JP4573329B2 - Optical disk device - Google Patents

Description

The present invention relates to an optical disk apparatus for writing / reading of the information signal on the optical disc.

  In an optical disk apparatus, an optical disk is used as an information recording medium, and information signals (data) are recorded / erased by irradiating a laser beam onto the recording surface of the optical disk on which spiral or concentric tracks are formed. In addition, data is reproduced based on the reflected light from the recording surface. An optical pickup device is provided as a device for irradiating the recording surface of the optical disc with laser light and receiving reflected light from the recording surface.

  Usually, such an optical pickup device is an optical system in which an objective lens is disposed in an optical path, guides laser light emitted from a light source to a recording surface of an optical disc, and guides return light reflected by the recording surface to a predetermined light receiving position. The optical detector is arranged at the light receiving position, and a lens driving unit that drives the objective lens in the optical axis direction (focus direction) or in a direction orthogonal to the track tangential direction (tracking direction).

  The photodetector outputs a signal including information (servo information) necessary for position control of the objective lens as well as reproduction information of data recorded on the recording surface. When data is recorded / reproduced in the optical disk apparatus, the amount of deviation between the beam spot of the laser beam irradiated on the optical disk surface and the center position of the track is based on the servo information from the photodetector. A track error signal indicating is detected. Further, a signal (lens drive control signal) for controlling the lens drive unit is generated from the track error signal. The lens drive unit shifts the objective lens based on the lens drive control signal, so that the laser beam is controlled (tracking control) so as to accurately track (track) the center of the track.

  By the way, in tracking control, the tracking accuracy of how accurately the laser beam tracks the center of the track is determined by the amplification factor (loop gain) of the amplitude of the signal wave transmitted through the tracking control system. Therefore, when the loop gain of the tracking control system fluctuates, there arises a problem that the tracking operation, particularly the track pull-in operation for pulling laser light into a predetermined track becomes unstable. For this reason, in the optical disc apparatus, it is necessary to keep the fluctuation of the loop gain of the tracking control system as low as possible.

Here, the following is proposed as a conventional technique for suppressing fluctuations in loop gain. For example, the tracking detection sensitivity is measured every time the optical disc is mounted on the optical disc apparatus, and the amplification gain at the time of amplifying the tracking error detection signal is adjusted again based on the tracking error detection sensitivity measurement value. There is a technique for keeping the loop gain constant (see, for example, Patent Document 1).
In addition, the tracking error signal offset correction value and amplitude correction value are stored in advance for a plurality of locations on the optical disc, and stable tracking control is achieved by switching between the offset correction value and the amplitude correction value according to the access location. There is a technique to perform (for example, see Patent Document 2).
Furthermore, there is a technique for improving the stability of the track pull-in operation by switching the loop gain of the tracking control system between the track pull-in operation and the time when the track pull-in operation is completed (for example, Patent Documents 3 and 4). reference).

Japanese Patent Laid-Open No. 5-274705 Japanese Patent No. 3560837 JP-A-5-144020 Japanese Utility Model Publication No. 5-90613

However, the techniques described in Patent Document 1 and Patent Document 2 described above are effective against changes in the loop gain of the tracking control system caused by a change in an optical disk to be loaded or an access area on the optical disk. However, there is no effect on the fluctuation of the loop gain caused by the lens shift. Therefore, since the amount of lens shift becomes large particularly during the track pull-in operation, it cannot be an effective technique for improving the stability of the track pull-in operation.
Further, in the techniques described in Patent Document 3 and Patent Document 4 described above, since the lens shift amount generated during the track pull-in operation is different every time, the track pull-in only by switching the loop gain of the tracking control system uniformly. It is difficult to stabilize the operation.
As described above, it is difficult to suppress the fluctuation of the loop gain caused by the lens shift, and there is a problem that the tracking operation, in particular, the track pull-in operation tends to become unstable.

  The present invention has been made to solve the technical problems as described above, and an object of the present invention is to suppress the fluctuation of the loop gain of the tracking control system caused by the lens shift and to perform stable track pull-in. It is to realize the operation.

For this purpose, an optical disc apparatus according to claim 1 of the present invention includes an optical pickup that irradiates light onto an optical disc on which a track is formed to write and / or read data, and the optical pickup. An objective lens for condensing the irradiated light as a light spot on the optical disc, a driving means for driving the objective lens in a radial direction of the optical disc with respect to the optical pickup, and the optical beam condensed on the optical disc A tracking error detecting means for detecting a deviation between the light spot and the track; and a tracking control means for controlling the driving means based on a tracking error signal output by the tracking error detecting means . The detection sensitivity of the tracking error detection means decreases as the increase occurs. And reduction characteristic, is characterized in that the change characteristic of the response sensitivity of the driving means with the movement of the objective lens, is set to reverse.

According to a second aspect of the present invention, in the optical disc apparatus according to the first aspect, the optical pickup includes a movable portion on which the objective lens is mounted, and the movable portion is movable in the tracking direction. A fixed portion attached via a support wire that is elastically deformed, and the driving means is fixed to the fixed portion so as to face the coil and the coil fixed to the movable portion. And two sets of magnets arranged at intervals in the tracking direction, and the center of the two sets of magnets in the tracking direction compared to the distance between the centers of the two sets of coils in the tracking direction. with between distance increases, the movable part that two pairs of the magnet relative to the two pairs of the coil when in the neutral state is configured to be positioned outside of the tracking direction It is characterized.

  According to the present invention, the fluctuation of the loop gain of the tracking control system caused by the lens shift can be suppressed to a very low level, so that a stable track pull-in operation can be realized.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the duplicate description thereof is simplified or omitted as appropriate.
[Embodiment 1]
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus 1 to which the present embodiment is applied. An optical disc apparatus 1 shown in FIG. 1 includes an objective lens 21, an optical pickup unit (optical pickup) 22, an actuator 23 as an example of a driving unit, a seek motor 24, a spindle motor 25, and tracking error detection as an example of a tracking error detection unit. 31, a lens shift detection unit 32 as an example of a lens shift detection unit, a first lens shift compensation unit 33 as an example of a lens shift compensation unit, and a tracking control unit 34 as an example of a tracking control unit. Here, each unit of the tracking error detection unit 31, the lens shift detection unit 32, the first lens shift compensation unit 33, and the tracking control unit 34 is realized by a microcomputer including a CPU, a RAM, a ROM, and the like. In addition, each part shown in the following Embodiments 2 to 6 is similarly realized by a microcomputer.

The optical pickup unit 22 is disposed inside the optical pickup housing 22A, irradiates the optical disc 10 with laser light emitted from a laser diode as a light source, receives reflected light from the optical disc 10 by a light receiving element, A signal corresponding to the received light intensity is generated. At that time, the objective lens 21 condenses the laser light emitted from the optical pickup unit 22 as a light spot on the surface of the optical disc 10.
The light receiving element of the optical pickup unit 22 includes a multi-divided detector (for example, a two-divided detector) in which the detection area is divided into a plurality of parts. The output signal of each detection area is used as a tracking error detection unit 31 and a lens shift detection unit. 32.
In addition, in the optical pickup unit 22, a diffraction element that diffracts the laser light emitted from the laser diode and branches it into a main beam and two sub beams is disposed. As for the light receiving element that receives the return light, a light receiving element that receives the return light of the main beam and a light receiving element that receives the return lights of the two sub beams are arranged. Therefore, the optical pickup unit 22 has a configuration in which the optical disc 10 is irradiated with the main beam and the two sub beams, and the three light receiving elements respectively receive the main beam and the two sub beams.

The actuator 23 is installed outside the optical pickup housing 22A on the optical disk 10 side, and shifts the objective lens 21 with respect to the optical pickup unit 22 in the tracking direction (direction of arrow A in the figure). Thereby, the laser beam from the optical pickup unit 22 is controlled (tracking control) so as to accurately track (track) the center of the track formed on the optical disc 10.
The seek motor 24 moves (seeks) the optical pickup unit 22 to a desired position in the radial direction of the optical disc 10. The spindle motor 25 holds the optical disk 10 and rotates it at a predetermined rotational speed.

The tracking error detection unit 31 detects a deviation (tracking error) between the beam spot of the laser beam irradiated on the optical disc 10 and the center position of the track based on the output signal from the optical pickup unit 22, and the tracking error signal Output as.
The lens shift detection unit 32 detects the shift amount of the objective lens 21 relative to the optical pickup housing 22A based on the output signal from the optical pickup unit 22, and outputs it as a lens shift signal.

The first lens shift compensation unit 33 generates a first compensation gain based on the lens shift signal output from the lens shift detection unit 32, and the generated first compensation gain and tracking output from the tracking error detection unit 31. A corrected tracking error signal obtained by integrating the error signal is output.
The tracking controller 43 generates a shift amount and a tracking actuator drive signal in the shift direction according to the corrected tracking error signal output from the first lens shift compensator 33, and drives the actuator 23 so as to reduce the tracking error. To do.

Next, generation of a tracking error signal in the tracking error detection unit 31 will be described. In the tracking error detection unit 31 of the present embodiment, a tracking error signal is generated by an operation push-pull method.
FIG. 2 shows a state in which the optical beam 10 is irradiated with the main beam mb, the sub beam sb1, and the sub beam sb2 by the optical pickup unit 22 (FIG. 2A), and the return light thereof as a light receiving element 227a, light receiving element 227b FIG. 3 is a diagram showing a state where light receiving elements 227c receive light (FIGS. 2B and 2B). In the optical pickup unit 22 of the present embodiment, the interval (Pb) between the main beam mb, the sub beam sb1, and the sub beam sb2 in the radial direction of the optical disc 10 is set to be half of the track pitch (Pt). Yes.
Further, as shown in FIGS. 2B and 2B, the light receiving element 227a configured by the two-divided detector has light receiving areas a and b that are symmetrical in the drawing, and similarly, the light receiving element 227b is It is assumed that the light receiving areas c and d and the light receiving element 227c have light receiving areas e and f. For convenience, output values from the light receiving areas a, b, c, d, e, and f are also displayed as a, b, c, d, e, and f, respectively.

The tracking error detection unit 31 uses the output values a, b, c, d, e, and f from the light receiving areas a, b, c, d, e, and f as the following (1) It is obtained by performing an operation using an expression.
TE = (ab) -k * ((cd) + (ef)) (1)
In the equation (1), k is a light amount ratio between the main beam mb and the sub beam sb1 and the sub beam sb2. (2).
k = mb / (sb1 + sb2) (2)

In a state where the objective lens 21 is not shifted (FIG. 2B), when the main beam mb crosses the track, a push-pull signal (ab) of the return light of the main beam mb (hereinafter referred to as “main push”). The "pull signal" is a sine wave signal with a track pitch showing 0 at the center of the track as one cycle. The push-pull signal k × ((cd) + (ef)) (hereinafter referred to as “sub-push-pull signal”) of the return light of the sub-beams sb1 and sb2 has a phase of the main push-pull signal. The signal is inverted by 90 °.
On the other hand, when the objective lens 21 is in a lens shift state (FIG. 2C), the main push-pull signal is a sine wave signal with an offset, and the sub push-pull signal is the same amount as the main push-pull signal. This is a signal whose phase is shifted by 90 °.
Therefore, as shown in the equation (1), by subtracting the sub push-pull signal from the main push-pull signal, the tracking error signal TE from which the offset due to the lens shift of the objective lens 21 is removed is obtained.

Subsequently, the lens shift detection unit 32 outputs a lens shift signal LP corresponding to the shift amount of the objective lens 21 with respect to the optical pickup housing 22A by performing calculation using the following expression (3).
LP = (ab) + k * ((cd) + (ef)) (3)
As shown in the equation (3), by adding the sub push-pull signal to the main push-pull signal, a signal obtained by extracting only the offset component from which the tracking error signal component is removed can be obtained. Since the offset occurs with the lens shift, an output corresponding to the shift amount of the objective lens 21 can be obtained by calculation using the expression (3).

Incidentally, FIG. 3 is a diagram showing a change in the state of the laser light caused by the lens shift of the objective lens 21. In the optical pickup unit 22 of the present embodiment, a finite system is adopted as the optical system, and divergent light enters the objective lens 21 and is condensed and irradiated onto the optical disk 10. When the objective lens 21 is in a neutral state (FIG. 3A), the optical axis of the laser light incident on the objective lens 21 and the central axis of the objective lens 21 are set to coincide with each other. Therefore, when the objective lens 21 is in a neutral state, a good laser light focusing spot is formed on the surface of the optical disk 10.
However, when the objective lens 21 is shifted from the neutral state (FIG. 3B), an angle of view is generated, and the condensing spot of the laser beam on the surface of the optical disk 10 is distorted. When the laser beam condensing spot is thus distorted, as shown in FIG. 3, the amplitude of the tracking error signal (the amplitude at the time of crossing the track) decreases. A decrease in the amplitude of the tracking error signal causes a decrease in tracking error detection sensitivity (an output value with respect to the amount of deviation from the track).

Therefore, in the optical disc apparatus 1 according to the present embodiment, the first lens shift compensation unit 33 performs a process for suppressing a decrease in tracking error detection sensitivity even when the objective lens 21 is shifted from the neutral state.
Specifically, the first lens shift compensation unit 33 generates a first compensation gain corresponding to the tracking error detection sensitivity based on the lens shift signal output from the lens shift detection unit 32. Further, a corrected tracking error signal is generated by adding the generated first compensation gain to the tracking error signal generated by the tracking error detection unit 31. Then, the generated corrected tracking error signal is output to the tracking control unit 34.

FIG. 4 is a diagram showing the relationship between the lens shift amount of the objective lens 21, the tracking error detection sensitivity, the first compensation gain, and the corrected tracking error detection sensitivity. As shown in FIG. 4, the tracking error detection sensitivity T has a characteristic that decreases as the lens shift amount s of the objective lens 21 increases. Here, in the present embodiment, it is assumed that the relationship of the following equation (4) is roughly provided between the tracking error detection sensitivity T and the lens shift amount s.
T = −0.69s ² +0.28 (4)

In the case where the tracking error detection sensitivity T has a characteristic as expressed by the equation (4), the first lens shift compensation unit 33 uses the lens shift detection value s based on the lens shift signal input from the lens shift detection unit 32. And the calculated lens shift detection value s as a variable is calculated using the following equation (5) to obtain the first compensation gain G1.
G1 = 0.28 / (− 0.69s ² +0.28) (5)

As described above, the first lens shift compensator 33 corrects the tracking error signal hTE corrected by integrating the generated first compensation gain G1 with the tracking error signal TE generated by the tracking error detector 31. Is generated. Therefore, the detection sensitivity hT of the corrected tracking error signal hTE in this case can be expressed by the following equation (6). That is,
hT = G1 × T
= [0.28 / (− 0.69 s ² +0.28)] × [−0.69 s ² +0.28]
= 0.28 (6)
It becomes.
Thus, in the first lens shift compensation unit 33 of the present embodiment, the sensitivity of the generated corrected tracking error signal hTE is constant regardless of the lens shift amount s of the objective lens 21.

  The corrected tracking error signal hTE generated in this way is output to the tracking control unit 34, and a tracking actuator drive signal is generated. Then, the actuator 23 is driven by the tracking actuator drive signal, and tracking control is executed. In this case, the tracking control unit 34 can generate an appropriate tracking actuator drive signal based on the corrected tracking error signal hTE in which the sensitivity decrease due to the lens shift amount s of the objective lens 21 is corrected. It is possible to stabilize the track pull-in operation.

Conventionally, the tracking control unit drives the actuator 23 based on the tracking error signal TE whose sensitivity decreases with the lens shift amount s of the objective lens 21. For this reason, if a lens shift occurs during the track pull-in operation, an excessive tracking actuator drive signal is generated from the excessive tracking error signal TE, and the track eccentric operation cannot be tracked and the track pull-in operation fails. There was a case.
On the other hand, in the optical disc apparatus 1 according to the present embodiment, an appropriate tracking actuator drive signal can be generated based on the corrected tracking error signal hTE in which the sensitivity decrease due to the lens shift amount s of the objective lens 21 is corrected. The track pull-in operation can be stabilized.

  As described above, in the optical disc apparatus 1 according to the present embodiment, the first lens shift compensation unit 33 has the first compensation gain G1 corresponding to the tracking error detection sensitivity T that decreases as the lens shift amount s increases. By generating and correcting the tracking error signal TE by the first compensation gain G1, a corrected tracking error signal hTE having a constant sensitivity is generated regardless of the lens shift amount s of the objective lens 21. Therefore, an appropriate tracking actuator drive signal can be generated regardless of the lens shift amount s of the objective lens 21, so that the track pull-in operation during tracking control can be stabilized.

[Embodiment 2]
In the optical disc apparatus 1 of the first embodiment, the case where the compensation gain corresponding to the tracking error detection sensitivity is generated and the tracking error signal is corrected has been described. In the optical disk device 2 according to the second embodiment, a case where a compensation gain corresponding to the actuator response sensitivity is generated and the tracking error signal is corrected will be described. Note that the description of the same configuration as in the first embodiment in the second embodiment is omitted.

  FIG. 5 is a block diagram showing a configuration of the optical disc apparatus 2 of the present embodiment. As shown in FIG. 5, in the optical disk device 2 of the present embodiment, a second lens shift as an example of a lens shift compensation unit is used instead of the first lens shift compensation unit 33 in the optical disk device 1 of the first embodiment. A compensation unit 35 is provided. Other configurations of the optical disc apparatus 2 are the same as those of the optical disc apparatus 1 according to the first embodiment.

  FIG. 6 is a diagram illustrating a state of the actuator 23 when the objective lens 21 is shifted. As shown in FIG. 6, in the actuator 23, the movable portion 231 on which the objective lens 21, the first coil 235, and the second coil 236 are mounted is supported on the fixed portion 237 by the support wire 232. Since the support wire 232 is elastically deformable, the objective lens 21 is movable in the tracking direction (arrow A in FIG. 5). The first magnet 233 and the second magnet 234 are mounted on the fixed portion 237. When the objective lens 21 is in a neutral state (FIG. 6A), the first magnet 233 is installed at a position where the center position thereof coincides with the center position of the first coil 235. Similarly, the second magnet 234 is installed at a position where the center position thereof coincides with the center position of the second coil 236. When the first coil 235 and the second coil 236 are energized in this state, thrust is generated by the magnetic interaction with the first magnet 233 and the second magnet 234, and acceleration is generated in the movable portion 231.

  However, when acceleration is generated in the movable portion 231 and the objective lens 21 is shifted from the neutral state (FIG. 6B), the first coil 235 and the second coil 236 are also shifted, and the first magnet 233 and the second magnet 233 are respectively shifted. The magnet 234 is moved away from the center position. When the first coil 235 and the second coil 236 move away from the center positions of the first magnet 233 and the second magnet 234, respectively, the density of the magnetic flux passing through the first coil 235 and the second coil 236 decreases. As a result, the response sensitivity of the actuator 23 (acceleration with respect to the current supplied to the first coil 235 and the second coil 236) decreases.

Therefore, in the optical disc apparatus 2 according to the present embodiment, the first lens shift compensation unit 35 performs a process for suppressing a decrease in response sensitivity of the actuator 23 even when the objective lens 21 is shifted from the neutral state.
Specifically, the second lens shift compensation unit 35 generates a second compensation gain corresponding to the response sensitivity of the actuator 23 based on the lens shift signal output from the lens shift detection unit 32. Further, a corrected tracking error signal is generated by integrating the generated second compensation gain to the tracking error signal generated by the tracking error detection unit 31. Then, the generated corrected tracking error signal is output to the tracking control unit 34.

FIG. 7 is a diagram showing the relationship between the lens shift amount of the objective lens 21, the response sensitivity of the actuator 23 (actuator response sensitivity), the second compensation gain, and the corrected actuator response sensitivity. As shown in FIG. 7, the actuator response sensitivity A has a characteristic that decreases as the lens shift amount s of the objective lens 21 increases. Here, in the present embodiment, it is assumed that the relationship between the actuator response sensitivity A and the lens shift amount s is roughly represented by the following equation (7).
A = −200 s ² +400 (7)

In the case where the actuator response sensitivity A has a characteristic as expressed by the equation (7), the second lens shift compensation unit 35 calculates the lens shift detection value s based on the lens shift signal input from the lens shift detection unit 32. The second compensation gain G2 is obtained by calculating and calculating the detected lens shift value s as a variable using the following equation (8).
G2 = 0.55s ² +1 (8)

Then, the second lens shift compensator 35 generates a corrected tracking error signal by integrating the generated second compensation gain with the tracking error signal TE generated by the tracking error detector 31. Thereby, the corrected tracking error signal is increased as the lens shift amount of the objective lens 21 is increased, and the decrease in the actuator response sensitivity A can be compensated.
Here, in FIG. 7, the integrated value of the actuator response sensitivity A and the second compensation gain G2 is shown as a corrected actuator response sensitivity hA. As shown in FIG. 7, in the corrected actuator response sensitivity hA, the decrease in the actuator response sensitivity A accompanying the lens shift is compensated, and shows a substantially constant value.

  Thereafter, the corrected tracking error signal output from the second lens shift compensation unit 35 is output to the tracking control unit 34, and a tracking actuator drive signal is generated. Then, the actuator 23 is driven by the tracking actuator drive signal, and tracking control is executed. In this case, since the tracking control unit 34 can generate an appropriate tracking actuator drive signal based on the corrected tracking error signal in which the decrease in actuator response sensitivity is compensated, the tracking pull-in operation is stabilized during tracking control. It becomes possible.

Conventionally, the tracking control unit drives the actuator 23 based on the tracking error signal TE with respect to the actuator 23 whose sensitivity decreases with the lens shift amount s of the objective lens 21. For this reason, if a lens shift occurs during the track pull-in operation, acceleration may be insufficient due to an excessive response, and the track pull-in operation may fail.
On the other hand, in the optical disk device 2 of the present embodiment, the actuator 23 is controlled based on the corrected tracking error signal that has been increased so as to compensate for the response sensitivity decrease due to the lens shift amount s of the objective lens 21. Yes. Therefore, an appropriate response can be obtained, and the track pull-in operation can be stabilized.

[Embodiment 3]
In the optical disk device 3 according to the third embodiment, both the correction of the tracking error signal based on the compensation gain corresponding to the tracking error detection sensitivity and the correction of the tracking error signal based on the compensation gain corresponding to the actuator response sensitivity are performed. Will be explained. Note that the description of the same configuration as in the first embodiment in the third embodiment is omitted.

  FIG. 8 is a block diagram showing a configuration of the optical disc apparatus 3 according to the present embodiment. As shown in FIG. 8, in the optical disk apparatus 3 according to the present embodiment, the second lens shift compensation section 35 according to the second embodiment is provided after the first lens shift compensation section 33 in the optical disk apparatus 1 according to the first embodiment. Is arranged. The other configuration of the optical disc apparatus 3 is the same as that of the optical disc apparatus 1 of the first embodiment.

As in the first embodiment, the first lens shift compensation unit 33 generates a first compensation gain corresponding to the tracking error detection sensitivity based on the lens shift signal output from the lens shift detection unit 32. Then, the first corrected tracking error signal is generated by adding the generated first compensation gain to the tracking error signal generated by the tracking error detection unit 31.
Similarly to the second embodiment, the second lens shift compensation unit 35 generates a second compensation gain corresponding to the response sensitivity of the actuator 23 based on the lens shift signal output from the lens shift detection unit 32. Then, the second corrected tracking error signal is generated by adding the generated second compensation gain to the first corrected tracking error signal output from the first lens shift compensation unit 33.

  Thereafter, the second corrected tracking error signal generated by the second lens shift compensation unit 35 is output to the tracking control unit 34, and a tracking actuator drive signal is generated. Then, the actuator 23 is driven by the tracking actuator drive signal, and tracking control is executed. In this case, the tracking control unit 34 can generate an appropriate tracking actuator drive signal based on the second corrected tracking error signal in which both the decrease in tracking error detection sensitivity and the decrease in actuator response sensitivity are compensated. It is possible to further stabilize the track pull-in operation during control.

[Embodiment 4]
In the optical disk device 4 according to the fourth embodiment, a case will be described in which the tracking error signal is corrected based on the compensation gain corresponding to the cumulative sensitivity obtained by integrating the tracking error detection sensitivity and the actuator response sensitivity. Note that the description of the same configuration as that of the first embodiment in the fourth embodiment is omitted.

FIG. 9 is a block diagram showing a configuration of the optical disc apparatus 4 of the present embodiment. As shown in FIG. 9, in the optical disk device 4 of the present embodiment, a third lens shift as an example of a lens shift compensation unit is used instead of the first lens shift compensation unit 33 in the optical disk device 1 of the first embodiment. A compensation unit 36 is provided. The other configuration of the optical disc apparatus 4 is the same as that of the optical disc apparatus 1 of the first embodiment. The actuator 23 has a lens shift characteristic similar to that shown in the second embodiment.
Based on the lens shift signal output from the lens shift detector 32, the third lens shift compensator 36 generates a third compensation gain corresponding to the cumulative sensitivity obtained by integrating the tracking error detection sensitivity and the actuator response sensitivity. Further, a corrected tracking error signal is generated by adding the generated third compensation gain to the tracking error signal generated by the tracking error detection unit 31. Then, the generated corrected tracking error signal is output to the tracking control unit 34.

FIG. 10 is a diagram showing the relationship between the lens shift amount of the objective lens 21, the cumulative sensitivity obtained by integrating the tracking error detection sensitivity and the actuator response sensitivity, the third compensation gain, and the corrected cumulative sensitivity. Both the tracking error detection sensitivity and the actuator response sensitivity have characteristics that decrease as the lens shift amount s of the objective lens 21 increases. Therefore, as shown in FIG. 10, the cumulative sensitivity obtained by integrating the tracking error detection sensitivity and the actuator response sensitivity shows a further significant decreasing tendency.
Therefore, the third lens shift compensation unit 36 of the present embodiment calculates the lens shift detection value s based on the lens shift signal input from the lens shift detection unit 32, and the calculated lens shift detection value s. Is used as a variable to calculate the third compensation gain G3 using the following equation (9).
G3 = 29s ⁴ +1 (9)

Then, the third lens shift compensator 36 generates a corrected tracking error signal by integrating the generated third compensation gain with the tracking error signal TE generated by the tracking error detector 31. As a result, the corrected tracking error signal has a value that is corrected to compensate for the decrease in tracking error detection sensitivity caused by the lens shift of the objective lens 21 and that compensates for the decrease in actuator response sensitivity. .
Therefore, the cumulative sensitivity is corrected to the corrected cumulative sensitivity in which the decrease due to the lens shift is suppressed by integrating the third compensation gain. As a result, as shown in FIG. 10, the corrected cumulative sensitivity has a substantially constant value.

  Thereafter, the corrected tracking error signal output from the third lens shift compensator 36 is output to the tracking controller 34, and a tracking actuator drive signal is generated. Then, the actuator 23 is driven by the tracking actuator drive signal, and tracking control is executed. In this case, the tracking controller 34 can generate an appropriate tracking actuator drive signal based on the corrected tracking error signal in which both the decrease in tracking error detection sensitivity and the decrease in actuator response sensitivity are compensated. It is possible to further stabilize the track pull-in operation.

[Embodiment 5]
In the first to fourth embodiments, a compensation gain corresponding to tracking error detection sensitivity, actuator response sensitivity, etc. is generated, and a corrected tracking error signal is generated by integrating the compensation gain with respect to the tracking error signal. The optical disk apparatus for performing the control has been described. In the optical disk device 5 according to the fifth embodiment, a case where the tracking error signal is corrected by the configuration of the actuator will be described. Note that the description of the same configuration as in the first embodiment in the fifth embodiment is omitted.

  FIG. 11 is a block diagram showing a configuration of the optical disc apparatus 5 of the present embodiment. As shown in FIG. 11, the optical disc apparatus 5 of the present embodiment has a configuration in which the lens shift detection unit 32 and the first lens shift compensation unit 33 in the optical disc apparatus 1 of the first embodiment are not provided. ing. The other configuration of the optical disc apparatus 5 is the same as that of the optical disc apparatus 1 of the first embodiment. Note that the tracking error detection unit 31 generates a tracking error signal by the operation push-pull method as in the first embodiment. Further, the lens shift characteristic shown in FIG. 14 described later is provided.

  FIG. 12 is a schematic diagram showing the configuration of the actuator 23 mounted on the optical disc apparatus 5 of the present embodiment. In the actuator 23 of the present embodiment shown in FIG. 12, unlike the actuator 23 of the second embodiment shown in FIG. 6, the first magnet 233 and the second magnet 234 include the objective lens 21, the first coil 235, and the first coil 235. The movable part 231 on which the two coils 236 are mounted is disposed outside the tracking direction (arrow A in FIG. 11). That is, when the objective lens 21 is in a neutral state (FIG. 12A), the center position of the first magnet 233 is shifted to the right side from the center position of the first coil 235 in the paper surface of FIG. Are arranged to be. Further, the center position of the second magnet 234 is arranged so as to be shifted to the left side from the center position of the second coil 234.

  FIG. 13 shows the response sensitivity of the first coil 235 and the response sensitivity of the second coil 236 in the actuator 23 of the present embodiment, and further, the total of the first actuator 235 and the second coil 236. It is the figure which showed the response sensitivity (actuator response sensitivity). The first magnet 233 and the second magnet 234 are disposed on the outer side in the tracking direction with respect to the first coil 235 and the second coil 236, respectively. Therefore, as shown in FIG. 13, in the first coil 235, the response sensitivity is maximized when the objective lens 21 is shifted to the right (FIG. 12B), and in the second coil 236, the objective lens 21 is Response sensitivity is maximized when shifted to the left. As a result, the actuator 23 of the present embodiment exhibits a characteristic that the actuator response sensitivity increases as the lens shifts.

FIG. 14 is a diagram showing the relationship between the lens shift amount of the objective lens 21, the tracking error detection sensitivity, the actuator response sensitivity, the cumulative sensitivity obtained by integrating the tracking error detection sensitivity and the actuator response sensitivity. Note that the cumulative sensitivity is shown in FIG. 14 so that the cumulative sensitivity is quadrupled.
As shown in FIG. 14, the tracking error detection sensitivity has a characteristic that decreases as the lens shift amount s of the objective lens 21 increases. However, since the actuator 23 of the present embodiment is set so that the actuator response sensitivity increases with the increase of the lens shift amount s, the cumulative sum of the tracking error detection sensitivity and the actuator response sensitivity is accumulated. Sensitivity fluctuations can be suppressed low.

  As described above, in the optical disk device 5 according to the present embodiment, it is possible to suppress fluctuations in the loop gain in spite of employing the tracking error detection unit 31 in which the tracking error detection sensitivity decreases with lens shift. . As a result, the tracking control unit 34 can generate an appropriate tracking actuator drive signal based on the tracking error signal in which a decrease in tracking error detection sensitivity is suppressed to a low level, thereby stabilizing the track pull-in operation during tracking control. It becomes possible.

[Embodiment 6]
In the optical disc apparatus 1 of the first embodiment, the case where the compensation gain corresponding to the tracking error detection sensitivity is generated and the tracking error signal is corrected has been described. In the optical disk device 6 according to the sixth embodiment, a configuration in which a constant included in a calculation for generating a compensation gain can be set will be described. Note that the description of the same configuration as in the first embodiment in the second embodiment is omitted.

  FIG. 15 is a block diagram showing a configuration of the optical disc apparatus 6 according to the present embodiment. As shown in FIG. 15, in the optical disc device 6 of the present embodiment, the calculation for generating the first compensation gain executed by the first lens shift compensation unit 33 in the optical disc device 1 of the first embodiment. Are additionally provided with a constant setting unit 37 as an example of response characteristic setting means for setting constants included in the circuit and a switch 40 for switching circuits. The other configuration of the optical disc apparatus 6 is the same as that of the optical disc apparatus 1 of the first embodiment.

  Here, a procedure of processing when the constant setting unit 37 sets constants will be described. FIG. 16 is a flowchart for explaining a processing procedure when the constant setting unit 37 sets a constant. For the description of the processing procedure, refer to FIG. 17 showing the relationship between the lens shift amount of the objective lens 21, the tracking error detection sensitivity, the first compensation gain, and the corrected tracking error detection sensitivity. In this process, the switch 40 is set to be connected to the terminal B, and the tracking control unit 34 is opened.

First, when the optical disk 10 is loaded (S1), the optical disk 10 is rotated and focused (S2).
(Amplitude acquisition process)
Next, the constant setting unit 37 observes the lens shift signal from the lens shift detection unit 32, and drives the actuator 23 so that the lens shift detection value approaches 0 mm (S3).
When the lens shift detection value reaches 0 mm (S4), the tracking error signal amplitude P1 is detected from the tracking error detection unit 31, and the detection value is stored (S5). In the case of the present embodiment, amplitude P1 = 0.28 is detected (see FIG. 17).

Subsequently, the lens shift signal is observed from the lens shift detector 32, and the actuator 23 is driven so that the lens shift detection value approaches the predetermined value u (S6). In this embodiment, u = 0.4 mm is set.
When the lens shift detection value reaches u = 0.4 mm (S7), the tracking error signal amplitude P2 is detected from the tracking error detector 31, and the detected value is stored (S8). In the present embodiment, P2 = 0.17 is detected (see FIG. 17).

(Set value calculation process)
Then, the stored P1 and P2 are read, and the calculation according to the following equation (10) is performed.
k2 = (P2-P1) / u ²
= (0.17-0.28) /0.4 ² = -0.69 (10)
The first lens shift compensation unit 33 includes a calculation unit, and the calculation unit includes a variable constant P1 and a variable constant k2 as shown in the following equation (11).
G1 = P1 / (k2 × s ² + P1) (11)
The constant setting unit 37 sets the calculation result k2 = −0.69 and the detection result P1 = 0.28 to the equation (11), and the following equation (12) is obtained.
^{G1 = 0.28 / (- 0.69s 2} +0.28) ... (12)

(Constant setting process)
Then, the constant setting unit 37 sets the obtained equation (12) in the first lens shift compensation unit 33 (S9). Thereby, the setting of the constant by the constant setting unit 37 is completed (S10).

  Next, when the constant setting to the first lens shift compensation unit 33 by the constant setting unit 37 is completed, the switch 40 is set to be connected to the terminal C, and the tracking control unit 34 is set to a closed state. Then, tracking control is performed in the same manner as described in the first embodiment.

As described above, in the optical disc device 6 according to the present embodiment, even when the lens shift characteristic of the tracking error detection sensitivity fluctuates due to the temporal change of the optical pickup unit 22, the calculation error is reduced by resetting the calculation constant. It becomes possible to do.
In addition, the lens shift characteristic may vary depending on the optical disk 10 to be mounted. However, by changing the setting of the arithmetic constant every time the optical disk 10 is replaced, the variation due to the difference of the optical disk 10 to be mounted can be obtained. It becomes possible to suppress.

1 is a block diagram illustrating a configuration of an optical disc device according to a first embodiment. It is the figure which showed the state in which the optical disk surface is irradiated with the laser beam, and the state in which the light receiving element receives the return light. It is the figure which showed the change of the state of the laser beam which arises by the lens shift of an objective lens. It is the figure which showed the relationship between the lens shift amount of an objective lens, tracking error detection sensitivity, 1st compensation gain, and corrected tracking error detection sensitivity. 6 is a block diagram illustrating a configuration of an optical disc device according to a second embodiment. FIG. It is the figure which showed the state of the actuator at the time of shifting an objective lens. It is the figure which showed the relationship between the lens shift amount of an objective lens, an actuator response sensitivity, a 2nd compensation gain, and the corrected actuator response sensitivity. 6 is a block diagram illustrating a configuration of an optical disc device according to Embodiment 3. FIG. FIG. 10 is a block diagram illustrating a configuration of an optical disc device according to a fourth embodiment. It is the figure which showed the relationship between the lens shift amount of an objective lens, the cumulative sensitivity which integrated tracking error detection sensitivity, and actuator response sensitivity, the 3rd compensation gain, and the corrected cumulative sensitivity. FIG. 10 is a block diagram illustrating a configuration of an optical disc device according to a fifth embodiment. It is the schematic which showed the structure of the actuator. It is the figure which showed the response sensitivity of the 1st coil in an actuator, the response sensitivity of a 2nd coil, and also the comprehensive response sensitivity of the actuator which totaled the 1st coil and the 2nd coil. It is the figure which showed the relationship between the lens shift amount of an objective lens, tracking error detection sensitivity, actuator response sensitivity, and the cumulative sensitivity which integrated tracking error detection sensitivity and actuator response sensitivity. FIG. 10 is a block diagram illustrating a configuration of an optical disc device according to a sixth embodiment. It is a flowchart explaining the procedure of the process at the time of a constant setting part setting a constant. It is the figure which showed the relationship between the lens shift amount of an objective lens, tracking error detection sensitivity, 1st compensation gain, and corrected tracking error detection sensitivity.

Explanation of symbols

1, 2, 3, 4, 5, 6 optical disk device,
10 optical disks, 21 objective lenses,
22 Optical pickup section (optical pickup),
22A optical pickup housing,
23 Actuator, 24 Seek motor, 25 Spindle motor,
31 Tracking error detector, 32 Lens shift detector,
33 First lens shift compensation unit, 34 Tracking control unit 35 Second lens shift compensation unit, 36 Third lens shift compensation unit,
37 Constant setting section, 40 switches.

Claims (2)

An optical pickup that irradiates light onto an optical disk on which a track is formed, and writes and / or reads data;
An objective lens for condensing the light emitted from the optical pickup as a light spot on the optical disc;
Driving means for driving the objective lens in the radial direction of the optical disc with respect to the optical pickup;
Tracking error detection means for detecting a deviation between the light spot collected on the optical disc and the track;
Tracking control means for controlling the driving means based on the tracking error signal output by the tracking error detection means;
With
The change characteristic of the detection sensitivity of the tracking error detection means, which decreases as the lens shift amount increases, and the change characteristic of the response sensitivity of the drive means accompanying the movement of the objective lens are set to be reversed. An optical disc apparatus characterized by the above. The optical pickup includes a movable portion on which the objective lens is mounted, and a fixed portion attached via a support wire that is elastically deformed so that the movable portion can move in the tracking direction.
The driving means includes
Two sets of a coil fixed to the movable part and a magnet fixed to the fixed part so as to face the coil are arranged at intervals in the tracking direction,
When the distance between the centers of the two magnets in the tracking direction is longer than the distance between the centers of the two coils in the tracking direction, and when the movable part is in a neutral state, 2. The optical disc apparatus according to claim 1, wherein the two sets of magnets are arranged so as to be located outside the tracking direction.

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