JPS5864649A - Driving device for objective lens - Google Patents

Abstract

PURPOSE:To simplify the structure by supporting the holder contg. coils for driving an objective lens by means of flat springs which are flexible in 2 directions meeting at right angles to each other. CONSTITUTION:An objective lens 7 is fixed on a holder 8 and the holder 8 is supported by means of flat springs 11-14. The flat springs 11-14 have rectangular faces 11a-14a formed at the central parts and faces 11b-14b, 11c-14c meeting at right angles to the faces 11a-14a at both ends of the faces 11a-14a.

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 on which a high-density digital signal is recorded on a disc-shaped recording medium. The present invention relates to an objective lens driving device 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 with respect to a signal on an information track.

More specifically, for example, tracking control corrects the amount of eccentricity of the information track with respect to the center of rotation of the disk, that is, the relative positional deviation in the radial direction of the disk, and the correction of the eccentricity of the information track relative to the center of rotation of the disk, and the correction of the eccentricity of the information track relative to the center of rotation of the disk. This method performs time correction, that is, jitter control, which is necessary when reproducing a disk based on the distance between the objective lens and the information track position, with respect to the vibration of the disk surface.

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.

This involves recording encoded video signals, audio signals, and various information on a disk as information tracks.
While this disk is rotating at high speed, light emitted from a light source such as a laser beam is focused on an information track on the disk, and the original recorded information is reproduced by reading the reflected light from the disk surface. be.

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 tracks are extremely small, in order to faithfully reproduce this high-density information, the convergence diameter of the optical spot for reading must also be extremely small. In order to accurately follow the optical spot with respect to the track, there is a problem in that the objective lens must be accurately driven and controlled so as to avoid positional deviation relative to the disk.

In order to solve this problem, conventional techniques 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.

As an example, there 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 disadvantage that a certain inclination angle always occurs in the optical axis within the objective lens, which prevents highly accurate reproduction.

As another example, the objective lens or its storage 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 the elastic support member, the objective lens, and the drive device for tracking control is supported by another elastic support member, and this is connected to the drive device for focus control (for example, the voice 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 a coil (equivalent to a coil). However, this method has problems in that tracking control and focus control are performed by separate electromagnetic devices, resulting in a complicated configuration, increased weight, and poor response at high frequencies. Moreover, since the objective lens is provided with an elastic member for tracking control and is driven in the focus direction including this elastic member, if the lens and the elastic member are driven in the focus direction with the elastic member tilted in the tracking direction, There is a fatal problem in that the elastic action of the elastic member causes a time lag in the movement of the lens in the focus direction, making accurate focus control impossible.

The present invention eliminates these drawbacks, allows for more precise control of the objective lens in the tracking and focusing directions, and furthermore allows the objective lens to be controlled at 9 degrees to both the tracking and focusing directions, i.e. For example, it is possible to perform time correction, that is, jitter control, required for video disc playback in the connection direction of the information track, and to improve the linearity of the operation in either direction.
The object of the present invention is to provide an objective lens driving device that has good linearity, has a simple structure, and is lightweight.

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

FIG. 1 shows a principle diagram of how to obtain the driving force for driving the objective lens of the present invention. Two permanent magnets 1 and 2 are placed on the same axis with a certain space between them, as shown in Figure 1, and are magnetized in opposite directions on the same axis, with the two same poles facing each other. . Therefore, a common magnetic field is generated in the space between the two opposing permanent magnets 1 and 2. Three axes, the T-axis, F-axis, and Z-axis shown in FIG. 1, are perpendicular to each other, and here the Z-axis is the direction in which the two permanent magnets 1 and 20 are magnetized. The intersection of the three axes is the two permanent magnets 1,
It is assumed that it is at the midpoint between two opposing spaces 1. A coil winding frame 3 is supported within this space so as to be movable in any direction in the T, F, and Z directions (the support structure is not shown in FIG. 1). At the outer periphery, F
A first coil 4 is wound in parallel in the −2 plane, a second coil rs is wound in parallel in the Z-T plane, and a third coil 6 is wound in the T-F plane.

It is assumed that each coil has a rectangular shape.

Now, when a current flows in the direction of the arrow in the first coil 4 shown in FIG. 1, the coil winding frame 3 moves in the direction of the arrow on the T-axis due to the electromagnetic action between the first coil 4 and the permanent magnets 1 and 20. Similarly, when a current is passed through the second coil 6 in the direction of the arrow, the coil winding frame 3 moves in the direction of the arrow on the F-axis, and when a current is passed through the third coil 6 in the direction of the arrow, the coil winding moves in the direction of the arrow on the Z-axis. Of course, if the direction of current flow is reversed, the direction of movement of the coil winding frame 3 will also be reversed. That is, when current is supplied to each of the three coils wound in directions perpendicular to each other within one common magnetic field, the coil winding frame 3 receives a driving force and moves in a predetermined direction.

Next, specific examples of the present invention will be shown. A first embodiment of the present invention is shown in FIGS. 2 to 6.

This first embodiment shows an objective lens driving device that controls the objective lens in two directions, the tracking direction and the focusing direction. The objective lens 7 is fixed to a holder 8 which also serves as a coil winding frame, and the holder 8 has a hole 8a through which the optical path from the objective lens 7 passes. - on the outer periphery of the holder 8 indicates the focus direction (F direction)
A tracking control coil 9 is wound in a rectangular shape parallel to the T direction, and a focus control coil 10 is wound in a rectangular shape parallel to the tracking direction (T direction). On both upper and lower sides of the holder 8, conductive plate springs 11 and 12 made of metal or the like are installed to restrict movement in the tracking direction and the focus direction.
13.14 is fixed at one end, and each leaf spring 11.
The other ends of 12, 13, and 140 are fixed to the support 16. This support 15 is fixed to a base 16. This allows the objective lens 7 to be supported so as to be movable in any direction of the T direction and the F direction.

On the other hand, permanent magnets 17 and 18 are arranged so that a constant air gap is formed with respect to the holder 8 in the front-rear direction, that is, in the direction perpendicular to the F-T plane, around which the control coils 9 and 10 are wound. It is fixed to the base 16.

The magnetization directions of these permanent magnets 17 and 180 are shown in FIG.

As shown in Figure 3, they are coaxial and in opposite directions.

Here, a detailed explanation of the operation of the leaf springs 11, 12, 13, and 14 will be given.

FIG. 4 is a top view of the above embodiment, and FIG. 6 is a side view of the same. As mentioned above, mutually independent leaf springs 11, 12, 1
One end of 3, 14 is fixed to the holder 8 and the other end to the support 16, and these leaf springs 11, 12, 13, 14
As shown in FIGS. 3 to 5, the strip-shaped first surfaces 11+a, 122L, 131L, 142 are formed in the center.
L has second surfaces 11b, 12b, 13b, and 14b that are perpendicular to the first surfaces 11a to 141L at both ends in the longitudinal direction. The vicinity of both ends of the first surfaces 11a to 141L and the first surfaces 1111 to 141 of the second surfaces 11b to 14b
Through-holes 11C to 140 are provided in a portion close to 141L, respectively, so that this portion is weakened and can be bent around this portion.

In this way, in FIG. 4, when receiving a driving force in the T direction, each bent portion (first surface 111L
The objective lens 8 moves in the T direction parallel to the width of the support body 142L with the bent portions near both ends of 142L (portions indicated by arrows in FIG. 4) as fulcrums.

In addition, in FIG. 6, if a driving force in the direction F is now received, the arrows in FIG. The objective lens 8 is mounted on the support 1 with the part shown in ) as a fulcrum.
Translate in parallel to 6 in the F direction.

Therefore, if such leaf springs 11 to 14 are used,
Objective lenses 8t and 8I are formed in the tracking direction and the focus direction while maintaining a parallel relationship with each other.

In this way, according to the above embodiment, by arranging two independent coils integrated with the objective lens in one common magnetic field and applying current to these coils, the objective lens can be directly Therefore, when the tracking support spring is tilted, as in conventional focus control that is controlled via a tracking support spring, there is a problem that a phase shift occurs with respect to the focus control signal. In addition, since there are only two independent coils for control and no yoke system, the linearity of the operation is good, and if the permanent magnet and coil dimensions are set appropriately, the necessary movement can be achieved. The range is also extremely wide.The structure is lightweight and extremely simple, so the response speed is 9. Frequency characteristics are 1.
Main characteristics such as phase characteristics and drive efficiency are greatly improved.

By the way, since this embodiment is a moving coil type objective lens drive device, lead wires are required to supply control current to each coil 9 and 10, but in this embodiment, in order to prevent abnormal resonance of the lead wires, The four leaf springs 11, 12
, 13 and 14 are shared as lead wires. That is, as shown in FIG. 2, the end of each coil 9.10 is connected to one end of the leaf springs 11.12, 13.14, the lead wire 24 for applying a control current is connected to the other end, and the leaf spring is 11,12゜13.
14 is used as one end of the lead wire.

In this way, even though it is a moving coil type, the leaf spring can also be used as a lead wire for applying control current, so there is no resonance abnormality in the lead wire.Next, a second embodiment of the present invention will be explained with reference to FIGS. 6 and 7.

This second embodiment adds one-way jitter control when used for video discs, and parts having the same functions as those of the first embodiment shown in Figs. 2 to 5 are given the same reference numerals. The explanation will be omitted, and the explanation will focus on the parts that are different from the first embodiment.

A tracking control coil 9 and a focus control coil 1o are wound around a holder 8 that holds an objective lens 7, as in the third embodiment, and a jitter control coil 19 is also wound in parallel to the F-plane. is wrapped. One ends of the plates 11, 12, 13.degree. 14 are fixed to the holder 8, and their other ends are fixed parallel to each other in the vertical direction of the intermediate support 20, which is lightweight and rigid. One end of the parallel springs 21 and 22 is fixed to two surfaces parallel to the front-rear direction of the intermediate support 2°, that is, the F-T plane, and the other end thereof is fixed to the support 23. Note that this support 23
is fixed to the base 16.

In this way, the objective lens 7 can be adjusted to F, T, in FIG.
The optical axis is supported so that it can move in any direction without tilting in the three Z directions that are perpendicular to each other. Then, in the same way as in the first embodiment, by applying a correction signal current to these three independent coils 9, 10.19 within one common magnetic field between the permanent magnets 17.18,
It is possible to correct tracking, focus, and jitter in each direction.

Since the structure is simple and based on a lightweight support structure, various performances such as response speed, frequency characteristics, phase characteristics, and linearity are improved, and the objective lens can be tracked without being affected by the elastic support. It can be directly driven in three directions: , focus, and jitter.

In the above embodiment, the leaf springs 11, 12, 13 and 14 are made of a conductive material and used as lead wires, but they do not necessarily have to be made of a conductive material, and may be made of, for example, resin. It may also be made of a non-conductive flexible material. In addition, if the leaf springs 11.12, 13.14 are not used as lead wires, each leaf spring 11.12, 13.
．． 14 need not be formed separately; for example, two opposing sides of a frame-shaped plate spring may be used as a pair of parallel plate springs. Moreover, when configuring the bent portions in the leaf springs 11 to 14, it is not always necessary to provide the through holes 11c to 14C, and for example, V-shaped cuts may be made. Furthermore, in the above embodiment, a movable coil type objective lens drive device was described, but a movable magnet type objective lens drive device as shown in Patent Application No. 109883 of 1983 and Patent Application No. 109884 of 1988 It can also be applied to devices.

As described above, the present invention has a rectangular first surface formed in the center, and second surfaces formed at both ends of the first surface in the longitudinal direction so as to be perpendicular to the first surface. and the vicinity of both ends of the first surface and the first surface of the second surface.
The objective lens is supported by a plurality of pairs of mutually parallel leaf springs whose ends near the surface of Since it is designed to move in at least two axial directions with respect to the information track of the recording medium, the structure itself can be made simple and lightweight, and therefore the response speed is 1 frequency characteristic.

It is possible to significantly improve phase characteristics, drive efficiency, and other initial characteristics.

[Brief explanation of the drawing]

Fig. 1 is a perspective view for explaining the present invention in detail, Figs. 2 and 3 are perspective views and exploded perspective views of the first embodiment of the invention, and Figs. 4 and 6 are illustrations of the above embodiment. A top view and a side view of the main parts of the example, and FIGS. 6 and 7 are a perspective view and an exploded perspective view of the second embodiment of the present invention. ...Holding body, 9
．． 1 o. 19... Coil, 11, 12, 13.14...
Curved/plate spring, 15.23...Fixed support, 16
...Base, 17.18 ...Permanent magnet,
20... Intermediate support, 21.22...
Parallel spring, 24...Lead wire. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) An objective lens that is disposed opposite to an encoded information track provided on a disk-shaped recording medium and projects a reading light spot onto the information track, and the objective lens is connected to the information track. supporting means movably in at least two axial directions orthogonal to each other, one end of which is fixed to the objective lens or a holder for holding it, and the other end of which is fixed to a fixed support. It is composed of a plurality of pairs of plate springs that are fixed and parallel to each other. and a second surface formed perpendicular to the surface, and the vicinity of both ends of the first surface and the end of the second surface close to the first surface are bendable. An objective lens driving device characterized by comprising: A through hole is formed at each end near the surface of the lens drive device. −