JPH05182216A - Objecting lens driving device - Google Patents

Abstract

PURPOSE:To prevent the occurance of unwanted resonance and to improve control performance by detecting the change of the magnetic field distribution made by a permanent magnet piece in accordance with the displacement of the permanent magnet held by a lens holder by a Hall element. CONSTITUTION:When a distance between a disk 13 and an objective lens 1 is changed, a current according to a focus deviation quantity flows through a focus controlling coil 6 and a lens holder 3 is displaced to a focus direction (Z direction), and thereby, a permanent magnet 21, as well is displaced in the same direction. Then the magnetic field distribution, as well of the position of a Hall element 23 is changed. According to the change, the voltage, as well generated in the Hall elements 23a-23d is changed, and the output of an operator 24c is changed according to the displacement of a Z direction. Thus, the position of the lens holder 3, the objective lens 1, as well in the focus direction (Z direction) is obtained by the signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device, and more particularly to a reproducing device or an objective of a recording / reproducing device for controlling track deviation and focus deviation of a light spot focused on an information recording surface of an optical disk. The present invention relates to a lens driving device.

[0002]

2. Description of the Related Art FIG. 11 is a perspective view showing a main part of a conventional objective lens driving device, in which 1 is an objective lens,
Reference numeral 2 is a counter weight, 3 is a lens holder having a cylindrical bearing 3a, and 4 is a bearing 3a of the lens holder 3 which is slidable in the focal direction (Z direction) and rotational direction (X direction).
5a, 5b are support rubbers for holding the lens holder 3, 6 is a focus control coil, 7
a and 7b are track control coils, 8 is a fixed base, and 9 is a fixed base.
Is a permanent magnet for focus control, 10 is a yoke, 11a, 11b
Is a permanent magnet for track control, and 12a and 12b are back yokes. The track control permanent magnets 11a and 11b are formed by magnetizing left and right two poles.

The lens holder 3 having the objective lens 1 and the counter weight 2 mounted thereon is supported by the support rubbers 5a and 5b to be X-shaped.
It is supported at a midpoint of the movable range in the axial direction and the Z-axis direction and is held by a fixed base 8. Further, the lens holder 3 is provided with a cylindrical bearing 3a, the focus control coil 6 is attached to the cylindrical portion concentric with the cylindrical bearing 3a, and the track control coils 7a and 7b are attached to the left and right side surfaces. .. The focus control coil 6 is arranged in the magnetic path formed by the focus control permanent magnet 9 and the yoke 10 provided on the fixed side, and the track control coils 7a and 7b are provided.
Is a track control permanent magnet 11a provided on the fixed side,
11b and the back yokes 12a and 12b are arranged in the magnetic path.

Next, the operation will be described. By passing a desired current through the focus control coil 6, the lens holder 3
Slides in the Z-axis direction to adjust the focal length of the objective lens 1. By passing a desired current through the track control coils 7a and 7b, the lens holder 3 rotates in the X-axis direction, and the objective lens 1 rotates to perform track control.

[0005]

Since the conventional device is constructed as described above, it is necessary to fix the supporting rubbers 5a and 5b to the lens holder 3 and then to fix them to the fixed base 8, so that the work can be performed easily. There was a problem that it was complicated. Further, if the support rubbers 5a and 5b are not attached and fixed correctly, when the lens holder 3 is driven in the X-axis direction or the Z-axis direction, it does not move accurately in that direction, and the objective lens 1 tilts. There was a point. Furthermore, support rubber 5
There is also a problem that a and 5b resonate at their natural frequencies, which adversely affects the frequency characteristics of the actuator as shown by the circle in FIG. 12 and deteriorates the control performance.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an objective lens driving device having a simple structure and a highly reliable lens holder supporting means.

[0007]

An objective lens driving device according to the present invention includes a permanent magnet piece held by a lens holder, which is a movable portion, and a fixed base provided so as to face the permanent magnet piece. This is provided with a number of Hall elements and an arithmetic unit that performs an arithmetic operation based on the outputs of the four Hall elements.

Further, the objective lens driving device according to the present invention includes four Hall elements held by the lens holder which is a movable portion, and a permanent magnet piece provided on the fixed base so as to face the Hall elements. It is provided with an arithmetic unit that performs arithmetic operations based on the outputs of four Hall elements.

Further, a metal counterweight held by a lens holder which is a movable portion, an electrostatic capacitance detector provided on a fixed base so as to face the counterweight, and an output of the electrostatic capacitance detector. It is provided with an arithmetic unit for performing an arithmetic operation based on.

Further, a metal counterweight held by a lens holder which is a movable portion, an eddy current displacement detector provided on a fixed base so as to face the counterweight, and an output of the eddy current displacement detector. It is provided with an arithmetic unit for performing an arithmetic operation based on.

[Action]

According to the present invention, the permanent magnet piece held by the lens holder is displaced along with the movement of the objective lens in the focal direction and the track direction, and the magnetic field distribution created by the permanent magnet piece is changed in accordance with this displacement. , It is detected by the Hall element provided on the fixed base. The output is calculated using a calculation device to obtain information on the position of the objective lens, and the midpoint of the objective lens is determined.

Further, the Hall element held by the lens holder is displaced along with the movement of the objective lens in the focal direction and the track direction, and the change in the magnetic field strength produced by the permanent magnet piece provided on the fixed side is detected. The output is calculated using a calculation device to obtain information on the position of the objective lens, and the midpoint of the objective lens is determined.

Further, the metal counterweight held by the lens holder is displaced along with the movement of the objective lens in the focal direction and the track direction, and the distance between the counterweight and the capacitance detector is also changed. Since the output of the electrostatic capacitance detector changes according to the distance from the counter weight, the output is calculated by using a calculation device and the information of the position of the objective lens is obtained to determine the midpoint of the objective lens. ..

Further, the metal counterweight held by the lens holder is displaced along with the movement of the objective lens in the focal direction and the track direction, and the distance between the counterweight and the eddy current displacement detector is also changed. Since the output of the eddy current displacement detector changes according to the distance from the counter weight, the output is calculated by using a calculation device and the information of the position of the objective lens is obtained to determine the midpoint of the objective lens. ..

[0015]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a main part of an objective lens driving device according to an embodiment of the present invention. In the figure, the same or corresponding parts as in FIG. 11 are designated by the same reference numerals.

Reference numeral 13 is an optical information recording medium (hereinafter referred to as a disk), and 21 is a permanent magnet piece held by the lens holder 3, which is magnetized in the longitudinal direction of the lens holder 3 by NS. Reference numeral 22 denotes a base held by the fixed base 8 and holds four Hall elements 23a to 23d. 24, 25
Is a computing unit that computes the signals obtained from the four Hall elements.

Next, the operation will be described. By the permanent magnet piece 21 held by the lens holder 3, the (X
The state of the magnetic field distribution in the Y direction formed on the (Z) plane is shown in FIG. The Hall element 23 is made of a material such as germanium or silicon, and has a property of generating an electromotive voltage at a right angle to the magnetic field and the current when the current is applied to the Hall element 23 in a magnetic field at right angles to the magnetic field. Further, this electromotive voltage is proportional to the strength of the magnetic field. Since the Hall elements 23a to 23d are arranged in the magnetic field distribution as shown in FIG. 2, an electromotive voltage corresponding to the strength of the magnetic field at each position is generated. The calculator 24a calculates and amplifies the sum of electromotive voltages generated in the hall elements 23a and 23b, the calculator 24b calculates and amplifies the sum of electromotive voltages generated in the hall elements 23c and 23d, and the calculator 24c calculates the sum of the electromotive forces of the calculators 24a and 24b. Calculate the output difference.

In the initial state, when the lens holder 3 is at the midpoint position in the Z direction, the position of the device base 22 is adjusted so that the output of the calculator 24c becomes zero. When the distance between the disk 13 and the objective lens 1 changes, a current corresponding to the amount of defocus flows into the focus control coil 6 and the lens holder 3 is displaced in the focal direction (Z direction), whereby the permanent magnet piece 21.
Is also displaced in the same direction, the magnetic field distribution at the position of the Hall element 23 also changes. Accordingly, the hall elements 23a-23
The electromotive voltage generated at d also changes, and the output of the calculator 24c changes as shown in FIG. 3 according to the displacement in the Z direction.

Therefore, the position of the lens holder 3 and thus the objective lens 1 in the focal direction (Z direction) can be obtained from this signal. The calculator 25a calculates the sum of electromotive voltages generated in the Hall elements 23a and 23c, and the calculator 25b calculates the sum of electromotive voltages generated in the Hall elements 23b and 23d.
After amplification, the calculator 25c calculates the difference between the outputs of the calculators 25a and 25b. Similarly to the focus direction, when the objective lens 1 is controlled by causing the lens holder 3 to rotate around the support shaft 4 by causing a current corresponding to the track shift amount to flow through the track control coils 7a and 7b, the calculator 25c operates as follows. The relationship between the output and the displacement in the X direction is as shown in FIG.

Therefore, the position of the lens holder 3 and thus the objective lens 1 in the track direction (X direction) can be obtained from this signal. The midpoint position of the objective lens 1 can be determined from the position information in the focus direction and the track direction, and the position is electrically supported by applying a current to the focus control coil 6 and the track control coils 7a and 7b. can do.

In the first embodiment, if the weight of the permanent magnet piece 21 and the mounting position are taken into consideration and the counterweight 2 is used as a substitute, the number of parts can be reduced.

Example 2. Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a perspective view of an essential part of an objective lens driving device according to another embodiment of the present invention. In the figure, parts that are the same as or correspond to those in FIGS. 1 and 11 are assigned the same reference numerals.

Reference numeral 31 is a base held by the lens holder 3 and holds four Hall elements 32a to 32d. 33
Is a permanent magnet piece held by a fixed base and is magnetized in the Y-axis direction.

Next, the operation will be described. In this configuration, in Embodiment 1, the permanent magnet piece is provided on the fixed side and the Hall element is provided on the lens holder that is the movable portion, and the relative positional relationship between the two is the same. The magnetic field distribution generated by the permanent magnet piece 21 does not change regardless of the movement of the lens holder 3. When the Hall element 32 is displaced along with the displacement of the lens holder 3, the strength of the magnetic field at that position changes, and the generated electromotive force changes. Although details are omitted, the position information can be obtained in both the focus direction and the track direction by using the same arithmetic unit and arithmetic method as in the first embodiment. The midpoint position is determined based on this, and the position can be electrically supported by passing a current through the focus control coil 6 and the track control coils 7a and 7b.

Example 3. Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a perspective view of an essential part of an objective lens driving device according to another embodiment of the present invention. In the figure, the same or corresponding parts as in FIG. 11 are designated by the same reference numerals.

Reference numeral 41 denotes a metal counterweight, which is fixed so as to project to the surface of the lens holder 3 opposite to the disk. 42a is a capacitance detector provided on the fixed base so as to face the protruding lower end of the counterweight 41, and 42b is provided on the fixed base so as to face the protruding side surface of the counterweight 41 in the track direction. It is a capacitance detector. 43a, 43b
Is a calculator for amplifying and calculating the outputs of the capacitance detectors 42a and 42b, respectively.

Next, the operation will be described. When the lens holder 3 is controlled to be displaced in the focus direction by causing a current corresponding to the amount of defocus to flow through the focus control coil 6, the counterweight 41 is also displaced at the same time, and the capacitance detector 42 is also displaced.
The distance to a changes. The capacitance detector 42 utilizes the fact that the capacitance between the metal counterweight 41 and the counterweight 41 changes according to the distance between the two, and replaces the capacitance change with a voltage change. The relationship between displacement and capacitance is inversely proportional to the distance between the two, as shown in FIG. Therefore, by performing the correction as shown in FIG. 8 in the arithmetic unit 43a, the signal as shown in FIG. 9 is obtained, and the position information of the lens holder 3 and thus the objective lens 1 in the focal direction (Z direction) is obtained. be able to. Similarly to this, the position in the track direction can also be obtained by the capacitance detector 42b and the calculator 43b. Based on that, determine the midpoint position of the objective lens 1,
Focus control coil 6 and track control coils 7a, 7
The position can be electrically supported by passing a current through b.

Example 4. Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a perspective view of an essential part of an objective lens driving device according to another embodiment of the present invention. In the figure,
The same or corresponding parts as those in FIGS. 11 and 6 are designated by the same reference numerals.

46a is a metallic counterweight 41
Of the eddy current displacement detector provided on the fixed base so as to face the protruding lower end of the fixed base, and 42b denotes an eddy current displacement detection provided on the fixed base so as to face the side surface of the protruding counterweight 41 in the track direction. It is a vessel.

Next, the operation will be described. When the lens holder 3 is controlled and displaced in the focus direction by causing a current according to the amount of defocus to flow through the focus control coil 6, the counterweight 41 is also displaced, and the eddy current displacement detector 4
The distance to 6a changes. The eddy current displacement detector 46 has two coils wound close to each other, one of which is the primary side,
When the other side is the secondary side and a current of several MHz is passed through the primary coil, a voltage proportional to the current and the mutual inductance between the two coils is induced in the secondary coil. At this time, if there is a metal surface such as the counterweight 41 near the secondary coil, an eddy current is generated on the metal surface, the apparent mutual inductance changes, and the voltage corresponding to the displacement of the counterweight 41 becomes 2%. It occurs in the next coil. By calculating with the calculator 47 based on this voltage, the lens holder 3,
As a result, position information of the objective lens 1 in the focal direction (Z direction) and the track direction (X direction) can be obtained. Based on this, the midpoint position of the objective lens 1 is determined, and the position can be electrically supported by passing a current through the focus control coil 6 and the track control coils 7a and 7b.

In the third and fourth embodiments, even if the electrostatic capacitance detector or the eddy current displacement detector is held by the lens holder 3 and the metal rod-shaped piece is provided on the fixed side, the same performance is obtained. You can do it.

In the above embodiment, the position and the track direction of the objective lens are detected and the objective lens is electrically supported based on the position information. It may be used for damping to suppress the resonance of the actuator. Further, it goes without saying that it may be used for offset correction means that occurs optically.

[0033]

As described above, according to the present invention, since the position of the objective lens is detected and the objective lens is electrically supported based on this position information, it is necessary to use a supporting rubber. In addition, the assembling work is simplified, and the tilt of the objective lens and the occurrence of unnecessary resonance due to the supporting rubber can be eliminated.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is a magnetic field distribution diagram generated from the permanent magnet pieces according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the position in the focal direction of the objective lens and the signal output from the computing unit according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the position of the objective lens in the track direction and the signal output from the computing unit according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a main part of an objective lens driving device according to another embodiment of the present invention.

FIG. 6 is a perspective view showing a main part of an objective lens driving device according to another embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a position of an objective lens in a focal direction and a signal output from a capacitance detector according to a third embodiment of the present invention.

FIG. 8 is a diagram showing characteristics of a correction circuit of an arithmetic unit according to a third embodiment of the present invention.

FIG. 9 is a diagram showing the relationship between the position of the objective lens in the focal direction and the signal output from the computing unit according to the third embodiment of the present invention.

FIG. 10 is a perspective view showing a main part of an objective lens driving device according to another embodiment of the present invention.

FIG. 11 is a perspective view showing a main part of a conventional objective lens driving device.

FIG. 12 is a frequency characteristic diagram of a conventional objective lens driving device.

[Explanation of symbols]

 1 Objective Lens 2 Counterweight 3 Lens Holder 3a Bearing 4 Spindle 6 Focus Control Coil 7a, 7b Track Control Coil 13 Disk 21 Permanent Magnet Piece 22 Base 23 Hall Element 24, 25 Operator

Front Page Continuation (72) Inventor Takeyuki Ito 1 Baba-Zou, Nagaokakyo-shi, Kyoto Mitsubishi Electric Corporation Electronic Product Development Laboratory

Claims (4)

[Claims] 1. A lens holder rotatably and slidably held by a support shaft, an objective lens provided on the lens holder at a position eccentric from the support shaft, and the lens holder being slid and rotated. In an objective lens driving device having a driving device for focus control and track control of a light spot on the optical information recording medium, a permanent magnet piece held by the lens holder and a permanent magnet piece facing the permanent magnet piece. It is equipped with four Hall elements provided on the fixed base and an arithmetic unit for performing an arithmetic operation based on the outputs of the Hall elements, and based on the arithmetic result, the position of the objective lens in the sliding direction and the rotating direction is determined. An objective lens driving device, which detects and feeds back the position signal to the driving device to electrically support the lens holder at a midpoint position. 2. A lens holder rotatably and slidably held by a support shaft, an objective lens provided on the lens holder at a position eccentric from the support shaft, and the lens holder being slid and rotated. In the objective lens driving device having a driving device for focus control and track control of the light spot on the optical information recording medium, four Hall elements held by the lens holder are arranged so as to face the Hall elements. Equipped with a permanent magnet piece provided on the fixed base and a calculation device that performs calculation based on the output of the Hall element, and detects the position of the objective lens in the sliding direction and the rotation direction based on the calculation result. Then, the objective lens driving device is characterized in that the lens holder is electrically supported at the midpoint position by feeding back the position signal to the driving device. 3. A lens holder rotatably and slidably held by a support shaft, an objective lens provided on the lens holder at a position eccentric from the support shaft, and the lens holder being slid and rotated. In an objective lens driving device having a driving device for focus control and track control of a light spot on the optical information recording medium, a metallic counterweight held by the lens holder, the counterweight, the focus direction, and It is equipped with two capacitance detectors provided on the fixed base so as to face each other in the track direction, and a calculation device that performs calculation based on the output of the capacitance detectors. A characteristic is that the position of the objective lens in the sliding direction and the rotating direction is detected, and the position signal is fed back to the driving device to electrically support the lens holder at the midpoint position. Objective lens driving device. 4. A lens holder rotatably and slidably held on a support shaft, an objective lens provided on the lens holder at a position eccentric from the support shaft, and the lens holder sliding and turning. In the objective lens driving device having a driving device for focus control and track control of the light spot on the optical information recording medium, a metallic counterweight held by the lens holder, the counterweight and the focus direction, Two fixed eddy current displacement detectors are provided on the fixed base so as to face each other in the track direction, and a calculation device that performs calculation based on the outputs of the eddy current displacement detectors.
It is characterized in that the position of the objective lens in the sliding direction and the rotating direction is detected based on the calculation result, and the position signal is fed back to the driving device to electrically support the lens holder at the midpoint position. Objective lens driving device.