JP2008140420A - Tracking servo device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking servo device capable of enhancing tracking accuracy after sufficiently assuring stability without raising a servo band. <P>SOLUTION: An eccentricity signal generation section 4 generates the eccentricity signal ES based on the tracking error signal obtained in the state of not applying tracking servo from a tracking actuator 12 which performs tracking for the information tracks of a disk-shaped optical recording medium. An eccentricity servo section 14 performs the eccentricity servo based on the eccentricity signal ES generated by the eccentricity signal generation section 4. A tracking servo section 15 performs the tracking servo in the amount remaining after servo taking by the eccentricity servo section 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tracking servo device that performs tracking servo when an information signal is recorded / reproduced on / from a disk-shaped recording medium.

  Conventionally, as disclosed in Patent Document 1 below, in tracking control of an optical disc, a bias value for compensating an offset value for a tracking error signal can be set optimally. Conventionally, the following patent document 1 is filed. For tracking error signals, the traverse signal is passed through a low-pass filter to obtain the center value of the traverse signal, which is used as the bias value. However, the frequency of the traverse signal obtained by the eccentricity of the disk varies greatly. For this reason, how to set the cutoff frequency of the low-pass filter has been a problem. In Patent Document 1 below, the center value of the traverse signal is extracted from the output of the optical information reading means while rotating the optical disk and moving the optical information reading means in the radial direction of the optical disk.

JP-A-8-279170

  By the way, in recent years, as the density of an optical disk, a magneto-optical disk, or the like, which is a specific example of a disk-shaped recording medium, is increased, the interval between tracks such as a record mark row has been reduced. In order to cause the light beam to correctly follow the recording mark row and the pit row whose intervals have become narrower, the disc eccentricity specification and servo specification have become stricter.

  For example, a compact disc (CD) with a disc size of 12 cm in diameter and a user recording capacity of 640 Mbytes has a track pitch of 1.6 μm and an allowable residual error of about 60 nmpp for an allowable eccentricity of 140 μmpp. . However, in a high-density optical disk using a short wavelength laser with a user recording capacity of 25 Gbyt, the track pitch is 0.32 μm, and the allowable residual error is about 18 nmpp for an allowable eccentricity of 50 μmpp. Yes.

  Thus, as the user recording capacity increases, the track pitch decreases and the allowable residue error also decreases. In response to this problem, it is conceivable to increase the servo band and suppress the allowable eccentricity.

  In other words, the servo band of compact disks is about 1 kHz, whereas the high-density optical disk using the short wavelength laser has a high servo band up to 3 kHz. For this reason, it is difficult to solve the problem simply by increasing the servo bandwidth. Therefore, it was considered to suppress the allowable eccentricity of the disk. For example, when comparing a compact disc with a high-density optical disc using the short wavelength laser, the compact disc has an allowable eccentricity of 140 μm, whereas a high-density optical disc using the short wavelength laser has an allowable disc eccentricity of only 50 μm. There is no.

  In addition, since the allowable eccentricity is suppressed and strictly limited, demands for disc molding accuracy, clamping accuracy, and motor shaft runout accuracy are becoming stricter. This also contributes to an increase in manufacturing cost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tracking servo device that can increase the tracking accuracy while ensuring sufficient stability without increasing the servo band. It is another object of the present invention to provide a tracking servo device that can increase the margin of allowable eccentricity.

  In order to solve the above problems, a tracking servo apparatus according to the present invention provides an optical head means for recording / reproducing information by irradiating a beam on a disk-shaped optical recording medium with respect to an information track of the disk-shaped optical recording medium. An eccentric signal generating means for generating an eccentric signal based on a tracking error signal obtained without tracking servo from a tracking actuator to be tracked, and an eccentric signal generated by the eccentric signal generating means are used. Eccentric servo means, and tracking servo means for performing tracking servo with the amount of remaining servo by the eccentric servo means.

  In this tracking servo apparatus, the eccentric servo means has a first control filter for inputting the eccentric signal, and feeds the servo remaining amount by the first control filter to the tracking servo means. Feed forward.

  The tracking servo means includes a second control filter to which the tracking error signal is input, a tracking actuator to which a filter output of the second control filter is input, and further the second control filter and the A tracking servo switch for turning on or off the tracking servo is provided between the tracking actuator and the tracking actuator.

  The eccentric servo means may feed the eccentric signal to the tracking servo means in a feedforward manner, and the tracking servo means may drive the tracking actuator by a common control filter.

  Thus, the tracking servo device of the present invention generates a disc eccentric signal from the tracking error in the optical disc, and stores the eccentric signal for one rotation. Then, the eccentric signal for one rotation is applied as a feed forward signal to the tracking servo section. The conventional tracking servo is performed with the servo remaining amount by the eccentric signal. Thus, tracking accuracy can be improved by performing tracking with the two-stage servo of the loop based on the eccentric signal and the loop based on the tracking signal.

  According to the present invention, the tracking accuracy can be improved without increasing the bandwidth of the tracking servo section. Further, according to the present invention, it is possible to increase the margin of the allowable eccentricity amount while maintaining the tracking accuracy.

  According to the present invention, an eccentricity signal is generated from a tracking error signal, and a two-stage servo configuration with an eccentricity servo based on the eccentricity signal (coarse tracking servo) and a tracking servo based on a tracking error (fine tracking error servo) is made. Thus, it is possible to increase the tracking accuracy while ensuring sufficient stability without increasing the signal servo band. In addition, it is possible to increase the margin for the allowable eccentricity.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first specific example of a tracking servo apparatus according to the present invention. The tracking servo device 1 includes an eccentric signal generation unit 4, an eccentric servo unit 14, and a tracking servo unit 15. In particular, in the first specific example, the eccentric servo unit 14 and the tracking servo unit 15 operate independently.

  The eccentric signal generation unit 4 generates an eccentric signal based on a tracking error signal obtained without tracking servo from the tracking actuator 12 that tracks the optical spot of the optical head with respect to the information track of the disk-shaped optical recording medium. Create an ES. The eccentric servo unit 14 performs eccentric servo based on the eccentric signal ES generated by the eccentric signal generation unit 4. The tracking servo unit 15 performs tracking servo with the remaining servo removal amount by the eccentric servo unit 14.

  The eccentric servo unit 14 has a control filter (C ′) 7 that receives the eccentric signal ES and performs eccentric control, and feeds the servo remaining amount by the control filter 7 to the tracking servo unit 15 in a feedforward manner. .

  The tracking servo unit 15 includes a control filter (C) 9 that performs tracking control when the tracking error signal is input, a tracking actuator 12 that receives a filter output of the control filter 9, and a control filter 9 and a tracking actuator 12. A tracking servo switch 10 for turning on or off the tracking servo is provided between the two. Switching of the tracking servo switch 10 is controlled according to a switch control signal supplied from the control signal input terminal 11.

  The tracking servo device 1 is given a target value r of the tracking error signal from the input terminal 2 with the tracking servo switch 10 turned on. This target value r is supplied to the subtracter 3. The subtracter 3 is also supplied with a tracking error signal TES from a tracking actuator 12 to be controlled (P) described later. The subtracter 3 subtracts the tracking error signal TES from the target value r of the tracking signal and supplies the difference signal to the control filter 9 as a subtraction output.

  Before the tracking servo switch 10 is turned on, the eccentric signal generation unit 4 is supplied from an unillustrated system controller via an octopus signal which is an FG (frequency generator) signal supplied from the input terminal 5 and the control terminal 6. An eccentric signal is generated from the tracking error signal based on the eccentric servo switch signal. The tracking error signal before the switch 10 is turned on is a tracking error signal obtained in a state in which the tracking servo is not applied from the tracking actuator 12 that tracks the optical head unit with respect to the information track of the optical disk. Details of the generation process of the eccentric signal ES by the eccentric signal generation unit 4 will be described later.

  The eccentric signal ES generated by the eccentric signal generation unit 4 is supplied to the control filter 7. The control filter 7 performs eccentric servo based on the eccentric signal ES, and supplies a servo remaining signal to the tracking servo unit 15.

  As described above, the tracking servo apparatus 1 in FIG. 1 feeds the output signal from the eccentric signal generation unit 4 (the eccentric signal ES detected from the tracking error signal TES) to the tracking actuator 12 through the appropriate control filter 7. It is to forward.

  This feedforward loop is referred to as an eccentric servo loop 14. When feedforward is performed, the polarities of the eccentricity signal and the drive signal are adjusted so that the tracking error signal is reduced by the eccentricity signal (the same applies hereinafter).

  The tracking actuator 12 supplies a tracking error signal TES to the output terminal 13 and feeds it back to the subtractor 3 through the feedback loop 16.

  After the tracking servo switch 10 is turned on, the tracking servo unit 15 controls the tracking actuator 12 while adding the servo remaining amount by the eccentric servo unit 14 to the filter output of the control filter 9, and the tracking actuator 12 Tracking servo is performed while feeding back the tracking error signal TES via (feedback loop 16).

  Since the eccentric servo unit 14 causes the head to substantially follow the eccentricity, the tracking servo unit 15 only has to deal with a tracking error that cannot be followed by the eccentric servo unit 14. In this case, when viewed from the tracking error loop, the tracking servo is performed with respect to a disk with very little eccentricity, so that a servo band is not required as compared with the tracking servo unit 15 alone. On the contrary, if the servo band is made the same as that of the tracking servo unit 15 alone, the tracking accuracy is improved.

  However, as an operation sequence, the eccentric servo is first, and then the tracking servo is performed. This is because if the tracking servo is turned on first, a tracking error signal cannot be obtained and an eccentricity signal cannot be generated.

  Further, by adopting a two-stage servo configuration with coarse tracking by the eccentric servo unit 14 and fine tracking by the tracking servo unit 15, the allowable eccentricity amount can be increased. That is, if the allowable eccentricity in the case of the tracking servo unit 15 alone is Δ, the allowable residual error amount in the eccentric servo loop by the eccentric servo unit 14 is Δ, and the allowable eccentricity in the eccentric servo loop is The amount Δ ′ is larger than Δ by the gain of the eccentric servo loop. That is, the allowable eccentricity can be increased as a whole.

  Next, the tracking error signal TES that is the basis for the eccentric signal generation unit 4 to generate the eccentric signal ES in the tracking servo apparatus 1 will be described. In particular, the principle for generating the eccentric signal ES from the tracking error signal TES will be described.

  FIG. 2 shows the waveform of the tracking error signal TES in the optical disc. The horizontal axis represents time, and the vertical axis represents the tracking error signal level. It is a waveform of the tracking error signal TES for one rotation of the disk.

  FIG. 3 shows the relationship between the tracking error signal TES and the disk eccentricity shown in FIG. In FIG. 3, A → B → C → D, and the disk is rotated once. For example, suppose that A is the peak value (r + Δ; r: radius, Δ: center deviation amount) of the deviation between the rotation center of the disk and the center of the disk (the center of the spiral of the recording signal).

  FIG. 4 is an enlarged view of the tracking error near A. At A, since the deviation from the tracking position due to the position of the true disk center is the largest, the track pitch is apparently widened. Therefore, as shown in FIG. 4, the frequency of the tracking error is low at the peak of the deviation.

  Next, at B in FIG. 3, the discrepancy between the disc rotation center and the disc center is the smallest. FIG. 5 is an enlarged view of the tracking error in the vicinity of B. At B, the deviation from the tracking position due to the true disk center position is minimized, and a tracking error corresponding to the original track pitch is obtained. Therefore, the frequency of tracking error becomes high as shown in FIG. For example, when the discrepancy between the disc rotation center and the disc center is zero, that is, when they completely match, the maximum frequency is reached.

  Next, at C in FIG. 3, the deviation between the disc rotation center and the disc center takes the peak value (r−Δ) again. Even at C, since the deviation from the tracking position due to the position of the true disk center is the largest, the track pitch is apparently widened. Therefore, like A, the frequency of the tracking error is lowered as shown in FIG.

  Next, in FIG. 3D, the discrepancy between the disc rotation center and the disc center is minimized again. Also at D, like B, the deviation from the tracking position due to the position of the true disk center is minimized, and a tracking error corresponding to the original track pitch is obtained. Therefore, like B, the frequency of the tracking error is high as shown in FIG. 5 (the maximum frequency is obtained when the discrepancy between the disc rotation center and the disc center is zero, that is, when they completely match).

  Finally, the position returns to the position A again, and the disk becomes one round. Thereafter, the states A, B, C, and D are repeated. The portions between A, B, C, and D are transition portions of the respective states, and the tracking error frequency continuously changes from a high frequency to a low frequency. Eventually, a tracking error signal TES as shown in FIG. 2 is obtained.

  Next, the configuration and operation of the eccentric signal generation unit 4 will be described in detail. FIG. 6 shows the internal configuration of the eccentric signal generation unit 4. A low-pass filter 21 that passes a low-frequency component of the tracking error signal TES input via the input terminal 20, a peak detector 22 that detects a peak of the low-frequency component signal from the low-pass filter 21, and a peak detector 22 An inversion mask generation unit 23 that generates an inversion mask from the detected peak, and an ES generation unit 24 that generates an ES signal from the peak of the peak detector 22 using the inversion mask generated by the inversion mask generation unit 23 are provided. .

  The low-pass filter 21 is a specific example of low-frequency extraction means that extracts a low frequency corresponding to the maximum eccentricity portion of the tracking error signal TES for one rotation of the disk. The peak detector 22 detects the envelope after making the low-frequency output extracted by the low-pass filter 21 only a half wave. The inversion mask generation unit 23 generates an inversion mask from the peaks detected by the peak detector 22. The ES generator 24 generates an ES signal from the peak of the peak detector 22 using the inversion mask generated by the inversion mask generation unit 23.

  Further, the eccentric signal generating unit 4 further includes an eccentric signal holding unit 25 that holds the generated eccentric signal ES for one rotation of the disk. The eccentric signal holding unit 25 holds the eccentric signal ES for one rotation of the disk before turning on the tracking servo unit 15. This is because if the tracking servo is turned on first, the tracking error signal TES as shown in FIG. 2 cannot be obtained and the eccentric signal ES cannot be generated.

  The eccentricity signal holding unit 25 is closed when the eccentricity servo switch signal is turned off and off, and the switch 26 is opened when the eccentricity servoswitch signal is turned on and off. A memory unit 27 that stores one rotation of the disk and a switch 28 that opens when the eccentric servo switch signal is turned off and closes when the eccentric servo switch signal is turned on and off are provided. When the switch 28 is closed, the eccentric signal ES is read from the memory unit 27 and supplied to the output terminal 29. The closing and opening of the switch 26 and the switch 28 are different from each other. This is because the tracking error signal becomes almost zero when the eccentric servo section 14 is turned on, and the tracking error signal as shown in FIG. 2 cannot be observed and the eccentric error signal cannot be generated correctly. Because.

  FIG. 7 is a diagram showing signal waveforms output by the respective units of the eccentric signal generation unit 4 shown in FIG. As shown in FIG. 7A, the tracking error signal TES input through the input terminal 20 repeats from eccentricity to sparseness and honey according to one rotation of the disk. When this is passed through the low-pass filter 21, the high-frequency component corresponding to the honey portion is removed, and only the low-frequency component corresponding to the sparse portion passes, and the positive and negative peaks are at positions corresponding to the sparse portion as shown in FIG. Envelope waveform that can be

  More specifically, when the tracking error signal (TES) is passed through an appropriate low-pass filter 21, as described with reference to FIG. 2, the tracking error frequency varies depending on the amount of eccentricity during one rotation. Therefore, a signal as shown in FIG. 7B is obtained.

  That is, at the maximum eccentricity, the tracking error signal has a low frequency, so that the signal amplitude is detected without being attenuated. On the other hand, where the eccentricity is minimum, the tracking error signal has a high frequency, so that the signal amplitude is attenuated and detected. Therefore, the signal is as shown in FIG.

  This envelope waveform is supplied to the peak detector 22. Similarly to the half wave circuit, the peak detector 22 generates a positive half wave waveform from the envelope waveform as shown in FIG. That is, only the half wave (+ signal) is used for the signal of FIG. 7B, and peak detection (envelope detection) is performed, so that the waveform is only on the positive side as shown in FIG. 7C. Produces no signal.

  This half-wave waveform is supplied to the inversion mask generation unit 23 and the ES generation unit 24. The inversion mask generator 23 generates an inversion mask signal as shown in FIG. 7D with respect to the signal in FIG. Specifically, for example, as shown in FIG. 8, after the signal of FIG. 7C is A / D converted, the output y (n) is monitored, and y (n) <y (n−1) to y A point where the transition is made to (n)> y (n-1) is detected, a flag is set, and the mask signal is set to H. Then, the mask signal is set to L when the flag is raised. Thereafter, this operation may be toggled.

  In the ES generation unit 24, an eccentricity error signal (ES signal) (FIG. 7) is generated based on the inversion mask signal (FIG. 7D) generated by the inversion mask generation unit 23 and the peak detection signal (FIG. 7C). (E)) is generated. Specifically, it is only necessary to invert the peak detection signal (FIG. 7C) only in the section where the inversion mask signal (d) is H. The signal thus obtained becomes an error signal ES corresponding to the amount of eccentricity.

  The memory unit 27 stores the sampled eccentricity error ES by a pulse signal (for example, 1000 pulses per rotation) output from the tachometer according to the rotation. Specifically, like the eccentric signal holding unit 25 shown in FIG. 9, the count value of the pulse of the octopus signal counted by the counter 31 is used as the address value, and is supplied from the ES generation unit 24 via the input terminal 30. The eccentricity signal ES is stored in the memory unit 27. Specifically, the eccentric signal ES is opened by the switch 26 that opens when the eccentric servo switch signal (A) supplied via the control terminal 6 is ON, and the memory unit 27 is supplied with the address according to the ON signal. Written. Further, the eccentric servo switch signal (A) is read from the memory unit 27 through the switch 28 that opens when the eccentric servo switch signal (A) is off.

As shown in FIG. 10, the eccentric signal holding unit 25 is a delay line (multi-stage) using a delay unit Z ⁻ⁿ (n: the number of pulses per rotation. In this example, n = 1000) as the storage unit 33. (D-flip-flop) 33). The delay timing is an octopus signal.

  FIG. 11 shows a second specific example of the tracking servo device according to the present invention, and a tracking servo device 40 capable of independently operating the servo by the eccentric signal (eccentric servo) and the tracking servo unit. It is.

  The tracking servo device 40 is different from the tracking servo device 1 of the first specific example in that the first specific example has two control filters, that is, a control filter 7 and a control filter 9. The common control filter (C) 41 is used. That is, the eccentric signal ES of the eccentric signal generation unit 4 is fed forward to the tracking servo unit 15 and the tracking actuator 12 is driven by the common control filter 41.

  In other words, the eccentric servo unit 14 feeds forward the eccentric signal ES generated by the eccentric signal generation unit 4 to the tracking servo unit 15, and the tracking servo unit 15 uses the common control filter 41 to track the tracking actuator 12. Drive. Since other configurations and operations are the same as those of the first specific example, description thereof will be omitted.

  FIG. 12 shows a third specific example of the tracking servo device according to the present invention, which is a tracking servo device capable of independently operating the servo by the eccentric signal (eccentric servo) and the tracking servo unit. 42.

  The tracking servo device 42 is different from the tracking servo device 40 of the second specific example in that the position where the eccentric signal ES generated by the eccentric signal generation unit 4 is fed forward is different.

  The tracking servo device 42 is given a target value r of the tracking error signal from the input terminal 2 in a state where the switch 10 is turned on. This target value r is supplied to the subtracter 3. The subtracter 3 is also supplied with a tracking error signal TES from the tracking actuator 12 to be controlled (P). The subtracter 3 subtracts the tracking error signal TES from the target value r of the tracking signal and supplies the difference signal to the control filter 43 as a subtraction output.

  Before the tracking servo switch 10 is turned on, the eccentric signal generation unit 4 includes an octopus signal, which is an FG signal supplied from the input terminal 5, and an eccentric servo switch supplied from a system controller (not shown) via the control terminal 6. Based on the signal, an eccentricity signal is generated from the tracking error signal. The tracking error signal before the switch 10 is turned on is a tracking error signal obtained in a state in which the tracking servo is not applied from the tracking actuator 12 that tracks the optical head unit with respect to the information track of the optical disk.

  The eccentric signal ES generated by the eccentric signal generation unit 4 is supplied to the adder 8. The eccentric servo unit 14 feeds the eccentric signal ES generated by the eccentric signal generation unit 4 forward to the tracking servo unit 15 via the adder 8.

  As described above, the tracking servo device 42 in FIG. 12 feeds the output signal from the eccentric signal generation unit 4 (the eccentric signal ES detected from the tracking error signal TES) to the tracking servo unit 15. .

  Note that when feedforward is performed, the polarities of the eccentricity signal and the drive signal are adjusted so that the tracking error signal is reduced by the eccentricity signal.

  The tracking actuator 12 supplies a tracking error signal TES to the output terminal 13 and feeds it back to the tracking servo switch 10 and the subtracter 44.

  The subtracter 44 subtracts the tracking error signal output from the tracking actuator 12 from the ideal tracking error signal and supplies the subtraction signal to the eccentricity signal generation unit 4. Thereby, the eccentric signal generation unit 4 generates the eccentric signal ES based on the tracking error signal.

  Since the eccentric servo unit 14 causes the head to substantially follow the eccentricity, the tracking servo unit 15 only has to deal with a tracking error that cannot be followed by the eccentric servo unit 14. In this case, when viewed from the tracking error loop, the tracking servo is performed with respect to a disk with very little eccentricity, so that a servo band is not required as compared with the tracking servo unit 15 alone. On the contrary, if the servo band is made the same as that of the tracking servo unit 15 alone, the tracking accuracy is improved.

  However, as an operation sequence, the eccentric servo is first, and then the tracking servo is performed. This is because if the tracking servo is turned on first, a tracking error signal cannot be obtained and an eccentricity signal cannot be generated.

  Further, by adopting a two-stage servo configuration with coarse tracking by the eccentric servo unit 14 and fine tracking by the tracking servo unit 15, the allowable eccentricity amount can be increased. That is, if the allowable eccentricity in the case of the tracking servo unit 15 alone is Δ, the allowable residual error amount in the eccentric servo loop is Δ, and the allowable eccentricity Δ ′ in the eccentric servo loop is It becomes larger than Δ by the gain of the core servo loop. That is, the allowable eccentricity can be increased as a whole.

  FIG. 13 shows a fourth specific example of the tracking servo apparatus according to the present invention. Unlike the first to third specific examples, the tracking servo device 45 operates the eccentric servo by the eccentric servo unit 14 and the tracking servo by the tracking servo unit 15 simultaneously. However, an eccentricity signal is generated before the tracking servo is operated.

  The tracking servo switch 10 is provided between the adder 8 and the tracking actuator 12. In the first specific example, it is different from that provided between the control filter 9 and the adder 8.

  Therefore, in this tracking servo device 45, when the tracking servo switch 10 is turned on, the eccentric servo by the eccentric servo unit 14 and the tracking servo by the tracking servo unit 15 operate simultaneously.

  Before the tracking servo switch 10 is turned on, the eccentric signal generation unit 4 includes an octopus signal, which is an FG signal supplied from the input terminal 5, and an eccentric servo switch supplied from a system controller (not shown) via the control terminal 6. Based on the signal, an eccentricity signal is generated from the tracking error signal. This eccentric signal is supplied to the control filter 7.

  When the switch 10 is turned on, the target value r of the tracking error signal is given from the input terminal 2. This target value r is supplied to the subtracter 3. The subtracter 3 is also supplied with a tracking error signal TES from the tracking actuator 12 to be controlled (P). The subtracter 3 subtracts the tracking error signal TES from the target value r of the tracking signal and supplies the difference signal to the control filter 9 as a subtraction output. The filter output from the control filter 7 is also supplied to the filter output of the control filter 9 by the adder 8.

  Since the optical head substantially follows the eccentricity by the eccentric servo unit 14, the tracking servo unit 15 only needs to deal with a tracking error that cannot be fully followed by the eccentric servo unit 14. In this case, when viewed from the tracking error loop, the tracking servo is performed with respect to a disk with very little eccentricity, so that a servo band is not required as compared with the tracking servo unit 15 alone. On the contrary, if the servo band is made the same as that of the tracking servo unit 15 alone, the tracking accuracy is improved.

  FIG. 14 shows a fifth specific example of the tracking servo apparatus according to the present invention. The tracking servo device 46 also simultaneously operates the eccentric servo by the eccentric servo unit 14 and the tracking servo by the tracking servo unit 15. However, an eccentricity signal is generated before the tracking servo is operated. Further, the tracking servo device 46 is different from the tracking servo device 45 of the fourth specific example in comparison with the fourth specific example having two control filters of the control filter 7 and the control filter 9. Thus, a common control filter 47 is used. That is, the eccentric signal ES of the eccentric signal generation unit 4 is fed forward to the tracking servo unit 15 and the tracking actuator 12 is driven by the common control filter 47.

  In other words, the eccentric servo unit 14 feeds forward the eccentric signal ES generated by the eccentric signal generation unit 4 to the tracking servo unit 15, and the tracking servo unit 15 uses the common control filter 47 to track the tracking actuator 12. Drive. Since other configurations and operations are the same as those of the first specific example, description thereof will be omitted.

  FIG. 15 shows a sixth specific example of the tracking servo apparatus according to the present invention. The tracking servo device 48 also simultaneously operates the eccentric servo by the eccentric servo unit 14 and the tracking servo by the tracking servo unit 15. However, an eccentricity signal is generated before the tracking servo is operated. Further, the tracking servo device 48 is different from the tracking servo device 46 of the fifth specific example in that the position where the eccentric signal ES generated by the eccentric signal generating unit 4 is fed forward is different. .

  The tracking servo device 48 is given a target value r of the tracking error signal from the input terminal 2 with the tracking servo switch 10 turned on. This target value r is supplied to the subtracter 3. The subtracter 3 is also supplied with a tracking error signal TES from the tracking actuator 12 to be controlled (P). The subtractor 3 subtracts the tracking error signal TES from the target value r of the tracking signal and supplies the difference signal to the control filter 49 as a subtraction output.

  The eccentric signal ES generated by the eccentric signal generation unit 4 is supplied to the adder 8. The adder 8 is also supplied with a tracking error signal from the tracking actuator 12. Here, the eccentric servo unit 14 feeds forward the eccentric signal ES generated by the eccentric signal generation unit 4 to the tracking servo unit 15 via the adder 8.

  As described above, the tracking servo device 48 in FIG. 15 feeds forward the output signal from the eccentric signal generation unit 4 (the eccentric signal ES detected from the tracking error signal TES) to the tracking servo unit 15. .

  FIG. 16 shows a seventh specific example of the tracking servo apparatus according to the present invention. Unlike the first to sixth specific examples, the tracking servo device 50 drives an actuator P′51 such as a thread motor in the eccentric servo by the eccentric servo unit 14, and based on that. The tracking actuator 12 is driven by the normal tracking servo unit 15. However, before the tracking servo is operated, the eccentric signal is generated by the eccentric signal generation unit 4.

It is a block diagram of the 1st specific example of a tracking servo apparatus. It is the figure which showed the tracking error signal TES in an optical disk. FIG. 3 is a diagram showing the relationship between the tracking error signal TES and the disk eccentricity shown in FIG. 2. It is the figure which expanded the tracking error of A vicinity in FIG. It is the figure which expanded the tracking error of B vicinity in FIG. It is a block diagram of an eccentric signal generation part. It is a figure which shows the signal waveform output by each part of an eccentric signal production | generation part. It is a figure explaining the principle of operation of an inversion mask generating part. It is a block diagram of the 1st specific example of an eccentric signal holding | maintenance part. It is a block diagram of the 2nd specific example of an eccentric signal holding | maintenance part. It is a block diagram of the 2nd example of a tracking servo apparatus. It is a block diagram of the 3rd example of a tracking servo apparatus. It is a block diagram of the 4th example of a tracking servo apparatus. It is a block diagram of the 5th example of a tracking servo apparatus. It is a block diagram of the 6th specific example of a tracking servo apparatus. It is a block diagram of the 7th example of a tracking servo apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tracking servo device, 4 Eccentric signal generation part, 7 Filter control part, 9 Filter control part, 10 Tracking servo switch, 12 Tracking actuator, 14 Eccentric servo part, 15 Tracking servo part

Claims (13)

Tracking error obtained when tracking servo is not applied from a tracking actuator that tracks the information track of the disk-shaped optical recording medium with optical head means for recording / reproducing information by irradiating the disk-shaped optical recording medium with a beam An eccentric signal generating means for generating an eccentric signal based on the signal;
Eccentric servo means using the eccentric signal generated by the eccentric signal generating means;
A tracking servo device comprising: tracking servo means for performing tracking servo with a remaining amount of servo by the eccentric servo means.   The eccentric signal generating means extracts a low frequency corresponding to the maximum eccentricity portion of the tracking error signal in one rotation of the disk, and a low frequency output extracted by the low frequency extracting means. 2. A tracking servo apparatus according to claim 1, wherein the peak detecting means detects the envelope after only half-waves, and the eccentricity signal is generated from the detection output detected by the peak detecting means.   The eccentric signal generation means generates an inverted mask signal from the detection output detected by the peak detection means, and inverts the detection output of the peak detection means according to the inverted mask signal to generate the eccentric signal. The tracking servo apparatus according to claim 2, wherein   2. The tracking servo apparatus according to claim 1, wherein the eccentric signal generating means further includes an eccentric signal holding means for holding the generated eccentric signal for one rotation of the disk.   2. The tracking servo apparatus according to claim 1, wherein the eccentric signal holding means holds the eccentric signal for one rotation of the disk before the tracking servo is turned on.   The eccentric servo means has a first control filter for inputting the eccentric signal, and feeds a servo remaining amount by the first control filter to the tracking servo means. The tracking servo device according to Item 1.   The tracking servo means includes a second control filter to which the tracking error signal is input, the tracking actuator to which the filter output of the second control filter is input, and the second control filter and the tracking actuator. A tracking servo device according to claim 1, further comprising a tracking servo switch for turning on or off the tracking servo.   After the tracking servo switch is turned on, the tracking servo means controls the tracking actuator while adding the servo remaining amount by the eccentric servo means to the filter output of the second control filter, and the tracking servo 8. The tracking servo device according to claim 7, wherein tracking servo is performed while feeding back a tracking error signal via the actuator.   The tracking servo according to claim 1, wherein the eccentric servo means feeds forward the eccentric signal to the tracking servo means, and the tracking servo means drives the tracking actuator by a common control filter. apparatus.   2. A tracking servo apparatus according to claim 1, wherein the eccentric servo means and the tracking servo means operate simultaneously.   The eccentric servo means includes a first control filter for inputting the eccentric signal, and feeds a servo remaining amount by the first control filter to the tracking servo means. The tracking servo apparatus according to claim 10.   The tracking servo means includes a second control filter to which the tracking error signal is input, the tracking actuator to which the filter output of the second control filter is input, and the second control filter and the tracking actuator. 12. A tracking servo device according to claim 11, further comprising a tracking servo switch for turning on or off the tracking servo between the two.   The eccentric servo means has a first control filter for inputting the eccentric signal, and controls another actuator different from the tracking actuator, and the tracking servo means receives the tracking error signal. The tracking servo apparatus according to claim 1, further comprising: a control filter for controlling the tracking actuator.

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