JPH10320789A - Vibration suppressing method for positioning mechanism and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a constant focus control by constituting an optical disk device with a biaxial lens translation driving mechanism positioning an objective lens in the direction of an optical axis and a radial direction and a translation coarse adjusting mechanism moving the whole area of the recording range of the optical disk while mounting the objective lens to suppress a revolving combined vibration between both mechanisms to be generated around an axis parallel with the tangential direction of the circumference of an optical disk. SOLUTION: When a distance in a direction vertical to the surface of an optical disk 40 between the position of the point of action of the driving force fp of a translation coarse adjusting mechanism 43, a distance in the vertical direction between the centorid (g) of a boaxial lens translation driving mechanism 42 and the centroid G of the translation coarse adjusting mechanism 43, the primary resonance frequency of the supporting system of the mechanism 43, the gain cross angular frequency of the control system of the mechanism 43, the time constant ratio between phase compensation circuits of the control system of the mechanism 43 and the ratio of the mass of the mechanism 42 to the mass of the mechanism 43 are respectively defined as hp , ha , ωp1 , ωp0 , γp and μ, the ratio of hp to ha is set based on a value to be calculated from an equation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing vibration of a positioning mechanism for positioning the focus of an objective lens of an optical disk device on a predetermined track following the eccentricity of an optical disk, and an optical disk device.

[0002]

2. Description of the Related Art In a track following control of an optical disk apparatus, a biaxial lens translation drive mechanism (lens actuator) is optically detected based on a positional deviation (tracking error) between a track of an optical disk and a focal point of an objective lens. The movable part) is precisely driven in the radial direction of the optical disk, and the biaxial lens translation drive mechanism is mounted, and the translational coarse movement mechanism (positioner movable part) that moves over the entire recording range in the radial direction of the optical disk is provided by an objective lens. With a two-step servo control system that follows the movement of the track, a high tracking accuracy of 0.1 micron or less is achieved for a track pitch of about 1 micron.

FIG. 6 shows a schematic diagram of such a positioning mechanism. This positioning mechanism moves the entire recording range in the radial direction on the recording surface side of the optical disc 40 and has a cross-sectional shape of L.
A positioner movable portion 43 having a character shape, and a positioner movable portion 43
The L-shaped wall portion is schematically illustrated as being supported via a spring damper 41 (spring constant k ₂ , braking coefficient c ₂ ) so that the focal point F is located on the surface of the optical disc 40.
And a lens actuator movable section 42 of the objective lens. The positioner movable portion 43 has an L-shaped bottom portion,
Rollers 48 and 49 and spring dampers 44 and 46 (spring constant k) which move on a base 50 fixed to the optical disk device main body.
₁ and a braking coefficient c ₁ ) (the distance between the two rollers 48 and 49 is l).
(E), and the radial position of the optical disc 40 at the center of gravity G divides the interval l into ρ: 1−ρ.

Normally, the lens actuator movable section 42
Is the focal length d _f of the objective lens is short, it is placed on the optical disc 40 side of the positioner movable portion 43. Therefore,
Centroid g of the lens actuator moving portion 42 is at a position spaced on the optical disc 40 side than the center of gravity G of the positioner movable portion 43, the spaced distance of the surface perpendicular to the direction of the optical disk 40 and h _a. Usually, (radial direction of the optical disk 40) driving force f _a of the lens actuator moving portion 42 exerts according to the position of the center of gravity g of the movable portion for movement stabilizing. Therefore, the driving force f _a acts on a position where the distance h _a is spaced from the center of gravity G of the positioner movable portion 43. Further, conventionally, (a radial direction of the optical disk 40) driving force f _p positioner movable portion 43 is also adapted to act on the center of gravity G of the positioner movable portion 43 including the lens actuator moving section 42.

[0005]

In such a dynamic system, the optical disk 40 is parallel to the surface of the optical disk 40 and
It is clear that the couple acts about an axis which is perpendicular to the radial direction of. Therefore, at the time of track following control, pitching mode resonance is excited, and the resonance frequency is
The rigidity of the bearings 44, 46, 48, 49 supporting the positioner movable part 43 (carriage) and the positioner movable part 4
3 inertia. Due to this resonance, the focal point F of the objective lens also vibrates in the radial direction of the optical disk 40 (coupled rotational vibration), and as a result, the track following control system oscillates, making it impossible to perform accurate track following control. Was.

The present invention has been made in view of the above-described circumstances, and suppresses coupled rotational vibration between a translational coarse movement mechanism and a two-axis lens translation drive mechanism in an optical disk drive, thereby achieving a stable and accurate focus. It is an object of the present invention to provide a method for suppressing vibration of a positioning mechanism and an optical disk device capable of realizing control.

[0007]

According to a first aspect of the present invention, there is provided a method for suppressing vibration of a positioning mechanism, comprising: a biaxial lens translation drive mechanism for positioning an objective lens of an optical disk device in an optical axis direction and a radial direction of the optical disk; And a translational coarse movement mechanism that carries an axial lens translation drive mechanism and moves over the entire recording range in the radial direction of the optical disc, wherein a vibration suppressing method for a positioning mechanism includes: between the center of gravity position and the translating coarse positioner, a distance between the optical disc surface and vertical to the h _p, between the center of gravity of the center of gravity and the translation coarse adjustment mechanism of the two-axis lens translation drive mechanism, the vertical a distance direction is h _a, the first-order resonance frequency of the translation coarse mechanism support system and omega _p1, the gain cross angular frequency of the translation coarse feed mechanism control system and omega _p0, the translation coarse feed mechanism control system For phase compensation circuit The number ratio and gamma _p, the mass and the mass ratio of the translation coarse adjustment mechanism of the two-axis lens translation drive mechanism when the mu, wherein the ratio of the h _p and the h _a (1)

[0008]

(Equation 3)

[0009] By setting based on the value obtained by the above, the rotationally coupled vibration of the biaxial lens translation drive mechanism and the translational coarse movement mechanism generated around an axis parallel to the tangential direction of the circumference of the optical disk. Is suppressed.

An optical disk apparatus according to a second aspect of the present invention is a biaxial lens translation drive mechanism for positioning an objective lens of the optical disk apparatus in the optical axis direction and the radial direction of the optical disk, and the optical disk mounted with the biaxial lens translation drive mechanism. An optical disc apparatus having a positioning mechanism having a translational coarse movement mechanism that moves over the entire recording range in the radial direction, wherein the translational coarse movement mechanism and the two-axis lens translation drive mechanism have a driving force of the translation coarse movement mechanism. between the center of gravity position and the translating coarse adjustment mechanism of action points, the distance between the optical disc surface and vertical to the h _p, between the center of gravity of the center of gravity and the translation coarse adjustment mechanism of the two-axis lens translation drive mechanism , the distance of the vertical direction is h _a,
The primary resonance frequency of the translational coarse mechanism support system is ω _p1 ,
The gain cross angular frequency of the translational coarse mechanism control system is ω _p0
When the time constant ratio of the phase compensation circuit of the translation coarse movement mechanism control system is γ _p and the ratio of the mass of the two-axis lens translation drive mechanism to the mass of the translation coarse movement mechanism is μ, 1)

[0011]

(Equation 4)

And having the h _p and the h _a determined based on the value determined by [0012].

[0013] Figure 2 is a block diagram of FIG. 1 shown in (a driving force other than the active position of the f _p is the same as FIG. 6), positioning mechanism optical disk apparatus according to the present invention (track following control system) It is. This block diagram shows a Laplace transform U (s) of an input signal u (t) which is an eccentric amount of a track.
However, through the addition point 10, the transfer function C ₂ (s) = ω _t0 of the phase advance compensation circuit of the lens actuator control system
² (1 + γ _t ^1/2 s / ω _t0 ) / (γ _t ^1/2 (1 + s /
(Ω _t0 γ _t ^1/2 ))). Here, ω _t0 is a gain cross angular frequency of the lens actuator control system, and γ _t is a constant of a phase compensation circuit of the lens actuator control system.

The output of the transmission element 11 is
Through the tracking of the lens actuator movable section 42
Transfer function T (s) =
1 / (s^Two+ 2ζ_t1ω_t1s + ω_t1 ^Two) Is the transmission element 1
3 given. Where ω _t1And ζ_t1Is a lens act
Primary resonance frequency of damper movable part support leaf spring and damper
Coefficient.

The output of the transfer element 13, as a displacement X ₂ (s) of the lens actuator moving portion 42, a summing point 21 is added, the transmission element 15 is a transfer function s ^2, the transfer function s ² -2ζ _t1 ω _t1 a transfer element 17 is s-omega _t1 ^2, the phase lead compensation circuit positioner control system transfer function C
₁ (s) = ω _p0 ² (1 + γ _p ^1/2 s / ω _p0 ) / (γ _p
Transfer element 1 which is ^1/2 (1 + s / (ω _p0 γ _p ^1/2 )))
4 and given. Here, ω _p0 is a gain crossing angular frequency of the positioner control system, and γ _p is a constant of a phase compensation circuit of the positioner control system.

The output of the transfer element 15 is a coefficient μ
Are applied to a subtraction point 19, and the output of the transmission element 17 is applied to a subtraction point 18. Here, μ = m / M. Here, m is the mass of the lens actuator movable section 42, and M is the mass of the positioner movable section 43. The output of the transmission element 14 is the summing point 19,
After being multiplied by the coefficient ξ _p by the element 25, it is given to the addition point 26.

The output of the addition point 19 is the subtraction point 1
2, a subtraction point 18 and a transfer element 20 having a transfer function P (s) = s ⁻² representing the compliance characteristic of the positioner movable section 43. The output of the subtraction point 18 is multiplied by η _a by the element 23 and then the subtraction point 2
6 given. Here, an ^{_{η a = mh a 2 / J}} .
However, h _a is the center of gravity g of lens actuator moving section 42
A distance between the center of gravity of the optical disc 40 and the center of gravity G of the positioner movable part 43, and J is a moment of inertia around the center of gravity G of the positioner movable part 43.

The output of the transmission element 20 is
43 displacement X₁(S) as given to the addition point 21
The output of the addition point 21 is given to the subtraction point 10.
available. The output of the addition point 26 is the pitching mode.
Input Q to compliance _iAs pitching
Transfer function A representing the compliance characteristic of mode resonance
(S) = 1 / (s^Two+ 2ζ_p1ω_p1s + ω_p1 ^Two) Is a biography
To the delivery element 27. Where ω_p1And ζ_p1Is positive
Primary resonance frequency and damping of the support system of the shocker movable part 43
It is a coefficient.

The output of the transfer element 27 includes a transfer element 28 is a transfer function s ^2, the transfer function _{^{s 2 -2ζ t ω t1 s-}} ω t1
^2, which is a transmission element 29. Also, element 22
Is multiplied by the coefficient 1 + λ, and is given to the addition point 21 as the displacement X ₃ (s) of the focal point F of the objective lens due to the pitching mode resonance. The output of the transmission element 28 is
After being multiplied by the factor μ in element 24, a subtraction point 19
Given to.

The output of transmission element 29 is applied to subtraction point 12
And the coefficient μη in element 30_z/ Η_aMultiply
After being passed, the objective lens of the support system of the positioner movable part 43
Transfer function 1 / that represents the compliance characteristic in the optical axis direction of
(S^Two+ 2ζ_z1ω_z1s + ω_z1 ^Two) To the transmission element 32
Given. Where ω_z1And ζ_z1Is the movable part of the positioner
43 primary resonance frequency of the supporting system in the optical axis direction of the objective lens
And the damping coefficient. Also, η_z= Ml_ah_a/
J. Where l_aIs the lens actuator movable part 4
2 and the center of gravity G of the positioner movable part 43,
The distance in the radial direction of the optical disc 40.

The output of the transfer element 32 is obtained as a displacement Z (s) of the focal point F of the objective lens in the radial direction of the optical disk 40 and is given to a transfer element 33 having a transfer function s ² . The output of the transfer element 33 is the coefficient η _z
, And is given to an addition point 26.

In the above block diagram, the input U
FIG. 3A shows the result of calculating a loop transfer function from (s) to the displacement Z (s), and FIG. 3 shows various constants used in this calculation.
(B). In FIG. 3A, the horizontal axis represents frequency, and the vertical axis represents gain and phase. Here, at a frequency (こ と が 1.6 kHz) corresponding to the resonance frequency of the pitching mode, it can be seen that a gain peak appears, the phase is delayed, the phase margin is reduced, and thus the stability is reduced. That is, it is understood that the control system is unstable due to the coupled vibration of the biaxial lens translation drive mechanism (lens actuator) and the translation coarse movement mechanism (positioner).

[0023] Figure 4, between the working point of the drive force f _p of the center of gravity G and the positioner movable part of the positioner movable portion 43, the distance h _p (FIG surface and vertical direction of the optical disc 40 (disc direction is positive) 6 is 0), and FIG.
FIG. 4 is a result of calculating a loop transfer function similar to FIG.
In FIG. 4A, the frequency is taken on the horizontal axis, and the gain is taken on the vertical axis. In FIG. 4B, the frequency is taken on the horizontal axis, and the phase is taken on the vertical axis. Distance h various constants other than _p are, and FIG. 3 (b)
Is the same as the value shown in FIG.

[0024] Here, as the distance h _p changes from positive to negative, the phase delay becomes small and the phase margin increases, it can be seen that the stability is increased. This is because, by moving the position of the point of application of the driving force of the positioner movable portion 43 away from the lens actuator movable portion 42, the couple acting around the center of gravity of the positioner movable portion 43 by the driving force of the positioner movable portion 43, and the lens Actuator movable part 42
It is considered that the result is that the resonance of the pitching mode is suppressed because the couple acting by the driving force is balanced.

This is because the input Q _i to the pitching mode compliance in the block diagram shown in FIG.
Is equivalent to having been deleted. When this condition is expressed by a mathematical expression, it is as shown in an expression (2).

[0026]

(Equation 5)

Here, under this condition, the displacement X ₃ (s) = 0 of the objective lens focal point F due to the pitching mode resonance.
Is considered. In addition, the resonance frequency of the pitching mode is generally 1 kHz or higher, higher than the gain cross frequency of the positioner control system (400 Hz or lower), and higher than the resonance frequency of the lens actuator movable unit 42 support system (100 Hz or lower). (3)
The approximation as in the equation (4) becomes possible.

[0028]

(Equation 6)

By substituting these into equation (2), the relation of equation (5) is obtained.

[0030]

(Equation 7)

Further, s = jω _p1 (j is the square root of −1)
Is finally obtained, the relationship of equation (1) is obtained.

[0032]

(Equation 8)

The positioner movable portion 43 which satisfies this relationship.
Do it in by setting the position of the acting point of the driving force f _p, it is possible to prevent the destabilization of the tracking control system due to pitching mode resonance. However, as described above, h
_p is between the center of gravity G of the position of the acting point of the driving force f _p positioner movable portion 43 and the positioner movable portion 43, the distance perpendicular to the surface direction of the optical disc 40, h _a is a lens actuator moving section Ω _p1 is the primary resonance frequency of the positioner movable unit 43 support system, and ω _p0 is the positioner between the center of gravity g of 42 and the center of gravity G of the positioner movable unit 43 in the direction perpendicular to the surface of the optical disk 40. It is the gain crossing angular frequency of the control system, and γ _p is a constant of the phase compensation circuit of the positioner control system. Further, μ = m / M. Here, m is the mass of the lens actuator movable section 42, and M is the mass of the positioner movable section 43.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. FIG. 1 is a schematic view schematically showing a configuration of a positioning mechanism showing an embodiment of a method for suppressing vibration of the positioning mechanism according to the present invention. The positioning mechanism includes a positioner movable part 43 (translational coarse movement mechanism) having an L-shaped cross section and moving over the entire radial recording range on the recording surface side of the optical disc 40;
The L-shaped wall portion is schematically illustrated as being supported via a spring damper 41 (spring constant k ₂ , braking coefficient c ₂ ) so that the focal point F is located on the surface of the optical disc 40.
And a lens actuator movable section 42 (a biaxial lens translation drive mechanism) of the objective lens.

The movable portion 43 of the positioner has an L-shaped bottom portion.
Moves on the substrate 50 fixed to the optical disk device body
Rollers 48, 49 and spring dampers 44, 46 (spring set)
Number k ₁, Braking coefficient c₁) Is supported by rolling bearings
(The distance between both rollers 48, 49 is
1 (L) in the radial direction of the optical disc 40 at the center of gravity G
Divides the interval l into ρ: 1−ρ).

The center of gravity g of the lens actuator movable section 42 is located at _a distance ha in the direction perpendicular to the surface of the optical disk 40 from the center of gravity G of the positioner movable section 43. Driving force f _a of lens actuator movable section 42
(In the radial direction of the optical disc 40)
The operation is performed in accordance with the position of the center of gravity g. Driving force f _p positioner movable portion 43, between the center of gravity G of the position and the positioner movable portion 43 of the point of action, the distance h _p of the surface perpendicular to the direction of the optical disc 40, a generally relationship of formula (1) It works to satisfy.

[0037]

(Equation 9)

Here, ω _p1 is the primary resonance frequency of the positioner movable section 43 support system, ω _p0 is the gain cross angular frequency of the positioner control system, and γ _p is the constant of the phase compensation circuit of the positioner control system. . Further, μ = m / M.
Here, m is the mass of the lens actuator movable section 42, M
Is the mass of the positioner movable part 43.

In the positioning mechanism having such a configuration,
Figure 3 (b) to when the various constants shown, position and positioner movable part 4 of the acting point of the driving force f _p positioner movable portion 43
Between 3 the center of gravity G, the optimum value of the distance h _p of the surface perpendicular to the direction of the optical disk 40, as calculated by Equation (1), h
_p = −1.91 mm. This corresponds to h in FIG.
_This substantially corresponds to the case of _p = −2 mm, which makes it possible to suppress a change in gain and phase at the resonance frequency in the pitching mode, thereby successfully preventing a decrease in the stability of the tracking control system.

FIG. 5 is a block diagram showing a configuration of an embodiment of an optical disk device according to the present invention. The optical disk device includes an optical disk 40 that rotates at a predetermined rotation speed.
An optical head 2 including an objective lens and the like for irradiating a light beam and receiving the reflected light, a tracking error detection circuit 4 for detecting a tracking error signal from the reflected light received by the optical head 2, and a tracking error detection circuit 4 An off-track correction circuit 5 that outputs a correction signal for correcting off-track based on the detected tracking error signal.

The optical disc apparatus further comprises a positioning mechanism 6 according to the second invention, having a positioner movable section 43 and a lens actuator movable section 42 for positioning the objective lens in accordance with the correction signal output from the off-track correction circuit 51. A signal detection circuit 3 for detecting a data signal from the reflected light received by the optical head 2, and a signal output circuit for performing a digital / analog conversion and other conversions on the data signal detected by the signal detection circuit 3 and outputting the data signal. ing.

In the optical disk apparatus having such a configuration, the optical head 2 is rotated by a predetermined number of rotations.
Is irradiated with a light beam, and the reflected light is received. The tracking error detection circuit 4 detects a tracking error signal from the reflected light received by the optical head 2, and the off-track correction circuit 5 corrects off-track based on the tracking error signal detected by the tracking error detection circuit 4. Is output. The positioning mechanism 6
The objective lens is positioned according to the correction signal output from the off-track correction circuit 51.

On the other hand, the signal detection circuit 3 detects a data signal from the reflected light received by the optical head 2, and the signal output circuit 7 converts the data signal detected by the signal detection circuit 3 into digital / analog conversion and other conversion. And output.
Other configurations and operations of the positioning mechanism are the same as those of the above-described embodiment of the positioning mechanism vibration suppressing method according to the present invention, and a description thereof will be omitted.

[0044]

According to the method for suppressing the vibration of the positioning mechanism and the optical disk apparatus according to the present invention, the coupled rotational vibration of the translational coarse movement mechanism and the two-axis lens translation drive mechanism in the optical disk apparatus is suppressed, and a stable and accurate rotation is achieved. Focus control can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view schematically showing a configuration of a positioning mechanism showing an embodiment of a method for suppressing vibration of the positioning mechanism according to the present invention.

FIG. 2 is a block diagram showing a control system of a positioning mechanism.

FIG. 3 is a graph showing a loop transfer function of a control system of a positioning mechanism.

[4] The distance h _p alter the is a graph showing the results of calculating the same loop transfer function as FIG.

FIG. 5 is a block diagram showing a configuration of a main part of an embodiment of an optical disk device according to the present invention.

FIG. 6 is a schematic diagram schematically showing a configuration of a positioning mechanism provided in a conventional optical disc device.

[Explanation of symbols]

2 the optical head 6 positioning mechanism 40 optical disc 42 lens actuator moving part (biaxial lens translation drive mechanism (moving part)) 43 positioner movable part (translational coarse feed mechanism (moving part)) f _p driving force G positioner translation coarse positioner centroid h _a centroid G of the center of gravity g lens actuator moving part of the movable part, between g, between the working position and the center of gravity G of the distance h _p driving force f _p of the disk surface and the vertical direction, the optical disc surface and vertical Distance γ _p Time constant ratio of phase compensation circuit of translation coarse movement mechanism control system ω _p0 Gain cross angular frequency of translation coarse movement mechanism control system ω _p1 Primary resonance frequency of translation coarse movement mechanism support system μ 2-axis lens translation drive mechanism Ratio of the mass of the motor and the mass of the translational coarse mechanism

Claims (2)

[Claims] 1. A biaxial lens translation drive mechanism for positioning an objective lens of an optical disc device in an optical axis direction and a radial direction of an optical disc, and a whole recording area in the radial direction of the optical disc which is equipped with the biaxial lens translation drive mechanism. And a translation coarse movement mechanism for moving the positioning mechanism, comprising: a position between a point of application of a driving force of the translation coarse movement mechanism and a center of gravity of the translation coarse movement mechanism; the distance in the vertical direction and h _p, between the center of gravity of the center of gravity and the translation coarse adjustment mechanism of the two-axis lens translation drive mechanism, the distance of the vertical h
_a, and the primary resonance frequency of the translational coarse motion mechanism support system is ω
and _p1, said the translation coarse feed mechanism control system gain cross angle frequency omega _p0, the time constant ratio of the phase compensation circuit of the translation coarse feed mechanism control system and gamma _p, the mass of the two-axis lens translation drive mechanism and Assuming that the mass ratio of the translational coarse movement mechanism is μ, the ratio of the h _p and the _ha is expressed by the following equation. By setting based on the value obtained by the above, the rotationally coupled vibration between the biaxial lens translation drive mechanism and the translation coarse movement mechanism, which is generated around an axis parallel to the tangential direction of the circumference of the optical disk, is suppressed. A method for suppressing vibration of a positioning mechanism. 2. A biaxial lens translation drive mechanism for positioning an objective lens of an optical disc device in an optical axis direction and a radial direction of the optical disc, and a whole recording area in the radial direction of the optical disc which is equipped with the biaxial lens translation drive mechanism. An optical disc device provided with a positioning mechanism having a translational coarse movement mechanism for moving the lens, wherein the translational coarse movement mechanism and the biaxial lens translation drive mechanism are:
Between the center of gravity of the translating coarse adjustment mechanism of the position and the translating coarse adjustment mechanism of action points of the driving force, the distance between the optical disc surface and vertical to the h _p, the translation and the center of gravity of the two-axis lens translation drive mechanism between the center of gravity of the coarse feed mechanism, the distance of the vertical direction h _a
And the primary resonance frequency of the translational coarse mechanism support system is ω _p1
And then, the translating the gain cross angular frequency of the coarse feed mechanism control system and omega _p0, the translation of the time constant ratio of the phase compensation circuit of the coarse feed mechanism control system and gamma _p, the mass and the said two-axis lens translation drive mechanism When the mass ratio of the translational coarse movement mechanism is μ,
The following equation Optical disc apparatus characterized by having the h _p and the h _a determined based on a value obtained by.