JPS5810197Y2 - Objective lens holding device - Google Patents

Description

[Detailed description of the invention] The present invention is an objective lens holder used in a device that uses an objective lens to optically read information from an information carrier recorded at high density by, for example, changes in brightness or phase difference. It is related to the device.

For example, in order to use an optical read head to read information recorded optically at high density, such as on a video disc, precise focusing and tracking are required to accurately track the track containing the information. It is.

Focusing and tracking are adjustments in the amount of movement in the direction parallel to the optical axis of the objective lens, while tracking is adjustment in the amount of movement in the direction perpendicular to the optical axis, so these movements are the same. If an attempt is made to use a mechanical system, the mechanism will become complicated and large, the mass of the objective lens holder will increase, and the frequency characteristics of the response will deteriorate.

In order to solve these drawbacks, the present inventors previously filed a patent application filed in 1973.
In No. 55288, an objective lens holding device for holding an objective lens using a plate-like elastic member was proposed.

That is, such an objective lens holding device includes an objective lens, a holding member that supports the objective lens, and an elastic member each having at least one surface parallel to the optical axis of the objective lens and one or more surfaces perpendicular to the optical axis. an elastic support member disposed on both sides of the optical axis, one end of the elastic support member being attached to a holding member for the objective lens, and the other end being attached to a fixing member provided opposite to the holding member; The present invention is characterized in that the holding member is configured to be movable independently in horizontal and vertical directions with respect to the optical axis together with the objective lens.

Therefore, in this invention, the objective lens is held by a plate-shaped elastic member having a simple shape, and this plate-shaped elastic member can be moved independently in the horizontal and vertical directions with respect to the optical axis of the objective lens. It has the advantage of being easy to align and track.

However, in such an objective lens holding device, when the plate-shaped elastic member is moved horizontally and vertically with respect to the optical axis, the plate-shaped elastic member is also displaced in its width direction due to the difference in spatial stiffness. Therefore, the objective lens is tilted, and focusing and tracking cannot be performed accurately.

In other words, the spatial stiffness of this plate-like elastic member differs in the longitudinal direction (two directions) parallel to the optical axis of the objective lens, the width direction (y direction) orthogonal to these two directions, and the z and y directions, respectively. This occurs because the moment of inertia of each area in the direction (X direction) that is orthogonal and parallel to the trunking direction of the objective lens is different.

Therefore, when performing automatic tracking and automatic focusing by automatically moving this plate-shaped elastic member in the X and Z directions using electromagnets, it is necessary to correct the displacement of this plate-shaped elastic member in the y direction. Since these directions cannot be separated from each other, it becomes particularly difficult to control automatic focus.

The purpose of the present invention is to move the above-mentioned plate-like elastic member in an unnecessary direction (
It is an object of the present invention to provide an objective lens holding device that enables accurate focusing and tracking by regulating displacement in the y direction.

The present invention includes an objective lens and a holding member that holds the objective lens.
An objective lens holding device held on a fixed member by a pair of plate-shaped elastic members arranged symmetrically with respect to the optical axis of the objective lens and each having at least one surface parallel to the optical axis and one or more perpendicular surfaces. A member is provided that is orthogonal to the width direction of the plate-like elastic member and restricts displacement of the plate-like elastic member in the width direction, thereby holding the holding member together with the objective lens in a direction parallel to the optical axis; It is characterized in that it can move independently only in a direction perpendicular to this and also perpendicular to the width direction.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view showing the configuration of an example of an optical reading head to which the objective lens holding device of the present invention is applied. The horizontal and vertical directions can be controlled automatically to enable automatic focusing and tracking.

One or more surfaces parallel to the optical axis of the objective lens 1 and one or more perpendicular surfaces are provided between the holding member 2 made of a magnetic material and the fixing member 3 that support the objective lens (including the objective lens barrel) 1. The plate-like elastic members, here plate springs 4 and 4', are mounted symmetrically across the optical axis of the objective lens 1.

In addition, when attaching the leaf springs 4.4', in this example, the leaf springs 4, 4' are attached to the holding members 2 through the holding plates 5.6, S/, 6/, which support the leaf springs 4, 4' at both ends, respectively.
and attach it to the fixing member 3.

Furthermore, a ring-shaped electromagnet 7 is attached to the fixing member 3, which faces the holding member 2 and surrounds a surface parallel to the optical axis of the plate spring 4゜4'. , and a tracking electromagnet 8 is attached at a position facing the holding member 2.

In the above-described configuration, the present invention includes an objective lens 1;
A plate-shaped or rod-shaped member (in this example, a plate-shaped member) 9 is fixed between the fixing member 3 and the part where the plate springs 4, 4' are attached, which regulates the widthwise displacement of the plate springs 4, 4'. Provided integrally with member 3.

Figure 2 shows the width direction (y direction) of the leaf spring 4 in Figure 1.
2 is a perspective view showing how a plate-like member 9 is attached to regulate the displacement of the plate spring 4, and both ends of the plate spring 4 in the width direction (y direction) are attached to the fixing member 3.
Since the objective lens 1 is in contact with a plate-like member 9 fixedly attached to the plate member 9, its displacement in that direction is restricted. If there is no defocus signal, if this defocus signal is detected and a current proportional to this detection signal is passed through the ring-shaped electromagnet 1, the objective lens 1 will be caused to emit light by the action of the magnetic field created by this electromagnet 7 and the holding member 2 facing it. Move in the axial direction.

Furthermore, when a tracking deviation signal is detected and a current proportional to the detected signal is passed through the tracking electromagnet 8, a direction perpendicular to the optical axis is generated between the electromagnet 8 and the holding member 2 facing it. A force is applied, and this force causes the objective lens 10 to move in a direction perpendicular to the optical axis.

In this way, when moving the objective lens 1 in the optical axis direction (two directions) to perform focusing, or when moving the objective lens 1 in a direction perpendicular to the optical axis (X direction) to perform tracking, the leaf spring Since the displacement of the lenses 4 and 4' in the width direction (y direction) is effectively restricted by the plate member 9, accurate focusing and tracking can be performed without tilting the objective lens 1.

As described above, in this example, since the displacement of the objective lens in extra directions is forcibly restricted by the rod-shaped or plate-shaped member, the objective lens can be precisely moved in the horizontal and vertical directions.

Moreover, since the objective lens holding device of the present invention has a simple and compact structure, the weight of an optical reading head to which this device is applied can be reduced.

Note that the present invention is not limited to the above-mentioned example, and can be modified or changed in many ways.

For example, static pressure can be applied to the portion that restricts displacement in the extra direction (y direction) shown in the above example to reduce wear on that portion 2.

That is, as shown in FIG. 3, a cavity 10 is formed in the fixing member 3.
And nozzles 11, 11' are formed in the width direction of the plate spring 4 attached to this fixed member 3, and these nozzles 11
.

A plate-like member 9 is arranged in the width direction of the plate spring 4 facing the plate member 11'.

Then, by applying static pressure to the plate member 9 through the cavity 10 and the nozzles 11, 11', the width direction of the plate spring 4 (
The displacement in the y direction) is effectively regulated, and no wear occurs in this part.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of an example of an optical reading head using the objective lens holding device of the present invention, FIG. 2 is a perspective view showing the manner in which the plate member according to the present invention is attached, and FIG. FIG. 3 is a side view showing how the is attached. 1...Objective lens, 2...Resuscitation member, 3
...Fixed member, 4,4bi...Plate elastic member (plate spring), 9...Plate member.

Claims (1)

[Claims for Utility Model Registration] An objective lens and a holding member that holds the objective lens are arranged symmetrically with respect to the optical axis of the objective lens. In an objective lens holding device that is held on a fixed member by a pair of plate-like elastic members each having at least one surface parallel to the optical axis and one or more perpendicular surfaces, A member is provided for restricting displacement of the plate-shaped elastic member in the width direction, and thereby the holding member is moved together with the objective lens in a direction parallel to the optical axis, perpendicular thereto, and perpendicular to the width direction. An objective lens holding device characterized in that it can move independently only in certain directions.