JP3519501B2 - Optical head device and optical disk device including the optical head device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information storage / reproduction device,
For example, the present invention relates to an optical disk device used as an external storage device such as a computer, and more particularly, to an optical head device for irradiating an information recording medium with a light beam and extracting the light beam reflected by the information recording medium.

[0002]

2. Description of the Related Art Generally, an optical disc apparatus irradiates an optical disc with a stable wavelength light, that is, a laser beam, in order to write information to the optical disc as a recording medium and reproduce information from the optical disc. It has an optical head device for extracting the reflected light.

An optical head device is a laser element for generating a laser beam used for writing information on an optical disk and reproducing information from the optical disk, and a laser beam from the laser element on a surface of the optical disk at a predetermined beam spot. It has an objective lens for collecting the reflected laser beam reflected by the optical disk while condensing it in a size, and a photodetector for detecting the light from the optical disk taken out by the objective lens and converting it into an electric signal.

The objective lens is, for example,
It is movably supported in the first and second directions by an actuator, that is, a lens holder, which is movably supported in a first direction orthogonal to the recording surface of the optical disc and a second direction that traverses a track of the optical disc.

In this type of optical disk device, after the optical disk is set at a predetermined position, the optical disk is rotated at a predetermined speed, and firstly, the distance between the objective lens and the recording surface of the optical disk is controlled to be constant (focus). Locked). This operation is usually called focusing, and a servo loop for positioning the objective lens at a constant interval with respect to the recording surface of the optical disc can be obtained.

In a state where focusing is aligned, a predetermined current is supplied to the drive coil of the linear moving mechanism to move the objective lens, and the center of the light passing through the objective lens and the center of the track coincide with each other ( (Tracking is consistent)
Then, the center of the light passed through the objective lens and the innermost track of the optical disc are aligned with each other. Thereby, for example, an eccentric component peculiar to the track of the corresponding optical disc is detected. This operation is usually called tracking, and a servo loop for matching the center of the light passing through the center of the objective lens with the track is obtained.

Then, a predetermined current is supplied to the drive coil of the linear moving mechanism, and the movable portion, that is, the objective lens is moved to the vicinity of the target track (coarse seek, sometimes called access in a broad sense). Furthermore, the track jump of the objective lens due to the supply of a predetermined current to the tracking coil causes the center of the target track to coincide with the center of the laser beam that has passed through the objective lens (fine movement seek).

In the track thus aligned with the center of the laser beam, the header information of the optical disk is checked by the reflected laser beam from the track and the information is written to the designated target track, or the target track is written. Information is read from.

With regard to focusing, a focus error is detected by a known focus error detection method based on the light intensity of the reflected laser beam from the recording surface of the optical disc detected by the photodetector, and the servo loop of the servo loop is detected. The controlled variable is specified. That is, the correction amount corresponding to the focus error detected by the well-known focus error detection method is calculated, and the magnitude of the drive signal for driving the objective lens moving mechanism in order to move the objective lens corresponding to the correction amount is determined. Desired. The drive signal is phase-compensated according to a predetermined rule and then supplied to the objective lens moving mechanism.

Regarding tracking, similarly,
A track error is detected by a known track error detection method to define the control amount of the servo loop. Here, a correction amount corresponding to the track error detected by a known track error detection method is calculated, and the magnitude of a drive signal for driving the objective lens moving mechanism to move the objective lens in accordance with the correction amount. Is required. The drive signal is phase-compensated according to a predetermined rule and then supplied to the objective lens moving mechanism.

[0011]

By the way, the gain of the servo loop used for focusing and the gain of the servo loop used for tracking are determined when the optical disk device or the optical head device is assembled.
For example, after adjusting with a variable resistance element,
It is maintained at a substantially fixed value.

Therefore, when the surface wobbling or eccentricity of the optical disc mounted in the optical disc apparatus exceeds the standard size, or during recording of information data on the optical disc or from the optical disc. During reproduction, a large vibration or shock, that is, a disturbance is applied from the outside of the optical disk device, so that either or both focusing and tracking deviate from the servo loop.

The deviation of the focusing and tracking servo loops, for example, interrupts the recording of information on the optical disc and the reproduction of information from the optical disc, which causes a problem of reducing the processing speed. In addition, there is a problem that the objective lens and the optical disc may come into contact with each other, or the lens holder that holds the objective lens may come into contact with the structure of the optical head device. Further, when the shape of the optical disc on which the information has already been recorded changes with time, for example, the warp of the disc occurs, there is a problem that the information cannot be reproduced from the corresponding optical disc. An object of the present invention is to provide an optical disk device capable of reducing deviation of a servo loop in focusing and tracking.

[0014]

The present invention has the above-mentioned problems.
The light collecting means for collecting light on the recording surface of the recording medium, and the holding means for movably holding the light collecting means in the direction orthogonal to the recording surface and in the direction parallel to the recording surface. Means, holding means driving means for moving the holding means in at least one of a direction orthogonal to the recording surface and a direction parallel to the recording surface, and a detection means for detecting an acceleration applied to the holding means, The maximum acceleration detected from the detection results of the detection means is detected , and the maximum detected
After obtaining the maximum gain corresponding to the acceleration of the
Component due to surface deviation and eccentricity of the recording surface
Predict the components, with the maximum value of each predicted component as the upper limit,
The servo loop is controlled when the holding means driving means is controlled.
Ru der which provides an optical head and a control means for controlling the output of the in-and phase compensation of a center frequency said holding means driving means to change the.

Further, this invention provides an objective lens for converging light on the recording surface of the recording medium, the objective lens the recording surface perpendicular to the direction and the recording surface in a direction parallel and radially to A lens holding means for movably holding, a first lens driving means for moving the lens holding means in a direction orthogonal to the recording surface, and a lens holding means for moving in a direction parallel to the recording surface and in a radial direction. A second lens driving means, and a first difference signal for obtaining a difference between a distance between the objective lens and the recording surface and a distance required for collecting the light passing through the objective lens. Generating means,
Second difference signal generating means for obtaining the difference between the focal point of the light passing through the objective lens and the center of the guide groove formed on the recording surface, and output signals of the first difference signal generating means. And from each of the output signals of the second difference signal generating means,
An acceleration detecting means for detecting the acceleration provided to the lens holding means, and a result of detection by the acceleration detecting means.
Detected the maximum acceleration, the maximum acceleration detected
After finding the corresponding maximum gain,
Predicts the component caused by the eccentricity of the recording surface
The maximum value of each predicted component as the upper limit,
Gain of the servo loop when controlling the stage drive means and
By changing the center frequency of the phase compensation,
Moving means or at least one of the second lens driving means
An optical head device having a control means for controlling the other output . Furthermore, the invention relates to a recording
At least an objective lens that collects light on the recording surface of the medium is used.
Move in the direction perpendicular to the recording surface or parallel to the recording surface
The distance between the objective lens and the recording surface and the objective lens
Difference from the distance required to collect the light passing through the lens.
And the condensing point of the light passing through the objective lens and the recording surface
The difference from the center of the guide groove
Calculate the velocity and calculate the maximum acceleration
Maximum gain detected and corresponding to the maximum acceleration detected
Then, the component due to the blurring of the recording surface and the recording surface
Predict the components due to eccentricity, and predict the maximum value of each component
Servo for controlling the position of the objective lens with the upper limit of
Change the center frequency of the loop gain and phase compensation
To determine the positional relationship between the objective lens and the recording surface of the recording medium.
The position of the objective lens characterized by being positioned within the range of
The present invention provides a storage control method .

[0016]

According to the present invention, the maximum acceleration of the accelerations applied to the holding means for movably holding the condensing means detected by the detecting means is detected, and the maximum detected acceleration is detected.
After obtaining the maximum gain corresponding to the acceleration,
Components due to blurring and components due to eccentricity of the recording surface
Minutes, predicting the maximum value of each component as the upper limit,
The gain of the servo loop when controlling the holding means driving means
Since the output of the holding means driving means for controlling the holding means by changing the center frequency of the phase and phase compensation is controlled,
The light from the condensing means held by the holding means is accurately focused on the recording surface of the recording medium.

[0017]

Further, according to the present invention, the acceleration provided to the lens holding means for holding the objective lens is such that the light passing through the objective lens and the space between the objective lens and the recording surface of the recording medium are condensed. A first difference signal generating means for obtaining a difference with a distance necessary for the purpose, and a first difference signal obtaining means for obtaining a difference between a condensing point of light passing through the objective lens and a center of a guide groove formed on the recording surface of the recording medium. Corresponding to the maximum acceleration of the detected accelerations obtained from each of the two difference signal generating means.
From the required maximum gain,
Minute and the component due to the eccentricity of the recording surface are predicted, and each predicted
The holding means driving means is controlled with the maximum value of the component as the upper limit.
Center frequency of servo loop gain and phase compensation
By changing the number, the first lens driving means or the second lens
The output of at least one of the drive units is reduced.

[0019]

[0020]

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1 and FIG. 2, the optical head device 2 has a recording surface of an optical disc D as a recording medium.
The objective lens 10 and the objective lens 10 which irradiate a laser beam (light) from a semiconductor laser element described later and take out the laser beam reflected by the recording surface of the optical disc D.
A lens actuator 12 that holds the lens actuator 12 so that the lens actuator 12 can move in the direction opposite to the recording surface of the optical disk D, and a slide base 14 that holds the lens actuator 12 so that the lens actuator 12 can move in the radial direction of the optical disk. 2 (a)
Is a schematic plan view of the optical head device 2 and FIG.
FIG. 2B is a schematic sectional view of the optical head device 2.

The lens actuator 12 includes a mirror 12a for guiding a laser beam from a semiconductor laser, which will be described later, to the objective lens 10, a focus coil 12b for moving the objective lens 10 in a method orthogonal to the recording surface of the optical disc D, and It has a tracking coil 12c for moving the objective lens 10 along the recording surface of the optical disc D in the radial direction of the optical disc D.

At a predetermined position of the lens actuator 12, first to third acceleration sensors for detecting accelerations acting on the lens actuator 12, that is, the objective lens 10 in the three axial directions of the X-axis, the Y-axis and the Z-axis. 12
x, 12y and 12z are arranged. The first
The acceleration sensor 12x of the optical disc D crosses a track previously formed on the recording surface of the optical disc D (radial direction).
That is, it is used to detect the acceleration in the tracking direction. In addition, the second acceleration sensor 12y detects the acceleration in the tangential direction of the track and uses the third acceleration sensor 1y.
2z is used to detect the acceleration in the direction opposite to the recording surface of the optical disc D, that is, in the focusing direction.

On a side surface of the slide base 14 at a predetermined position and parallel to the radial direction of the optical disk D, leg portions 14a and 14 used for connection with a guide shaft described later are provided.
b is formed integrally with the slide base 14. The leg portions 14a and 14b are provided with a pair of drive coils 16a and 16b that generate a driving force for moving the slide base 14 in a desired direction in response to a magnetic field provided by a magnetic force generator described later, that is, a fixed magnet. It is arranged. That is, the drive coils 16a and 16b
Composes a linear motor 16 for linearly moving the slide base 14 together with a magnetic force generator described later and a guide shaft described later.

A plurality of bearings 18 are arranged at predetermined positions of the legs 14a and 14b so as to be rollable with respect to a guide shaft, which will be described later, and provide friction between the guide shaft and the guide shaft at a predetermined value or less. ing. As shown in FIG. 2, the bearing 18 has legs 14a so that its rolling surface is orthogonal to the normal line of the guide rail.
And 14b.

At the position where the rolling surfaces of the respective bearings 18 come into contact, the slide base 1 is inserted through the bearings 18.
A guide shaft 20 that supports the movable body 4 in the X-axis direction.
a and 20b are arranged.

The slide base 14 has a drive coil 16a.
And 16b through the guide shafts 20a and 20b by the propulsive force generated by the current supplied to
It is movably held parallel to the radial direction of the optical disc. The guide shafts 20a and 20b are arranged so as to be parallel to each other, and the surface including the axis of each shaft and the recording surface of the optical disk are parallel to each other.

As shown in FIG. 2, the guide shaft 20a is provided at a predetermined position on the side of the legs 14a and 14b opposite to the side on which the lens actuator 12 is held.
Position sensors 22a and 22b for detecting the position of the slide base 14 that moves 20 and 20b, that is, the position of the objective lens 10 are arranged. Therefore, the position sensors 22a and 22b are moved together with the slide base 14 in the radial direction of the optical disc when the slide base 14 is moved.

Paths along which the position sensors 22a and 22b are moved, that is, parallel to the guide shafts 20a and 20b and parallel to the recording surface of the optical disc, and near the position sensors 22a and 22b,
Linear scales 24a and 24b indicating the positions of the position sensors 22a and 22b are arranged. That is, the position sensor 22a and the linear scale 24a, and the position sensor 22b and the linear scale 24b are
Position detectors 25a and 25b for detecting the current positions of the legs 14a and 14b are formed, respectively.

A surface including the axes of the guide shafts 20a and 20b, which are the respective shafts 20a and 20b.
0b and inside the drive coils 16a and 16b, auxiliary yokes 26a and 2 used as a part of a magnetic circuit of the linear motor 16 which has already been described later.
6b is arranged.

At a position facing the auxiliary yokes 26a and 26b with the drive coils 16a and 16b sandwiched therebetween, a yoke 27a forming a magnetic circuit described later by being magnetically connected to the auxiliary yokes 26a and 26b, respectively.
And 27b are arranged.

Between the yokes 27a and 27b and the respective drive coils 16a and 16b, a magnetic force generating device that functions to change the magnetic force generated by the current supplied to the respective coils 16a and 16b into propulsion force, that is, A pair of fixed magnets 28a and 28b are arranged.

The magnets 28a and 28b are in close contact with the yokes 27a and 27b. The yoke 27a and the auxiliary yoke 26a, and the yoke 27b and the auxiliary yoke 26b are respectively connected to the connecting member 2
Connected via 9a, 29b, 29c and 29d,
It forms a closed circuit as a magnetic circuit.

A semiconductor laser device fixed via a fixing member (not shown) at a position where the laser beam can be irradiated toward the mirror 12a of the lens actuator 12 so that the direction of the polarization plane of the laser beam coincides with a predetermined direction. 30 (hereinafter referred to as a laser element) is arranged. In addition,
The laser element 30 and the optical element described later are, for example,
The slide base 14 is arranged at a predetermined position of a housing portion (not shown) of the optical head device 2 in an area outside the movable area where the slide base 14 can move. Further, in this embodiment, the direction of the plane of polarization of the laser beam emitted from the laser element 30 is, for example, the X-axis direction.

Lens actuator 12 and laser element 30
Between the collimating lens 3 and the collimating lens 3 for shaping the cross-sectional shape of the laser beam emitted from the laser 30 into a predetermined size.
2 and a beam splitter 34 that guides the laser beam that has passed through the collimator lens 32 to the recording surface of the optical disc D and separates the reflected laser beam reflected by the recording surface from the light that is directed to the optical disc D.

In the direction in which the reflected laser beam separated by the beam splitter 34 is guided, the reflected laser beam separated by the beam splitter 34 is reflected by the lens unit 36 which gives predetermined optical characteristics and the recording surface. A photodetector 38 is arranged which converts the reflected laser beam into an electrical signal corresponding to the light intensity.

Referring to FIG. 3, the optical head device 2 shown in FIGS. 1 and 2 is an information recording / reproducing device, that is, a main controller of the optical disc device 100, that is, a CPU 1.
Controlled by 02.

In the CPU 102, an initial operation program for operating the optical disk device 100 and predetermined initial data, and the objective lens 10 of the optical head device 2 are transmitted via the control bus 106.
A memory 104 storing a control program and the like for locating the vehicle at a predetermined position is connected.

The CPU 102 also has a control bus 106.
Via a laser control circuit 110 for activating the laser element 30 and changing the light intensity of the laser beam emitted from the laser element 30 according to the data to be recorded, and a linear motor 16 for moving the linear motor 16 to a predetermined position. The motor control circuit 112 and the video signal processing circuit 114 that performs signal processing for reproducing information recorded on the optical disc D based on the reflected laser beam from the recording surface of the optical disc D detected by the photodetector 38. Are connected.

The CPU 102 further includes a control bus 10
A predetermined current is supplied to the focus coil 12b via the objective lens 1 based on the reflected light from the recording surface of the optical disc detected by the photodetector 38.
The reflected light from the recording surface of the optical disc detected by the photodetector 38 and the focus control circuit 116 that moves the objective lens 10 in order to match the distance between 0 and the recording surface of the optical disc with the focal length of the objective lens 10. A tracking control circuit 118 for matching the center of the light passed through the objective lens 10 with the track center of the track of the optical disc is connected. The focus control circuit 116 and the control bus 106, and the tracking control circuit 118 and the control bus 106 are connected to each other via an A / D converter 132.

The CPU 102 also has a control bus 106.
Based on the outputs from the position detectors 25a and 25b, the position of the slide base 14, that is, the objective lens 10 and the track (pre-groove) formed on the recording surface of the optical disc, and the slide base 14 (that is, the objective lens 10). ) Is moved, that is, the position / speed calculation circuit 120 for calculating the moving speed of the linear motor 16 is connected.

On the other hand, a motor 4 for rotating the optical disc D
Is rotated at a predetermined speed by the motor drive current supplied from the motor drive circuit 122 under the control of the CPU 102.

Further, the linear motor control circuit 112 includes
The motor drive amount converted from a digital signal to an analog signal by the D / A converter 134 is input via the CPU 102, and the slide base 14 for moving the position of the linear motor 16, that is, the position of the objective lens 10 to a predetermined position. Movement is controlled.

Next, the focus control circuit and the tracking control circuit will be described in detail. As shown in FIG. 4, the focus control circuit 116 includes a focus error detector 51, a gain controller 52, a phase compensation circuit 53, a lens actuator drive circuit 54, a focus coil 55, and a surface shake acceleration detector 56 together. You can replace the one you did. In addition, CPU
102 also functions as a selector 102a that compares the acceleration in a normal state with the magnitude of acceleration due to disturbance and switches the data table read from the memory 104 in an algorithm described later with reference to FIG.

That is, the focus error detector 51 detects the focus error described later with reference to FIGS. 6 (a) to 6 (c), and the surface shake amount of the optical disc D, that is, the amount to move the objective lens 10 is focused. It is detected as an error, is amplified to a predetermined level by the gain controller 52, and a correction amount for correcting the position of the lens actuator 12 (objective lens 10) corresponding to the displacement is obtained via the phase compensation circuit 53. .
Subsequently, the lens actuator drive circuit 54 obtains the current value to be supplied to the focus coil 55, and the lens actuator 12 and the objective lens 10 are set to the optical disc D.
Is moved by a predetermined amount in the direction orthogonal to the recording surface of, ie, the Z-axis direction.

At this time, the disturbance represented by, for example, impact or vibration is detected as the surface vibration acceleration by the surface vibration acceleration detector 56. It should be noted that the surface wobbling acceleration detector 56 is included in the lens actuator 12 of the optical head device 2 shown in FIG.
Of at least one of each of the acceleration sensors 12x, 12y, and 12z of the above is used to determine that a predetermined level has been exceeded.

The impact or vibration detected by the surface wobbling acceleration detector 56, that is, the disturbance acceleration is input to the CPU 102 shown in FIG. 3 and predetermined based on a disturbance compensation routine defined according to an algorithm described later with reference to FIG. Is converted into a compensation amount of 1 and is fed back to the gain controller 52 and the phase compensation circuit 53. Even when the disturbance acceleration is detected, the gain controller 52 and the phase compensation circuit are switched by switching the selector 102a shown in FIG. 4 only when the magnitude of the disturbance acceleration exceeds a predetermined level. Feedback to 53.

More specifically, the disturbance acceleration detected by the surface wobbling acceleration detector 56 is converted into a digital signal by the A / D converter 132 and input to the CPU 102 at relatively short sampling times. CPU
Reference numeral 102 determines whether or not the magnitude of the disturbance acceleration input via the A / D converter 132 exceeds a predetermined level, and when the magnitude of the disturbance acceleration exceeds the predetermined level, the selector 102a is operated. The gain corresponding to the switched and input disturbance acceleration is read from the memory 104, and the gains of the gain controller 52 and the phase compensation circuit 53 are changed to predetermined values. Here, for example, when the magnitude of the disturbance acceleration becomes larger than a predetermined level, the gain of the servo loop is increased.

By the way, since it is necessary to stabilize the loop for controlling the movement of the objective lens 10 by changing the gain, when the gain of the gain controller 52 is changed by the CPU 102, the phase compensation circuit. It becomes necessary to change the center frequency of the phase compensation by 53 in association with the change of the gain.

Therefore, when the gain of the gain controller 52 is changed, the center frequency of the phase compensation corresponding to the input disturbance acceleration is read from the memory 104 by the CPU 102 and the phase by the phase compensation circuit 53 is read. The center frequency of compensation is changed. The center frequency of phase compensation is, for example, 1.5 kHz (hereinafter,
[indicated as [kHz]), 3 [kHz] and 4.5 [kHz]
z] is selected based on an algorithm for obtaining an acceleration, which will be described later with reference to FIG.

As shown in FIG. 5, the tracking control circuit 118 includes a track error detector 61, a gain controller 62, a phase compensation circuit 63, a lens actuator drive circuit 64, a track coil 65, an eccentric acceleration detector 66, and a linear acceleration detector. A motor drive circuit 67, a linear motor 68,
Also, the position detector 69 can be replaced with a group. Note that the CPU 102, like the focus control circuit shown in FIG. 4, compares the acceleration in the normal state with the magnitude of the acceleration due to the disturbance, and creates a data table read from the memory 104 in an algorithm described later with reference to FIG. It also functions as a selector 102a for switching.

That is, the track error detector 61 detects a track error, which will be described later with reference to FIG. 6 (b), and the track reciprocates in the radial direction of the optical disk D in accordance with the eccentricity of the center hole of the optical disk D. That is, the amount by which the objective lens 10 should be moved in the radial direction of the optical disc D is detected as a track error, is amplified to a predetermined level by the gain controller 62, and is passed through the phase compensation circuit 63 to the lens actuator corresponding to the eccentricity. A correction amount for correcting the position of 12 (objective lens 10) is obtained.

Subsequently, the lens actuator drive circuit 64
And the driving coil 16a by the objective lens driving circuit 65
And 16b and the current value to be supplied to the focus coil 55 are obtained, and the lens actuator 12 and the objective lens 10 are moved by a predetermined amount in the direction orthogonal to the recording surface of the optical disc D, that is, the X-axis direction. Further, based on the track error detected by the track error detector 61, a control amount for driving the linear motor is defined and supplied to the linear motor drive circuit 67. As a result, the linear motor 68 is driven to move the objective lens 10 to a predetermined position. In this case, the speed of the linear motor 68 is monitored via the speed detector 69, so that the objective lens 10 by the linear motor 68 is
The amount of movement is fed back.

Separately, for example, a disturbance represented by shock or vibration is detected by the eccentric acceleration detector 66 as eccentric acceleration. The impact or vibration detected by the eccentric acceleration detector 66, that is, the disturbance acceleration is input to the CPU 102 shown in FIG. 3, and a predetermined compensation amount is calculated based on a disturbance compensation routine defined according to an algorithm described later with reference to FIG. And is fed back to the gain controller 62 and the phase compensation circuit 63. Even when the disturbance acceleration is detected, the selector 102a is switched and fed back to the gain controller 62 and the phase compensation circuit 63 only when the magnitude of the disturbance acceleration exceeds a predetermined level.

More specifically, the disturbance acceleration detected by the eccentric acceleration detector 66 is converted into a digital signal by the A / D converter 132 and input to the CPU 102 at relatively short sampling times. CPU1
02 determines whether or not the magnitude of the disturbance acceleration input via the A / D converter 132 exceeds a predetermined level, and when the magnitude of the disturbance acceleration exceeds the predetermined level, the selector 02 102a is switched, the gain corresponding to the input disturbance acceleration is read from the memory 104, and the gain of the gain controller 62 is changed to a predetermined value.

By the way, since it is necessary to stabilize the loop for controlling the movement of the objective lens 10 by changing the gain, when the gain of the gain controller 62 is changed by the CPU 102, the phase compensation circuit. Unless the center frequency of the phase compensation by 63 is linked and changed, the stability of the loop needs to be reduced. From this, when the gain of the gain controller 62 is changed, the central frequency of the phase compensation corresponding to the input disturbance acceleration is stored in the memory 10 by the CPU 102.
4, the center frequency of the phase compensation by the phase compensation circuit 63 is changed.

Next, the method for detecting the focus error and the track error will be described in detail. FIG. 6 shows an example of the positional relationship between the reflected light from the recording surface of the optical disc that has passed through the lens unit 36 and the photodetector 38, and the output signal from the photodetector 38.

The lens unit 36 is provided with a focusing lens 36a for imparting a predetermined focusing property to the reflected light from the optical disc separated from the light traveling from the laser element 30 to the optical disc by the beam splitter 34, and for the astigmatism method, for example. , And a cylindrical lens 36b for giving astigmatism to the light passing through the focusing lens 36a.

Therefore, the light passing through the cylindrical lens 36b is directed to either one of the first and second directions which are orthogonal to each other in the direction in which the light travels, that is, in the plane orthogonal to the optical axis of the system. , First, then equally focused in the first and second directions,
Further, it is focused in the remaining direction (see FIG. 6 (a)).

The photodetector 38 is, for example, a four-divided photodetector having first to fourth detection areas 38a to 38d, and as shown in FIG. 6B, the first and third photodetectors. After the outputs of the detection areas 38a and 38c and the outputs of the second and fourth detection areas 38b and 38d are added to each other, the "difference" between the addition outputs of the respective detection areas 38a and 38c Depending on the cross-sectional shape of the emitted light, a signal having “0” or “positive” and “negative” polarities as shown in FIG. 6C is output. Note that, for example, the first and third detection areas 38a
And the output difference of 38c or the output difference of the second and fourth detection areas 38b and 38d (either one is used depending on the pre-groove of the photodetector 38 and the recording surface of the optical disc, that is, the direction of the track). By doing so, it is possible to detect a decrease in the light intensity corresponding to the shadow of the track, and therefore the shift between the track center and the center of the light passed through the lens unit 36 is required.

Therefore, the output from the photodetector 38 is "0".
At this position, the focus of the objective lens 10 and the recording surface of the optical disc are aligned. When the output from the photodetector 38 is either “positive” or “negative”, the focus coil driving unit 124 moves the focus coil to the focus coil based on the movement amount of the objective lens 10 obtained by the focus control circuit 116. 12b is supplied with a predetermined drive current,
The objective lens 10 is moved so that the output from the photodetector 38 becomes “0”.

Further, based on the correction amount calculated by the tracking control circuit 118, the track coil driving unit 1
A predetermined drive current is supplied from 26 to the tracking coil 12c, and the center of the laser beam that has passed through the objective lens 10 is aligned with the center of the target track.

Next, the characteristics of the operation of the optical head device 2 shown in FIGS. 1 to 6 will be described. The laser beam from the laser element 30 is guided to the objective lens 10 via the collimator lens 32, the beam splitter 34, and the mirror 12a, and is focused on the recording surface of the optical disc D.

The reflected laser beam reflected by the recording surface of the optical disc D is returned to the objective lens 10 and then guided by the mirror 12a to the beam splitter 34. The beam is directed from the laser element 30 to the optical disc through the beam splitter 34. After being separated from, the light is passed through the focusing lens 36a and the cylindrical lens 36b of the lens unit 36 in order, and an image is formed on the photodetector 38.

Each detection area 38a-38d of the photodetector 38
Output from the focus control circuit 116, the tracking control circuit 118, and the video signal control circuit 114.
Supplied.

Therefore, firstly, the focus control circuit 11
By the focus control signal from 6 to the focus coil 12b, the distance between the objective lens 10 and the recording surface of the optical disc is aligned with the distance at which the laser beam passing through the objective lens 10 is converged (focus lock). It Secondly, the movement of the linear motor according to the linear motor control signal from the linear motor control circuit 112 moves the lens actuator 12, that is, the objective lens 10 to a position facing the target track or in the vicinity of the target track. Thirdly, the tracking coil 12c of the lens actuator 12 is energized by the track coil driving unit 126 based on the tracking signal from the tracking control circuit 118, and the target track and the objective lens 10 are
The center of the laser beam passed through is aligned. That is, tracking is ensured for the target track.

After this, each detection area 38 of the photodetector 38
The sum signal of the outputs of a to 38d is supplied to the video signal control circuit 114 and reproduced as a video signal.
By the way, as already described in the section of the prior art, the gain of the focusing and tracking servo loop is substantially adjusted after the optical disk device or the optical head device is assembled, for example, after being adjusted by a variable resistance element or the like. Maintained at a fixed value. From this, when the surface wobbling or eccentricity of the optical disc D mounted on the optical disc apparatus 100 exceeds the standard size, or while recording information data on the optical disc D or from the optical disc D, While playing data,
When a large vibration or shock, that is, a disturbance is applied from the outside, either or both of focusing and tracking may deviate from the servo loop.

Next, focus control and tracking control by the focus control circuit and tracking control circuit shown in FIGS. 4 and 5 and compensation of the servo loop when a disturbance occurs will be described.

As shown in FIGS. 1 and 2, the lens actuator 12 includes an X-axis acting on the objective lens 10,
Since the first to third acceleration sensors 12x, 12y, and 12z that detect the respective accelerations in the three Y-axis and Z-axis directions are arranged, focusing between the objective lens 10 and the optical disk D can be performed. In addition to the state and tracking state, 3 acting on the objective lens 10
Axial acceleration can be detected.

The outputs of the respective acceleration sensors 12x, 12y and 12z are input to the surface shake acceleration detector 56 and the eccentric acceleration detector 66 in the focus control circuit and the tracking control circuit shown in FIGS. Each is used. It is needless to say that the surface wobbling acceleration detector 56 and the eccentric acceleration detector 66 are usually used to detect the amount of surface wobbling or eccentricity of the optical disc D mounted in the optical disc device 100. Absent.

Hereinafter, the first to third acceleration sensors 12 will be described.
A method of detecting the acceleration by using the signals entering the servo circuit from the outputs of x, 12y and 12z will be described.
FIG. 7 is a chart showing an algorithm for obtaining acceleration. Referring to FIG. 7, the input signals to the focus error detector 51 and the track error detector 61 shown in FIGS.

[0072]

[Equation 1] The original acceleration signal is replaced by passing through the filter having the transfer function shown by. Next, the original acceleration signal calculated by equation (1) is

[0073]

[Equation 2] Fourier transform is performed as a quantity indicated by. here,
Accelerations α _{1 to} α _{i at} a certain moment are obtained from the spectrum obtained by the Fourier transform according to the equation (2). It should be noted that the accelerations α _{1 to} α _i obtained here indicate a state in which the surface runout acceleration, the eccentric acceleration, and the acceleration due to the disturbance are combined. Further, as a result of the Fourier transform by the equation (2), each of the instantaneous accelerations is, for example, −40 decibel / decat (hereinafter, [dB / d
It is recognized that the frequency response can be accommodated within a Bode plot having a slope (denoted as c]). next,
The maximum acceleration α _max is extracted from the instantaneous acceleration obtained by the equation (2),

[0074]

[Equation 3] Then, the maximum gain g _max is calculated.

The maximum gain g thus obtained
Based on _max , the maximum values of surface wobbling acceleration and eccentric acceleration that may occur during normal operation are predicted. From this, stable servo is possible by changing the gain of the servo loop with the predicted maximum values of surface runout acceleration and eccentric acceleration as the upper limit, and changing the center frequency of the phase compensation of the phase compensation circuit. Become. The center frequency of the servo loop gain and phase compensation is
It is stored in the memory 104 in advance.

Therefore, the maximum acceleration is obtained from the input signals to the focus error detector 51 and the track error detector 61, and the gain of the servo loop and the gain of the servo loop are determined by referring to the control amount stored in the memory 104. By changing the center frequency of the phase compensation corresponding to the change, the stability of the servo loop is improved.

Next, the first to third acceleration sensors 12
Each of x, 12y and 12z or one of them
From the two outputs, a disturbance having an acceleration greater than the acceleration during normal operation described using equations (1) to (3),
That is, the disturbance acceleration provided by vibration or shock will be described.

Based on the acceleration calculated through the surface wobbling acceleration detector 56 and the eccentric acceleration detector 66 shown in FIGS. 4 and 5, the optimum gain corresponding to the acceleration is read from the reference table of the memory 104. . Where C
The PU 102 outputs a resistance select signal corresponding to the optimum gain read from the memory 104. Further, the gain intersection frequency, that is, the center frequency of phase compensation and the resistance select signal are set based on the read optimum gain.

Next, in relation to the detected disturbance acceleration,
A method of changing the gain of the servo loop will be described. Referring to FIG. 8, firstly, based on the initial data stored in the memory 104, the objective lens 10
That is, the lens actuator 12 is moved at a normal acceleration. In this case, the gain of the servo loop and the center frequency of phase compensation are also set according to the initial data.

Subsequently, the first to third acceleration sensors 1
The outputs of 2x, 12y, and 12z are input to the surface wobbling acceleration detector 56 and the eccentric acceleration detector 66, and the surface wobbling acceleration and the eccentric acceleration are detected (STP1).

The required acceleration to be provided to the objective lens 10, that is, the lens actuator 12 is calculated based on each of the surface wobbling acceleration and the eccentric acceleration detected in step STP1 (STP2).

Based on the required acceleration calculated in step STP2, the optimum gain corresponding to the required acceleration is read from the reference table of the memory 104 (STP.
3). Then, the CPU 102 determines whether or not the gain and the center frequency of the phase compensation set based on the initial data are optimum (STP4).

If it is determined in step STP4 that the center frequency of the gain and phase compensation set based on the initial data is the optimum value, step ST
P1 to P4 are repeated to maintain a stable servo loop (STP4-Y). On the other hand, step ST
In P4, when it is determined that the center frequencies of the gain and the phase compensation set based on the initial data deviate from the optimum values (STP4-N), the CPU 10
By the control of No. 2, according to the algorithm described in FIG. 7, the surface wobbling acceleration detector 56 and the eccentric acceleration detector 6
Based on the acceleration calculated via 6, the optimum gain corresponding to the acceleration is read from the reference table of the memory 104, and the resistance value of the gain controller corresponding to the optimum gain is selected via the CPU 102 (STP5). .

Subsequently, the CPU 102 switches the resistance value of the multiplexer described later (STP6).
In addition, following steps STP5 and 6, the CPU
By the control of 102, the resistance value for changing the center frequency of the phase compensation corresponding to the resistance value of the gain controller changed in step STP5 is read from the memory 104 (STP7). Subsequently, the CPU 102 switches the resistance value of the multiplexer described later (ST
P8).

When the gain of the servo loop and the center frequency of the phase compensation are changed by steps STP4-N to STP8, the changed control data is stored in the memory 104 as the control data on the corresponding acceleration ( STP9). As a result, the gain data of the servo loop and the center frequency data of the phase compensation for the disturbance that may be repeated continuously or randomly are accumulated, and even when the disturbance occurs, the
The control data can be read, and the time required until the servo loop is stabilized can be shortened.

Next, an example of a gain controller and a phase compensation circuit which can be used in the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5 will be described.
FIG. 9 shows an example of the gain controller used in the embodiment of the present invention.

Referring to FIG. 9, the gain controller incorporated in the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5 has a plurality of resistance elements R11, R12, R13 ,. Are connected to the input terminals and function as switching elements for changing the magnification under the control of the CPU 102. A plurality of first multiplexers 151 connected to the input side of the first multiplexer 151 and having a predetermined resistance value. Resistance element R2
For each acceleration detected by the surface wobbling acceleration detector 56 and the eccentric acceleration detector 66 in the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5 via 1, R22, R23 ,. A second multiplexer 152 which functions as a switching element for giving a predetermined gain under the control of the CPU 102;
It has an amplifier 153 for amplifying the output of the second multiplexer 152 by a predetermined magnification.

FIG. 10 is a graph showing the relationship between the gain of the servo loop switched by the gain controller shown in FIG. 9 and the center frequency of phase compensation. As shown in FIG. 10, by switching the combination of the resistance elements of the first and second multiplexers of the gain controller shown in FIG. 9, -40 [dB / dB shown in FIG.
The center frequency of the phase compensation in the Bode line having a slope of dc] is 3 [kHz] as the reference level,
For example, it can be changed within a range of ± 1.5 [kHz].

FIG. 11 is a circuit diagram showing an example of a phase compensation circuit incorporated in the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5. Referring to FIG. 11, the phase compensation circuit has a plurality of resistance elements R31, R32, R33, ... Having respective predetermined resistance values connected to the input terminals thereof, and is for changing the magnification under the control of the CPU 102. A first multiplexer 161, which functions as a switching element, and a plurality of resistance elements R41, R42, R43, ... Which are connected to the input side of the first multiplexer 161 and have a predetermined resistance value under the control of the CPU 102.
The output from the gain controller shown in FIG. 9 via the second multiplexer 162 functioning as a switching element for changing the constant, and the first and second multiplexers 162 and 162 are waveform-shaped. It has an amplifier 163 for amplifying the generated signal by a predetermined magnification.

According to the phase compensation circuit shown in FIG. 11, the center frequency of the phase compensation shown in the Bode diagram shown in FIG. 10, that is, the center frequency defined by the intercept of the frequency axis by the gain, for example, the reference frequency 3 as a level
It can be extracted at [kHz] and ± 1.5 [kHz].

FIG. 12 is a schematic diagram shown as a filter circuit which is an equivalent circuit for explaining the function of the phase compensation circuit shown in FIG. Referring to FIG. 12, FIG.
The first multiplexer 161 of the phase compensation circuit shown in FIG.
2 is equivalent to R2. From this, the cutoff frequency ωs of the phase compensation circuit shown in FIG.

[0092]

[Equation 4] And the magnification n is

[0093]

[Equation 5] , Respectively. As a result, the center frequency fc is

[0094]

[Equation 6] Stipulated in.

Next, the gain intersection shown in FIG.
To third acceleration sensors 12x, 12y and 12z
A method of obtaining each output of will be described. Here, acceleration is α, control deviation is ε, gain intersection frequency
(It is the same frequency as the center frequency of the phase compensation shown in the equation (6)) is fc, the phase compensation range is n, and the cutoff frequency fb.
That is, when ωs shown in the equation (4) is fb, the secondary resonance frequency of the slide base 14 is f ₂ , and Q ₂ is the peak amount of the secondary resonance frequency f ₂ ,

[0096]

[Equation 7] Is satisfied. At this time, ωs, that is, fb is

[0097]

[Equation 8] Can be written as In the equation (7), the gain intersection frequency fc is

[0098]

[Equation 9] It is effective in the range that satisfies

[0099]

As described above, according to the optical head device of the present invention, the acceleration applied to the holding means for movably holding the condensing means detected by the detecting means .
The maximum acceleration of them is detected and the maximum acceleration detected
After obtaining the maximum gain corresponding to
Of the component due to the eccentricity of the recording surface and the component due to
The maximum value of each measured and predicted component is set as the upper limit
The gain of the servo loop and the gain
And the output of the holding means driving means for driving the holding means by changing the center frequency of the phase compensation is controlled, so that the light from the condensing means held by the holding means is accurately reflected on the recording surface of the recording medium. Collected.

[0100]

Further, the acceleration provided to the lens holding means for holding the objective lens is the distance between the objective lens and the recording surface of the recording medium and the distance required for collecting the light passing through the objective lens. And a second difference signal generating means for obtaining the difference between the focal point of the light passing through the objective lens and the center of the guide groove formed on the recording surface of the recording medium. And each is required.

[0102]

[0103]

[0104]

The positional relationship between the objective lens and the recording surface of the recording medium is maintained at a high response speed. Further, when the amount of shake or eccentricity of the recording medium exceeds the standard size, or during recording of information data to the recording medium or during reproduction of information data from the recording medium, a large external vibration or shock, that is, Even when a disturbance is applied, the width of change in the control amount for controlling the positional relationship between the objective lens and the recording medium within a predetermined range is reduced.

Therefore, the processing speed is not lowered, and the information can be surely reproduced from the optical disk even if the optical disk on which the information is already recorded changes in shape such as a warp. Provided is an optical disk device capable of preventing contact or contact between a lens holder holding an objective lens and a structure of an optical head device.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical head device to which an embodiment of the present invention is applied.

2 is a plan view of the optical head device shown in FIG. 1 and a sectional view taken along a plane including an optical axis of an objective lens.

FIG. 3 is a schematic block diagram showing an example of an information recording / reproducing apparatus in which the optical head device shown in FIGS. 1 and 2 is incorporated.

4 is a block diagram showing an example of a focus control circuit incorporated in the information recording / reproducing apparatus shown in FIG.

5 is a block diagram showing an example of a tracking control circuit incorporated in the information recording / reproducing apparatus shown in FIG.

6 is a schematic diagram showing the principle of focus detection and information reproduction in the information recording / reproducing apparatus shown in FIG.

FIG. 7 is a chart showing an algorithm for obtaining a disturbance acceleration that is an embodiment of the present invention.

8 is a flowchart showing a procedure for obtaining a disturbance acceleration according to the algorithm shown in FIG.

9 is a schematic circuit diagram showing an example of a gain controller that can be used in each of the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5. FIG.

10 is a Bode plot showing the relationship between the gain of the servo loop provided by the gain controller shown in FIG. 9 and the center frequency of phase compensation.

FIG. 11 is a schematic circuit diagram showing an example of a phase compensation unit that can be used in each of the focus control circuit and the tracking control circuit shown in FIGS. 4 and 5.

12 is a schematic circuit diagram showing an equivalent circuit of the phase compensation section shown in FIG.

[Explanation of symbols]

2 ... Optical head device, 4 ... Motor, 1
0 ... Objective lens, 12 ... Lens actuator, 12a ... Mirror, 12b
… Focus coil, 12c… Track coil,
12x ... 1st acceleration sensor, 12y ... 2nd acceleration sensor, 12z ... 3rd acceleration sensor, 14
… Slide base, 16… Linear motor,
18 ... Bearings, 20a and 20
b ... Guide shaft, 22a and 22b ... Position sensor, 24a and 24b ... Linear scale, 25a and 25b ... Position detection part, 26a and 26b ... Auxiliary yoke, 27a and 27b ... Magnet, 28a and 28b ... Yoke, 29a to 29d ... Connecting member,
30 ... Semiconductor laser element, 32 ... Collimating lens, 34 ... Beam splitter, 36 ... Lens unit, 38 ... Photodetector, 51 ...
Focus error detector, 52 ... Gain controller, 53 ... Phase compensation circuit, 54 ... Lens actuator drive circuit, 55 ... Focus coil,
56 ... Surface runout acceleration detector, 61 ... Track error detector, 62 ... Gain controller, 6
3 ... Phase compensation circuit, 64 ... Lens actuator drive circuit, 65 ... Trax coil,
66 ... Eccentric acceleration detector, 67 ... Linear motor drive circuit, 68 ... Linear motor, 69 ... Speed detector, 100 ... Optical disk device, 102
... CPU, 102a ... Selector, 10
4 ... Memory, 106 ... Control bus,
110 ... Laser control circuit, 112 ... Linear motor control circuit, 114 ... Video signal processing circuit,
116 ... Focus control circuit, 118 ... Tracking control circuit, 120 ... Position / speed control circuit, 122
... Motor drive circuit, 124 ... Focus coil drive section, 126 ... Track coil drive section, 13
2 ... A / D converter, 134 ... D / A converter, 151 ... First multiplexer, 152
… Second multiplexer, 153… Amplifier, 161
... first multiplexer, 162 ... second multiplexer, 163 ... amplifier, D
…optical disk.

Claims (3)

(57) [Claims] 1. Condensing means for condensing light on a recording surface of a recording medium, and holding means for movably holding the condensing means in a direction orthogonal to the recording surface and in a direction parallel to the recording surface. A holding means driving means for moving the holding means in at least one of a direction orthogonal to the recording surface and a direction parallel to the recording surface; a detecting means for detecting an acceleration applied to the holding means; Detects the maximum acceleration of the detection results of
The maximum gain corresponding to the detected maximum acceleration.
After the recording, the component caused by the blur of the recording surface and the recording
The components due to the eccentricity of the surface are predicted, and the maximum of each predicted component is calculated.
When controlling the holding means driving means with a large value as the upper limit
The center frequency of gain and phase compensation of the servo loop of
An optical head device comprising: a control unit that changes the output of the holding unit driving unit. 2. An objective lens for condensing light on a recording surface of a recording medium, and the objective lens is movably held in a direction orthogonal to the recording surface, a direction parallel to the recording surface and a radial direction. Lens holding means, first lens driving means for moving the lens holding means in a direction orthogonal to the recording surface, and second lens for moving the lens holding means in a direction parallel to the recording surface and in a radial direction. Driving means, first difference signal generating means for obtaining a difference between a distance between the objective lens and the recording surface and a distance required for collecting the light passing through the objective lens, Second difference signal generating means for obtaining a difference between the condensing point of the light passing through the objective lens and the center of the guide groove formed on the recording surface; and an output signal of the first difference signal generating means, Output of second difference signal generating means From each item, and acceleration detecting means for detecting an acceleration that is provided on the lens holding means, the maximum acceleration of the detection result by the acceleration detecting means
The maximum acceleration corresponding to the maximum acceleration detected.
After obtaining the in, the component due to the blurring of the recording surface
Each component predicted by predicting a component caused by the eccentricity of the recording surface
The holding means driving means is controlled with the maximum value of the component as the upper limit.
Center of gain and phase compensation of servo loop when controlling
By changing the frequency, the first lens driving means or the front
Control output of at least one of the second lens driving means
And a control unit for controlling the optical head device. 3. An objective lens for collecting light on a recording surface of a recording medium.
At least in the direction orthogonal to the recording surface or the recording surface.
When moving in a parallel direction, the objective lens and recording surface
It is necessary to collect the light passing through the space and the objective lens.
The difference between the required distance and the point where light passes through the objective lens
The objective lens is determined from the difference from the center of the guide groove formed on the recording surface.
The acceleration that acts on the
The maximum acceleration of the
After finding the maximum gain corresponding to the
And predict the component due to the eccentricity of the recording surface.
The position of the objective lens is controlled with the maximum value of each component as the upper limit.
Center of gain and phase compensation of servo loop when controlling
By changing the frequency, the objective lens and the recording surface of the recording medium
Characterized by positioning the positional relationship within a predetermined range
Objective lens position control method.