JPH0333936Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a small optical pickup installed in a compact disc player or the like.

[Prior art]

6 and 7 schematically show a conventional optical pickup.

Reference numeral 1 is an objective lens. This objective lens 1
A lens barrel 2 holding the lens is supported on a lens holding member 3. This lens holding member 3 is held in the X direction (tracking servo direction) and Y direction by a leaf spring or the like.
It is supported for fine movement in the direction (focus servo direction). On both sides of the lens holding member 3, a focus coil 4 wound into a rectangular cylinder shape and a tracking coil 5 closely attached to the outside thereof are provided. Further, a base (not shown) is provided with a yoke 6 that sandwiches each coil 4 and 5, and a magnet 7 is held in this yoke 6. The lens holding member 3 is corrected and driven in the Y direction by the current flowing laterally in the focus coil 4 and the magnetic field formed by the magnet 7. Further, the lens holding member 3 is corrected and driven in the X direction by the current flowing vertically in the tracking coil 5 and the magnetic field.

Further, a prism 8 is provided below the objective lens 1. On the optical axis on the side of this prism 8, a laser diode 9, a beam splitter 10, a collimating lens 11, and a quarter wavelength plate 12 are arranged.
Optical members such as the following are provided. The laser beam emitted from the laser diode 9 passes through each optical member 10, 11, 12, is reflected by the prism 8, and is sent to the objective lens 1, which focuses it on the recording surface of the optical disk. A beam spot is formed. The beam reflected from the recording surface of the optical disk returns along the path and is reflected by the beam splitter 10. and,
Photodiode 13 located in the direction of reflection
The reflected light is now detected by

[Problems with conventional technology]

In the conventional optical pickup described above, coils 4 and 5 for driving the objective lens and members 6 and 7 constituting a magnetic circuit are provided on both sides of the objective lens. Therefore, the size of the optical pickup increases in the lateral direction accordingly. In addition, since the coil 4 etc. are placed on both sides,
Optical members 9-
13 cannot be placed. Therefore, conventionally, the drive member such as the coil 4 and the optical members 9 to 13 must be arranged in two layers, one above the other, and the vertical dimension of the optical pickup has also increased.

In order to eliminate the above-mentioned drawbacks, only one set of coils 4 and 5, yoke 6, and magnet 7 for driving lens holding member 3 may be provided, and a one-sided driving system may be used. However, if the structure of FIG. 6 is simply removed from the coils 4 and 5 on one side, the distance between the point of application of the driving force (approximately the center of the yoke 6) and the objective lens 1 will be widened. Because of this, the load becomes unbalanced. Furthermore, the state of support by the leaf spring becomes unstable, making it impossible to perform a smooth correction operation.

The present invention solves the above-mentioned conventional problems, and allows the focusing coil and tracking coil to be arranged within the minimum dimensions, minimizing the width dimension, and using a single set of magnet and yoke. The object of the present invention is to provide an optical pickup that enables efficient driving of a focus servo and a tracking servo.

[Means for solving problems]

In the optical pick-up according to the present invention, the lens holding member that holds the objective lens facing the recording medium operates in the focus servo direction along the optical axis of the objective lens and in the tracking servo direction along the recording surface of the recording medium. A focus coil that drives the lens holding member in the focus servo direction and a tracking coil that drives the lens holding member in the tracking servo direction are fixed to the lens holding member. Furthermore, in the optical pickup provided with a magnetic circuit that crosses the focus coil and the tracking coil, the focus coil is wound into a rectangular tube shape and placed inside a hole formed in the lens holding member, In addition, both opposing outer surfaces of the focus coil are fixedly attached to both inner surfaces of the hole, and the tracking coil is tightly attached to the other outer surface of the focus coil, and the tracking coil is fixedly attached to the opposite outer surface of the focus coil. The bent portion is provided in close contact with the same surface as the inner surface of the hole to which the focus coil is in close contact,
The magnetic circuit is characterized in that one of the magnet and the yoke constituting the magnetic circuit is inserted into the focus coil, and the other is provided facing the outside of the tracking coil.

[Effect]

In the above means, a pair of a magnet and a yoke are provided with a focus coil and a tracking coil in between, and a driving force in the focusing direction and a driving force in the tracking direction are exerted by magnetic flux extending from the magnet to the yoke. be done. The focus coil is installed in a hole formed in the lens holding member, and both outer surfaces of the focus coil and the bent portion of the tracking coil are placed in close contact with the same inner surface of the hole in the lens holding member. Therefore, the width dimension in which the coil is arranged can be suppressed within the width dimension of the focus coil. Therefore, the width dimension of the lens holding member in which this coil is installed can be minimized.

[Example of the present invention]

Embodiments of the present invention will be described below with reference to the drawings of FIGS. 1 to 5.

Fig. 1 is a plan view of the optical pick-up, Fig. 2 is a side view thereof, Fig. 3 is an exploded perspective view of the optical pick-up, Fig. 4 is a plan view of the lens holding member, and Fig. 5 is a perspective view of the coil. It is.

Reference numeral 21 in the figure is a yoke. This yoke 2
1 is made of a magnetic material, and a pair of plate portions 21a and 21b are erected in parallel at the bottom tip thereof. A magnet 22 is fixed to the inner surface of one plate portion 21a, and the magnet 22 extends from the magnet 22 toward the opposite plate portion 21b.
A magnetic circuit is configured that flows from 1b to plate portion 21a.

Spring support portions 21c are protruded from both sides of the base end of the yoke 21, and focus springs 23 are fixed to the top and bottom of the spring support portions 21c. Two protrusions 21d are protruded from the upper and lower surfaces of the spring support portion 21c, and the focus spring 23 is positioned by fitting a small hole 23a formed in the focus spring 23 with the protrusions 21d. ing.
A total of four focus springs 23 are attached to the upper and lower surfaces of the yoke 21 on the downstream side.

An intermediate member 24 is supported at the tip of the focus spring 23. The intermediate member 24 can be slightly moved in the focus servo direction (Y direction) by deforming the focus spring 23. Intermediate member 2
4 is configured in a U-shape. Intermediate member 24
Focus spring fixing surfaces 24a are provided on the upper and lower surfaces of both sides of the
is formed, and this focus spring fixing surface 2
4a is provided with a pair of protrusions 24b. A small hole 23b bored at the tip of the focus spring 23 is fitted into the protrusion 24b, thereby positioning the focus spring 23 and the intermediate member 24.

Furthermore, tracking spring fixing surfaces 24c are provided at the lower ends of the inner surface of both sides of the intermediate member 24, and the pair of left and right tracking spring fixing surfaces 24c
A lower end of a tracking spring 25 is fixed to each of the springs 4c. Two square protrusions 24d are provided on each tracking spring fixing surface 24c, and a notch 2 formed at the lower end of the tracking spring 25
5a is fitted into this protrusion 24d to position the tracking spring 25.

A lens holding member 26 is supported at the upper end of the tracking spring 25. The lens holding member 26 has spring fixing surfaces 26a formed on both sides, and two protrusions 26b are provided on each of the spring fixing surfaces 26a. A small hole 25b is bored in the upper end of the tracking spring 25, and this small hole 25b
is fitted into the projection 26b to position the spring.

Further, as shown in detail in FIG. 4, the lens holding member 26 is integrally formed with a lens barrel 26c on the right side of the figure, and has a square hole 26d formed on the left side of the right side of the figure. An objective lens 27 is held within the lens barrel 26c. Further, a focus coil 28 and a tracking coil 29 are installed in the hole 26d. As shown in FIG. 5, the focus coil 28 is wound into a rectangular tube shape so that current flows in the X direction. This focus coil 28 is fixed in the hole 26d at the left end in the drawing, and the focus coil 28 and the objective lens 27 balance the load on the left and right sides of the lens holding member 26. . Note that if the objective lens 27 is heavier, a balancer may be attached to the left side surface 26e of the lens holding member 26 to balance the left and right sides.

Further, two tracking coils 29 are provided, each of which is wound to form a substantially square shape. In the tracking coil 29, the part indicated by the reference numeral 29a in FIG. 5 is a driving part.
In this drive section 29a, a current flows in the Y direction. Further, the side end portion 29b of the tracking coil 29 is bent in the opposite direction to the direction of the focus coil 28. In the lens holding member 26, the side end portion 29b is attached in close contact with the inner surface of the hole 26d. Since the side end portion 29b is bent in the opposite direction to the focus coil 28 in this manner, the side end portion 29b does not protrude from the side of the focus coil 28. Therefore, the inner dimension Wa (see FIG. 4) of the hole 26d is the same as that of the focus coil 28.
The width of the lens holding member 26 can be reduced by the amount that the side end portion 29b does not protrude outside the dimension Wa.

When the entire optical pickup is assembled, the focus coil 28 surrounds the plate portion 21a of the yoke 21 and the magnet 22, as shown in FIGS. 1 and 2. In addition, the other plate portion 21b
is placed between the tracking coil 29 and the objective lens 27. Then, the magnet 22 and the plate portion 21b
focus coil 2 within the magnetic field formed between
8 and the driving portion 29a of the tracking coil 29 are interposed.

Further, as shown in FIG. 2, a prism 31 is provided directly below the objective lens 27. This prism 31 is arranged inside the yoke 21.
Therefore, the optical member 14 that receives and receives the laser beam is disposed at a position parallel to the yoke 21. The laser beam passes through a notch 21e formed in the yoke 21, is reflected by a prism 31, and is sent to an objective lens 27.

In the above optical pickup, magnet 2
2 and the plate portion 21b of the yoke 21 and the current flowing through each coil 28 and 29, an electromagnetic force is generated, and the lens holding member 26 is corrected and driven in the X direction and the Y direction. That will happen. Therefore, the point of application of the force that drives the lens holding member 26 is approximately at the midpoint between the magnet 22 and the plate portion 21b of the yoke 21 (the position indicated by A in FIGS. 1 and 4). In the lens holding member 26, an objective lens 27 and a focus coil 28 are arranged on the left and right sides of the point A, so that the load on both sides of the point A can be balanced. Also, as mentioned above, A
A balancer can also be provided on the left side surface 26e of the lens holding member 26 so that the left and right loads are accurately balanced with respect to the point and the point A coincides with the center of gravity.

Further, the above-described driving center point A is located at the midpoint of the width Wb of the tracking spring 25. On the other hand, the focus spring 23 is bonded to the focus spring fixing surface 24a of the intermediate member 24, and the point at which the intermediate member 24 is supported by the focus spring 23 is a point on the step at the end of the fixing surface 24a (reference numeral point B). This point B is also the driving force application point A of the lens holding member 26.
is in the same position as That is, the driving force application point A of the lens holding member 26 and the focus spring 2
The support point B by the tracking spring 25 and the support point by the tracking spring 25 (the midpoint of the spring width Wb) are set to be located on the same line.

Next, the operation of the optical pickup having the above configuration will be explained.

The optical disk is rotationally driven by a turntable (not shown). In accordance with this, the optical pickup moves away from the position close to the turntable 11, and a reproduction operation is performed.

A laser beam emitted from a laser diode 9 (see FIG. 6) within the optical member 14 is split into three beams by a diffraction grating. Further, the beam passes through a beam splitter 10, is made into a parallel beam by a collimating lens 11, passes through a quarter-wave plate 12, and is sent to an objective lens 27 by a prism 31. The light is focused on the recording surface of the optical disk by the objective lens 27, and three beam spots are formed on the recording surface. The reflected beam from the recording surface passes through the objective lens 27, prism 31, etc., and returns to the beam splitter 10, where it is reflected in a 90-degree direction, passes through the concave lens and the cylindrical lens 15, and is sent to the photodiode. Detected at 13. By intensity modulating the detection output of the photodiode 13, information bits on the recording surface of the optical disk are read.

During this reproduction operation, the lens holding member 26 is slightly driven to perform a correction operation.

A correction operation for focusing the beam spot formed on the recording surface of the optical disk is performed by controlling the current flowing through the focus coil 28. The lens holding member 26 is driven in the Y direction together with the objective lens 27 by the current flowing in the focus coil 28 in the X direction and the magnetic field generated by the magnet 22 and crossing the focus coil 28. This movement is permitted by the deformation of the focus spring 23. As a result, the objective lens 27
The focus of the laser beam emitted from the optical disk is always set on the recording surface of the optical disk.

Further, the correction operation for causing the laser beam irradiated onto the recording surface of the optical disk to follow the information track is performed by controlling the current flowing through the tracking coil 29. A current flowing in the Y direction in the drive section 29a of the tracking coil 29;
The lens holding member 26 is slightly driven in the X direction by the magnetic field formed by the magnet 22. This movement of the lens holding member 26 is permitted by the deformation of the tracking spring 25.

Since the lens holding member 26 is configured to balance the left and right loads with point A as the border,
The lens holding member 26 does not tilt due to inertial force during the correction operation. Accurate corrective action is performed. Also, the support point B by the focus spring 23
Since the support point by the tracking spring 25 (midpoint of Wb) coincides with the driving force application point A,
The support balance by the spring is good, and the correction operation of the lens holding member 26 is also smooth.

[Effects of this invention]

As described above, according to the present invention, the focus coil has a rectangular tube shape and is provided in the hole of the lens holding member, and the two opposing outer surfaces of the focus coil and the bent portion of the tracking coil hold the lens. Since the coils are in close contact with the same inner surface of the hole in the member, the arrangement dimensions of the coils can be kept within the width dimension of the focus coil. Furthermore, a magnet and a yoke constituting a magnetic circuit are also arranged within the hole of the lens holding member. Therefore, the overall width of the lens holding member in which the focus coil and tracking coil are housed is just the width of the focus coil plus the minimum thickness. Since the magnet and yoke do not protrude, a pick-up with the minimum width can be constructed. Furthermore, since a magnetic field that crosses the focus coil and the tracking coil can be formed by one set of magnet and yoke, driving efficiency is improved.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a plan view of an optical pickup, FIG. 2 is a side view thereof, and FIG. 3 is an exploded perspective view of the optical pickup. Figure 4 is a plan view of the lens holding member, Figure 5 is a perspective view of the coil, Figure 6 is a front view schematically showing the structure of a conventional optical pickup, and Figure 7 is a right side view of Figure 6. be. 21...Yoke, 21a, 21b...Plate part, 2
2... Magnet, 23... Focus spring, 2
4... Intermediate member, 25... Tracking spring, 2
6... Lens holding member, 27... Objective lens, 2
8...Focusing coil, 29...Tracking coil.

Claims (1)

[Scope of utility model registration request] A lens holding member holding an objective lens facing the recording medium is supported so as to be able to move slightly in a focus servo direction along the optical axis of the objective lens and in a tracking servo direction along the recording surface of the recording medium. , and a focus coil that drives the lens holding member in the focus servo direction and a tracking coil that drives the lens holding member in the tracking servo direction are fixedly installed on the lens holding member, and further, the focus coil and the tracking coil are fixed to the lens holding member. In an optical pickup in which a magnetic circuit is provided across the coil, the focus coil is wound into a rectangular tube shape and placed inside a hole formed in the lens holding member. The outer surface of the tracking coil is fixedly attached to both inner surfaces of the hole, and the tracking coil is in close contact with the other outer surface of the focus coil, and the portion bent on the opposite side of the focus coil is fixed to the inner surface of the hole. The hole is provided in close contact with the same inner surface as the focus coil, and one of the magnet and yoke forming the magnetic circuit is inserted into the focus coil, and the other is inserted into the outer side of the tracking coil. An optical pick-up characterized by being provided facing the.