JPH0435815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an optical recording disk that is widely used for video, audio, etc., and when recording information or reading recorded information, a laser beam is emitted onto the disk. The present invention relates to a driving device for a converging objective lens, and particularly to a device for setting a neutral position in the focus direction.

Taking reading as an example, this type of optical information recording/reproducing device irradiates an optical recording disk with an information reading laser beam focused by an objective lens, and reads the information recorded on the disk from the reflected light. The objective lens is mounted on a slider that moves in the track direction (radial direction) of the disk. In order to read out information accurately, the objective lens must be able to move in the optical axis direction (focus direction) for focus adjustment, and make fine adjustments in the track direction, that is, approximately in the radial direction of the disk, on this slider. No. Figures 1 to 6
The figure shows a conventional objective lens drive device that has this function.

In Figures 1 to 6, 1 is the rotating shaft 1a.
An optical recording disk that is rotated around the
A slider 3 is slidably supported on a guide rail 2 provided in the radial direction of the disk 1. The slider 3 may be fixed to the tip of an arm that is rotatable around one point. The objective lens 4 is
It is mounted on a cylindrical rotating body 6 supported on the slider 3 so as to be rotatable about a guide shaft 5. The optical axis of this objective lens 4 is parallel to the guide axis 5, and includes a laser light source and a beam splitter (a combination of a polarizing beam splitter and a quarter-wave plate, not shown).
The information reading laser beam guided through the disk (or a half mirror) is focused onto the disk 1. The light reflected by the disk 1 passes through the objective lens 4 again, is split by a beam splitter, enters a light receiving element, and is read out as a signal by this light receiving element.

In order to enable focus adjustment of the objective lens 4 when reading this information and fine adjustment of the approximately radial track direction of the disk 1, the cylindrical rotating body 6 is equipped with a focus direction drive coil 7 and a track direction drive coil 7. A coil 8 is wound and fixed. Both coils 7 and 8 are fixed to the rotating body 6 in close contact with each other using an adhesive or the like, and the focus direction drive coil 7 is wound coaxially with the guide shaft 5.
On the other hand, the track direction drive coil 8 is divided into four groups in the circumferential direction, and each coil 8a, 8b,
8c and 8d are the circumferential component s and the axial component z
It is continuously wound into a square shape.

On the other hand, a yoke 10 is fixed to the slider 3. The yoke 10 has a base 12 having an inner arcuate portion 11 at two diametrically opposed locations, and an annular permanent magnet 13 located outside the inner arcuate portion 11. A cap 14 is attached at a position opposite to the inner circumferential arc-shaped portion 11. The inner circumferential arcuate portion 11 and the cap 14 portion constitute a magnetic force reinforcement section I having a higher magnetic flux density than other portions. Coils 7 and 8 fixed to the cylindrical rotating body 6
is inserted into the gap 15 between the inner arcuate portion 11 and the cap 14. When the track direction drive coil 8 is not energized to the focus direction drive coil 7, the adjacent coils 8 are inserted into this magnetic force strengthening section. It is arranged to be located symmetrically within I.
Reference numeral 16 denotes a rotation range regulating pin that hangs down from the rotating body 6, and the lower end of this regulating pin 16 is supported by a viscoelastic material 18 to regulate the neutral position of the objective lens 4 in the track direction. That is, the viscoelastic material 18 is
Connecting plate 1 fixed to inner circumferential arcuate portion 11 of yoke 12
7, and its free end is connected to the lower end of the regulating pin 16 by a presser ring 19.

In the above conventional device, the focus direction drive coil 7
When a current is applied to the gap 15, the directions of the magnetic flux lines generated in the gap 15 and the current flowing through the coil 7 are perpendicular to each other. It will move in the axial direction, that is, in the optical axis direction F of the objective lens 4,
The focus can be adjusted by changing the magnitude of the current flowing through the focus direction drive coil 7.

Furthermore, when a current is applied to the track direction drive coil 8, which is divided into four groups, so that the current flows in the same direction in the axial component z located within the magnetic force reinforcement section I, the current flows in the axial component z. Since the current and the magnetic flux lines generated in the gap 15 are perpendicular to each other, the rotating body 6 rotates around the guide shaft 5. Therefore, the objective lens 4 mounted on the eccentric position of the rotating body 6 is driven in the track direction T, and fine adjustment in the track direction is performed.

By the way, in such an objective lens drive device,
It is necessary to maintain the rotating body 6 in a floating state, that is, to hold it in a neutral position so that the objective lens 4 of the rotating body 6 can move up and down in the focus direction. In the conventional device, an initial current (offset current) of an appropriate magnitude is passed through the focus direction drive coil 7 to maintain the rotating body 6 in a neutral state. This requires a complex electrical circuit. That is, since it is necessary to perform a focus search operation at the time of starting, there is a problem that the control system becomes complicated.

The present invention does not rely on electrical means of applying an offset current, but instead uses magnetic means to
This device was designed to be able to set the neutral position in the focus direction of a rotating body on which an objective lens is mounted. a focus direction drive coil which is fixed to the slider so as to be located concentrically with the moving object and outside of the permanent magnet, and which moves the rotating object in the axial direction when energized by electromagnetic interaction with the permanent magnet; In the focus direction driving device of the drive device, a neutral position setting member made of at least one magnetic material through which the magnetic flux lines of the permanent magnet pass is further provided on the slider, and the rotating body is adjusted according to the position of the neutral position setting member. The neutral position of the rotating body in the focus direction is set by the axial force acting on the rotating body.

The present invention will be described below with reference to the illustrated embodiments.
First, the configuration of the objective lens driving device itself of this embodiment will be explained. The configuration of the focus direction driving device of the objective lens driving device is the premise of the present invention. In FIGS. 7 to 10, the guide rail 2, objective lens 4, slider 3, guide shaft 5, and optical recording disk 1 are the same components as in the conventional apparatus, and in this embodiment, the guide shaft 5 is made of magnetic material. The objective lens 4 is fixed to an eccentric portion of a disk-shaped rotating body 20 made of a non-magnetic material and has a guide tube portion 21, and the guide tube portion 21 is fitted onto the guide shaft 5 so as to be rotatable and movable in the axial direction. It is being A pair of permanent magnets 22, 22 each having a shape of about a quarter arc are suspended and fixed on the lower surface of the rotary body 20 at two radially opposite locations. The permanent magnets 22, 22 are magnetized in the radial direction, and have the same polarity on their inner and outer circumferential parts. That is, the inner peripheral portions are both S poles, and the outer peripheral portions are both N poles, for example.

The support base 23 fixed to the slider 3 side is made of a non-magnetic material such as an aluminum alloy, and has a cylindrical wall 24 located outside the permanent magnets 22, 22. This support stand 23 does not have a magnet, unlike the conventional example. Instead of the magnets, a focus direction drive coil 7 and a track direction drive coil 8, which were fixed to the rotating body 6 in the conventional example, are fixed to the inside of the cylindrical wall 24. The direction of the windings of the focus direction drive coil 7 and the track direction drive coil 8, the permanent magnet 22
The positional relationship between the focus adjustment drive coil 7 and the focus adjustment drive coil 7 is the same as that of the conventional example. Directional drive coil 8
When current is applied in the forward and reverse directions, the rotating body 20 rotates about the guide shaft 5, and the position of the objective lens 4 in the track direction is adjusted. FIG. 10 shows the state before the coils 7 and 8 are fixed to the cylindrical wall 24, and both coils are wound on a bobbin or a bobbin made of a non-magnetic material.

Further, the present invention utilizes the fact that the permanent magnet 22 is fixed to the rotating body 20, so that the rotating body 20 can be placed in a neutral position in the focus direction of the rotating body 20, that is, in a state where no current flows through the focus direction drive coil 7.
A neutral position setting member 30 made of a magnetic material, like the guide shaft 5, is fixed below the guide shaft 5, which is the center of rotation of the rotating body 20. This neutral position setting member 30 is composed of a flat plate material (disk material or perforated disk material), and depending on the position of this neutral position setting member 30, the rotating body 20, that is, the neutral position in the focus direction of the objective lens 4. can be set. In other words, the magnetic flux lines of the permanent magnet 22 pass through the guide shaft 5, which is a magnetic material, and the neutral position setting member 30, so the permanent magnet 22, that is, the rotating body 20, moves out from the N pole of the permanent magnet 22 depending on the position of both magnetic materials. The magnetic flux lines entering the south pole are subjected to a force that makes them equal at the top and bottom of Fig. 11. Therefore, the neutral position in the focus direction of the rotating body 20, that is, the objective lens 4, which is supported to move in the axial direction with extremely light force, can be set by the axial position of the guide shaft 5 of the neutral position setting member 30. 11A and 11B are for explaining the principle in more detail, and FIG. 11A shows the guide shaft 5 made of magnetic material when there is no neutral position setting member 30.
This shows that the magnetic flux lines passing through are stable.
At this time, the magnetic flux line U that leaves the permanent magnet 22 and draws an upward loop acts as a force to lift the rotating body 20, and the magnetic flux line B that draws a downward loop acts as a force that moves the rotating body 20 downward. Therefore, if the entire weight of the rotating body 20 is G, the rotating body 20 will be stabilized at a position in the focus direction where U=B+G. However, if a neutral position setting member 30 is provided as shown in FIG.
The upper magnetic flux line U' decreases. For this reason, rotating body 2
0 receives a downward force, and is at a position lower than the state in figure A, that is, the upper and lower magnetic flux lines are balanced, U' =
It becomes stable at the position where B'+G holds. Therefore, when the neutral position setting member 30 is raised in the X direction,
When the rotating body 20 is lowered in the x direction so that the magnetic flux lines above and below the permanent magnet 22 are even, and conversely when the neutral position setting member 30 is lowered in the Y direction, the rotating body 20 is lowered in the y direction.
rise in the direction. This means that if the position of the neutral position setting member 30 can be adjusted in the axial direction, the neutral position of the objective lens 4 in the focus direction can be set freely. Any means for adjusting the position of the neutral position setting member 30 may be used. Of course, the neutral position setting member 30 may be fixed at a preset position,
Also in this case, the effect that the neutral position in the focus direction can be set without any special electrical control is obtained, compared to the conventional device in which an offset current must be passed through the focus direction drive coil 7.

In the above embodiment, both the guide shaft 5 and the plate-shaped neutral position setting member 30 are made of magnetic material, but as shown in FIGS. 12A and 12B, the guide shaft 5 is made of a non-magnetic material, , for example, the support base 23
Even if a cylindrical member or annular member 31 made of a magnetic material concentric with the rotating body 20 is provided on the cylindrical wall 24 of Accordingly, the neutral position of the rotating body 20 in the focus direction can be set. Furthermore, even if the neutral position setting member provided on the outer periphery of the rotating body 20 is not annular and is simply a piece of magnetic material 32 as shown in FIGS. 13A and 13B, it can change the distribution of magnetic flux lines, so the same A neutral position can be set. In the case of the example shown in FIG. 13, it is preferable to provide the magnetic material pieces 32 at two locations in the radial direction corresponding to the positions of the permanent magnets 22, from the standpoint of axial force balance.

14A and 14B are diagrams for explaining the operation of the embodiment shown in FIG. 11. FIG. 14A shows a state where the magnetic flux lines are balanced by the magnet 22 and the neutral position setting member 30, that is, the neutral position. From this state, move the neutral position setting member 30 to the magnet 2.
When the magnet 22 (rotating body 20) is moved by X in the direction approaching the neutral position setting member 30, as shown in FIG. 14B, the magnet 22 (rotating body 20) moves by By moving, the lines of magnetic flux are kept in balance.

FIGS. 15A and 15B are diagrams for explaining the operation of the embodiment shown in FIGS. 12 and 13. 15th
Figure A shows the magnet 22 and neutral position setting members 31, 32.
This shows a state in which the magnetic flux lines are balanced, that is, held in a neutral position. From this neutral state, an external force is applied to the rotating body 20, and the rotating body 20
Even if 0 moves, as shown in FIG. 15B, a returning force acts in the direction of the neutral position to maintain the balance of the magnetic flux lines, and the magnetic flux returns to the neutral position.

Further, as the magnetic material constituting these neutral position setting members, any (ferro)magnetic material such as iron, steel, stainless steel, etc. can be used. Although it is possible to set the neutral position of the objective lens 4 in the focus direction by using a magnet instead of the neutral position setting member 30, the magnetic attractive force (or repulsive force) with the permanent magnet 22 is too strong with a magnet. The focus direction driving coil 7 cannot smoothly drive the focus direction.

It should be noted that the track direction drive device shown in the above embodiment is merely an example, and the present invention is not limited to the track direction drive means and its neutral position setting means. Further, in the above embodiment, the focus direction drive coil 7 and a part of the neutral position setting member (the annular member 3
1) is fixed to the annular wall 24 of the support base 23, but the support base 23 and its annular wall 24 are not necessarily provided. It may be provided on the slider 3 by any suitable means.

As described above, according to the present invention, in an objective lens drive device configured to fix a focus direction drive coil to a slider and fix a permanent magnet to a rotating body on which an objective lens is mounted, at least With a very simple configuration in which a neutral position setting member made of one magnetic material is provided, it is possible to set the neutral position of the objective lens in the focus direction according to the position of the neutral position setting member. Therefore, compared to conventional devices that set the neutral position by passing an offset current through the focus direction drive coil, this device does not require a complicated electrical circuit and therefore does not require electrical adjustment. A device with excellent sensitivity can be obtained. In particular, if the position of the neutral position setting member is adjustable, the neutral position of the objective lens in the focus direction can be freely set.

[Brief explanation of drawings]

Fig. 1 is a plan view showing the relationship between the slider and the optical recording disk of an optical information recording/reproducing device, Fig. 2 is a plan view of a conventional objective lens drive device, and Fig. 3 is a plan view of the support portion of the conventional device. Figures 4 and 5 are cross-sectional views taken along lines - and - in Figure 3, respectively, Figure 6 is a perspective view of the cylindrical rotating body of the conventional device, and Figure 7 is the objective lens of the present invention. FIG. 8 is a sectional view taken along the line - in FIG. 7, FIG. 9 is a perspective view of the rotating body of the present invention equipped with an objective lens, and FIG. 10 is a plan view showing an embodiment of the driving device. A perspective view of the coil to be fixed, FIGS. 11A and 11B show the state of magnetic flux lines passing through two neutral position setting members made of magnetic material, and a magnetic circuit diagram showing the principle of the present invention, FIGS. 12A and B and FIGS. 13A and 13B are a plan view and a vertical cross-sectional view showing another embodiment of the present invention, respectively. FIGS. 14A and 14B are a vertical cross-sectional view explaining the operation of the embodiment shown in FIG. 11, and FIG. Figures A and B are longitudinal sectional views illustrating the operation of the embodiment shown in Figures 12 and 13. 1... optical recording disk, 3... slider,
4... Objective lens, 7... Focus direction drive coil, 8... Track direction drive coil, 20...
Rotating body, 22... Permanent magnet, 23... Support base, 3
0... Neutral position setting member, 31... Annular member or cylindrical member, 32... Magnetic material piece.

Claims (1)

[Claims] 1. A rotating body is supported on a slider that is supported movably in the tracking direction with respect to the optical recording disk so as to be rotatable and movable in the axial direction about a guide shaft provided on the slider. , in an optical information recording and reproducing device in which this rotary body is equipped with an objective lens that converges an information readout laser beam onto the disk, a permanent magnet is fixed to the rotary body, and a permanent magnet is placed on the slider concentrically with the rotary body. A focus direction drive coil that moves the rotating body in the axial direction when energized by electromagnetic action with the permanent magnet is fixed, and the slider is further provided with a neutral position made of at least one magnetic material through which the magnetic flux lines of the permanent magnet pass. A focus direction neutral position setting device for an objective lens drive device in an optical information recording/reproducing device, characterized in that a setting member is provided so as to be movable and adjustable in the axial direction. 2. In claim 1, the guide shaft is made of a magnetic material, and the neutral position setting member is composed of the guide shaft and a plate made of a magnetic material provided above or below the guide shaft. A focus direction neutral position setting device for an objective lens drive device in an optical information recording/reproducing device comprising: 3. The focus direction neutral position setting device of an objective lens driving device in an optical information recording/reproducing device according to claim 2, wherein the plate member is formed to be adjustable in position in the axial direction of the rotating body. 4. In claim 1, the neutral position setting member is a cylindrical member or an annular member made of a magnetic material located on the outer periphery of the rotating body, and is a focus member of an objective lens driving device in an optical information recording/reproducing device. Directional neutral position setting device. 5. In claim 4, the cylindrical member or the annular member is positioned at a neutral position in the focus direction of an objective lens driving device in an optical information recording/reproducing device, the position of which is adjustable in the axial direction of the rotating body. Setting device. 6. In claim 1, the neutral position setting member is one or more pieces of magnetic material located on the outer periphery of the rotating body, and the neutral position setting member is a neutral position setting member in a focus direction of an objective lens driving device in an optical information recording/reproducing device. Positioning device. 7. In claim 6, the magnetic material piece is a focus direction neutral position setting device of an objective lens driving device in an optical information recording/reproducing device, wherein the magnetic material piece is provided symmetrically at two locations in the radial direction of the rotating body. . 8. In claim 6 or 7, the magnetic material piece is arranged in a neutral position in a focus direction of an objective lens driving device in an optical information recording/reproducing device, the magnetic material piece being formed so as to be adjustable in position in the axial direction of the rotating body. Positioning device.