JPH0150976B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical pickup device, and more particularly to an improvement in a magnetic circuit for axially moving a focusing lens that focuses laser light.

BACKGROUND ART An optical pickup device is a device for focusing a laser beam onto an information track of a disk-shaped information recording medium and detecting the returning laser beam reflected on the recording medium, and an example thereof is shown in FIG. In the figure, reference numeral 1 denotes a base having a projecting wall 2 protruding from one end. 3 and 3 are a pair of leaf springs extending in parallel from both side walls of the projecting wall 2; 4 is a cylinder fixed between the free ends of the leaf springs 3 and 3; 5 is a cylinder coaxially arranged within the cylinder 4; 4
A lens support tube is movably supported in the axial direction by support springs 6, 6 connected to both ends of the lens support tube, 7 is a focusing lens disposed inside the lens support tube 5, and 8 is a coaxial lens attached to the lower part of the lens support tube 5. A first coil 9 is wound around a first bobbin that is fixed to a first bobbin. 10 is a first yoke having a U-shaped cross section, a magnet 11 is fixed to one leg piece 10a, and a bottom surface 10b is attached to a base 1 with a bobbin 8 inserted between the magnet 11 and the other leg piece 10a.
It is fixed at The first coil 9 and the magnetically biased first yoke 10 form a first magnetic circuit. Reference numeral 12 designates a second bobbin fixed to the side surface of one leaf spring 3, around which a second coil 13 is wound. Reference numeral 14 indicates a second yoke fixed to a projecting wall 15 projecting from the base 1 and inserted into the second bobbin 12. The second coil 13 and the magnetically biased second yoke 14 constitute a second magnetic circuit.

Although not shown, a housing is fixed to the lower surface of the base 1, and the housing houses a laser light source, a photodetector, and an optical system excluding the objective lens 7, and the laser beam is transmitted to the first yoke on the base 1. 10 and 10 and supplied to the objective lens 7.

This device can move the objective lens 7 in the axial direction by passing an electric current through the first coil 9, and in the diametrical direction by passing an electric current through the second coil 13. The objective lens 7 can be positioned at an appropriate focus position depending on the warpage or eccentricity of the medium.

However, in the apparatus shown in FIG. 1, the first and second coils 9 and 13 and the first and second yokes 10 and 14 are separately provided, making it difficult to miniaturize the apparatus.

Therefore, by excluding the second bobbin coil yoke 12, 13, 14 and the protruding wall 15 shown in FIG. An annular second coil 16 is attached to the adjacent peripheral surface, and the objective lens 7 is moved in the axial direction by energization of the first coil 9, and the second
It has been proposed that the objective lens 7 is moved in the diametrical direction by energizing the coil 16.

Although this allows the device to be made more compact because the yoke 10 is shared, it is necessary to attach the second coil 16 across the corner of the first coil 9, which not only impairs the assembly work but also makes it difficult to assemble the yoke 10. 10 leg pieces of
Since the first and second coils 9 and 16 overlap between a and 10a, the leg piece 1 is
It is necessary to widen the 0a interval, and since the width of the second coil 16 is determined by the width of the first coil 9, the magnetic flux density interlinking with the second coil 16 is reduced, and the generated force is small. There were flaws.

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above-mentioned drawbacks, and provides an optical pickup device that is small and easy to assemble, eliminating the above-mentioned drawbacks.

The present invention has a pair of leg pieces protruding from the bottom in parallel, a protruding wall having a width narrower than the leg pieces between the leg pieces, and a magnetically biased yoke, which is coaxially wound around the protruding wall of the yoke, and the yoke is wound coaxially around the protruding wall of the yoke. a first coil that is movable in a direction along one inner surface; and a first coil that is wound and fixed to the first coil so that its axis is perpendicular to the axis of the first coil and its outer end surface is located within the wall surface of one side of the yoke leg. A coil block consisting of two coils, an objective lens coaxially fixed to the first coil, and a coil block consisting of the first and second coils.
and an elastic support member movably supporting the coil in the axial direction.

The present invention has the following effects due to the above configuration.

1. The yoke of the magnetic circuit that moves the objective lens in the axial and diametrical directions can be shared, making it possible to reduce the size and weight.

2. Co-winding of the first and second coils is easy, and the second coil can be easily attached to the first coil, and workability is good.

3. The first coil may be circular, and even if the first coil deviates from the center of the yoke, it will not be pulled back toward the center, making it easy to drive by the second coil.

4. The second coil is not limited to the width of the first coil and can be made large, and can be multi-layered, so the efficiency of the magnetic circuit is good.

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the present invention are shown below in Figures 3 and 4.
Let's explain from the diagram. In the figure, 17 is a housing with holes 17 coaxially formed on the upper surface 17a and the lower surface 17b.
c, 17d are drilled. 18 is York;
Leg pieces 18b and 18c are provided in parallel to protrude from the bottom 18a, and between the leg pieces 18b and 18c there is a protruding wall that is narrower in width than the width W of the leg piece, and in the illustrated example, a cylindrical protruding wall whose outer peripheral surface in the diametrical direction is flattened. 18d is installed protrudingly. yoke 18
A projecting wall 18d is housed in the housing 17 coaxially with the holes 17c and 17d. 19 is a first plate spring (elastic support member) arranged parallel to the legs 18b and 18c of the yoke and whose upper and lower ends are fixed to the housing 17 and can be torsionally deformed; 20 is a support plate fixed to the plate spring 19; 21a; ~21d has a support plate 20 at one end
The leg piece 18b, 1 is fixed to the side surface of the yoke and the other end is a yoke.
A second leaf spring (elastic support member) extends in parallel to the sides between 8c and the other end is swingable in the axial direction of the holes 17c and 17d. A first bobbin 22 is a bottomed cylindrical bobbin coaxially disposed on the projecting wall 18d of the yoke, and a first coil 23 is wound therein. 24 is leg piece 18
The first bobbin 22 is parallel to the opposing surfaces of b and 18c.
A second coil 25 is wound around a rectangular second bobbin that is fixed perpendicularly to the diametrically outer periphery of the bobbin and is disposed such that its circumferential surface is located between the leg pieces 18b and 18c. The first and second coils (coil blocks) 23 and 25 are fixed to the other ends of movable second leaf springs 21 and 21 by a first leaf spring 19. Magnets 26 and 26 are fixed to the inner surfaces of the leg pieces 18b and 18c to magnetically bias the yoke 18, and 27 is coaxially arranged on the bottom surface of the first bobbin 22 to direct the laser beam supplied from the hole 17d to the hole (not shown). The objective lens is shown focusing on the optical recording medium placed outside of 17c.

This operation will be explained below. A gap is provided between the projecting wall 18d of the yoke 18 and the first bobbin 22 so that the second coil 25 can move in the axial direction. When current is passed through the first coil 23, the first bobbin 22 moves in the axial direction of the magnetically biased protruding wall 18d of the yoke, deforming the second leaf spring 21, and moving the objective lens 27 along the optical axis. move in the direction. Further, the second coil 25 is connected to the protruding wall 18d of the yoke.
Portions 25a, 25a', 25b, 2 parallel to the axis of
5b' is located between the magnet 26 and the projecting wall 18d, so that the coil parts 25a, 2
At 5a', 25b, and 25b', the lines of magnetic force intersect with the axis of the coil 25 obliquely or perpendicularly. Therefore, when a current is passed through the coil 25, the portion 2 of the coil 25
5a, 25a', 25b, and 25b' are acted upon by a force in the direction of the arrow shown in FIG.
Move 7.

By passing current through the first and second coils 23 and 25 in this way, the objective lens 27 can be moved in the optical axis direction and in the direction perpendicular to the optical axis.

In this device, the magnetically biased yoke 18 for moving the objective lens 27 in the optical axis direction can be used in common with the yoke of the magnetic circuit for moving the objective lens 27 in the diametrical direction, and the device can be made smaller and lighter.

In addition, bobbins can be used for the first and second coils 23 and 25, and winding is easy, and in particular, the second coil 25 does not require any processing to deform.
3 is easy to install and has good assembly workability.

Further, the first coil 23 may be circular, and even if the first coil deviates from the center of the projecting wall 18d, it is difficult to be pulled back toward the center, so that driving by the second coil 25 is easy.

Further, the second coil 25 can be made larger without being limited by the width of the first coil 23, and the restrictions on the coil thickness are relaxed, so it can be multi-layered, thereby improving the efficiency of the magnetic circuit.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts showing an example of an optical pickup device, FIG. 2 is a perspective view of essential parts showing a modification of the device shown in FIG. 1, and FIG. 3 is an example of an optical pickup device according to the present invention. FIG. 4 is a perspective view of the main part, FIG. 4 is a view taken along the line AA in FIG. 3, and FIG. 5 is a plan sectional view of the main part for explaining the operation of the apparatus shown in FIG. 18... Yoke, 18a... Bottom, 18b, 1
8c... Leg piece, 18d... Projection wall, 19, 21...
Elastic support member, 23...first coil, 25...
Second coil, 27...objective lens.

Claims (1)

[Claims] 1. A housing, a yoke disposed within the housing, a pair of legs protruding from the bottom of the yoke in parallel, a magnet fixed to the inner surface of the legs for magnetically biasing the yoke, and a magnet between the legs. A protruding wall having a width narrower than the width of the leg piece is provided on the protruding wall, and a first coil movable in the axial direction and the width direction of the leg piece is disposed coaxially with respect to the protruding wall. a second coil that is perpendicular to the axis and is wound and fixed to the first coil so that its outer end surface is located within one side wall surface of the yoke leg; and an objective lens that is coaxially fixed to the first coil. a torsionally deformable first elastic support member arranged parallel to the leg of the yoke and whose upper and lower ends are fixed to the housing; and one end fixed to the first elastic support member via the support member. and a second elastic support member whose other end extends in parallel to the side between the legs of the yoke and supports the coil block movably in the axial direction of the first coil. .