JP3572055B2 - Disc playback device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pickup driving device for moving a pickup in a radial direction of a disk when information is reproduced from, for example, a disk as a recording medium.
[0002]
[Prior 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.
[0003]
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 to be realized.
[0004]
Therefore, in a conventional popular 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. .
[0005]
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 phase compensation amplifier 53a of a servo LSI 53, and a BTL (Balanced). A tracking servo loop T is configured by a Transformer Less) driver 54. A slide servo loop S is constituted by the pickup 51, the RF amplifier 52, the phase compensation amplifier 53a of the servo LSI 53, the low-pass filter 53b of the servo LSI 53, the motor driver 55, and the feed motor 56 composed of a DC brush motor. The servo LSI 53 is controlled by a microcomputer (hereinafter, referred to as a microcomputer) 57.
[0006]
In the above-described slide feed system, at the time of slide feed at the time of reproduction, a low-frequency component is passed through a low-pass filter 53b from an input signal to a BTL driver 54 for driving the tracking actuator coil 51a, that is, a TRD (tracking drive) signal. Is taken out. 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.
[0007]
In the above-described slide feed system, high-speed search by slide feed is performed by the track count method according to the procedure shown in FIG. 15 and the following.
[0008]
1. At the start time (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 a track cross value based on the track cross signal is set (point c).
[0011]
4. When the measured value of the counter reaches a predetermined value, the feed motor 56 is stopped (point d).
[0012]
5. After the pickup 51 is stopped by the back electromotive force brake of the feed motor 56 and the loss torque of the slide feed mechanism (period e), the tracking servo is turned on (point f).
[0013]
As described above, in the configuration using the DC brush motor as the feed motor 56, high-speed search by the track count method can be performed with relatively easy control.
[0014]
[Problems to be solved by the invention]
However, in the above-described conventional disk reproducing apparatus using a DC brush motor as the feed motor 56, when the voltage of the apparatus is reduced, the size is reduced and the power consumption is reduced, and when the seek speed is increased. Then, the following problems are caused.
[0015]
1) When seeking high-speed seeking in the track count search, if the power supply voltage of the feed motor 56 can be designed to be sufficiently high, as shown in FIG. / T characteristic), the usable range of the motor voltage Vm as a parameter is, for example, from 1 to 10 V, and the dynamic range is 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.
[0016]
On the other hand, if the power supply voltage of the feed motor 56 is designed to be, for example, about 5 V in order to reduce the voltage and power consumption, the motor voltage Vm becomes about 4 V due to a voltage drop in the motor driver 55 and the like. As a result, the dynamic range is about four times (12 dB). 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 becomes difficult to sufficiently reduce the acceleration at the very low speed during reproduction. As a result, the fine speed feed of the pickup 51 cannot be performed satisfactorily.
[0017]
JP-A-60-50674, JP-A-61-206976, and JP-A-62-149077 disclose a configuration in which a pulse voltage is supplied as a drive signal for the feed motor 56. It is difficult to satisfactorily drive the feed motor 56 and sufficiently suppress the acceleration of the fine feed of the pickup 51 only by supplying the voltage.
[0018]
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 becomes remarkable due to the increase of the self-resonance frequency and the increase of the resonance Q accompanying the miniaturization of the pickup 51.
[0019]
The vibration of the pickup 51 is generated as follows. When the tracking servo is ON, the tracking actuator coil 51a of the pickup 51 drives and controls the objective lens 51b in the disk radial direction. However, during a seek operation in which the tracking servo is turned off, the objective lens 51b that should be at the neutral position is displaced by acceleration and inertia of the objective lens 51b. Therefore, the pickup 51 vibrates during the seek and after the seek is completed.
[0020]
The above-described vibration of the pickup 51 causes an increase in the counting error and variation in the number of tracks in the track counting search, and hinders the speeding up of the search.
[0021]
3) When a high-speed seek is to be performed in the track count search, the track count set value for each disk reproducing device is considered in consideration of variations such as the N / T characteristics of the feed motor 56 and the loss torque of the slide feed mechanism. Control for correcting the table and learning is required. However, since the landing accuracy of the search in the track count system changes every time due to the following factors, it is not easy to correct the track count set value or to control by learning.
[0022]
The above factors are the eccentricity of the disk and the eccentricity of the disk mounting mechanism, that is, the eccentricity of the disk with respect to its rotation center, the resolution of the slide feed mechanism by the coking torque determined by the number of poles and the gear ratio of the motor 56, and the tracking. An erroneous count caused by a low S / N ratio of the track cross signal generated from the error signal, or an erroneous count of the track cross signal caused by the vibration of the pickup 51 described above.
[0023]
4) When a high-speed seek 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 only during the track count. However, when the track count method is not adopted, for example, a sensor composed of a photodetector and a reflector, or 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, there are variations in the N / T characteristics of the feed motor and 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. In addition, variation in landing accuracy due to vibration of the pickup remaining when the tracking servo is turned on cannot be avoided.
[0024]
[Means for Solving the Problems]
In order to solve the above problems, a pickup driving device of the present invention includes a pickup having a tracking actuator, a feed motor for moving the pickup in a direction perpendicular to a track direction of a disk as a recording medium, and an output from the pickup. Drive signal generating means for generating a drive signal for the tracking actuator based on the read signal of the recording medium, and detecting the amount of eccentricity of the disk as the recording medium with respect to the rotation center based on the drive signal for the tracking actuator. At the same time, during a tracking operation of the driven body driven for tracking by the tracking actuator, the amount of displacement from the free center position, which is the position of the driven body when no drive signal is input to the tracking actuator, is detected. Detecting means for detecting, based on the amount of eccentricity and the amount of displacement of the driven body detected by the detecting means, detecting an allowable movable amount of the driven body by a tracking actuator, based on the allowable movable amount , A tracking actuator and a feed motor are controlled.
[0025]
According to the configuration of the present invention, the control unit detects the allowable movable amount of the driven body by the tracking actuator based on the amount of eccentricity of the disk with respect to the rotation center and the amount of displacement of the driven body from the free center position. The movement of the pickup at the time of searching for a track to be scanned is controlled based on the allowable movable amount. Note that the allowable movable amount is, for example, a limit displacement amount at which a read signal from the pickup deteriorates when the displacement amount of the pickup, that is, the driven body becomes larger than that.
[0026]
That is, when the target track can be scanned only by moving the driven body within the allowable movable amount, the control unit controls only the tracking actuator to move the driven body to the target track position, and The scanning of the track is performed. On the other hand, if it is impossible to scan the target track only by moving the driven body within the allowable movable amount, the control means moves the pickup by the feed motor and then moves the driven body by the tracking actuator to the target track. To make the pickup scan the track.
[0027]
Therefore, in the present disk reproducing apparatus, a high-speed search can be performed safely without deteriorating a reproduced signal by making maximum use of the allowable movable amount of the driven body in the pickup.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment of the Invention]
An 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 having a tracking actuator coil (tracking actuator) 1a and an objective lens (driven body) 1b, an RF amplifier 2, and a tracking equalizer amplifier (drive) A tracking servo loop T is constituted by the signal generating means 3a and the actuator driver 4. Further, a pickup 1, an RF amplifier 2, a tracking error waveform shaping amplifier 3b, a tracking equalizer amplifier 3a, a low-pass filter (motor drive signal supply means) 3c, a low-pass filter 5, a microcomputer 6, an analog switch 7, a variable voltage power supply 8, a motor driver A slide servo loop S is configured by the feed motor 9 and the feed motor 10. The tracking equalizer amplifier 3a, the waveform shaping amplifier 3b, and the low-pass filter 3c are included in the servo LSI 3.
[0029]
The pickup 1 reads a signal recorded on a disc (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.
[0030]
The tracking equalizer amplifier 3 a generates a TRD (tracking drive) signal for performing tracking from a tracking error signal obtained from the pickup 1 via the RF amplifier 2 and supplies the TRD (tracking drive) signal to the actuator driver 4. The waveform shaping amplifier 3 b shapes the waveform of the tracking error signal obtained from the pickup 1 via the RF amplifier 2 to generate a TCRS (track cross) signal, and supplies this signal to the microcomputer 6. The low-pass filter 3c extracts a signal having a frequency component of about 0.5 to 5 Hz from the output of the tracking equalizer amplifier 3a, that is, the TRD 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.
[0031]
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.
[0032]
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.
[0033]
The microcomputer 6 controls the operation of the disc reproducing apparatus, and includes a counter input terminal 6a, input terminals 6b and 6c which are A / D (analog / digital conversion) input ports, and a D / A (digital / analog conversion) port. Output terminals 6d, 6e and 6f, and a rewritable memory (storage means) 6g.
[0034]
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. The TVD signal is input to the input terminal 6b, and the TRP signal is input to the input terminal 6c. 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.
[0035]
A TVDO (traverse drive output) signal is output from the output terminal 6d. This TVDO signal is a signal for controlling the rotation of the motor driver 9, that is, the rotation of 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 generates a TVDO signal 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.
[0036]
A PLM (play window) signal is output from the output terminal 6e. This PLM signal is an output of the motor driver 9, that is, a signal for turning on / off the feed motor 10. Here, the analog switch 7 is turned on / off by the H / L of the PLM signal, and the supply of the TVDO signal to the motor driver 9 is turned on / off. An SLDV (slide motor voltage control) signal is output from the output terminal 6f. This SLDV signal controls the output voltage of the variable voltage power supply 8.
[0037]
The analog switch 7 is for turning on / off the supply of the TVDO signal from the microcomputer 6 to the motor driver 9. 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 generates a motor voltage Vm for driving the feed motor 10 based on the voltage supplied from the variable voltage power supply 8 and the TVDO signal input from the microcomputer 6 via the analog switch 7, and generates the motor voltage Vm. This is supplied to the feed motor 10. Therefore, the 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.
[0038]
The feed motor 10 is composed of, for example, a DC brush motor and receives the motor voltage Vm to slide the pickup 1 in the radial direction of the disk.
[0039]
In the above configuration, the operation of the disc reproducing apparatus will be described below. At the time of reproduction, the microcomputer 6 performs control to slide 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 in the case where the slide feed mechanism and the feed motor 10 are not connected is shown. When the two 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.
[0040]
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 passage of time at the time of the very low-speed slide 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.
[0041]
The TVDO signal transitions in substantially the same manner as the TVD signal, as shown in FIG. 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.
[0042]
When the TVD signal reaches the sending start point, and similarly when the TVDO signal reaches the sending start point a, the PLM signal opens a window t having a certain time width, that is, turns on the analog switch 7 for a certain time t, A TVDO signal is provided to the motor driver 9. Further, the PLM signal keeps opening a window t having a certain time width at a certain interval T after the above-mentioned sending start point. On the other hand, when the pickup 1 approaches the reference point after passing the feed start point, that is, when the TVD signal moves toward the reference point after passing the feed start point, the PLM signal stops opening the window of a fixed time width. I do.
[0043]
The motor driver 9 generates a motor voltage Vm as a pulse signal 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 having the predetermined 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 does not exceed the upper limit point b of the TVDO signal, that is, the value corresponding to the upper limit value. 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.
[0044]
As described above, in the present disk reproducing apparatus, the feed motor 10 is driven by the motor voltage Vm composed of a pulse signal at the time of fine-speed feeding 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.
[0045]
Further, the motor voltage Vm at the feed start point is set to the minimum starting voltage of the feed motor to be used, and the motor voltage Vm is set to the upper limit motor voltage Vm given by 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 disc reproducing apparatus has a stable feed servo system in which the acceleration at the time of the very low speed feed during the reproduction is minimized and the hunting is suppressed.
[0046]
In the configuration of FIG. 1, when a BTL (Balanced Transformer Less) driver IC is used as the motor driver 9, an output proportional to the TVDO signal can be obtained from the BTL driver IC, so that the variable voltage power supply 8 is provided as a separate circuit. There is no need, and the SLDV signal as the voltage control signal becomes unnecessary.
[0047]
Further, in the present disk reproducing apparatus, as shown in FIG. 3, a motor driver 21 is provided instead of the motor driver 9 shown in FIG. 1, and an LC filter 22 is provided between the motor driver 21 and the feed motor 10. It may be configured. The motor driver 21 is of a PWM (Puls Wids Modulation) control type. The LC filter 22 is provided to remove interference noise and unnecessary radiation from peripheral components due to the PWM component.
[0048]
The motor driver 21 has an ST / SP terminal 21a for inputting start / stop of operation. The ST / SP terminal 21a is provided in a general PWM driver IC. The PLM signal is input to the ST / SP terminal 21a. 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.
[0049]
The motor driver 21 changes the duty ratio of the output pulse signal according to the magnitude of 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. 5A becomes the DC voltage shown in FIG. Voltage.
[0050]
As described above, in the present disk reproducing apparatus, the pulse voltage as the motor voltage Vm output from the motor driver 21 changes the duty ratio according to the magnitude of the TVDO signal.
[0051]
[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIG. 1, FIG. 2, FIG. 6, and FIG. 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 a stable feed servo is realized. . In the disc reproducing apparatus according to the present embodiment, in order to realize more precise fine-speed slide feed, attention is paid to the characteristic of the feed motor 10 so that adverse effects due to this characteristic can be avoided.
[0052]
The feed motor 10 composed of a DC brush motor has the following three characteristics: N / T characteristics (rotational speed / torque characteristics), coking torque, and loss torque, as described below.
[0053]
N / T characteristics (rotation speed / torque characteristics)
An example of the N / T characteristic 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.
[0054]
Coking torque
The 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.
[0055]
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. The rotor 31 tends to stop at the position shown in FIG.
[0056]
FIG. 6A shows a state in which the rotor coil 31a is most attracted to the magnet 32b by the magnetic force. This state is the same when the rotor coil 31b or the rotor coil 31c is most attracted to the magnet 32b, or when any of the rotor coils 31a to 31c is most attracted to the magnet 32a. 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 shown in FIG. .
[0057]
FIG. 6B shows a state in which one of the rotor coils 31a to 31c is drawn to the magnet 32a and the other is drawn 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 twelve positions where the torque is high, which is a characteristic called coking torque.
[0058]
This coking torque greatly varies in each motor due to the assembling accuracy of the rotor and the magnet, the management of the magnetization of the magnet, and the like.
[0059]
Loss torque
The 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. Therefore, 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.
[0060]
As described above, the individual feed motors 10 have various variations in each characteristic. Therefore, in the present disk reproducing apparatus, the following control in the control shown in FIG. 2 described above is performed 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.
[0061]
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 transmitted to the motor driver 9 shown in FIG. After that, it is supplied to the feed motor 10 as the motor voltage Vm. In this example, it is assumed that the motor driver 9 is of the inverting input AMP type.
[0062]
In this embodiment, the following control is performed to supply the motor 10 with the motor voltage Vm having the waveform shown in FIG.
[0063]
1. The microcomputer 6 takes in the TVD signal indicating the average shift amount of the pickup 1 (the solid line portion of the TVD signal shown in FIG. 2) into the input terminal 6b which is the A / D port shown in FIG. Next, the microcomputer 6 obtains a TVDO signal as shown in FIG. 2 by an operation based on the fetched value or by a software table, and outputs this signal from an output terminal 6d which is a D / A port.
[0064]
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 widths T1 to Tn is inversely proportional to the input value (variations have been corrected based on experiments). From the output terminal 6e as a PLM signal.
[0065]
3. The TVDO signal is input to the analog switch 7, and the analog switch 7 is turned on / off by the PLM signal to be converted into a pulse height TVDO signal having pulse widths t1 to tn. When this TVDO signal is input to the motor driver 9, the motor voltage Vm shown in FIG. 7 is applied to the feed motor 10.
[0066]
As described above, the pulse width of the motor voltage Vm increases when the voltage value, that is, the peak value is low, and the pulse width decreases when the peak value is low. Thereby, the pickup 1 can be accurately moved by the feed motor 10 and the feed motor 10 can be moved at that time 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. It can be operated at a minimum starting voltage (the minimum starting voltage of the motor is almost proportional to the load at that time). Therefore, the acceleration of the pickup 1 can be minimized, and the pickup 1 can be sent with the minimum movement amount determined by the gear ratio of the mechanical system.
[0067]
[Embodiment 3]
Still another embodiment of the present invention will be described below with reference to FIGS. 1 and 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.
[0068]
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 the search.
[0069]
Eccentricity of a disk with respect to its center of rotation caused by eccentricity of the disk and eccentricity in a chucking state due to low chucking accuracy of a disk chucking mechanism.
[0070]
The resolution of the slide feed by the feed motor and the gear ratio of the slide feed mechanism.
[0071]
Backlash of slide feed mechanism.
[0072]
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 amount of 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 amount of eccentricity H of the CD 41 is 70 μm, and the amount of eccentricity due to chucking of the disk chucking mechanism is 58 μm. In this case, the maximum eccentricity due to both eccentricities is 128 μm. On the other hand, the track pitch of the CD 41 is 1.6 μm. Accordingly, the search accuracy in this case is 80 tracks by the calculation of 128 ÷ 1.6. That is, the search accuracy at an eccentric amount of 128 μm is ± 80 tracks (books).
[0073]
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, assuming that the gear ratio of the slide feed mechanism is 0.6 mm / rotation and the polarization point at which the coking torque acts, that is, the rotor 31 stops at twelve points as described above, the resolution is 0.6 mm ÷ 12. Is 50 μm. At this resolution, if the track pitch of the CD is 1.6 μm, a search error of ± 50 μm, that is, ± 31 search errors in the track will occur.
[0074]
Next, the effect of the backlash on search accuracy will be described. In general, when the clearance is designed to be 0 (zero) in the meshing of the gears, the friction increases and the gears cannot rotate. For this reason, a minimum clearance is provided between the meshing teeth. In addition, the shaft of the spur gear also requires clearance, and these clearances cause backlash. Therefore, for example, a backlash of 50 μm results in a maximum of 31 search errors in the number of CD tracks.
[0075]
In the disc 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.
[0076]
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 in a disk reproducing apparatus using a motor which is a design center in the specification 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 sliding the pickup 1 in the tracking servo OFF state when searching for an arbitrary target track, 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 drawing as a table, and subtract the number of tracks in the standard table from the number of target tracks to obtain the set track count. The number of tracks is counted by the microcomputer 6 as counting means based on the TCRS signal.
[0077]
The feed motor 10 used in the disk reproducing apparatus varies, and as shown in the graph showing the number of rotations and the track count frequency in FIG. 9, not only the standard motor h but also the motor i having a large number of rotations and the number of rotations. Motor j exists. 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, it is necessary to perform search learning according to the characteristics of each of the motors h to j, and correct the standard table based on the learning.
[0078]
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 number of track jumps for each search, that is, the track count. 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 made to exactly match the center of the landing error for each search, and the search is slowed by the deviation.
[0079]
In order to avoid the influence of the search error due to the eccentricity, the coking 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.
[0080]
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 is a standard table included in a disk reproducing apparatus having a design-centered feed motor 10 (hereinafter, referred to as a design-centered apparatus). Although the distribution of the landing error for each search is different from the normal distribution, there are about ± 100 landing error factors due to eccentricity for each search, and about ± 50 landing error factors due to other coking torque and backlash. When there is a total of ± 150 landing errors for each search, the distribution is slightly similar to the normal distribution as shown in FIG.
[0081]
Here, first, learning and correction of the standard table in the design-centric 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. Accordingly, the number of highly 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.
[0082]
However, in practice, the characteristics of the feed motor 10 of an arbitrary disc reproducing apparatus other than the disc reproducing apparatus having the design-centered feed motor 10 and the characteristics of the disc with respect to the rotation center when the disc is mounted on the disc reproducing apparatus. The amount of eccentricity is unknown.
[0083]
Therefore, in the learning / correction in the disc reproducing apparatus, among elements that cause a search error in the track count method, attention is paid to an element having a large ratio of occurrence of the search error. A non-learning area EA1 is a range in which a search error due to an element is high. 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.
[0084]
Next, the operation for this will be described with reference to FIG. Here, the above-described standard table A is set in advance in the disc reproducing apparatus, and the operation of learning and correcting the standard table A to the target center table B will be described. If a landing error within 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.
[0085]
On the other hand, in the above search, for example, it is assumed that a landing error at the position B first occurs. In this disc reproducing apparatus, since the position of the target center table is position B, there is a high probability that a landing error in the range EB2 of positions 2 and 3, that is, a landing error at position B will occur. Since the position B is a position other than the non-learning region in the landing error distribution DA 1, that is, the position of the learning region, the standard table is first shifted one position B from the position A (landing error distribution DA 1) at that time. It is learned and corrected to the moved position 1 (landing error distribution D1).
[0086]
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) moved from the position 1 to the position 3 by one.
[0087]
Further, after that, if the landing error at the position 4 occurs, although the probability is relatively low, this position is a learning area of the landing error distribution D2. Therefore, the table reads from the position 2 to the position B (landing error distribution B 1), That is, learning and correction are performed on the target center table B.
[0088]
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, and an appropriate non-learning area is set. Learning and correcting the table. 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 search due to eccentricity in each disk chucking in the disk reproducing apparatus are reduced. The effect is suppressed. Therefore, a stable high-speed search can be realized.
[0089]
[Embodiment 4]
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.
[0090]
In the specification 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 low-frequency sensitivity (1 Hz sensitivity). The low-frequency sensitivity has a unit of V / μm, and is usually about 10 mV / μm. If the above-mentioned low-pass 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 can be obtained 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.
[0091]
FIG. 12 illustrates a method of detecting the low-frequency sensitivity of the tracking actuator. The vertical axis in the figure is a TRP (tracking position) signal. This TRP signal is a signal obtained by passing a TRD (tracking drive) signal through the low-pass filter 5 as described in FIG. 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.
[0092]
The zero (0) point on the vertical axis shown in FIG. 12 is a position where the current for driving the pickup 1 does not flow in the tracking actuator coil 1a in any of the radially inward and outward directions of the disk (hereinafter, the pickup 1). Is referred to as the free center. Note that the horizontal axis in the figure indicates the elapsed time.
[0093]
When the low-frequency sensitivity is obtained, first, when the disk reproducing apparatus is in the reproducing state of the tracking servo ON, and when the pickup 1 is near the free center, the slide movement of the pickup 1 by the feed motor 10 is performed. Is stopped, and the TRP signal 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.
[0094]
Next, the microcomputer 6 obtains the TRP value of the average center position of the pickup 1 in the area A from the TRP signal. This TRP value is an average value of the captured TRP signals or an intermediate value between the maximum value and the minimum value.
[0095]
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. Therefore, when 63 track jumps are 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.
[0096]
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.
[0097]
On the other hand, a 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 low-frequency sensitivity obtained from the difference standard value of the TRP value. This low-frequency sensitivity is obtained by calculating (difference in TRP value) / (amount of track jump). Therefore, 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 from (difference in TRP value obtained by measurement) / (amount of track jump).
[0098]
Next, the microcomputer 6 calculates the amount of 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 and minimum values 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 operation is
Total eccentricity = (maximum value-minimum value) / (low-frequency sensitivity)
It is.
[0099]
In the present disk reproducing apparatus, based on the eccentricity, the number of search errors in the track count method or another method assumed from the eccentricity is calculated, and the number of search errors in the search is integrated with other search error factors. Determine the number of tracks in the non-learning area. The number of tracks is determined by calculation or based on a dedicated table stored in the memory 6g of the microcomputer 6 in advance.
[0100]
As described above, in the present disk reproducing apparatus, it is possible to accurately obtain the eccentric amount, which is particularly uncertain as a search error factor and occupies a relatively large ratio, and based on the eccentric amount, Learning and correction can be performed well. As a result, a good search for the disk can be performed.
[0101]
[Embodiment 5]
Still another embodiment of the present invention will be described below with reference to FIGS. In the present disk reproducing apparatus, by detecting the TRP signal and the low-frequency sensitivity of the tracking actuator, the displacement amount of the pickup 1 from the free center position can be known almost in real time when the tracking servo is ON. Can be. 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, and such a delay is caused in the following operation characteristic of the present disk reproducing apparatus. 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 eccentricity obtained as described above. Thus, the movable amount in the disk radial direction can be utilized to the maximum. This function will be described in detail below.
[0102]
For example, in the present disk reproducing apparatus, as shown in FIG. 13, the allowable movable amount in the disk radial direction due to the lens kick of the pickup 1 is ± 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. And Here, the permissible movable amount in the disk radial direction is a limit displacement amount at which a read signal from the pickup 1 deteriorates when the displacement amount of the pickup 1 in the disk radial direction is further increased.
[0103]
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 set to, for example, 100 μm / 250 mV (TRP). This means that the pickup 1 is displaced by 100 μm with a TRP signal of 250 mV. 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.
[0104]
Here, for example, in a CD device, 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. 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.
[0105]
Further, in the conventional CD device, immediately after the search, in order to quickly return the pickup displaced in the radial direction of the disk to the vicinity of the free center position, the feed servo of the pickup based on the TVD signal is performed. However, the TVD signal is a signal that has passed through a low-pass filter that cuts off around 1 Hz so as to indicate the average center position of the pickup, 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.
[0106]
On the other hand, in the present disk reproducing apparatus, the TRP signal is also used as the second signal of the feed servo. Therefore, when the average center of the pickup 1 is located near the free center position in FIG. It is possible to detect that the remaining 300 μm after subtracting the total eccentricity of 100 μm is the allowable movable amount due to the lens kick. Also, if 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. It can immediately be seen that the movable amount is the remaining 100 μm. On the other hand, it is immediately understood that the allowable movable amount due to the lens kick inward in the radial direction of the disk is 300 μm. If necessary, the microcomputer 6 can know the average center position of the pickup 1 by observing one cycle of the TRP signal. Further, at the double speed or higher, the average center position can be clearly known earlier than in the case of the TVD signal.
[0107]
Also, when a search by a lens kick is necessary at a position radially outward of the disk from the point M clearly, a slide feed based on the TRP signal is performed, and then the amount of the slide is reduced. If the lens kick is performed within the range, the lens kick can be safely performed.
[0108]
As described above, in the present disk reproducing apparatus, when performing a search by a lens kick, the allowable movable amount of the pickup 1 in the disk radial direction can be maximized, and the high-speed operation can be performed without deteriorating the reproduction signal. Search can be performed safely.
[0109]
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. As described above, the slide movement of the pickup 1 is performed with the tracking servo turned off. In this case, the pickup 1 vibrates in the radial direction of the disk due to the acceleration of the slide feed. Although this vibration is relatively unlikely to occur in the case of a radial direction balance type pickup, even with such a pickup, it becomes remarkable in slide feeding from a position largely displaced from the free center position. When the vibration becomes remarkable, the vibration is also added to the above-mentioned main factors that degrade the search accuracy, such as eccentricity, the resolution of the slide feed, and the backlash of the slide feed mechanism.
[0110]
For example, if vibration of the pickup 1 of ± 50 μm remains immediately before the tracking servo is turned ON after the slide feed is completed, a search error of ± 31 tracks occurs in the CD device.
[0111]
Here, in the present disk reproducing apparatus, the amount of displacement of the pickup 1 from the free center position can be known by the configuration for detecting the TRP 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 a 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 slides the pickup 1 toward the free center position based on the PLM signal and the SLDV signal shown in FIG. When the vehicle reaches the vicinity of the position, the search is started immediately.
[0112]
【The invention's effect】
As described above, the pickup driving device of the present invention includes a pickup having a tracking actuator, a feed motor for moving the pickup in a direction perpendicular to the track direction of a disk serving as a recording medium, and a recording medium output from the pickup. Drive signal generation means for generating a drive signal for a tracking actuator based on a read signal of the tracking actuator; detecting an eccentric amount of a disk serving as a recording medium with respect to the rotation center thereof based on the drive signal of 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 driving signal is not input to the tracking actuator during a tracking operation of the driven body driven for tracking by Detecting an allowable movable amount of the driven body by a tracking actuator based on the eccentric amount and the displacement amount of the driven body detected by the detecting means; This is a configuration for controlling the feed motor.
[0113]
This makes it possible to perform the high-speed search safely without deteriorating the reproduction signal by making the most of the allowable movable amount of the driven body in the pickup.
[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 an explanatory diagram showing a relationship among a TVD signal, a TVDO signal, a PLM signal, and a motor voltage Vm in the disc reproducing apparatus shown in FIG.
FIG. 3 is a schematic circuit diagram showing a main part of the disk reproducing apparatus 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-described 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. 5) is a waveform diagram of the motor voltage Vm obtained from the PWM signal shown in FIG. 5A 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 center of rotation 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 that is a conventional pickup driving device.
FIG. 15 is a diagram showing a relationship between a track cross signal used for a search in 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 a 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]
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. Microcomputer (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)

A pickup having a tracking actuator;
A feed motor for moving the pickup in a direction orthogonal to a track direction of a disk serving as a recording medium;
Drive signal generation means for generating a drive signal for a tracking actuator based on a read signal of a recording medium output from the pickup;
Based on the drive signal of the tracking actuator, the amount of eccentricity of the disk serving as the recording medium with respect to the rotation center is detected, and the tracking actuator is driven by the tracking actuator during a tracking operation of the driven body driven for tracking by 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 signal is not input;
Based on the amount of eccentricity and the amount of displacement of the driven body detected by the detecting means, an allowable movable amount of the driven body by the tracking actuator is detected. A pickup driving device, comprising: control means for controlling a motor.

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