JP3323699B2 - Objective lens drive - Google Patents

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 apparatus in an apparatus for optically recording and / or reproducing information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art An objective lens driving device includes a focusing shift due to a vertical movement of a recording surface due to a warp of a disc-shaped recording medium (hereinafter referred to as a disc) such as a compact disc, a tracking shift due to eccentricity and the like, and a disc and an objective lens. In order to correct the angular deviation, the objective lens is driven in two axial directions: a direction perpendicular to the disk (hereinafter, referred to as a focusing direction) and a radial direction of the disk (hereinafter, referred to as a tracking direction).

In an optical information recording / reproducing apparatus including the above-described objective lens driving apparatus, if the optical axis of the objective lens is inclined with respect to the disk surface, optical aberration occurs, and the signal at the time of recording / reproducing deteriorates. Cause. Therefore, in a conventional optical information recording / reproducing apparatus, a tilt control device that tilts the entire optical pickup by a tilt motor such as a DC motor and controls the optical axis has been used.

Further, as disclosed in Japanese Patent Application Laid-Open No. 6-162540, for example, a relative angle between a disc and an objective lens is detected, and based on the detected relative angle signal,
There has been proposed a method of adjusting a drive current flowing through a plurality of focusing coils fixed to a movable body to correct a tilt.

[0005]

In an optical recording / reproducing apparatus using a disk, it is being realized to reduce the diameter of a condensed spot by using an objective lens having a high aperture ratio and to increase the recording capacity. In this case, the degree of aberration due to the inclination of the optical axis of the objective lens with respect to the disk is equal to the aperture ratio of 3
Since it becomes larger in proportion to the power, it is necessary to position the optical axis of the objective lens with respect to the disc with higher precision in order to obtain a good recording / reproducing signal. However, D
The tilt correcting means using a C motor or the like can correct only a low-frequency angle shift, and has a problem that it is difficult to reduce aberrations.

On the other hand, if a method of detecting the relative angle between the disk and the objective lens and adjusting the drive current flowing through a plurality of focusing coils fixed to the movable body based on the detection signal to correct the tilt is used. It is possible to correct an angle shift in a wide range from a frequency to a high frequency. However, in such a configuration, since the magnetic circuit is fixed, the position of the plurality of focusing coils with respect to the magnetic flux density distribution of the magnetic circuit changes with movement of the movable body, so that each focusing coil is linked. The amount of magnetic flux that fluctuates. Therefore, the drive sensitivity fluctuates depending on the position of the movable body, and there are problems such as deterioration of servo stability and control accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and detects a relative angle of an objective lens with respect to a disk to cope with an angular shift from a low frequency to a high frequency and to adjust the movable body. It is an object of the present invention to provide an objective lens driving device capable of performing a stable angle correction of driving sensitivity regardless of a position in a focusing direction and a tracking direction.

[0008]

In order to achieve the above object, an objective lens driving device according to the present invention comprises an objective lens for recording and / or reproducing optical information on a disc-shaped recording medium, and an objective lens. Holding the lens holder and the pair
A movable body having at least one permanent magnet fixed to the lens holder, the movable body having a magnetization direction in an optical axis direction of an object lens and a tangential direction perpendicular to a radial direction of the disc-shaped recording medium ; At least four rod-shaped support members that movably support the rod-shaped support member in the optical axis direction or the radial direction , a fixed base that fixes the rod-shaped support member, and a position that is opposed to the permanent magnet in the tangential direction. At least the one yoke made of a magnetic material, wound wound on the yoke, have a winding axis in the optical axis direction, a substantially load of the movable body has
A pair including a center and a plane substantially perpendicular to the radial direction.
At least two focusing coils disposed at positions corresponding to each other, at least one tracking coil wound around the yoke and having a winding axis in the radial direction, and the objective for the disc-shaped recording medium. Lens tilt
And a tilt detecting means for outputting a tilt detection signal.
The at least two focusing coils
One of the focusing coils is
Output signal and the focus error signal.
The other focusing coil is connected to the tilt detection signal.
Signal and the difference signal between the focus error signal
It is characterized by being driven .

[0009] In the above configuration, the tilt detecting means is preferably a light sensor mounted on the reflective to the movable body. Further, in the above configuration, it is preferable that power is supplied to the tilt detection unit via the rod-shaped support member. In the above configuration, it is preferable that a cross-sectional shape of the rod-shaped support member is any one selected from a circle, a substantially polygonal shape, and an elliptical shape.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the objective lens driving device according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a configuration of an objective lens driving device according to an embodiment of the present invention. In FIG. 1, the objective lens driving device includes an objective lens 1, a lens holder 2 holding the objective lens 1, permanent magnets 3a and 3b arranged and fixed to the lens holder 2 along a tangential direction K, and a lens holder. 2, a tilt detector 4, a fixed base 5, tracking coils 6 a to 6 d, a focusing coil 7
a to 7d, wire members 8a to 8d (not shown because 8d is located on the back side of the lens holder 2), and a support member 9
And so on. In the figure, 10 is a disk, T
Is a tracking direction parallel to the radial direction of the disk 10,
F indicates a focusing direction perpendicular to the disk 10, K indicates a direction perpendicular to the focusing direction F and the tracking direction T, and J indicates an optical axis of the objective lens 1. Objective lens 1, lens holder 2, permanent magnets 3a and 3
b and the tilt detector 4 constitute a movable body 20.

The tilt detector 4 includes a light emitting section 4a and a light receiving section 4 arranged in the tracking direction T with the light emitting section 4a interposed therebetween.
b and 4c, and irradiates light from the light emitting unit 4a to the disk 10 and emits light reflected by the disk 10 to the light receiving unit 4.
Light is received at b and 4c, and a voltage corresponding to the amount of received light is generated. The fixed base 5 is formed of a magnetic material and has a tangential direction K with respect to the permanent magnets 3a and 3b.
Are provided along the opposite yoke portions 5a to 5d. Specifically, opposing yoke portions 5a and 5b are disposed at positions opposing permanent magnet 3a, opposing yoke portions 5c and 5d are disposed at positions opposing permanent magnet 3b, and opposing yoke portions 5a
The positional relationship between and y is such that the opposing yoke portion 5a and the opposing yoke portion 5b are symmetrical with respect to a plane substantially including the center of gravity of the movable body 20 and substantially perpendicular to the tracking direction T. Further, the positional relationship between the opposing yoke portions 5c and 5d is similarly arranged.

Each of the tracking coils 6a to 6d has a winding axis in the tracking direction T,
a to 5b. Focusing coil 7a
7d have winding axes in the focusing direction F, and are wound around the opposing yoke portions 5a to 5b. Each of the wire members 8a to 8d has an axis in the tangential direction K,
The rod-shaped support members are substantially parallel to each other, and are formed of a conductive material. One end of each of the wire members 8 a to 8 d is connected to the lens holder 2. The support member 9 includes
The other ends of the wire members 8a to 8d are connected,
It is fixed to a fixed base 5. Accordingly, the movable body 20 is supported by the wire members 8a to 8d so as to be movable in the focusing direction F, the tracking direction T, and the rotation direction around the tangential direction K with respect to the fixed base 5.

Next, FIG. 2 shows a circuit configuration of a tilt control circuit of the objective lens driving device of the present embodiment. In FIG.
The tilt control circuit includes the light receiving units 4 b and 4 of the tilt detector 4.
c, a differential drive amplifier 12 for outputting a sum of a differential output from the differential amplifier 11 and a focus error signal, and a differential amplifier 11
And an inversion drive amplifier 13 that outputs a differential output of a differential output from the controller and a focus error signal. Forward drive amplifier 12
Is supplied to the focusing coils 7a and 7c, and the output of the inversion drive amplifier 13 is supplied to the focusing coils 7b and 7d.

The operation of the objective lens driving device configured as described above will be described. Tracking direction T
In the case of the driving of (1), an electromagnetic force is generated by the magnetic flux generated by the permanent magnets 3a and 3b being orthogonal to the current flowing through the tracking coils 6a to 6d. Tracking coil 6a
Since 6d are fixed to the fixed base 5, the movable body 20 relatively translates substantially in the tracking direction T. On the other hand, in the case of driving in the focusing direction F, the permanent magnet 3a
And 3b are generated by the focusing coils 7a to 7b.
An electromagnetic force is generated by being orthogonal to the current flowing through 7d, and the movable body 20 similarly translates substantially in the focusing direction F.

Next, the rotational drive in the tangential direction K will be described. First, tilt detection is performed as follows.
When the optical axis J of the objective lens 1 and the disk 10 are perpendicular to each other, as shown in FIG. 3, the light emitted from the light emitting unit 4a of the tilt detector 4 is reflected by the disk 10 and received by the light receiving units 4b and 4c. Is done. At this time, the amount of light received by the light receiving unit 4b is equal to the amount of light received by the light receiving unit 4c. On the other hand, when the optical axis J of the objective lens 1 is not perpendicular to the disk 10, as shown in FIG. 4, a part of the light reflected by the disk 10 is not received by the light receiving portion 4b or 4c, There is a difference between the amount of light received by the light receiving unit 4c and the amount of light received by the light receiving unit 4c. Therefore, the signals generated by the light receiving sections 4b and 4c are respectively input to the differential amplifier 11, and the difference is obtained to generate a tilt detection signal.

Next, the tilt drive, which is a rotational drive around the tangential direction K, is performed as follows. First, the tilt detection signal is divided into two, one of which is input to the forward drive amplifier 12,
The other is input to the inversion drive amplifier 13. The output of the forward drive amplifier 12 is supplied to the focusing coils 7a and 7c, and the output of the reverse drive amplifier 13 is supplied to the focusing coils 7b and 7d together with the focusing drive signal. Therefore, a moment corresponding to the tilt detection signal acts on the permanent magnets 3a and 3b, and the angle deviation between the disk 10 and the optical axis J of the objective lens 1 is corrected.

Further, when the movable body 20 is in the tracking direction T
Will be described with reference to FIGS. 5 and 6. FIG. Now, an angle shift between the disk 10 and the optical axis J of the objective lens 1, that is, a tilt drive current corresponding to the tilt drive signal is supplied to the focusing coils 7a and 7c via the forward drive amplifier 12, and to the inversion drive amplifier 13 It is assumed that the focusing coils 7b and 7d are respectively energized through. At this time, the movable body 20
Is located in the neutral position shown by the solid line in FIG. 5, the permanent magnets 3a and 3b have focusing coils 7a respectively.
7b generate a reaction force of the electromagnetic force. The tilt driving force in the tracking direction T is distributed as shown by the solid line in FIG. Here, an axis that passes through the substantially center of gravity of the movable body 20 and is parallel to the tangential direction K is referred to as a center of gravity axis.
The distribution of the tilt driving force is symmetric about the center of gravity of the movable body 20, and the movable body 20 rotates around the center of gravity by an angle corresponding to the tilt drive signal.

When the movable body 20 is located at a position moved in the tracking direction as shown by a broken line in FIG.
Since the permanent magnets 3a and 3b, which are magnetic field sources, are moving together with the movable body 20, the permanent magnet 3a and the opposing yoke portions 5a and 5b or the permanent magnet 3b and the opposing yoke portion 5
The magnetic flux density distribution between c and 5d also changes, and the tilt driving force in the tracking direction T is distributed as shown by the broken line in FIG. That is, since the distribution of the tilt driving force also moves with the movement of the permanent magnets 3a and 3b, the distribution of the tilt driving force is also substantially symmetric about the center of gravity of the movable body 20. Therefore, the movable body 2
0 rotates by an angle corresponding to the tilt drive signal about the center of gravity axis, and a constant tilt drive sensitivity is always obtained regardless of the position of the movable body 20.

In the above embodiment, the focusing coils 7a and 7b are located at positions substantially including the center of gravity of the movable body 20 and symmetric with respect to a plane substantially perpendicular to the tracking direction T.
However, the present invention is not limited to this, and it is sufficient that a rotational driving force about the center of gravity axis is given to the movable body 20. For example, at a position that includes the substantially center of gravity of the movable body 20 and is symmetrical with respect to a plane that is substantially perpendicular to the focusing direction F,
Two tracking coils may be arranged, and a signal in which a tilt detection signal is superimposed on a tracking error signal may be output to the tracking coil.

In the above embodiment, the direction of gravity is not specifically discussed, but the same effect can be obtained regardless of the direction of gravity. In addition, the tilt drive sensitivity when the movable body 20 moves in the tracking direction T has been described.
The same effect can be obtained also in the case of moving in the focusing direction F. The cross-sectional shapes of the wire members 8a to 8d, which are rod-shaped support members, are circular, substantially polygonal,
Similar effects can be obtained in any of the elliptical shapes.

Further, in the above-described embodiment, the four-wire supporting mechanism for supporting the movable body 20 by the four rod-shaped supporting members has been described as the supporting mechanism, but the focusing direction, the tracking direction, and the rotating direction around the tangential direction K are described. Any support mechanism may be used as long as it is movably supported on three axes in the tilt driving direction. For example, a support mechanism in which a parallel leaf spring is formed into a predetermined shape by etching or the like so as to be movably supported on three axes is also the same. It is possible to achieve the effect described above.

Further, in the above-described embodiment, the tilt detector 4 in which the reflection type optical sensor is mounted on the movable body 20 as the tilt detecting means has been described, but the tilt detecting means has a relative position between the optical axis of the disk 10 and the optical axis of the objective lens 1. It is sufficient that the angle can be detected, and the present invention is not limited to this. If a part of the recording / reproducing light beam is used instead of the light emitting section 4a of the tilt detector 4, the same effect can be obtained, and further, the weight and simplification can be realized.

[0023]

As described above, according to the present invention, the objective lens, the lens holder for holding the objective lens, and the permanent magnet which is a magnetic flux generating source are integrated into a movable body, so that the movable body is moved in the tracking direction. Even if it moves, the permanent magnet that is the magnetic field source moves together with the movable body, the magnetic flux density distribution between the permanent magnet and the opposing yoke changes, and the distribution of tilt driving force moves with the movement of the permanent magnet. I do. Therefore, the distribution of the tilt driving force becomes substantially symmetric with respect to the center of gravity of the movable body. Therefore, the movable body rotates about the center of gravity axis by an angle corresponding to the tilt drive signal, and constant tilt drive sensitivity is always obtained regardless of the position of the movable body. Since the object to be driven is lightweight and small, it is possible to correct the angle shift in a wide range from low frequency to high frequency. Further, in the tilt control, it is possible to realize servo stability and high-accuracy control accuracy. As a result, even if an objective lens having a high aperture ratio is used to realize high-density recording and reproduction, optical aberration and defocus are suppressed, and accurate recording and reproduction of information can be performed.

The apparatus further comprises a tilt detecting means for detecting an inclination of the objective lens with respect to the disk-shaped recording medium, and outputs a signal obtained by superimposing a focusing drive signal and a tilt drive signal by a forward drive amplifier and a reverse drive amplifier to a focusing coil. Therefore, the focusing coil can be used for both the driving in the focusing direction and the driving in the tilt driving direction, which is the rotational driving direction around the tangential direction, thereby realizing a reduction in size and weight, a reduction in the number of parts and a reduction in man-hours, resulting in cost reduction. be able to. Also, the driving coil is
Since it is not mounted on the movable body, only the tilt detector needs power supply to the movable body, and power can be supplied via the four rod-shaped support members.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of an objective lens driving device according to the present invention.

FIG. 2 is a circuit diagram of a tilt control circuit in one embodiment of the objective lens driving device of the present invention.

FIG. 3 is a schematic diagram of a main part when the tilt detection unit has no inclination;

FIG. 4 is a schematic diagram of a main part when a tilt of a tilt detection unit occurs.

FIG. 5 is a schematic diagram of a main part for describing an operation of the objective lens driving device of the present invention.

FIG. 6 is a tilt drive distribution diagram in the tracking direction on the movable body of the objective lens driving device of the present invention.

[Explanation of symbols]

 T: tracking direction F: focusing direction K: tangential direction J: optical axis of objective lens 1: objective lens 2: lens holder 3a, 3b: permanent magnet 4: tilt detector 4a: light emitting unit 4b, 4c: light receiving unit 5: Fixed bases 5a, 5b, 5c, 5d: opposing yoke portions 6a, 6b, 6c, 6d: tracking coils 7a, 7b, 7c, 7d: focusing coils 8a, 8b, 8c, 8d: wire members 9: support members 10: Disk 11: Differential amplifier 12: Forward drive amplifier 13: Reverse drive amplifier

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-366429 (JP, A) JP-A-7-73484 (JP, A) JP-A-4-57226 (JP, A) JP-A-7-73 73486 (JP, A) JP-A-6-251405 (JP, A) JP-A-3-137831 (JP, A) JP-A-1-97419 (JP, U) JP-A 64-12219 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 09-7/10

Claims (4)

(57) [Claims] 1. An objective lens for recording and / or reproducing optical information on a disc-shaped recording medium, a lens holder for holding the objective lens, an optical axis direction of the objective lens and a disc-shaped recording medium. A movable body having a direction of magnetization in a tangential direction perpendicular to the radial direction and including at least one permanent magnet fixed to the lens holder; and enabling the movable body to move in the optical axis direction or the radial direction. At least four rod-shaped support members for supporting, a fixed base for fixing the rod-shaped support members, a yoke made of at least one magnetic body disposed at a position facing the permanent magnet in the tangential direction, and the yoke wound around the, have a winding axis in the optical axis direction,
Including a substantially center of gravity of the movable body, and substantially perpendicular to the radial direction
At least symmetrically positioned with respect to the
Two focusing coils, at least one tracking coil wound around the yoke and having a winding axis in the radial direction, and a tilt of the objective lens with respect to the disc-shaped recording medium are detected.
And a tilt detecting means for outputting a tilt detection signal.
And Bei, one of the at least two focusing coils
One of the focusing coils and the tilt detection signal
The sum signal with the focus error signal and the other focus signal
The focusing coil is connected to the tilt detection signal and the focus detection signal.
Driven by the difference signal from the error signal.
And an objective lens driving device. Wherein said tilt detection means, the objective lens driving device according to claim 1, wherein an optical sensor mounted on the reflective to the movable body. Wherein said tilt the power supply to the detection means, the objective lens driving device according to claim 1, wherein performed via the rod-like support member. 4. The rod-shaped support member has a circular cross section.
4. The objective lens driving device according to claim 3 , wherein the objective lens driving device is selected from a substantially polygonal shape and an elliptical shape.