JPH0388137A - Method and device for driving objective lens - Google Patents

Abstract

PURPOSE:To perform fast access control by controlling a neutral position holding force generating coil in a direction to reduce a displacement quantity from a neutral position in the tracking direction of an objective lens holder when a seeking operation is performed. CONSTITUTION:A leaf spring 33' as a rocking part is fixed in the tracking direction against a unit main body 29. When the objective lens holder 11 is fluctuated in the tracking direction in fast access, the displacement quantity of the holder 11 can be detected since reflection quantities in right and left directions at a reflection prism 61 are different with each other. Then, currents is made to flow in the neutral position holding force generating coils 39, 39' corresponding to the displacement quantity from the neutral position, by which the strength of a developing magnetic field can be controlled. Thereby, it is possible to hold the holder 11 at the neutral position by quickly following acceleration applied to the holder 11 even when the magnitude and the direction are changed. Then, the fast access control can be performed by fixing magnetically the holder 11 on a rocking member.

Description

[Detailed description of the invention] The present invention optically reads and writes information by irradiating a light spot onto an optical recording medium such as an optical disk, magneto-optical disk, or optical card. The present invention relates to an objective lens driving method and apparatus for controlling the position of an objective lens that irradiates a light spot relative to a recording medium.

In the spot irradiation of Jōkitatetsusako, the objective lens is controlled and driven in the focusing direction and the tracking direction. One of the driving methods is to fix the holder to which the objective lens is attached to the unit body via a flexible member, and use this flexure to drive the objective lens holder for focusing and tracking using a magnetic drive mechanism. be.

FIG. 11 is a plan view showing such a conventional objective lens driving device, and FIG. 12 is a sectional view taken along the line 1-2. However, the magnetic drive member is omitted from illustration. Further, for convenience of explanation, the flexible member 510 is shown with halftone dots, and the objective lens 130 is shown with hatching in the plan view.

The objective lens holder 110 equipped with the objective lens 13 is
It is fixed to the unit main body 290 of the drive device by a flexible member 510 made of an integrally molded resin product.

The flexible member 510 has thin parts A, B,
B, C, and C are formed, and the thin part A acts as a bending hinge part in the tracking direction, and the thin parts B, B,
C and C act as bending hinges in the focus direction.

The tracking direction movement uses the thin flexible hinge part A as a fulcrum, and arcuate movement in the direction shown by the arrow T in the figure, and the focusing movement uses the thin flexible hinge part B as the fulcrum.

B, C, and C move the objective lens 130 up and down as shown by arrow F, thereby displacing the objective lens 130.

However, it is inevitable that the overall weight of the objective lens side centering on the hinge part A of the objective lens holder 110 and the opposite side will be unbalanced. However, it is practically impossible to achieve a precise balance in the final product due to variations in molded products, adhesives during assembly, wiring during mounting, etc. Therefore, high-speed tracking is required when seeking the entire unit. When accessing, the objective lens holder is displaced in the tracking direction due to acceleration, and during close access, vibration is induced and the tracking operation is started, which delays access and prevents speeding up of control.

Further, since the flexible member 51O is an integrally molded resin product, it can be said that the flexible member 51O is simplified by itself if attention is paid only to its component configuration. However, since its characteristics depend on the molding conditions of the resin, changes in hinge thickness, molding distortion, etc.
Variations in resin spring force, viscosity, etc. occur during the objective lens displacement operation, which becomes a factor that makes the drive control of the objective lens unstable. Moreover, since it is an integral structure, the movements in the focusing direction and the tracking direction affect each other, making it difficult to control the objective lens.

The present invention provides an objective lens driving method and device that enables high-speed access by preventing vibration of the objective lens in the tracking direction during seek, and also enables stable control of the objective lens holder. It is something.

The present inventor previously filed Japanese Patent Application No. 63-332674,
The present invention, which proposes a method for preventing vibration of an objective lens during seek, takes this technology one step further.

11. The objective lens driving method of the present invention fixes the objective lens holder to the unit body so as to be able to swing in the tracking direction and the focusing direction by a swinging member, and enables high-speed track access by moving the unit body; In an objective lens driving method that provides close access to an objective lens holder in a tracking direction and a focusing direction.

The swinging member is fixed to the unit body so that it cannot swing in the tracking direction, and during high-speed track access, the amount of displacement of the objective lens holder from the neutral position in the tracking direction is detected by an optical system, and this amount of displacement is detected by the optical system. The objective lens holder is magnetically fixed to the swinging member in the decreasing direction.

Further, in the objective lens drive device of the present invention, in the objective lens drive device in which the objective lens holder is fixed to the unit main body so as to be swingable in the tracking direction and the focus direction, the objective lens holder has a bending direction in the tracking direction. The relay member is swingably fixed to the unit main body via a second leaf spring whose deflection direction is the focusing direction, and the objective lens The first magnetic member is provided at the end of the relay member opposite to the end connected to the holder, and the first magnetic member is spaced from both sides of the objective lens holder that faces the first magnetic member. A pair of second
a magnetic member, wherein at least one of the first and second magnetic members is a neutral position holding force generating coil; and an optical system that detects the amount of displacement from the neutral position in the tracking direction of the neutral position, and the magnetic field strength generated by the neutral position holding force generating coil is controlled according to the amount of displacement detected by the optical system. .

The Sho-Iichiri objective lens holder is fixed to the unit body via a swinging member. The objective lens holder is swingable in the tracking direction relative to the swinging member. On the other hand, the swinging member that supports the objective lens holder in this manner is swingable in the focusing direction with respect to the unit body, but cannot swing in the tracking direction.

During high-speed tracking access, there is a swinging member fixed to the unit body that can swing in the focus direction but not swingable in the tracking direction, and an objective lens holder supported by this swinging member. Apply magnetic force between them to lock them. At this time, the optical system detects the amount of displacement of the objective lens holder from the neutral point position in the tracking direction, and according to this amount of displacement, the lock position by magnetic force is controlled in the direction in which the amount of displacement decreases, and the objective lens holder is Keep the holder in the neutral position.

In the device of the present invention, which uses a flexible member having two leaf springs and a relay member as the swinging member, a current is passed through the neutral position holding force generating coil, and the neutral position holding force generating coil is connected to the opposing magnetic member. The objective lens holder is locked by exerting a repulsive force between the two. At this time, the optical system attached to the objective lens holder detects the amount of displacement from the neutral position, controls the magnetic field strength generated by the neutral position holding force generating coil according to the amount of displacement, and moves the objective lens holder. Maintain in neutral position.

During close access, by stopping the current flowing through the neutral position holding force generating coil and releasing the lock caused by the magnetic force, the objective lens holder becomes free to swing in the tracking direction, allowing normal tracking operation. Perform focusing operation.

When operating in the focus direction, due to the deflection of the second leaf spring,
The relay member fixed to this leaf spring, the first leaf spring, and the objective lens holder swing together, and the objective lens holder moves up and down with respect to the unit body.

On the other hand, during the tracking direction operation, the objective lens holder swings relative to the relay member due to the deflection of the first leaf spring.

In this way, the tracking operation and the focusing operation do not affect each other, and the characteristics of the leaf spring can be almost the same when designed and manufactured, so unstable factors are reduced and control characteristics are stabilized.

FIG. 1 is a top view showing the objective lens driving device of the present invention;
Fig. 2 is a side view of the main parts of the magnetic drive mechanism with the exception of the tracking coil 17 omitted, and Fig. 3 is a longitudinal cross-sectional view of Fig. 2 (
1), FIG. 4 is a top view with the second leaf spring 33 removed from the top view of the main part, and FIG.
The figure is a sectional view taken along the line -v in FIG. 4.

As shown in FIGS. 1 and 2, a focusing coil 15 is wound around the circumferential surface of the objective lens holder 11 to which the objective lens 13 is fixed.

Four tracking coils 17 are attached.

Driving magnet 21. The objective lens holder 11 is attached to the unit main body 2 so that the device single coil l5 and the tracking coil 17, which are composed of an outer yoke 23 and an inner yoke 19, are arranged.
It is supported by 9.

The objective lens holder 11 is attached to the relay member 35 via the l-th leaf spring 31. As can be seen from, for example, FIGS. 3 and 4, the l-th leaf spring 31 is a leaf spring whose surface expands in the vertical direction in FIG. 3, that is, in the focus direction (arrow F). The direction of deflection of the spring 31 is aligned with the tracking direction T. Therefore, the objective lens holder l1 is supported by the first leaf spring 3l so as to be swingable in the tracking direction T with respect to the relay member 35.

On the other hand, the relay member 35 includes a pair of second leaf springs 33 . 33', the unit body 29
It is fixed to . second leaf spring 33;

33' has a surface extending in the plane of the paper in FIG. 1, that is, in the tracking direction T, and the deflection direction of this leaf spring is aligned with the focus direction F. Therefore, the second leaf spring 33.
33', the relay member 35 that supports the objective lens holder 11 is supported so as to be swingable in the focus direction F with respect to the unit body 29.

Furthermore, since the spreading surfaces of the first leaf spring 3l and the second leaf spring 33, 33' are perpendicular to each other and their swinging directions are perpendicular to each other, the swinging of the first leaf spring 31 is , second leaf spring 3
3, 33' does not affect the swinging, and
The reverse is also true.

The objective lens holder 11 has a notch 11a in which the relay member 35 is disposed.

In order to suppress the resonance of the leaf springs that occurs during operation, the first and second leaf springs 31, 33, and 33' are made of materials and have thicknesses set to be lightweight and sufficiently vibration-proofing. It is desirable to have a structure in which an elastic body such as rubber is laminated and integrated with a metal elastic plate. In order to suppress resonance, in addition to this rubber laminated fixing structure, as shown in FIGS. 6A and 6B, the relay member 35 side of the first leaf spring 31 and the second leaf spring 33. 33', the fixed side of the unit body 29 is covered with a rubber elastic body 4 set for the same purpose.
1. A similar effect can be obtained even if the structure is sandwiched by 41'.

At the time of close access, the driving magnetic device 19.

21, 23 and the tracking coil l7, a force is applied to the objective lens holder l1 in the tracking direction T according to the signal, and the first plate spring 3
1 is bent, and the objective lens holder 11 operates in the tracking direction T. At this time, the lth leaf spring 31 and the second leaf spring 33. 33' are coupled via the relay member 35, and the swinging directions of both are set to be perpendicular to each other as described above, so that the swinging of the first leaf spring 31 is similar to that of the second leaf spring 33'. Leaf spring 33. It does not affect the movement of 33'.

Similarly, during close access, the driving magnetic devices 19, 2
1.23 and the focusing coil 15, force is applied to the objective lens holder 11 in the focusing direction F according to the signal, and the second leaf spring 33, 33' is bent, causing the objective lens holder 11 to bend. 11 operates in the focus direction F.

At this time, as described above, the swinging of the second leaf springs 33, 33' does not affect the movement of the first leaf spring 31. In this way, the movements in the tracking direction T and the focus direction F are separated. By doing so, you can prevent the two from influencing each other.

Further, unlike synthetic resin molded products, the characteristics of a leaf spring can be made almost the same between the time of design and the time of manufacture, and stable drive characteristics can be obtained in accordance with the design characteristics. Furthermore, since the swinging member that supports the objective lens holder 11 on the unit main body 29 is composed of the thin leaf springs 31, 33, 33' and the relay member 35 made of resin or the like,
Compared to the conventional example shown in Figure 11.12,
The volume of the portion corresponding to the hinge can be reduced, making it possible to reduce weight and size.

During a high-speed tracking operation during a seek, the unit main body 29 itself moves at high speed in the direction of the paper in FIG. At this time, since the objective lens holder 11 is supported so as to be able to swing freely in the plane of the paper with respect to the relay member 35, it is displaced in the tracking direction T due to the acceleration during high-speed track access, and the movable part is free during close access. It induces vibration and interferes with stable high-speed control.

In the embodiment shown in FIGS. 1 to 5, taking advantage of the fact that the tracking direction and the focusing direction operate separately as described above, a magnet is attached to the end of the relay member 35 opposite to the first leaf spring 31. 37 is provided in the notch 1fa of the objective lens holder 11 at a position facing the N and S poles of the magnet 37, and is provided with protrusions 11b and 11b facing away from these magnetic poles.
lb' is provided, and a neutral position holding force generating coil 39°39' is wound around this protrusion. At the time of high-speed track access, current is supplied to the neutral position holding force generating coils 39, 39' to exert a counterforce with the magnet 37, thereby generating a force counteracting acceleration.

Further, in the present invention, when operating the neutral position holding coils 39 and 39', the amount of displacement from the neutral position in the tracking direction is measured.

As shown in FIGS. 3 to 5, a reflecting prism 61 is attached to the construction portion 11c on the lower surface of the objective lens holder 11. As shown in FIGS. As shown in FIG. 5, the reflective prism 61 is a chevron-shaped prism with reflective surfaces (mirrors) formed on the right and left sides, and is arranged so that the ridge line is perpendicular to the plane of the paper at a neutral position.

The light beam 67 passes through the through hole 33'a of the second leaf spring 33'.
When the objective lens holder 11 is in the neutral position, the amount of light reflected from the right reflective surface and incident on the photodiode 63 (sensing element) is:
When the objective lens holder 11 swings in the tracking direction during 6-shift when the amount of light incident on the left photodiode 65 (sensing element) is the same, the amounts of light reflected on the left and right sides of the reflecting prism 61 are different. Measure the neutral position holding force generating coil 39°39' so that this amount becomes zero.
For example, in Fig. 4, when the objective lens holder oscillates in the direction in which the coil 39 approaches the north pole of the magnet, The magnetic field generated in the coil 39 is strengthened. Note that the photodiodes 63 and 65 are supported by the unit body 29 or the relay member 35.

FIG. 6 is a block diagram showing an example of this feedback control. (ideally zero), the difference is amplified by an amplifier (Amρ) and the neutral position holding force generating coils 39 and 39' are driven to make the displacement zero.

By measuring the amount of displacement using the optical system and controlling the neutral position holding force generating coils 39, 39', even if the magnitude or direction of the acceleration applied to the objective lens holder 11 changes, it can be quickly followed. Objective lens holder 11
can be kept in a neutral position. Furthermore, even if there is some problem with the assembly accuracy of the objective lens drive device, this can be resolved electrically.

The light beam 67 is obtained from an appropriate light source, but the objective lens 13
A part of the optical system for spot irradiation can be divided and used. This allows the device to be made more compact.

FIG. 7 is a configuration diagram showing an example of an optical system.

During spot irradiation by the objective lens 13, the light beam from the laser diode 71 passes through the collimator lens 73. The beam passes through a beam shaping prism 75 and enters a beam splitter 77 . The light flux that enters the rising mirror 79 from the beam splitter 77 is reflected and raised, and enters the objective lens 13 of the objective lens holder 11 as a light flux 69 (see also FIG. 3). The reflected light passes through the objective lens 13 and the rising mirror 79. The light passes through the beam splitter 77 and enters the recorded information detection system 91 (readout system). The detection system includes a wavelength plate 81. It consists of a beam splitter 83, a condensing lens 85.87, and a photodiode 89.89.

When detecting the neutral position, a part of the luminous flux is split from the beam splitter 77, the beam diameter is adjusted by the beam diameter control slit 93, the beam diameter is raised by the first position detection prism 11, and the luminous flux is made to enter the reflecting prism 61 as the luminous flux 67. .

Furthermore, after the high-speed track access is completed, the current is stopped flowing through the neutral position holding force generating coil 39, 39'.
The circuit configuration is such that the lock function is released when access is made in secret.

Furthermore, the relay member and the objective lens holder are magnetically locked during high-speed access and left free during close access. For example, a magnet may be attached to the objective lens holder and a coil may be provided to the relay member. , an appropriate configuration can be taken.

As described above, by holding the neutral position, it is possible to prevent vibration in the tracking direction during seek and speed up access control, but the tracking coil is used to generate force to counter the acceleration generated during seek. By causing the vibration to occur during seek, vibration during seek can be further prevented.

As shown in Figures 1 and 2, during secret access,
Driving magnet 21. By passing a current through the tracking coil 17 within the magnetic field formed by the inner yoke 19 and the outer yoke 23, the objective lens holder 11 rotates in the tracking direction (T).

This method itself is the same as the conventional mechanism. A current is passed through this tracking coil 17 during seek, and a force counteracting the force applied to the objective lens holder 11 is obtained by acceleration during seek.

The force F generated by acceleration during seek reduces the slight unbalanced mass of the objective lens holder 11 by Δm.

Let the seek acceleration be α.

F=α・Δm It is expressed as

Therefore, the tracking coil 17 generates a force in the objective lens holder 11 that counteracts this and rotates in the direction opposite to the direction of the acceleration.

FIG. 9 is a block diagram showing an example of this control, in which the load speed signal (moving speed signal of the unit main body 29) is transmitted to
mp) and is supplied to an acceleration counter force generating coil (same as the tracking coil 17) to provide a co-force in the opposite direction to the acceleration direction, thereby directing the displacement from the neutral position to zero. As described above, this displacement is detected and the neutral position holding force generating coil is further driven.

A specific control example is shown in FIG. 9, and acceleration occurs when increasing the feeding speed of the unit body 29 (objective lens holder 11) and when entering a stopping operation.

Along with this, the voice coil motor (VCM) voltage for feeding is controlled, but if the tracking coil voltage is changed in accordance with this, the force opposing the seek acceleration becomes
Obtained by tracking coil.

After the seek is completed, the tracking coil 17 is used for normal tracking servo.

In this way, by using the tracking coil 17 to generate a force that counteracts the acceleration during seek and maintaining the neutral position, the amount of displacement from the neutral position is reduced.
Objective lens holder 11 with neutral position holding force generating coil
This makes it easier to prevent vibrations when seeking.

According to the present invention, an optical means for swingably supporting an objective lens holder with respect to a unit body and detecting deviation of the objective lens holder from a neutral position during seek; By providing a magnetic fixing means capable of ON-OFF control between the swinging member and the objective lens holder, and locking the objective lens holder at a neutral position with respect to the swinging member during seek; A flexible member (swinging member) that supports the holder on the unit body is formed by first and second leaf springs whose deflection directions are set in the tracking direction and the focus direction, respectively, and a relay member provided between both leaf springs. By configuring this, the following effects can be obtained.

- The objective lens holder can be maintained in a neutral position during high-speed track access, making it possible to speed up access control.

- By forming the flexible member mainly from a leaf spring whose characteristics can be almost matched between the design and manufacturing times, variations are reduced and it becomes possible to drive the objective lens in accordance with the design values.

■ Since the deflections in the focus and tracking directions operate independently, movements in both directions do not affect each other and are easy to control.

[Brief explanation of drawings]

FIG. 1 is a top view of the objective lens driving device of the present invention, FIG. 2 is a side view of the main part thereof, and FIG. 3 is a longitudinal sectional view of FIG. 2. FIG. 4 is a top view of the main part of FIG. 1 with the second leaf spring 33 removed, and FIG. 5 is a sectional view taken along the line ■--■ in FIG. 4. FIGS. 6A and 6B are explanatory diagrams showing a structure in which an elastic body is sandwiched. FIG. 7 is a block diagram showing an example of controlling the neutral position holding coil. FIG. 8 is an explanatory diagram showing an example of an optical system. FIG. 9 is a block diagram showing an example of controlling the acceleration counterforce generating coil (tracking coil), and FIG. 10 is a timing chart. FIG. 11 is a top view showing a conventional objective lens driving device, and FIG. 12 is a sectional view thereof. 11... Objective lens holder 13... Objective lens 1
5... Focusing coil 17... Tracking coil 19... Inner yoke 21... Drive magnet 2
3...Outer yoke 31...First leaf spring 3
3.33'...Second leaf spring 35...Relay member 3
7... Control magnet 39.39'... Neutral position holding force generating coil 41.4
1'... Elastic body 51... Flexible member 61...
・Reflection prism 6365...Photodiode 67...Light flux 69...Light flux 71...
・Laser diode 73...Collimator lens 75...Beam shaping prism 79...Elevating mirror 93...Beam diameter control slit 95...Elevating prism

Claims (1)

[Claims] 1. The objective lens holder is fixed to the unit body so as to be swingable in the tracking direction and the focusing direction by a swinging member, so that high-speed track access by movement of the unit body and the movement of the objective lens holder In an objective lens driving method that provides close access in the tracking direction and focus direction, the swinging member is fixed to the unit body so as not to swing in the tracking direction, and during high-speed track access, the swinging member is fixed in the tracking direction of the objective lens holder. The amount of displacement from the neutral position is detected by an optical system,
An objective lens driving method characterized by magnetically fixing an objective lens holder to a swinging member in a direction that reduces the amount of displacement. 2. Supplying current during high-speed track access to the tracking coil that performs tracking drive during close access,
2. The objective lens driving method according to claim 1, wherein a force counteracting the force applied to the objective lens holder due to acceleration during high-speed track access is generated. 3. In the objective lens drive device in which the objective lens holder is fixed to the unit body so as to be swingable in the tracking direction and the focus direction, the objective lens holder is connected to the relay member via the first leaf spring whose deflection direction is the tracking direction. This relay member is swingably fixed to the unit main body via a second plate spring whose deflection direction is the focus direction, and further, the relay member is swingably fixed to the unit main body via a second leaf spring whose deflection direction is the focus direction. a first magnetic member provided at the end of the side relay member;
A first magnetic member is attached to the objective lens holder portion facing the first magnetic member.
a pair of second magnetic members provided to sandwich the magnetic member spaced from both sides, and at least one of the first and second magnetic members is composed of a neutral position holding force generating coil. and an optical system that is attached to the objective lens holder and detects the amount of displacement from the neutral position in the tracking direction of the objective lens holder. An objective lens driving device characterized by controlling the strength of a magnetic field generated by a position holding force generating coil. 4. Supplying current during high-speed track access to the tracking coil that performs tracking drive during close access,
4. The objective lens drive device according to claim 3, further comprising acceleration counterforce generating means for generating a force counteracting the force applied to the objective lens holder due to acceleration during high-speed track access.