JPH11306553A - Method of tracking control and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a track jump driving signal at any time for operating an accurate track servo by varying a track jump driving signal according to a lens shift signal in a device for recording/reproducing on/from an optical disk medium. SOLUTION: In the state where there is no lens shift, for a drive signal to operate an actuator for a track jumping, an acceleration pulse and a slowdown pulse are set equal to each other. Since a proper driving force for a track jump changes with lens shifts, a voltage or a time width of a drive signal for a track jump and further, data which change both are stored in a memory beforehand according to the lens shift signals. Thus, even if a lens shift occurs and a moving rate to a lens driving force changes, it is possible to properly correct the track jump driving force at any time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a tracking control method for an apparatus for recording / reproducing on / from an optical disk medium having a narrow track pitch. More specifically, as the optical disk medium, the present invention can be applied to a DVD-R, a rewritable type thereof, and a high-density optical disk such as a DVD. Related to the device.

[0002]

2. Description of the Related Art In a recordable optical disk drive, in order to make a light spot follow an information recording track (for example, a groove) formed on a medium, a difference signal of a diffracted light distribution from a guide track (for example, a land) is used. , A so-called push-pull tracking method is used. This push-pull tracking method can obtain a tracking error signal with a very simple configuration. On the other hand, as the capacity of optical discs has increased, the light spot used for recording / reproduction has become smaller, but the track pitch on the media has become narrower, and the amplitude of the tracking error signal has increased. It is getting smaller. Therefore,
In order to obtain a tracking error signal, a high-precision device is required.

However, in the conventional push-pull tracking method, when the objective lens is moved so that the light spot follows the eccentric component of the disk for tracking control, the diffraction distribution on the photodetector also moves. Due to the shift of the diffraction distribution, an offset occurs in the tracking error signal. Also, when the disk is tilted, the two photodetectors arranged parallel to the track lose their balance,
Even when the light spot is at the center of the information recording track, a phenomenon that the tracking error signal does not become zero, that is, a track offset occurs. As a result, there is a problem that the light spot cannot be accurately positioned at the center of the information recording track.

As described above, the push-pull tracking system conventionally used has advantages and disadvantages and a large offset due to a lens shift. Therefore, the servo system controls not only the lens but also the carriage at high speed. Since a step servo is required, the cost is high. As one conventional measure for solving such a problem, there has been proposed a low-cost servo system which eliminates the need for a two-stage servo by providing a lens shift detecting means and an offset correcting means (for example, Japanese Patent Application Laid-Open No. Hei 6 (1994) -64605).
-44587 and JP-A-9-265649).

More specifically, normal recording is enabled by detecting a lens shift and correcting an offset instead of a two-step servo (see Japanese Patent Application Laid-Open No. Hei 6-4).
No. 4587). Further, an offset component of the light spot position from the track center is detected by a meandering frequency component signal obtained from a meandering guide groove (Japanese Patent Application Laid-Open No. 9-265649). As described above, in the optical disc, a method of reducing the total cost of the system by simplifying the optical system and the mechanical configuration as much as possible and providing the correction means is generally performed. Here, an optical system in a conventional optical disk device will be described with reference to the drawings.

FIG. 5 is a schematic diagram showing a configuration of a main part of an optical system in an optical disk device. In the figure, 1 is a light source such as a laser, 2 is a coupling lens,
3 is a beam splitter, 4 is a reflection plate, 5 is a 1/4 wavelength plate, 6 is an objective lens, 7 is a medium, 7a is a recording surface, 8
Is a condenser lens, 9 is a photodetector, 10 is an I / V amplifier, 1
1 is an actuator, 12 is a tracking motor, 1
3 is a focusing motor, 14 is a lens holder, 15
Is a lens shift detecting means, 16 is a carriage, 17 is a tracking error signal detecting means, 18 is an offset adding means, 19 is an adder, 20 is a tracking drive circuit,
1 denotes a jump drive circuit, A and B each output of the I / V amplifier 10, TE denotes a tracking error signal, and SP denotes a light spot.

The operation of generating the tracking error signal TE in the optical disk device shown in FIG. 5 will be briefly described. Light emitted from a light source 1 such as a laser
The light is condensed on the recording surface 7 a on the medium 7 by the coupling lens 2, the beam splitter 3, the reflection plate 4, the 波長 wavelength plate 5, and the objective lens 6. The light reflected on the recording surface 7a returns to the same optical system again, is reflected by the beam splitter 3, and is condensed by a condenser lens 8 on a photodetector 9 composed of light receiving elements A and B, and is converted into an electric signal. You. Photodetector 9
Is normally converted from a current to a voltage by the I / V amplifier 10 and various calculations are performed, but the calculation may be performed without changing the current.

FIG. 6 shows a recording surface 7a associated with a lens shift.
FIG. 4 is a diagram showing an example of a change state of a light amount distribution on a light receiving element due to reflected light from (2), (1) is a case where there is no lens shift;
Indicates a case where there is a lens shift. The reference numerals in the figure are the same as those in FIG. 5, 31 is an information recording track (for example, a groove), 32 is a guide track (for example, a land),
Reference numeral 33 denotes the center of the information recording track 31, reference numeral 34 denotes the center of the objective lens, and reference numeral 35 denotes a dividing line between the light receiving elements A and B of the photodetector 9.

On a recording surface 7a on the medium 7 shown in FIG. 5, an information recording track (for example, a groove, hereinafter appropriately referred to as a groove) 31 shown in a sectional view in FIG.
And a guide track (for example, a land, hereinafter referred to as a land as appropriate) 32 for guiding a light beam to the information recording track 31 are spirally carved. The guide track (land) 32 has pre-pits including address information in the form of groove breaks or pits. Then, each light receiving element A of the photodetector 9 shown in FIG.
The division line 35 of B is optically substantially parallel to the tangent direction of the spiral track of FIG.

In the tracking operation, the tracking error signal detecting means 17 generates a tracking error signal TE, which is spot position information, and performs control based on the tracking error signal TE. , B, a push-pull signal which is a difference signal between the left and right signals A and B of the dividing line 35) is used. This tracking error signal TE is
0 and a jump drive circuit 21 to drive a tracking motor 12 composed of a voice coil or the like so as to maintain a zero-cross point indicating the center of the groove (the information recording track 31), and apply a force to the actuator 11 by a spring or the like. The supported objective lens 6 is moved. On the output side of the tracking error signal detecting means 17, that is, on the preceding stage of the tracking drive circuit 20, an offset adding means 18 for giving an offset to the tracking error signal TE is also added.

A focus servo system for adjusting the focus of the light beam to the recording surface 7a is provided, and there is an apparatus for further dividing the photodetector 9 in order to obtain a focus servo signal for focus servo. In such a device, in the tracking control method, the dividing line 35 is used.
Each element group corresponding to the light receiving elements A and B of the photodetector 9 divided by the above may be processed as a group. Although not shown, a focus servo that drives the focus motor 13 based on the focus servo signal and causes the focus of the light spot SP to follow the recording surface 7a is also mounted.

Further, in the tracking control, a lens shift detecting means 15 for monitoring a displacement (lens shift) of the objective lens 6 is required. The lens shift detecting means 15 determines the position of the lens holder 14 on which the objective lens 6 is supported by a photo interrupter (LED and PD).
Are configured as a set, and are read by a type such as the size of the light shielding, and various types known in the related art (for example, JP-A-6-44587 and JP-A-9-265649 described above). No.)
Can be used. In addition, the position can be detected by a device (wobble track) on the medium without using such a type of sensor.

The conventional optical disk device shown in FIG. 5 has the above-described configuration, and generates a tracking error signal TE for tracking control. In the optical system shown in FIG. 5, when a lens shift occurs, a change as shown in FIG. 7 occurs.

FIG. 7 is a view for explaining a state in which a lens shift has occurred in the optical system of the optical disk apparatus shown in FIG. Reference numerals in the figure are the same as those in FIG.

FIG. 7 shows only the main parts of the optical system related to the lens shift in the optical disk apparatus shown in FIG. In FIG. 7, a solid line indicates a state without lens shift, and a broken line indicates a state where lens shift has occurred.
When the lens shift occurs and the objective lens 6 moves as indicated by the broken line, the light on each of the light receiving elements A and B of the photodetector 9 is deviated to one side. Here, a state where the tracking servo is applied according to the presence or absence of the lens shift (the spot position is controlled so that the push-pull signal becomes zero) will be described with reference to FIG.

In the state without the lens shift, the reflected light returns symmetrically to the dividing line 35 of the light receiving elements A and B as shown in FIG. The spot SP is controlled at the center 33 of the groove so that the intensity distribution becomes the same (the hatched portion in the figure indicates a region where the diffracted light is particularly strong). However, when there is a lens shift, as shown in FIG. 6 (2), the light is received with a bias toward the light receiving element A or B (in this case, the light is biased toward the light receiving element A). The light intensity is conversely biased. As a result, the spot is controlled at a position other than the groove center 33 so that the push-pull signal of the difference signal “AB” between the outputs of the light receiving elements A and B is canceled to be zero. This state will be described with reference to FIG. 8 using push-pull signals at the time of track movement and at the time of jump.

FIGS. 8A and 8B are diagrams showing an example of a change state of a push-pull signal at the time of track movement and at the time of jump due to a lens shift. FIG. 8A shows a case where there is no lens shift, and FIG. Show. The reference numerals in the figure are the same as those in FIG. 6, where 36 indicates the zero cross position and 37 indicates the offset of the push-pull signal.

When there is no lens shift, FIG.
As shown in (1), zero crossing (36 in the figure) occurs at the groove center 31. However, when a lens shift occurs, as shown in FIG. 8B, an offset 37 is added to the push-pull signal, and the zero cross point (36 in FIG. 8) is not at the center 33 of the groove. Further, when tracking is performed on a certain track and 1 tracking is performed and there is no lens shift, as shown in FIG. 8 (1), zero is symmetrical and +/- side is symmetrical. , A stable jump is possible. However, if there is a lens shift, as shown in FIG. 8 (2), the push-pull signal becomes asymmetric, so that the jump is likely to fail. Moreover,
When a change in the spring constant holding the lens (objective lens 6) or a change in the driving force of the actuator 11 occurs,
The probability of a jump failure is even higher.

[0019]

BACKGROUND OF THE INVENTION Also, the inventors of the present invention have jointly
Japanese Patent Application No. 9-278 proposes a track offset removal method for detecting a track offset component and correcting tracking by using signals obtained from LPPs present on the left and right of a recording track specified by the -R standard.
No. 256 optical disk device). According to this track offset removing method, although tracking can be corrected, recording / recording on an optical disk medium having a narrow track pitch is performed.
No particular consideration is given to tracking control of the reproducing apparatus.

[0020]

As described in the prior art, a medium having a narrow track pitch has appeared, and it has been difficult to accurately follow a track with a push-pull tracking system conventionally used. Has become. As one of the countermeasures, a system using a two-stage servo for controlling not only the lens but also the carriage at high speed has been proposed, but there is a problem that the cost is increased.

Therefore, a low-cost servo system which eliminates the need for a two-stage servo by providing a lens shift detecting means and an offset correcting means has been proposed (Japanese Patent Laid-Open No. 6-44587, cited above). JP-A-9-26
No. 5649). However, in an apparatus for recording / reproducing data on / from an optical disk medium having a narrow track pitch, the presence of a non-linear component in the track jump driving force is a serious problem. Here, a change in the spring constant that changes due to the lens shift will be described.

FIG. 9 is a diagram showing an example of the relationship between the holding form of the objective lens 9 and the force generated by the spring. (1) shows a case where there is no lens shift, and (2) and (3) show a lens shift. Indicates when there is. The reference numerals in the figure are the same as those in FIG. 5, 22 indicates a spring, F and F 'indicate the force generated by the spring 22,...

The objective lens 6 is fixed to a lens holder 14 and is provided with a rod-shaped or plate-shaped spring 22 for the actuator 1.
1 supported. In FIG. 9, the center “•” of the lens and the center “×” of the light beam are preferably matched by assembling adjustment, but may be slightly shifted. Normally, the force F (x) generated by the spring 22 is represented by the following equation (1).

[0024]

## EQU1 ## F (x) = k.x (1) This equation (1) is an approximation of the force generated in a region where the spring 22 has a linear characteristic. Here, k is a spring coefficient, and x is a bending distance. However, strictly speaking,
The linearity breaks down as x increases, resulting in a force F '(x + y) as shown in the following equation (2).

[0025]

F '(x + y) = k (x + y) + f (x + y) = k ・ x + ky ・ f (x + y) (2) As is clear from the equation (2), the force F ′ (x +
y) has a non-linear component. That is, F '(x
+ Y) ≠ F (x) + F (y), and if a lens shift occurs, a proper track jump cannot be performed with the same driving force. Although largely related to the characteristics and configuration of the spring, if the linear region is small, the nonlinear component may not be negligible in the lens shift range that occurs in actual use.

In particular, when the track pitch is narrow and a precise track jump is required, it cannot be ignored. FIG. 9 shows the case of lens movement by a spring support method, but a method called axis sliding (a large lens holder having a rotation axis at the center has a lens at the end, and by rotating the holder, In the type that moves the lens), there is a support that generates a force so as to determine the lens position without driving force. Even in this case, as in the previous case, there is a non-linear component. There is a problem. Next, a change in the driving force of the actuator 11 will be described.

FIGS. 10A and 10B are perspective views showing an example of a voice coil motor used as an actuator. FIG. 10A is a diagram for explaining the relationship between coil current and driving force, and FIG. In the figure, 41 is a magnetic material, 42 is a permanent magnet, 43 is a coil, 44 is a current direction, 45 is a flow direction of magnetic flux, 46 is a driving force, and C to E represent points.

There are various types of voice coil motors. FIG. 10 shows an example in which the magnetic body 41 has an E-shaped side surface. A permanent magnet 42 is added to a part of the magnetic body 41.
Then, as shown in FIG. 10 (2), the magnetic flux densities emitted from the permanent magnet 42 are different from each other, such as dense at the point C, small at the point D, and coarser at the point E. . When a coil 43 having a shape as shown in FIG. 10A is inserted into the magnetic body 41 and a current flows in the direction of 44, a driving force 46 is generated according to Fleming's left-hand rule. The electromagnetic force (F) generated by the coil 43 is represented by L, the coil length at which the coil 43 is linked to the magnetic flux in the magnetic circuit gap, B the magnetic flux density in the gap, and i the current flowing through the coil 43. If

[0029]

F = iLB (3), where the position of the coil 43 is at the point C,
It can be seen that the driving force changes between the point and the point E. As described above, the lens shift involves the non-linearity of the driving force of the spring 22 and the actuator 11, and depending on the presence or absence of the lens shift, a different appropriate track jump driving force is required.

Incidentally, in the case of the conventional wide track pitch, the track jump driving force is also set large, so that such a non-linear component is negligible in practical use. However, as described above, as the track pitch becomes narrower, it is necessary to eliminate the effect of the non-linear component in the track jump driving force in a device that requires a precise track jump. ing. According to the present invention, an appropriate track jump driving force is always obtained even if a lens shift occurs and a moving rate with respect to the lens driving force changes.
It is an object to realize a tracking control method capable of performing accurate track servo.

[0031]

According to a first aspect of the present invention, there is provided a tracking control method comprising: a light source such as a semiconductor laser; an actuator mounted on a carriage for driving an objective lens separately from the light source; Lens shift detecting means for detecting a displacement in the direction as a lens shift signal, and a positional error between a spot formed by condensing a light beam from a light source by an objective lens and a track center of the recording medium, the track groove or the like. Tracking error signal detection means for detecting as a tracking error signal by a change in the far-field image of the diffracted light from the pit row, and a tracking drive circuit for driving an actuator so that the light spot follows the track center using the tracking error signal. Forced to move the light spot to a nearby track And a jump driving circuit for generating a track jump driving signal for driving the actuator is provided an apparatus for recording / reproducing the optical disc medium, and configured to change a track jump driving signal in accordance with the lens shift signal.

According to a second aspect of the present invention, in the tracking control method of the first aspect, the voltage value of the track jump drive signal is changed according to the lens shift signal.

According to a third aspect of the present invention, in the tracking control method of the first aspect, the time width of the track jump drive signal is changed according to the lens shift signal.

According to the tracking control method of the fourth aspect, in the tracking control method of the first to third aspects,
The voltage value or the time width of the track jump drive signal is changed nonlinearly in accordance with the lens shift signal.

According to a fifth aspect of the present invention, in the tracking control method of the first to fourth aspects,
The track jump drive signal that is changed according to the lens shift signal is configured to be changed according to the amplitude of the tracking error signal.

According to the tracking control method of the sixth aspect, in the tracking control method of the first to fifth aspects,
When the track servo is pulled in, the voltage value and the time width of the track jump drive signal are set to initial values.

According to the tracking control method of the seventh aspect, in the tracking control method of the first to fifth aspects,
At the time of retraction after the track has moved beyond a specific number of tracks, the voltage value and the time width of the track jump drive signal are set to the set values.

According to the tracking control method of claim 8, in the tracking control method of claims 1 to 7,
The lens shift is detected in a band higher than the carriage movement speed.

According to the tracking control method of the ninth aspect, a light source such as a semiconductor laser, an actuator mounted on the carriage and driving the objective lens separately from the light source, and a displacement (shift) of the objective lens in the tracking direction with respect to the carriage. Lens shift detecting means for detecting light as a lens shift signal, and a position error between a spot formed by condensing a light beam from a light source by an objective lens and a track center of a recording medium, and diffracted light from the track groove or pit row. Tracking error signal detection means for detecting a tracking error signal based on a change in the far-field image of the target, a tracking drive circuit for driving an actuator so that the light spot follows the track center using the tracking error signal, Force actuate to move spot A drive circuit for generating a track jump drive signal for driving the optical disc medium; and a track offset removing means for adding an offset to the tracking error signal in accordance with the lens shift signal. While changing the track jump drive signal accordingly,
It is configured to remove the track offset.

According to a tenth aspect of the present invention, there is provided an optical disk device, wherein a means for performing the tracking control method according to the first to ninth aspects is provided, and the medium having a track pitch of 75% or less of the light spot diameter (λ / NA) is provided. It is configured to access.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tracking control method and an optical disk apparatus according to the present invention are characterized in that a track jump drive signal is changed in accordance with a lens shift signal. The hardware configuration is basically the same as that of FIG.
The jump drive circuit 21 performs a correction by a program in a built-in ROM, a work memory, or an operation of a control IC so that a driving force corresponding to the lens shift amount is obtained.

First Embodiment The first embodiment corresponds to the first aspect of the present invention, but also relates to the second to tenth aspects of the present invention. The invention is the basic invention. In the first embodiment, in order to solve the problem that an appropriate driving force for a track jump changes due to a lens shift, a driving force according to a lens shift amount is generated. First, an apparatus for recording / reproducing information on / from an optical disk medium suitable for carrying out the tracking control method of the present invention will be described with reference to the optical system shown in FIG.

An apparatus for recording / reproducing on / from an optical disk medium includes a light source (1) such as a semiconductor laser and a carriage (1).
6) an actuator (11) mounted on the light source (1) to drive the objective lens (6) separately from the light source (1), and a lens shift for shifting the objective lens (6) in the tracking direction with respect to the carriage (16). A lens shift detecting means (15) for detecting a signal as a signal, and a positional error between a spot formed by condensing a light beam from the light source (1) by an objective lens (6) and a track center of the recording medium. Tracking error signal detecting means (17) for detecting as a tracking error signal based on a change in the far-field image of the diffracted light from the pit row; and an actuator (11) for following the light spot SP to the track center using the tracking error signal. And a tracking drive circuit (20) for driving the light spot, and forcibly activate the light spot SP to move it to a nearby track. And a jump driving circuit (21) for generating a track jump driving signal for driving the eta (11). The first embodiment is characterized in that a device for recording / reproducing on / from an optical disk medium composed of such components is configured to change a track jump drive signal according to a lens shift signal. Have. Next, the track jump drive signal will be described with reference to the drawings.

FIG. 1 shows a tracking error signal TE at the time of a track jump, a drive signal for operating the actuator 11 for performing the track jump, and a moving speed of the objective lens 6 at that time, for the tracking control method of the present invention. Is a time chart showing an example of the relationship between (1), each signal waveform when there is no lens shift,
(2) and (3) show appropriate drive signals when there is a lens shift.

As shown in FIG. 1A, in a state where there is no lens shift, the drive signal for operating the actuator 11 has the same acceleration pulse and the same deceleration pulse. Such a drive signal causes the objective lens 6 to move, stop on an adjacent track, and continue to follow that track. However, as described in detail in the related art, an appropriate driving force for a track jump is changed by the lens shift. Therefore, as shown in FIGS. 1 (2) and (3), data for changing the voltage or the time width of the track jump drive signal in accordance with the lens shift signal, and data for changing both of them are previously stored in the memory.

The control of the track jump drive signal in this case is realized by a control IC, a memory and the like provided in the jump drive circuit 21 of FIG. As mentioned above,
In the first embodiment, even if the lens shift occurs and the moving rate with respect to the lens driving force changes, the track jump driving force can always be corrected to an appropriate one. Therefore, according to the first embodiment, accurate track servo can be performed.

Second Embodiment The second embodiment corresponds to the second and third aspects of the present invention. The first aspect of the present invention and the fourth to tenth aspects of the present invention. Is also relevant. In the first embodiment described above, a case has been described in which, when a lens shift occurs and a moving rate with respect to a lens driving force changes, an appropriate track jump driving force is always corrected. The second embodiment is characterized in that specific means for changing a lens driving force for a track jump is configured.

First, in the second aspect of the present invention, the voltage of the drive signal is changed to change the drive force for the track jump. As shown in FIG. 1A, in the state without the lens shift, the acceleration and deceleration pulses were symmetrical, and the moving speed of the lens became triangular. However, when lens shift is occurring,
The reaction force of the spring is large (or small),
With the same drive signal, the same lens moving speed (distance) cannot be obtained. Whether the spring force increases or decreases depends on the direction of the lens shift and the direction of the track jump. Therefore, by changing the voltage of the drive signal, a large force (compared to the force of the spring) is generated at the start of the jump, and a small force is generated at the time of deceleration, to thereby move the lens at a moving speed. Control is performed so that the moving distance is kept almost the same.

Next, according to the third aspect of the present invention,
The driving force for the track jump is changed in the same manner as in the invention of (1). Although the case of changing the voltage of the drive signal has been described in the second aspect of the present invention,
The difference is that the time width of the drive signal is changed. In the case of changing the voltage as in the second aspect of the present invention, the instantaneous current increases, so that the driver IC needs a margin of performance. However, when the time width is changed in this way, a normal driver IC can sufficiently cope with the change. As described above, in the second embodiment, the voltage value (the invention of claim 2) or the time width (the invention of claim 3) of the track jump drive signal is changed according to the lens shift signal. Make up. Therefore,
A specific and simple tracking control method is realized.

Third Embodiment The third embodiment corresponds to the invention of claim 4, but the invention of claims 1 to 3 and the claims 5 to 10 described above. It is also related to the invention of The third embodiment is characterized in that the relationship between the lens shift and the drive signal is defined. When a lens shift occurs and an appropriate drive signal value is calculated from the detection result, a linear calculation is easiest. However, changes in spring force and changes in magnetic flux density are mostly not linear. Therefore, in the third embodiment, the voltage value or the time width of the track jump drive signal is changed in a non-linear manner according to the lens shift signal.

FIG. 2 is a diagram showing an example of the relationship between a drive signal and a lens shift according to the third embodiment in the tracking control method of the present invention. The horizontal axis in the figure indicates the lens shift amount, and the vertical axis indicates the drive signal.

In FIG. 2, the solid line indicates the characteristic at the time of the track jump to the inner periphery, and the broken line indicates the characteristic at the time of the track jump to the outer periphery. As shown in FIG. 2, non-linear data (in this case, the correction amount gradually increases as the lens shift amount increases) indicated by a solid line is stored in a memory in advance. Alternatively, the approximation formula is created and the calculation is performed in response to the change in the drive signal. In the case of a voice coil motor, the driving force suddenly decreases when the value exceeds a certain value, so that when the lens shift amount exceeds a certain value,
The correction may be made. As described above, in the third embodiment, the time width of the track jump drive signal is changed according to the lens shift signal. Therefore, even a mechanism having a non-linear and special driving force characteristic such as a change in magnetic flux density due to the shape of the voice coil motor can perform accurate track servo.

Fourth Embodiment The fourth embodiment corresponds to the fifth aspect of the present invention. However, the fourth to fourth aspects of the present invention and the sixth to tenth aspects of the present invention. It is also related to the invention of In the fourth embodiment, the drive signal change rate table or the constant of the approximate expression is changed according to the amplitude of the tracking error signal that roughly indicates the track pitch of the medium. The basic principle is that when the track pitch is wide, the driving force required for track jump becomes large,
Small changes such as a non-linear component of the spring and a reduction in the driving force of the actuator are negligible.

However, as the track pitch becomes narrower, the drive power becomes more sensitive to the jump driving force. Therefore, the drive signal is adjusted according to the amplitude of the tracking error signal. Therefore, according to the fourth embodiment, it is possible to adjust the track jump drive signal corresponding to various media having different track pitches, and to perform accurate track servo.

Fifth Embodiment Although the fifth embodiment corresponds to the invention of claim 6, the invention of claims 1 to 5 and the invention of claims 7 to 10 are described. It is also related to the invention of In the fifth embodiment, when the track servo is pulled in, the voltage value and the time width of the track jump drive signal are set to the initial values. When pulling in from a state where tracking is lost, the track jump drive signal is set to an initial value. In a state where the track control is not performed, the lens is normally held at the mechanical center position of the apparatus (approximately the same position as the center of the light beam) by a force such as a spring.

However, when the vehicle is off the track,
That is, when the tracking servo loop is not operating, the lens is supported by almost only the force of the spring, so when the carriage is moved at high speed, the acceleration receives the inertia force and the lens is displaced from the center of the carriage. Will be. When this value is detected by the lens detection means having a low detection speed, the carriage movement ends, and
At the moment when the lens returns to the mechanical center by the force of the spring, it is erroneously detected that the lens position is still off the center.

Therefore, in the fifth embodiment, the track jump drive signal is set to the initial value when the track servo is pulled in. That is, at the timing when the movement of the carriage is completed and the operation of pulling in the track is started, the same track jump drive signal as in the state without the lens shift can be said to be the optimum set value. Therefore, regardless of the speed (time) of the lens position detection, an appropriate adjustment of the track jump drive signal can be promptly performed when the track servo is pulled in, and accurate track servo can be performed.

Sixth Embodiment The sixth embodiment corresponds to the seventh aspect of the present invention. However, the sixth to sixth aspects of the present invention and the eighth to tenth aspects of the present invention. It is also related to the invention of In the sixth embodiment, the configuration is such that the track jump drive signal is set to a set value at the time of retraction after the track has moved beyond a specific number of tracks. In the tracking control, the jumping method is changed according to the number of tracks that normally move. For example, a small number of track movements can be handled by moving only the lens, and a large number of track movements exceeding a certain predetermined number can be fixed by keeping the lens position just before the movement, or the mechanical center position of the apparatus. And the carriage is moved.

Therefore, at the time of track retraction performed after the movement is completed, the lens position is already known, and it is not necessary to calculate from the output of the lens position sensor to obtain an appropriate drive signal, and the track retraction can be performed quickly.
As described above, according to the sixth embodiment, it is possible to quickly adjust the track jump drive signal properly regardless of the speed (time) of lens position detection at the time of retraction after the carriage movement is completed. Therefore, accurate track servo can be performed.

Seventh Embodiment The seventh embodiment corresponds to the eighth aspect of the present invention. However, the seventh to seventh aspects of the present invention, and the ninth and tenth aspects of the present invention. It is also related to the invention of In the seventh embodiment, the lens shift is detected in a band higher than the carriage movement speed (frequency band).

FIG. 3 is a view for explaining the state of movement of the carriage. The reference numerals in the figure are the same as those in FIG. 5, and G and H indicate the right end and the left end of the carriage.

In the case of a relatively inexpensive system, a method of moving the carriage 16 with a combination of gears is often adopted. Most systems using a CD-ROM or the like have such a configuration. In this configuration, since the minimum movement accuracy of the carriage 16 is relatively rough, when a higher accuracy is required, it is dealt with by moving the objective lens 6. Light spot SP on track
When the reproduction / recording is continuously performed by following, the objective lens 6 moves to the right side to move the light spot SP to the outer periphery. When the state G at the right end of the carriage minimum accuracy is reached, the carriage 16 moves to the state H.

At this time, the objective lens 6 is on the left side of the carriage 16, and the correction of the track jump drive signal is completely opposite between G and H. Even in this state, in order to perform an accurate correction operation, the band for detecting the lens position is set to a band higher than the carriage moving speed, and instantaneously responds to a change in the correction amount due to the carriage movement. By the way, the carriage 16 has several K
Since the lens moves only in the frequency band of Hz, it is sufficient to detect the lens position in the order of several tens to several hundreds KHz, and there is no problem at all. As described above, according to the seventh embodiment, when following a desired track, even if the relative position between the light beam and the lens changes due to the movement of the carriage with minimum accuracy, the lens position detection can be performed at a higher speed. Therefore, the track jump drive signal can always be properly maintained.

Eighth Embodiment The eighth embodiment corresponds to the ninth aspect of the present invention. However, the eighth aspect of the present invention relates to the first to eighth aspects and the tenth aspect.
It is also related to the invention of In the eighth embodiment,
In order to stabilize the tracking operation at the time of lens shift, the tracking control method described in the first embodiment is also performed by removing the track offset component. As a specific means therefor, a device for recording / reproducing on / from the optical disk medium described in the first embodiment is provided with a track offset removing means for adding an offset to the tracking error signal TE in accordance with the lens shift signal ( An offset adding means 18) is added to change the track jump drive signal in accordance with the lens shift signal and remove the track offset.

As described with reference to FIG. 8, the push-pull signal is offset (3
7) occurs. At the time of a track jump in this state, the amplitude of one side (the lower side in FIG. 8) of the push-pull signal is small, resulting in an unstable track jump. When the lens shift is large, the offset (37) is further increased, and the push-pull signal does not cross zero. As a result, tracking cannot be performed at all with the usual method. When the ratio between the track pitch and the light spot diameter (λ / NA) is 75% or less, this offset becomes remarkable, and the push-pull signal does not cause zero crossing due to a practically used lens shift, so that tracking becomes impossible.

The track offset removing means includes:
Conventionally known or well-known means are used in combination. As described above, in the eighth embodiment, the track jump drive signal is changed according to the lens shift signal, and the track offset is removed. Therefore, the lens shift amount limited by the track offset amount can be greatly increased, and accurate track jump can be realized by a mechanism having an inexpensive configuration.

Ninth Embodiment The ninth embodiment corresponds to the tenth invention, but also relates to the first to ninth inventions. As described in the previous embodiment, when the track pitch becomes narrow, the push-pull signal becomes very small,
In practice, many problems arise in tracking control. An example will be described with reference to the following experimental data.

FIG. 4 is a timing chart for explaining an example of a change state between the lens shift and the push-pull signal.
(1) when the lens shift is +150 μm, (2) when there is no lens shift, and (3) when the lens shift is −150 μm.
The case of is shown.

In this experiment, the relationship between the track pitch and the light spot diameter is about 74%, and no offset adjustment or adjustment of the track jump drive signal is performed. Usually, a lens shift that can occur with an inexpensive configuration is about ± 400.
μm. However, in this experimental data, ± 150μ
At m, the push-pull signal at the time of the track jump has already been disturbed and is in an unstable state. From the results of the above experiments, the relationship between the track pitch and the light spot diameter was 7
It is necessary to mount the means for implementing the tracking control method of the present invention described in the first to eighth embodiments in the optical system of the apparatus for media of 5% or less. By providing a means for implementing this tracking control method, a device without any countermeasure can provide a good track servo even in the case of a relationship between a medium and a drive where a track error signal is small and tracking is difficult. Can be performed.

[0070]

According to the tracking control method of the first aspect,
It is configured to change the track jump drive signal according to the lens shift signal. Therefore, even if a lens shift occurs and the movement rate with respect to the lens driving force changes, the track jump driving force is always corrected to an appropriate value, so that accurate track servo can be performed.

According to the tracking control method of the present invention, the voltage value of the track jump drive signal is changed in accordance with the lens shift signal. Therefore, in addition to the effect of the tracking control method of the first aspect, a specific and simple tracking control method is realized.

According to a third aspect of the present invention, in the tracking control method of the first aspect, the time width of the track jump drive signal is changed according to the lens shift signal. Therefore, in addition to the effect of the tracking control method of claim 1, accurate track servo can be performed using an inexpensive drive circuit.

According to the tracking control method of the fourth aspect, in the tracking control method of the first to third aspects,
The voltage value or the time width of the track jump drive signal is changed nonlinearly in accordance with the lens shift signal. Therefore, in addition to the effects of the tracking control methods of claims 1 to 3, even if the mechanism has a non-linear and special driving force characteristic such as a change in magnetic flux density due to the shape of the voice coil motor, accurate track servo can be performed. Can do it.

According to the tracking control method of the fifth aspect, in the tracking control method of the first to fourth aspects,
The track jump drive signal that is changed according to the lens shift signal is configured to change the amount of change according to the amplitude of the track error signal. Therefore, in addition to the effects of the tracking control method according to claims 1 to 4, it is possible to adjust a track jump drive signal corresponding to various media having different track pitches, and to perform accurate track servo.

According to the tracking control method of the sixth aspect, in the tracking control method of the first to fifth aspects,
When the track servo is pulled in, the voltage value and the time width of the track jump drive signal are set to initial values. Therefore, in addition to the effect of the tracking control method according to the first to fifth aspects, it is possible to quickly adjust a proper track jump drive signal at the time of pulling in the track servo regardless of the speed (time) of the lens position detection. , And accurate track servo can be performed.

According to the tracking control method of the seventh aspect, in the tracking control method of the first to fifth aspects,
At the time of retraction after the track has moved beyond a specific number of tracks, the voltage value and the time width of the track jump drive signal are set to the set values. Therefore,
In addition to the effects of the tracking control method according to any one of the first to fifth aspects, an appropriate adjustment of the track jump drive signal can be quickly performed regardless of the speed (time) of lens position detection at the time of retraction after the carriage movement is completed. Therefore, accurate track servo can be performed.

According to the tracking control method of claim 8, in the tracking control method of claims 1 to 7,
The lens shift is detected in a band higher than the carriage movement speed (frequency band). Therefore, in addition to the effects of the tracking control method according to claims 1 to 7, the lens position detection is performed even when the relative position between the light flux and the lens changes due to the movement of the carriage with the minimum accuracy when following a desired track. Is performed at a higher speed, so that the track jump drive signal can always be properly maintained.

According to the tracking control method of the ninth aspect, the track jump drive signal is changed according to the lens shift signal, and the track offset is removed. Therefore, the lens shift amount limited by the track offset amount can be significantly widened, and accurate track jump can be realized by a mechanism having an inexpensive configuration.

According to a tenth aspect of the present invention, there is provided an optical disk device for accessing a medium having a track pitch whose track pitch is 75% or less of a light spot diameter (λ / NA). Means for implementing the control method are provided. Therefore, in addition to the effects of the tracking control method according to the first to ninth aspects, even in the case of an apparatus without any countermeasure, even in the case of a relationship between a medium and a drive in which tracking error signals are small and tracking is difficult, Good track servo can be performed.

[Brief description of the drawings]

FIG. 1 shows a tracking control method according to the present invention; a tracking error signal TE during a track jump and an actuator 11 for performing the track jump;
6 is a time chart showing an example of a relationship between a drive signal for operating the operation of the lens and the moving speed of the objective lens 6 at that time.

FIG. 2 is a diagram illustrating an example of a relationship between a drive signal and a lens shift according to a third embodiment in the tracking control method of the present invention.

FIG. 3 is a diagram illustrating a state of movement of a carriage.

FIG. 4 is a timing chart illustrating an example of a change state between a lens shift and a push-pull signal.

FIG. 5 is a schematic diagram showing a configuration of a main part of an optical system in the optical disk device.

FIG. 6 is a diagram showing an example of a change state of a light amount distribution on a light receiving element due to reflected light from a recording surface 7a with a lens shift.

FIG. 7 is a diagram illustrating a state in which a lens shift has occurred in the optical system of the optical disc device illustrated in FIG. 5;

FIG. 8 is a diagram showing an example of a change state of a push-pull signal at the time of track movement and jump at the time of lens shift.

FIG. 9 is a diagram showing a relationship between a holding form of the objective lens 9 and a force generated by a spring.

FIG. 10 is a perspective view showing an example of a voice coil motor used as an actuator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Coupling lens, 3 ... Beam splitter, 4 ... Reflector, 5 ... 1/4 wavelength plate, 6 ...
... Objective lens, 7 ... Media, 7a ... Recording surface, 8 ...
... Condenser lens, 9 ... Photodetector, 10 ... I / V amplifier, 11 ... Actuator, 12 ... Tracking motor, 13 ... Focus motor, 14 ... Lens holder, 15 ... Lens shift Detecting means, 16: carriage, 17: tracking error signal detecting means,
18 offset adding means, 19 adder, 20
... Tracking drive circuit, 21 ... Jump drive circuit

Claims (10)

[Claims] 1. A light source such as a semiconductor laser, an actuator mounted on a carriage and driving an objective lens separately from the light source, and a lens shift signal indicating a displacement (shift) of the objective lens in the tracking direction with respect to the carriage. Lens shift detecting means for detecting the position error between the spot formed by condensing the light beam from the light source by the objective lens and the center of the track of the recording medium. Tracking error signal detection means for detecting as a tracking error signal based on a change in the field of view image; a tracking drive circuit for driving the actuator so that the light spot follows the track center using the tracking error signal; Force the actuator to move the spot A device for recording / reproducing data on / from an optical disk medium, comprising: a jump drive circuit for generating a track jump drive signal to be driven; wherein the track jump drive signal is changed according to the lens shift signal. Tracking control method. 2. The tracking control method according to claim 1, wherein the voltage value of the track jump drive signal is changed according to the lens shift signal. 3. The tracking control method according to claim 1, wherein the time width of the track jump drive signal is changed in accordance with the lens shift signal. 4. The tracking control method according to claim 1, wherein a voltage value or a time width of the track jump drive signal is changed in a non-linear manner according to the lens shift signal. Tracking control method. 5. The tracking control method according to claim 1, wherein the track jump drive signal changed according to the lens shift signal is changed according to the amplitude of the tracking error signal. Tracking control method. 6. The tracking control method according to claim 1, wherein a voltage value and a time width of a track jump drive signal are set to initial values when a track servo is pulled in. . 7. The tracking control method according to claim 1, wherein a voltage value and a time width of a track jump drive signal are set to a set value at the time of retraction after a track has moved beyond a specific number of tracks. And a tracking control method. 8. The tracking control method according to claim 1, wherein a lens shift is detected in a band higher than a speed (frequency band) of a carriage movement. 9. A light source such as a semiconductor laser, an actuator mounted on a carriage and driving an objective lens separately from the light source, and a lens shift signal indicating a displacement (shift) of the objective lens in the tracking direction with respect to the carriage. Lens shift detecting means for detecting the position error between the spot formed by condensing the light beam from the light source by the objective lens and the center of the track of the recording medium. Tracking error signal detection means for detecting as a tracking error signal based on a change in the field of view image; a tracking drive circuit for driving the actuator so that the light spot follows the track center using the tracking error signal; Force the actuator to move the spot An apparatus for recording / reproducing data on / from an optical disk medium, comprising: a jump drive circuit for generating a track jump drive signal to be driven; and track offset removing means for adding an offset to the tracking error signal in accordance with the lens shift signal. A tracking control method, wherein the track jump drive signal is changed according to a signal and a track offset is removed. 10. A medium for performing a tracking control method according to claim 1, wherein a medium having a track pitch of 75% or less of a light spot diameter (λ / NA) is accessed. Optical disk device.