JPH0194538A - Optical pickup - Google Patents

Abstract

PURPOSE:To prevent an adverse effect on the tracking positioning control of an objective lens due to a friction force to occur at an objective lens shifting mechanism by energizing the objective lens shifting mechanism in the orthogonal direction to a tracking movement direction. CONSTITUTION:When a driving current is supplied to a driving coil 26, a lens holder 25 shifts in a focusing direction according to its polarity (a direction) and strength, and a position in the focusing direction of an objective lens 5 is decided. Further, when the driving current is supplied to a driving coil 29, the lens holder 25 rotates sin the tracking direction around a bearing 22 according to its polarity and strength, and the position in the tracking direction of the objective lens 5 is decided. Since a tracking bobbin 30 is composed of a magnetic substance, a suction force is generated between the bobbing 30 and a permanent magnet 32 facing the tracking bobbin 30, and the bearing 22 adheres on an opposite side to the working direction of the suction force, and the play between an axis 21 and the bearing 22 is eliminated. Thus, the adverse effect on the tracking positioning control of the objective lens is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical pickup that positions a light beam on a recording track formed on an optical storage medium such as an optical disk.

[Prior Art] In recent years, an optical disk storage device has been proposed that uses an optical disk in which an optical storage medium is formed into a disk shape as a storage medium. On the data storage surface of this optical disk, a recording track with a fine structure of, for example, a track width of about 1 μm and a track pitch of about 2 μm is formed, and a laser beam with a spot diameter of about 1 μm is irradiated onto this recording track. irradiate.

Then, while rotating the optical disk, data is stored by modulating the intensity of the laser beam in accordance with the data to be recorded, and also detects changes in the level of reflected light of the laser beam from the data storage surface. The stored data is played back.

In this way, the part that follows the laser beam to the recording track and narrows the spot diameter to a predetermined size is
This is an optical pickup, and an example of its schematic configuration is shown in FIG.

In the figure, laser light output from a semiconductor laser device 1 is converted into parallel light by a coupling lens 2, transmitted through a polarizing beam splitter 3, and then passed through a quarter-wave plate 4.
After being polarized, the light is focused by an objective lens 5 and focused onto a recording track of an optical disk 6.

The reflected light from the optical disk 6 is again converted into parallel light via the objective lens 5, further polarized by the 174-wave plate 4, reflected by the polarizing beam splitter 3, and divided into four parts by the lens 7. An image is formed on the light receiving element 8.

The objective lens 5 is also provided with a tracking mechanism for positioning the objective lens 5 in the radial direction of the optical disc 6, and a focusing mechanism for focusing. Note that hereinafter, the tracking mechanism and focusing mechanism are collectively referred to as an objective lens moving mechanism.

Then, a servo control unit (not shown) detects the position error and focus error of the laser beam on the recording track based on the output signal of the four-division light receiving element 8, and also detects the position error and focus error of the laser beam on the recording track according to the detection signal of the error. The focusing mechanism is controlled to move the objective lens 5 in a direction that reduces the positional deviation and focus deviation of the laser beam on the recording track. Further, recording data is extracted from the output signal of the four-division light-receiving element 8.

Now, the focusing mechanism attached to the objective lens 5 is one in which a lens holder supporting the objective lens 5 is moved back and forth in the focusing direction by a linear motor or a voice coil, etc., for boat fishing. Further, as a tracking mechanism, a linear motor, a voice coil, or the like is used that causes the focusing mechanism to reciprocate in an arc shape in the tracking direction.

FIG. 6 shows a conventional example of an objective lens moving mechanism for moving an objective lens in such an optical pickup.

The holder 10 that houses and holds the objective lens 5 is held between a pair of leaf springs 11.12, the other ends of these leaf springs 11.12 are fixed to a shaft 13, and the lower end of the shaft 13 is It is supported by a bearing 15 attached to a base member 14 of the objective lens moving mechanism.

Further, a leaf spring 17 is fixed to the upper end of the support member 16 formed upright from the base member 15, and a bearing 18 is fixed to the other end of the leaf spring 17. The upper end portion of the shaft 13 is received by this bearing 18 .

In this way, the objective lens 5 is supported so as to be able to move in a circle around the axis 13. Further, the shaft 13 is biased from above by the leaf spring 17, and the shaft 13 and the bearing 15 are
18 is removed.

Further, a light emitting diode 19 linked to the shaft 13 is provided, and a semiconductor device detection element 20 is provided on the base member 14 facing the light emitting diode 19. Based on the output signal of this semiconductor device detection element 20, the objective lens 5 is The displacement from the neutral position of circular motion is detected.

However, such conventional devices have the following disadvantages.

That is, in order to eliminate play between the shaft 13 and the bearings 15, 18, the leaf spring 17 applies a biasing force in the longitudinal direction of the shaft 13, but between the shaft 13 and the bearings 15, 18, When viewed microscopically, slippage occurs, and its biasing force causes a frictional load in the rotational direction of the shaft 13, increasing the load on the tracking drive mechanism and adversely affecting tracking positioning control. There is also a risk that it may cause

[Purpose] The present invention has been made in order to eliminate the disadvantages of the prior art, and to solve the problem of tracking positioning control of an objective lens caused by frictional force generated in the objective lens moving mechanism when moving in the tracking direction. The purpose is to provide an optical pickup that can prevent adverse effects.

[Structure] In order to achieve this object, the present invention includes a biasing means for biasing the objective lens moving mechanism in a direction perpendicular to its tracking movement direction.

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

1 and 2 show an objective lens moving mechanism according to an embodiment of the present invention. Note that this objective lens moving mechanism is used in an optical pickup similar to that shown in FIG.

In the figure, a shaft 21 is fixed upright on the base 2° of the objective lens moving mechanism, and a bearing 22 is attached to this shaft 21.
is rotatably mounted.

A pair of leaf springs 23 and 24 are attached to the upper and lower surfaces of the bearing 22, and a lens holder 25 that holds the objective lens 5 is fixed to the other ends of the leaf springs 23 and 24. , the optical axis of the objective lens 5 and the upright direction of the axis 21 are parallel to each other.

A driving coil 26 that serves as a driving source for the focusing mechanism and constitutes a near motor is wound around the lens holder 25, and two holes 25a provided outside the leaf springs 23 and 24 are wound around the lens holder 25. , 25b includes a yoke 27 of a magnetic circuit member 27, 28 which is disposed on the base 20 and constitutes a focusing mechanism linear motor.
a, 28a is inserted.

Further, a tracking bobbin 30 is attached to the end of the lens holder 25 on the opposite side to the direction of extension of the leaf springs 23 and 24, and a tracking bobbin 30 is attached to the drive coil 29, which serves as a drive source for the tracking mechanism and constitutes a near motor. Base 2
A tracking yoke 31 that is raised from zero has a tracking mechanism and a permanent magnet 3 that constitutes a linear motor.
2 are arranged. This causes the tracking bobbin 30 and the permanent magnet 32 to face each other.

The mounting holes 33, 34, 35, and 36 are for mounting this objective lens moving mechanism to the optical pickup, and the mounting holes 33, 34, 35, and 36 are for mounting the objective lens moving mechanism to the optical pickup. The transmission section 37 is for passing a laser beam for data recording/reproduction, and the deflection prism 38 is for bending the laser beam toward the objective lens 5.

Moreover, position regulating members 39 and 40 for regulating the position of the bearing 22 are attached to the upper and lower ends of the shaft 21.

With the above configuration, when a drive current is supplied to the active coil 26, the lens holder 25
moves in the focusing direction, thereby determining the position of the objective lens 5 in the focusing direction.

Further, when a drive current is supplied to the drive coil 29, the lens holder 25 rotates in the tracking direction around the bearing 22 depending on the polarity and strength of the drive current, thereby determining a position of the objective lens 5 in the tracking direction. Ru.

In this way, the objective lens 5 is moved in the focusing direction and the tracking direction, respectively.

Now, the tracking bobbin 30 is made of a magnetic material, and therefore, an attractive force of, for example, 10,100 (or more) is generated between the tracking bobbin 30 and the permanent magnet 32 facing it.

As a result, as shown in FIG. 3, the bearing 22 comes into close contact with the shaft 21 on the side opposite to the acting direction F of this suction force, so that play caused by the dimensional tolerance between the shaft 21 and the bearing 22 is eliminated. Ru.

By the way, it is conceivable that a frictional force is generated in the tracking direction of the objective lens 5 due to the action of this attraction force, but normally, the displacement of the objective lens 5 in the tracking direction is about several lOμm, and the rotation angle is When converted to 10', such a circular motion is realized by the rolling motion of the shaft 21 and the bearing 22, so that the shaft 21
Since the frictional force between the bearing 22 and the bearing 22 is very small, this frictional force does not have an adverse effect on the tracking positioning control of the objective lens 5, etc.

Further, in such an objective lens moving mechanism, a force of, for example, about 10 (g) acts as a thrust force in the focusing direction.

On the other hand, the coefficient of friction in the axial direction that occurs between the shaft 21 and the bearing 22 is about 0.2, for example, when the material of the shaft 21 is stainless steel and the material of the bearing 22 is resin.
Furthermore, as mentioned above, since the magnitude of the suction force acting in the direction perpendicular to the shaft 21 is about too (g), the frictional force in the axial direction generated between the shaft 21 and the bearing 22 is about 20 (g). It will be about. Therefore, even if the objective lens 5 is moved in the focusing direction and an axial thrust is applied to the bearing 22, the frictional force acting between the shaft 21 and the bearing 22 is greater, so the bearing 22 is Movement in the direction, vibrations occurring between the shaft 21 and the bearing 22, etc. are prohibited.

Therefore, regulating the position of the bearing 22 in the vertical direction only needs to be considered when a shock is applied during transportation, etc.
Since the accuracy may be rough, the position regulating members 39 and 40 can sufficiently achieve this, and there is no need to apply force using a leaf spring or the like. .

Further, as shown in FIG. 4, when the lengths of the tracking bobbin 30 and the permanent magnet 32 are made the same, the tracking bobbin 30, the yoke 31. The purgance of the magnetic circuit formed by the permanent magnet 32 is maximum when the tracking bobbin 30 directly faces the permanent magnet 32.

As a result, when the supply of immediate current to the drive coil 29 is stopped, the tracking bobbin 30 always returns to the state where it directly faces the permanent magnet 32, that is, to the neutral position that is the reference position for movement in the tracking direction.

Therefore, this embodiment does not require a mechanism for detecting the neutral position, which was conventionally necessary.

The objective lens moving mechanism can be made smaller and lighter, contributing to miniaturization of the optical pickup and cost reduction.

In addition, in this embodiment, the shaft 21 is fixed upright to the base 20.
The bearing 22 is inserted into the base 20, and the attraction force between the tracking bobbin 3o and the permanent magnet 32 causes the bearing 22 to align with the shaft 21, and it is relatively easy to accurately stand the shaft 21 upright on the base 20. , assemblability of parts, and
Assembly accuracy is improved.

In the above-mentioned embodiment, a biasing force in a direction perpendicular to the direction of movement of the objective lens is generated by magnetic force, but a similar biasing force can also be generated by other means, such as a means using an elastic member. The means can be realized.

Further, although the above-mentioned embodiments were implemented in an optical pickup applied to an optical disk drive device, the present invention can be similarly applied to an optical pickup that records/reproduces data on other optical storage media. can.

[Effect] As explained above, according to the present invention, since the biasing means for biasing the objective lens moving mechanism in a direction perpendicular to its tracking movement direction is provided, the objective lens does not move when it moves in the tracking direction. The effect is that the frictional force generated in the mechanism is extremely small, and the tracking positioning control of the objective lens is not adversely affected.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view showing an objective lens moving mechanism according to an embodiment of the present invention, Fig. 2 is a schematic sectional view thereof, and Fig. 3 is a schematic sectional view for explaining the mode of movement between the support and the bearing. FIG. 4 is a schematic diagram for explaining the dimensional relationship between the tracking bobbin and the permanent magnet. FIG. 5 is a schematic configuration diagram showing an example of an optical pickup;
FIG. 6(a) is a schematic plan view showing a conventional example of an objective lens moving mechanism, and FIG. 6(b) is a schematic sectional view thereof. 5... Objective lens, 20... Base, 21... Shaft, 22... Bearing, 23, 24... Leaf spring, 25...
・Lens holder, 26° 29... Drive coil, 27
．． 28... Magnetic circuit member, 30... Tracking bobbin, 31... Yoke, 32... Permanent magnet. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An objective lens moving mechanism that positions the light beam on the recording track by linearly moving the objective lens in the focal direction and circularly in the tracking direction to form an image of the light beam on a recording track formed on an optical storage medium. 1. An optical pickup comprising: a biasing means for biasing the objective lens moving mechanism in a direction perpendicular to its tracking movement direction.