JPH0145143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a reproducing apparatus that optically reads information by projecting a light spot onto an information track in which a high-density digital signal is recorded on a disc-shaped recording medium. This invention relates to a movable body holding device that can be used in an objective lens drive device, etc. that controls the position of an objective lens relative to a disk surface in order to accurately correct and control the position of a light spot in response to an information track signal. be.

For more details, apply to this type of playback device,
For example, tracking control corrects the eccentricity of the information track with respect to the rotation center of the disk, that is, the relative positional deviation of the disk in the radial direction, the warpage of the disk itself, and the relative deflection of the disk surface that occurs due to the rotational movement of the disk. Focus control is performed to control the distance between the objective lens and the information track position.

Generally, this type of optical information reading device is used in video discs that record video signals and digital audio discs that record encoded audio signals, as well as other high-density information recording and reproducing devices such as those related to computers. It is applied.

In this system, coded video signals, audio signals, and various other information are recorded as information tracks on a disk, and while the disk is rotating at high speed, light emitted from a light source such as a Reger beam is transferred to the disk. By focusing the light on the upper information track and reading the reflected light from the disk surface, the original recorded information is reproduced.

This optical information reading device can record information at an extremely high density, and has the advantage of being able to record information at a higher density, with higher accuracy, and with higher performance than conventional analog systems.

On the other hand, since the width and pitch of the information track are extremely small, in order to faithfully reproduce this high-density information, the focusing diameter of the light spot for reading must also be extremely small. There is a problem in that the light spot must be accurately driven with respect to the information track of the disk and controlled so as not to cause a relative positional shift with respect to the disk.

In order to solve this problem, conventional methods have been used to electrically detect the reflected light from the disk surface and control the reading light spot position to match the information track position.

One example is a method in which a rotatable mirror is placed in the optical path between the laser light source and the objective lens, and the mirror is rotated and controlled based on the information of the tracking error signal. However, this method has the drawback that a certain inclination angle always occurs in the optical axis within the objective lens, and highly accurate reproduction cannot be expected.

As another example, the objective lens or its holding frame is supported by an elastic support member made of a leaf spring, and tracking control is performed by displacing the objective lens parallel to the disk surface according to a tracking error signal. The entire device including an elastic support member, an objective lens, and a drive device for tracking control is supported by another elastic support member, and this is connected to a drive device for focus control (for example, a voice coil commonly used in speakers). A method has been proposed in which the focus is controlled by driving the objective lens in a direction perpendicular to the disk surface using an equivalent lens. However, in this method, tracking control and focus control are performed by separate electromagnetic devices, so the structure becomes complicated, the weight increases, and the response at high frequencies deteriorates. Moreover, the objective lens is provided with an elastic member for tracking control, and since the elastic member including this elastic member is driven in the focus direction, when the elastic member is inclined in the tracking direction, the elastic action of the objective lens and the elastic member is used. There is a problem in that a temporal and phase shift occurs in the movement of the lens in the focus direction, making accurate focus control impossible.

The present invention eliminates these drawbacks, allows for more accurate control of the objective lens in both the tracking direction and the focus direction, and has good linearity of operation in both directions. To provide an objective lens holding device that has a simple structure and is lightweight.

Hereinafter, details of the present invention will be explained with reference to the drawings.

FIG. 1 illustrates the principle of the invention. Two permanent magnets 1 and 2 coaxially arranged with a certain space between them are magnetized in opposite directions on the same axis as shown in Fig. 1, and a magnetic material formed in a U-shape. The yokes 3 and 4 each form a magnetic gap. On the other hand, coils 5 and 6 are wound around the movable part so as to cross each other at a certain angle. The two magnetic gaps mentioned above are arranged symmetrically with respect to the area where the two coils 5 and 6 cross. FIG. 2 is a diagram illustrating the direction of the driving force. For simplicity, only one direction in which the coils are in a crossed state will be explained. If a current is passed in a certain direction through the coils 5 and 6, forces will be generated in the directions of vectors a→ and b→, and the resultant force will be V→. Further, when only the direction of the current in the coil 5 is reversed, the combined vector becomes H→ due to the vector c→ caused by the coil 5 and the vector b→ caused by the coil 6. That is, by controlling the direction of the current flowing through the coils 5 and 6, it is possible to move the movable part in any vertical or horizontal direction.

3 and 4 show an embodiment of the present invention, in which the objective lens holding device of the present invention is applied to a two-dimensional objective lens driving device in the tracking direction and the focus direction.

An objective lens 7 through which an optical signal passes is fixed in a center hole 8a of a holding member 8 which also serves as a coil winding frame. The holding member 8 is made of a lightweight and strong material, such as a light metal such as aluminum or magnesium, or a reinforced plastic containing a reinforcing agent such as carbon wire or glass, and is supported as shown in FIG. It has protrusions 9 and 10 for coupling with other members. Two coils 5 and 6 are wound symmetrically around the outer circumferential portion of the holding member 8 so as to surround the optical axis of the objective lens 7 and avoid the optical axis at a certain angle to each other.

Support members 11 and 12 for regulating two-dimensional movement are coupled to the distal ends of the coupling protrusions 9 and 10.

The support member 11 includes a parallelogram frame-shaped body consisting of a pair of elastic surfaces 13 and 14 and a pair of rigid surfaces 15 and 16, a pair of elastic surfaces 17 and 18, and a pair of rigid surfaces 1.
It is composed of a parallelogram frame-shaped body consisting of 5 and 19 pieces connected together. The support member 12 is similarly configured. That is, these supporting members 1
1 and 12 are adjacent elastic surfaces 13 and 17 and 1
It consists of two springs formed so that the angles 4 and 18 are at approximately 90 degrees.

These support members 11, 12 have rigid surfaces 16,
16 to the coupling protrusions 9 and 10 of the holding member 8, and by fixing the rigid surfaces 19 and 19 to the outer case 21, the holding member 8 is movably supported within the outer case 21. At this time, the coupling protrusions 9, 1
0, two protrusions 9a, 9a, 10a,
10a, two holes 16a, 16a are provided in each of the rigid surfaces 16, 16 of the supporting members 11, 12, and with the protrusions 9a, 10a inserted into the holes 16a of the rigid body 16, they are fixed together. Then, the mounting angle of the support members 11, 12 can be accurately regulated by the engagement between the protrusions 9a, 10a and the hole 16a.

The magnetic circuit consists of a U-shaped yoke 2 made of magnetic material.
At one end 22a, 23a of 2, 23, there are magnets 24, which are coaxial and magnetized in opposite directions, as shown in FIG.
25 and the other end 22 of the yokes 22 and 23
b, 23b are loosely fitted into the through holes 8b, 8b of the holding member 8, and the magnets 24, 25 are inserted into the coils 5, 6.
The yokes 22 and 23 are fixed to the outer case 21 with screws 26 and 27 in this state.

In this way, by passing a predetermined current through the coils 5 and 6, the holding member 8 is driven in the tracking direction and the focusing direction according to the operating principle shown in FIG. At this time, supporting members 11, 12
are rigid surfaces 15, 16, 1 constituting each parallelogram
9 moves in the tracking T direction and the focusing F direction shown in FIG. 3 by the elastic action of the elastic surfaces 13, 14, 17, and 18 while maintaining verticality with respect to the holding member 8 and the outer case 21. Therefore, the holding member 8 can be moved in the two axial directions of tracking T and focusing F using the common supporting members 11 and 12, and therefore the optical axis of the objective lens 7 will not be tilted during the movement.

The support members 11 and 12 are integrally molded from a synthetic resin having high elasticity such as polyimide or polypropylene, and the elastic surfaces 13, 14, 17, and 18 are thin walls, and the rigid surfaces 16 and 19 are thick walls. be able to. Of course, the elastic surfaces 13, 14, 17, 1
8 and the rigid surfaces 16 and 19 may be made of different materials, and these may be bonded with an adhesive, or may be integrated by inserting, outsert, etc. inside a molding die.

Furthermore, although the embodiments shown in FIGS. 3 and 4 are constructed by connecting two parallelogram frame bodies, it may be constructed by connecting three or more parallelogram frame bodies.

Furthermore, in the embodiments shown in FIGS. 3 and 4, in order to downsize the entire device, the support members 11 and 12 are arranged coaxially on the O-O′ axis in FIG.
The holding member 8 may be held between the rigid surfaces 16 and 12.

5, 6, and 7 conceptually show the relationship between the supporting members 11, 12 and the holding member 8 in this case. When the holding member 8 is not driven,
As shown in FIG.
The holding member 8 is positioned at the center in a moderately bent state. When a driving force in the tracking T direction is applied to the holding member 8 in this state, the rigid surface 15 of the supporting member 11 sinks vertically, and the elastic surfaces 13, 1
4, 17, and 18 are bent downward. In addition, in response to this, the rigid surface 15 of the support member 12 is pulled up vertically, and the elastic surfaces 13, 14, 17, and 18 are extended nearly horizontally. This causes the holding member 8 to move in parallel in the tracking T direction. Next, the holding member 8
When a driving force in the focus direction is applied to , the rigid surfaces 15, 15 of the support members 11, 12 are both pulled up in the vertical direction, the elastic surfaces 13, 14 are tilted, and the holding member 8 is moved in parallel in the focus direction F. .
Movement of T and F in the opposite direction is performed in the same manner.

As described above, the present invention configures a support member by connecting a parallelogram-shaped bendable frame body consisting of a pair of elastic surfaces and a pair of rigid surfaces, and supports an objective lens holding member with this support member. As a result, it is possible to improve the linearity of the movement of the objective lens holding member, and it is also possible to obtain excellent effects such as a simple structure and a reduction in weight.

[Brief explanation of drawings]

1 and 2 are an exploded perspective view and an operation explanatory diagram showing the principle of the present invention, FIGS. 3 and 4 are a fragmentary perspective view and an exploded perspective view of essential parts of an embodiment of the present invention, and FIG.
7 to 7 are conceptual diagrams for explaining the operation of the embodiment of the present invention, and FIGS. 8 and 9 are transfer characteristic diagrams of the embodiment of the present invention. 5, 6... Coil, 7... Objective lens, 8...
Holding member (movable body), 9, 10... coupling protrusion,
9a, 10a...Protrusion, 11, 12...Support member, 13, 14, 17, 18...Elastic surface, 15,
16, 19... Rigid surface, 16a... Hole, 21...
Outer case, 22, 23... Yoke, 24, 25...
...Magnet.

Claims (1)

[Scope of Claims] 1. A plurality of parallelogram frame-shaped bodies made of a resin material and consisting of a pair of mutually opposing elastic surfaces and a mutually opposing pair of rigid surfaces, the rigid surfaces of which are A support member connected by coupling or sharing, an objective lens holding member attached to a rigid surface at one end of the support member, and a fixing member to which the rigid surface at the other end of the support member is attached, By varying the angle between the elastic surfaces of adjacent frame-shaped bodies,
1. An objective lens holding device for an optical disc playback device, characterized in that the objective lens holding member is held relative to the fixing member so as to be movable in the focusing direction and the tracking direction of the optical disc. 2. An objective lens holding device for an optical disc playback device according to claim 1, wherein the supporting member is attached at a position symmetrical with respect to the center of gravity of the objective lens holding member. 3 A plurality of protrusions are provided on one of the rigid surfaces of the objective lens holding member and a support member attached to the objective lens holding member, and a plurality of holes are provided on the other side, and the protrusions are inserted into the holes. 2. An objective lens holding device for an optical disc playback device according to claim 1, wherein said rigid surface is attached to a movable body. 4. Claim 1, characterized in that the support member is integrally molded from a synthetic resin having high elasticity such as polyimide or polypropylene, and the elastic surface is a thin wall surface and the rigid surface is a thick wall surface. Objective lens holding device for optical disc playback equipment.