JP2002324372A - Disk reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a fine-speed feeding of a pickup, in which there is no hunching even when a gear ratio of a slide feed mechanism for a pickup is large. SOLUTION: The pickup 1 having a tracking actuator coil 1a, a feed motor 10 which moves the pickup 1, and a microcomputer 6 which generates a driving signal for the tracking actuator coil 1a on the basis of a read signal of a recording medium outputted from the pickup 1 are provided. On the basis of the driving signal for the tracking actuator coil 1a, a pulse voltage, as a driving signal for moving the pickup 1, whose voltage value is gradually increased, is generated by the microcomputer 6, an analog switch 7, a variable voltage power source 8, and a motor driver 9. The pickup 1 is fed at a fine speed by supplying the pulse voltage to the motor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickup driving device for moving a pickup in a radial direction of a disc when reproducing information from a disc as a recording medium, for example.

[0002]

2. Description of the Related Art For example, in a disk reproducing apparatus, when reproducing information from a disk, a pickup is moved in a radial direction of the disk by a slide feed motor. As such a slide feed motor, a linear motor is used in some intermediate and high-end machines.

However, when a linear motor is used, the circuit of the speed control system becomes complicated, and a high-precision feed mechanism is required, resulting in an increase in cost. In addition, power consumption increases when a high-speed search is attempted.

Therefore, in a conventional type of disk reproducing apparatus, a DC brush motor is used as a slide feed motor of a pickup, and a slide feed mechanism is configured by combining this motor with a rack and pinion mechanism, a ball screw, a flat gear, and the like. are doing.

As shown in FIG. 14, a conventional slide feed system using a DC brush motor includes a pickup 51 having a tracking actuator coil 51a and an objective lens 51b, an RF amplifier 52, a servo LS
I53 phase compensation amplifier 53a and BTL (Balanced
Transformer Less) The driver 54 forms a tracking servo loop T. Further, a pickup 51, an RF amplifier 52, a phase compensation amplifier 53a of a servo LSI 53, and a low-pass filter 53 of a servo LSI 53
b, a motor driver 55 and a feed motor 56 composed of a DC brush motor constitute a slide servo loop S. The servo LSI 53 is controlled by a microcomputer (hereinafter, referred to as a microcomputer) 57.

In the above-described slide feed system, at the time of slide feed during reproduction, an input signal to the BTL driver 54 for driving the tracking actuator coil 51a, that is, a TRD (tracking drive) signal is passed through a low-pass filter 53b. The low-frequency component is extracted. The feed motor 56 is driven by the motor driver 55 based on this signal, and the pickup 51 is slid in the radial direction of the disk as the recording medium.

In the above-described slide feed system, high-speed search by slide feed is performed by a track count method according to the procedure shown in FIG. 15 and the following.

[0008] 1. At the start (point a), the tracking servo is turned off.

[0009] 2. The rotation of the feed motor 56 in a predetermined direction is started (point b).

[0010] 3. A counter for measuring the track cross value based on the track cross signal is set (point c).

4. When the value measured by the counter reaches a predetermined value, the feed motor 56 is stopped (point d).

5. Back electromotive force brake of feed motor 56,
After waiting for the pickup 51 to stop due to the loss torque of the slide feed mechanism (period e), the tracking servo is turned on (point f).

As described above, in the configuration using the DC brush motor as the feed motor 56, the control is relatively easy,
High-speed search by the track count method is possible.

[0014]

However, in the above-mentioned conventional disk reproducing apparatus using a DC brush motor as the feed motor 56, it is necessary to reduce the voltage, size and power consumption of the apparatus. When a high-speed seek is attempted, the following problems are caused.

1) When a high-speed seek is to be performed in a track count search, if the power supply voltage of the feed motor 56 can be designed to be sufficiently high, as shown in FIG. In the following, the motor voltage Vm is a parameter in the N / T characteristic.
Can be used, for example, from 1 to 10 V, and the dynamic range becomes as wide as 10 times (20 dB). In this case, even if the gear ratio of the slide feed mechanism is set small enough to make the acceleration of the fine feed of the pickup 51 at the time of reproduction sufficiently small, high-speed seek can be performed.

On the other hand, in order to reduce the voltage and power consumption,
When the power supply voltage of the feed motor 56 is designed to be, for example, about 5 V, the motor voltage Vm becomes about 4 V due to a voltage drop in the motor driver 55 and the like, and the dynamic range is about four times (12 dB). Become. In this case, unless the gear ratio of the slide feed mechanism is set to be 2.5 times larger than in the above-described case, high-speed seek cannot be performed in the track count search. However, with the large gear ratio as described above, it is difficult to sufficiently reduce the acceleration at the very low speed during reproduction. As a result, it becomes impossible to perform the fine-speed feeding of the pickup 51 satisfactorily.

Incidentally, Japanese Patent Application Laid-Open Nos.
JP-A-1-206976 and JP-A-62-149077 disclose a configuration in which a pulse voltage is supplied as a drive signal for the feed motor 56, but the feed motor 56 can be satisfactorily provided only by supplying a pulse voltage. Drive,
In addition, it is difficult to sufficiently suppress the acceleration of the fine feed of the pickup 51.

2) When a high-speed seek is to be performed in the track count search, as shown by a broken line in FIG. 17, the vibration of the pickup 51 becomes more remarkable as the speed is increased. Further, the vibration of the pickup 51 is caused by the increase of the self-resonant frequency and the resonance
It becomes remarkable by the increase of.

The vibration of the pickup 51 is generated as follows. When the tracking servo is ON, the tracking actuator coil 51 of the pickup 51
“a” drives and controls the objective lens 51b in the disk radial direction. However, at the time of seeking when the tracking servo is OFF, the objective lens 51b which should be at the neutral position
Is displaced by the acceleration and the inertia of the objective lens 51b.
Therefore, the pickup 51 vibrates during the seek and after the completion of the seek.

The above-mentioned vibration of the pickup 51 causes an increase in counting errors and variations in the number of tracks in the track-counting search, and hinders a high-speed search.

3) When a high-speed seek is to be performed in the track count search, the N / N
In consideration of variations such as the T characteristic and the loss torque of the slide feed mechanism, it is necessary to perform control for correcting or learning the table of the track count set value for each disk reproducing device. However, since the landing accuracy of the search in the track count method changes every time due to the following factors, it is not easy to control the track count set value by correction or learning.

The above factors are the eccentricity of the disk and the eccentricity of the disk mounting mechanism, ie, the eccentricity of the disk with respect to its rotation center, and the sliding feed mechanism of the slide feed mechanism by the coking torque determined by the number of poles of the motor 56 and the gear ratio. This includes erroneous counting due to the resolution and the low S / N ratio of the track cross signal generated from the tracking error signal, or erroneous counting for the track cross signal due to the vibration of the pickup 51 described above.

4) When a high-speed seek operation is performed in a search method other than the track count search method, the problem caused by the vibration of the pickup as shown in FIG. 17 does not occur during the track count. However, when the track count method is not employed, for example, a sensor including a photodetector and a reflector, or a sensor including a Hall element and a magnet is required for controlling the slide feed mechanism, and a waveform shaping circuit for the sensor output is also required. Cost. In addition, the above-described variations in the N / T characteristics of the feed motor and the loss torque of the feed mechanism, the resolution of the slide feed mechanism due to the cogging torque determined by the number of poles and the gear ratio of the motor, or the eccentricity of the disk and the eccentricity of the disk mounting mechanism. Variations in landing accuracy for each search cannot be avoided. Further, it is not possible to avoid variation in landing accuracy due to vibration of the pickup remaining when the tracking servo is turned on.

[0024]

In order to solve the above-mentioned problems, a pickup driving device according to the present invention comprises a pickup having a tracking actuator and moving the pickup in a direction perpendicular to the track direction of a disk as a recording medium. A feed motor for driving, a drive signal generating means for generating a drive signal for a tracking actuator based on a read signal of a recording medium output from the pickup, and a tracking actuator for tracking based on the drive signal for the tracking actuator. Detecting means for detecting an amount of displacement from a free center position, which is a position of the driven body when a driving signal is not input to the tracking actuator, during a tracking operation of the driven body driven by the pickup; Running When performing a search for a track to be performed, so that the driven body is disposed at the free center position, after controlling the tracking actuator based on an output of the detection unit, the search is performed so that the search is performed. Control means for controlling the feed motor.

According to the structure of the present invention, the control means first searches for a track to be scanned by the pickup so that the driven body is arranged at the free center position.
The tracking actuator is controlled based on the displacement of the driven body from the free center position detected by the detection means. At this free center position, the vibration of the driven body is suppressed. Accordingly, thereafter, the control means controls the feed motor so that a search for a track to be scanned is performed.

With the above control, in the present disk reproducing apparatus, it is possible to suppress a decrease in search accuracy due to the vibration of the driven body of the pickup, and to perform a highly accurate search.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment of the Invention] One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, in the present disk reproducing device constituting a pickup driving device, a pickup 1, R having a tracking actuator coil (tracking actuator) 1a and an objective lens (driven body) 1b is provided.
A tracking servo loop T is configured by the F amplifier 2, the tracking equalizer amplifier (drive signal generating means) 3a, and the actuator driver 4. Also,
Pickup 1, RF amplifier 2, tracking error waveform shaping amplifier 3b, tracking equalizer amplifier 3
a, low-pass filter (motor drive signal supply means) 3
A slide servo loop S is constituted by c, the low-pass filter 5, the microcomputer 6, the analog switch 7, the variable voltage power supply 8, the motor driver 9, and the feed motor 10. The tracking equalizer amplifier 3a, the waveform shaping amplifier 3b, and the low-pass filter 3c include a servo LS
Included in I3.

The pickup 1 reads a signal recorded on a disk (not shown) as a recording medium and takes out the signal as an electric signal. The RF amplifier 2 amplifies an output signal from the pickup 1.

The tracking equalizer amplifier 3a has an R
TR for performing tracking from a tracking error signal obtained from the pickup 1 via the F amplifier 2
A D (tracking drive) signal is generated and supplied to the actuator driver 4. The waveform shaping amplifier 3b shapes the waveform of a tracking error signal obtained from the pickup 1 via the RF amplifier 2, and performs TC shaping.
An RS (track cross) signal is generated, and this signal is supplied to the microcomputer 6. Low-pass filter 3c
Is the output of the tracking equalizer amplifier 3a, that is, T
A signal having a frequency component of about 0.5 to 5 Hz is extracted from the RD signal. The output signal of the low-pass filter 3c is input to the A / D input terminal 6c of the microcomputer 6 as a TVD (traverse drive) signal.

The actuator driver 4 drives the tracking actuator coil 1a of the pickup 1 based on the output from the tracking equalizer amplifier 3a. Driven by the tracking actuator coil 1a, the objective lens 1b performs tracking.

The low-pass filter 5 extracts a TRP (tracking position) signal having a frequency of about 300 to 1000 Hz from the output of the tracking equalizer amplifier 3a. This TRP signal is a signal close to the tracking drive signal itself of the tracking servo loop T, and is a signal indicating the position of the pickup 1 in the disk radial direction, that is, the tracking position.

The microcomputer 6 controls the operation of the disk reproducing apparatus, and includes a counter input terminal 6a, an A / D
(Analog / digital conversion) Input terminals 6b and 6c as input ports, output terminals 6d, 6e and 6f as D / A (digital / analog conversion) ports, and rewritable memory (storage means) 6g I have.

The TCRS signal is input to the counter input terminal 6a from the waveform shaping amplifier 3b. This TCRS signal is used at the time of high-speed search. Input terminal 6b
Receives the TVD signal, and the input terminal 6c receives the TRP signal. The microcomputer 6 selects the two input terminals 6b and 6c or one of these input terminals, and takes in the TVD signal and the TRP signal as appropriate.

An output terminal 6d outputs a TVDO (traverse drive output) signal. This TVDO signal is a signal for controlling the rotation of the motor driver 9, that is, the feed motor 10, and is input to the motor driver 9 via the analog switch 7. The microcomputer 6 generates the TVDO signal based on the TVD signal. In this case, the microcomputer 6 performs the TV calculation based on a proportional operation from the TVD signal or a table preset in a storage circuit (PROM: program read only memory) provided in the microcomputer 6.
Generate a DO signal.

From the output terminal 6e, a PLM (play window)
A signal is output. The PLM signal is an output of the motor driver 9, that is, a signal for turning on / off the feed motor 10. Here, by the H / L of the PLM signal,
The analog switch 7 is turned on / off, and the supply of the TVDO signal to the motor driver 9 is turned on / off. SLDV (slide motor voltage control) from output terminal 6f
A signal is output. This SLDV signal controls the output voltage of the variable voltage power supply 8.

The analog switch 7 turns on / off the supply of the TVDO signal from the microcomputer 6 to the motor driver 9.
It is for doing. The variable voltage power supply 8 has a variable output voltage and supplies a voltage for generating the motor voltage Vm to the motor driver 9. The motor driver 9 receives the voltage supplied from the variable voltage power supply 8 and the TVD input from the microcomputer 6 via the analog switch 7.
A motor voltage Vm for driving the feed motor 10 is generated based on the O signal, and supplied to the feed motor 10. Therefore, the above low-pass filter 3c,
The microcomputer 6, the analog switch 7, the variable voltage power supply 8 and the motor driver 9 constitute a motor drive signal supply unit.

The feed motor 10 is, for example, a DC brush motor, and receives the motor voltage Vm to slide the pickup 1 in the radial direction of the disk.

The operation of the disk reproducing apparatus having the above configuration will be described below. During playback, the microcomputer 6
Performs control for sliding the pickup 1 at a very low speed. At this time, the relationship between the TVD signal, the TVDO signal, the PLM signal, and the voltage Vm of the feed motor 10 and the time is as shown in FIG. Here, for convenience of explanation, each state when the slide feed mechanism and the feed motor 10 are not connected is shown. When both are connected, the feed motor 10 starts to move by the pulse voltage Vm corresponding to the TVDO signal at the feed start point a, so that the TVDO signal changes in the direction of the reference point o.

The TVD signal is obtained by passing the TRD signal for driving the tracking actuator coil 1a of the pickup 1 through the low-pass filter 3c. In addition, the pickup 1 moves outward from the reference point in the radial direction of the disc with the elapse of time at the time of sliding at a low speed during reproduction. Therefore, the TRD signal changes from the reference point in a direction set as the outside of the radial direction of the disk as shown in FIG.

The TVDO signal is, as shown in FIG.
The transition is almost the same as the D signal. However, in order to prevent the motor driver 9 from applying the motor voltage Vm more than necessary to the feed motor 10, the TVDO signal has an upper limit point b.

When the TVD signal reaches the sending start point, and similarly when the TVDO signal reaches the sending starting point a, the PLM signal opens a window t of a fixed time width, that is, the analog switch 7 is turned on for a fixed time t. Turn ON, and T
A VDO signal is applied. Also, the PLM signal is
A window t of a fixed time width at a fixed interval T after the above-mentioned feeding start point.
Keep open. On the other hand, when the pickup 1 approaches the reference point after passing the feed start point, that is, when the pickup 1
If the signal moves to the reference point after the feed start point,
Stop opening windows for a certain period of time.

The motor driver 9 generates a pulsed motor voltage Vm based on the voltage supplied from the variable voltage power supply 8 and the TVDO signal input via the analog switch 7. The width and timing of the pulse signal are set by the window t of the constant time width of the PLM signal, and the magnitude at that time is set by the magnitude of the TVDO signal. Therefore, the motor voltage Vm is
It does not exceed the upper limit b of the DO signal, that is, the value corresponding to the upper limit. At the feed start point a, the minimum starting voltage of the feed motor 10 is given to the feed motor 10 as the motor voltage Vm.

As described above, in the present disk reproducing apparatus,
The feed motor 10 is driven by a motor voltage Vm consisting of a pulse signal at the time of fine speed feed during reproduction. Therefore, even when the power supply voltage is set low in order to reduce the voltage or power consumption of the apparatus and the gear ratio of the slide feed mechanism is set large in order to perform a high-speed search, a very low speed during reproduction is required. The acceleration at the time of feeding can be suppressed to a sufficiently small value.

Further, the motor voltage V at the feed start point
m is set to the minimum starting voltage of the feed motor to be used,
The motor voltage Vm is set to the upper limit motor voltage Vm given at the upper limit point b of the TVDO signal. Therefore, the amount of movement of the pickup 1 in one slide feed is limited, and the phenomenon that the pickup 1 moves back and forth in the radial direction of the disk due to too much feed per time, that is, hunting occurs. It is unlikely to occur. As a result, the present disk reproducing apparatus has a stable feed servo system in which the acceleration at the time of fine-speed feeding during reproduction is minimized and hunting is suppressed.

In the configuration shown in FIG. 1, a BTL (Balanced Transformer Less) driver I
When C is used, since an output proportional to the TVDO signal is obtained from the BTL driver IC, the variable voltage power supply 8
Need not be provided as a separate circuit, and the SLDV signal which is a voltage control signal thereof is not required.

As shown in FIG. 3, the present disk reproducing apparatus includes a motor driver 21 in place of the motor driver 9 shown in FIG. May be provided. The motor driver 21 is a PWM (Puls Wids Mo)
duration: pulse width modulation). LC
The filter 22 is provided to remove interference noise and unnecessary radiation from peripheral components due to the PWM component.

The motor driver 21 has an ST / SP terminal 21a for inputting start / stop of the operation.
This ST / SP terminal 21a is connected to a general PWM driver I.
C is provided. ST / SP terminal 21a
Is supplied with a PLM signal. Therefore, in the present disk reproducing apparatus, the analog switch 7 is not required, and the TVDO signal is also directly input to the motor driver 21. The other configuration is the same as the configuration shown in FIG.

The motor driver 21 changes the duty ratio of the output pulse signal in accordance with the TVDO signal. That is, the duty ratio increases when the TVDO signal has a large value, and decreases when the TVDO signal has a small value. For example, the duty ratio is 66% shown in FIG. 4A and 33% shown in FIG. To change. When the PWM signal is processed by the LC filter 22, the signal shown in FIG. 4A becomes the DC voltage shown in FIG. 4B, and the signal shown in FIG.
The DC voltage shown in FIG.

As described above, in the present disk reproducing apparatus,
The pulse voltage as the motor voltage Vm output from the motor driver 21 has a duty ratio changed according to the magnitude of the TVDO signal.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. 1, 2, 6 and 7. In the disc reproducing apparatus shown in FIG. 1, in the fine-speed slide feed at the time of reproduction, by driving the feed motor 10 with the pulse voltage as described above, hunting hardly occurs and stable feed servo is realized. . In the disc reproducing apparatus according to the present embodiment, in order to realize more accurate fine-speed slide feed, attention is paid to the characteristics of the feed motor 10 so that adverse effects due to these characteristics can be avoided.

Feed motor 10 composed of a DC brush motor
As described above, there are three characteristics of N / T characteristics (rotational speed / torque characteristics), coking torque and loss torque as described below.

N / T Characteristics (Rotation Speed / Torque Characteristics) An example of the N / T characteristics is as shown in FIG.
The N / T characteristic of the DC brush motor is determined by the magnetic circuit of the motor and the moment of inertia of the rotor. The higher the magnetic flux density of the magnetic circuit and the smaller the moment of inertia of the rotor, the slope of the graph shown in FIG. Becomes steep. Further, the N / T characteristic is affected by the variation of the magnet in the magnetic circuit.

Coking torque Coking torque is generated by the magnetic circuit of the motor. The coking torque will be described with reference to a DC brush motor having a three-pole / two-magnet structure generally used for a feed motor.

In the three-pole / two-magnet structure of the DC brush motor, the positional relationship between the rotor coil and the magnet is as shown in FIGS. In the figure, the rotor 31 has three-pole rotor coils 31a to 31c. 32a and 32b are fixed magnets. Rotor 3
1 (a) or (b) in FIG.
Try to stop at the position.

FIG. 6A shows a state in which the rotor coil 31a is most attracted to the magnet 32b by the magnetic force. In this state, the magnet 32b is attached to the rotor coil 31.
b or when the rotor coil 31c is pulled most, or when the rotor coil 31a-
The same applies to the case where any one of the lines 31c is drawn most. Accordingly, in the three-pole / two-magnet structure, there are six positions where the resistance is large due to the magnetic force when the rotor 31 starts to rotate, that is, the positions where the torque is high, for the position where the state of FIG. .

FIG. 6B shows the rotor coil 31a.
31c is attracted to the magnet 32a, and the other one is attracted to the magnet 32b in the same positional relationship. There are six positions where the torque is high, even if the position shown in FIG. Therefore, in the three-pole / two-magnet structure of the DC brush motor, there are a total of 12 positions where the torque is high, which is a characteristic called coking torque.

This coking torque is obtained by
Significant variations occur due to the assembling accuracy of the rotor and the magnet, the management of the magnetization of the magnet, and the like.

Loss Torque Loss torque is a torque generated by frictional resistance at a bearing of a motor. The magnitude of the loss torque varies among individual motors depending on the dimensional accuracy and finishing accuracy of the bearing portion. In a DC brush motor, the frictional resistance between the electrode of the rotor coil and the brush also adds to the loss torque.
Accordingly, the loss torque in this case varies depending on the spring pressure of the brush, the dimensional accuracy and the finishing accuracy of the electrode and the brush, and the like.

As described above, the individual feed motors 10 have various variations in each characteristic. Therefore, in the present disk reproducing apparatus, the following control is performed in the control shown in FIG. 2 in order to realize uniform and high-precision fine-speed feeding without being affected by variations in the characteristics of the individual feed motors 10. Is going.

That is, in the control of FIG. 2, the PLM signal is a pulse signal of a window t having a fixed time width, and a signal inversely proportional to the TVD signal whose pulse width is limited by the PLM signal is a motor shown in FIG. The signal is supplied to the feed motor 10 via the driver 9 as the motor voltage Vm. In this example, it is assumed that the motor driver 9 is of the inverting input AMP type.

In this embodiment, the following control is performed to supply the motor voltage Vm having the waveform shown in FIG.

1. The microcomputer 6 calculates the average shift amount of the pickup 1 (the solid line portion of the TVD signal shown in FIG. 2).
An input terminal 6b which is an A / D port shown in FIG.
Take in. Next, the microcomputer 6 performs an operation based on the captured value or a software table,
A TVDO signal is obtained as shown in FIG.
Output from the output terminal 6d which is the A port.

2. When the microcomputer 6 determines that the TVD signal that has reached the feed start point shown in FIG. 2 has been input to the input terminal 6b, the signal of the pulse width T1 to Tn is inversely proportional to the input value (variation is corrected based on an experiment). From the output terminal 6e as a PLM signal.

3. The TVDO signal is input to the analog switch 7, and the analog switch 7 is turned ON / OFF by the PLM signal, thereby generating a pulse width t1.
Ｔtn to a pulse height TVDO signal. This T
When the VDO signal is input to the motor driver 9, the motor voltage Vm shown in FIG.

As described above, the pulse width of the motor voltage Vm is wide when the voltage value, that is, the peak value is low, and the pulse width is narrow when the peak value is low. This allows
The pickup motor 1 can be accurately moved by the feed motor 10 and the minimum starting voltage at that time can be reduced by reducing the influence of the difference and variation of the coking torque due to the rotation start position of the feed motor 10 and the variation of the slide feed mechanism. (The minimum starting voltage of the motor is almost proportional to the load at that time). Accordingly, the acceleration of the pickup 1 is minimized, and the pickup 1 can be sent with a minimum moving amount determined by the gear ratio of the mechanical system.

[Third Embodiment of the Invention] Still another embodiment of the present invention will be described below with reference to FIGS. 1, 8 to 11. In the disk reproducing apparatus, in a high-speed search by a track count method, a learning function is used to avoid a decrease in search accuracy due to a search error, thereby enabling a high-speed search.

In the high-speed search by the slide feed, the pickup 1 reaches the target track by accurately crossing the track up to the target track, and thereafter, the tracking servo is turned on, and the pickup 1 reproduces information of the target track. The following three main factors can reduce the accuracy of this search.

The eccentricity of the disk with respect to its center of rotation caused by the eccentricity of the disk and the eccentricity in the chucking state due to the low chucking accuracy of the disk chucking mechanism.

The resolution of the slide feed by the feed motor and the gear ratio of the slide feed mechanism.

Backlash of slide feed mechanism.

First, the effect of the eccentricity on the search accuracy will be described. For example, in a compact disk (hereinafter referred to as a CD) 41 shown in FIG. 8, the eccentricity H of the CD 41 itself with respect to a perfect circle 42 is regulated to 70 μm or less in the standard. Here, it is assumed that the eccentric amount H of the CD 41 is 70 μm and the eccentric amount due to the chucking of the disk chucking mechanism is 58 μm. In this case, the maximum eccentricity due to both eccentricities is 128 μm. Meanwhile, CD41
Has a track pitch of 1.6 μm. Therefore, the search accuracy in this case is 80 by the calculation of 128 ÷ 1.6.
Become a truck. That is, the search accuracy at an eccentric amount of 128 μm is ± 80 tracks (books).

Next, the effect of the slide feed resolution on search accuracy will be described. As described above, the feed motor 10 has the coking torque, and the resolution of the slide feed is determined from the relationship between the coking torque and the gear ratio of the feed mechanism, and this resolution affects the search accuracy. For example, the gear ratio of the slide feed mechanism is set to 0.6 mm / rotation, and the polarization point where the coking torque acts, that is, the rotor 31 is rotated.
Assuming that there are twelve stopping points as described above, the above resolution is 50 μm by the calculation of 0.6 mm ÷ 12. At this resolution, the track pitch of the CD is 1.6 μm.
In the case of m, a search error of ± 50 μm, that is, ± 31 search errors in a track occurs.

Next, the effect of the backlash on the search accuracy will be described. Generally, if the clearance is designed to be 0 (zero) in meshing the gears,
The friction increases and the gear cannot rotate. For this reason, a minimum clearance is provided between the meshing teeth. In addition, the shaft of the spur gear also needs clearance,
These clearances are the backlash. Therefore,
For example, a backlash of 50 μm results in a maximum of 31 search errors in the number of CD tracks.

In the present disk reproducing apparatus, in a high-speed search by the track count method, a standard table for search is corrected by learning in order to suppress a decrease in search accuracy due to the search error. Hereinafter, this function will be described using a CD as an example.

The microcomputer (control means) 6 has a standard table as control information for controlling the search by the track count method in the memory 6g. This standard table is set by an experiment with a disk reproducing apparatus using a motor which is a design center of the specifications of the feed motor 10. In the standard table, the track count number in the track number measurement area shown in FIG. 15 is set as the set track count number. The set track count is the number of tracks measured by the slide feed of the pickup 1 in a state where the tracking servo is off when an arbitrary target track is searched, and is set according to the target track. It is.
Note that the standard table may have the number of tracks in the non-measurement area shown in the figure as a table, and the number of tracks in the standard table may be subtracted from the target track count to determine the set track count. The number of tracks is counted by the microcomputer 6 as counting means based on the TCRS signal.

The feed motor 10 used in the disk reproducing apparatus has variations, and as shown in the graph of FIG. 9 showing the number of rotations and the track count frequency,
In addition to the standard motor h, there are a motor i having a high rotation speed and a motor j having a low rotation speed. Then, the number of tracks in the non-measurement area in the search by the track count method greatly changes among the motors h to j. Therefore, in order to realize a high-speed search, each of the motors h to j
It is necessary to perform search learning according to each characteristic and correct the standard table based on the learning.

In this case, it is possible to simply learn and correct the standard table based only on the difference between the standard table and the track jump number for each search, that is, the track count number. However, in such learning / correction, it is not possible to learn a table sufficiently adapted to the characteristics of the feed motor 10 due to the search error due to the eccentricity, the coking torque of the motor, or the backlash of the slide feed mechanism. That is, the table cannot be accurately matched with the center of the landing error for each search, and the search is delayed by the amount of the deviation.

In order to avoid the influence of the search error due to the eccentricity, the cogging torque of the motor or the backlash of the slide feed mechanism, the disc reproducing apparatus learns and corrects the standard table as follows. This correction is performed by the microcomputer 6 as correction means.

FIG. 10 shows the relationship between the standard table A and the distribution of landing errors for each search by slide feed. The standard table A has a design-centered feed motor 10
Is a standard table included in a disk reproducing apparatus (hereinafter, referred to as a design-centered apparatus) provided with. Although the distribution of the landing error for each search is different from the normal distribution, the landing error factor for each search due to eccentricity is about ± 100, and the landing error factor due to other coking torque and backlash is ±.
When there are about 50 lines and there is a landing error of ± 150 lines for each search, the distribution is slightly similar to the normal distribution as shown in FIG.

First, learning and correction of the standard table in the design-centered apparatus will be described. The standard table A here is not corrected and the range of the search error is ± 150 lines as it is, and the probability that the search by the track count can be performed with a search error within ± 50 lines increases. Therefore, the number of accurate searches and the number of track jumps due to the next lens kick and the like are reduced, and the fastest search is possible on average.

However, actually, the characteristics of the feed motor 10 of any disc reproducing apparatus other than the disc reproducing apparatus having the design-centered feed motor 10 and the rotation center when the disc is mounted on the disc reproducing apparatus are described. The amount of eccentricity of the disk with respect to is not known.

Therefore, in the learning / correction in the disc reproducing apparatus, among the elements which cause a search error in the track count method, attention is paid to an element having a large ratio of causing the search error. For example, in the above-mentioned example, eccentricity is noticed. The range in which a search error is likely to occur due to the element is defined as a non-learning area EA1. As a result, it is possible to narrow the range in which the table is moved by learning and suppress a decrease in search performance. Also, with a relatively high probability, the standard table of any disc reproducing apparatus can be quickly converged to within ± 50 of the target center table by correction. The target center table is assumed to be originally most suitable for the disc reproducing apparatus.

Next, the operation for this will be described with reference to FIG. Here, the standard table A is set in advance in the disc reproducing apparatus.
The operation of learning and correcting the target center table B will be described. If a landing error in the range of positions 1 and 2 shown in FIG. 11 first occurs when a search is performed by the track count method, the landing error is determined by the non-learning area (± 100 lines) in the distribution DA of the landing error. , The standard table is not learned or corrected.

On the other hand, in the above search, it is assumed that, for example, a landing error at the position B first occurs. In this disk reproducing apparatus, since the position of the target center table is position B, the landing error in the range EB2 between positions 2 and 3, ie, the position B
Is more likely to cause a landing error. Position B above
Is a position other than the non-learning area in the landing error distribution DA, that is, the position of the learning area, and therefore, the standard table first has one position B higher than the position A (landing error distribution DA) at that time.
Is moved to the position 1 (distribution D1 of landing error).

If the search is performed several times thereafter, a landing error at the position 3 occurs with a relatively high probability, and this position is a learning area of the distribution D1 of the landing error. Therefore, the table is learned and corrected to the position 2 (landing error distribution D2) which has moved from the position 1 to the position 3 side.

Then, although the probability is relatively low,
When the landing error at position 4 occurs, this table is a learning area of the landing error distribution D2, and the table is learned and corrected from position 2 to position B (landing error distribution B), that is, the target center table B. You.

As described above, in the present disk reproducing apparatus,
After performing a factor analysis of the landing error in the search by the track count method, the distribution of the landing error is assumed, an appropriate non-learning area is set, and the learning and correction of the table are performed based on these. As a result, in the present disk reproducing apparatus, variations in individual characteristics such as motor characteristics and backlash in the slide feed mechanism, eccentricity of the disk itself and eccentricity due to eccentricity in every disk chucking in the disk reproducing apparatus are reduced. The effect is suppressed. Therefore, a stable high-speed search can be realized.

[Fourth Embodiment of the Invention] Still another embodiment of the present invention will be described below with reference to FIGS. In the present disk reproducing apparatus, the total eccentricity that causes the landing error, that is, the eccentricity of the disk with respect to the rotation center due to the eccentricity of each disk or eccentricity due to disk chucking is accurately detected as follows. The non-learning region is accurately set based on the accurate total eccentricity.

In the specifications of the pickup 1 of the disk reproducing apparatus, there is an item called drive sensitivity of the tracking actuator, and this item further includes an item defined as a low-frequency sensitivity (1 Hz sensitivity). The unit of the low-frequency sensitivity is V / μm, and is usually about 10 mV / μm. If the low-frequency sensitivity of the tracking actuator can be detected, the amount of displacement of the tracking actuator from a free center, which will be described later, that is, the moving distance is determined by detecting the drive voltage of the tracking actuator, as can be seen from the unit. be able to. The moving distance corresponds to the amount of eccentricity of the disk with respect to the rotation center.

FIG. 12 illustrates a method of detecting the low-frequency sensitivity of the tracking actuator. The vertical axis direction in the figure is a TRP (tracking position) signal. This TRP signal, as described in FIG.
(Tracking drive) This is a signal obtained by passing the signal through the low-pass filter 5. The TRP signal is input to the input terminal 6c of the microcomputer 6, and is detected by the microcomputer 6 as a signal proportional to the drive voltage of the tracking actuator of the pickup 1.

The 0 (zero) point on the vertical axis shown in FIG. 12 is a position where the current for driving the pickup 1 does not flow through the tracking actuator coil 1a in any of the radially inward and outward directions of the disk (hereinafter referred to as “zero”). , The free center of the pickup 1). Note that the horizontal axis in FIG.

When the low-frequency sensitivity is obtained, first, when the disk reproducing apparatus is in the reproducing state of tracking servo ON, and when the pickup 1 is near the free center, the pickup 1 by the feed motor 10 is used. Stops the slide feed for one rotation of the disk (one cycle)
Is taken into the memory 6g of the microcomputer 6. This operation corresponds to the region A in FIG.

Next, the microcomputer 6 calculates the TRP of the average center position of the pickup 1 in the area A from the TRP signal.
Find the value. This TRP value is an average value of the captured TRP signals or an intermediate value between the maximum value and the minimum value.

Next, an accurate search is performed using a predetermined number of track lens kicks. In this case, for example, in the case of a CD, the track pitch is 1.6 μm.
When a book track jump is performed, a displacement of about 100 μm is given to the pickup 1. After the end of the lens kick, the TRP signal for one rotation of the disk is taken into the memory 6g of the microcomputer 6. This operation corresponds to the region B in FIG.

Next, the microcomputer 6 obtains the TRP value of the average center position of the pickup 1 in the area B from the TRP signal in the same manner as described above. Thereafter, the microcomputer 6 calculates a difference between the TRP value of the area A and the TRP value of the area B. This difference in TRP value corresponds to the amount of track jump (about 100 μm) due to the lens kick.

On the other hand, the standard value of the difference between the TRP values of the standard pickup 1 is stored in the memory 6g of the microcomputer 6 in advance. This standard value corresponds to the track jump amount. The memory 6g stores the T
The low-frequency sensitivity obtained from the difference standard value of the RP value is stored. The low-frequency sensitivity is obtained by calculating (difference in TRP value) / (amount of track jump). Accordingly, the microcomputer 6 detects the low-frequency sensitivity of the tracking actuator of the disc reproducing apparatus by comparing the difference between the TRP values obtained as described above and the standard value of the difference between the TRP signals. Note that the low-frequency sensitivity can also be obtained by (difference in TRP value obtained by measurement) / (amount of track jump).

Next, the microcomputer 6 calculates the eccentricity from the low-frequency sensitivity obtained as described above as follows. The TRP signal has a sine waveform due to the eccentricity, as shown in FIG. The maximum value and the minimum value of this waveform are stored in the memory 6g of the microcomputer 6. The microcomputer 6 calculates the total eccentricity from the low-frequency sensitivity and the maximum value and the minimum value. This calculation is: total eccentricity = (maximum value−minimum value) / (low-band sensitivity).

In the present disk reproducing apparatus, based on the above eccentricity, the number of search errors in the track counting method and other methods assumed from this eccentricity is calculated, and the number of tracks is calculated in combination with other search error factors. The number of tracks in the non-learning area in the search is determined. The determination of the number of tracks is performed by calculation or based on a dedicated table stored in the memory 6g of the microcomputer 6 in advance.

As described above, in the present disk reproducing apparatus,
The eccentricity, which is particularly uncertain as a search error factor and accounts for a relatively large proportion, can be accurately obtained,
Based on this eccentric amount, learning and correction of the standard table can be performed satisfactorily. As a result, a good search for the disk can be performed.

[Fifth Embodiment] Still another embodiment of the present invention will be described below with reference to FIGS. In this disk reproducing apparatus, when the tracking servo is turned on, the TRP signal and the low-frequency sensitivity of the tracking actuator are detected.
The displacement amount of the pickup 1 from the free center position can be known almost in real time. The reason why the real time is set substantially is that a delay of 2 to 3 mSec occurs due to the time constant of the low-pass filter 5 in FIG. 1. It doesn't matter. Therefore, in the present disk reproducing apparatus, the remaining amount of the movable amount of the pickup 1 in the disk radial direction at that time is predicted at the time of the search by the lens kick based on the displacement amount and the total eccentric amount obtained as described above. Thus, the movable amount in the radial direction of the disk can be maximized. This function will be described in detail below.

For example, in the present disk reproducing apparatus, as shown in FIG. 13, the permissible movable amount in the disk radial direction due to the lens kick of the pickup 1 is set to ± 400 μm, and the total eccentric amount due to the eccentricity of the disk and the eccentricity due to the mounting of the disk. Is ± 100 μm. Here, the permissible movable amount in the disk radial direction is a limit displacement amount at which the readout signal from the pickup 1 deteriorates when the displacement amount of the pickup 1 in the disk radial direction is further increased.

The TRP signal is a signal proportional to the low-frequency sensitivity of the pickup 1, as described above. Therefore,
The relationship between the amount of displacement of the pickup 1 in the disk radial direction and the TRP signal is, for example, 100 μm / 250 mV (TRP). This means that the pickup 1 is displaced by 100 μm with a 250 mV TRP signal. Therefore, in FIG. 13, the vertical axis can be the radial displacement of the pickup 1 and the TRP signal. In this case, the relationship between the two is 400 μm = 1V.

Here, for example, in a CD apparatus, a search, that is, a high-speed search by a track count method or a high-precision search by a lens kick is performed with the tracking servo turned off, and immediately after that, the tracking servo is turned on. Will be When such a search operation is performed, it is not easy to predict at which position of the total eccentricity of the disk the tracking servo will be turned on. Further, when the pickup 1 is vibrated in the search operation, it is completely unknown at which position in the range of the allowable movable amount of the pickup 1 in the radial direction of the disk the tracking servo is turned on.

Further, in the conventional CD device, immediately after the search, the pickup displaced in the disk radial direction is quickly returned to the vicinity of the free center position.
The pickup servo is performed based on the TVD signal. However, the TVD signal is set to 1 Hz so as to indicate the average center position of the pickup.
This is a signal that has passed through a low-pass filter that cuts off the vicinity, and has a delay of about 250 mSec. Therefore,
When high-speed servo is performed based on the TVD signal, the feed servo cannot follow.

On the other hand, in this disk reproducing apparatus, T
Since the RP signal is also used as the second signal of the feed servo, in FIG. 13, when the average center of the pickup 1 is located near the free center position, the microcomputer 6 subtracts the total eccentricity of 100 μm from 400 μm to obtain the remaining 300 μm. Can be detected as the allowable movable amount due to the lens kick.
When the TRP signal immediately after the search indicates the point K, the eccentricity of the disk from this point may be 200 μm at 100 μm × 2, so that the tolerance due to the lens kick outward in the radial direction of the disk can be reduced. The movable amount is 100 remaining
It is immediately apparent that μm is On the other hand, the allowable movable amount by the lens kick inward in the radial direction of the disc is 300 μm.
It is immediately apparent that m is In addition, the microcomputer 6
If necessary, the average center position of the pickup 1 can be known by observing one cycle of the TRP signal. Further, at the double speed or higher, the average center position can be apparent earlier than in the case of the TVD signal.

When a search by a lens kick is required at a position radially outward of the disk from the point M apparently further than the point M, TR TR
If the lens kick is performed within the range of the slide amount after performing the slide feed by the P signal, the lens kick can be safely performed.

As described above, in the present disk reproducing apparatus,
When performing a search by a lens kick, the allowable movement amount of the pickup 1 in the disk radial direction can be used to the maximum, and a high-speed search can be performed safely without deterioration of a reproduction signal.

Further, in the present disk reproducing apparatus, it is possible to suppress a decrease in search accuracy due to the vibration of the pickup 1. Hereinafter, this function will be described. The slide feed of the pickup 1 is performed with the tracking servo turned off as described above. In this case, the pickup 1 vibrates in the radial direction of the disk due to the acceleration of the slide feed. This vibration is relatively unlikely to occur in the case of a radially balanced pickup, but even with such a pickup, it becomes remarkable in a slide feed from a position largely displaced from the free center position. When the vibration becomes remarkable, the above vibration is also added to the above-mentioned eccentricity, the resolution of the slide feed and the backlash of the slide feed mechanism, which are the main factors that reduce the search accuracy.

For example, the vibration of the pickup 1 of ± 50 μm turns on the tracking servo after the slide feed is completed.
In the case of the CD device, a search error of ± 31 tracks occurs in the CD device.

Here, in the present disk reproducing apparatus, the T
The amount of displacement from the free center position of the pickup 1 can be known by the configuration for detecting the RP signal and the low-frequency sensitivity of the tracking actuator, that is, the microcomputer 6.
Also, it has been found that when the pickup 1 is at the free center position, vibration hardly occurs. Therefore, in the present disk reproducing apparatus, a search is performed according to the following procedure. First, the microcomputer 6 determines whether or not the pickup 1 is near the free center position at the end of the slide feed of the pickup 1 during the search. As a result of this determination, when the pickup 1 is at the free center position, the microcomputer 6 starts the search operation as it is. On the other hand, when the pickup 1 is not at the free center position, the microcomputer 6 sets the PL shown in FIG.
After the pickup 1 is slid toward the free center position based on the M signal and the SLDV signal, when the pickup 1 approaches the free center position, the search is started immediately.

[0111]

As described above, the pickup driving apparatus according to the present invention comprises a pickup having a tracking actuator, a feed motor for moving the pickup in a direction perpendicular to the track direction of a disk as a recording medium, and a pickup motor. Drive signal generating means for generating a drive signal for a tracking actuator based on a read signal of a recording medium to be output; and a driven body driven for tracking by the tracking actuator based on the drive signal for the tracking actuator. Detecting means for detecting a displacement amount from a free center position which is a position of the driven body when a drive signal is not input to the tracking actuator during a tracking operation; and searching for a track to be scanned by the pickup. Control means for controlling the feed motor so that the search is performed after controlling the tracking actuator based on the output of the detection means so that the driven body is disposed at the free center position. This is a configuration including:

As a result, it is possible to suppress a decrease in search accuracy due to the vibration of the driven body of the pickup.
This has the effect that a highly accurate search is possible.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of a disk reproducing device that is a pickup driving device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a TVD in the disc reproducing apparatus shown in FIG.
FIG. 4 is an explanatory diagram showing a relationship among a signal, a TVDO signal, a PLM signal, and a motor voltage Vm.

FIG. 3 is a schematic circuit diagram showing a main part of the disk reproducing device when the motor driver shown in FIG. 1 outputs a PWM signal;

4A is a waveform diagram of a PWM signal output from the motor driver shown in FIG. 3, and FIG. 4B is a diagram showing the PWM signal from the above-mentioned PWM signal via the LC filter shown in FIG. 3; It is a waveform diagram of the obtained motor voltage Vm.

5A shows another example of the PWM signal shown in FIG. 4A, and shows a waveform diagram of a signal having a smaller duty ratio than the PWM signal; FIG. ) Is FIG.
FIG. 4 is a waveform diagram of a motor voltage Vm obtained from the PWM signal shown in FIG. 3A through the LC filter shown in FIG.

6A is an explanatory diagram of a positional relationship between a rotor and a magnet when a coking torque is generated in the feed motor shown in FIG. 1, and FIG. 6B is a diagram when a coking torque is generated. It is explanatory drawing of the other said two positional relationship.

FIG. 7 is a waveform chart showing another example of the motor voltage Vm output from the motor driver shown in FIG.

FIG. 8 is an explanatory diagram showing a state in which a disk is eccentric with respect to the rotation center in a pickup driving device according to another embodiment of the present invention.

FIG. 9 is an explanatory diagram of a count region and a non-count region of the number of tracks in three feed motors whose rotation speeds are different from each other.

FIG. 10 is an explanatory diagram showing a relationship between a standard table for controlling a feed motor used in a pickup driving device according to another embodiment of the present invention and a distribution of landing errors in a search.

FIG. 11 is an explanatory diagram of an operation of learning and correcting the standard table shown in FIG. 10 in a pickup driving device according to another embodiment of the present invention.

FIG. 12 is an explanatory diagram of an operation of detecting an eccentric amount of a disk with respect to its rotation center in a pickup driving device according to still another embodiment of the present invention.

FIG. 13 is an explanatory diagram of an operation of obtaining an allowable movable amount by a lens kick in a pickup in a pickup driving device according to still another embodiment of the present invention.

FIG. 14 is a schematic circuit diagram of a disk reproducing device as a conventional pickup driving device.

FIG. 15 is a diagram showing a relationship between a track cross signal used for a search by a conventional track count method, a drive signal of a pickup feed motor, and a count area and a non-count area of the number of tracks in the slide feed of the pickup. FIG.

FIG. 16 is a graph showing a relationship between a rotation speed, a torque, and a motor voltage Vm in the feed motor shown in FIG.

17 is a graph showing a slide feed speed by a feed motor shown in FIG. 14 and a track cross frequency of a pickup.

[Explanation of symbols]

Reference Signs List 1 pickup 1a tracking actuator coil (tracking actuator) 1b objective lens (driven body) 3 servo LSI 3a tracking equalizer amplifier (drive signal generation means) 3b waveform shaping amplifier 3c low-pass filter (motor drive signal supply means) 5 low-pass filter 6 micro Computer (motor drive signal supply means, control means, counting means, correction means, detection means) 6g memory (storage means) 7 analog switch (motor drive signal supply means) 8 variable voltage power supply (motor drive signal supply means) 9 motor driver (Motor drive signal supply means) 10 Feed motor

Claims (1)

[Claims] 1. A pickup having a tracking actuator, a feed motor for moving the pickup in a direction perpendicular to a track direction of a recording medium disk, and tracking based on a recording medium read signal output from the pickup. A drive signal generating means for generating a drive signal for the actuator; and a drive signal input to the tracking actuator during a tracking operation of a driven body driven for tracking by the tracking actuator based on the drive signal for the tracking actuator. Detecting means for detecting an amount of displacement from a free center position, which is a position of the driven body when the driven body is not being moved, and when performing a search for a track to be scanned by the pickup, the driven body is positioned at the free center position. Dealt So that the said after controlling the tracking actuator based on the output of the detecting means, the pickup drive unit, characterized in that a control means for controlling the feed motor so that the search is performed.