JPH04134635A - Light pickup - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical head used for writing and reading compact discs (CDs), laser discs (LDs), optical storage discs, video discs, etc. ,
Hereinafter, those for reading, those for writing, and those for both writing and continuous output will be referred to as optical pink-up, and this patent shall apply to them.

[Conventional technology]

In order to improve the vibration resistance and impact resistance of optical pickups, optical pickups having mass-balanced actuators were invented, and are disclosed in (a) JP-A-63-271733 and (b) JP-A-1-199327. It is published as. As shown in FIGS. 6 and 7, each lens block (1
), a mass balance block (2), and a support block (3), which are connected by a parallel link (4) and whose mass is balanced around a support center. or(
Both a) and (b) have drive parts on both sides of the support center,
The driving moments are symmetrical about the center and equal in the same direction both in the front and rear.

However, in (a), the relative positions of the center of gravity, the center of the resultant force of the supporting force by the link (4), and the center of the resultant driving force are not defined for each of the lens block and the balance block, and in the illustrated example, they are not defined relative to each other. is seperated.

In addition, (mouth) stipulates that the support force resultant force by the link and the driving force resultant force are the same, but does not specify the relative relationship with the center of gravity position of each block, and the illustrated example clearly shows that The center of gravity is far apart, and it is difficult to make it coincide with the center of gravity in view of the claims that define the relationship between the magnet and the support block.

Displacement in the vertical (Z) direction is the same in both (a) and (b), but displacement in the horizontal (X) direction is determined by (a) the rotation of the link support block as a whole around one axis in the vertical direction. In contrast, (b) uses the same mechanism in the X direction as in the Z direction.

This patent is applicable to both mechanisms (a) and (b), regardless of this difference, and defines the basic structures of the lens block and balance prosif for a mass-balanced actuator.

[Problems with conventional technology]

In either the lens block or the balance block, the center of gravity, the driving force resultant vector, and the support force resultant vector due to the link must be on the same line, and if any of them deviates by 1', the driving direction of the block will change due to the drive This causes problems such as movement of the center of gravity to other directions and rotation around the center of gravity, causing the angle of the optical axis of the lens block with respect to the optical disk to tilt due to driving, and causing unnecessary resonance in the transmission characteristics. For this reason, both (a) and (b) have not yet been put into practical use.The present invention was obtained as a result of research and elucidation of the problems in practical application of (a) and (b).

Furthermore, due to the internal structure of the lens block and balance block, resonance in the high frequency range (100 Hz or more) occurs inside them, causing problems in the high frequency characteristics of the transfer function, and the focus tracking servo on the track of the optical system and the recorded image. There was a problem that it became incomplete.

[Problem to be solved by the invention]

In realizing the invention of the mass-balanced actuator, we focused on the movement and movement of the center of gravity when driving the lens block and balance block.
The first problem to be solved is to eliminate the resonance on the transfer function caused by rotation around the center of gravity, as well as the tilt of the optical axis during driving.
This is an issue.

The second problem is to suppress the occurrence of high-frequency resonance within both blocks.

[Means to solve the problem]

In a mass-balanced actuator, the problem can be solved by making the resultant vectors of the respective centers of gravity, driving force resultant force vector, and support force resultant vector of the link coincide with each other on the same straight line for the optical block and the mass-balanced block. In detail, the problem can be solved by adopting the structure described in claim 1. If the structure according to claim 2 is adopted, even higher accuracy can be obtained and it is perfect, but generally there is little need for this.

Suppressing the high-frequency resonance within both blocks can be solved by adopting the structure of claim 3.

[For production]

The resultant force vector of the driving force of the block and the resultant force vector of the supporting force from the link is on a straight line in the driving direction, and that line passes through the center of gravity of the block, so the center of gravity is not in the driving direction. 1-2), the resultant force vector, or 1-3)
Now, the driving force resultant vector and the supporting force resultant vector are 0 or more, which does not generate a rotational moment and cause no rotational movement of the block since the arm length is 0, which is the effect of claim 1.

If the structure of claim 1 is not completely satisfactory due to manufacturing errors, claim 2 has the effect of suppressing the adverse effects caused by the movement of the center of gravity due to the rotational moment generated thereby.

Claim 3 suppresses high-frequency resonance occurring within the block or in the link. 3-1), by using a highly rigid material such as PPS for the block and making the structure as rigid as possible, the resonance can be increased to a higher ultra-high frequency (> 10
kHz), and using materials such as Hytrel (DuPont) and Perbrene (Toshi) for the link,
Its viscoelasticity absorbs and damps vibrations in the ultra-high frequency range. Further, the structure of the link is generally made of a thin or thin member with a low section modulus and a long length, and its primary bending resonance is dominant. However, if the masses and driving forces of both blocks are precisely balanced, the primary bending resonance will be completely suppressed. Even if such high-order resonance occurs, the viscoelasticity of the material absorbs and suppresses it.

3-2) takes advantage of the fact that when there is a slight unbalance between the mass and driving force of both blocks due to manufacturing errors, a rigid link material is less likely to cause primary resonance. ing.

In that case, in order to absorb and suppress minute residual first-order resonance, its higher-order resonance, and high-frequency resonance within the block, objects made of highly viscoelastic material may be embedded in a part of the block or link, and the higher-order and high-frequency vibrations may be distorted. This problem can be solved by coating a large portion of the surface.

3-3) is to use a hinge that utilizes the bending of the thin-walled part of a conventional viscoelastic material, or a shaft that utilizes the torsion of the thin-walled or narrow-diameter part at the connection point between the link and the block. are separated. This connection point generally has a structure with a thick wall that extends into the two connected members around it, and by making this thick wall the necessary volume and shape, it can be shared as the vibration absorption part in 3-2). be. In this case, both the block and the link can be made of a rigid material.

〔Example〕

FIG. 1 is a longitudinal sectional view and a plan view of an example in which claim 1 and claim 3-1) of the present invention are implemented.

FIG. 2 is an exploded view and also shows how to assemble it.

(1) is a lens block, which is made of PPS material and consists of an objective lens (1-1), a magnet (5-3), and a yoke (5-2).

(2) is a balanced block made of PPS and magnet (5-3
), yoke (5-2).

(3) is a support block made of PPS and has a slit to hold the coil (5).

Parallel links (4) are made of highly viscoelastic materials such as Hytrel and Pelprene, and connect points (4-1) and (4-
2), (4-3), (4-4), (4-5).

(4-6), etc. are connected to (1), (2), and (3). The connection points are thin and easily bend to act as hinges (4-1)... (4-
6) and a similar lower link connecting point (not shown), the lens can be displaced from side to side (tracking). A similar hinge, not shown, is utilized for vertical (focusing) displacement. A second exploded view is shown to show the specific structure of the details.
As shown in the figure. The figure also shows the assembly method.

(5) is a coil for vertical drive (focusing);
5-1) is a coil for left and right drive (trunking).

The connection points (4-3), (4-4) and the corresponding connection points of the lower link not shown are
(both are orthogonal at 01) is on the plane determined by
During tracking driving, the resultant support force of the block (1) from the link is a vector parallel to the driving direction at the center of the tracking coil (5-1) within the Xl-○, -Z1 plane. Further, the reaction force of the force (5-1) received from the magnetic field becomes the driving force resultant vector applied to the magnet. This driving force resultant vector is a vector in the driving direction, with the point of force applied between the two coils (51) within the X, -O, -Z planes. The center of gravity of block (1) is also located within the plane XIo, -2, and is designed to be at the point of force of the resultant driving force vector. That is, the resultant force of the center of gravity, the resultant driving force, and the resultant supporting force lies on a straight line in the driving direction passing through the point (O1). In the illustrated example, both the driving force resultant force itself and the supporting force resultant force themselves are on a straight line passing through (O,) in the driving force direction.

The same applies to the balanced block.

The center of the support block is point (O), and the centers of gravity of blocks (1) and (2) are located at the 1st position of front-back symmetry with respect to point (O), and mass balance is established because their masses are equal. . Also, the resultant driving force is equal in magnitude for both blocks, is equidistant from point (○), and has the opposite direction, so regarding point (○),
Creates a rotation moment of the same magnitude in the same direction.

The same applies to vertical driving (focusing).

The above description shows that claims 1 and 3-1) are realized. This is an improvement over the prior art (b) according to the present invention.

It is easily shown in other embodiments that similar improvements can be made to the prior art (a). So Hachi 1st
This can be realized by replacing the dashed-dotted line portion in the figure with the dashed-dotted line portion in FIG. FIG. 3 shows a YZ cross section and an XY cross section passing through point (O).

(4-30) is a member that connects the left and right link members (4). The vertical link member (4-30) is connected to the vertical member (3-2) through a thin hinge (4-31) for vertical displacement, and (3-2) serves as a vertical rotation wheel for horizontal displacement. connected to the support piece (3-4) via the hinge (3-3);
(3-4) is put into the floor base mounting part (6). (O)
A hinge (3-3) is provided on a straight line in the Z direction passing through the point,
A hinge (4-31) is provided on a plane parallel to planes X, -O, and -Z passing through (O). (3-2) (3-
4) is a support block, in this case a hinge for left and right rotation (3)
-3).

Although the above-illustrated example is an example in which the objective lens is displaced vertically and horizontally, it is also possible to drive a combination of lenses and mirrors, or the entire optical system, etc., for displacement all at once.

Furthermore, although the above illustrated example is an example in which the coil is fixed to a base and the magnet is driven to be displaced, it is also possible to conversely have the magnet fixed and the coil installed in a lens block or a balance block so that the coil is displaced as a unit. Of course.

FIG. 4 is a vertical cross-sectional view showing an embodiment of claim 2,
Block (3) and link (4) are omitted. 1st
The lens block (1) and balance block (2) shown in the figure have been changed to structures having principal points of second-order moments of inertia at the centers of gravity (41) and (42), respectively. This can be realized by making each structure as symmetrical as possible with respect to the centers of gravity (41) and (42) as shown in the figure. In addition, blocks (1) and (2) are point symmetrical with respect to point (○), and the principal point of the entire second-order moment of inertia is at point (○), which is the center of gravity and the center of the movable part of the entire actuator. It's supposed to match.

Figures 5a and 5b are embodiments of claim 3-2),
FIG. 5C is an embodiment of claim 3-3). Figure 5a shows PPS in the link member (4) made of Pervrene.
This is an example in which aggregate (51) is added.

The aggregate has a structure that has been passed through insert molding, two-color molding, etc. Figure 5 shows a lens block that absorbs and damps the bending vibration of the lens frame and the U-shaped tuning fork-shaped bending vibration of the magnet frame.
This is an example in which a Pervrene coating is provided on the surface.

FIG. 5C shows an example in which only the connecting part (54) including the hinge and its surroundings as a connecting point between the lens stand (1) and the link (4) is made of Pervrene material, and the other parts are made of PPS material.
Corresponds to -3).

〔Effect of the invention〕

The mass-balanced actuator, which was difficult to realize due to unclear points in the conventional technology, has been developed by the present invention, which suppresses resonance in the high and ultra-high frequencies of the transfer characteristic and minimizes the tilt of the optical axis due to driving. As a result, it has become possible to put it into practical use, and it has become possible to realize an optical pickup that has two major advantages: excellent vibration and shock resistance as a mass-balanced type, and complete freedom in mounting and operating posture. .

[Brief explanation of the drawing]

1 and 2 are one embodiment of claims 1 and 3-1) of the present invention, and FIGS. 1 and 3 are other embodiments of the same. FIG. 4 is a vertical longitudinal sectional view showing an embodiment according to claim 2 of the present invention. FIG. 5 is a sectional view of a portion showing the third embodiment. (1) is a lens block. (1-1) is an objective lens. (
2) is a balance block, (3) is a support block, (3-2
) is a vertical member (3-3) connecting the upper and lower link connecting members (4-30) is a pivot hinge for left and right movement, (3-4) is a support piece, and (4) is a parallel link. (4-1) (4-2)... are connecting points, (5) is a driving unit focusing coil, (5-1) is a tracking coil, (5-2) is a yoke, (5-3) is a permanent magnet. (6
) is the base mounting part, (O) is the center of the actuator, (O
1) is the center of the lens block, (41). (42) are the centers of gravity of the lens block and balance block, respectively;
(51) is aggregate, (52) and (53) are viscoelastic coatings,
(54) is a connecting portion. FIGS. 6 and 7 are examples of prior art.

Claims (1)

[Claims] 1. It has an optical block (1), a balance block (2), and a support block (3), and (1) and (2) are arranged at least in the vertical (Z, focusing) direction or in the horizontal (X, focusing) direction. Seesaw-like (tracking) direction with the support block as a fulcrum (
Connect (1), (2) and (3) by a parallel link (4) that allows movement while keeping 1) and (2) parallel, and with respect to the link center (O) point of (3), (1) and (
2) In an optical pickup having a mass-balanced actuator whose primary moment is mass-balanced around at least one axis vertically (Z), horizontally (X), and longitudinally (Y), the actuator is ) and 2) or 1) and 3). 1), blocks (1) and (2) each have at least z or
A drive means that drives itself in either direction, with a structure in which the driving force resultant vector, the supporting force resultant force vector from the link, and the center of gravity are approximately on the same line. 2. An optical pickup according to claim 1, characterized by having at least one of the following structures. 1) A structure in which the center of gravity of at least one of blocks (1) and (2) substantially coincides with the principal point of the second-order moment of inertia. 2) A structure in which the second-order moment around point (O) of block (1) and the second-order moment around point (O) of block (2) are symmetrical with respect to point (O) and are approximately equal. 3. An optical pickup according to claim 1, characterized by having one of the following structures. 1) A structure in which at least one of the blocks (1) and (2) is made of a highly rigid material, and the link (4) is made of a soft material with high viscoelasticity and low rigidity. 2) A structure in which at least one of the blocks (1) and (2) is rigidly constructed, and a portion thereof has a vibration absorbing portion made of a soft material with high viscoelasticity or a vibration absorbing coating. (There is no question of whether the link (4) is rigid or flexible.) 3) In the above claim 3-2), the block (1)
), or the connection point between (2) and the link (4) is constructed of a thin hinge or small diameter shaft made of flexible material, and the connection point is freely rotatable by bending or twisting, and the connection point and the surrounding soft material are connected. A structure in which the connecting part is shared as the vibration absorbing part in 3-2).