JPH03266226A - Objective lens driver - Google Patents

Abstract

PURPOSE:To remove the influence of dust and dewing by fixing a part of three or more pieces, at least, of plate-shaped elastic members for a tracking direction positioned in plural planes containing axial line nearly parallel with the optical axis of an objective lens to a movable part. CONSTITUTION:Driving in a tracking direction T is attained because a lens holder 2 on which the objective lens 1 is fitted is driven by an electrodynamic type converter in which tracking coils 7a to 7d are arranged in the gap of a magnetic circuit consisting of magnets 5a, 5b and magnetic yokes 6a, 6b installed on a base 10, and it is rotated around the axial line by the deflection in a width direction of the tracking plate springs 4a to 4c. The driving in a focusing direction F is attained because it is moved in parallel by focusing plate springs 3a, 3b through the tracking plate springs 4a to 4c. Thus, since no friction is caused at the time of respective moving in the focusing direction F and the tracking direction T, stable performance free from the influence of the dust and the dewing can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device for an apparatus for optically writing or reading information on a disc-shaped recording medium.

Conventional technology Objective lens drive devices are designed to correct focus deviations caused by vertical movement of warped disk-shaped recording media such as compact discs, and tracking deviations caused by eccentricity. A conventional objective lens driving device of this type is shown in FIG. Even if it has a structure like this, it is a bridge plate.Driver 1 in the focus direction F.Objective lens 2.
Magnets 25a, 25b and magnetic yokes 26a, 26b are mounted on a base 29.
The electrodynamic transducer-1, which has a focusing coil 28 disposed in the gap of a magnetic circuit, can be obtained by sliding movement along the axis 23. Attached lens holder 22
is rotated about the axis 23 by an electrodynamic transducer in which tracking coils 27a, 27b are placed in the gap of a magnetic circuit consisting of magnets 25a, 25b and magnetic yokes 26a, 26b provided on a base 29. Even if the entire objective lens driving device is driven by a motor in the access direction AC (same direction as the tracking direction T) on the recording medium, the problem to be solved by the invention is as shown in FIG. In the objective lens drive device having the following configuration, drive in the focus direction is performed along the axis 23.1. Since the drive in the tracking direction is centered around the X and axis 23,
If dust or water droplets are inserted between the lens holder 3 and the lens holder 22, frictional resistance increases and it becomes difficult to perform stable focus tracking servo.Therefore, the present invention solves the above problems. For example, it provides a stable objective lens drive device that is not affected by dust or condensation.Means to solve the problemThe technical means to solve the above problem are as follows. Rope plate Length of the movable part including the objective lens At least three or more plate-shaped elastic members for the tracking direction (plate-shaped for the radial direction) located in a plurality of planes including an axis substantially parallel to the optical axis of the objective lens. One end of the elastic member (elastic member) is fixed to the movable part so that the movable part can move in the focusing direction. plate-shaped elastic member for direction)
By supporting the movable part via the plate-shaped elastic member for tracking direction, the action of the above-mentioned technical means is as follows. Due to the deflection of the shaped elastic member in the thickness direction, the movable part can rotate in the tracking direction about the axis. The focus direction is c when the tracking direction people move.
Since there is no friction, stable performance is achieved that is unaffected by dust or condensation. Furthermore, with respect to rotation around an axis perpendicular to the optical axis of the objective lens, extremely high rigidity can be obtained without causing in-plane deformation of the plate-like elastic member in the tracking direction.

EXAMPLE Hereinafter, an objective lens driving device according to an embodiment of the present invention will be explained with reference to the drawings. B)
is a sectional view taken along the line A-A in Figure 1 (A). Figure 2 is an exploded perspective view. Figure 3 (A) is a planar view showing drive in the tracking direction. Figure 3 (B) is a diagram showing drive in the focus direction. FIG.

As shown in FIG. 2, three tracking plate springs 4a to 4c, whose planes include an axis R parallel to the optical axis of the objective lens 1, are fixed to the lens holder 2 so as to sandwich the lens holder 2. Tracking plate springs 4a~4
Both ends of c are fixed to intermediate members 11a and Ilb, respectively. Review Mi Even though the intermediate members 11a and 11b are fixed to the base 10 by the focusing plate springs 3a and 3b, they are arranged as shown in FIG. 3(A)! Drive in the tracking direction T is performed by magnets 5a, 5b and a magnetic yoke 6a provided on the lens holder 2 to which the objective lens 1 is attached or on the base 10.
It is driven by an electrodynamic transducer in which tracking coils 7a to 7d are arranged in the air gap of a magnetic circuit consisting of 6b.
As shown in FIG. 3(B), driving in the focus direction F can be achieved by rotating the tracking leaf springs 4a to 4c around the axis R due to deflection in the thickness direction.
Lens holder 2 with objective lens 1 attached is base 1
0 magnets 5a, 5b and magnetic yokes 6a, 6b
The tracking plate spring 4a is driven by an electrodynamic transducer in which a focusing coil 8 is arranged in the gap of a magnetic circuit consisting of the focusing plate springs 3a and 3b.
obtained by translation through ~4c.

The entire objective lens drive device is moved in the access direction A on the recording medium.
c) In order to shorten the access time by driving the access with a motor in () the same direction as the racking direction T), the
By the balance weight 9, the objective lens 1, the lens holder 2, the balance weight 9, the focusing coil 8,
The center of gravity of the movable part consisting of the tracking coils 7a to 7d is made to coincide with the axis R. Furthermore, since no friction occurs when moving in the focus direction F and tracking direction T, stable performance is obtained that is not affected by dust or condensation. As shown in Fig. 2, the tracking plate spring 4a rotates around an axis perpendicular to the optical axis of the objective lens 1 (e.g.
α Tracking leaf springs 4b and 4c around the X axis
Due to the arrangement of the tracking leaf springs, the angles (for example, AI) made by adjacent leaf springs are all equal, as shown in Figure 5. By arranging the objective lens 1 in this way, it is possible to obtain almost uniform rigidity with respect to rotation around an axis perpendicular to the optical axis of the objective lens 1, regardless of the direction of the axis. In addition, two sets of tracking leaf springs are placed between the lens holders (
The number of tracking leaf springs in each set and the angle formed by adjacent leaf springs are the same (AI=81), and one set (4a to 4c) is divided into sets (4a to 4c and 4d to 4f).
c) of the other set (4d to 4f) of the tracking leaf springs.
) with respect to the tracking leaf spring, if it is attached to the lens holder in a position where it is rotated around axis 2 by approximately half the angle (B1), it will be more stable against rotation around the axis perpendicular to the optical axis. High rigidity can be obtained by using three or more tracking leaf springs and arranging them at equal angles, so that when driving not only in the tracking direction T but also in the focus direction F, the axis R passing through the center of gravity of the movable part Regarding the support in the focus direction, which makes it possible to provide even support to the target and achieve more stable displacement frequency characteristics: As shown in FIG. 3b
If the intermediate members 11a and 11b are omitted, and the tracking leaf springs 4a to 4c having hinge members are used as shown in FIG. 6, tracking can be achieved without impairing the effects of the present invention. Hinge member 4a for
4C and the focusing hinge member 3a, or the lens holder 2, and the number of assembly steps can be reduced. An objective lens drive device configured to obtain drive in the tracking direction by rotation, and the movable part including the objective lens has at least one movable part located within a plurality of planes including an axis substantially parallel to the optical axis of the objective lens. A portion of three or more tracking direction plate-like elastic members is fixed to the movable part so that the movable part can move in the focus direction, and a plurality of focus directions are substantially perpendicular to the optical axis and substantially parallel to each other. By supporting the movable part by the plate-like elastic member for the tracking direction via the plate-like elastic member for the tracking direction, the movable part rotates about the axis due to the deflection in the thickness direction of the plate-like elastic member for the tracking direction. It can be rotated as an axis in the tracking direction. Furthermore, by aligning the center of gravity of the movable part with the rotation axis, unnecessary resonance of the objective lens during access can be suppressed.
Since no friction occurs during movement in each tracking direction, stable performance is obtained that is not affected by dust or condensation. It is also possible to obtain very high rigidity due to in-plane deformation.

[Brief explanation of drawings]

Figure 1 (A) is a plane view of an objective lens driving device according to an embodiment of the present invention. Figure 1 (B) is a cross section taken along the line AA of Figure 1 (A). @ Figure 2 is an embodiment of the present invention. Fig. 3 (
A) is a planar view showing driving in the tracking direction. Figure 3 (B) is a front cross-sectional view showing driving in the focus direction. Figure 4 (A) is an objective lens driving device according to another embodiment of the present invention. The plane of Fig. 4(B) is A- of Fig. 4(A).
Cross-section A is shown in Fig. 5 in plan view showing the arrangement of the tracking plate spring, and Fig. 6 in perspective view showing the structure of the focusing hinge member and tracking hinge member.
A) is a plane view of a conventional objective lens drive device.
) is the BB sectional view of FIG. 7(A). 1...Objective lens f, 2... Lens holder, 3a
, 3b...Focus plate spring 4a-4c...Tracking plate spring 5a, 5b...Magnetic five 6a, 6b
...Magnetic yoke 7a-7d...Tracking coil) L,, 8...Focusing coil, 9...
・Balance weight, 10...one person 11a, l
lb...Intermediate member, F...Focus method KT...
Tracking direction, AC... access direction

Claims (10)

[Claims] (1) The objective lens of a device for optically writing or reading information onto or from a disc-shaped recording medium is aligned in a radial direction parallel to the recording medium surface of the disc-shaped recording medium and in a direction parallel to the recording medium surface. one or more radial drive coils for driving the movable part in the radial direction; and a mechanism for driving the movable part in the optical axis direction in the perpendicular direction. one or more optical axis direction drive coils to provide magnetic flux to the optical axis direction drive coil; one or more radial direction magnetic circuits to provide magnetic flux to the optical axis direction drive coil; at least three radii located within a plurality of planes including an axis substantially parallel to the optical axis of the objective lens. A part of the plate elastic member for the radial direction is fixed to the movable part, and the plate elastic member for the radial direction is fixed by a plurality of plate elastic members for the optical axis direction that are substantially perpendicular to the axis and substantially parallel to each other. An objective lens driving device, characterized in that the movable part is supported through the movable part. (2) The angle formed by adjacent radial plate elastic members is
The objective lens driving device according to claim 1, wherein the objective lens driving device is substantially the same. (3) Two sets of radial plate-like elastic members are provided with the lens holder sandwiched between them in the optical axis direction, and the radial plate-like elastic members in the same group are The radial plate elastic members of one set have substantially the same angle with respect to the radial plate elastic members of the other set. 2. The objective lens driving device according to claim 1, wherein the objective lens driving device is mounted so as to be rotated about the axis by a half angle. (4) The objective lens driving device according to claim 1, wherein the center of gravity of the movable part is made substantially coincident with the axis. (5) Claim 1, characterized in that the plate-shaped elastic member for the radial direction is formed of a metal plate spring made of stainless steel, phosphor bronze, beryllium copper, etc., and is integrally molded with the plate-shaped elastic member for the optical axis direction. The objective lens driving device described in . (6) The radial plate-like elastic member has a plurality of flat plate portions located within a plurality of planes including the axis, and both ends of the flat plate portions are deflected in a direction substantially perpendicular to the optical axis direction. 2. The objective lens driving device according to claim 1, wherein the objective lens driving device comprises a flexible thin hinge portion, one end of which is attached to a lens holder, and the other end of which is attached to a plate-like elastic member for the optical axis direction. (7) The plate-like elastic member for the optical axis direction includes a plurality of flat plate parts,
The patent claim is characterized in that the flat plate part has thin hinge parts at both ends that are flexible and deformable in the optical axis direction, and one end is attached to a fixed part and the other end is attached to a radial plate-shaped elastic member. The objective lens driving device according to scope 1. (8) The objective lens drive device according to claim 6, wherein the radial plate-like elastic member and the lens holder are integrally molded. (9) The objective lens driving device according to claim 6 or 7, wherein the plate-like elastic member for the radial direction and the plate-like elastic member for the optical axis direction are integrally molded. (10) The objective lens driving device according to claim 6 or 7, characterized in that the plate-like elastic member for the radial direction, the plate-like elastic member for the optical axis direction, and the lens holder are integrally molded.