JP2817480B2 - Tracking control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device such as an optical disk device for recording and reproducing information on a record carrier having a large number of information tracks by using a light beam emitted from a semiconductor laser or the like.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing a tracking control device in a conventional optical disk device. The record carrier 1 is attached to a rotation shaft of a motor 2 and rotates at a predetermined rotation speed. On the record carrier 1, a track having a width of 0.6 μm and a track pitch of 1.6 μm on which a signal is recorded is spirally provided. A light beam 4 generated from a light source 3 such as a semiconductor laser is collimated by a coupling lens 5, passes through a polarizing beam splitter 6, a 波長 wavelength plate 7, is reflected by a total reflection mirror 8, and is converged by a converging lens 10. And is irradiated onto the record carrier 1. The converging lens 10 is attached to the movable section 40. The movable section 40 has a bearing, and is configured to be able to move up and down along a sliding shaft 51 attached to the transfer table 13 and to be rotatable about the sliding shaft 51.
The movable section 40 is attached to the transfer table 13 via a rubber 52, and is adjusted so that the optical axis of the light beam 4 substantially matches the optical axis of the converging lens 10. The transfer table 13 can move on the base 53 in the radial direction of the record carrier 1. The movable portion 40 receives a current through the coil 313, and the coil 313 receives an electromagnetic force.
It can move up and down along. The transfer table 13 to which the total reflection mirror 8 and the converging lens 10 are attached is configured such that when a current flows through the coil 14, the coil 14 receives an electromagnetic force and moves in the radial direction of the record carrier 1. In addition, the movable portion 40 is configured to be able to rotate around the sliding shaft 51 when the coil 89 receives an electromagnetic force when a current flows through the coil 89. Therefore, the converging lens 10 attached to the movable section 40 can move in the radial direction of the record carrier 1 within a range of several hundred μm. Hereinafter, the configuration in which the converging lens 10 is driven in the radial direction of the record carrier 1 by passing a current through the coil 89 is referred to as a tracking actuator.

The reflected light 9 reflected on the record carrier 1 passes through a converging lens 10 and is reflected on a total reflection mirror 8 to
After passing through the 波長 wavelength plate 7, the polarization beam splitter 6
And is incident on the detection lens 81. Detection lens 81
Is reflected on the photodetector 303. The photodetector 303 has a two-segment structure, and its output is input to amplifiers 304 and 305, respectively.
Outputs of the amplifiers 304 and 305 are input to respective terminals of the differential amplifier 306, and the differential amplifier 306 outputs a signal corresponding to a difference between the two signals. The above-described configuration generally constitutes a detection system called a knife edge method, and the output of the differential amplifier 306 is a focus indicating the shift between the focus position of the light beam 4 narrowed by the converging lens 10 and the record carrier 1. It becomes an error signal. In response to this signal, the coil 31
The focus is controlled so that the focal point of the light beam 4 is always positioned on the record carrier 1 by flowing a current through the lens 3 and driving the converging lens 10 in the vertical direction. Note that the phase compensation circuit 307
Is a circuit for securing a phase margin of the focus control system, and the drive circuit 311 is a circuit for performing power amplification.

A light source 3, a coupling lens 5, a polarizing beam splitter 6, a quarter-wave plate 7, a detection lens 81,
The reflection mirror 82 and the photodetectors 11, 303 are fixed to the base 53 of the apparatus. The portion of the reflected light 9 that has passed through the detection lens 81 is irradiated onto the photodetector 11. The photodetector 11 has a two-part structure, and its output is input to amplifiers 16 and 17, respectively. Outputs of the amplifiers 16 and 17 are input to respective terminals of the differential amplifier 18, and
The differential amplifier 18 outputs a signal according to the difference between the two signals.
The output of the differential amplifier 18 becomes a tracking error signal (hereinafter, referred to as a TE signal) indicating a positional deviation between the light beam 4 converged on the record carrier 1 and the track.

The output signal of the differential amplifier 18 is supplied to a phase compensation filter 30 for compensating the phase of the tracking control system.
Input to 0. The output of the phase compensation filter 300 is supplied to the drive circuit 35 for power amplification and the equivalent filter 301.
Is input to The drive circuit 35 allows a current corresponding to the input signal to flow through the coil 89. Therefore, the converging lens 10 is driven by a current according to the TE signal, and tracking control is performed so that the light beam 4 converged on the record carrier 1 is always positioned on the track.

[0006] The equivalent filter 301 is a convergent lens 1 held by the movable section 40 for a drive current flowing through the coil 89.
This is a filter having a transfer function equal to the relationship of displacement of zero. Therefore, the output of the equivalent filter 301 indicates the displacement of the converging lens 10.

[0007] In the configuration shown in FIG.
Has a spring property and a viscosity, so that it has a secondary transfer function as shown in (Equation 1). In (Equation 1), Ke indicates a spring constant, Kf indicates a thrust constant, D indicates a viscosity coefficient, and m indicates a mass of the movable unit 40 including the converging lens 10. Therefore, the equivalent filter 301 is an electric circuit having the transfer function shown in (Equation 1).

[0008]

(Equation 1)

The output of the equivalent filter 301 is
Is input to the drive circuit 36 via a phase compensation filter 302 for securing a phase margin of the control system.

[0010] The drive circuit 36 causes a current corresponding to the input signal to flow through the coil 14. Therefore, the transfer table 13 moves in a direction in which the displacement of the converging lens 10 is reduced to zero.

In general, in a TE detection method such as a push-pull method, when the converging lens 10 is displaced,
If the optical axis of the light beam 4 and the optical axis of the light beam 4 incident on the converging lens 10 are shifted, an error occurs in the TE signal. Therefore, a method of reducing the displacement of the converging lens 10 with the above-described configuration is performed. In general, the control band of the tracking actuator is about 2 kHz, and the control band of the transfer table 13 is about several hundred Hz.

[0012]

Since the viscosity coefficient of rubber or the like changes with temperature, the characteristics of the tracking actuator change, and a difference occurs with the transfer function of the equivalent filter. For this reason, the displacement of the convergent lens cannot be reduced, so that accurate tracking control cannot be performed,
When the difference increases, the phase margin of the control system of the transfer table decreases, and the tracking control system may become unstable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a tracking control device capable of performing stable tracking control even at a low temperature.

[0014]

In order to solve the above-mentioned problems, a tracking device according to the present invention comprises: a track shift detecting means for detecting a positional shift between a light beam irradiated on a record carrier and a track; A first moving means for moving the light beam across the track; a second moving means for moving the first moving means across the track; and First control means for driving the first moving means so that the light beam on the record carrier is positioned on the track; and driving the second moving means in response to a signal from the track deviation detecting means. To control the position of the first moving means
Control means and the signal level of the track deviation detecting means.
Detected that the signal has exceeded the specified range, and generates a malfunction detection signal.
Determining means for outputting, the first and second control means
A malfunction detection signal from the determination means when
Is output, the first moving means is heated.

[0015]

According to the present invention, stable tracking control can be performed even at a low temperature by heating the first moving means to change the characteristics of the first moving means so as to be substantially the same as the characteristics of the equivalent filter. Become.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of a tracking control device in an optical disk device according to an embodiment of the present invention will be described below. In FIGS. 1 and 7 in each embodiment, the transfer function of the equivalent filter 301 depends on the temperature of the rubber 52. The description will be made assuming that the transfer function of the tracking actuator at 15 ° C. is set and that the temperature near the rubber 52 is 5 ° C. Further, a phase compensation filter 3 for securing a phase margin of a control system of the transfer table 13 is provided.
02 is designed so that a sufficient phase margin can be ensured in the transfer characteristics of the tracking actuator when the temperature of the rubber 52 is 10 ° C. or higher and the control system is stabilized.

Hereinafter, a tracking control device in an optical disk device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a book diagram of a focus control device and a tracking control device of an optical disk device according to an embodiment of the present invention. Note that the same components as those in FIG.

Switches 308 and 309 are switches for switching ON / OFF of the tracking control and the control of the transfer table 13, respectively, and are configured to be closed when the control terminal C is at a high level. Switches 308 and 3
09 is a control terminal C of the microcomputer 37
It is connected to the. The oscillator 312 generates a sine wave of a predetermined level and outputs the sine wave to the input terminal B of the switch 310. The output signal of the phase compensation filter 307 of the focus control system is input to the input terminal A of the switch 310.
The switch 310 connects the input terminal A and the output terminal D when the control terminal E is at the high level, connects the input terminal C and the output terminal D when the control terminal E is at the low level, and inputs the input terminal B when the control terminal E is at the middle level. And the output terminal D are connected. The control terminal E is connected to the microcomputer 37 via a control line 314. The input terminal C receives a zero-level signal. The temperature sensor 44 measures the temperature near the rubber 52.
The temperature is defined as Wa. The temperature data Wa is taken into the microcomputer 37 via the data line 53. The microcomputer 37 takes in the temperature data of the temperature sensor 44 via the data line 53 before operating the focus control. In this embodiment, the acquired temperature data Wa is 5 ° C. The temperature of rubber 52 is 5 ° C
In the transfer characteristic of the tracking actuator in the above, the phase margin of the control system of the transfer table 13 cannot be secured. Therefore,
The microcomputer 37 is connected to the control line 31
4 is set to the middle level for a predetermined period. The predetermined period is defined as Tb. Therefore, the focus control coil 3
In 13, a current flows according to the output signal of the oscillator 312. The coil 313 generates heat by the application of the current, and the temperature of the movable section 40 rises. Further, the temperature of the rubber 52 attached to the movable section 40 also increases. The current application time or current value is set to a value at which the temperature of the rubber 52 increases from 5 ° C. to 10 ° C. Thereafter, the control line 314 is set to the high level to perform the focus control, and then the control lines 318 and 315 are set to the high level to operate the tracking control and the control of the transfer table 13.
In a state where the focus control and the tracking control are operating, the temperature of the rubber 52 does not become lower than 10 ° C. because the heat is generated by the current constantly flowing through the coils 313 and 89. Therefore, the phase margin of the control system of the transfer table 13 is secured. That is, the tracking control system does not become unstable. FIG. 2 shows a flow of the operation of the microcomputer 37 described above.

Next, the phase compensation filter 307 will be described in detail. FIG. 3 shows the configuration of the phase compensation filter 307. The input terminal 100 is connected to the data line 48 in FIG. The output terminal 102 is connected to the data line 49 in FIG. By appropriately setting the capacitor 103 and the resistors 104 and 105, a phase lead characteristic for securing a phase margin of the focus control system can be realized. This characteristic is shown in FIG. The characteristic (a) indicates the gain, and the characteristic (b) indicates the phase. In both of the characteristics (a) and (b), the horizontal axis indicates frequency. Note that the gain is indicated by a dB value, and the frequency is indicated by a logarithm. The gain intersection of the focus control system is generally 2 kHz.
It is about z, and has a characteristic that the phase advances near 2 kHz. The configuration and operation of the phase compensation filter 300 for tracking control are almost the same as those of the phase compensation filter 307 for focus control, and thus description thereof is omitted. Transfer table 1
Phase compensation filter 302 for phase compensation of the control system 3
Is the same as the configuration of the phase compensation filter 307 of the focus control system, and the description is omitted. Since the gain intersection of the control system of the transfer table 13 is generally about several hundred Hz,
The phase advances in the vicinity of the frequency.

Next, the operation of the equivalent filter 301 will be described in detail. FIG. 5 shows the configuration of the equivalent filter 301. The input terminal 200 is connected to the data line 350 of FIG. The output terminal 203 is connected to the data line 50 in FIG. Capacitor 201, coil 204 and resistor 2
02 has been described in the conventional example by appropriately setting (Equation 1)
Characteristics similar to the above transfer function can be realized.

Next, the characteristics of the tracking actuator will be described. FIG. 6 shows an example of a transfer function of the displacement of the converging lens 10 held by the movable section 40 with respect to the drive current flowing through the coil 89 shown in FIG. The characteristic (a) indicates the gain, and the characteristic (b) indicates the phase. In both of the characteristics (a) and (b), the horizontal axis indicates frequency. Note that the gain is indicated by a dB value, and the frequency is indicated by a logarithm. The frequency f indicates the frequency at the gain intersection of the control system of the transfer table 13. Generally, as the temperature increases, the primary resonance frequency decreases and the Mp value increases. Here, a decrease in the phase margin caused by the difference between the transfer function of the equivalent filter 301 and the transfer function of the tracking actuator will be described using the characteristic (b). Note that, as described above, the equivalent filter 3
The characteristics of No. 01 are equal to the characteristics of the tracking actuator at 15 ° C. Therefore, when the temperature of the rubber 52 is 1
In the case of the tracking actuator at 5 ° C., since the transfer function of the equivalent filter 301 matches the transfer function of the tracking actuator, the reduction of the equivalent phase margin is zero. In the case of 10 ° C., the phase shift at the gain intersection frequency f is D1. Therefore, the phase margin decreases by D1. Similarly, in the case of 5 ° C., the temperature decreases by D2. In other words, as the temperature decreases, the phase margin decreases, and the control system of the transfer table 13 becomes unstable, so that the tracking control system also becomes unstable. In this embodiment, as described at the beginning of the description of the embodiment, when the temperature is 10 ° C. or more, that is, when the decrease in the phase margin is within D1, a sufficient phase margin can be secured by the phase compensation filter 302.
If the temperature is lower than 0 ° C., a sufficient phase margin cannot be secured.

In this embodiment, the current application time is changed in accordance with the temperature. However, the current application may be performed at a predetermined temperature or lower, and the current application time and level may be fixed at predetermined values. In this case, the processing of the microcomputer 37 is simplified. Further, the temperature sensor 44 is provided and the heating is performed only when the temperature is low. However, the heating may be always performed regardless of the temperature. In this case, the temperature sensor 44 becomes unnecessary.

Hereinafter, a tracking control device in an optical disk device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 7 shows a book diagram of the focus control device and the tracking control device of the optical disk device in the embodiment of the present invention. Note that the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

The TE signal output from the differential amplifier 18 is
The signal is input to an input terminal A of a window comparator 316 that detects that the level of the TE signal falls within a predetermined range. The window comparator 316 sets the output terminal B to a high level when the TE signal exceeds a predetermined level.
That is, it is determined whether the tracking control is operating normally based on the fact that the level of the TE signal is within a predetermined range. The output terminal B of the window comparator 316 is connected to the microcomputer 37 via the data line 317. The microcomputer 37 sets the control line 314 to a high level to perform focus control, and then sets the control lines 318 and 315 to a high level to operate tracking control and control of the transfer table 13. The microcomputer 37 takes in the output signal of the window comparator 316 via the data line 317 after a lapse of a predetermined time Tc after operating the tracking control and the control of the transfer table 13. The output signal of the window comparator 316 is called a TR-NG signal. When the TR-NG signal is continuously at the low level during the predetermined period Td, the tracking control is operating normally. When the TR-NG signal is at the high level, the control lines 318 and 315 are set to the low level. Then, the tracking control and the control of the transfer table 13 are disabled, and then the control line 314 is set to low level to disable the focus control.

In this embodiment, the temperature of the rubber 52 is 5 ° C., and the phase margin of the control system of the transfer table 13 cannot be secured with the transfer characteristic of the tracking actuator at 5 ° C.
Therefore, the tracking control system becomes unstable, and the TE signal deviates from zero level. Therefore, the TR-NG signal becomes high level. Therefore, the microcomputer 37
Transmits the temperature data of the temperature sensor 44 to the data line 53
Ingest through. In this embodiment, the acquired temperature data is 5 ° C. The microcomputer 37 determines that the cause of the instability of the tracking control system is a low temperature because the acquired temperature data is 5 ° C., and sets the control line 314 to the middle level for a predetermined period. The following operation is the same as that of the first embodiment, and the description is omitted. 8 and 2 show the flow of the operation of the microcomputer 37 described above. The timer in FIG. 8 is for measuring the above-mentioned predetermined period Td. When reset, measurement starts again.

FIG. 9 is a block diagram of the window comparator 316. The input terminal 400 is connected to the data line 319 of FIG. 7, and the output terminal 401 is connected to the data line 317 of FIG.
Connected to each other. The input terminal 400 is connected to the A terminal of the comparator 402 and the B terminal of the comparator 403. The B terminal of the comparator 402 is connected to a reference power supply 404 of level VH. Therefore, the level at the B end is VH. A of the comparator 403
The terminal is connected to a reference power supply 405 of level VL.
The level of the A terminal is -VL due to the polarity of the reference power supply 405.
It has become. The comparators 402 and 403 are configured to output a high level when the level of the A terminal is higher than the level of the B terminal. The output signals of the comparators 402 and 403 are input to the OR circuit 406.
The OR circuit 406 outputs a high level when either or both of the input signals are at a high level. The output of the OR circuit 406 is connected to the output terminal 401. Next, the operation of the window comparator 316 will be described using the waveforms shown in FIG. The waveform (a) in FIG. 10 shows an example of the TE signal. A period A indicates a period in which the tracking control and the control of the transfer table 13 are not performed, and a period B indicates a case in which the operation is performed. Note that the case where the tracking control is unstable and the control system is oscillating is shown. Waveforms (b) and (c) show output waveforms of comparators 402 and 403, respectively. The waveform (d) shows the output waveform of the OR circuit 406. When the tracking control system oscillates during the period B, the output signal becomes high level intermittently, so that it is possible to detect that the tracking control system is oscillating.

A window comparator 316 for judging whether the tracking control is operating normally is provided. The focus comparator is used only when it is detected that the tracking control does not operate normally and the temperature is lower than the output of the temperature sensor 44. By applying a current to the coil 313 and heating the coil 313, heating does not occur even though there is no need for heating due to detection errors of the temperature sensor 44 and variations in the characteristics of the tracking actuator. Therefore, the time for operating the tracking control is reduced.

In this embodiment, the temperature sensor 44 is provided and heating is performed only when the temperature is low. However, if the tracking control does not operate normally regardless of the temperature, heating may be performed at all times. In this case, the temperature sensor 44 becomes unnecessary.

In the first and second embodiments, a current is applied to the focus control coil 313 to heat it. However, a tracking control coil 89 can be used. Further, the coil 313 for focus control and the coil 89 for tracking control can be used at the same time. In addition, a dedicated heating element can be used.

[0032]

According to the present invention, the focus control coil 31 is provided.
3 to raise the temperature of the rubber 52 by applying a current,
Even at a low temperature, the transfer function of the equivalent filter 301 and the transfer function of the tracking actuator can be substantially matched, and stable tracking control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a first embodiment of the present invention;

FIG. 2 is a flowchart for explaining processing of a microcomputer according to the embodiment;

FIG. 3 is a block diagram of a phase compensation filter according to the embodiment.

FIG. 4 is a characteristic diagram of a phase compensation filter according to the embodiment.

FIG. 5 is a block diagram of an equivalent filter in the embodiment.

FIG. 6 is a characteristic diagram of the tracking actuator in the embodiment.

FIG. 7 is a block diagram for explaining a second embodiment of the present invention;

FIG. 8 is a flowchart for explaining processing of a microcomputer in the embodiment.

FIG. 9 is a block diagram of a window comparator in the embodiment.

FIG. 10 is a waveform chart for explaining the operation of the window comparator in the embodiment.

FIG. 11 is a block diagram for explaining a tracking control device of a conventional optical disc device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Record carrier 2 Motor 3 Light source 6 Polarization beam splitter 8 Total reflection mirror 10 Convergent lens 11 Photodetector 13 Transfer stand 14 Coil 16 Amplifier 17 Amplifier 18 Differential amplifier 35 Drive circuit 36 Drive circuit 37 Microcomputer 40 Moving part 44 Temperature sensor Reference Signs List 51 sliding shaft 52 rubber 53 base 81 detection lens 82 reflection mirror 89 coil 300 phase compensation filter 301 equivalent filter 302 phase compensation filter 303 photodetector 304 amplifier 305 amplifier 306 differential amplifier 307 phase compensation filter 308 switch 309 switch 310 switch 311 Drive circuit 312 Oscillator 313 Coil 316 Window comparator

────────────────────────────────────────────────── ─── Continuing from the front page (72) Hiroyuki Yamaguchi 1006 Kadoma Kadoma, Kadoma City, Osaka Pref. Matsushita Electric Industrial Co., Ltd. Field (Int.Cl. ⁶ , DB name) G11B 7/09-7/095

Claims (6)

(57) [Claims] 1. A track shift detecting means for detecting a positional shift between a light beam irradiated on a record carrier and a track, a first moving means for moving a light beam on the record carrier across the track, A second moving means for moving the first moving means across the track; and a first moving means for driving the first moving means in response to a signal from the track deviation detecting means, so that the light beam on the record carrier is moved on the track. First control means for controlling the position of the first moving means in response to a signal from the track deviation detecting means, and controlling the position of the first moving means. When,
Determining means for detecting that the level of the signal of the track deviation detecting means has exceeded a predetermined range and outputting a malfunction detection signal; setting the first and second control means to an operating state;
The malfunction detection signal is output from the determination means when
Tracking control device in case, characterized in that heating the first moving means. 2. A track shift detecting means for detecting a positional shift between a light beam irradiated on a record carrier and a track, a first moving means for moving a light beam on the record carrier across the track, A second moving means for moving the first moving means across the track; and a first moving means for driving the first moving means in response to a signal from the track deviation detecting means, so that the light beam on the record carrier is moved on the track. First control means for controlling the position of the first moving means in response to a signal from the track deviation detecting means, and controlling the position of the first moving means. When,
A temperature detecting means for detecting a temperature, wherein the second control
Responding to the output of the temperature detecting means before bringing the means into operation.
Flip and tracking control apparatus characterized by heating said first moving means. 3. A track shift detecting means for detecting a positional shift between a light beam irradiated on a record carrier and a track, a first moving means for moving the light beam on the record carrier across the track, A second moving means for moving the first moving means across the track; and a first moving means for driving the first moving means in response to a signal from the track deviation detecting means, so that the light beam on the record carrier is moved on the track. First control means for controlling the position of the first moving means in response to a signal from the track deviation detecting means, and controlling the position of the first moving means. When,
Range level signal of the tracking error detection means for a predetermined
The judgment method that detects that the threshold value has been exceeded and outputs a malfunction detection signal
And a temperature detecting means for detecting a temperature.
And when the 22nd control means is brought into the operating state,
A malfunction detection signal is output from the stage, and the temperature detection
A tracking control device, wherein when the output of the step is in a predetermined range, the first moving means is heated. 4. The method according to claim 1, wherein the first moving means is heated by operating the first moving means.
4. The tracking control device according to 2 or 3 . 5. A tracking control apparatus according to claim 1, 2 or 3, characterized by heating said first moving means by operating the moving means for the focus control. 6. A method according to claim 1, wherein said first level is determined according to an output level of said temperature detecting means.
4. The tracking control device according to claim 2 , wherein the degree of heating of the moving means is changed.