JPH05128561A - Tracking actuator of optical disk drive - Google Patents

Abstract

PURPOSE:To provide a tracking actuator of an optical disk drive which can be made compact in size without accompanying the shift of an optical axis. CONSTITUTION:This tracking actuator is comprised of a parallel leaf spring mechanism 41 which translates a galvanomirror 47 in a perpendicular direction Z to an optical disk 3, a leaf spring member 46 mounted at the front end of the mechanism 41 for turning the galvanomirror, and an actuator 48 for working the force to the front end of the leaf spring member. The galvanomirror 47 is mounted at the front end of the leaf spring member 46. As the actuator 48 is driven, the parallel leaf spring mechanism 41 and the leaf spring member 46 are bent, so that the galvanomirror 47 is translated and turned. The galvanomirror 47 is so adapted as to shift actually in the same manner as when it turns and shifts around a virtual axis 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking actuator for an optical disk device, and more particularly to a tracking actuator using a galvano mirror.

In a tracking actuator,
In order to improve the tracking accuracy, it is preferable that the optical axis of reflected light from the optical disc does not shift and that the optical disc device be small in size in order to miniaturize it.

[0003]

2. Description of the Related Art FIG. 8 shows an example of a conventional tracking actuator.

In the figure, 1 is a galvanometer mirror, 2 is an objective lens, 3 is an optical disk, and 4 is a split sensor.

The actuator 5 is driven by a tracking control signal from the split sensor 4, and the galvanometer mirror 1 is rotated about a central axis 6.

The beam spot on the optical disc 3 is separated by a distance ε.
When the galvanometer mirror 1 is rotated from the position shown by the broken line to the position shown by the solid line to move it, the optical path becomes as shown by the solid line, and the reflected light 10 reflected and returned by the optical disk 3 is returned.
Is the dimension δ with respect to the incident light 11 on the galvanometer mirror 1.
However, the tracking control signal is offset, and the tracking accuracy is impaired.

FIG. 9 shows another example of a conventional tracking actuator.

Reference numeral 20 denotes a galvanometer mirror, and a rotation center axis 21 thereof passes through an image side focal point 22 of the objective lens 2 and is an image side focal plane 24 which is a plane perpendicular to an optical axis 23 of the objective lens 2.
It is located above.

When the actuator 5 is driven, the galvanometer mirror 20 rotates about the shaft 21 as shown by the broken line.

The incident light 25 is reflected by the galvano mirror 20 and is launched.

The rising light 26 passes near the image-side focal point 22 and, after passing through the objective lens 2, is vertically incident on the optical disc 3 as indicated by reference numeral 27. Therefore, the reflected light 2
8 passes through the image-side focal point 22, and the reflected light 29 reflected by the galvanometer mirror 20 matches the incident light 25. That is, the optical axis shift is unlikely to occur.

Therefore, the tracking control signal has no offset, and the tracking accuracy is improved.

[0013]

Depending on the optical disk device, it may be necessary to dispose the galvano mirror farther from the optical disk 3 as indicated by reference numeral 30 in FIG.

In this case, the central axis of rotation of the galvanometer mirror 30 is separated from the objective lens 2 in the lateral direction, as indicated by reference numeral 31.

Therefore, the tracking actuator becomes large in the lateral direction.

Further, the weight of the galvano mirror 30 becomes heavy, which is disadvantageous in terms of control.

It is an object of the present invention to provide a tracking actuator for an optical disk device, which can be miniaturized without causing an optical axis shift.

[0018]

According to a first aspect of the present invention, there is provided a tracking actuator for an optical disk device using a galvano mirror arranged to face an optical disk, the tracking actuator being arranged in a direction parallel to the optical disk and having the galvano mirror at the tip thereof. A leaf spring member that supports the optical disc in a posture inclined by 45 degrees and that translates and rotates the galvanomirror in a direction perpendicular to the optical disc, and a leaf spring member that is arranged in a direction parallel to the optical disc. , The base side of the leaf spring member is fixed to its tip,
A parallel leaf spring mechanism that translates the galvano-mirror in a direction perpendicular to the optical disc by the deflection and a tracking control signal drive a force to the tip of the leaf spring member in a direction perpendicular to the optical disc. The actuating actuator is used, and the galvanometer mirror is translated and rotated by the bending of the parallel leaf spring mechanism and the bending of the leaf spring member.

According to a second aspect of the present invention, the parallel leaf spring mechanism of the first aspect is arranged on the left and right sides, and the leaf spring members are extended between the parallel leaf spring mechanisms in the opposite direction. It is configured as follows.

[0020]

In the invention of claim 1, the parallel leaf spring mechanism and the leaf spring member act so as to reduce the space occupied by them, and the galvanometer mirror is centered on a point on the image side focal plane of the objective lens. It acts to displace so as to rotate.

According to the second aspect of the present invention, the leaf spring member is extended in the direction opposite to the direction in which the parallel leaf spring mechanism is extended. Acts to fit in.

[0022]

1 and 2 show a tracking actuator 40 of an optical disk device according to a first embodiment of the present invention.

In the figure, parts corresponding to those shown in FIGS. 8 and 9 are designated by the same reference numerals.

Reference numeral 41 denotes a parallel leaf spring mechanism, one end of which is fixed to the vertical base portion 42a of the base 42 and is arranged in a direction parallel to the optical disk 3 so as to have the first and second leaf springs 4.
3 and 44, and a connecting member 45 that connects the tips of the first and second leaf springs 43 and 44.

Reference numeral 46 denotes a plate spring member, which is connected to the connecting member 45 on the base side thereof, is oriented parallel to the optical disk 3, and extends from the parallel plate spring mechanism 41 in the distal direction. A galvano mirror 47 is attached to the tip of the optical disc 3
It is fixed in a posture inclined at 45 degrees with respect to.

Reference numeral 48 denotes an actuator, which is fixed on the horizontal base portion 42b and applies a force P to the tip of the leaf spring member 46 in the direction Z perpendicular to the optical disk 3.

Reference numeral 50 denotes a virtual axis line, which is the galvanometer mirror 4.
An extension surface 49 of 7 is an axis intersecting the image-side focal plane 24 of the objective lens 2.

When the actuator 48 is driven by the tracking control signal, the parallel leaf spring mechanism 41 and the leaf spring member 46 bend as shown in FIG.

The parallel leaf spring mechanism 41 bends by δ _A , the leaf spring member 46 bends by δ _B , and tilts by θ.

The galvanometer mirror 47 has δ _A + δ in the Z direction.
_B translates to reach the position indicated by reference numeral 47b, further rotates by θ, and finally reaches the position indicated by reference numeral 47a.

This position corresponds to the galvano mirror 47 in FIG.
Is substantially the same as the position when is rotated about the virtual axis 50.

Therefore, as shown in FIG. 9, the reflected light 6
There is no optical axis deviation with respect to the incident light 61 of 0, a tracking control signal having no offset is obtained, and tracking control is performed accurately.

Further, since it does not actually have a central axis of rotation,
Even when the galvano mirror 47 is arranged apart from the objective lens 2, the size of the tracking actuator does not increase, and the tracking actuator is small in size as in FIG.

Further, since the size of the galvanometer mirror 47 is small and the weight thereof is light, the tracking control is well performed.

Next, the galvanometer mirror 47 is moved to the virtual axis 50.
The reason for the displacement so as to rotate around will be described.

In FIG. 4, when the distance between the incident light 61 and the image-side focal plane 24 is L, AB is

[0037]

[Equation 1]

[0038]

When ∠BAC is θ, since θ is minute, BC is

[0040]

[Equation 2]

It becomes

BD, that is, the translation amount δ of the galvano mirror 47 is δ = 2Lθ.

That is, δ and θ have a proportional relationship.

On the other hand, regarding the parallel leaf spring mechanism 41 and the leaf spring member 46, the bending amount and the inclination angle when the force P is applied by the actuator 48 are as follows.

The length of the first and second leaf springs 43 and 44 is a, and the length of the leaf spring member 46 is b. Further, the first and second leaf springs 43, 44 and the leaf spring member 46 both have a longitudinal elastic modulus of E and a second moment of area of I.

The bending amount δ _A is Pa ³ / 24EI, the bending amount δ _B is Pb ³ / 3EI, and the inclination angle θ is Pb ² / 2EI.

Therefore, the translation amount δ of the mirror 20 (= δ _A +
δ _B ) is P (a ³ + 8b ³ ) / 24EI.

If this is represented by θ,

[0049]

[Equation 3]

It becomes

Similar to the equation, δ and θ have a proportional relationship.

Comparing the equations with the equations,

[0053]

[Equation 4]

A and b are determined so as to satisfy the above condition.

In the tracking actuator shown in FIGS. 1 and 2, the dimensions are determined as described above, and the mirror 20 is displaced in the same manner when it is pivotally displaced about the virtual axis 50.

FIG. 5 shows a tracking actuator 80 of an optical disk device according to the second embodiment of the present invention.

FIG. 6 shows the main part of the tracking actuator in FIG. 5, and FIG. 7 shows it in exploded form.

In the parallel leaf spring mechanism 81, a pair of leaf springs 82 to 85 are arranged on the left and right sides, and the tips of the leaf springs 82 to 85 are connected to each other by a coupling member 86.
It is a structure commonly connected by.

The leaf spring member 87 is fixed to the connecting member 86 and extends toward the fixing portion side of the leaf spring 82 or the like, that is, in the direction opposite to the leaf spring 82 or the like.

The galvano mirror 20 is fixed to a mirror base 88 having a substantially triangular prism shape, and the base 88 is fixed to the tip of the leaf spring member 87.

The actuator 90 is composed of a yoke 91, a magnet 92, a coil 93, etc., and applies a force P to the mirror base 88.

When the actuator 90 is driven, the parallel leaf spring mechanism 81 and the leaf spring member 87 bend as in the case of the above-described embodiment, and the mirror 20 is displaced so as to rotate about the virtual axis 50.

In the present embodiment, the leaf spring member 8
Since 7 extends inside the parallel leaf spring mechanism 81, the tracking actuator 40 is smaller than that of the first embodiment.

[0064]

As described above, according to the first aspect of the invention, the size can be reduced while preventing the optical axis shift.

According to the second aspect of the invention, the size can be further reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a tracking actuator of an optical disk device of the present invention.

FIG. 2 is a perspective view showing a tracking actuator in FIG.

FIG. 3 is a diagram showing a state when the tracking actuator of FIG. 1 is in operation.

FIG. 4 is a diagram for explaining the displacement of the galvanometer mirror in FIG.

FIG. 5 is a diagram showing a second embodiment of the tracking actuator of the optical disk device of the present invention.

FIG. 6 is a perspective view showing a tracking actuator in FIG.

7 is an exploded perspective view of the tracking actuator of FIG.

FIG. 8 is a diagram showing an example of a conventional tracking actuator.

FIG. 9 is a diagram showing another example of a conventional tracking actuator.

[Explanation of symbols]

 40,80 Tracking actuator 41,81 Parallel leaf spring mechanism 42 Base 43 First leaf spring 44 Second leaf spring 45,86 Coupling member 46,87 Leaf spring member 47 Galvano mirror 48,90 Actuator 49 Extension surface 50 Virtual Axis line 60 Incident light 61 Reflected light 82 to 85 Leaf spring 88 Mirror base 91 Yoke 92 Magnet 93 Coil

Claims (2)

[Claims] 1. A tracking actuator of an optical disk device using a galvano mirror (47) arranged opposite to an optical disk (3), the tracking actuator being arranged in a direction parallel to the optical disk and having the galvano mirror at the tip thereof with respect to the optical disk. A leaf spring member (46, 87) that supports the galvano-mirror in a posture inclined by 45 degrees and translates and rotates the galvano-mirror in a direction perpendicular to the optical disc is arranged in a direction parallel to the optical disc. , A parallel plate spring mechanism (41, 81) for fixing the base side of the plate spring member to its tip, and translating the galvanomirror in a direction perpendicular to the optical disk by its deflection, and driven by a tracking control signal, Force is applied to the tip of the leaf spring member in a direction perpendicular to the optical disc. A tracking actuator for an optical disk device, comprising an actuator (48, 90), wherein the galvanomirror is translated and rotated by the bending of the parallel leaf spring mechanism and the bending of the leaf spring member. .. 2. The parallel leaf spring mechanism (90) according to claim 1 is arranged on the left and right sides, and the leaf spring member (81) is provided between the parallel leaf spring mechanisms (90) in the opposite direction. A tracking actuator for an optical disk device, which is configured to extend.