JPH01151024A - Optical pick-up actuator - Google Patents

Abstract

PURPOSE:To execute the focusing tracking without inclining a lens holder, to facilitate the assembling and to attain the miniaturization by providing a groove to extend in a focusing direction, laying plural balls to the groove, and pressing a moving part in a fixing part direction. CONSTITUTION:When a current flows at a focusing coil 53, an electromagnetic force acts, a lens holder 51 is guided to grooves 51d and 55b through a ball 60, moved in the direction of an arrow F and focusing is executed. When the current flows at a tracking coil 61, the electromagnetic force acts, a lens holder 51 is swayed in the direction of an arrow T with the center of the ball 60 and the tracking is executed. Namely, since the moving part such as the lens holder 51 is pressed through plural balls 60 to a lens holder guiding member 55, which is the fixing part, the inclination due to the clearance is eliminated. Thus, a smooth focusing operation and a tracking operation can be obtained, assembling is facilitated and miniaturization can be executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical pickup actuator used in compact discs, video discs, optical memory disks capable of both recording and playback, etc. It consists of a movable part, a fixed part, and a support part that movably supports the movable part, and one of the movable part and the fixed part is provided with a magnet, and the other is provided with a coil, and a current is applied to the coil. The present invention relates to an optical pickup actuator that moves the movable part by supplying it and performs focusing and tracking.

(Background of the invention) Next, a conventional example will be explained using the drawings.

First, a first conventional example will be explained using FIGS. 9 and 10. In the figure, the disk is placed at the top.

Reference numeral 1 denotes a lens holder which is a movable part and is provided with an objective lens 2 for converging laser light onto the disk. A focusing coil 3 is wound around the side surface of the lens holder 1. Reference numeral 4 denotes a magnetic substrate serving as a fixed portion, and a shaft 5 is erected on the substrate 4. The lens holder 1 is fitted onto the shaft 5 so as to be movable in the axial direction (focusing direction) of the shaft 5 on the fixed portion side, and to be rotatable relative to the shaft 5 (in the tracking direction). The lens holder 1 is provided with a first through hole 1a and a second through hole 1b. The inner yoke 6 and the second inner yoke 7 are fitted into each other.

8 is a first magnet provided on the substrate 4 so as to face the first yoke 6 through the lens holder 1, and whose magnetization direction is horizontal; 9 is a first magnet that is connected to the second yoke 7 through the lens holder 1; The second
It is a magnet. A first outer yoke 10 is provided on the first magnet 8 on the opposite lens holder 1 side, and a second outer yoke 11 is provided on the second magnet 9 on the opposite lens holder 1 side, respectively, on the substrate 4. There is. Further, the focusing coil 3 is provided with tracking coils 12, 13, 14.15 (tracking coil 14.15 is not shown). Further, as shown in FIG. 10, the lens holder 1 has one end connected to the substrate 4.
It is supported by a projection 4a provided above via a damper 16 which is a support portion.

and the first magnet 8. First outer yoke 10. A first magnetic circuit is formed by the substrate 4 and the first inner yoke 6, and the first
A magnetic field is generated between the magnet 8 and the first inner yoke 6. Also, the second magnet 9. Second outer yoke 11. Board 4
A second magnetic circuit is formed by the second inner yoke 7 and a magnetic field is generated between the second magnet 9 and the second inner yoke 7.

This type is called a sliding type optical pickup actuator.

Next, the operation of the above configuration will be explained. When a current is applied to the focusing coil 3, an electromagnetic force acts on the focusing coil 3, and the lens holder 1 moves in the direction of arrow X in FIG. 1, thereby performing focusing. Further, when current is applied to the tracking coils 12 to 15, an electromagnetic force acts on the tracking coils, and the lens holder 1 rotates in the direction of arrow θ (tracking direction) in FIG. 9, thereby performing tracking. And focusing coil 3
When the current flowing through the tracking coils 12 to 15 is cut off, the elasticity of the damper 16 causes the lens holder 1 to return to the neutral point.

Next, a second conventional example will be explained using FIG. 11.

In the figure, the disk is placed at the top.

21 is an objective lens 2 that converges the laser beam onto the disk.
2 is a movable part of the lens holder. A focusing coil 23 is wound around the side surface of the lens holder 21, and two plates 24 are attached to the wound focusing coil 23. Reference numeral 25 denotes a substrate serving as a fixing portion having a base portion 25a and a standing wall portion 25b. The lens holder 21 is supported by four support wires 26, which are fixed at one end to the vertical wall portion 25b of the substrate 25 and at the other end to the plate 24.

The surface of this support wire 26 is covered with a damping material such as silicone rubber. The lens holder 21 has a first through hole 21a and a second through hole 7t 2 l b each having a rectangular cross section. And those first through holes 21a
The base portion 25a of the substrate 25 is inserted into the second through hole 21b.
The first inner yoke 27 and the second inner yoke 2 provided above
8 are inset. 29 is a lens holder 21
The first magnet is provided on the base portion 25a of the substrate 25 so as to face the first inner yoke 27 via the side portion 21C, and has a horizontal magnetization direction. A second magnet 30 is provided on the base portion 25a of the substrate 25 so as to face the second inner yoke 28 via the side portion 21d of the lens holder 21, and has a horizontal magnetization direction.

A first (7) magnet is placed on the side opposite to the lens holder 21 of the first magnet 29.
The outer yoke 31 is attached to the anti-lens holder 21 of the second magnet 30.
On the sides, second outer yokes 32 are provided on the base portions 25a of the substrates 25, respectively.

Also, 33, 34, 35.36 are tracking coils (3
5 and 36 are not shown). And the first magnet 29
．． First outer yoke 31. A first magnetic circuit is formed by the base portion 25a of the substrate 25 and the first inner yoke 27.
A magnetic field is generated between the magnet 29 and the first inner yoke 27. Also, the second magnet 30. Second outer yoke 32.
A second magnetic circuit is formed by the base portion 25a of the substrate 25 and the second inner yoke 28, and the second magnet 30 and the inner yoke 28 form a second magnetic circuit.
A magnetic field is generated between the two. There are 4 types like this
This is called a wire-type optical pickup actuator.

Next, the operation of the above configuration will be explained. When a current is supplied to the focusing coil 23, the focusing coil 23
An electromagnetic force acts on the lens holder 21 having the focusing coil 23 in the direction of the arrow X (
(focusing direction) and focusing is performed. Furthermore, when a current is supplied to the tracking coils 33 to 36, an electromagnetic force acts on the tracking coils 33 to 36, and the lens holder 21 moves in the arrow y direction (tracking direction) in FIG. 11, and tracking is performed. . Then, when the current flowing through the focusing coil 23 and the tracking coils 33 to 36 is cut off, the support wire 2
6, the lens holder 21 returns to the neutral point.

Next, a third conventional example will be explained using FIG. 12. This example is similar to a four-wire optical pickup actuator and uses four leaf springs instead of four support wires. In the figure, 41 is a lens holder which is a movable part and has an objective lens 42. The lens holder 41 is provided with a focusing coil and a tracking coil as in FIG. 11, but these are omitted in the figure. 43 is a substrate serving as a fixed portion. Reference numeral 49 denotes a support portion consisting of four leaf springs 44 to 47 and an intermediate member 48 having leaf springs 44, 45 and 46, 47 at both ends. Here, the leaf springs 44 and 45 have flexibility in the direction of arrow X (focusing direction), and the leaf springs 45 and 46 have flexibility in the direction of arrow y (tracking direction). Furthermore, a damping material such as silicone rubber is applied to the surface of each of the leaf springs 44 to 47. The lens holder 41 is supported by the substrate 43 via a support portion 49 . This type is called a leaf spring type optical pickup actuator.

Next, the operation of the above configuration will be explained. When a current is supplied to a focusing coil (not shown), an electromagnetic force acts on the focusing coil, and the lens holder 41 having the focusing coil moves in the direction of arrow X (focusing direction) in FIG. 12, thereby performing focusing.

Further, when a current is supplied to a tracking coil (not shown), an electromagnetic force acts on the tracking coil, and the lens holder 41 moves in the direction of the arrow y (tracking direction) in FIG. 12, thereby performing tracking.

Then, when the current flowing through the focusing coil and the tracking coil is cut off, the lens holder 41 returns to the neutral point due to the elasticity of the leaf springs 43 to 46.

(Problem to be solved by the invention) The three conventional examples having the above configurations have the following problems.

(2) Sliding optical pickup actuator Since the lens holder 1 moves in the vertical direction along the shaft 5, a gap is required between the shaft 5 and the lens holder 1. Therefore, the lens holder 1 is not parallel to the disk, causing problems such as increased jitter and deterioration of the C/N ratio.

In order to improve this parallelism, it is necessary to lengthen the sliding part of the lens holder 1 (height of the lens holder 1), which increases the height of the lens holder 1 and increases the size of the actuator. There are also problems.

In addition, since the lens holder 1 moves while sliding with respect to the shaft 5, there is a large frictional resistance and lacks smoothness.
There is a problem that the N ratio deteriorates. If the shaft 5 is coated (eg, coated with fluorocarbon resin) in order to reduce this frictional resistance, there is also the problem that the number of manufacturing steps increases.

Furthermore, in order to perform focusing while the lens holder 1 remains parallel, it is necessary to
There is also the problem that it is necessary to configure two magnetic circuits, which increases the size of the actuator.

04-Wire Type Optical Pickup Actuator A so-called rolling phenomenon occurs in which the lens holder 21 tilts in the direction of rotation during focusing and tracking operations. In order to suppress this phenomenon, it is necessary to precisely align the center of gravity of the movable part, the point of application of the driving force of the focusing coil 23° tracking coils 33 to 36, and the point of application of the force of the support wire 26. However, there is a problem in that it is extremely difficult to realize this.

Furthermore, the smaller the actuator is, the smaller the elastic force of the support wire 26 is required, which means that the strength of the support wire 26 is reduced. There is a problem in that it is very difficult to accurately attach the weak support wire 26 without distortion.

Furthermore, in order to remove the high-order resonance of the support wire 26 itself, the support wire 26 needs to be covered with a damping material.
Another problem is that it is difficult to attach the damping material because the strength of the support wire 26 is weak.

Furthermore, in order to perform focusing while the lens holder 21 remains parallel, it is necessary to configure two magnetic circuits symmetrically with respect to the lens holder 21, which poses the problem of increasing the size of the actuator. .

■ Leaf spring type optical pickup actuator This type does not cause rolling phenomenon, but like the four-wire type optical pickup actuator, it has the problem that if the actuator is made smaller, it will be difficult to assemble the leaf spring.

The present invention was made in view of the above problems, and its purpose is to provide an optical pickup actuator that can perform focusing and tracking without tilting the lens holder (movable part), is easy to assemble, and can be made compact. It is about realization.

(Means for Solving the Problems) The present invention for solving the above problems includes a movable part having an objective lens, a fixed part, and a support part movably supporting the movable part. In an optical pickup actuator, a magnet is provided on one of a part and a fixed part, and a coil is provided on the other, and the movable part is moved by supplying current to the coil to perform focusing and tracking. A plurality of balls are formed in the grooves, facing each of the fixed parts and extending in the focusing direction, and the movable part is pressed in the direction of the fixed part using the supporting part. This is a characteristic feature.

(Function) In the optical pickup actuator of the present invention, the movable part pressed toward the fixed part by the support member is
The movable part and the fixed part move smoothly in the focusing direction and the tracking direction by a plurality of balls interposed in grooves in the focusing direction carved on opposing surfaces of the movable part and the fixed part.

(Example) Next, the present invention will be explained in detail using the drawings.

First, a first embodiment will be described using FIGS. 1 to 3. In the figure, reference numeral 51 denotes a lens holder, which is a movable part, and has an objective lens 52 in the center thereof, which converges the laser beam onto the disk. An arm portion 51 that grips the focusing coil 53 is provided at one end of the lens holder 51.
a and 51b are provided. Reference numeral 54 denotes a base serving as a fixed part, and a lens holder guide member 55 is mounted on this base 54.
and an inner yoke 5 that fits into the focusing coil 53.
6 and an outer yoke 57 are provided. outer yoke 57
A magnet 58 whose 1 m direction is horizontal is disposed on the focusing coil 53 side. And base 54. Inner yoke 56. A magnetic circuit is formed by the outer yoke 57° and the magnet 58, and a magnetic field is generated between the magnet 58 and the inner yoke 56. A V-shaped groove 51d is carved in the focusing direction (indicated by arrow F in FIG. 2) on a surface 51c of the other end of the lens holder 51 that faces the lens holder guide member 55. Further, a V-shaped groove 55b opposite to the groove 51d is carved in a surface 55a of the lens holder guide member 55 that faces the opposite surface 51C of the lens holder 51.

A plurality of balls 60 (two in this embodiment) are arranged in these two grooves 51d and 55b.

59 is a base portion 59a and two arm portions 59b and 59c.
This damper is a support part made of silicone rubber or the like and is approximately U-shaped. A base portion 59a of this damper 59 is fixed to the lens holder guide portion 55, and arm portions 59b, 59
The tip end of c is fixed to the lens holder 51, and applies a pressing force to the lens holder 51 in the direction of the lens holder guide N355. 61 is a tracking coil disposed on the focusing coil 53.

Next, the operation of the above configuration will be explained. When a current is applied to the focusing coil 53, an electromagnetic force acts on the focusing coil 53, and the lens holder 51 having the focusing coil 53 is moved through the grooves 51d and 55b via the ball 60.
2, the lens moves in the direction of arrow F in FIG. 2, and focusing is performed. In addition, the tracking coil 61
When a current is applied to the tracking coil 61, an electromagnetic force acts on the tracking coil 61, and the lens holder 51 swings in the direction of arrow T in FIG. 1 about the center of the ball 60, thereby performing tracking. Then, when the current flowing through the focusing coil 53 and the tracking coil 61 is cut off, the lens holder 51 returns to the neutral point due to the elasticity of the damper 59.

According to the above configuration, the movable parts such as the lens holder 51 are pressed against the lens holder guide member 55, which is a fixed part, through the plurality of balls 60. The slope will disappear. In addition, the lens holder 51 and the lens holder guide member 55
Since the friction between the ball 60 and the ball 60 is rolling friction caused by the rotation of the ball 60, it is extremely small, and smooth focusing and tracking operations can be obtained, and the C/N ratio is also improved. Furthermore, since no wires or leaf springs are used as the support, assembly is easy. Also.

Since the lens holder 51 is supported via the plurality of balls arranged in the grooves 51d and 55b, no rolling phenomenon occurs. Incidentally, a gain diagram in the focus direction of this embodiment is shown in FIG. 4, a phase diagram in FIG. 5, a gain diagram in the tracking direction in FIG. 6, and a phase diagram in FIG. 7. As can be seen from these figures, good results can be obtained even if the center of gravity of the movable part, the point of application of the driving force by the coil, and the support point of the damper do not coincide, so that the actuator can be made smaller. Furthermore, since only one magnetic circuit is required, the actuator can be made smaller.

Note that this embodiment is not limited to the above configuration.

For example, in the above configuration, the groove 55b of the lens holder guide member 55 is V-shaped, but it may be U-shaped. Also,
In the above embodiment, the center of gravity of the movable part, the point of application of the driving force by the coil, and the support point of the damper are not made to match, but they may be made to match, and by making them match, higher precision can be achieved. Needless to say, it will become an excellent actuator.

Furthermore, in the above embodiments, the configuration in which the movable part is a coil and the fixed part is a magnet (generally referred to as a moving coil type actuator) was explained, but conversely, the configuration in which the movable part is a magnet and the fixed part is a coil (generally referred to as a moving coil type actuator) is explained. An actuator (referred to as a moving magnet type actuator) may also be used.

Next, a second embodiment of the present invention will be described using FIG.

In the figure, reference numeral 71 denotes a lens holder, which is a movable part, and has an objective lens 72 at one end for converging laser light onto the disk. A focusing coil 73 is attached to the other end of the lens holder 71. Reference numeral 74 denotes a base that is a fixed part, and on this base 74 are an inner yoke 76 that fits into the focusing coil 73 and an inner yoke 7.
Two outer yokes 77 are provided at both ends of the yoke 6. A magnet 78 whose magnetization direction is horizontal is disposed on the focusing coil 73 side of the outer yoke 77 . And base 74. Inner yoke 76° Outer yoke 77.1m
A magnetic circuit is formed by the stone 78, and the magnet 78 and the inner yoke 76
A magnetic field is generated between the two. A V-shaped groove 71b is formed on the surface 71a of the lens holder 71 facing the inner yoke 76 in the focusing direction (perpendicular to the plane of the paper in FIG. 8).
is engraved on. Further, a V-shaped groove 76b facing the groove 71b is carved in a surface 76a of the inner yoke 76 that faces the surface 71a of the lens holder 71. and,
A plurality of balls 80 (
In this embodiment, two) are provided. 79 is
The damper is a support portion that is fixed to the lens holder 71 at one end and to the outer yoke 77 at the other end. This damper 79
applies a pressing force to the lens holder 71 in the direction of the inner yoke 76 . 81 is a tracking coil disposed on the focusing coil 73.

Next, the operation of the above configuration will be explained. When a current is applied to the focusing coil 73, an electromagnetic force acts on the focusing coil 73, and the lens holder 71 having the focusing coil 73 is moved through the grooves 71b and 76b via the ball 80.
, and moves in a direction perpendicular to the page in Figure 8.
Focusing is done. Further, when a current is applied to the tracking coil 81, an electromagnetic force acts on the tracking coil 81, and the lens holder 71 swings in the direction of arrow T in FIG. 8 about the center of the ball 80, thereby performing tracking. Then, when the current flowing through the focusing coil 73 and the tracking coil 81 is cut off, the damper 79
The lens holder 71 returns to the neutral point due to its elasticity.

According to the above configuration, the movable parts such as the lens holder 71 are pressed against the inner yoke 76, which is the fixed part, through the plurality of balls 80, so that the tilt due to the gap is prevented as in the above-mentioned sliding type optical pickup actuator. It disappears. Moreover, Il! between the lens holder 71 and the inner yoke 76! Since the friction is caused by rolling friction caused by the rotation of the ball 80, it is extremely small, and smooth focusing and tracking operations can be obtained, and the C/N ratio is also improved. Furthermore, since no wires or leaf springs are used as the support, assembly is easy. Furthermore, since the lens holder 71 is supported via the plurality of balls disposed in the grooves 71b and 76a, no rolling phenomenon occurs.

In addition, since the objective lens 72 is disposed at the end of the lens holder 71, even if the optical system is located laterally to the actuator, there is nothing blocking the beam, so the beam can easily enter the objective lens through a prism etc. This is very advantageous when reducing the overall height of the device. In addition, good results can be obtained even if the center of gravity of the movable part, the point of application of the driving force by the coil, and the support point of the damper do not coincide, so that the actuator can be made smaller.

Note that this embodiment is not limited to the above configuration.

For example, the groove 76b may be a U-shaped groove. In addition, in the above embodiment, the center of gravity of the movable part, the point of application of the driving force by the coil, and the support point of the damper are not made to coincide, but they may be made to coincide, and by making them coincide, it is possible to improve the Needless to say, it becomes a highly accurate actuator. Furthermore, in the above embodiments, the configuration in which the movable part is a coil and the fixed part is a magnet (generally referred to as a moving coil type actuator) was explained, but conversely, the configuration in which the movable part is a magnet and the fixed part is a coil (generally referred to as a moving coil type actuator) is explained. An actuator (referred to as a moving magnet type actuator) may also be used.

(Effects of the Invention) As described above, according to the present invention, an optical pickup actuator that can perform focusing and tracking without tilting the lens holder (movable part), is easy to assemble, and can be miniaturized is realized. can do.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a first embodiment of the present invention, Fig. 2 is a side view in Fig. 1, and Fig. 3 is an A-A in Fig. 1.
4 is a gain diagram in the focus direction of the first embodiment, FIG. 5 is a phase diagram, FIG. 6 is a gain diagram in the tracking direction of the first embodiment, and FIG. 7 is a phase diagram. Diagram, No. 8
The figure is a plan view showing the second embodiment, FIG. 9 is a perspective view showing the first conventional example, FIG. 10 is a sectional view of FIG.
FIG. 1 is a perspective view showing a second conventional example, and FIG. 12 is a configuration diagram showing a third conventional example. 51.71... Lens holder 51d, 55b, 71b, 76b... Groove 52.72.
...Objective lens 53.73...Focusing coil 54.74...
・Base 55... Lens holder guide member 56.76... Inner yoke 57.77... Outer yoke 58.78... Magnet 59.79... Damper 6
0,80... Ball 61.81... Tracking coil patent applicant Konica Co., Ltd.
Ceremony Clerk Patent attorney Fuji Ijima 1 person Tube 71 mouths Q, (111 turns,, 1 [J (ni l-1z) tube 8 figures 73 Fuga casing coil angle etc. 9 figures tube 10 figures X 餉 g11 in four

Claims (1)

[Claims] Consisting of a movable part having an objective lens, a fixed part, and a support part that movably supports the movable part, one of the movable part and the fixed part has a magnet, and the other has a magnet. A coil is installed in the
In an optical pickup actuator that moves the movable part and performs focusing and tracking by supplying current to the coil, grooves are formed facing the movable part and the fixed part, respectively, and extending in the focusing direction; An optical pickup actuator characterized in that a plurality of balls are interposed in the groove, and the movable part is pressed toward the fixed part using the support part.