JPH01182936A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To raise a resonance frequency and the band of a track follow-up control and to improve follow-up accuracy by fixing a bearing at a tracking driving magnetic circuit fixed on a base. CONSTITUTION:An upper and lower pair of elastic member 4 is arranged inside two flats vertical to a focusing direction 1001, one edge is fixed at an objective lens holding member 2, and the other edge is fixed at a turning member 52. The turning member 52 is driven in a tracking direction 1002 by impressing a tracking driving signal to a tracking driving coil 16 fixed to the turning member 52. The axis 6 is fixed to the turning member 52, supported by two bearings 20 and 22, and the bearings 20 and 22 are fixed to a tracking driving magnetic circuit 44 fixed on a base 58. Thus, a resonance frequency in the case that the turning member 52 is driven in the tracking direction 1002 can be raised, and in its turn, the control band of a track following-up can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device in an optical head used in an optical information recording/reproducing device.

2. Description of the Related Art In recent years, many recording and reproducing devices for video, audio, etc. using optical disks have been announced, and related technologies have also progressed accordingly. In particular, various methods have been proposed for optical pickup, but one of the important issues is to improve the frequency characteristics of the actuator.

Optical reading devices are known for a long time, in particular for the responsive correction of focusing and tracking.
Patent application 1986-2 for a mechanism that drives the objective lens two-dimensionally
No. 93842, and has a structure as shown in FIGS. 3 and 4.

FIG. 3 is a perspective view of a conventional objective lens drive device, and the fourth
The figure is a sectional view taken along arrow A in FIG. 3.

1001 indicates a focusing direction, and 1002 indicates a tracking direction.

100 is an objective lens, and an objective lens holding member 102 is held so that its optical axis is parallel to the focusing direction 1001.
is fixed. A pair of upper and lower elastic members 104 are arranged in two planes perpendicular to the focusing direction 1001, and one end is fixed to the objective lens holding member 102 and the other end is fixed to the rotating member 202. The elastic member 104 is configured as a parallel spring by a thin temporary spring arranged so that the section modulus is small in the focusing direction 1001 and the section modulus is large in the tracking direction 1002.

This allows the objective lens holding member 102 to be flexible in the focusing direction 1001 and flexible in the tracking direction 1002.
is strongly supported.

A balancer 218 corrects the amount of unbalance of the objective lens 100, the rotating member 202, the parallelogram prism 132, etc. with respect to the rotating axis, and is arranged so that the center of gravity of the movable part is on the rotating axis. .

204 is a tracking drive magnetic circuit fixed to a base 208, to which the tracking drive magnet 108 is fixed. A magnetic flux is generated in the magnetic gap of the tracking drive magnetic circuit 204 in a direction parallel to the focusing direction 1001, and by applying a tracking drive signal to the tracking drive coil 1) 6 fixed to the rotating member 202, the tracking direction is changed. 1002.

The shaft 206 is fixed to the rotating member 202. axis 206
is supported substantially perpendicularly to the surface of the disk 200 by two bearings 120.122;
22 is an arm housing 2 provided on the base 208;
12 and a base 208, respectively.

The shaft 206 is provided with an opening 210 so that the first reflective surface 214 of the parallelogram prism 132 can be located at the center of rotation of the shaft 206, and the opening 210 is provided with the shaft 206.
6 is connected to a hole 126 provided at the center of rotation.

The laser beam emitted from the fixed optical system 128 passes through the hole 126.
, is totally reflected by the first reflecting surface 214 and the second reflecting surface 216, and is guided to the objective lens 100.

Reference numeral 140 denotes a focus drive magnetic circuit fixed to the base 208, and the gap portion 146 is formed in an arc shape centered on the rotation wheel of the rotation member 202, and a magnetic field is formed in the radial direction of the gap portion 146.

Reference numeral 138 denotes a focus drive coil located in the gap portion 146 and fixed to one end of the objective lens holding member 102. By applying a signal corresponding to the focusing error signal to this focus drive coil 138, the objective lens 100 is moved in the focusing direction 1001,
The distance from the recording surface of the recording/reproducing disk 200 can be kept constant. 'Problems to be Solved by the Invention However, with the above configuration, when trying to drive the rotating member 202 in the tracking direction 1002, resonance occurs in this part due to the small rigidity of the arm housing 212, which causes problems in tracking. The drawback was that the control band could not be increased.

Means for Solving the Problems In order to solve the above problems, the objective lens drive device of the present invention is configured such that a bearing is fixed to a tracking drive magnetic circuit fixed to a base.

Effect of the Invention With the above configuration, the present invention can provide high rigidity even when the rotating member is driven in the tracking direction, so the tracking control band can be increased, and the laser beam can be directed to the track with high precision. It can be followed.

Embodiment An embodiment of the objective lens driving device of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective sectional view showing an embodiment of the objective lens driving device of the present invention, and FIG. 2 is an assembled view of the main parts of the present invention.

In FIGS. 1 and 2, 1001 indicates the focusing direction, and 1002 indicates the tracking direction.

Reference numeral 100 denotes an objective lens, which is fixed to the objective lens holding member 2 so that its optical axis is parallel to the focusing direction 1001. A pair of upper and lower elastic members 4 are arranged in two planes perpendicular to the focusing direction 1001, and one end is fixed to the objective lens holding member 2 and the other end is fixed to the rotating member 52. This elastic member 4 is
001 has a small section modulus, and is configured as a parallel spring in the focusing direction 1001 by thin leaf springs arranged so that the section modulus is large in the tracking direction 1002. As a result, the objective lens holding member 2 is supported flexibly in the focusing direction 1001 and rigidly in the tracking direction 1002.

44 is a tracking drive magnetic circuit fixed to the base 58, and the tracking drive magnet 8 is fixed thereto. A magnetic flux is formed in the magnetic gap of the tracking drive magnetic circuit 44 in a direction parallel to the focusing direction 1001. By applying a tracking drive signal to the tracking drive coil 16 fixed to the rotation member 52, the rotation member 52 is driven in the tracking direction 1002.

At this time, the height of the center of gravity of the movable parts such as the objective lens 100, the objective lens holding member 2, the rotating member 52, and the tracking drive coil 16 is approximately the same height as the height at which the tracking drive coil 16 is arranged. , Therefore, the generated thrust is approximately at the same height as the center of gravity of the moving part.

The shaft 6 is fixed to a rotating member 52. The shaft 6 is supported by two bearings 20.22.
is fixed to the tracking drive magnetic circuit 44 fixed to the base 58. Normally, magnetic circuits are made of iron-based materials with a certain degree of thickness in order to reduce leakage magnetic flux, so their rigidity is quite high. Therefore, the resonant frequency of this portion can be made relatively high.

The shaft 6 is provided with an opening 10 so that the first reflecting surface 14 of the parallelogram prism 32 can be located at the center of rotation of the shaft 6, and the opening 10 is also located at the center of rotation of the shaft 6. It is connected to the provided hole 26.

The laser beam emitted from the fixed optical system 28 passes through the hole 26, is totally reflected by the first reflecting surface 14 and the second reflecting surface 46, and is guided to the objective lens 100.

40 is a focus drive magnetic circuit fixed to the tracking drive magnetic circuit 44, and the gap portion 48 is a rotating member 52.
It is formed in an arc shape centered on the rotation axis, and a magnetic field is formed in the radial direction.

38 is a focus drive coil located in the gap portion 46 and fixed to one end of the objective lens holding member 2. By applying a signal corresponding to the focusing error signal to the focus drive coil 38, the objective lens 100 is
By moving the lens in the focusing direction 1001, the distance from the recording surface can be kept constant.

In the device configured as above, the bearing 20°22
By fixing this to the tracking drive magnetic circuit 4, it is possible to increase the resonance frequency when the rotating member 52 is driven in the tracking direction 1002, and as a result, it is possible to increase the control band for track following.

Effects of the Invention As described above, in the present invention, by fixing a bearing to a highly rigid tracking drive magnetic circuit, the resonant frequency can be increased even when a rotating member is rotationally driven. , the band of track following control can be increased. Therefore, the tracking accuracy for the track can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective sectional view of an objective lens driving device of the present invention;
2 is an assembled view of the main parts of FIG. 1, FIG. 3 is a perspective view of a conventional objective lens driving device, and FIG. 4 is a sectional view of FIG. 3. 2...Objective lens, 4...Elastic member,
6... Axis, 8... Tracking drive magnet, 16... Tracking drive coil, 2o,
22...Bearing, 32...Parallelogram prism, 38...Focus drive coil, 4o
...Focus drive magnetic circuit, 52...
・Rotating member. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1: Focus island EvJ, concave shaft Figure 2: 1θθ - Objective lens 2θZ゛° Concave auxiliary arm 206 --- Axis Figure 3

Claims (3)

[Claims] (1) an objective lens; an objective lens holding member that moves integrally with the objective lens; one end is fixed to the objective lens holding member; the other end is centered on a first axis parallel to the optical axis of the objective lens; an elastic member fixed to a rotating member that rotates as a rotation member; an optical path changing means for guiding light from the optical axis to the one axis; and the rotating member is rotatable about the first axis. the objective lens holding member has a focusing drive coil that is driven in the optical axis direction of the objective lens, and the rotating member generates torque around the first axis. at least one tracking drive coil, the tracking drive coil being arranged in a tracking drive magnetic circuit having a magnetic gap in the rotating direction of the rotating member, and the optical path changing means Two planar reflecting surfaces that are fixed to the moving member and are inclined with respect to the optical axis are arranged parallel to each other and opposite each other, and the pair of bearings is arranged such that one of the bearings rotates in the rotation direction. An objective lens driving device, wherein one of the pair of bearings is disposed above the member and the other is disposed below the rotating member, and each of the pair of bearings is fixed to a yoke of the tracking drive magnetic circuit. (2) The objective lens driving device according to claim (1), wherein the optical path changing means is constituted by one parallelogram prism. (3) The objective lens drive device according to claim (1), wherein the center of gravity of the optical path changing means and the rotating member is arranged at approximately the same height as the tracking drive coil.