JP2002245644A - Actuator device for optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent sensitivity from decreasing owing to insufficient winding factors of the focus coil and tracking coil of a moving magnet type actuator. SOLUTION: In the actuator device for an optical pickup, which is equipped with a holder holding an objective arranged opposite an information recording medium, a magnet fixed to the holder, a support mechanism supporting the holder movably, and a couple of coil assemblies 67A and 67B arranged at the both sides of the magnet to drive the magnet, the coil assemblies are arranged having the focus coil and tracking coil stacked, and a magnetic circuit for focusing is composed of the outside coil of one coil assembly and the inside coil of the other coil assembly in combination and a magnetic circuit for tracking is composed of the inside coil of one coil assembly and the outside coil of the other coil assembly in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving magnet type objective lens actuator in an optical apparatus for recording an information signal on an optical disk or the like as an optical information recording medium and reproducing the recorded information signal.

[0002]

2. Description of the Related Art A conventional optical disk actuator structure will be described with reference to FIG. The pickup 100 includes a pickup housing 110, a light emitting element light receiving element integrated laser 120 (hereinafter, referred to as an integrated laser), an integrated laser drive circuit 130, a collimator lens 140,
It comprises a mirror 150 and an actuator assembly 160. The objective lens 161 is attached and fixed to the actuator assembly 160.

A pickup 100 is provided with a central lens of an objective lens for reading high-density information from a read-only disk formed by irregularities or the like or a recording / reproducing disk capable of reversibly forming a signal due to a difference in reflectance of a material. Are attached in a posture substantially orthogonal to the signal forming surface 210 of the medium 200.

Further, the pickup 100 moves substantially in parallel from the inner circumference to the outer circumference of the medium 200 or from the outer circumference to the inner circumference while maintaining the above-mentioned posture, so that the signal on the medium 200 Must be read in a high-quality state, or a high-quality signal must be written on the medium 200. Therefore, two guide shafts 300 are formed substantially parallel to the signal forming surface 210 of the medium 200, and the guide housing 111 is formed with a guide hole 111 and a guide groove 112 for parallel movement based on the guide shafts. I have.

Next, the operation of the pickup will be described. Laser light 170 emitted from integrated laser 120
Is a divergent light having a radiation angle, and in this divergent light, a collimator lens 140 is arranged, and a light emitting point of the integrated laser 120 is placed at a focal position of the collimator lens 140, so that the collimator lens The emitted laser light 170 becomes substantially parallel light. When a parallel flat plate or the like exists between the laser emission point of the integrated laser 120 and the principal point of the collimator lens 140, the integrated laser 12 is located at a position where the thickness of the transmission part is corrected.
Needless to say, it is necessary to set a zero laser emission point.

[0006] The focal length of the collimator lens 140 takes various values depending on whether the pickup is for reproduction only or for recording and reproduction.
In general, by setting the focal length of the objective lens 161 to be described later to be a large value of 5 to 8 times, the required mounting accuracy of the integrated laser 120 and the collimator lens 140 to the pickup housing 110 can be reduced. .

[0007] In the case of recording and reproduction, the emission intensity inherent in the integrated laser and the writing speed to the medium 200 largely depend on the emission intensity. There is.

The optical path of the parallel light 171 emitted from the collimator lens 140 is changed by the rising mirror 150 so as to be substantially orthogonal to the signal forming surface 210 of the medium 200. The parallel light 171 is transmitted to the objective lens 1 fixed to the actuator
It is incident on 61.

The numerical aperture (hereinafter N) of the objective lens 161
A) is a value that is optimal for the target medium, so that at a distance from the medium 200 by a predetermined distance,
By positioning the objective lens 161, a signal on the medium 200 can be read in a high quality state,
A high-quality signal can be written on the medium 200.

As an example, a reproduction operation of a reproduction-only medium in which a signal is composed of fine irregularities will be described. On the signal forming surface 210 of the medium 200, the objective lens 161 and the laser light 172 narrowed down by the transparent protective layer 220 of the medium 200 are reflected on the signal surface, and the reflected light travels along the same optical path as the going light. Returning to the opposite direction, the light is guided onto the light receiving element of the integrated laser 120 by a spectroscopic means (not shown) provided in the integrated laser 120.

Since the reflected light is modulated by the irregularities on the medium 120, a signal formed on the medium 120 can be reproduced.

When the above reading and writing are performed, the medium 200 is rotating at a predetermined rotation speed. However, generally, the medium 200 is rotated by a mechanical accuracy of a media rotating means (not shown) and a physical accuracy of the medium 200. When the objective lens 161 facing the signal surface of the medium 200 is fixed, continuous information cannot be read or written in a high-quality state. To cope with this, the actuator assembly 160 has a function of causing the objective lens 161 to follow the surface runout and the center runout of the medium 200. Generally, the operation of following the objective lens to the surface shake is referred to as a focus operation, and the operation of following the objective lens to the medium runout is referred to as a tracking operation.

Before describing the following method, the structure of the actuator assembly 160 will be described with reference to FIGS. The actuator assembly 160 includes the objective lens 1
61, lens holder 182, magnet 163, wire 164, wire holder 185, actuator base 1
66, coil assembly 167, relay board 188, fixing screw 1
Consists of 69.

The objective lens 16 is mounted on the lens holder 182.
1. The magnet 163 is attached and fixed. The lens holder 162 is supported by four wires 164 and held in a space in a cantilever state. on the other hand,
The wire holder 165 is attached and fixed to the actuator base 168 by a fixing screw 169, and the wire 16 is attached to the wire holder 165.
The four supporting ends are attached and fixed.

As shown in FIG. 8, the wire holder 165
The damping material 165b for reducing the resonance magnification (Q) of the secondary vibration system composed of the lens holder assembly 162 and the four wires 164 is provided in the concave portion 165a near the wire mounting portion.
Is filled. A pair of coil assemblies 167 is attached to the actuator base 1 so that the magnet 183 attached to the lens holder 162 is sandwiched while being separated.
66 and fixed.

As shown in FIG. 9, the coil assembly 167 includes a yoke plate 167a having a high magnetic permeability, a pair of yoke holders 167b, and two windings 167c. Winding 16
7c includes a winding 167ct (hereinafter referred to as a tracking coil) wound directly on the yoke plate, and a winding 167cf (hereinafter referred to as the focus coil) wound around the yoke holder so as to cover the winding. A coil terminal of the coil assembly 167 is soldered to a predetermined position of a relay board 168 attached and fixed to the back surface of the actuator base 166.

Next, the focusing operation and the tracking operation of the actuator assembly 180 will be described. The light receiving element of the integrated laser 120 shown in FIG. 5 has a function of generating an error signal according to the residual tracking error of the focus operation and the tracking operation, and based on this signal,
A drive signal for performing a focus operation and a tracking operation of the objective lens is supplied to the coil assembly 167 via a relay board 168 shown in FIG.

As a method of detecting the residual tracking error of the focus operation, there is a knife edge method. In the knife edge method, a return light is kicked by a shielding plate inserted on an optical path, and a pattern of reflected light returning on the light receiving element,
This is a method of calculating the residual follow-up amount by utilizing the fact that it changes according to the distance between the objective lens 161 and the medium 200.
When a so-called hologram laser is used as the integrated laser 120, a knife edge method is often used.

On the other hand, as a method for detecting a residual tracking error in the tracking operation, there are a DPD method (phase detection method), a three-beam method, and the like. The DPD method is a method of determining the residual following error by setting the step of the unevenness formed on the medium 200 to d and the laser wavelength to be human, d ≒ person / 4. According to the above setting, there is an advantage that modulation by unevenness can be obtained and a signal on a medium can be reproduced at a high S / N ratio.

At this time, the pattern of the reflected light returning to the light receiving element becomes a rotationally symmetrical elliptical shape at each point on the virtual center when the virtual center is considered by connecting the centers of the continuous unevenness information. The change in the major axis tilt polarity of the ellipse is reversed depending on whether the trajectory by which the laser beam scans the medium relatively shifts inside or outside the virtual center formed by the unevenness. Utilizing this fact, the residual tracking error of the tracking operation is detected.

The thrust generated by the coil assembly 167 changes according to the level of the drive signal. This thrust is
Magnet 163 attached to lens holder 162
, And follows the surface runout and the center runout of the medium 200. The above operation constitutes a closed loop servo system, and the tracking following operation is performed by tracking servo,
The focus following operation is called a focus servo.

FIG. 10 shows the tracking servo operation.
Will be described based on the tracking magnetic circuit. The magnet 163 is magnetized in two poles in the thickness direction, and a pair of coil assemblies 187 are installed so as to sandwich the magnet 163 while being separated as described above.

Now, when a drive current is applied to the tracking coil 187ct as shown in the figure, a magnetic field 167ctj of an arrow is generated (a direction in which a double circle comes out of the plane of the paper perpendicularly, and a cross shows a direction in which it goes perpendicular to the plane of paper). The thrust of the magnet 163 in the arrow direction 163t changes according to the strength. By reversing the direction of the drive current, the magnetic field generated by the coil is reversed, and the thrust on the magnet also acts in the direction opposite to the arrow.

The focus servo operation is as shown in the focus magnetic circuit of FIG. 11, and the operation is the same as described above.

[0025]

The actuating system configured as described above is called a moving magnet type actuator in the sense that the coil side is fixed and the magnet moves, but the fixed coil assembly is used. In general, the sensitivity of either the focus or the tracking is reduced due to the restriction resulting from the configuration described above.

As described above, since the winding wound directly on the yoke plate is wrapped by the outer winding,
For example, in the case of using a wire having the same wire diameter and the same material, the tracking coil on the inner side does not increase the linear area factor as expected due to dimensional restrictions, and the sensitivity is reduced.

To correct this, there are means such as thinning the wire of the inner tracking coil, replacing it with a material having a high conductivity, or increasing the wire area ratio and conductivity by making the cross-section square. .

However, all of these measures lead to an increase in the cost of the actuator assembly, and there is a problem that it is difficult to adopt it as a total judgment.

There is also a means for increasing the linear area ratio by increasing the volume of the inner coil occupying the inside of the actuator assembly. However, the expansion of the actuator assembly necessitates an increase in the size of the entire pickup. This leads to an increase in the size of the entire apparatus.

An object of the present invention is to prevent a decrease in sensitivity due to a shortage of the linearity of a focus coil and a tracking coil in a moving magnet type actuator.

[0031]

To solve the above-mentioned problems, the present invention employs the following configuration. A holder for holding an objective lens opposed to the information recording medium, a magnet fixedly mounted on the holder, a support mechanism for movably supporting the holder, and a magnet arranged on both sides of the magnet to hold the magnet; A pair of coil assemblies to be driven, comprising: a pair of coil assemblies, each of which includes a focus coil and a tracking coil arranged in layers, and A magnetic circuit for focusing is formed by a combination of an outer coil of one of the coil assemblies and an inner coil of the other coil assembly, and one of the coil assemblies of the pair of coil assemblies is formed. Actuator for an optical pickup that forms a tracking magnetic circuit by combining an inner coil and an outer coil of the other coil assembly The other apparatus.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A configuration example of an actuator device according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an example of the configuration of an actuator device according to an embodiment of the present invention. Two types of coil assembly 67A to make
And a coil assembly 67B, a relay board 68, a fixing screw 69,
It is composed of

As shown in FIG. 2, the coil assembly 67A includes a yoke plate 67Aa having high magnetic permeability, a pair of yoke holders 67Ab, an inner tracking coil 67Act wound directly around the yoke, and the tracking coil 67Act. It is composed of an outer focus coil 67Acf wound so as to cover it.

The coil assembly 67B is wound around the yoke plate 67Ba having a high magnetic permeability, a pair of yoke holders 67Bb, an inner focus coil 67Bcf wound directly around the yoke, and the focus coil 67Bcf. Tracking coil 6 outside
7Bct.

Next, the driving principle of the objective lens holder will be described. First, in the case of the tracking direction, as shown in FIG. 3, the tracking coil 67Act wound around the inside of the coil assembly 67A and the tracking coil 673ct wound around the outside of the coil assembly 67B form a pair.
The winding directions are parallel to each other, and when each is energized, a magnetic circuit 67ctj is formed. By the action of the magnetic circuit, a thrust 63t is generated in the magnet 63, and the objective lens holder moves in the tracking direction.

Similarly, in the case of the focus direction, as shown in FIG. 4, the focus coil 67Acf wound around the outside of the coil assembly 67A and the focus coil 67Bcf wound around the inside of the coil assembly 67B form a pair. The winding direction is parallel, and the magnetic circuit 67c
fj. The thrust 63f is generated in the magnet 63 by the action of the magnetic circuit, and the objective lens holder moves in the focus direction.

As described above, one is provided by the inner coil wound directly on the yoke having high magnetic permeability, and the other is provided by the outer coil wound so as to cover the inner coil.
By forming a pair of focus coils or tracking coils so as to form a pair, extreme sensitivity loss due to a decrease in the line rate, which is a problem with the pair of focus coils or tracking coils, due to both inner coils, is large. And the sensitivity balance in the focus direction and the tracking direction is improved.

[0038]

According to the constitution of the present invention, in the conventional moving magnet type actuator, extreme sensitivity due to shortage of line rate, which is a problem with a pair of focus coils or tracking coils, both of which are formed of inner coils. The reduction can be improved without increasing the cost and the size, and the sensitivity balance between the focus direction and the tracking direction is improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of an actuator device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed structure of a coil assembly A and a coil assembly B of the present embodiment.

FIG. 3 is a diagram showing a tracking magnetic circuit when a coil assembly A and a coil assembly B of the present embodiment are used.

FIG. 4 is a diagram illustrating a focus magnetic circuit when a coil assembly A and a coil assembly B of the present embodiment are used.

FIG. 5 is a diagram showing a structure of an optical pickup using a conventional actuator.

FIG. 6 is a diagram showing a structure of a conventional actuator.

FIG. 7 is an exploded view of a conventional actuator.

FIG. 8 is a detailed view of a wire holder.

FIG. 9 is a detailed view of a conventional coil assembly.

FIG. 10 is a diagram showing a tracking magnetic circuit when a conventional coil assembly is used.

FIG. 11 is a diagram showing a focus magnetic circuit when a conventional coil assembly is used.

[Explanation of symbols]

 60 Actuator assembly 61 Objective lens 62 Objective lens holder 63 Magnet 63f Focusing direction thrust 63t Tracking direction thrust 64 Wire 65 Wire holder 66 Actuator base 67A Coil assembly A 67Aa Yoke 67Ab Yoke holder 87Acf Focus coil 67Act Tracking coil 67cft Tracking magnetic field Magnetic field 67B Coil assembly B 67Ba Yoke 67Bb Yoke holder 67Bcf Focus coil 67Bct Tracking coil 68 Relay board 69 Fixing screw 100 Pickup 110 Pickup housing 111 Guide hole 112 Guide groove 120 Light emitting element light receiving element integrated laser 130 Laser drive circuit 140 Collimator lens 150 mirror 60 Actuator assembly 161 Objective lens 162 Objective lens holder 183 Magnet 163f Focusing direction thrust 163t Tracking direction thrust 164 Wire 165 Wire holder 165a Wire mounting recess 165b Damping material 186 Actuator base 167 Coil assembly 167a Yoke 167c Coke yoke 167c Coke holder Tracking coil 167cfj Focusing magnetic field 167ctj Tracking magnetic field 168 Relay board 169 Fixed screw 170,171,172 Laser light 200 Recording / reproducing disk 210 Signal forming surface 220 Cover layer 300 Guide

Claims (1)

[Claims] 1. A holder for holding an objective lens opposed to an information recording medium, a magnet fixed to the holder, a support mechanism for movably supporting the holder, and arranged on both sides of the magnet. And a pair of coil assemblies for driving the magnet, wherein each of the pair of coil assemblies is provided with a focus coil and a tracking coil stacked one on another, A magnetic circuit for focusing is formed by a combination of an outer coil of one of the pair of coil assemblies and an inner coil of the other of the pair of coil assemblies, and one of the pair of coil assemblies. A tracking magnetic circuit is formed by a combination of an inner coil of the coil assembly and an outer coil of the other coil assembly. Actuator device of the optical pick-up that.