JP3798639B2 - Optical disc apparatus and driving method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc apparatus capable of detecting the tilt of an optical disc and adjusting the tilt of the optical axis of the objective lens in the tangential direction and the radial direction of the optical disc, and particularly has an actuator structure and its driving technology. The present invention relates to an optical disk device.
[0002]
[Prior art]
As a configuration of a drive system used in a conventional optical pickup device, for example, one shown in FIG. 9 is known. The configuration of this drive system is disclosed in Japanese Patent Laid-Open No. 2000-149297.
This drive system is equipped with a 4-axis actuator, and moves the objective lens 31 of the optical pickup device in the focus direction and tracking direction of the optical disk to adjust the position, thereby changing the tilt of the optical axis to the tangential tilt direction and the radial tilt. Can be adjusted in the direction.
[0003]
The actuator provided in this drive system is configured by dividing the focus coil 30 into four parts, which are wired independently. In addition, each focus coil 30 is configured to be energized independently, and is set so that all coils generate electromagnetic action (electromagnetic force) in the same direction when energized uniformly in the same direction. Accordingly, when the respective focus coils 30 are uniformly energized in the same direction, an electromagnetic force that moves the lens base 32 in the vertical direction works and focusing can be performed.
[0004]
Further, by selectively controlling energization including the direction of the current flowing through each focus coil 30, the direction and magnitude of the electromagnetic force generated by each focus coil 30 is adjusted, and the position of the lens base 32 is changed. The attitude of the objective lens 31 can be controlled.
[0005]
FIG. 10 is a diagram illustrating a configuration of a circuit that generates drive signals A, B, C, and D for driving the focus coil 30.
Here, the first difference signal V1 has a voltage having a magnitude corresponding to the amount of inclination of the optical disc in the tangential direction, and the second difference signal V2 corresponds to the amount of inclination of the optical disc in the radial direction. Has a magnitude voltage. The voltage V3 is a voltage proportional to the focus signal.
[0006]
The four drive signals A, B, C, and D supplied to the focus coil 30 have a relationship expressed by Formula 1 to Formula 4, respectively.
[Expression 1]
A = V1 + V2 + V3
[Expression 2]
B = V1-V2 + V3
[Equation 3]
C = -V1-V2 + V3
[Expression 4]
D = −V1 + V2 + V3
[0007]
[Problems to be solved by the invention]
In the above prior art, each focus coil 30 is wired independently. Moreover, in the said prior art, the tracking coil for moving the objective lens 31 to a tracking direction other than each focus coil 30 is needed.
For this reason, the wiring material from the lens base 32 becomes ten corresponding to five coils, and there is a problem that the drawing structure becomes complicated.
In addition, five amplifiers for driver circuits for driving the coils had to be provided.
Further, since the focus coil 30 also functions as a tilt coil, there is a problem that three servo control loops (focus servo, tangential tilt servo, and radial tilt servo) are synthesized, and operation control becomes complicated.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical disc apparatus having an actuator structure that can easily control the operation with a simple configuration.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an optical disc apparatus according to the first aspect of the present invention provides:
The optical disk is irradiated with a light beam using an objective lens to reproduce or record information,
A focus coil for adjusting the distance between the objective lens and the optical disc;
A tracking coil for moving a lens base supporting the objective lens in a radial direction of the optical disc;
First and second tilt coils for adjusting the tilt of the optical axis of the objective lens ;
A light receiving means for detecting a light beam reflected by the optical disc with four photodetectors and generating four signals corresponding to the intensity of the detected light;
First subtracting means for supplying a signal corresponding to a difference between two signals generated by two photodetectors provided at diagonal positions of the light receiving means to the first tilt coil;
A signal corresponding to the difference between the two signals generated by the two photodetectors of the light receiving means provided at different diagonal positions from the two photodetectors supplying the signal to the first subtracting means, Second subtracting means for supplying to the second tilt coil ,
The first tilt coil is provided in a diagonal position of the lens base with the objective lens as a center and is connected in series, and a first electromagnetic coil having a reverse direction with the objective lens as a center is applied by energization. Comprising a second coil;
The second tilt coil is provided at a diagonal position of the lens base where the first and second coils are not provided, and is connected in series with the objective lens as a center, and is centered on the objective lens when energized. Including third and fourth coils that act as electromagnetic forces in opposite directions,
It is characterized by that.
[0010]
According to the present invention, the first tilt coil includes the first and second coils connected in series in which an electromagnetic force in the reverse direction centered on the objective lens is applied by energization. In addition, the second tilt coil includes third and fourth coils connected in series in which an electromagnetic force in the reverse direction around the objective lens acts when energized.
This simplifies the configuration of a circuit for adjusting the position and tilt of the objective lens. In addition, since the focus coil is provided separately from the first and second tilt coils, the operation can be easily controlled.
[0011]
A first amplifier that drives the focus coil by supplying a current;
A second amplifier that drives the tracking coil by supplying a current;
A third amplifier that drives the first tilt coil by supplying a current;
A fourth amplifier that drives the second tilt coil by supplying a current;
It is desirable.
[0014]
A method of driving an optical disc device according to the second aspect of the present invention includes:
A method of driving an optical disc apparatus that reproduces or records information by irradiating an optical disc with an optical lens using an objective lens,
A focus adjustment step in which a first amplifier supplies a current to the focus coil to adjust a distance between the objective lens and the optical disc;
A tracking adjustment step in which a second amplifier supplies a current to the tracking coil to move a lens base supporting the objective lens in a radial direction of the optical disc;
A third amplifier supplies current to first and second coils provided in a diagonal position of the lens base with the objective lens as the center and connected in series, and the first and second coils A fourth amplifier supplies current to third and fourth coils that are provided in the diagonal position of the lens base that is not provided with a coil and is connected in series with the objective lens as a center, and the objective lens A tilt adjustment step for adjusting the tilt of the optical axis in the tangential direction and radial direction of the optical disc ,
The inclination adjustment step includes:
A light receiving step in which four light detectors detect a light beam reflected by the optical disc and generate a signal corresponding to the detected light;
A first subtracting circuit configured to generate a signal corresponding to a difference between the two signals generated by the two photodetectors provided at diagonal positions and to supply the first signal to the third amplifier; A subtraction step;
The second subtracting circuit calculates a difference between two signals generated by the two photodetectors provided at different diagonal positions from the two photodetectors that supply signals to the first subtracting circuit. A second signal subtraction step for generating a corresponding signal and supplying the corresponding signal to the fourth amplifier,
It is characterized by that.
[0015]
According to the present invention, the first to fourth amplifiers can be used to supply current to the focus coil and tracking coil and the first to fourth coils for driving.
Thereby, the position and inclination of the objective lens can be adjusted with a simple configuration. In addition, since the focus coil is provided separately from the first to fourth coils for adjusting the tilt of the objective lens, the operation can be easily controlled.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical disk device according to an embodiment of the present invention will be described in detail with reference to the drawings.
This optical disc apparatus includes a tilt actuator 100 in order to control the tilt of the optical axis of the objective lens.
[0019]
1 and 2 are perspective views illustrating the structure of the actuator 100 provided in the optical disc apparatus.
Here, FIG. 1 shows an example configured with a moving coil system (MC system), and FIG. 2 shows an example configured with a moving magnet system (MM system). As shown in FIGS. 1 and 2, the actuator 100 includes a focus coil 1, a tracking coil 2, tilt coils 3 and 4, a magnet 5, an objective lens 6, a lens base 7, a yoke 8, and a damper. 9, a holder 10, silicon rubber 11, and a holding portion 12.
3 is a diagram showing wiring of the tilt coils 3 and 4, and FIG. 4 is a diagram showing a configuration of the driver circuit 13 that supplies a drive current to the actuator 100 and the like.
[0020]
The focus coil 1 is for adjusting the distance between the optical disk and the actuator 100 and moving the focal position of the light beam by an electromagnetic force that acts when energized. In the actuator 100 configured with the MC system shown in FIG. 1, the focus coil 1 is wound around the lens base 7 so as to surround the objective lens 6 so as to be sandwiched between magnetic circuits formed by the magnet 5 and the yoke 8. It is configured. Further, in the actuator 100 configured by the MM method shown in FIG. 2, the focus coil 1 is wound around the tilt coils 3 and 4.
[0021]
The tracking coil 2 is for moving the actuator 100 in the radial direction of the optical disk by an electromagnetic force acting when energized. In the actuator 100 configured by the MC system shown in FIG. 1, the tracking coil 2 is configured to be wound so as to wrap around the tilt coils 3 and 4 provided on both sides of the lens base 7. Further, in the actuator 100 configured by the MM method shown in FIG. 2, the tracking coil 2 is configured so as to be wrapped around the focus coil 1 and the tilt coils 3 and 4, and is disposed at both ends of the lens base 7. .
Note that the tracking coil 2 on the right side of FIG. 1 is omitted to illustrate the internal tilt coils 3 and 4. Further, the tracking coil 2 on the near side in FIG. 2 is also shown with a part omitted in order to illustrate the internal coil.
[0022]
As shown in FIG. 3, the tilt coil 3 is composed of two coils 3 a and 3 b connected in series, and for adjusting the tilt of the optical axis in the objective lens 6 by electromagnetic force acting between the magnet 5 and the tilt coil 3. Is.
The two coils 3a and 3b are provided at diagonal positions of the lens base 7 with the objective lens 6 as the center, and an electromagnetic force in a direction in which the objective lens 6 is tilted works when energized. That is, for example, when the two coils 3a and 3b provided at the horizontal position are energized, electromagnetic forces directed to the magnets 5 from the horizontal position in opposite directions (up and down directions) act on the optical axis of the objective lens 6. Adjust the tilt.
[0023]
As shown in FIG. 3, the tilt coil 4 includes two coils 4 a and 4 b connected in series, and adjusts the tilt of the optical axis of the objective lens 6 by electromagnetic force acting between the magnet 5 and the tilt coil 4. Is.
The two coils 4a and 4b are provided at diagonal positions different from the positions where the two coils 3a and 3b are arranged at the diagonal position of the lens base 7 with the objective lens 6 as the center. The electromagnetic force in the direction of tilting the lens 6 works.
[0024]
The magnet 5 is a permanent magnet for generating an electromagnetic force when the tilt coils 3 and 4 are energized.
The objective lens 6 is for irradiating the optical disk with a light beam emitted from a light emitting diode, a semiconductor laser or the like, and is installed at the center of gravity of the lens base 7.
The lens base 7 is for supporting the objective lens 6, and is connected to the holding unit 12 via the silicon rubber 11.
[0025]
The yoke 8 is made of, for example, a ferromagnetic material, and forms a magnetic circuit with the magnet 5 to generate an electromagnetic force with the focus coil 1, tracking coil 2, tilt coils 3, 4. Is.
The damper 9 is for connecting the holder 10 and the holding portion 12 and holding the lens base 7 with a degree of freedom in the radial direction of the optical disc.
The holder 10 is for supporting the damper 9.
[0026]
The silicon rubber 11 has elasticity and connects the lens base 7 and the holding portion 12 to hold the lens base 7 with a degree of freedom in the tangential direction of the optical disc.
The holding part 12 is for holding the lens base 7 via the silicon rubber 11.
[0027]
The driver circuit 13 shown in FIG. 4 is a circuit for supplying a current flowing through the focus coil 1, the tracking coil 2, and the tilt coils 3 and 4, and includes four amplifiers 13a to 13d.
Each of the amplifiers 13a to 13d is a BTL amplifier (Balanced Transformless Amplifier), and supplies current to the focus coil 1, the tracking coil 2, and the tilt coils 3 and 4, respectively.
The amplifiers 13a to 13d and the focus coil 1, the tracking coil 2, and the tilt coils 3 and 4 are connected via a wire having a low stress.
[0028]
FIG. 5 is a diagram illustrating an example of the configuration of the tilt detection circuit 14 that drives the amplifiers 13c and 13d.
As illustrated, the tilt detection circuit 14 includes phase compensation circuits 15 and 16, an addition circuit 17, subtraction circuits 18 to 20, a light receiving element 21, and inverting circuits 22a to 22d.
[0029]
The phase compensation circuit 15 is connected to the amplifier 13c and compensates the phase of the signal supplied to the tilt coil 3.
The phase compensation circuit 16 is connected to the amplifier 13d and compensates the phase of the signal supplied to the tilt coil 4.
[0030]
The adder circuit 17 has an output terminal connected to the phase compensation circuit 15, and a tangential error signal T and a radial error signal R are input to two non-inverting input terminals.
The subtraction circuit 18 has an output terminal connected to the phase compensation circuit 16. A radial error signal R is input to the non-inverting input terminal of the subtracting circuit 18, and a tangential error signal T is input to the inverting input terminal.
[0031]
The subtraction circuit 19 is a circuit for generating a tangential error signal T, and corresponds to the difference between the sum signal of the outputs from the inverting circuits 22a and 22b and the sum signal of the outputs from the inverting circuits 22c and 22d. Generate a signal.
The subtraction circuit 20 is a circuit for generating a radial error signal R, and is a signal corresponding to the difference between the sum signal of the outputs from the inverting circuits 22a and 22d and the sum signal of the outputs from the inverting circuits 22b and 22c. Is output.
[0032]
The light receiving element 21 includes four photodetectors 21a to 21d, detects a light beam reflected by the optical disc, and generates a current having a magnitude corresponding to the intensity of the detected light.
The photodetectors 21a to 21d are connected to the inverting circuits 22a to 22d, respectively.
The inverting circuits 22a to 22d are I / V amplifiers for converting the current signals received from the photodetectors 21a to 21d into voltage signals.
[0033]
The operation of the optical disk apparatus according to the embodiment of the present invention will be described below.
In this optical disc apparatus, the position and inclination of the objective lens 6 are adjusted by controlling the current supplied to the focus coil 1, the tracking coil 2, and the tilt coils 3 and 4 by the driver circuit 13.
[0034]
That is, by controlling the current supplied from the amplifier 13a to the focus coil 1, the lens base 7 is moved in the focus direction, and the distance between the objective lens 6 and the optical disk is adjusted. Thereby, the focal position of the light beam can be adjusted.
Further, by controlling the current supplied from the amplifier 13b to the tracking coil 2, the position of the lens base 7 is moved in the tracking direction, and the position of the objective lens 6 in the tracking direction of the optical disk is adjusted.
[0035]
Moreover, the inclination of the optical axis in the objective lens 6 is adjusted by controlling the current supplied to the tilt coils 3 and 4 from the amplifiers 13c and 13d.
FIG. 6 is a diagram for explaining the principle of operation in which the tilt coils 3 and 4 adjust the tilt of the objective lens 6.
[0036]
When the two coils 3a and 3b constituting the tilt coil 3 are energized, electromagnetic forces directed in opposite directions with respect to the objective lens 6 act. Further, when the two coils 4 a and 4 b constituting the tilt coil 4 are energized, electromagnetic forces directed in opposite directions around the objective lens 6 act.
For example, when the coil 3a is energized and an electromagnetic force directed upward along the optical axis in the objective lens 6 acts, an electromagnetic force directed downward about the objective lens 6 acts on the coil 3b. Similarly, for example, when the coil 4a is energized and an electromagnetic force directed upward along the optical axis in the objective lens 6 acts, the coil 4b receives an electromagnetic force directed downward from the objective lens 6 as a center. work.
[0037]
Thus, when the coils 3a and 4a are driven in the upward direction with the same electromagnetic force and the coils 3b and 4b are driven in the downward direction with the same electromagnetic force, the tilt in the tangential direction is controlled. Can do. The same applies when the coils 3a and 4a are driven downward and the coils 3b and 4b are driven upward. Further, when the coils 3a and 4b are driven with the same electromagnetic force in the upward direction and the coils 3b and 4a are driven with the same electromagnetic force in the downward direction, the radial tilt can be controlled. it can. The same applies when the coils 3a and 4b are driven downward and the coils 3b and 4a are driven upward.
By simultaneously driving the tilt coils 3 and 4 as described above, the tilt of the objective lens 6 can be adjusted in the tangential direction and the radial direction of the optical disc.
[0038]
Next, the operation of the tilt detection circuit 14 that drives by supplying current to the tilt coils 3 and 4 will be described.
The tilt detection circuit 14 supplies a current corresponding to the light beam detected by the light receiving element 21 to the tilt coils 3 and 4.
Here, output signals of the photodetectors 21a to 21d are Sa to Sd, respectively.
[0039]
At this time, the subtraction circuit 19 generates a tangential error signal T having the relationship shown in Formula 5.
[Equation 5]
T = ((− Sa) + (− Sb)) − ((− Sc) + (− Sd))
[0040]
Further, the subtraction circuit 20 generates a radial error signal R having the relationship shown in Equation 6.
[Formula 6]
R = ((− Sa) + (− Sd)) − ((− Sb) + (− Sc))
[0041]
The adder circuit 17 generates a tilt detection signal TILT_X having the relationship shown in Expression 7 and supplies the tilt detection signal TILT_X to the tilt coil 3 through the phase compensation circuit 15.
[Expression 7]
TILT_X = T + R
[0042]
The subtraction circuit 18 generates a tilt detection signal TILT_Y having the relationship shown in Expression 8 and supplies the tilt detection signal TILT_Y to the tilt coil 4 through the phase compensation circuit 16.
[Equation 8]
TILT_Y = TR
[0043]
The tilt detection circuit 14 adjusts the tilt of the objective lens 6 by supplying current to the tilt coils 3 and 4 so as to control the light spot of the light receiving element 21 to be at the center of the photodetectors 21a to 21d.
That is, for example, as shown in FIG. 7 with hatching, it is assumed that the light spot is shifted in the radial direction from the centers of the photodetectors 21a to 21d. In this case, the tilt detection circuit 14 adjusts the tilt of the optical axis in the objective lens 6 in the radial direction of the optical disc by supplying a current for controlling the tilt in the radial direction to the tilt coils 3 and 4. As a result, the light spot can be moved to the position indicated by the dotted line in FIG. 7 and arranged at the center of the photodetectors 21a to 21d.
[0044]
In this way, information can be recorded on or reproduced from the optical disc by adjusting the tilt of the objective lens 6 in the tangential direction and radial direction of the optical disc, irradiating the optical disc with the light beam, and detecting the reflected light. it can.
[0045]
As described above, according to the present invention, the four amplifiers 13a to 13d can be driven by supplying current to the focus coil 1, the tracking coil 2, and the tilt coils 3 and 4. According to the present invention, since the focus coil 1 is provided separately from the tilt coils 3 and 4, the distance between the objective lens 6 and the optical disc is adjusted independently of the tilt of the optical axis. be able to.
Thereby, the number of parts can be reduced, and the operation can be easily controlled with a simple configuration.
[0046]
The present invention is not limited to the above embodiment, and various modifications and applications are possible.
For example, in the above-described embodiment, the tilt detection circuit 14 has been described as generating the current to be supplied to the tilt coils 3 and 4 using the tangential error signal T and the radial error signal R. It is not limited.
That is, for example, as shown in FIG. 8, the tilt detection circuit 14 may be configured by using two subtraction circuits 23 and 24. In this case, a signal for supplying a current to the tilt coils 3 and 4 can be generated without generating the tangential error signal T and the radial error signal R.
[0047]
【The invention's effect】
As described above, according to the present invention, the number of amplifiers for driving by supplying current to the coil can be reduced, and the operation can be easily controlled with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating the structure of an actuator provided in an optical disc apparatus according to an embodiment of the invention.
FIG. 2 is a perspective view illustrating the structure of an actuator provided in the optical disc apparatus according to the embodiment of the invention.
FIG. 3 is a diagram showing wiring of a tilt coil.
FIG. 4 is a diagram illustrating a configuration of a driver circuit.
FIG. 5 is a diagram illustrating an example of a configuration of a tilt detection circuit.
FIG. 6 is a diagram for explaining the principle of operation in which a tilt coil adjusts the tilt of an objective lens.
FIG. 7 is a diagram showing a light spot of a light receiving element.
FIG. 8 is a diagram showing a modification of the tilt detection circuit.
FIG. 9 is a diagram showing a configuration of a drive system used in a conventional optical pickup device.
FIG. 10 is a diagram illustrating a circuit that generates a signal for driving a focus coil included in a conventional optical pickup device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 30 Focus coil 2 Tracking coil 3, 4 Tilt coil 3a, 3b, 4a, 4b Coil 5 Magnet 6, 31 Objective lens 7, 32 Lens base 8 Yoke 9 Damper 10 Holder 11 Silicon rubber 12 Holding part 13 Driver circuit 13a- 13d Amplifier 14 Tilt detection circuit 15, 16 Phase compensation circuit 17 Addition circuit 18-20 Subtraction circuit 21 Light receiving element 21a-21d Photo detector 22a-22d Inversion circuit

Claims (3)

An optical disk device for reproducing or recording information by irradiating an optical disk with an optical lens using an objective lens,
A focus coil for adjusting the distance between the objective lens and the optical disc;
A tracking coil for moving a lens base supporting the objective lens in a radial direction of the optical disc;
First and second tilt coils for adjusting the tilt of the optical axis of the objective lens ;
A light receiving means for detecting a light beam reflected by the optical disc with four photodetectors and generating four signals corresponding to the intensity of the detected light;
First subtracting means for supplying a signal corresponding to a difference between two signals generated by two photodetectors provided at diagonal positions of the light receiving means to the first tilt coil;
A signal corresponding to the difference between the two signals generated by the two photodetectors of the light receiving means provided at diagonal positions different from the two photodetectors supplying the first subtracting means, Second subtracting means for supplying to the second tilt coil ,
The first tilt coil is provided at a diagonal position of the lens base with the objective lens as a center and is connected in series, and a first electromagnetic force acting in a reverse direction with the objective lens as a center is applied when energized. A second coil;
The second tilt coil is provided in the diagonal position of the lens base where the first and second coils are not provided, and is connected in series with the objective lens as a center, and the objective lens is centered by energization. Including third and fourth coils that act as electromagnetic forces in opposite directions,
An optical disc device characterized by the above. A first amplifier that drives the focus coil by supplying a current;
A second amplifier that drives the tracking coil by supplying a current;
A third amplifier that drives the first tilt coil by supplying a current;
A fourth amplifier that drives the second tilt coil by supplying a current;
The optical disc apparatus according to claim 1, wherein: A method of driving an optical disc apparatus that reproduces or records information by irradiating an optical disc with an optical lens using an objective lens,
A focus adjustment step in which a first amplifier supplies a current to the focus coil to adjust a distance between the objective lens and the optical disc;
A tracking adjustment step in which a second amplifier supplies a current to the tracking coil to move a lens base supporting the objective lens in a radial direction of the optical disc;
A third amplifier supplies current to first and second coils provided in a diagonal position of the lens base with the objective lens as the center and connected in series, and the first and second coils A fourth amplifier supplies current to third and fourth coils that are provided in the diagonal position of the lens base that is not provided with a coil and is connected in series with the objective lens as a center, and the objective lens A tilt adjustment step for adjusting the tilt of the optical axis in the tangential direction and radial direction of the optical disc ,
The inclination adjustment step includes:
A light receiving step in which four light detectors detect a light beam reflected by the optical disc and generate a signal corresponding to the detected light;
A first subtracting circuit configured to generate a signal corresponding to a difference between the two signals generated by the two photodetectors provided at diagonal positions and to supply the first signal to the third amplifier; A subtraction step;
The second subtracting circuit calculates a difference between two signals generated by the two photodetectors provided at different diagonal positions from the two photodetectors that supply signals to the first subtracting circuit. A second signal subtraction step for generating a corresponding signal and supplying the corresponding signal to the fourth amplifier,
A method for driving an optical disk device, comprising:

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