JP2601811B2 - Objective lens drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an objective lens driving device, and more particularly to an objective lens driving device in which a supporting method of a movable body including a lens is improved.

(Prior art) In an optical reproducing apparatus using a laser beam, a laser beam is condensed by a lens or the like to detect a signal. However, in order to detect a signal correctly, it is necessary to respond to unevenness or vibration of an information recording medium. Focusing control for focusing the light spot on the medium and tracking control for causing the light spot to follow the signal track are required. In order to perform these controls, an error detection device that detects each error and an actuator (objective lens driving device) that moves the optical system so as to cancel the errors are required.

Conventionally, as this type of objective lens driving device, as shown in FIGS. 5 to 7, the rotation direction of the movable body about the principal axis of inertia and the parallel movement in the direction of the principal axis of inertia make the tracking direction and focusing direction of the objective lens. Or a device which moves the movable body holding the objective lens directly in the two perpendicular directions of the focusing direction and the tracking direction as shown in FIGS. 8 and 9. I was

Here, the specific configuration and operation principle of the two objective lens driving devices will be described below. 5 is a perspective view, FIG. 6 is a sectional view taken along line AA of FIG. 5, FIG. 7 is a sectional view taken along line BB of FIG. 5, and FIG. 8 is a perspective view. FIG. 9 is an exploded perspective view.

The objective lens driving device shown in FIGS. 5 to 7 is configured as follows. That is, a shaft 102 is implanted at the center of the upper surface of a base 101 made of a magnetic material, and
2 is a bearing sleeve 10 which is fitted with the shaft 102 to form a sliding bearing mechanism.
A holding cylinder 104 formed in a cylindrical shape with a bottom is mounted so as to be slidable in the axial direction and rotatable around the axis via 3. A so-called bottom wall 104a of the holding cylinder 104 supports the objective lens 105, and a focusing coil for controlling an axial position on the outer periphery of the cylinder 104b by using the cylinder 104b of the holding cylinder 104 as a coil bobbin. 106 and a tracking coil 107 for controlling the position in the direction around the axis are fixed.

In addition, two inner yokes 108 are pivoted about the shaft 102 at a position facing the inner surface of the bottom wall 104a of the holding cylinder 104 on the upper surface of the base 101 so as to fit into the cylindrical portion 104b of the holding cylinder 104 in a non-contact manner. Protruding symmetrically, and an inner yoke on the outside of the cylindrical portion 104b.
Outer yokes 109 are arranged so as to face the outer surface of 108, respectively, and a permanent magnet 110 magnetized in the axial direction is interposed between the outer yokes 109 and the upper surface of the base 101. Further, a small shaft 111 is erected on the upper surface of the base 101 and at a position facing the inner surface of the bottom wall 104a of the holding cylinder 104, and is formed of, for example, rubber or the like between the small shaft 111 and the bearing cylinder 103. A neutral position setting damper member 112 in the tracking direction is interposed. In FIG. 6, reference numeral 113 denotes a transmission hole provided on the base 101 for guiding light to the objective lens 105 and light from the objective lens 105.

With the above configuration, the position of the holding cylinder 104 is changed in the Y-axis direction in FIG. 5 by the electromagnetic force accompanying the energization control of the focusing coil 106, whereby the focusing control can be performed. In addition, the tracking coil 10
The position of the holding cylinder 104 is rotationally moved in the X direction in FIG. 5 by the electromagnetic force accompanying the energization control to 7, so that tracking control can be performed. These energization controls are performed by a servo system (not shown).

On the other hand, the objective lens driving device shown in FIGS. 8 and 9 is configured as follows. That is, a metal rod fixing plate 212 is provided to protrude upward from the end of the base 211 made of a magnetic material. One end of each of four metal bars 213 parallel to the base 211 is fixed to the metal bar fixing plate 212. A movable body 215 holding the objective lens 214 is fixed to the other end of the metal bar 213. In addition, movable body 2
A focusing coil 216 and a tracking coil 217 are fixed to 15.

Also, two inner yokes 218 protrude from the base 211 so as to be fitted into the focusing coil 216 with a certain gap provided inside. Outside the inner yoke 218, outer yokes 219 are respectively provided at positions facing the inner yoke 218 with the focusing coil 216 and the tracking coil 217 interposed therebetween. On the surface of the outer yoke 219 facing the inner yoke 218,
Each magnet 220 is fixed.

With the above configuration, the movable body 215 can be moved in the Y direction in FIG. 8 by the electromagnetic force accompanying the energization control of the focusing coil 216, thereby performing the focusing control, and energizing the tracking coil 217. The movable body 215 is moved in the X-axis direction in FIG. 8 by the electromagnetic force accompanying the control,
As a result, tracking control can be performed.

However, this type of apparatus has the following problems. That is, in the apparatus shown in FIGS. 5 to 7, the damper member 112 for determining the neutral position of the holding cylinder 104 is
Since it is fixed at a biased position on the opposite side of the objective lens 105 from the boundary 102, a moment force about the orthogonal axis is generated in the holding cylinder 104 when a displacement in the focusing direction is given.
For this reason, a reaction force proportional to the above-described moment is generated in the sliding bearing mechanism that regulates the rotation axis around the orthogonal axis. Since the sliding friction of the sliding bearing mechanism is substantially proportional to the normal reaction, the larger the displacement in the focusing direction, the larger the frictional force acts. Therefore, the relationship between the quasi-static displacement in the focusing direction and the force has a hysteresis characteristic as shown in FIG.

Since the quasi-static displacement has a large hysteresis as described above, there is a problem that it is difficult to pull in the servo when the servo is applied. Further, in order to solve this problem, conventionally, a countermeasure has been taken by increasing the surface accuracy of the bearing mechanism.
This has hindered price decline.

On the other hand, in the apparatus shown in FIGS.
When the objective lens 214 is moved in the tracking direction indicated by the axis, the point of action of the force generated by the tracking coil 217 is matched with the center of gravity of the movable
15 is moved in parallel. However, when the movable body 215 is shifted from the neutral position in the focusing direction, the point of action of the force generated by the tracking coil 217 is the movable body 2
As a result, a rotational force around the axis indicated by the Z axis in the figure was generated. As a result, the objective lens 215 tilts, causing an increase in jitter.

In addition, in the case of supporting by a combination of parallel springs or a parallel spring and a rotary bearing instead of the four wires 213, the restraining force against the rotational displacement around the Z axis is strong, but the movable body also moves from the neutral position in the focusing direction. In the shifted state, basically, a force for rotating the movable body about the Z axis acts. For this reason, although the amount of tilt in the low frequency region is small, tilt vibration is excited in a frequency region near 1 KHz, and as a result, the control operation is unstable.

(Problems to be Solved by the Invention) As described above, in the conventional objective lens driving device, when a displacement in the focusing direction is given, a moment force about an orthogonal axis is generated, and the relation between the quasi-static displacement in the focusing direction and the force is generated. However, there are problems such as the occurrence of hysteresis characteristics, the imbalance in force when the lens is shifted in the focusing direction or the tracking direction, and the tilt of the lens.

The present invention has been made in consideration of the above circumstances, and an object thereof is to suppress a hysteresis characteristic in a relationship between a quasi-static displacement and a force in a focusing direction, and to suppress the hysteresis characteristic in a focusing direction or a tracking direction. An objective lens driving device with a simple configuration that can maintain the balance of force even in the shifted state and prevent the lens from tilting beforehand, facilitating the servo pull-in operation at the start of the control operation and obtaining stable control characteristics. Is to provide.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is that two pairs of support rods having a parallel relationship are provided.
A pair is used, these are arranged in an intersecting relationship, and the movable body is rotationally driven around the intersecting point with respect to the movement in the tracking direction.

That is, the present invention provides an objective lens, a movable body for holding the objective lens, and moving and displacing the movable body with respect to a fixed portion in at least an optical axis direction of the objective lens or a direction orthogonal to the optical axis direction. An objective lens driving device having driving means, wherein a support for supporting the movable body with respect to the fixed portion is disposed so as to be parallel to each other in a plane parallel to the optical axis of the objective lens, and one end of each of the supports is provided. A first support rod pair each having a side fixed to the movable body and the other end fixed to the fixed portion, each of which is cantilevered; and the first support rod parallel to the optical axis of the objective lens. The second support rods are arranged so as to be parallel to each other in a plane different from the pair, and one end of each is fixed to the movable body and the other end is fixed to the fixing part, so that each of the second support rods is cantilevered. A plane including the pair of first support rods and a plane including the pair of second support rods intersect with each other, and a line of intersection is formed between the one end side and the other end side. By doing so, the intersection line is made to coincide with the rotational inertia center of the movable body.

(Operation) With the above configuration, the plane formed by the pair of the first support rods and the plane formed by the pair of the second support rods intersect with each other. It is defined as a direction parallel to the plane and a direction of rotation about the intersection of the two planes. Therefore, regarding focusing, by moving the movable body in a direction parallel to each of the above-described planes, the objective lens can be driven in a direction perpendicular to the optical recording medium. Further, with respect to tracking, the objective lens can be driven in the radial direction of the optical recording medium by rotating the movable body about the intersection line.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

1 is a plan view showing a schematic configuration of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line CC in FIG. 1, and FIG. 3 is a perspective view showing the device. It is.

In these figures, reference numeral 11 denotes a base formed of a magnetic material. At the end of the base 11, a support rod fixing plate 12a,
12b protrudes upward. One ends of support bars 13a and 13b parallel to each other in a plane perpendicular to the base 11 are fixed to the support bar fixing plate 12a. Similarly, one ends of support rods 14a and 14b parallel to each other in a plane orthogonal to the base 11 are fixed to the support rod fixing plate 12b. The plane formed by the first pair of support rods 15 formed by the support rods 13a and 13b and the plane formed by the second pair of support rods 16 formed by the support rods 14a and 14b correspond to the base 11 Are arranged to intersect approximately at the center.

As described above, the support rods 13a, 13b, 14a, 14b are held in a state of being cantilevered by the support fixing plates 12a, 12b, respectively. And other parts of the support rods 13a, 13b, 14a, 14b,
For example, no binding force acts on the intersection (intersection) between the support bars.

A movable body 18 holding an objective lens 17 is fixed to the other end of the pair 15 of the first support rod and the pair 16 of the second support rod. Here, the center of inertia of the movable body 18 and the intersection of the two planes formed by the pair of first and second support rods 15 and 16 match each other. Further, the objective lens 17 is arranged at a position away from the center of inertia by a predetermined distance. Further, focusing coils 19a and 19b and tracking coils 20a and 20b are fixed to the movable body 18 at positions symmetrical to each other with respect to the center of inertia of the movable body 18.

On the other hand, the base 11 has a focusing coil
The inner yokes 21a and 21b protrude so that the inner yokes 21a and 21b are inserted with a certain gap provided inside the 19a and 19b. Outside the inner yokes 21a and 21b, a focusing coil 19 is provided.
Outer yokes 22a, 22b are provided at positions facing the inner yokes 21a, 21b with the a, 19b and the tracking coils 20a, 20b interposed therebetween. Then, the inner yoke 2 of the outer yokes 22a and 22b
Magnets 23a and 23b are fixed to the surfaces facing 1a and 21b, respectively.

With such a configuration, the focusing coil 19
The movable body 18 is moved in the Y direction in FIG. 2 by the electromagnetic force accompanying the energizing control of the a and 19b, thereby performing the focusing control, and is movable by the electromagnetic force accompanying the energizing control of the tracking coils 20a and 20b. The body 18 is rotated around the Y-axis in FIG. 2 so that tracking control can be performed. In this case, since the first support rod pair 15 and the second support rod pair 16 are used as supports for supporting the movable body 18 with respect to the base 11, the following effects can be obtained. .

That is, the rotation and the slip around one axis are controlled by the four support rods 13a, 13
Since it is realized by b, 14a, and 14b, frictional force does not act as in the case of using a bearing. Therefore, the relationship between the quasi-static displacement in the focusing direction and the force is linear as shown in FIG. 4, and has a characteristic without hysteresis as shown in FIG. Since there is no hysteresis in the quasi-static displacement as described above, it is possible to easily perform pull-in when servo is applied.

The movement of the objective lens 17 in the tracking direction is realized by the rotational movement of the movable body 18 due to a couple generated by the tracking coils 20a and 20b. This couple does not change even when the relative position between the tracking coils 20a, 20b and the timing circuit changes due to displacement in the focusing direction or displacement in the tracking direction. Further, the two pairs of support rods 15 and 16 which intersect each other at the center of inertia of the movable body 18 are provided with an appropriate spring property for the parallel movement of the movable body 18 in the focusing direction and the rotational movement of the movable body 18 around the center axis of inertia. Is shown. Therefore, even when the objective lens 17 is moved in the tracking direction while the movable body 18 is shifted from the neutral position in the focusing direction, such as when the movable body 18 is moved in parallel in two directions at right angles, even when the objective lens 17 is moved around the Z axis, In this configuration, a force for rotating the movable body 18 does not basically act, so that an extremely stable control operation can be realized.

In addition, since the structure is such that the two pairs of support rods 15 and 16 cross each other, the panel characteristics of each support rod are extremely strong except in the Y direction and the rotation direction around the center axis of inertia, and the movable The position of the member 18 can be stably regulated. Further, as compared with the conventional apparatus shown in FIGS. 8 and 9, the number of parts is substantially the same, and the configuration is not complicated.

The present invention is not limited to the above-described embodiment. For example, the intersection of each plane formed by the pair of the first and second support rods coincides with the rotational inertia center of the movable body. It is desirable, but it is not always necessary to match exactly. The conditions such as the material, length, and diameter of the support rod may be appropriately determined according to the weight of the movable body and the like. For example, as a material of the support rod, a carbon fiber composite material, an elastic alloy material, a stainless steel alloy, and a copper alloy can be used in addition to a general metal rod. Further, the arrangements of the focusing coil and the tracking coil are not limited to those shown in FIG. 1 and can be appropriately changed according to the specifications. Moreover,
The above embodiments are all moving coil types in which a drive coil is arranged on the movable body side and a magnet is arranged on the fixed part side.
The present invention is not limited to this. That is, a moving magnet type in which a magnet is arranged on the movable body side and a drive coil is arranged on the fixed part side may be used. It should be noted that the moving magnet type has advantages such as excellent operating characteristics because there is no coil wiring or the like on the movable body side.
In addition, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, the movable body is supported by two sets of parallel support rods that intersect each other at the center of inertia of the movable body. The advantage of the method supported by parallel support rods is that there is no hysteresis in the relationship between the quasi-static displacement and force in the focusing direction, and the advantage that the tilting of the movable body is not excited, which is the advantage of the shaft sliding method. It is possible to realize an objective lens driving device having both functions, and its usefulness is enormous.

[Brief description of the drawings]

1 to 3 are diagrams for explaining a schematic configuration of an objective lens driving device according to an embodiment of the present invention, wherein FIG. 1 is a plan view, and FIG. 2 is a view taken along a line CC of FIG. FIG. 3 is a sectional view, FIG. 3 is a perspective view, FIG. 4 is a diagram showing the driving characteristics in the focusing direction of the above-described embodiment, and FIGS. 5 to 7 are diagrams for explaining a first conventional example. 6 is a perspective view, FIG. 6 is a sectional view taken along line AA of FIG. 5, FIG. 7 is a sectional view taken along line BB of FIG. 5, and FIGS. 8 and 9 are second conventional examples. 8 is a perspective view, FIG. 9 is an exploded perspective view, and FIG. 10 is a diagram showing a driving characteristic in a focusing direction in a first conventional example. 11 ... base, 12a, 12b ... support rod fixing plate, 13a, 13b, 14a, 14b
... support rod, 15 ... first support rod pair, 16 ... second support rod pair, 17 ... objective lens, 18 ... movable body, 19a, 19b ... focusing coil, 20a, 20b ... tracking coil, 21a, 21b ... inner yoke, 22a, 22b ... outer yoke, 23a,
23b… A magnet.

Claims (2)

(57) [Claims] An objective lens, a movable body for holding the objective lens, and the movable body displaced relative to a fixed part in at least an optical axis direction of the objective lens or a direction orthogonal to the optical axis direction. An objective lens driving device having driving means, wherein a support for supporting the movable body with respect to the fixed portion is arranged so as to be parallel to each other in a plane parallel to the optical axis of the objective lens, and one end of each of the supports is provided. A pair of first support rods each having a side fixed to the movable body and the other end fixed to the fixing portion, each of which is cantilevered; and the first support rod being parallel to the optical axis of the objective lens. A second support in which the rods are cantilevered by being arranged parallel to each other in a plane different from the pair of rods, one end of each being fixed to the movable body and the other end being fixed to the fixing part; rod And a plane including the pair of the first support bars and a plane including the pair of the second support bars intersect with each other, and the line of intersection intersects the one end side and the other end side. The objective lens driving device, wherein the intersection line is made to coincide with the rotational inertia center of the movable body. 2. The patent according to claim 1, wherein said pair of said first support rods and said pair of said second support rods are arranged in parallel relation to a plane orthogonal to the optical axis of said objective lens. The objective lens driving device according to claim 1.