JP3074055B2 - pick up - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup having a structure in which a head base in which a pickup head is mounted on a suspension base by a suspension spring is cantilevered. The present invention relates to a pickup in which the flow of magnetic flux from a fan is shaped like a fan.

[0002]

2. Description of the Related Art An optical pickup has a function of reproducing information recorded on a compact disk (CD) or a laser disk (LD) and generating a focus error signal and a tracking error signal. I have.

In such a pickup, various improvements have been made in pursuit of small size and light weight. One example of such a pickup is a cantilever supporting a head base on which a pickup head is mounted on a suspension base by a biaxial spring. Is being developed.

That is, as shown in FIG. 1, a laser beam emitted from a laser diode 3 provided in a pickup case 2 of a pickup 1
Is diffracted (separated) into a plurality of light fluxes by a diffraction grating deposited on the surface of. Here, the zero-order light at the center is used for signal reading and focus servo, and the two light beams on both sides thereof are used for tracking servo.

The laser beam having passed through the grating 4 is reflected toward a disk (not shown) by a half mirror 5 having the property of transmitting and reflecting the light, and the optical axis thereof is bent by 90 ° by a reflecting mirror 6.

[0006] The laser beam from the reflection mirror 6 is
The light is focused on the disk by the objective lens 37.

The light reflected from the disk is transmitted to the objective lens 37.
After passing through the reflection mirror 6, the light is guided to the optoelectronic integrated circuit (OEIC) 7 through the half mirror 5.

Here, the optical axis of the reflected laser light is adjusted by moving the optoelectronic integrated circuit 7 in the x and y directions.

FIGS. 2 and 3 show an actuator unit housed in the pickup case 2 described above. The actuator unit 9 includes a yoke base 1.
0, a suspension base 20 and a head base 30 are provided.

On one end 10a side of the yoke base 10,
The yoke portions 11 and 12 which are partially bent are provided. A permanent magnet 13 is fixed to the yoke 12.

On the other end 10b side of the yoke base 10,
The screw hole 14 into which the screw 40 is inserted is formed. Positioning holes 15, 15 are formed on both sides of the screw hole 14.

At upper and lower sides of both ends of the suspension base 20, fixing portions 21 and 22 to which fixing pieces 52 at one end of a leaf spring 51 are fixed are provided. At the center of the suspension base 20, a screw hole 23 into which the screw 40 is inserted is formed. On the lower surface side of the suspension base 20, there are provided positioning projections (not shown) inserted into the positioning holes 15, 15 of the yoke base 10.

The head base 30 includes a yoke base 10
An insertion hole 31 through which the yoke portions 11 and 12 are inserted is formed. A coil bobbin 33 having an insertion hole 32 is fixed to the insertion hole 31. The coil bobbin 33 has
Two exciting coils 34 and 35 for tracking are attached. In addition to the periphery of the coil bobbin 33, Four
An exciting coil (not shown) for scum is wound. A track is provided above and below each end of the coil bobbin 33.
A coil extraction section 3 from which the start or end of the king excitation coils 34, 35 or the focus excitation coil is extracted.
6A is provided.

An objective lens 37 is attached to the tip of the head base 30. At the upper and lower sides of both ends of the head base 30 with the objective lens 37 interposed therebetween, a fixing portion 38 to which a fixing piece 54 at the other end of the leaf spring 51 is fixed.
39 are provided.

The leaf spring 51 is manufactured in a state of being connected to the ear portion 60 via a connecting piece 61, and the fixing pieces 52, 54 of the leaf spring 51 are connected to the suspension base 20 and the head. After being fixed to the base 30 side, the central portion of the connecting piece 61 is cut, and the leaf spring 51 is
It is separated from 0.

The flexible substrate 80 supplies an exciting current as a control signal for tracking and focusing. The output end of the lead wire 81 has a connecting piece 52A provided on the fixing piece 52 of the leaf spring 51. Are connected to each other.

When assembling the actuator unit 9 having such a configuration, first, the permanent magnet 13 is fixed to the yoke portion 12 of the yoke base 10. Next, the suspension base 2 is inserted into the positioning holes 15, 15 of the yoke base 10.
The yoke base 10 and the suspension base 20 are fixed by inserting positioning projections provided on the lower surface side of the “0”.

After the fixing of the yoke base 10 and the suspension base 20 is completed, the fixing portions 21 provided on the upper and lower sides of both ends of the suspension base 20,
A fixing piece 52 at one end of the leaf spring 51 is fixed to the plate 22 using, for example, a thermosetting adhesive.

Next, the fixing piece 5 on the other end side of the leaf spring 51
4 is fixed to the fixing portions 38 and 39 of the head base 30 using the above-mentioned thermosetting adhesive.

After the fixing pieces 52 and 54 of the leaf spring 51 are fixed to predetermined portions of the suspension base 20 and the head base 30, the coil is pulled out from the upper and lower coil take-out portions 36A at both ends of the coil bobbin 33, and the leaf spring is pulled. 5
The first fixing piece 54 is soldered.

Accordingly, the exciting coils 34 and 35 for tracking and the exciting coil for focusing are
Is electrically connected to After the soldering of the leaf spring 51 is completed, the central portion of the connecting piece 61 of the ear part 60 is cut, and the leaf spring 51 is separated from the ear part 60.

For the flexible substrate 80, a connecting piece 52A provided on the fixing piece 52 of each leaf spring 51 is inserted into a land 82, and the land is soldered.
After soldering with the flexible board 80, screws 40 are inserted into the screw insertion holes 23 and 14 of the suspension base 20 and the yoke base 10, and the suspension base 20 and the yoke base 10 are connected to the pickup case 2 through the screws 40. To a predetermined location.

An exciting current, which is a control signal from the flexible board 80, is supplied to each exciting coil provided on the coil bobbin 33 via each leaf spring 51, so that tracking and focusing are performed. That is, when tracking is performed, magnetic flux is generated from the tracking excitation coils 34 and 35, and when focusing is performed, magnetic flux is generated from the focusing excitation coil.

The direction and strength of the generated magnetic flux are controlled by a control signal supplied via the flexible substrate 80, so that the head base 30 cantileverly be supported by each leaf spring 51. Move in the direction. Thereby, the objective lens 37 can be moved in the tracking direction and the focus direction of the disk.

[0025]

In the above-described conventional actuator unit 9, since the magnetic flux flowing from the permanent magnet 13 to the yoke portion 11 is linear as shown in FIG. Trouble has occurred.

That is, in the actuator unit 9 shown in FIG. 2, the permanent magnet 13 serving as a driving source and the respective exciting coils 34 and 35 (each of the exciting coils 34 and 35 are regarded as a single unit).
In this configuration, it is generally impossible to match the drive center of the leaf spring 51 with the position of the center of gravity of the movable head base 30.

Therefore, the movement of the head base 30 is delayed with respect to the driving direction of the leaf spring 51 (phase delay),
In addition to the occurrence of higher-order resonance in the head base 30, the phase delay of the head base 30 causes the objective lens 3
7, the tracking followability is reduced.

In order to prevent this, FIG.
As shown in FIG. 7, by obtaining a force O which is a source of the rotational motion, the head base 30 is applied to each of the exciting coils 34 and 35.
Generates a moment m around the moving direction of the
It is conceivable to cancel the problem caused by the displacement between the driving center and the center of gravity of the head base 30 in the movable state.

The present invention has been made in view of such circumstances, and takes into account the displacement between the drive center of the suspension spring and the position of the center of gravity of the head base, and moves the head base in the direction in which the head base is to be moved. It is an object of the present invention to provide a pickup capable of preventing a higher-order resonance generated in a head base by obtaining a moment and canceling a mutual displacement.

[0030]

In order to achieve the above object, the present invention provides a method for reading information recorded on an information recording medium.
And the excitation coil for driving the head base
The mounted head base is separated by the suspension spring
Supported and separated from the exciting coil.
Due to the electromagnetic action with the permanent magnets facing each other with a distance
Is a pickup driven in the tracking direction.
The permanent magnet cuts the left and right corners of the surface facing the exciting coil.
The permanent magnet and the excitation coil
At the center of the left and right sides of the exciting coil facing surface.
And the longest on both the left and right ends of the exciting coil facing surface.
Thus, the permanent magnet was diffused with respect to the exciting coil.
It is characterized by providing a magnetic flux .

[0031]

[Action] In pickup of the present invention is intended to prevent the head base of the high-order resonance caused by misalignment between the drive center and the head base of the center-of-gravity position by each of the suspension springs, facing the yoke portion and the excitation coil
Cut off the left and right corners of the surface of the permanent magnet facing the exciting coil
By doing so, the yoke and excitation coil
To give a diffused magnetic flux to the

This makes it possible to obtain a moment that circulates in the direction in which the head base is to be moved, so that the displacement between the drive center of each suspension spring and the position of the center of gravity of the head base can be offset. Higher-order resonance generated in the head base can be prevented.

Further, since a moment that circulates in the direction in which the head base is to be moved can be obtained, the objective lens of the head base can be moved more quickly. Can also be improved.

[0034]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings described below, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals, and redundant description will be omitted.

FIGS. 5 and 6 show the structure of the actuator unit 9 according to the pickup of the present invention. The actuator unit 9 includes a yoke base 10, a suspension base 20, and a head base 30.

On one end 10a side of the yoke base 10,
Yoke portions 11 and 12 are provided. A permanent magnet 13 is fixed to the yoke 12. A corner 13a of the surface of the permanent magnet 13 facing the yoke 11 is cut. As a result, the width of the surface of the permanent magnet 13 facing the yoke 11 is made smaller than the width of the yoke 11, so that the magnetic flux from the permanent magnet 13 spreads in a fan-like manner and Be guided. In the cut state of the corner 13a of the permanent magnet 13, the cut is not limited to a square as shown in FIG.

On the other end 10b side of the yoke base 10,
The screw hole 14 for inserting the screw 40 is formed. Positioning holes 15, 15 are provided on both sides of the screw hole 14.
Are formed.

The leg portions 91b of the solder terminals 91 having the connection pieces 91a are press-fitted into the fixing portions 21 and 22 provided at both ends of the suspension base 20, and the solder terminals 91 are provided. The fixing piece 52 of the leaf spring 51 is fixed by solder as described later.

On the lower surface side of the fixing pieces 52 , 54 of the leaf spring 51 ,
Is pre-coated with solder. These fixing pieces 52, 5
4, holes 52a and 54a are provided as shown in FIG. 6, and the fixing pieces 52 and 54 are formed by the holes 52a and 54a.
The heat by the laser beam to the solder previously applied to the lower surface side of the 54 is efficiently transmitted. A connecting piece 53 is provided on the fixing piece 54 of the leaf spring 51,
The excitation coils 34, 35, and 36 on the coil bobbin 33 side are connected to each other.

The shape of the holes 52a and 54a is not limited to a circular shape as shown in FIG.
Notched holes 52b and 54b as shown in FIG. Reference numeral 51A in the figure indicates a vibration absorbing unit for absorbing vibration of the leaf spring 51.

At the center of the suspension base 20,
A screw hole 23 is formed. Suspension base 2
0, positioning holes 15 of the yoke base 10,
15 are provided with positioning projections (not shown).

The head base 30 includes the yoke base 10
An insertion hole 31 through which the yoke portions 11 and 12 are inserted is formed. A coil bobbin 33 having an insertion hole 32 is fixed to the insertion hole 31.

As shown in FIG. 8, an exciting coil 36 for focusing is wound around the coil bobbin 33. Exciting coils 34 and 35 for tracking are mounted on the upper part of the exciting coil 36.

The coil lead-out portion 36A of the coil bobbin 33 has a leg 92b of a solder terminal 92 having a connection piece 92a.
Is press-fitted. Here, the connection relationship between each of the excitation coils 34, 35, 36 and the connection piece 92a of the solder terminal 92 is, for example, when the connection piece 92a of the solder terminal 92 on the upper side of the coil bobbin 33 is used for tracking and focus, respectively. The connection pieces 92a on the lower diagonal correspond to the tracking pieces and the focus pieces, respectively.

As a result, when the coil bobbin 33 is assembled into the head base 30, the usage of the respective exciting coils 34, 35, 36 is changed even when the coil bobbin 33 is mounted upside down.
Therefore, workability can be greatly improved. This
This is to prevent , for example, tracking from being used erroneously for focusing .

Incidentally, each of the exciting coils 34, 35, 36
As shown in FIG. 9, for example, as shown in FIG. 9, the connection piece 92a of the solder terminal 92 on the upper side of the coil bobbin 33 is used for focusing, and the connection piece 92a of the lower When used for tracking , if the coil bobbin 33 is mounted upside down,
The applications of the respective exciting coils 34, 35, 36 are reversed. For this reason, when assembling the coil bobbin 33 into the head base 30, the mounting direction of the coil bobbin 33 is restricted, so that considerable attention is required, which may cause a reduction in workability.

At the tip of the head base 30, an objective lens 37 is attached. Fixed portions 38 and 39 provided above and below both ends of the head base 30 with the objective lens 37 interposed therebetween have leg portions 90 of the solder terminals 90.
b is press-fitted.

The leaf spring 51 is manufactured in a state where the leaf spring 51 is connected to the ear portion 60 having the positioning hole 62 through the connection piece 61.
After the members 2 and 54 are fixed to the suspension base 20 and the head base 30, the central portion of the connecting piece 61 is cut, and the leaf spring 51 is cut off from the ear portion 60.

A flexible board 80 having lead wires 81 is attached to the suspension base 20 side. Each land 82 of the flexible substrate 80
Is formed with a positioning recess 83 for positioning the connection piece 91a of the solder terminal 91.

Here, the dimension between the lands 82 of the flexible substrate 80 is slightly wider than the dimension between the connection pieces 91a of the solder terminals 91. As a result, when the respective connection pieces 91a are fitted into the positioning recesses 83 of the lands 82, a repulsive force is generated in the flexible substrate 80 due to bending, and a force in a direction spreading outward acts on the respective positioning recesses 83. , connecting pieces 91a and connected to the lands 82 that Do made more reliable. Regarding the shape of the land 82 may be of circular as shown in FIG.

FIG. 10 shows the action of the leaf spring 51 depending on the state of attachment of the leaf spring 51 in FIG. 5, and shows a state in which the support interval on the head base 30 side is narrowed when viewed from the suspension base 20 side. Is attached.

That is, the leaf springs 5 facing each other on the plane
1 of the distance between the fixing piece 52 and L1, also fixed piece 54
When the distance between them is L2, L1> L2.
Accordingly, when the direction of the driving force F obtained by the magnetic fluxes generated from the tracking excitation coils 34 and 35 is set to the direction of the arrow (left side), the resultant force with the force M generated in the leaf spring 51 causes the actual movement direction to change. A force V is obtained. Further, a reaction force S is obtained as a reaction of the force M.

Since the reaction force S produces a moment m which circulates in the moving direction (F direction) of the head base 30 having the apparent action point G1, the action point G0 by the leaf spring 51 and the center of gravity of the head base 30 are obtained. Even if the positions do not match, it is possible to prevent a phase delay from occurring in the head base 30. As a result, higher-order resonance generated in the head base 30 can be minimized.

That is, in the actuator unit 9 shown in FIG. 5, the permanent magnet 13 serving as a driving source and each of the exciting coils 34, 35 and 36 (each of the exciting coils 34, 35 and 36 are regarded as a single unit) are each one. In such a configuration, the driving center of the leaf spring 51 (action point G0)
It is generally impossible to match the center of gravity of the head base 30 in the movable state with the center of gravity.

For this reason, the displacement between the drive center by the leaf spring 51 and the position of the center of gravity of the head base 30 causes high-order resonance. However, as described above, when viewed from the suspension base 20 side. By narrowing the support interval of the leaf spring 51 on the head base 30 side, it is possible to cancel a phase delay due to higher-order resonance.

By the way, as shown in FIG. 11, when the support interval of the leaf spring 51 on the head base 30 side as viewed from the suspension base 20 side is increased (L1 <L2) and the driving force F is the same as described above, Since the directions of V rise leftward and descend leftward, respectively, and the directions of the reaction forces S generated in the respective leaf springs 51 are also reverse, respectively.
The moment m is clockwise.

In such a case, it is not possible to obtain a moment m that circulates in the direction in which the objective lens 37 is to be moved, so that higher-order resonance cannot be prevented and a phase delay occurs. I will.

Further, as shown in FIG. 12, when L1 = L2, no reaction force S or the like is generated in each leaf spring 51, no moment m is generated on either side, and each leaf spring 51 is not generated. Since there is no movement of the action point G0 due to 51, each leaf spring 5
The arrangement according to 1 is very ideal.

However, since each leaf spring 51 has elasticity in practice, when the head base 30 having a predetermined weight is to be moved to either the left or right, the phase is Since a delay occurs, improvement of higher-order resonance of the head base 30 is incomplete.

FIG. 13 shows the characteristics of the servo gain and the phase when the interval between the leaf springs 51 in FIG. 10 is set to L1> L2. It can be seen that the phase lag has been greatly improved.

FIG. 14 shows each leaf spring 51 of FIG.
Shows the characteristics of the servo gain and the phase when the interval at is L1 <L2, and a large fluctuation is observed in the servo gain particularly in the region surrounded by the oblique lines. In addition, a large delay is seen in the phase characteristic that causes a large change in the servo gain.

FIG. 15 is a view for explaining the effect of the flow of the magnetic flux from the permanent magnet 13.
The corner 13a in which the left and right two corners on the surface side facing
And a yoke and an excitation coil from the permanent magnet 13.
A diffused magnetic flux is provided to the This allows
The same effect as the improvement of the higher-order resonance by each leaf spring 51 described above can be obtained.

That is, as shown in FIG.
When a current i flows leftward in each of the exciting coils 34 and 35 with respect to the magnetic flux B from No. 3, a driving force F (= ilB) is generated in a direction orthogonal to the magnetic flux B. At this time, in each of the excitation coils 34 and 35, a force O serving as a source of the downward and upward rotational movements is obtained, and thereby a leftward moment m is obtained in each of the excitation coils 34 and 35.

[0064] FIG. 17 shows a spring member for fixing the laser diode 3 and the grating 4 shown in FIG. 1 by the pickup case 2, the spring member 100
Is a base 10 that abuts a part of the pickup case 2
1 is provided. Further, the elastic members 102 and 10 having biasing forces in different directions are provided on the spring member 100.
3 are provided.

The elastic support 102 is provided with an insertion hole 104 for a screw (not shown) screwed into a predetermined position of the pickup case 2. The elastic support 103 has a through hole 10 through which the laser light from the laser diode 3 passes.
5 are provided.

The elastic support 10 of the spring member 100
2 and 103, the laser diode 3 and the grating 4 can be pressed and fixed in predetermined directions of the pickup case 2 in the directions of the arrows. After each is fixed, a screw inserted into the insertion hole 104 is screwed into a predetermined portion of the pickup case 2 so that the elastic support 10
Since the spring member 100 can be fixed via the second member 2, workability is greatly improved.

Conventionally, as shown in FIG. 18, the grating 4 is urged in the direction of the arrow by a spring 106 (a in the figure) or a leaf spring 107 (b in the figure), and the leaf spring 107 is fixed independently. I have. The laser diode 3 is provided with a leaf spring 108 as shown in FIG.
And the leaf spring 108 is fixed independently.

Therefore, since it is necessary to fix each of the spring 106 and the leaf springs 107 and 108 individually, not only the number of working steps increases, but also the adjustment of the position of the grating 4 or the laser diode 3 after the fixing is performed independently. Since it is necessary to loosen the fixed spring 106 or the plate springs 107 and 108, the workability is deteriorated.

FIG. 19 shows the half mirror 5 shown in FIG.
And shows a fixing spring member for attaching the mounting recess 2a of the pickup case 2, the engaging piece 109 having an engaging groove 108 of the screw 107 in a fixed spring member 106, engages the half mirror 5 at the time of mounting Combination fixed spring member 1
A holding piece 110 for holding the posture of the position No. 06 and an elastic piece 111 for urging the half mirror 5 in the direction of the arrow are provided.

In mounting, after dropping the half mirror 5 into the mounting recess 2a, the elastic piece 111 of the fixed spring member 106 is inserted into the gap of the mounting recess 2a. At this time, the holding piece 110 is engaged with the half mirror 5, and the posture of the fixed spring member 106 is stably maintained.
09 is engaged with the step 112, and the elastic piece 111 presses the half mirror 5 laterally.

Incidentally, conventionally, as shown in FIG. 20, the holding piece 110 provided on the fixed spring member 106 of FIG. 19 is not provided, and the elastic piece 111 of the fixed spring member 106 is attached to the mounting recess 2a. In many cases, the engagement piece 109 slips down from the step 112 when it is inserted into the gap, so that workability has been significantly impaired.

FIG. 21 shows the actuator unit 9.
The clamper base 70 is provided with a yoke base clamper 71 and a head base clamper 72.

The suspension base 20 and the head base 30 of the actuator unit 9 are clamped by a yoke base clamper 71 and a head base clamper 72, respectively. Each yoke base clamper 71
And the yoke base 2 by the head base clamper 72.
0 and the head base 30 are clamped in a state where the parallelism is accurately maintained.

The base 70 has an ear 6 of the leaf spring 51.
A pair of ear placement portions 73 for positioning the 0 are provided. The ear mounting portion 73 is provided with a positioning projection 74, and the positioning hole 62 of the ear 60 is fitted into the positioning projection 74 so that the suspension base 20 is provided.
The relative position of the leaf spring 51 with respect to the head base 30 is uniquely determined. In the drawing, reference numeral 80 denotes an applicator for applying a bonding material such as cream solder or a thermosetting adhesive having a short curing time, and reference numeral 81 denotes a laser irradiator for irradiating a laser beam.

Next, the procedure for assembling the actuator unit 9 will be described with reference to FIG.

First, in (procedure 1), the yoke base 10 to which the suspension base 20 is attached is set on the yoke base clamper 71. At this time, it is desirable that the clamping pressure by the yoke base clamper 71 is set to such an extent that the suspension base 20 does not float with respect to the yoke base 10, and it is further preferable that the clamping is performed so that the yoke base 10 and the suspension base 20 do not deform. . Thus, the clamp state accuracy enhanced et a flatness of the yoke base 10 and suspension base 20 and the like are performed.

In (procedure 2), the head base 30 is set on the head base clamper 72. By the clamping of the head base clamper 72, the accuracy of the flatness of the head base 30 is improved.

In (Procedure 3), the fixing part 2 of the suspension base 20 and the head base 30 is
A predetermined amount of solder is applied to 1, 22, 38 and 39. In addition, not only such solder but also a thermosetting resin having a short curing time as described above may be used. Then, the fixing part
A predetermined amount of solder is applied in advance to 21, 22, 38 and 39.
The solder terminals 91 and 90 are fixed by press-fitting.

In (Procedure 4), the positioning holes 62 of the ear portions 60 of the leaf spring 51 are fitted into the positioning protrusions 74 of the ear mounting portions 73. Thereby, the relative position of the leaf spring 51 with respect to the suspension base 20 and the head base 30 is uniquely determined.

In (procedure 5), the suspension base 20 and the head base 30 applied in (procedure 3) are used.
Are irradiated with laser light by a laser irradiator 81 to the fixing portions 21 and 38 on the front side of the laser beam. As a result, the pre-applied solder is melted, so that the fixing pieces 5 of the leaf spring 51 are fixed.
2 and 54 are fixed to the fixing portion 2 via the solder terminals 91 and 90.
1 and 38.

After the fixing pieces 52 and 54 of the leaf spring 51 have been fixed to the fixing portions 21 and 38 on the front side of the suspension base 20 and the head base 30, the same operation is performed on the rear side of the suspension base 20 and the head base 30. This is performed for the units 22 and 39.

In (procedure 6), after the fixing in (procedure 5) is completed, the middle part of the connecting piece 61 of the ear part 60 is cut.

In (procedure 7), the head base clamper 7
2 is removed. In (procedure 8), the fixing portion 2 of the suspension base 20
Re-irradiation of laser light by the laser irradiator 81 is performed only on the first and second 22. Thereby, the suspension base 2
While the solder in the fixing portions 21 and 22 of 0 is melted and fixed again within a short time, partial distortion due to the warpage of the leaf spring 51 is corrected as described above, and re-fixing is performed.

In (procedure 9), the objective lens 37 is attached to a predetermined position of the head base 30. As described above, in the present embodiment, the corner 13 a of the surface of the permanent magnet 13 facing the yoke 11 is cut and the opposed surface is smaller than the width dimension of the yoke 11, so that the magnetic flux heading toward the yoke 11 is formed. Was made to spread like a fan.

As a result, a moment m which circulates in the direction in which the head base 30 is to be moved can be obtained, so that the displacement between the driving center of each leaf spring 51 and the position of the center of gravity of the head base 30 can be offset. Therefore, high-order resonance generated in the head base 30 can be prevented.

[0086]

As described above, according to the pickup of the present invention, the permanent magnet facing the exciting coil is
It has corners with the left and right corners of the coil facing surface cut off.
The distance between the magnet and the exciting coil is
At the center of the left and right sides of the
The longest is that the permanent magnet is diffused with respect to the excitation coil.
The magnetic flux is applied. By that
The magnetic flux crossing the exciting coil can be inclined.
Move the drive point of the excitation coil
The center of gravity of the head base coincides with the drive center of the spring
To prevent higher order resonance of the head base.
Can be

As a result, it is possible to obtain a moment that circulates in the direction in which the head base is to be moved, so that it is possible to offset the displacement between the drive center of each suspension spring and the center of gravity of the head base. Higher-order resonance generated in the head base can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a conventional pickup.

FIG. 2 is a perspective view showing an actuator unit housed in a pickup case of the pickup of FIG.

FIG. 3 is an exploded perspective view showing the actuator unit of FIG. 2;

FIG. 4 is a view for explaining a flow of a magnetic flux from a permanent magnet provided in the actuator unit of FIG. 2;

FIG. 5 is a perspective view showing an actuator unit according to an embodiment of the pickup of the present invention.

FIG. 6 is an exploded perspective view showing the actuator unit of FIG.

FIG. 7 is a perspective view showing another example of the suspension spring of FIG. 5;

FIG. 8 is a perspective view showing the coil bobbin of FIG. 5;

FIG. 9 is a perspective view of another coil bobbin for explaining the operation of the coil bobbin of FIG. 8;

FIG. 10 is a view for explaining the operation of the leaf spring of FIG. 5;

FIG. 11 is a diagram for explaining the operation of the leaf spring of FIG. 5;

FIG. 12 is a view for explaining the operation of the leaf spring of FIG. 5;

FIG. 13 is a characteristic diagram for explaining a state where the servo gain and the phase are improved by the action of the leaf spring of FIG. 5;

14 is a characteristic diagram for explaining states of a servo gain and a phase due to the action of the leaf spring in FIG. 11;

FIG. 15 is a plan view for explaining the operation of the permanent magnet of FIG. 5;

16 is a diagram for explaining the direction of the magnetic flux from the permanent magnet and the direction of the moment acting on each exciting coil in FIG.

FIG. 17 is a perspective view showing a spring member for fixing the laser diode and the grating of FIG. 1 with a pickup case.

FIG. 18 is a perspective view showing another spring member for explaining the operation of the spring member shown in FIG. 17;

FIG. 19 is a view showing a spring member for pressing and fixing the half mirror of FIG. 1;

[20] Other for explaining the action of the spring member of FIG. 19
It is a figure showing a spring member.

FIG. 21 is a diagram illustrating an assembly process of the actuator unit of FIG. 5;

FIG. 22 is a view for explaining the procedure for assembling the actuator unit of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pickup 2 Pickup case 9 Actuator unit 10 Yoke base 11, 12 Yoke part 13 Permanent magnet 20 Suspension base 21, 22, 38, 39 Fixed part 30 Head base 33 Coil bobbin 37 Objective lens 51 Leaf spring 52 Fixed piece 60 Ear part 61 Connection Piece 80 flexible board 81 lead wire 82 land 83 positioning recess 90, 91, 92 solder terminal

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Takahashi 25-1, Nishimachi, Yamada-ji, Kawajie-shi, Saitama Prefecture Pioneer Corporation Kawagoe Plant (72) Inventor Jiro Morinaga 25-1, Nishimachi, Yamada-ji, Kawagoe-shi, Saitama Pioneer (56) References JP-A-64-7344 (JP, A) JP-A-2-94123 (JP, A) JP-A-2-132646 (JP, A) JP-A-3-41629 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 7/09 G11B 7/095

Claims (1)

(57) [Claims] 1. A method for reading information recorded on an information recording medium.
Equipped with an objective lens and an excitation coil for driving the head base
Head base cantilevered by suspension spring
Distance between the exciting coil and the exciting coil.
Provided by the electromagnetic action with the permanent magnet
A pickup driven in a racking direction, wherein the permanent magnet cuts off two right and left corners of an exciting coil facing surface.
Having a corner portion, the permanent magnet and the exciting coil
The separation distance should be the shortest at the left and right center of the exciting coil facing surface.
And the longest at both left and right ends of the exciting coil facing surface,
The permanent magnet is a magnetic flux diffused to the exciting coil.
Pickup, characterized in that it give.