of the disk, the information recording track of the optical spot in the objective lens driving device was improved. It is possible to increase the sensitivity to follow the displacement. Furthermore, when the rotational frequency of the disk is increased for the purpose of speeding up data transfer, necessary means can be taken by increasing the primary resonance frequency of the objective lens driving device as shown in FIG. The tracking sensitivity in the wavenumber band can be increased. However, since the acceleration gain in the frequency band near the DC band decreases in inverse proportion to the square of the frequency increase with the increase in the primary resonance frequency, it is applied to music playback using a CD-ROM playback device. This may be a factor in reducing the sensitivity of the optical spot 21 to follow the displacement of the information recording trunk 23 in the low-speed rotation frequency band of the disk 22. Therefore, in the best mode for carrying out the present invention, as described above, two sets of four metal wires are used as the support means of the objective lens holding member 2, and one set of the first metal wires is used. 6 1 has one end fixed to the objective lens holding member 2 A first free vibration system based on the total mass of the member whose other end is fixed to the relay support member 71 and supported by the first metal wire 61 and the spring constant of the first metal wire 61 The other set of second metal wires 62 has one end fixed to the relay support member 71, the other end fixed to the fixing portion, and the other set of second metal wires 62. A second free vibration system is constituted by the total mass of the supported members and the spring constant of the second metal wire 62. By optimizing the mass of each component and the spring constant of the metal wires 61 and 62, as shown in FIG. The acceleration gain acting on the objective lens holding member 2 is increased in both a plate frequency band and a lower primary resonance frequency band unique to the second free vibration system.

As described above, two sets of free vibration systems using two sets of metal wires 61 and 62 as a set of four as the means for supporting the objective lens holding member 2 are configured, and the first free vibration system is formed. By making the resonance frequency inherent in the dynamic system substantially coincide with the high-speed rotation frequency band of the disk for the purpose of high-speed data transfer, the acceleration acting on the objective lens holding member 2 can be adjusted in the high-speed rotation frequency band of the disk. Music by using a CD-ROM playback device by increasing the resonance frequency of the second free vibration system in a frequency band lower than the resonance frequency specific to the first free vibration system. The object of the present invention is to achieve high-speed data transfer by increasing the acceleration in the low-speed rotation frequency band of the disk applied to reproduction or the like, more than the acceleration obtained only by the first automatic vibration system. In low-speed rotation frequency band both of the disc which is applied to the serial high-speed rotation frequency band and music playback of the disk, it is possible to improve the follow-up sensitivity to displacements of the information recording track of the optical sponge bets. Industrial applicability

INDUSTRIAL APPLICABILITY The objective lens driving device according to the present invention is useful as a driving device for driving an objective lens in an optical pickup for optically reading information recorded on a rotationally driven disk-shaped recording medium. It is suitable for use in optical information recording / reproducing devices that support two or more recording information transfer speeds, such as CD-ROM reproducing devices. £ zi66fcyJL3d

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Claims

The scope of the claims

1. An objective lens (1) is held, and a focusing coil (3) for generating a driving force in a focusing direction parallel to the optical axis of the objective lens (1) is provided on an outer peripheral portion of the objective lens (1). One end is attached to the objective lens holding member (2) having a tracking coil (4) wound around the optical axis of 1) that generates a driving force in the tracking direction perpendicular to the optical axis; Four first metal wires (61) fixed and the other end fixed to the relay holding member (71), one end is fixed to the relay holding member (71), and the other end is fixed to the fixing portion (71). 72) four second extra wires (62) fixed to the front IC focusing coil (3) and tracking via the first metal wire (61) and the second metal wire (62). By supplying current to the coil (4), a driving force is generated by Lorentz force. And a magnetic circuit member (9, 10) disposed on the fixed portion (72) so as to form a magnetic field for causing the objective lens holding member (2) to be connected to the first metal wire (61). ) Is movably supported by the relay holding member (71) by the elastic deformation of the fixing portion (72), and the fiber holding member (71) is movably supported by the elastic deformation of the second metal wire (62). An objective lens driving device characterized by being supported by (1).