JPH03273533A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To prevent the oscillation in a tracking direction and to obviate the deterioration in the frequency response characteristic of the displacement in a focusing direction by positioning the approximate center of gravity of a moving part to the inside of a stationary node and crimping and supporting the stationary node from an optical axis direction by parallel leaf springs. CONSTITUTION:This device is constituted of an objective lens 1, a lens holder 2, a balance member 3, two pieces of intermediate nodes 4, one piece of the stationary node 5, one set of the parallel leaf springs 6, a tracking driving means 10, and a focusing driving means 9. The approximate center of gravity of the moving part consisting of the objective lens 1, the lens holder 2, the balance member 3, the intermediate nodes 4, and the stationary node 5 is positioned in the stationary node 5. The total sum of the inertia moment around the center of rotation in the tracking direction of the lens holder is thereby held zero even if the impact and acceleration in the tracking direction are applied from the outside. The oscillation of the objective lens in the tracking direction is obviated. The deterioration in the frequency response characteristic of the displacement in the tracking direction is obviated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention 1 relates to an objective lens driving device for an apparatus for optically recording or reproducing information on a disc-shaped recording medium.

Conventional technology An objective lens drive device moves an objective lens in an optical axis direction perpendicular to the surface of the recording medium in order to correct focus deviation caused by vertical movement of a warped disk-shaped recording medium such as a compact disk, and tracking deviation caused by eccentricity. (hereinafter referred to as a focus direction F) and a radial direction parallel to the recording medium surface (hereinafter referred to as a tracking direction T).

An example of a conventional objective lens driving device will be described below with reference to the drawings.

FIG. 3 is a perspective view showing the configuration of a conventional objective lens driving device. In FIG. 3, F is a focusing direction rKT is a tracking direction, 101 is an objective lens, 102 is a lens holder to which the objective lens 101 is attached, A tracking hinge 103 is provided to allow the lens holder 102 to rotate freely in the tracking direction T. A tracking hinge 104 is connected by four hinge parts, and the lens holder 102 can be moved in the focusing direction F via the tracking hinge part 103. Parallel lens for focusing supported by 105
are support parts 106 a and 106 b that support the parallel link for focusing 104; and support parts 106 a and 106 b are plates having rotational axes in a direction parallel to the focusing direction F; and focusing coils I, 107 fixed to both sides of the lens holder 102 in the tracking direction T. a and 107b are plates having rotation axes in a direction perpendicular to the focus direction F and the tracking direction T; a tracking coil I fixed to the surface of the lens holder 102 on the opposite side to the tracking hinge part 103 with respect to the objective lens 101; ,, 108a, 108
b are focusing coils 106a, 106b
Two focusing magnets 109 are located at opposing sides of the tracking coils 107a and 10.
Tracking magnets K 110a, 110b installed at positions facing a part of the surface in the direction of the orbital axis of 7b,
110c is a focusing magnet 108a, 108
The focusing coil 106 is attached to the rear side yoke 111a and 111b that fix the tracking magnet 109 and the tracking magnet 109.
The two opposing yaws 112 installed inside the supports 105. Back yoke 110a, 1
10b, 110c and opposing yokes 111a, 111
The operation of the objective lens drive device configured as described above will be explained below. The focusing coils 106a and 106b receive the electromagnetic force obtained by orthogonal to the magnetic flux generated by the focusing magnets 108a and 108b. The tracking coils 107a and 107b, which are fixed to the lens holder 102 to which the objective lens 101 is attached, perform tracking in the tracking direction T. The lens holder 102 receives an electromagnetic force orthogonal to the magnetic flux generated by the tracking magnet 109, and rotates around the tracking hinge part 103. With this configuration, the lens holder 102 is supported so as to rotate around the tracking hinge part 103 in the tracking direction T.
When an external shock or acceleration in the tracking direction T is applied to the objective lens drive device, the objective lenses 1 and 01 held by the lens holder 102 vibrate due to the inertial force acting on the lens holder 102. It becomes more likely to occur. In particular, when performing high-speed access, there is a problem that a desired track cannot be quickly accessed due to the vibration of the objective lens 101 as described above. The objective lens is supported by a parallel link 104 for focusing via a parallel link 103, and has a misalignment with respect to the position where the lens holder 102 is supported and the center of gravity position +i of the lens holder 102, the direction perpendicular to the focusing direction F and the tracking direction T. 1
01 in the focus direction F, the lens holder 102 tends to rotate around an axis parallel to the tracking direction T, which deteriorates the displacement frequency response characteristic in the focus direction F. By matching the center of rotation of the lens holder in the tracking direction and the support position in the focus direction with the approximate center of gravity of the lens holder, unnecessary vibration of the objective lens in the tracking direction can be prevented and the focus direction can be driven. The objective of the present invention is to provide a water objective lens driving device that realizes stable support and driving that can prevent the lens holder from rotating around an axis parallel to the tracking direction when the lens holder is rotated.

In order to solve the above problems, the objective lens driving device of the present invention includes an objective lens of a device for writing or reading optical information on a disc-shaped recording medium, a lens holder for holding the objective lens, and a balance member. , two intermediate nodes having thin hinge portions at both ends connecting the lens holder and the balance member by forming parallel links; and thin walls at both ends connecting the center portions of each of the two intermediate nodes. one fixed node having a hinge portion, at least one set of parallel leaf springs that support the fixed node by sandwiching it from the optical axis direction, and moving the objective lens in a radial direction parallel to the disk-shaped recording medium. and a focusing drive means to move the objective lens in the optical axis direction. Even though the approximate center of gravity of the lens holder is located inside the fixed section, this configuration allows the center of rotation of the lens holder in the tracking direction and the support position in the focus direction, and the approximate center of gravity of the movable part consisting of the objective lens and the lens holder to be adjusted. Even if they can be made to match, as a result, an impact or acceleration in the tracking direction T is applied to the objective lens drive device from the outside.
The sum of the moments of inertia around the center of rotation of the lens holder in the tracking direction is zero, so the objective lens does not vibrate in the tracking direction.Also, when driving the objective lens in the focus direction, the support position and approximate center of gravity of the lens holder The lens holder will not rotate around the axis parallel to the tracking direction.
An objective lens driving device according to an embodiment of the present invention will be described below with reference to the drawings. Figure 2 is an exploded perspective view showing the configuration of the lens drive device. Figure 2 is a front view of the lens holder showing the movement of the objective lens in the tracking direction. is the focusing direction fi) T is the tracking direction 1 is the objective lens'
X, 2 is a lens holder that holds objective lens 1, 3 is a balance member, 4 is lens holder 2 and balance member 3
5 has thin hinge parts at both ends that connect the middle sections of the middle nodes of the two parallel links 4. The fixed bar has a center of gravity a that is parallel to the optical axis direction of the objective lens 1 and passes through the approximate center of gravity of the movable part consisting of the objective lens 1, the lens holder 2, the balance member 3, two intermediate sections 4, and the fixed section 5.
6 is a set of parallel plates that support the fixed node 5 movably in the focus direction F by sandwiching it from the direction of the center of gravity; 7 is two permanent magnets attached to the two intermediate nodes 4; 8 is a Two opposing yoke coils 9 are wound around the opposing yoke 8 and drive the objective lens 1 in the focusing direction F by the permanent magnet 7; 10 are two focus coils that are wound around the opposing yoke 8 and drive the objective lens 1 by the permanent magnet 7 Two tracking coils driven in the tracking direction T; 11 is a support part 1 that supports a pair of parallel leaf springs 6;
Reference numeral 2 designates a base on which the two opposing yokes 8 and the support portion 11 are fixed.

In the objective lens drive device configured as above,
The operation will be explained below. First, the objective lens 1 is driven in the focus direction F (the focus coil 9 wound around the opposing yoke 8 is perpendicular to the magnetic flux generated by the permanent magnet 7 attached to the intermediate nodes 4 of the two The objective lens 1 supported by the parallel plate spring 6 is driven in the focusing direction F by the reaction of the electromagnetic force obtained by the magnetic yoke. The tracking coil 10 wound around 8 receives an electromagnetic force obtained by being orthogonal to the magnetic flux generated by the permanent magnet 7 attached to the two intermediate nodes 4, and its reaction produces the force shown in FIG. As described above, the lens holder 2 and the balance member 3, which are connected by two intermediate nodes 4, translate around the fixed node 5, and the objective lens 1 is driven in the tracking direction T. According to the embodiment of the present invention, there are a lens holder 2 that holds the objective lens 1, a balance member 3, and two lenses having thin hinge portions at both ends that connect the lens holder 2 and the balance member 3 by forming a parallel link. The middle clause 4 of
The movable part is composed of one fixed joint having thin hinge parts at both ends that connects the central part of each of the two intermediate joints 4, and the approximate center of gravity of the movable part is located inside the fixed joint 5, and the movable part is parallel to each other. By sandwiching and supporting the fixed node from the optical axis direction with the leaf spring, the center of rotation of the lens holder 2 in the tracking direction T and the support position in the focus direction F can be made to coincide with the approximate center of gravity of the movable part. .

As a result, an external shock or acceleration in the tracking direction T is applied to the objective lens drive device, and the sum of the moments of inertia of the lens holder 2 around the center of rotation in the tracking direction T becomes zero, and therefore the objective lens 1 vibrates in the tracking direction T. Also, when the objective lens 1 is driven in the focus direction F, the support position of the lens holder 2 and the center of gravity are approximately the same.The lens holder 2 rotates around an axis parallel to the tracking direction T. Therefore, the objective lens 1 does not cause track deviation due to impact or acceleration in the tracking direction T, and the desired position is maintained even during high-speed access. It is possible to realize an objective lens driving device that can quickly access a track and can obtain stable displacement frequency response characteristics in the focus direction F.

Ma? =Using the permanent magnet 7 as the driving force generating part of the objective lens 1Lz By winding the tracking coil 10 and the focus coil 9 around the opposing yoke 8, the temperature rise of the objective lens 1 when the objective lens 1 is driven can be reduced. Furthermore, since there is no need to connect a lead wire to the lens holder 2, reliability can be improved.Advantages of the Invention The present invention provides a lens holder for holding an objective lens, a balance member, and a lens holder. and a balance member by forming a parallel link, two intermediate sections having thin-walled hinges at both ends, and one intermediate section having thin-walled hinges at both ends, connecting the central portions of each of the two intermediate sections. A movable part is formed by the fixed joint, the center of gravity of the movable part is located inside the fixed joint, and the fixed joint is held and supported from the optical axis direction by a parallel plate spring, thereby rotating the lens holder in the tracking direction. The support position in the center and focus direction can be made to coincide with the substantially center of gravity position of the movable part.

When an impact or acceleration in the tracking direction T is applied to the objective lens drive device from the outside, the sum of the moments of inertia of the lens holder around the center of rotation in the tracking direction T becomes zero, and therefore the objective lens vibrates in the tracking direction T. (Also, when driving the objective lens in the focus direction F, the support position of the lens holder and the center of gravity position must match. The lens holder does not rotate around the axis parallel to the tracking direction T, and the focus No deterioration of displacement frequency response characteristics in direction F
Therefore, the objective lens does not cause track deviation due to impact or acceleration in the tracking direction T, and a desired track can be quickly accessed even during high-speed access, and the displacement frequency response in the focus direction F is stable. It is possible to realize an objective lens driving device that can obtain characteristics.

[Brief explanation of drawings]

Figure 1 is an exploded perspective view showing the configuration of an objective lens drive device according to an embodiment of the present invention; Figure 2 is a front view of the lens holder showing the movement of the objective lens in the tracking direction; Figure 3 is a conventional objective lens drive. FIG. 2 is a perspective view showing the configuration of the device. F... Focusing KT... Tracking IKK
...center of gravity line 1...objective lens i'i6...parallel plate *, 7.
...Permanent magnet 8...Opposing magnet 9...Focusing light L,, 10...Tracking light L)
, 11... Support part 12... One person 101...
...Objective lens 102...Lens holder, 103.
・・Hinge i for tracking 104 ・Parallel sunk for focusing 105 --・Support K 106a,
106b=focusing coil, 107a,
107b...Tracking Koinok 108a,
108b...Focusing magnet K 109--Tracking magnet 110a, 110b, 11
0 c ・---Back side 111a, 111b...
・Opposing Yokyu 112a, 112b... alone

Claims (1)

[Claims] An objective lens of a device for writing or reading optical information on a disk-shaped recording medium, a lens holder for holding the objective lens, a balance member, and a 2 having thin hinge portions at both ends of the lens holder and the balance member. A parallel link connected by an intermediate node of the book, one fixed node having thin hinge portions at both ends connecting the center portions of each of the two intermediate nodes, and the fixed node is sandwiched from the optical axis direction. at least one set of parallel plate springs supported by a parallel plate spring; tracking drive means for moving the objective lens in a radial direction parallel to the disk-shaped recording medium; and focusing drive means for moving the objective lens in the optical axis direction. 1. An objective lens drive device, wherein a substantially center of gravity of a movable portion comprising the objective lens, the lens holder, the balance member, the two intermediate sections, and the fixed section is located inside the fixed section.