JPS58185036A - Optical pickup - Google Patents

Abstract

PURPOSE:To perform easy and accurate control of a holding barrel of an objective lens, by holding the holding barrel movable in both tracking and focusing directions while adsorbing or attracting magnetically the holding barrel to a static magnetic path and then performing the position control of the holding barrel by controlling the current of a control electromagnet. CONSTITUTION:An objective lens 12 is held by a holding barrel 13. An outer barrel 11 is made of a magnetic matter and the magnetic flux of a magnet 20 pierces through the barrel 13. The barrel 13 can move in both tracking and focusing directions by means of a bearing 19 containing a steel ball 17 and guide grooves 14 and 18. The barrel 13 is attracted to the bearing 19 by the magnetic force. An electromagnet 22 has four projected magnetic poles and controls the current supplied to each of coils 25a-25d to move the barrel 13. A magnetic fluid 26 is injected to a magnetic gap in order to increase the density of magnetic flux as well as to control the mobile part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to an optical pickup, and particularly to an optical pickup ζ suitable for playing back audio discs, video discs, and the like.

[Technical background of the invention and its problems]

Put away audio discs, video discs, etc.

When reproducing recorded information, in order to correctly converge the reading light beam onto the information track on the disk surface,
It is necessary to control the objective lens of the optical system in two directions: focusing control in the optical axis direction and tracking control in the lateral direction of the information track.

Focusing needs to respond with a maximum stroke of about 1 to 2 inches in order to follow the waveform deformation of the disk. Further, since the information track is formed in a spiral shape on the disk, tracking must respond quickly with a stroke of 01 to 0.2H in order to correct the deviation between the center of curvature of the track and the center of rotation of the disk.

FIG. 1 shows a row of conventional optical pickups with such an intention. This pickup includes a stationary part 1 and a movable holding cylinder 2.

A lens 3 and the like are attached to the holding tube 2. Hold 1vI
Reference numeral 2 denotes a pair of parallel plate springs 5a so that the movable frame 4 can move only in one direction (left-right direction in the figure).

5b, and the movable pedestal 4 is further supported by a pair of parallel leaf springs 6a and 6b provided above and below so that it can move only in the direction of the axis of the holding cylinder 2.

The stationary part 1 includes a magnetic circuit 7 made of a magnetic material, in which an annular magnetic gap 7' is formed. The movable frame 4 is provided with a coil 8 for driving it, and this coil 8 is arranged within the magnetic gap 7'. The movable pedestal 4 is driven and controlled by the electromagnetic force received from the magnetic circuit 7 in the same manner as in the case of a normal loudspeaker 2 by passing a current through the coil 8.

On the other hand, in order to drive the holding cylinder 2, a pair of suction iron pieces 9m and 9b are provided on both sides of the tip thereof, and a pair of electromagnets 101. IQb is provided. Therefore, by energizing these electromagnets 10m and 10b, the holding cylinder 2 is driven and controlled by the magnetic attraction force with the attraction iron pieces 9a and 9b.

In this way, the holding cylinder 2 can be driven relative to the stationary part 1 in two dimensions in the direction of the optical axis and in the direction orthogonal to the optical axis. According to the configuration shown in Figure @1, the important factors that determine the focusing and tracking drive control of the holding cylinder 2 are mainly the leaf springs 5a, 5b, and 6.
m, 6b, it is difficult to make the holding cylinder 2 of the objective lens 3 respond at a high speed, and in the case of an optical pickup, it is necessary to control the characteristics with a motion of several fG (z). However, there is a problem in that the quality control and shape control of the material must be strictly controlled.Also, although it is good at relatively low frequencies, at high frequencies resonance may occur and control becomes difficult, and resonance countermeasures are required. There were drawbacks such as the need for

[Purpose of the invention]

This invention was made based on the above circumstances.

The object of the present invention is to provide an optical pickup in which quality control and shape control of the material is relatively easy, high-order resonance is prevented, and focusing and tracking drive control can be performed easily and accurately.

[Summary of the Invention g] The present invention provides a stationary magnetic path, a part of the stationary magnetic path that is inserted into a gap corresponding to the magnetic path, forms a part of the magnetic path, and is magnetically attracted or attracted to the stationary magnetic path, and the position of the stationary magnetic path is The holding tube of the objective lens is controlled.

A mechanism for holding the holding cylinder movably in the tracking direction and the focusing direction, at least one magnetic generation source for generating magnetic flux in the stationary magnetic path, and a control electromagnet for driving the holding cylinder. This device is characterized in that a magnetic fluid is held in the magnetic flux passing portion between the holding cylinder side and the stationary magnetic path to suppress resonance.

〔Effect of the invention〕

In this invention, the holding cylinder of the objective lens is magnetically attracted or attracted to the stationary magnetic path and can move freely in the tracking direction and the focusing direction. Since this is done through adjustment, it has the advantage of being easy and accurate to control.

In particular, in this invention, since the magnetic fluid is held in the magnetic flux penetrating portion between the holding cylinder side and the stationary magnetic path, the magnetic fluid receives a shearing force as the two move relative to each other.

Damping force is generated by internal friction, and resonance can be suppressed. Furthermore, since the magnetic fluid has a higher magnetic permeability than air, the magnetic flux density of the magnetic flux penetrating portion becomes higher, so there is an advantage that the permanent magnet can be made smaller and the overall size can be made smaller.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 2 and 3, reference numeral 11 denotes a cylindrical outer cylinder made of a magnetic material and forming part of a stationary magnetic path, and a holding cylinder 13 for the objective lens 12 is disposed approximately at the center of this outer cylinder 11. be done. The holding cylinder 13 is also made of a magnetic material, and has a V-shaped guide #$ parallel to the axis on one side 111 thereof.
A linear shaft portion 15 having a diameter of 14 is provided, and a magnetic pole 16 is formed on the opposite side surface.

This holding cylinder 13 is magnetically attracted to a bearing body 19 made of a magnetic material and equipped with a U-shaped guide groove 18, which receives a straight shaft part 15 through a plurality of steel balls 17, and is attracted in the tracking direction. It is supported so that it can freely swing in the direction of the casing.

The bearing body 19 has a permanent magnet 20 provided as a magnetic generation source.
It is fixed to one side of the inner periphery of the outer cylinder 11 via. The steel ball 17 has the guide groove 14 of the linear shaft portion 15 and the guide 111I18 of the bearing body 19 shorter than both of them and 18, so that the magnetic flux density rapidly decreases at the upper and lower ends and restrains them toward the center. ing. The plurality of steel balls 17 are movably held at a position where the attraction force based on the permanent magnet 2o and the mutual repulsion force are balanced.

A permanent magnet 21 as a similar magnetism generation source is also provided on the other side of the inner periphery of the outer cylinder 11, and a magnetic pole 23 of a control electromagnet 22 is disposed inside the permanent magnet 21 in contact with the permanent magnet 21. The magnetic pole 23 is in the normal shape 1! ! 4ζ, which faces the magnetic pole 16 of the holding cylinder 13, and its tip has four protruding magnetic poles 241 to 2
It is divided into 4d, and coils 25a to 25d are wound around each of them.

Outer cylinder 11. Permanent magnet 20. Bearing body 19. Permanent magnet 21.
The magnetic pole 23 forms a stationary magnetic path, and the holding cylinder 13 which is a movable part
Together, they form a θ-shaped magnetic path as a whole.

In this optical pickup, in particular, this is to provide a damping function to vibrations of the holding cylinder 13.

Magnetic fluids 26 and 27 are held in the magnetic flux penetrating portion between the holding cylinder 13 side and the stationary magnetic path. That is, magnetic fluid 2
6 is filled between the magnetic pole 16 of the holding cylinder 13 and the magnetic pole 23 of the control electromagnet 22 and is held by the magnetic flux passing between them, and does not require a special container for holding. .

Further, the magnetic fluid 27 is filled in the guide #114 of the linear shaft portion 15 and the guide s18 of the i-receptor 19, surrounding the steel ball 17, and is held by the magnetic flux passing through these portions.

Next, the operation of this optical pickup will be explained.

t showing the extracted parts of the control electromagnet 22 and the magnetic pole 16
In Figure 44, the right and left coils 25a (25c)
When no current flows through 25b (25d), the magnetic flux at the magnetic poles 23 and 16 is in a state of equilibrium on both sides, as shown by the broken line 28, and in this state, the holding cylinder 13
is in a normal position, not biased in any direction, as shown in FIGS. 2 and 3.

Now in Figure 4, carp JL/25a (25c),
When a current flows in the direction shown in 25b (25d)1, this current generates a magnetic flux as shown by the single-dot chain @29,
Since this and the magnetic flux 28 are adjusted, the magnetic flux at the protruding magnetic pole 24a (24c) increases and the magnetic flux at the protruding magnetic pole 24b (24d) decreases.

Therefore, the magnetic pole 16 has a strong magnetic flux, the protruding magnetic pole 241 (24
C) The holding cylinder 13 is attracted toward the straight shaft part 1.
Rotate in that direction around the tip of 5.

Furthermore, if the direction of the current flowing through the coils 25m (25c) and 25b (25d) is reversed, the increase and decrease in magnetic flux will be reversed and the holding cylinder 13 will rotate in the opposite direction. In this way, the tracking direction of the objective lens 12 can be controlled.

Next, in FIG. 5, coils 25a (25b), 25
c (25d) Positive When a current is applied in the direction shown, the magnetic pole 16 is attracted to the magnetic pole 24C (24d) for the same reason as shown in FIG. Since the holding cylinder 13 is supported so as to be movable in the vertical direction, it is thereby lowered, and if the direction of 4 ft is reversed, the holding cylinder 13 is raised and the focusing direction of the objective lens 12 can be controlled.

In this case, the focusing direction and tracking direction of the objective lens 12 can be controlled by
The holding cylinder 13 has a natural frequency determined by its mass and the magnetic force that supports it.

There is a possibility that a resonance-like cap may occur in the range of this natural frequency and higher frequencies. However, due to the relative movement during this period, the magnetic fluid 26 held between the magnetic poles 16 and 23 of the holding cylinder 13 is subjected to shearing force. Therefore, a damping force is generated due to the internal friction of the magnetic fluid 26, and abnormal vibrations can be suppressed.

Furthermore, as a general property of the magnetic fluid 26, the magnetic permeability of air is also high, so the magnetic flux density on the opposing surface between the magnetic pole 16 of the holding tube 13 and the stationary side magnetic pole 23 becomes high, and the permanent magnet 20
Alternatively, even if the magnetomotive force of 21 is small, the same effect as in the case of magnetic fluid 26 can be obtained, and in particular, since the magnetic fluid 27 is also filled around the steel ball 17, the internal loss of the fluid is large. It is expected that the effect will be further expanded.

[Other embodiments of the invention]

Next, another embodiment of the present invention will be explained with reference to FIGS. 6 to 8. In the first embodiment, the linear shaft portion 1 of the holding cylinder 13 is
5 is held by a bearing body 19 via a plurality of steel balls 1, and the magnetic pole 16 on the other side is opposed to the magnetic pole 23 of the control electromagnet 22, so that the holding cylinder 13 can be freely moved in the tracking direction and the focusing direction by magnetic force. It is to be kept as such.

On the other hand, the embodiments shown in FIGS. 6 to 8 are as follows.

An edge shaft 31 is formed on one side of the holding cylinder 13, and the edge shaft 31 is attracted by magnetic force to a bearing body 33 made of a magnetic material and equipped with a V-shaped groove 32 to support the edge shaft 31 so as to be swingable in the tracking direction. . This bearing body 33 is disposed facing the permanent magnet 19 at a distance and is attracted to it, but edges 34a, 34b, 35a, perpendicular to the edge axis 31,
35b is supported by a pair of frame-shaped parallel links 34 and 35 so as to be swingable in the focusing direction. That is, the edges 34m and 35m are in the V-shaped grooves 36g and 37a formed on the outside of the bearing body 33.

Furthermore, the edges 34b and 35b are respectively engaged with V-shaped #1136b and 37b formed on the outside of the magnetic pole 23, thereby making it possible to support the bearing body 33 against the stationary part i. The bearing body 33 also prevents the edge shaft 31 from sliding in the longitudinal direction.
Stoppers 38a and 38b are provided for stopping the movement.

Furthermore, in this optical pickup as well, the holding body 13
In order to suppress abnormal vibrations, magnetic fluids 39 and 40 are held between the magnetic poles 14 and 23 and between the bearing body 33 and the permanent magnet 20, respectively. In this embodiment, the configuration of other parts is the same as in the $1 embodiment, so corresponding parts are denoted by the same reference numerals and detailed explanation will be omitted.

In addition, in Fig. 8, for convenience of understanding, the magnetic fluid is 39°40°.
This shows the case where is omitted.

Also in this embodiment, the coil 25a of the control electromagnet 22
Regarding the first embodiment, it is possible to drive the holding cylinder 13 in the focusing direction and the tracking direction and control the position of the objective lens 12 easily and accurately by adjusting the direction and magnitude of the current flowing through the points 25d and 25d. This is the same as described in FIGS. 4 and 5.

At this time, the magnetic fluid 39, 40 acts to suppress abnormal vibrations of the holding cylinder 13, as in the case of the first embodiment, by increasing the magnetic flux density of the magnetic flux haze passage part, thereby increasing the permanent magnet. It is possible to downsize and reduce the overall size and cost.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without changing the gist.

For example, in each of the above embodiments, a cylindrical outer cylinder 11 is used, but other cylindrical bodies such as a rectangular cylinder may be used instead.

Further, in each of the above embodiments, a case is shown in which two permanent magnets are used, but the number of permanent magnets as a magnetic generation source is not limited to this, and for example, one part of the bearing body 19 or 33. Alternatively, by using permanent magnets for the entire bearing body 19 or 33, the attraction force of the bearing body 19 or 33 can be further increased and stabilized.

In each of the above embodiments, the protruding magnetic poles 24a to 24 are
A case has been described in which one coil 25a to 25d is wound around each of the coils 25a to 25d. However, these have one protruding magnetic pole 1
The coils for tracking control and focusing control may be wound separately, and as shown in Figure @9, one coil may be wound across two protruding magnetic poles. It is also easier to adjust by rubbing 4 times like this. In FIG. 9, each coil is indicated by 41a to 41d.

[Brief explanation of the drawing]

Figure 1 (1al, 1b) shows an example of a conventional optical pickup (al is a plan view, (b) is a longitudinal front view,
Figure 2 is a plan view of an embodiment of the present invention, Figure 3 is a longitudinal sectional front view of the embodiment, Figures 4 and 5 are respectively explanatory views of the operation of the embodiment, and Figure 6. 7 is a plan view of another embodiment of the present invention, FIG. 7 is a longitudinal sectional front view of the same embodiment, and FIG. 7 is a perspective view with a portion cut away. FIG. 9 is a perspective view showing a different configuration of the control electromagnet. 1... Stationary part 2... Holding cylinder 3... Lens 4... Movable frame 5a, 5b, 6a, 5
b --- Leaf spring 7...Magnetic circuit 7'...Magnetic gap 8...Coil 9a, 9b...Attraction iron pieces 10a, 10b...Electromagnet 11...Outer tube 12...Objective Lens 13・
...Holding tube 14...Guide groove 15...Straight shaft portion 16...Magnetic pole 17...Steel ball 1
8... Guide groove 19... Bearing body 20.21
...Permanent magnet 22...Control electromagnet 23...Magnetic poles 248-24d...Protruding magnet 41 251-25
d...Coil 26.27...Magnetic fluid 31...Edge shaft 32...V-shaped groove 33...
Bearing body 34.35...Parallel link 34a,
34b, 35m, 35b...-edge 36a,
36b, 37a, 37b-・V-shaped groove 38a, 38b・
...Stopper 39.40...Magnetic fluid 41a-4
1d...Coil Figure 1 (a) b (b) Figure 2 Figure 3 1b 24d 6vA Figure 8 Figure 9 4c

Claims (1)

[Claims] (1) A stationary magnetic path, and a magnetic field that is inserted into a gap corresponding to the stationary magnetic path and forms a part of the magnetic path, and is magnetically attracted or attracted to the stationary magnetic path and changes its position. a holding tube for an objective lens to be controlled; a mechanism for holding the holding tube movably in a tracking direction and a focusing direction; at least one magnetic generation source generating magnetic flux in the stationary magnetic path; 1. An optical pickup comprising: a control electromagnet for driving, and a magnetic fluid is held in a magnetic flux penetrating portion between the holding cylinder side and the stationary magnetic path. (2) The mechanism for holding the holding cylinder movably in the tracking direction and the focusing direction includes a linear shaft portion having a guide groove formed on one side of the holding cylinder, and a complex structure provided on the side of the static magnetic path. The optical pickup according to claim 1, further comprising a bearing body that receives the linear shaft portion through several steel balls. +31 -1: The mechanism for holding the holding cylinder movably in the tracking direction consists of an edge shaft formed on one side thereof and a bearing body having a V-shaped groove for receiving this edge axis, and the mechanism holds the holding cylinder movably in the focusing direction. Claim 1, characterized in that the mechanism for movably holding the bearing body comprises a frame-shaped parallel link that swingably supports the bearing body relative to the stationary part by an edge in a direction perpendicular to the edge axis. Optical pickup as described in section. (4) The magnetic pole of the control electromagnet has four protruding magnetic poles, and by adjusting the direction and magnitude of the stray current flowing through the coil wound around these protruding magnetic poles, the tracking direction of the objective lens can be determined. The optical pickup according to any one of claims 1 to 3, wherein the optical pickup controls a focusing direction. (5) The optical pickup according to claim 4, wherein the control electromagnet has a coil for controlling the tracking direction and a coil for controlling the focusing direction.