JPS5864648A - Driving device for objective lens - Google Patents

Abstract

PURPOSE:To control the positions of coils wound at right angles to one another in the direction of 3 axes by simple structure by applying a magnetic field to the coils from 2 magnets arranged on the same axis. CONSTITUTION:Permanent magnets 1, 2 arranged on the same axis with a certain space in-between are magnetized in the reverse directions on the same axis so that the 2 same poles face to each other. When an electric current is supplied to a coil 4 in the arrow direction, the coil winding frame 3 moves in the arrow direction of T-axis. Similarly, a coil 5 takes part in movement in the direction of F-axis, and a coil 6 takes part in movement in the direction of Z-axis.

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 warping of the disk itself and the relative displacement caused by the rotational movement of the disk. It performs focus control to control the distance between the objective lens and the information track position in response to disc surface shake, and also performs time correction, ie, jitter control, which is necessary when playing a video disc.

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 precision, 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 focusing diameter of the optical spot for reading must also be extremely small. In order to cause the light spot to accurately follow the information track, there is a problem in that the objective lens must be accurately driven and controlled so as to prevent relative positional deviation from 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.

For 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, 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 (5-1), which includes a 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 drive device commonly used for 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 a voice coil (equivalent to a voice coil). However, in this method, the tracking control and focus control are performed by separate electromagnetic devices, making the configuration complicated.
There is also a problem that the weight increases and the response at high frequencies deteriorates. 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 and allows for more precise control of the objective lens for the tracking direction and focus direction, and also for the trough 67 - either for the king direction or the focus direction. 90
For example, it is possible to perform time correction or jitter control necessary for video disc playback even in the tangential direction of the information track, and to improve the linearity of the operation in either direction. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below 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 Ta2 axis and the Z axis, shown in FIG. 1 are perpendicular to each other, and here the Z axis is the magnetization direction of the two permanent magnets 1 and 2. The intersection of the three axes is the two permanent magnets 1 and 2.
It is assumed that it is at the midpoint of the opposing space. A coil winding frame 3 is supported within this space so as to be movable in any direction in each of the T, F, and Z directions (the support structure is not shown in FIG. 1). At the outer periphery of the frame 3, a first coil 4, Z-
A second coil 6 is wound in parallel in the T plane, and a third coil 6 is wound in the T-F plane. Note that each coil is assumed to have 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 magnet 1t2. Similarly, when a current is passed through the second coil 5 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. Frame 3 moves.

Of course, if the direction of current flow is reversed, the moving direction 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 tenth embodiment of the present invention is shown in FIGS. 2 to 5.

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 section 8a through which the optical path from the objective lens 7 passes. A tracking control coil 9 is wound around the outer periphery of the holder 8 in parallel to the focus direction (F 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 leaf springs 11, 12+ made of metal etc. are attached 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 12t, 13° and 14 are fixed to the support body 15. This support 16 is fixed to a base 16.

Thereby, the objective lens 7 is 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 fixed to the base 16 so that a constant air gap is formed with respect to the holding body 8 around which the control coils 9 and 1o are wound.

These permanent magnets 17 and 180 are magnetized in opposite directions on the same axis as shown in FIG. 21 and FIG.

Here, details of the operation of the leaf springs 11, 12, 13, and 14 will be described.

FIG. 4 is a top view of the above embodiment, and FIG. 5 is a side view of the same. As mentioned above, the leaf springs 11+12 are independent of each other.
One end of t 13, 14 is connected to the holder 8, the other end is connected to the support 1
5, these leaf springs 11, 129
13914 is a rectangular first surface 112L*12a+1 formed in the center as shown in FIGS. 3 to 5.
3at 14a at both ends in the longitudinal direction, the first surface 111L
~Second surface 11b, 12b, 1 perpendicular to 141L
3b and 14b.

Then, through holes 11C to 14C are provided near both ends of the first surfaces 111L to 14gL and in portions of the second surfaces 11b to 14b close to the first surfaces 11a to 14a, respectively, to weaken these portions. If you bend to the center like this, the fourth
In the figure, if a driving force is now applied in the T direction, each bending part (the bending part near both ends of the first surfaces 11a to 14N and the part indicated by the arrow in FIG. 4) is used as a fulcrum. , when the objective lens 8 is moved in the T direction parallel to the support 15 and receives a driving force in the F direction in FIG. 1 side 1
The objective lens 8 is moved parallel to the support body 15 in the F direction using the bent portion near 1a to 14a- (the portion indicated by the arrow in FIG. 5) as a fulcrum.

Therefore, by using such leaf springs 11 to 14, it is possible to move the objective lens 8 in the tracking direction and the focus direction without giving an inclination angle to the optical axis while maintaining a parallel relationship with each other.

In this way, according to the above embodiment, two independent coils integrated with the objective lens are arranged in one common magnet W, and the objective lens is changed by applying current to these coils. Can be driven directly. Therefore, there is no problem that a phase shift occurs with respect to the focus control signal when the tracking support spring is tilted, which is the case with conventional focus control that is controlled via the tracking support spring.

In addition, since only two independent coils are provided for control and there is no yoke system, the linearity of the operation is good, and if the permanent magnet and coil dimensions are set appropriately, the required range of motion is extremely large. It can be taken widely. Furthermore, since the structure is lightweight and extremely simple, the response speed, frequency characteristics, phase characteristics, drive efficiency, and other characteristics 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+
1'2s 13+14 are shared as lead wires. That is, as shown in FIG. 2, leaf springs 11t 12t
The end of each coil 9.1o is connected to one end of 13 and 14 degrees, and the lead wire 24 for applying a control current is connected to the other end, and the leaf springs 11 and 12 degrees and 13 and 14 are used as part of the lead wire. We are using.

In this way, even though it is a moving coil type, the plate spring can also be used as a lead wire for applying a control current, so there will be no resonance abnormality in the lead wire.

Next, a second embodiment of the present invention will be described 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 1 are mounted on a holder 8 having an objective lens 7, as in the first embodiment.
A jitter control coil 19 is further wound in parallel within the F-7 plane. And leaf spring 1
One end of 1, 12, 13° 14 is fixed to the holder 8, and the other end is attached to two surfaces parallel to the front-rear direction of the up-down direction 2o, that is, the F-T plane of the lightweight and rigid intermediate support 2o. One end of the parallel springs 211 and 22 is fixed to the support body 23, and the other end thereof is fixed to the support body 23. Note that this support 23 is fixed to the base 16.

In this way, the objective lens 7 becomes F in FIG.

The optical axis is supported so that it can move in any direction without tilting with respect to the T and Z directions that are perpendicular to each other. Then, in the same manner 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, tracking, \ focus , jitter can be corrected in each direction.0 According to the second embodiment, like the first embodiment, the structure is simple and is based on a lightweight support structure, so the response speed can be improved. , various performances such as frequency characteristics, phase characteristics, and linearity have been improved, and the objective lens can be directly driven in the three directions of tracking, focus, and jitter without being affected by an elastic support. can.

In the above embodiment, the through holes 110 to 140 are provided when forming the bent portions of the leaf springs 11 to 14, but V-shaped cuts or the like may be provided instead of the through holes.

As described above, the present invention includes winding at least two independent coils in directions perpendicular to each other on a holder integrated with an objective lens, and a permanent magnet with a predetermined space in the vicinity thereof. The objective lens is driven in at least two axial directions perpendicular to each other by the current flowing through the coil and the electromagnetic action of the permanent magnet. Therefore, when the tracking support spring is tilted, as in conventional focus control that is controlled via a tracking support spring, a phase shift will occur with respect to the focus control signal. You can eliminate all problems. Moreover, since only two or three coils are provided for control and there is no yoke system, the linearity of operation is 15.

If you set the dimensions of the permanent magnet and coil appropriately,
The required range of motion can also be extremely wide.

[Brief explanation of drawings]

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 5 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
, 10° 19... Coil, 11, 12, 13.
14...Plate spring, 15123...Fixed support, 16...Base, 17.18...
・Permanent magnet, 2o...Intermediate support, 21.22
...Parallel spring, 24...Lead wire. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure 1 Figure 5 Figure 6

Claims (1)

[Claims] (1) An objective lens that is movably arranged opposite to an encoded information track provided on a disk-shaped recording medium and projects a reading light spot onto the information track; a permanent magnet disposed with a predetermined space therebetween; and at least two mutually independent coils wound in directions perpendicular to each other around a holder integrated with the objective lens; An objective lens driving device characterized in that the objective lens is driven in at least two mutually orthogonal axes directions by a current flowing through the magnet and an electromagnetic action of the permanent magnet. ? ) The objective lens according to claim 1, wherein the objective lens is movably supported using a conductive leaf spring, and the leaf spring is used as a lead wire for energizing the coil. Drive device.