JPH04330644A - Objective lens actuator - Google Patents

Abstract

PURPOSE:To prevent the generation of the auxiliary resonance generated at a low frequency as the moment rigidity of a member, such as leaf spring, supporting an objective lens holder is low and to stabilize control. CONSTITUTION:A holder case 4a of the objective lens holder 2 is supported to a reference base 14 with a point contact using a V-groove and a steel ball 13. This holder case is brought into pressurized contact at plural points with piezo elements and the steel ball from the reference base side. The holder case is inclined according to the inclination of the disk surface by driving the piezo elements 6a, 6b, 6c, 6d.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator for an optical head in an optical disk master exposure machine or an information reading device, and more particularly to an objective lens actuator that does not use a leaf spring or the like to support an objective lens holder. It is something.

0002

2. Description of the Related Art An optical head is used to reproduce, record, and erase information from a master optical disk (hereinafter referred to as a disk). An objective lens actuator is incorporated to cause the lens to follow the movement of the disk.

The configuration of this objective lens actuator is as follows:
Various methods have been devised in the past, including JP-A-63-2
In the No. 5841 publication, as shown in FIG. 7, tracking coils 3a, 3b and tracking magnets 5a, 5b for sandwiching the objective lens 1 and driving it in the tracking direction are provided on the base 8, and Focusing coils 2a, 2b and focusing magnet 6a for driving in the focus direction,
6b is provided so as to be able to independently drive at least two locations in the radial direction of the disk by sandwiching the objective lens 1, and adds a signal detecting the inclination of the disk (or base 8) to each drive circuit in reverse phase. A configuration is disclosed in which the objective lens 1 is tilted according to the tilt of the disk by inputting the following information.

0004

However, in the above-described conventional objective lens actuator, two focusing coils 2 arranged in the radial direction of the disk.
In order to tilt the objective lens 1 by applying currents of different magnitudes to a and 2b, the moment rigidity of a leaf spring (not shown), which is a support member in the focus direction, must be reduced to some extent. For this reason, there is a problem in that secondary resonance such as torsional resonance occurs at low frequencies in the movable part, making control unstable. In addition, due to an assembly error in the two focusing coils 2a and 2b, the drive vectors of the electromagnetic force generated in these two coils are not in the same direction, resulting in unnecessary secondary resonance and unstable control. There was a problem with that.

Therefore, the present invention solves the above-mentioned conventional problems, prevents unnecessary secondary resonance such as torsional resonance from occurring in the movable part, and enables stable control of the objective lens holder. The objective is to provide a possible objective lens actuator.

[0006]

[Means for Solving the Problems] The gist of the present invention is to provide an objective lens holder which is incorporated into an optical head for reproducing or recording information on an optical disk, and which has an objective lens and a focusing coil attached thereto. An objective lens actuator, which includes the objective lens holder so as to be movable in the optical axis direction by energizing the focusing coil, and has a plurality of locking parts at the end of the opposite side of the objective lens. L that supports the case and the locking part of the holder case from above and below.
It consists of a reference base having a plurality of support parts having a letter shape and a predetermined elasticity and a piezo element provided near the support parts, and the locking part and each opposing surface in the optical axis direction of the support part and the locking part. A V-shaped groove is provided at a position where the piezo element faces each other, and a steel ball is arranged between the V-shaped grooves so that the holder case and the reference base are in point contact. By energizing the element, the holder case is tilted in accordance with the tilt of the optical disc surface so that the optical axis is substantially perpendicular to the tilted surface.

[0007]

[Operation] Therefore, in controlling the focus direction, the objective lens holder is moved in the optical axis direction by controlling the energization of the drive coil of the objective lens holder. In addition, if the disk (or substrate) has a tilt such as warpage, the holder case can be tilted at a predetermined angle with respect to the optical axis by adjusting the amount of current applied to each piezo element accordingly, and the optical axis of the objective lens can be tilted at a predetermined angle. is approximately perpendicular to the disk surface. In this way, since no spring or the like is used to support the objective lens holder, occurrence of secondary resonance etc. is prevented.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a hydrostatic bearing 12 is formed between an objective lens holder 2, which has an objective lens 1 attached to its bottom and a drive coil 10 wound around its top, and a bearing housing 3 formed in a holder case 4. It is arranged in the holder case 4 so as to An inner yoke 7 to which a permanent magnet 8 and an outer yoke 9 are fixed is fixed to the holder case 4 so that the drive coil 10 wound around the objective lens holder 2 is disposed in the magnetic gap. .

Further, the locking portion 4a of the holder case 4 and the support portion 5a of the reference base 5 that abuts the locking portion 4a and supports the holder case 4 are shown in FIG. 2 (top view), FIG. 4, V-shaped grooves 4b, 4c and 5b are formed respectively, and between these V-shaped grooves 4b and 5b, and between the V-shaped grooves 4
c and piezo elements 6a, 6b, 6c provided on the reference base 5
, 6d, so that the steel ball 13 is placed in point contact with the holder case 4 and the reference base 5.

In the above configuration, the moving operation of the objective lens holder 2 (movable part) in the optical axis direction is controlled by controlling the energization from the coil end (not shown) of the drive coil 10. In addition, by controlling the energization to each piezo element 6a etc. and tilting the holder case 4 according to the tilt due to warping of the disk or substrate, etc., the optical axis perpendicular to the upper surface of the reference base 5 can be adjusted. The optical axis of the objective lens holder 2 can be tilted at a predetermined angle in any direction within a plane perpendicular to the optical axis (tilt operation). For example, in Figure 5 (
When there is no need to drive the piezoelectric elements 6a, 6b, 6c, and 6d shown in a), that is, when the optical axis (two-dot chain line) is perpendicular to the surface of the disk or substrate 23 (the one-dot chain line is the rotation axis). On the other hand, as shown in FIG. 6(b), even if the disk (or substrate) 23 has a slight warp (inclination), the elements 6a etc. are driven according to the degree of inclination, and the holder case 4
By tilting, the optical axis of the objective lens 1 can be made substantially perpendicular to the tilted surface of the disk 23.

In this way, the piezo elements 6a, 6b, 6c
, 6d are driven, the support portion 5a of the reference base 5 is deformed within the elastic limit, as shown in FIG. Therefore, it is necessary to use a material having predetermined elasticity and rigidity as the reference base 5. In addition, piezo elements 6a and 6b
, 6c, and 6d can generate a much larger force than the driving force when using a coil, so the elastic constant of the support portion 5a is made high (rigidity is made high).
It is possible to operate even if Therefore, even if secondary resonance occurs in the operation in the optical axis direction, it is possible to achieve a very high frequency range.

0012

[Effects of the Invention] As explained above, according to the present invention, in order to support the holder case of the objective lens holder,
The objective lens holder is supported on the reference base with point contact by using V-shaped grooves and steel balls without using springs, etc.
Since the piezo element is driven to tilt the objective lens holder according to the inclination of the disk, even if secondary resonance occurs in the operation in the optical axis direction, it is possible to operate in a very high frequency range, which is different from conventional methods. Since the occurrence of secondary resonance due to insufficient rigidity of the movable part can be prevented, the accuracy of control in the focus direction can be improved.

Furthermore, since the holder case is supported by point contact using steel balls, it is possible to prevent external vibrations etc. from being transmitted to the objective lens holder as much as possible and to reduce the influence of disturbances. Control accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an objective lens actuator showing an embodiment of the present invention.

FIG. 2 is a top view of the objective lens actuator of the present invention.

FIG. 3 is a sectional view taken along line A-A' in FIG. 2;

FIG. 4 is a sectional view taken along line B-B' in FIG. 2;

FIG. 5 is an explanatory diagram showing tilt control of the holder case according to the tilt of the disk (or substrate).

FIG. 6 is an explanatory diagram showing deformation within the elastic limit of the support portion of the reference base.

FIG. 7 is a perspective view showing a conventional objective lens actuator.

[Explanation of symbols]

1 Objective lens 2 Objective lens holder 4 Reference base 4a Holder case 5 Reference base 5a Support portions 5b, 4b, 4c V-shaped grooves 6a, 6b, 6c, 6d Piezo element 13
wrecking ball

Claims (1)

[Claims] 1. An objective lens actuator, which is incorporated in an optical head for reproducing or recording information on an optical disk, and has an objective lens holder attached with an objective lens and a focusing coil, A holder case that is movable in the optical axis direction by energizing a focusing coil and has a plurality of locking parts at the end of the opposite side of the objective lens; It consists of a plurality of L-shaped support parts having a predetermined elasticity that are supported in a pinching manner, and a reference base having a piezo element provided near the support parts, and the optical axis of the locking part and the support part V on each opposing surface in the direction and the position where the piezo element of the locking part faces each other.
A steel ball is arranged between the V-shaped grooves so that the holder case and the reference base are in point contact, and by energizing the piezoelectric element, the tilt of the optical disc surface is adjusted. The objective lens actuator is characterized in that the holder case is inclined so that the optical axis is substantially perpendicular to the inclined surface thereof.