JP3820089B2 - Lens actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens actuator used in an apparatus (hereinafter referred to as an optical disk drive apparatus) that records / reproduces information on an optical storage medium having a plurality of different values corresponding to double speed.
[0002]
[Prior art]
In a lens actuator used for active control, it is necessary to employ a movable mechanism for reducing loss operation due to nonlinearity as much as possible. For this reason, a spring support structure is often used as a support structure for a lens actuator used in an optical disk drive device that requires high-precision control. For example, as described in Japanese Patent No. 2856176, four support springs (wires) are used. A structure in which the optical pickup is supported by the elastic member).
[0003]
On the other hand, due to the necessity of mounting a high NA objective lens as the recording density increases, it is necessary to reduce the optical axis tilt due to parasitic rotational motion during translational driving of focusing and tracking. However, in the structure described in Japanese Patent No. 2856176, in order to increase the displacement sensitivity in the focusing direction and the tracking direction, it is necessary to set the compliance (elastic coefficient) in both directions of the support spring low, and the size and weight are reduced. Since the outer dimension is restricted by the surface of the surface, the arrangement size of the support spring is limited, and therefore, in principle, there is a problem that the torsional rigidity in the radial direction is inevitably lowered.
[0004]
For this reason, the parasitic error of drive thrust during focusing or tracking translation shift, or the presence of a little asymmetry due to the assembly error of the support spring, causes parasitic rotational motion in the radial direction during translation drive. It often gives rise to production yields or costs.
[0005]
Until now, the optical axis tilt due to this parasitic rotational motion has been discussed mainly as a problem with respect to the DC (direct current) shift of the lens actuator in both radial and tangential axis tilts. This is a factor that firstly generates a parasitic moment as a working radius of thrust in a direction in which the DC shift amount is orthogonal as described above. Second, in the conventional optical disk drive device specifications, resonance around a tangential axis (hereinafter referred to as roll). This is because the frequency (called resonance) could be set higher than the maximum spindle rotation frequency of the optical disk drive device specification.
[0006]
[Problems to be solved by the invention]
However, due to the recent demand for high speed optical disk drive devices, the spindle rotation frequency during recording as well as during reproduction tends to exceed the roll resonance frequency of the conventional lens actuator. If these two frequencies match, the phenomenon described later occurs.
[0007]
The spectrum of the disk runout and eccentric component tends to be strong in the low frequency component in accordance with the principle of the natural world, and there may be a component having a large primary component, that is, a spindle rotation frequency component from the disc standard. That is, the surface blur and the eccentric component having the spindle rotation frequency component of this disk act as a forced feedback to the lens actuator for focusing and tracking, respectively, and act as an excitation force.
[0008]
As long as the excitation force acts as a theoretical pure translational thrust, no particular problem occurs. However, when the above-mentioned translational thrust is generated for focusing and tracking, it is inevitable that a DC shift occurs in the tracking and focusing directions that are in the orthogonal directions. As a result, this shift amount functions as a working radius, and the above-mentioned translational thrust generates a thrust parasitic moment, and this parasitic moment has the same frequency component as the roll resonance frequency due to the above-mentioned frequency coincidence. Will cause a literal rotational resonance.
[0009]
The AC (alternating current) radial direction tilt amount generated by the rotational resonance of the movable part is much higher than the conventional radial direction tilt amount caused by the DC shift, and modulates the amplitude of the tracking error signal and the RF signal. In addition to hindering stable recording / reproduction performance, servo errors may occur depending on the degree.
[0010]
Since these are literal resonances, the focusing and tracking parasitic moment canceling means used for the countermeasure against the parasitic inclination assuming only the DC shift is not effective.
[0011]
In summary, the synchronous signal excitation at the roll resonance frequency is an excitation condition that maximizes the sensitivity of the roll, that is, the radial gradient. Therefore, at the time of DC shift such as an inevitable cumulative deviation in the focus direction or a carriage tracking error in the tracking direction, there is an AC excitation force for disc surface deviation or eccentric tracking in a direction perpendicular to them. By adding, the radial inclination increases rapidly. As a result, the RF signal amplitude is modulated, increasing the error rate or increasing the possibility of occurrence of a servo error, which significantly hinders the speeding up.
[0012]
However, since the roll resonance frequency exists somewhere as long as the lens actuator is used, the above-described characteristics at the roll resonance frequency cannot be avoided. In the above description, the spring support structure has been described for the sake of convenience, but the problem is common to other structures, for example, an elastic hinge or a bearing. Therefore, it is necessary to set the roll resonance frequency while avoiding the spindle rotation frequency, and it is most desirable to set a roll resonance frequency that is high enough and necessary for the spindle rotation frequency of the maximum operating rotation speed.
[0013]
However, the rotational speed required for the optical disk drive within the operating time of the lens actuator used for the optical pickup is not always the same due to the above-mentioned demand for high speed, and also varies depending on the CD / DVD and its reproduction / recording. Since the spindle rotation speed control is performed, it is necessary to cope with this.
[0014]
From the principle of natural vibration, the roll resonance frequency is proportional to the square root of the torsion spring constant of the spring support structure and inversely proportional to the square root of the moment of inertia of the movable structure. This principle suggests that in order to sufficiently increase the roll resonance frequency, it is necessary to make the torsion spring constant much higher than before and / or make the moment of inertia very small. However, in general, in the spring support structure, if the support spring is set to low compliance in order to increase DC sensitivity, it is inevitable that the torsion spring constant depending on the support spring also becomes low. On the other hand, in other support structures that are not easily affected by this, since the support structure occupies the center of the movable structure, it is necessary to provide a pair of thrust generation sources on both sides for symmetry. Incurs an increase.
[0015]
Therefore, in any structure, there is a problem that it is often difficult to increase only the roll resonance frequency as necessary while satisfying other desirable characteristics.
[0016]
The present invention is directed to solving the problems of the prior art, and an object of the present invention is to provide a lens actuator that can reduce the influence of a roll resonance component that is harmful to speeding up.
[0017]
[Means for Solving the Problems]
In order to achieve this object, the lens actuator according to the present invention is used in an apparatus for recording / reproducing information having a plurality of values corresponding to different speeds for recording / reproducing of an optical storage medium, focusing and tracking. A lens actuator for driving an objective lens for control, comprising a holder that holds the objective lens, a wire spring that supports the holder from both sides of the holder, and a fixed block that fixes an end of the wire spring in the actuator, the spacing of the wire spring on each side of the holder, is installed to spread Oite a fixed position location in a fixed position location by remote fixed block in the holder, the lens optical axis and the cylindrical surface of the coaxial objective lens that it is curved to the outer bending shape of the fixing portion content vicinity of fixing the wire spring is fixed to the position, and the fixed block wire springs fixed blocks and And butterflies.
[0021]
According to the said structure, a torsion spring constant can be raised with a wire spring made low compliance, and a roll resonant frequency can be raised epoch-makingly .
[0022]
In addition, when the movable part of the lens actuator and the support structure are assembled, the movable part and the fixed block are positioned coaxially with the lens optical axis of the objective lens, and the support spring on the fixed block side in which the working radius from the coaxial line is increased ( Since the shape of the spring fixing part that restrains the wire spring or leaf spring is also a coaxial cylindrical surface, the support spring is effective even if relative rotational misalignment occurs in parts around the focusing direction (Y axis) during assembly. It is difficult to change the length, the asymmetry of compliance due to the difference in the lengths of the wire springs of both wings of the movable part can be prevented, and the occurrence of parasitic rotational motion around the tangential axis (X axis) can be reduced.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0024]
1 is a perspective view showing a front side of a lens actuator according to an embodiment of the present invention. FIG. 2 is a perspective view showing a rear side of the lens actuator of FIG. 1. 1 is a base, 2 is a base 1 facing each other. , 3 is an objective lens, 4 is a holder for holding the objective lens 3, 5 is a focusing coil, 6 is a tracking coil, and 7 is 4 in this example (at least 4 are sufficient). A wire spring which is a holder support spring, 8 is a printed circuit board for fixing a wire spring and feeding a coil fixed to both side portions of the holder 4, and 9 is a fixed block for fixing an end of the wire spring 7.
[0025]
The movable portion includes an objective lens 3 fixed and held on the holder 4, a focusing coil 5, a tracking coil 6, and a printed board 8. Further, the fixed portion is composed of a base 1 that also serves as a magnetic circuit rear yoke, a magnet 2, and a fixed block 9 fixed on the base 1.
[0026]
A fixed magnetic circuit is formed by the magnet 2 that is a magnetic flux generation source and the base 1 that is the back yoke, and the holder 4 has a thrust generation amount by four wire springs 7 installed so as to be symmetrical with each other. The objective lens 3 that is supported by the fixed block 9 so as to be elastically displaceable and is fixed to the holder 4 is focused according to the value of the current flowing through the focusing coil 5 and the tracking coil 6. And tracking thrust can be generated.
[0027]
The other end of the wire spring 7 whose one end is fixed to the printed circuit board 8 of the holder 4 passes through a damper material filling recess 10 formed at a distance from the inner wall of the fixed block 9 as shown in FIG. And soldered to a pattern of a flexible printed circuit board (not shown) provided on an arcuate surface portion 9a formed in the back wall of the fixed block 9 through the long hole 11 formed in communication with the recess of the fixed block 9 It is fixed by.
[0028]
However, the fixed pattern of the wire spring 7 may be formed on a printed circuit board, or may be a metal pattern directly formed on the fixed block 9 made of molded resin by a plating method as another example. Good. Moreover, as a damper material with which the hollow 10 is filled, for example, a silicone-based gel material is used.
[0029]
Further, a positioning slot 12 is formed on the fixed block 9. The positioning reference shaft 13 is inserted into the positioning long hole 12, and the fixing block 9 is positioned in the rotational direction around the focusing direction (Y axis) shown in FIG. The positioning reference shaft 13 may be formed on the base 1 or may be provided on an assembly work table in which the position of the base 1 is fixed with respect to the reference. A fixing operation is performed after the positioning. As a fixing method, a method such as adhesion between the base 1 and the fixing block 9 or screwing can be employed.
[0030]
In this embodiment, a metal wire spring is used as the wire spring 7 and soldering is used as a fixing method to serve as a power supply connection. An appropriate material may be selected and used depending on the material, and a resilient support spring such as a leaf spring may be used. Depending on the material and structure of the support spring, a bonding method or an insert molding method may be used. It is conceivable to appropriately select and adopt.
[0031]
FIG. 3 is a plan view of the lens actuator of the first embodiment. The holder 4 is supported by four wire springs 7 with respect to the fixed block 9, and the freedom between the holder 4 and the fixed block 9 in each wire spring 7 is shown. The spacing in the tracking direction in the straight portion 7 a is widened on the fixed position side of the fixed block 9 with respect to the fixed position side of the holder 4, and each wire spring 7 is bent outwardly in the vicinity of the fixed portion of the fixed block 9. ing.
[0032]
FIG. 4 is a plan view of the lens actuator of the second embodiment. The difference from the configuration of the first embodiment is the curved shape of the wire spring 7, and the other configurations are basically the same as those of the first embodiment. Therefore, corresponding members are denoted by the same reference numerals, and detailed description thereof is omitted. That is, in the second embodiment, the distance in the tracking direction at the free straight line portion 7 a between the holder 4 and the fixed block 9 in each wire spring 7 is set to be closer to the fixed position side of the fixed block 9 than the fixed position side of the holder 4. Is the same as in the first embodiment, but differs in that each wire spring 7 is bent in an inwardly bent manner in the vicinity of the fixed portion of the fixed block 9.
[0033]
In other words, in the second embodiment, the angle in the free straight line of the wire spring 7 is increased, and the curvature is inwardly bent to reduce the increase in compliance in the tracking direction and to increase the compliance in the radial rotation direction (roll rotation direction). ing.
[0034]
In the first embodiment, the angle in the free straight line of the wire spring 7 is smaller than that in the second embodiment, and the curve is outwardly bent. In this configuration, the effect of increasing the compliance in the roll rotation direction is less than in the second embodiment, but the same is achieved by increasing the size in the tracking direction (Z axis) shown in FIG. 1 at the fixed position of the wire spring 7 of the fixed block 9. The effect of can be obtained.
[0035]
As shown in FIG. 1, the relative rotation adjustment around the focusing direction (Y axis) in FIG. 1 is performed at the time of assembling and coupling the lens actuator, and the tangential axis (X Minimize parasitic rotational motion around the axis).
[0036]
In the adjustment, the monitoring target of the adjustment is not a parasitic radial tilt amount when a DC shift is given in the focusing direction as in the prior art, but a vibration having an AC spindle rotation frequency component in the focusing direction. Adjustment is performed to minimize the parasitic radial tilt amount at this time.
[0037]
With such a movable part configuration, the moment of inertia can be reduced by reducing the weight, and the torsion spring constant can be increased and the roll resonance frequency can be dramatically increased while keeping the wire spring in a low compliance state.
[0038]
Further, when the movable part of the lens actuator and the support structure are assembled, the movable part and the fixed block are positioned coaxially with the lens optical axis of the objective lens 3, and the working radius from the coaxial line is increased to support the fixed block 9 side. Since the surface of the spring fixing part that constrains the spring (wire spring or leaf spring) is also a coaxial cylindrical surface, it can be supported even when relative rotational deviation occurs in parts around the focusing direction (Y axis) during assembly. The effective spring length is difficult to change, the asymmetry of compliance due to the difference in the lengths of the wire springs 7 on both wings of the movable part can be prevented, and the occurrence of parasitic rotational motion around the tangential axis (X axis) can be reduced. Can do.
[0039]
From the viewpoint of improving workability and stability of the characteristics, and preventing the optical axis deviation of the lens, the relative position adjustment of the tracking direction component between the fixed block of the support structure and the fixed magnetic circuit as described above is performed. The rotation is adjusted around the axis that is coaxial or substantially coaxial with the optical axis, but only the position of the magnet 2 is adjusted, the relative position between the fixed block 9 of the support structure and the fixed magnetic circuit, or the movable part and the fixed magnetism. The relative translation position of the circuit may be adjusted.
[0040]
Here, by setting and adjusting the roll resonance frequency so as to be sufficiently high or take a different value for any of the spindle rotation frequencies that are the maximum recording / reproducing speed in the optical disc drive apparatus specification, the parasitic moment Prevents the occurrence of rotational resonance.
[0041]
5A and 5B are diagrams showing examples of frequency response characteristics of the lens actuator when the roll resonance frequency is not considered with respect to the spindle rotation frequency. In this example, a lens corresponding to a reproduction 32-times speed CAV (Constant Angular Velocity) method and a recording 8-times speed CLV (Constant Linear Velocity) method as a double-speed compatible numerical value expressed as 2,4 times the standard data transfer speed. Actuator.
[0042]
FIGS. 5A and 5B show the frequency response characteristics in the tracking direction at the focus neutral position and ± 0.3 mm (DC shift) among the characteristics of the lens actuator. FIG. 5A shows gain characteristics, and FIG. 5B shows phase characteristics. It can be seen that the tracking eigenvalue is present at about 50 Hz, and the roll resonance parasitic to this exists near about 60 Hz, but this alone does not appear to be a resonance that causes a problem in characteristics.
[0043]
However, in the above-described recording 8 × speed CLV system, the spindle rotation frequency in the OPC (Optimum Power Control) region is about 60 to 70 Hz, and a phenomenon occurs in which the roll resonance frequency is excited in the OPC region.
[0044]
FIG. 6 shows the roll resonance characteristics at the focus neutral position and ± 0.3 mm in terms of the roll tilt sensitivity (rad / m) per tracking displacement amplitude. Incidentally, the focus shift of 0.3 mm exemplifies a possible numerical value as a cumulative initial deviation from the disk surface to the objective lens. 1 (rad / m) corresponds to about 0.06 (degrees / mm). According to this, the roll tilt sensitivity at 60 to 70 Hz is about 5 (degrees / mm) or more, and if the eccentric primary component including the media, chuck or turntable is 0.1 mm, it is about 0.5 degrees or more. A tilt occurs in the objective lens of 1 degree or more at the maximum. This modulates the RF signal and track error signal, and in this example, the recording characteristics are significantly impaired. If this occurs in synchronization with the spindle rotation frequency during reproduction, a problem occurs in reproduction characteristics.
[0045]
FIGS. 7A and 7B show the characteristics of the lens actuator corresponding to the reproduction 32 × speed CAV method and the recording 8 × speed CLV method when this example is implemented, and the focus neutral position and the tracking direction at ± 0.3 mm. It is a figure which shows the frequency response characteristic of this lens actuator.
[0046]
The roll resonance frequency is considered with respect to the spindle rotation frequency, and the tracking eigenvalue is about 50 Hz which is substantially the same as the conventional example, but the roll resonance frequency parasitic on this is about 90 Hz. However, the roll resonance itself on the tracking response is hardly visible due to the relationship between the tracking active displacement and the ratio of the roll tilt sensitivity. However, it has been shown above that it cannot be guaranteed that it will not be a problem if it is not so conspicuous on the active characteristics of tracking.
[0047]
FIG. 8 shows the roll resonance characteristics at the focus neutral position and ± 0.3 mm in the same manner as FIG. 6, expressed as roll tilt sensitivity (rad / m) per tracking displacement amplitude. The roll tilt sensitivity at the peak position substantially equal to the roll resonance frequency is substantially the same as described above, but in this example, it is 60 to 70 Hz in the recording 8 × CLV OPC region and 120 Hz in the reproduction 32 × CAV method. Since it is considered that the peak positions are separated from each other, it can be seen that the roll tilt sensitivity in these frequency bands is kept low.
[0048]
Also, in an ordinary optical disk drive device, when an optical disk with extremely deteriorated mechanical characteristics is loaded, information can be recorded / reproduced at a spindle rotation speed that is the maximum recording / reproduction speed on this optical disk. When there is a possibility of affecting the quality or reliability of the optical disk drive or the optical disk and its signal, consideration is given so that recording / reproduction can be performed at a lower rotational speed. For that purpose, several types of low-speed compatible numerical values are also supported. The spindle rotational frequency corresponding to these double speeds is also set to a roll resonance frequency that avoids rotational resonance due to synchronous signal excitation as described above.
[0049]
In other words, the influence of the roll resonance component is reduced by setting the roll resonance frequency to an unused rotation frequency that avoids all the spindle rotation frequencies of the recording / reproducing speed corresponding to the double speed preset by the specifications in the optical disk drive device. In addition, the speed of the optical disk drive device can be increased.
[0050]
For this reason, when the roll resonance frequency cannot be set sufficiently high with respect to the spindle rotation frequency which is the maximum recording / reproducing speed, the specifications of the optical disk drive device as described above are used even in other support structures or conventional structures. The influence of the roll resonance component can be reduced by the design that sets and adjusts the roll resonance frequency while avoiding the spindle rotation frequency that is the maximum recording / reproducing speed.
[0051]
【The invention's effect】
As described above, according to the present invention, the torsional spring constant can be increased while the wire spring is kept in low compliance, and the roll resonance frequency can be dramatically increased, and the movable portion of the lens actuator and the support structure can be improved . A spring that constrains the support spring (wire spring or leaf spring, etc.) on the fixed block side when the movable part and fixed block are positioned coaxially with the lens optical axis of the objective lens during assembly and the working radius from the coaxial line is increased. since the fixing portion shaped surface is also a coaxial cylindrical surface, the focusing direction (Y-axis) the wire spring effective length be relative rotational deviation occurs in parts around hardly varies during assembly, the movable portion of the wings Compliance asymmetry due to different lengths of wire springs can be prevented, and the occurrence of parasitic rotational movement around the tangential axis (X axis) can be reduced. It can be an effect that it is possible to perform a high-speed optical disk drive device.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a front side of a lens actuator according to an embodiment of the present invention. FIG. 2 is a perspective view showing a rear side of the lens actuator according to an embodiment of the invention. FIG. 4 is a plan view of the lens actuator of the second example in the embodiment of the present invention. FIG. 5A is a frequency response in the tracking direction in the characteristics of the lens actuator. FIG. 6B is a graph showing phase characteristics. FIG. 6B is a graph showing roll tilt sensitivity (rad / m) per displacement amplitude of tracking the roll resonance characteristics at the focus neutral position and ± 0.3 mm. 7 (a) is a tracking method in the characteristics of a lens actuator for reproduction 32 × speed CAV method and recording 8 × speed CLV method. FIG. 8B is a graph showing the phase characteristics. FIG. 8 is a graph showing the roll tilt sensitivity (rad / m) per displacement amplitude of tracking the roll resonance characteristics at the focus neutral position and ± 0.3 mm. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base 2 Magnet 3 Objective lens 4 Holder 5 Focusing coil 6 Tracking coil 7 Wire spring 7a Free linear part 8 Printed circuit board 9 Fixed block 9a Arc surface part 10 Indentation 11 Slot

Claims (1)

A lens actuator for driving an objective lens for controlling focusing and tracking, which is used in an apparatus for recording / reproducing information having a plurality of numerical values corresponding to different speeds for recording / reproducing of an optical storage medium,
In a lens actuator comprising: a holder that holds the objective lens; a wire spring that supports the holder from both sides of the holder; and a fixing block that fixes an end of the wire spring.
The spacing of the line springs on both sides of the holder, and placed so as broaden Oite a fixed position location in a fixed position location by remote the fixed block in the holder, the lens optical axis and coaxial of said objective lens lens actuator, characterized in that it is curved to the outer bending shape in the the line spring is fixed in a fixed position of the fixed block, and the fixed portion component vicinity of the fixed block the line spring is a cylindrical surface.

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