Object lens drive unit

Abstract

An object lens drive unit in which an undesired displacement or inclination of an object lens with respect to an optical disc is reduced. The position at which a lens holder for the object lens is supported by a pair of rod-shaped elastic support members in the focusing direction substantially coincides with the center of the tracking coil in the focusing direction.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic perspective view of an object lens drive unit according to a first embodiment of the invention.

FIG. 2A and FIG. 2B show schematic perspective views illustrating how the object lens drive unit shown in FIG. 1 is driven in the radial tilt direction and the tangential tilt direction.

FIG. 3A and FIG. 3B show a method for stabilizing the supporting of the lens holder by the rod-shaped elastic support members of the object lens drive unit shown in FIG. 1.

FIG. 4 shows the shape of the second rod-shaped elastic support members and the third rod-shaped elastic support members of the object lens drive unit shown in FIG. 1.

FIG. 5 schematically shows how the second rod-shaped elastic support members and the third rod-shaped elastic support members in the object lens drive unit according to a second embodiment of the invention are fixed.

FIG. 6 schematically shows the positions at which the first rod-shaped elastic support members, the second rod-shaped elastic support members, and the third rod-shaped elastic support members of the object lens drive unit according to a third embodiment of the invention are each fixed on the lens holder.

FIG. 7 shows an example of an optical pickup in which the object lens drive unit of the invention is mounted.

FIG. 8 shows an example of an optical disc drive in which the optical pickup shown in FIG. 7 is mounted.

FIG. 9 shows the output signal due to the inclination between the optical disc and the object lens in the optical disc drive shown in FIG. 8.

FIG. 10 schematically shows the positions at which the second rod-shaped elastic support members of the object lens drive unit according to a fourth embodiment of the invention are supported.

Claims

1. An object lens drive unit comprising: an object lens for focusing light on a recording surface of an optical disc;a lens holder for holding the object lens;a pair of first rod-shaped elastic support members for supporting the lens holder;a drive means for the lens holder, the drive means comprising:a focusing coil and a tracking coil for driving the lens holder in a direction towards or away from the optical disc and in a radial direction of the optical disc;a radial tilt coil and a tangential tilt coil for causing the lens holder to be inclined in a radial direction and a tangential direction of the optical disc; anda magnetic circuit,wherein the position at which the lens holder is supported by the first rod-shaped elastic support members in the focusing direction substantially coincides with the position of the center point of the tracking coil in the focusing direction.

2. An object lens drive unit comprising: an object lens for focusing light on a recording surface of an optical disc;a lens holder for holding the object lens;a pair of first rod-shaped elastic support members for supporting the lens holder;a drive means for the lens holder, the drive means comprising:a focusing coil and a tracking coil for driving the lens holder in a direction towards or away from the optical disc and in a radial direction of the optical disc;a radial tilt coil and a tangential tilt coil for causing the lens holder to be inclined in a radial direction and a tangential direction of the optical disc; and a magnetic circuit,wherein the point at which the lens holder is supported by the first rod-shaped elastic support members substantially coincides with the geometric center or the center of gravity of the tracking coil.

3. The object lens drive unit according to claim 1 or 2, comprising at least two pairs of second rod-shaped elastic support members that support the lens holder on the opposite side from the first rod-shaped elastic support members with respect to the tangential direction, wherein the second rod-shaped elastic support members have a smaller axial stiffness than the first rod-shaped elastic support members, wherein the position at which one of the two pairs of the second rod-shaped elastic support members support the lens holder in the focusing direction and the position at which the other pair supports the lens holder in the focusing direction are substantially symmetric with respect to the point at which the first rod-shaped elastic support members support the lens holder.

4. The object lens drive unit according to claim 3, comprising a pair of third rod-shaped elastic support members that support the lens holder on the opposite side from the first rod-shaped elastic support members with respect to the tangential direction, wherein the third rod-shaped elastic support members have a smaller axial stiffness than the first rod-shaped elastic support members, wherein the position at which the third rod-shaped elastic support members support the lens holder in the focusing direction substantially coincides with the position at which the first rod-shaped elastic support members support the lens holder in the focusing direction.

5. The object lens drive unit according to claim 3 or 4, wherein the point at which the two pairs of the second rod-shaped elastic support members support the lens holder, the point at which the third rod-shaped elastic support members support the lens holder, and the point at which the first rod-shaped elastic support members support the lens holder do not lie in the same plane perpendicular to the tangential direction.

6. The object lens drive unit according to claim 4 or 5, wherein the first rod-shaped elastic support members, the second rod-shaped elastic support members, and the third rod-shaped elastic support members are made of electrically conductive material, wherein they each supply current to the focusing coil, the tracking coil, the radial tilt coil, or the tangential tilt coil.

7. The object lens drive unit according to any one of claims 3 to 6, wherein the end of the second rod-shaped elastic support members opposite to the end thereof at which the lens holder is supported is supported by a fixing portion, wherein the interval of two points at which each pair of the second rod-shaped elastic support members is supported by the fixing portion is narrower than the interval of the two points at which each pair of the second rod-shaped elastic support members support the lens holder.