JP2001351256A - Drive device for objective lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving device, capable of independently displacing an objective lens holding body in the focusing direction and the tracking direction by removing the influence of an interference mode which displaces simultaneously in both directions of the focusing direction and the tracking direction. SOLUTION: The objective lens drive device is composed of an objective lens 3, optical head 4, rising mirror 5, photodetector 6, adding and subtracting arithmetic circuit 7, focus error signal amplifier 8, tracking error signal amplifier 9, focus control circuit 10, tracking control circuit 11, interference mode compensating circuit 12, focusing direction driving coil 13, tracking direction driving coil 14, coarse positioning mechanism 15 and objective lens holding body 16. The movement of the device, while interfering with the both directions, is reduced by sending signals which offset rocking modes of the objective lens holding body 16 to respective coils with the interference mode compensating circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device incorporated in an optical disc apparatus for recording or reproducing information on or from an optical disc having information recording tracks, and more particularly to an objective lens driving apparatus which forms an optical spot on an information recording surface of the optical disc to form an optical spot on the optical disc. The present invention relates to an objective lens driving device that can move in a vertical direction and a track-crossing direction.

[0002]

2. Description of the Related Art In an optical disk apparatus, an objective lens is held and light condensed by the objective lens is positioned at a desired position in a disk radial direction, and at the same time, is positioned at a desired position in a disk vertical direction. An objective lens driving device that performs tracking and focusing on an information track has been proposed.

In such an objective lens driving device, the objective lens is supported so as to be independently movable in two axes of a tracking direction and a focusing direction, that is, a horizontal direction and a vertical direction of the disk. The deviation amount is optically detected independently, and the control is also performed independently.

[0004] Return light of an optical spot formed on an information recording surface via an objective lens is used to detect the shift amount. In order to just focus on the disk surface, it is general that the return light is processed by a photodetector divided into four by an astigmatism method, a knife edge method, or the like, and focusing is performed.

[0005] In general, tracking positioning to a track serving as a target position uses a shift signal detected by a two-segment photodetector by a three-beam method, a push-pull method, a phase difference detection method, or the like.

However, the signals of the respective deviation amounts detected as described above are processed independently, and input to and controlled by a focus driving coil or a track driving coil which is provided so as to be independently drivable.

However, with the recent increase in information recording density, the track density has also increased, and the accuracy with which the objective lens must be positioned has become extremely high.

From the viewpoint of the above-described focus operation and tracking operation from the viewpoint of accuracy, it cannot be said that the objective lens holder is strictly and independently driven by the signals input to the respective coils. This objective lens holder is
Although it is configured to be driven independently in the focus direction and the track direction, it is known to have a mode in which it is driven while interfering in both directions depending on the support method of the objective lens holder. This has an adverse effect as interference movement in both directions.

The configuration of a conventional objective lens driving device will be described with reference to FIG.

FIG. 17 shows a shaft-sliding type objective lens driving device 1.
11, the objective lens holder 110 slides with respect to a shaft 103 buried in the center of the upper surface of the base made of a magnetic material, and moves the objective lens 101 in the tracking direction by rotating. Is displaced. That is, the objective lens holder 110 is fitted to the shaft 103 and forms the sliding bearing mechanism with the shaft 103.
It is mounted so as to be slidable in the axial direction via the shaft 02 and rotatable around the axis. The objective lens 101 is provided on the upper surface of the objective lens holder 110.

The objective lens holder 110 is also used as a coil bobbin. Objective lens holder 110
A focusing coil 105 for controlling the position in the axial direction and a tracking coil 106 for controlling the position in the direction around the axis are fixed to the outer periphery of.

The magnetic circuit has two inner yokes projecting symmetrically about an axis at a position facing the inner surface of the cylindrical portion of the objective lens holder 110 on the upper surface of the base so as to be fitted into the cylindrical portion in a non-contact manner. Provided. Further, outer yokes 104 and 109 are arranged outside the cylindrical portion so as to face the outer surface of the inner yoke, and are magnetized in the axial direction between the inner and outer yokes 104 and 109 and the upper surface of the base. The permanent magnets 107 and 108 are interposed.

The objective lens driving device thus configured changes the position of the objective lens holder 110 in the Y-axis direction by the electromagnetic force accompanying the energization control of the focusing coil 105, thereby performing focusing control. The position of the objective lens holder 110 is rotated in the X-axis direction by an electromagnetic force accompanying the control of energization of the tracking coil 106, thereby performing tracking control. These energization controls are performed by independent servo systems.

A small plate made of a magnetic material such as an iron piece is disposed around the outer periphery of the objective lens holder 110 to which the tracking coil 106 and the focusing coil 105 are fixed.
The preload is applied in a direction perpendicular to the axial direction of the support shaft 103 so that the objective lens holder 110 slides securely on the support shaft 103 by utilizing the action of the magnetic circuit formed between the support shaft 103 and the support shaft 103. Is occurring.

This preload is required to perform a sliding operation on the support shaft 103. However, the frictional force generated by this preload is reduced by the objective lens holder 11.
This has an adverse effect that makes a minute displacement of 0 impossible.

As described above, the positioning control having a very high frequency band requires an objective lens driving device for linearly displacing nanometers. However, if nonlinear elements such as friction are present, this order of displacement cannot be realized by sliding. In such a shaft-sliding type objective lens driving device, the displacement of this order is realized by the oscillating movement of the objective lens holder 110 about the bearing contact point due to the elastic deformation of the bearing portion 102 or the preload. .

And such an objective lens holder 110
There is a mode in which the objective lens 101 is displaced simultaneously in both directions as an interference mode in both directions of the focus direction and the track direction.

In the conventional shaft-sliding type objective lens driving device, the frequency of the mode may change due to a change in the contact state between the support shaft 103 and the bearing portion 102. Further, there is another problem that the mode shape itself changes and the degree of adverse effects changes depending on the use situation.

Such a change in characteristics is caused by a contact state between the support shaft 103 and the bearing portion 102. This is because the hole shape of the bearing portion 102 of the conventional objective lens driving device is generally substantially circular, and the objective lens holder 110
Is also substantially circular in shape. Since the objective lens holder 110 is manufactured by injection molding, the hole shape of the bearing portion 102 is caused by the shape of a die-cut mold. The outer diameter shape of the support shaft 103 satisfies straightness and is produced at low cost. This is due to the possible shape being a round bar.

However, when the round hole is pressed with a preload in a predetermined direction against the round bar by fitting the round bar into the round hole as described above, the round hole is inserted into the round hole. It was clear that the contact position and the contact state when rotated were greatly changed.

From the viewpoint of positioning control, the adverse effects of these swing modes are observed as phase disturbances in the frequency response of the focus drive characteristic or the track drive characteristic of the objective lens driving device. If the phase is significantly delayed in this phase characteristic, the phase margin of the positioning control may be reduced to be unstable, and the gain may be raised even if the phase advances, resulting in a gain margin depending on the frequency of the oscillation mode. Could disappear and become unstable.

FIG. 19 shows the track driving control when the swing mode having the frequency characteristic as shown in FIG. 18 exists. In this case, it can be said that there is an adverse effect of reducing the phase margin by acting to delay the phase.

The frequency of the swing mode is determined by the bearing 102
Is determined depending on the material characteristics of the
Specifically, it was present in a frequency region near a control band provided at about 3 to 5 kHz.

In an objective lens driving device other than the shaft sliding type objective lens driving device, a wire 11 as shown in FIG.
Even when the objective lens 101 and the like are supported by 2, there is a mode in which the lens swings around the vicinity of the support point supported by the wire when performing minute displacement. Since this swing mode has the same effect as the above-described shaft-sliding type objective lens driving device on the positioning control system of the objective lens 101, suppression of the swing mode is a problem regardless of the objective lens driving device. Was.

[0025]

As described above, in the conventional objective lens driving device, since the focus direction and the track direction are controlled completely independently, when the recording density is improved, each direction is controlled. Therefore, it was not possible to suppress the adverse effects due to the interference of the objective lens, and to improve the positioning accuracy of the objective lens.

In view of the above, the present invention has been made in view of the above-mentioned conventional problems. In controlling the focus direction and the track direction over a wider frequency band, the present invention provides an objective lens holder and an objective lens holder. Objective lens driving device that can achieve high-precision positioning operation even when recording density is improved by controlling the positioning of the objective lens regardless of the state of contact with the supporting shaft and including interference components from different directions. The purpose is to provide.

[0027]

In order to achieve the above object, an objective lens driving apparatus according to the present invention comprises an objective lens, an optical axis direction of light incident on the objective lens while holding the objective lens, and an optical axis. An objective lens holder supported so as to be drivable in one direction perpendicular to the axis, a focusing coil for driving the objective lens holder in the optical axis direction, and an objective lens holder perpendicular to the optical axis. A tracking coil for driving in the direction, a magnetic circuit formed by each of the focusing coil and the tracking coil, focus detection means for detecting displacement of the objective lens holder in the optical axis direction, and the objective lens holder A track detection means for detecting a displacement in a direction perpendicular to the optical axis direction, and a detection signal detected by the focus detection means. A focus control device for outputting a result obtained by arithmetically processing the detection signal to the focusing coil and the tracking coil; a detection signal detected by the track detection means being input; And a track control device for outputting the result to the tracking coil.

Next, the objective lens driving device according to the present invention is capable of driving the objective lens in the optical axis direction of light incident on the objective lens while holding the objective lens and in one direction perpendicular to the optical axis. A supported objective lens holder, a focusing coil for driving the objective lens holder in the optical axis direction, and a tracking coil for driving the objective lens holder in a direction perpendicular to the optical axis, A magnetic circuit formed by each of the focusing coil and the tracking coil; focus detection means for detecting displacement of the objective lens holder in the optical axis direction; and a focus detection unit for detecting a displacement of the objective lens holder in a direction perpendicular to the optical axis direction. A track detection means for detecting displacement, and a detection signal detected by the focus detection means, which are input and obtained by arithmetically processing the detection signal. A focus control device that outputs a result to the focusing coil; and a track control that receives a detection signal detected by the track detection unit and outputs a result obtained by arithmetically processing the detection signal to the tracking coil and the focusing coil. And a device.

According to such a configuration, the influence of the interference mode which occurs simultaneously in both the focus direction and the track direction is removed, and the objective lens holder is controlled to be displaced independently in the focus direction and the track direction. By doing so, even when the objective lens is displaced in the tracking direction and the focusing direction, disturbance such as frictional force generated due to the contact state between the objective lens holder and the support shaft that supports the objective lens holder. A uniform driving characteristic can be obtained without greatly changing the tracking characteristic and the focusing characteristic due to the influence of the above.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show the first embodiment.

FIG. 1 is a block diagram of the first embodiment. However, the solid line in FIG. 1 indicates the flow of the signal.

The optical disk 1 is fixed to a disk motor 2 and is rotatable in a predetermined direction.

The objective lens driving device includes an objective lens 3, an optical head 4, a rising mirror 5, a photodetector 6, a sum / difference calculation circuit 7, a focus error signal amplifier 8, a tracking error signal amplifier 9, and a focus control circuit. 10, a tracking control circuit 11, an interference mode compensation circuit 12, a focus direction drive coil 13, a track direction drive coil 14, a coarse positioning mechanism 15, and an objective lens holder 16.

The optical disk 1 and the objective lens 3 are arranged at a minute interval. The objective lens 3 is held by an objective lens holder 16, and a focus direction drive coil 13 and a track direction drive coil 14 are arranged near the objective lens holder 16. The optical head 4 includes an objective lens 3, an objective lens holder 16, a focus direction drive coil 13, a track direction drive coil 14, and a rising mirror 5.
It is composed of The optical head 4 is provided with a coarse positioning mechanism 15 for determining a coarse position of the objective lens 3 (the objective lens holder 16 or the optical head 4) and a photodetector 6.

The light incident on the optical disk 1 by the objective lens 3 is reflected on the surface of the rotating optical disk 1, passes through the objective lens 3 again, is reflected by the rising mirror 5, and is input to the photodetector 6. You. The photodetector 6 includes a plurality of divided cells, and the intensity of light output from the cells is output to the sum-difference calculation circuit 7. The signal input to the sum-and-difference calculation circuit 7 is divided into a focus error signal corresponding to a defocus and a tracking error signal corresponding to a positional shift amount in a track direction with respect to a target track in the sum-difference calculation circuit 7. An operation is performed.

Each of the distributed signals is output to either the focus error signal amplifier 8 or the tracking error signal amplifier 9. After being amplified by each amplifier, the signal from the focus error signal amplifier 8 is sent to the focus control circuit 10 and the tracking error signal amplifier 9
Is output to the tracking control circuit 11.

The tracking control circuit 11 calculates a coarse positioning drive signal and a fine positioning drive signal of the optical head 4, and outputs the coarse positioning drive signal to the coarse positioning mechanism 15 and the fine positioning drive signal to the track direction drive coil 14 and the interference mode. Each is input to the compensation circuit 12. The coarse positioning drive signal is mainly a signal having a frequency component of 1 kHz or less, and the fine positioning drive signal is a drive signal mainly including a high frequency component up to about 5 kHz.

The coarse positioning mechanism 15 performs the coarse positioning operation of the optical head 4 with respect to the optical disk 1 based on the coarse positioning drive signal. Further, an operation of positioning the objective lens 3 (the objective lens holder 16) on the target track is performed by the track direction drive coil 14 based on the fine positioning drive signal.

On the other hand, the focus drive signal output from the focus control circuit 10 is input to the focus direction drive coil 13 to perform an operation for positioning the objective lens 3 in the vertical direction with respect to the optical disc 1. The light spot formed on the information recording surface is focused.

Incidentally, since there is a possibility that the objective lens 3 is swung by the drive signal input to the track direction drive coil 14, the signal is input from the interference mode compensation circuit 12 to the focus direction drive coil 13 in order to cancel this movement. Is calculated. More specifically, the interference mode compensation circuit 12 performs an operation to cancel the swing mode generated by the drive signal to the track direction drive coil 14 by inputting the drive signal to the focus direction drive coil 13. The calculated drive signal is subjected to calculation including frequency characteristics. The calculated drive signal is added to the drive signal from the focus control circuit 10 and input to the focus direction drive coil 13.

The focus direction drive coil 13 performs a focusing operation at a target position based on the input drive signal.

The operation of the interference mode compensating circuit 12 will be described with reference to FIG.

The calculation in the interference mode compensating circuit 12 is performed in consideration of the influence of the swing mode of the objective lens 3 (the objective lens holder 16) on the track direction drive characteristics and the focus direction drive characteristics. Here, the influence of the swing mode on each drive characteristic can be considered as shown in FIG.

As shown in FIG. 2, the magnitude αt of the influence on the swing mode generated by the input of the drive signal to the track direction drive coil 14 and the focus direction drive coil 13
Αf, the magnitude of the influence on the swing mode caused by the input of the drive signal to the drive signal, and the influence coefficients βt and βf of the oscillation of the swing mode detected by the photodetector 6 as displacements in the focus direction and the track direction. , These four parameters determine the influence of the swing mode. The calculation in the interference mode compensation circuit 12 is performed based on these four parameters so as to have a frequency characteristic. In general, the frequency characteristics of the swing mode are very high, on the order of several kHz, so that it is preferable to have a band-pass characteristic or a bypass characteristic that allows passage near the frequency of the swing mode. As a result, the influence of the swing mode near the control band is large, so that the passing frequency of the interference mode compensating circuit 12 is a frequency near the control band, for example, a frequency of about 1 kHz to 10 kHz.

At this time, the gain G1 in the pass frequency region
By giving G1 = (− αt / αf) × K (1), the oscillation mode can be suppressed. Note that K is 0 ≦ K ≦ 1, depending on the polarity of land tracking and groove tracking described later.
Or, −1 ≦ K ≦ 1.

In order to provide an all-pass characteristic,
That is, the calculation may be a multiplication by a predetermined value. In this case, the predetermined value may be set near the value shown in the equation (1).

In the first embodiment as described above,
By compensating the movement of the objective lens 3 due to the drive signal input to the track direction drive coil 14 to be suppressed by the drive signal input to the focus direction drive coil 13, the swing of the objective lens 3 is performed. Thus, the objective lens 3 can be positioned with high accuracy even when the recording density is improved.

Next, the configuration of the second embodiment of the present invention will be described with reference to FIG.

In the following embodiments, the same components are denoted by the same reference numerals, and redundant description will be omitted.

The feature of the second embodiment is that the objective lens 3
That is, the track direction drive coil 14 is operated by using a drive signal from the focus control circuit 10 in order to suppress the swing of the track direction.

FIG. 3 is a block diagram of the second embodiment. The driving signal input to the interference mode compensating circuit 12 is a driving signal from the focus control circuit 10 and is calculated in the interference mode compensating circuit 12. The drive signal for suppressing the swing of the objective lens 3 is added to the drive signal from the tracking control circuit 11 and is input to the track direction drive coil 14. Other configurations and operations are the same as those of the first embodiment.

However, a good operation can be performed if the gain G2 in the pass region of the interference mode compensation circuit 12 is set according to the following relationship: G2 = (− αf / αt) × K (2)

In the second embodiment as described above,
By performing such compensation that the motion of the objective lens 3 oscillating by the drive signal input to the focus direction drive coil 13 is suppressed by the drive signal input to the track direction drive coil 14, the oscillation of the objective lens 3 is performed. Thus, the objective lens 3 can be positioned with high accuracy even when the recording density is improved.

Next, the configuration of the third embodiment of the present invention will be described with reference to FIG.

The feature of the third embodiment is that the drive signals from the focus control circuit 10 and the tracking control circuit 11 are input to the interference mode compensation circuit 12 so that the track direction drive coil 14 and the focus direction drive coil 13
Output the drive signal.

FIG. 4 is a block diagram of the third embodiment. A drive signal from the focus control circuit 10 and a drive signal from the tracking control circuit 11 are input to the interference mode compensating circuit 12, and the objective lens A drive signal for suppressing the swing of the third is obtained by calculation. The obtained drive signal for suppressing the oscillation is added to the drive signal output from the focus control circuit 10 and input to the focus direction drive coil 13, and output from the tracking control circuit 11 and input to the track direction drive coil 14. Is added to the driving signal. Other configurations and operations are the same as those of the first embodiment.

In the third embodiment as described above,
By calculating and calculating a drive signal that suppresses the excitation of the swing mode and adding the calculated drive signal to each drive signal, the swing of the objective lens 3 can be suppressed.

Next, the configuration of the fourth embodiment of the present invention will be described with reference to FIG.

The feature of the fourth embodiment is that the signals from the focusing error signal amplifier 8 and the tracking error signal amplifier 9 are directly input to the interference mode compensation circuit 12.

FIG. 5 is a block diagram of the fourth embodiment. The signal from the focusing error signal amplifier 8 is supplied to a focus control circuit 10 and an interference mode compensation circuit 12.
And a tracking error signal amplifier 9
Are output to the tracking control circuit 11 and the interference mode compensation circuit 12.

The interference mode compensating circuit 12 outputs a drive signal for suppressing the swing of the objective lens 3 to the track direction drive coil 14 and the focus direction drive coil 13 based on the two input signals. , Or the drive signal from the focus control circuit 10. Other configurations and operations are the same as those of the first embodiment.

With such a configuration, if a correlation spectrum between the tracking direction drive signal and the focus direction drive signal is obtained, a correlation spectrum equivalent to the calculation in the interference mode compensation circuit 12 can be obtained. .

Normally, the correlation spectrum of the rotation synchronization component of the optical disk is large, but by adopting the configuration as in the present embodiment, the spectrum near the frequency of the swing mode can be increased.

The interference mode control circuit 12
Is added to the output of the tracking control circuit 11 and the focus control circuit 10 before the input to the coil, that is, the objective lens holder 16
It is possible to effectively suppress the effect of the mechanical swing mode of the robot. As another configuration, for example, the output signal of the focus error signal amplifier 8 and the tracking error signal amplifier 9 is applied to the interference mode compensation circuit 1.
It is also possible to add two outputs and input them to the focus control circuit 10 and the tracking control circuit 11. However, in such a configuration, a signal for exciting the interference mode may be amplified in the focus control circuit 10 and the tracking control circuit 11, and it is difficult to effectively suppress the oscillation mode. Further, if the interference mode control circuit 12 is configured to remove this effect, there is a problem that the configuration of the interference mode control circuit 12 becomes large. On the other hand, by adopting a configuration as shown in FIGS. 3 to 5, it is possible to effectively suppress the interference mode with a simple control system configuration.

In the fourth embodiment as described above,
By calculating and calculating a drive signal that suppresses the excitation of the swing mode and adding the calculated drive signal to each drive signal, the swing of the objective lens 3 can be suppressed.

Next, the configuration of the fifth embodiment of the present invention will be described with reference to FIG.

A feature of the fifth embodiment is that a land / groove switching circuit 17 is provided.

FIG. 6 is a block diagram of the fifth embodiment. The output of the land / groove switching circuit 17 is output from the tracking control circuit 11 and the interference mode compensation circuit 12.
Connected to be input to

The optical disc 1 has a land track and a groove track as information recording tracks, that is, a groove portion and a hill portion of a track groove, and information can be recorded or reproduced on both of these tracks. Such an optical disc 1
When the tracking positioning is performed by using, the polarity of the tracking error signal is inverted between the land track and the groove track. This is because the polarity of the position error signal itself detected when tracking the groove and the hill is inverted, and a land-groove switching device 17 is provided to correct this inversion.

For example, when the swing mode of the objective lens 3 is generated so as to delay the phase of the positioning control system while tracking the land track, the polarity is reversed in the groove track to advance the phase. Focus control circuit 10 and tracking control circuit 11
Works. For this reason, if the advance of the phase makes the operation of each control circuit and each coil significantly unstable, for example, the land-groove switching circuit 17 operates so that the interference mode compensation circuit 12 operates only at the time of land tracking. Controlled. It should be noted that the interference mode compensating circuit 12 can be controlled to operate only at the time of groove tracking. Further, depending on the swing mode, the same phase delay may occur between land tracking and groove tracking, and in such a case, the polarity of the output signal of the interference mode compensating circuit 12 can be changed.

In the fifth embodiment described above,
Even if the polarity of the tracking error signal is inverted, the land / groove switching circuit 17 controls only land tracking or groove tracking, so that the positioning accuracy of the objective lens 3 does not decrease.

Next, the configuration of the sixth embodiment of the present invention will be described with reference to FIG.

The feature of the sixth embodiment is that the objective lens 3
And a tilt control circuit 32 for controlling the inclination.

FIG. 7 is a block diagram of the sixth embodiment. An inclination detecting circuit 31 including a sensor such as an optical sensor for detecting the amount of relative inclination of the objective lens with respect to the optical disk 1 near the objective lens 3 is provided. Provided. The output of the tilt detection circuit 31 is input to the tilt control circuit 32. The tilt control circuit 32 outputs the signal after the arithmetic processing (the tilt of the objective lens 3) to the focus control circuit 10, the tracking control circuit 11, and the objective lens holder 16.

In the sixth embodiment, it is possible to reduce the aberration which occurs when the relative tilt amount of the objective lens 3 with respect to the optical disk 1 increases and adversely affects the recording and reproduction of information. In particular, a high-density optical disk device is effective because the allowable range of the relative tilt amount is narrow.

In an optical disc apparatus having a tilt mechanism in which the objective lens 3 is provided to be tilted in advance with respect to the optical disc 1, a tilt operation for controlling the tilt mechanism is performed. In the same manner as described above, the interference operation is adversely affected in the track direction and the focus direction. However, since each drive signal is calculated from the tracking control circuit 11 and the focus control circuit 10 using the detection result of the tilt detection circuit 31, even if a tilt mechanism is provided, the operation is performed without lowering the positioning accuracy of the objective lens 3. it can. At this time, the tilt correction operation is performed at a low frequency of 1 kHz or less.

Next, the configuration of the seventh embodiment of the present invention will be described with reference to FIGS.

The feature of the seventh embodiment is that a projection 5 is formed on a bearing portion 102 which is a through hole of the objective lens holder 47 which contacts a support shaft 103 on which the objective lens holder 47 is supported.
1 and 52 are provided.

FIG. 8 is a front view of the objective lens holder according to the seventh embodiment, and FIG. 9 is a perspective view.

The objective lens holder 47 holds the two objective lenses 41 and 42 and holds the bearing unit 1 with respect to the support shaft 103.
02 is slidably supported. Objective lens 4
Reference numerals 1 and 42 are for a CD and a DVD, for example. Coil portions 43 and 44 are provided on the outer peripheral portion of the objective lens holder 47 so as to face the magnets 45 and 46, and are activated by an electromagnetic force in a track direction or a focus direction by flowing a current. The coil portions 43 and 44 are provided with plate-shaped small pieces 48 and 49 made of a magnetic material, and the objective lens holder 47 is maintained at a neutral position by using magnetic flux acting on the coil portions 43 and 44. I have. The so-called magnetic spring effect that generates an appropriate preload (in the direction of the arrow in FIG. 8) so that the bearing portion 102 slides appropriately on the support shaft 103 at the same time as being held at the neutral position is generated.

The objective lens holder 47 and the support shaft 103 are in contact with each other at the bearing 102, and the swing mode is likely to change depending on the state at this point of contact. However, in order to make the contact state as uniform as possible, FIG. It has such a configuration.

Two projections 5 are provided at positions near the objective lenses 41 and 42 above the inside (inner diameter surface) of the bearing 102.
1, 52 are provided. Preload is applied so that the support shaft 103 comes into contact with the protrusions 51 and 52.

In the seventh embodiment as described above,
Even when the tracking operation and the focusing operation are performed, the contact position between the support shaft 103 and the bearing unit 102 hardly changes, so that the disturbance force that may occur during each operation can be kept almost constant. Even when offset in the focusing direction or the focusing direction, uniform driving characteristics can be obtained without significant changes in tracking characteristics and focusing characteristics, and highly accurate positioning of the objective lens can be performed.

Therefore, the driving force for driving the objective lenses 41 and 42 is affected by the disturbance force in the uniform swing mode, and the uniform characteristics are obtained even when the objective lenses 41 and 42 move in the tracking or focusing direction. Can be held.

Accordingly, a highly accurate positioning operation can be performed on the objective lenses 41 and 42.

Further, by setting the contact position between the support shaft 103 and the bearing portion 102 at a position where a vibration mode that adversely affects the driving of the objective lenses 41 and 42 can be suppressed, the characteristics at the time of driving the objective lens are further stabilized. be able to. In general, the point of contact between the support shaft and the bobbin hole is a node of the vibration mode. Therefore, the support shaft 103 is required to be near the upper surface of the objective lens holder provided with the objective lens and close to the center of gravity of the objective lens holder. It is a suitable place for the contact position between the bearing portion 102 and the bearing portion.

Further, the projections 51 and 52 are
It is provided at a predetermined distance in the focus direction so that the inclination of 1, 42 is unlikely to occur, but if it is provided so that the approximate center of this distance is higher than the approximate center of the upper and lower end surfaces of the bobbin hole, the characteristics with respect to vibration will be improved. good.

Further, as shown in FIG. 10 (c), the objective lens holder 47 has an objective lens 42 having a high NA near the contact portion where it comes into contact with the support shaft 103 by preload (compared to the NA of the objective lens 41). May be provided.

The present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention. For example, although only a single objective lens is mounted on the objective lens holder, a plurality of objective lenses may be mounted on the objective lens holder.

Further, the supporting system of the objective lens is not limited to the shaft sliding type, but may be a wire supporting system.

The shape and arrangement position of the protrusion are shown in FIG.
As shown in FIGS. 12A and 11B, even if the aspect of the protrusion is configured to be wide, FIGS.
As shown in (1), it may be provided with a predetermined length (for example, consistently) in the axial direction of the bearing portion.

FIGS. 13 (a) and 13 (b) and FIGS. 14 (a) and 14 (a) and 14 (a) and 14 (a) and FIG.
It may be a single projection 53 as shown in FIG.

Further, even if the projection is not provided on the objective lens holder, FIGS. 15 (a) and 15 (b) and FIGS.
It may be provided on the support shaft itself as shown in FIGS.

[0095]

As described above, according to the present invention, the influence of the interference mode which is simultaneously displaced in both the focus direction and the track direction is suppressed, and the objective lens holder is displaced independently in the focus direction and the track direction. , Highly accurate positioning can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of an objective lens driving device according to the present invention.

FIG. 2 is an explanatory diagram of an operation of an interference mode compensation circuit of the objective lens driving device according to the present invention.

FIG. 3 is a block diagram of a second embodiment of the objective lens driving device of the present invention.

FIG. 4 is a block diagram of a third embodiment of the objective lens driving device according to the present invention.

FIG. 5 is a block diagram showing a fourth embodiment of the objective lens driving device according to the present invention.

FIG. 6 is a block diagram of a fifth embodiment of the objective lens driving device according to the present invention.

FIG. 7 is a block diagram of a sixth embodiment of the objective lens driving device according to the present invention.

FIG. 8 is a front view showing the vicinity of an objective lens holder according to a seventh embodiment of the objective lens driving device of the present invention.

FIG. 9 is a perspective view of the vicinity of an objective lens holder according to a seventh embodiment of the objective lens driving device of the present invention.

FIG. 10 is a perspective view of a bearing unit and an explanatory view and a front view of a preload according to a seventh embodiment of the objective lens driving device of the present invention.

FIG. 11 is a block diagram of a seventh embodiment of the objective lens driving device according to the present invention.

FIG. 12 is a perspective view and a front view illustrating another projection of the objective lens driving device of the present invention.

FIG. 13 is a perspective view and a front view illustrating another projection of the objective lens driving device of the present invention.

14A and 14B are a perspective view and a front view illustrating another projection of the objective lens driving device of the present invention.

FIG. 15 is a perspective view and a front view illustrating another projection of the objective lens driving device of the present invention.

FIG. 16 is a perspective view and a front view illustrating another projection of the objective lens driving device of the present invention.

FIG. 17 is a perspective view of a conventional objective lens driving device.

FIG. 18 is a graph showing the relationship between frequency and phase, and the relationship between frequency and gain.

FIG. 19 is a graph showing the relationship between frequency and phase, and the relationship between frequency and gain.

FIG. 20 is another perspective view of a conventional objective lens driving device.

[Description of sign]

 Reference Signs List 1 optical disk 2 disk motor 3 objective lens 4 optical head 5 rising mirror 6 photodetector 7 sum difference arithmetic circuit 8 focus error signal amplifier 9 tracking error signal amplifier 10 focus control circuit 11 track control circuit 12 interference mode compensation circuit 13 Focus direction drive coil 14 Track direction drive coil 15 Rough positioning mechanism 16 Objective lens holder

Claims (6)

[Claims] 1. An objective lens, an objective lens holder that holds the objective lens and is supported so as to be drivable in an optical axis direction of light incident on the objective lens and in one direction perpendicular to the optical axis. A focusing coil for driving the objective lens holder in the optical axis direction; a tracking coil for driving the objective lens holder in a direction perpendicular to the optical axis; and each of the focusing coil and the tracking coil. A magnetic circuit; a focus detection unit that detects displacement of the objective lens holder in the optical axis direction; a track detection unit that detects displacement of the objective lens holder in a direction perpendicular to the optical axis direction; A detection signal detected by the focus detection means is input, and the result obtained by arithmetically processing the detection signal is used as the focusing coil. And a focus control device that outputs the signal to the tracking coil, and a track control device that receives a detection signal detected by the track detection unit, and outputs a result obtained by arithmetically processing the detection signal to the tracking coil. An objective lens driving device, characterized in that: 2. An objective lens, an objective lens holder that holds the objective lens and is supported so as to be drivable in an optical axis direction of light incident on the objective lens and in one direction perpendicular to the optical axis. A focusing coil for driving the objective lens holder in the optical axis direction; a tracking coil for driving the objective lens holder in a direction perpendicular to the optical axis; and each of the focusing coil and the tracking coil. A magnetic circuit; a focus detection unit that detects displacement of the objective lens holder in the optical axis direction; a track detection unit that detects displacement of the objective lens holder in a direction perpendicular to the optical axis direction; A detection signal detected by the focus detection means is input, and the result obtained by arithmetically processing the detection signal is used as the focusing coil. And a track control device that receives a detection signal detected by the track detection unit and outputs a result obtained by performing an arithmetic processing on the detection signal to the tracking coil and the focusing coil. An objective lens driving device, characterized in that: 3. A signal output from the focus control device or the track control device is input to a compensation control device, and the compensation control device performs an arithmetic operation and outputs the signal from the track control device or the focus control device. The objective lens driving device according to claim 1, wherein the signal is added to the obtained signal and input to the tracking coil or the focusing coil. 4. The apparatus according to claim 1, wherein the compensation control device is operated so as to have a frequency characteristic that passes a frequency component near a control band determined by the track control device and the focus control device. 3. The objective lens driving device according to 2. 5. A correction device for correcting the inversion when the polarity of a signal detected by said track detecting means is inverted while tracking said objective lens to a desired position. The objective lens driving device according to claim 1, wherein 6. A supporting shaft for supporting the objective lens holder, which is reciprocable in the optical axis direction and rotatable in a plane substantially perpendicular to the optical axis, is inserted into the objective lens holder. There is a bearing part penetrating substantially parallel to the optical axis direction, and one of the bearing part and the support shaft has a projection having a size such that the objective lens holder can reciprocate and rotate. The objective lens driving device according to claim 1, further comprising a unit.