JP2000331352A - Optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time required for seeking in reproducing a signal recorded in an optical disk. SOLUTION: A procedure for fixing time constant of filters incorporated in a RF(radio frequency) ripple signal generating circuit 8 and a tracking error signal generating circuit 9 after detecting out of lock of a PLL(phase locked loop) 5 by a microcomputer 11, and a procedure for switching time constant of a waveform equalizing circuit 3 after track-on are made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus suitable for servo signal processing of a reproducing apparatus for reading information recorded on an optical disk.

[0002]

2. Description of the Related Art A conventional optical disk reproducing apparatus will be described with reference to FIG. The pickup 1 irradiates a laser beam to the disk 2, detects the reflected light, and outputs a reproduction signal. The waveform equalization circuit 3 performs waveform equalization on the reproduced signal,
An RF (radio frequency) signal output is output to the data slicer 4. In the data slicer 4, the RF signal is sliced by the reference potential to be binarized, and a PLL (phase-locked
loop) Output to 5. The PLL 5 synchronizes the binary data and extracts a bit clock. The synchronization detection circuit 6
A demodulation timing signal is output based on the bit clock. In the decoder 7, 2 based on this timing signal
The demodulated data is demodulated, and the demodulated output is output.

An RF ripple signal generation circuit 8, a tracking error signal generation circuit 9, and a focus error signal generation circuit 10 output a tracking error signal, a focus error signal, and an RF ripple signal, which are positional information of the pickup 1, to a microcomputer 11, respectively. . Microcomputer 11
Outputs a position control signal to the servomechanical unit 12 based on those signals to control the position of the pickup.

The RF ripple signal is obtained by extracting only the envelope change of the RF signal. When the pickup 1 moves in the radial direction of the disk 2 and crosses the track, the signal shown in FIG.
This signal is used for track counting, for example. The tracking error signal is a signal for detecting a displacement of the position of the pickup 1 in the surface direction with respect to the optical disk 2, and there are several methods for obtaining the tracking error signal. For example, in the case of the phase difference detection method, when the pickup moves in the radial direction of the disk and crosses the track, the signal becomes a sawtooth signal as shown in FIG. 6, and becomes 0 when the pickup is on the track. The focus error signal is a signal for detecting a deviation of the position of the pickup 1 in the vertical direction with respect to the optical disk 2.

[0005] Here, the pickup output signal is attenuated as the frequency becomes higher, and the waveform equalizing circuit 3 functions to emphasize the higher frequency component of the pickup output. As shown in FIG. 7, the band of the pickup output signal changes in the frequency axis direction in proportion to the reproduction linear velocity. Therefore, the waveform equalization circuit 3 also needs to control the band in accordance with the change in the signal band of the pickup output, that is, in accordance with the change in the reproduction linear velocity.

The focus error signal generation circuit 1 of the RF ripple signal generation circuit 8, the tracking error signal generation circuit 9, and the focus error signal generation circuit 10
0 is independent of the playback linear velocity of the disc, but other RF
The ripple signal generation circuit 8 and the tracking error signal generation circuit 9 need to change the characteristics of the built-in filter in accordance with the reproduction linear velocity of the disk.

The RF ripple signal generation circuit 8 has, for example, a configuration as shown in FIG. 8, and a high-pass filter 81 removes and outputs a low-frequency component of the pickup output.
Reference numeral 2 denotes peak detection of the output of the high-pass filter 81, and bottom detection circuit 83 bottom-detects the output of the high-pass filter 81. The differential amplifier 84 amplifies and outputs the difference between the output of the peak detection circuit 82 and the output of the bottom detection circuit 83. The low-pass filter 85 removes unnecessary high-frequency components such as noise from the output of the differential amplifier 4 and outputs an RF ripple signal. The time constants of the high-pass filter 81, the peak detection circuit 82, and the bottom detection circuit 83 need to be controlled in accordance with the change in the signal band of the pickup output, that is, in accordance with the change in the reproduction linear velocity.

Further, a tracking error signal generating circuit 9
There are various methods. For example, in the case of the phase difference detection method, two of the four pickup outputs are added by an adder circuit 91a and an adder circuit 91b in a configuration as shown in FIG. The output of 91a is converted to a waveform equalizer 92a
Then, the output of the adder circuit 91b is passed through the waveform equalizing circuit 92b, and the balance adjustment filter 93a and the balance adjustment filter 93b correct the imbalance of the pickup output and the imbalance from the pickup output to the output of the waveform equalization circuit. And the balance adjustment filter 93
The phase difference between the output a and the output of the balance adjustment filter 93b is detected by a phase difference detection circuit 94 to output a tracking error signal. Of these, the time constants of the waveform equalizing circuit and the balance adjustment filter need to be controlled in accordance with the change in the signal band of the pickup output, that is, in accordance with the change in the reproduction linear velocity.

As described above, it is necessary to control the band by adjusting the time constants of the built-in filters of the waveform equalizing circuit 3, the RF ripple signal generating circuit 8, and the tracking error signal generating circuit 9 in accordance with the change in the reproduction linear velocity. If the signal changes following the change of the reproduction linear velocity, it can be used as a signal for controlling the time constant. However, since the frequency of the bit clock extracted by the PLL 5 changes in proportion to the reproduction linear velocity, this bit clock has a waveform. An equalizing circuit 3, a tracking error signal generating circuit 9,
It can be supplied to the RF ripple signal generation circuit 8 and used as a control signal to control the time constant of the waveform equalization circuit 3 and the built-in filter. If the PLL 5 is locked during normal reproduction, the bit clock is proportional to the reproduction linear velocity.

Therefore, the microcomputer outputs a control signal to the switch 13, outputs a bit clock to the waveform equalization circuit 3, the RF ripple signal generation circuit 8, and the tracking error signal generation circuit 9, and can control the time constant of the built-in filter. It has become.

However, this conventional example has a problem. This will be described with reference to the chart of FIG. When the vehicle crosses a track during a seek operation or the like, the lock of the PLL 5 may be released.
In this case, the bit clock frequency cannot maintain a proportional relationship with the reproduction linear velocity, and becomes unstable. As a result, the time constants of the built-in filters of the tracking error signal generation circuit 9 and the RF ripple signal generation circuit 8 significantly deviate from the optimum values and become unstable, so that a normal signal cannot be output.

When trying to turn on the track from this state, the output of the tracking error signal generating circuit 9 outputs an erroneous signal, so that the track cannot be turned on properly. In the worst state, the pickup 1 slides on the disk 2. Move to the outer periphery of the disk.

In order to prevent this, in the conventional servo signal processing system, the microcomputer 11 controls the tracking error signal,
When the unlock state of the PLL 5 is detected due to an abnormality in the RF ripple signal, a control signal is output to the switch 13 and the fixed clock is sent to the waveform equalizing circuit 3, the RF ripple signal generating circuit 8, and the tracking error signal generating circuit 9. Output, and the time constants of the waveform equalizing circuit 3 and the built-in filter are fixed once.

In this state, since the time constant of the waveform equalizing circuit 3 is not optimal, waveform equalization cannot be performed well. Also,
Although the time constants of the built-in filters of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 are also shifted and are not optimal, since the time constants of the built-in filters are stable, signals with small amplitudes are output. If you turn on the track in this state, tracking will work well. After confirming that the tracking has been performed, the microcomputer 11 outputs a control signal to the switch, and supplies a bit clock again to the waveform equalizing circuit 3, the RF ripple signal generating circuit 8, and the tracking error signal generating circuit 9.

In this state, the bit clock is not proportional to the reproduction linear velocity, but is a bit clock proportional to the fixed clock. Thereafter, the PLL is pulled in and the PLL is locked, and the bit clock is proportional to the reproduction linear velocity and data can be read for the first time.

As described above, when the PLL is unlocked and the tracking is lost when crossing a track during a seek operation or the like, there is a problem that it takes time to turn on the track again and read data.

[0017]

As described above, in the conventional servo signal processing method, when the PLL is unlocked when crossing a track during a seek operation or the like, the track is turned on again and data is read. There was a problem that it takes time until.

An object of the present invention is to provide an optical disk reproducing apparatus capable of shortening the time required for seeking.

[0019]

In order to solve the above-mentioned problems, in the optical disk reproducing apparatus of the present invention, the time constant of the waveform equalizing circuit is always set to follow the reproducing linear velocity, and the RF ripple signal generating circuit, the tracking error signal The time constant of the built-in filter of the generation circuit can be switched and set to either linear reproduction speed tracking or fixed, and when a seek command comes to the microcomputer, the RF ripple signal generation circuit and tracking error signal generation circuit Fix the time constant of the built-in filter, then move to seek operation, track on,
Data is read after the PLL is locked by the pull-in operation, and the built-in time constants of the RF ripple signal generation circuit and the tracking error signal generation circuit are returned to the reproduction linear velocity tracking.

By means of the above means, the microcomputer detects that the PLL is unlocked, and then generates an RF ripple signal generation circuit,
The need for seeking is eliminated by eliminating the procedure for fixing the time constant of the built-in filter of the tracking error signal generation circuit and the procedure for switching the time constant of the waveform equalization circuit to track the reproduction linear velocity after turning on the track. Time can be reduced.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram for describing an embodiment of the present invention. The pickup 1 applies a laser beam to the disk 2, detects reflected light, and outputs a reproduction signal. The waveform equalizer 3 equalizes the waveform of the reproduced signal and outputs an RF output to the data slicer 4. The data slicer 4 slices the RF signal at a certain reference potential, binarizes the RF signal, and outputs it to the PLL 5.
The PLL 5 synchronizes the binary data and extracts a bit clock. The synchronization detecting circuit 6 outputs a timing signal for demodulation based on the bit clock. Using this timing signal, the decoder 7 demodulates and outputs the binary data.

The RF ripple signal generation circuit 8, tracking error signal generation circuit 9, and focus error signal generation circuit 10 output a tracking error signal, a focus error signal, and an RF ripple signal, which are positional information of the pickup, to the microcomputer 11. The microcomputer 11 outputs a position control signal to the servo mechanism unit 12 based on these signals, and controls the position of the pickup.

The time constant of the waveform equalizing circuit 3 is
And the fixed clock output from the microcomputer 11 is switched by the switch 13 and output. The time constants of the filters included in the RF ripple signal generating circuit 8 and the tracking error signal generating circuit 9 are controlled by the switch 13. Control.

This embodiment is different from the conventional example in that the time constant of the waveform equalizing circuit is controlled not by the output of the switch 13 but by the bit clock of the PLL 5 so that the time constant of the waveform equalizing circuit is controlled. Is always set to follow the reproduction linear velocity.

The operation when the microcomputer 11 receives a seek command will be described with reference to the flowchart of FIG. When the microcomputer 11 receives the seek command, the microcomputer 11 fixes the time constants of the filters incorporated in the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9, and then starts the seek operation. Even if the lock of the PLL 5 is released during the seek, the time constant of the built-in filter of the tracking error signal generation circuit 9 is fixed, so that the tracking error signal output is stable and the track can be turned on. After that, the PLL 5 performs the pull-in operation and locks the data, reads the data, and returns the built-in time constants of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 to the reproduction linear velocity tracking.

By doing so, the PL, which was conventionally required,
The procedure from when the microcomputer 11 detects the unlock of L5 to when the time constants of the built-in filters of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 are fixed, and the waveform equalization circuit 3 after the track is turned on. Can be omitted, and the time required for seeking can be reduced.

Next, the fixed position of the time constant of the built-in filters of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 will be described.

The method of controlling the rotation of the optical disk is roughly classified into a CLV (constant linear velocity) method and a CAV (constant rotation speed) method.
There is a method. The CLV method is a control method for keeping the linear velocity constant. The linear velocity of the track to be reproduced is the same everywhere on the disk, and the reproduction linear velocity is always constant. On the other hand, the CAV method is a control method for keeping the angular velocity constant, and the reproduction linear velocity increases from the inner circumference to the outer circumference as shown in FIG. For example, a DVD (digital video disc) disc has a difference in reproduction linear velocity of about 2.
4 times.

The control method of DVD disk rotation is CAV
Let us consider the case of the method. When the time constant of the built-in filter of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 is fixed during the seek, if the time constant of the filter is fixed to the time constant at the time of the innermost reproduction of the disc, the time of the outermost reproduction The deviation of the time constant of the filter from the optimum value increases. Further, if the time constant of the filter is fixed to the time constant at the time of reproduction of the outermost periphery of the disc, the deviation of the time constant of the filter from the optimum value at the time of reproduction of the innermost periphery becomes large. Therefore, when the fixed value of the time constant of the filter is set to the average value of the time constant of the filter at the time of reproducing the innermost circumference of the disc and the time constant of the filter at the time of reproducing the outermost circumference of the disc, the optimum value of the time constant can be obtained at any place. , And the RF ripple signal and the tracking error signal can be output more accurately.

When the fixed position of the time constant of the built-in filter of the RF ripple signal generation circuit 8 and the tracking error signal generation circuit 9 can be set arbitrarily, when seeking from the inner circumference to the outer circumference, the filter before the seek is used. When the frequency is fixed to be higher than the time constant, the RF ripple signal and the tracking error signal can be output with higher accuracy.

Conversely, when seeking from the outer circumference to the inner circumference,
If the frequency is fixed to be lower than the time constant of the filter before the seek, the RF ripple signal and the tracking error signal can be output with higher accuracy.

FIG. 4 is a circuit configuration diagram for explaining another embodiment of the present invention. In this embodiment, PL
The L5 bit clock is converted into a voltage by the frequency-voltage conversion circuit 14, and a control voltage is supplied from the microcomputer 11, and the time constant of the waveform equalization circuit 3, the RF ripple signal generation circuit 8, the tracking error signal generation circuit 9 in that the time constant of the built-in filter 9 is controlled by voltage.

In such an embodiment, a control clock generation circuit, a crystal oscillator and the like are not required. In addition, since control is performed by voltage, it is easy to fix the time constant at an arbitrary position.

[0034]

As described above, according to the optical disk reproducing apparatus of the present invention, the time required for seeking can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram illustrating an embodiment of the present invention.

FIG. 2 is a flowchart for explaining an operation during a seek.

FIG. 3 is an explanatory diagram for explaining a relationship between a reproduction position and a reproduction linear velocity.

FIG. 4 is a configuration diagram for explaining another embodiment of the present invention.

FIG. 5 is a configuration diagram for explaining a conventional optical disc reproducing apparatus.

FIG. 6 is an explanatory diagram for explaining a tracking error signal and an RF ripple signal.

FIG. 7 is a configuration diagram for describing a configuration of a tracking error signal generation circuit.

FIG. 8 is a configuration diagram for describing a configuration of a ripple signal generation circuit.

FIG. 9 is an explanatory diagram for explaining a relationship between a signal band of a pickup output and a reproduction linear velocity.

FIG. 10 is a flowchart for explaining a conventional seek operation.

[Explanation of symbols]

1 ... pickup, 2 ... disk, 3 ... waveform equalization circuit,
4 data slicer, 5 PLL, 6 synchronization detection circuit,
7 Decoder, 8 RF ripple signal generation circuit, 9 Tracking error signal generation circuit, 10 Focus error signal generation circuit, 11 Microcomputer, 12 Servo mechanism, 13 Switch, 14 Frequency voltage conversion circuit.

Claims (9)

[Claims] When a seek command is received, a laser beam is radiated from a pickup onto an optical disk, the reflected light is detected, and a time constant of a waveform equalization circuit for waveform equalizing a reproduced signal taken out is determined by a reproduction linear velocity. While following, the time constant of the filter incorporated in the servo signal processing circuit that controls the position of the pickup based on the position information of the pickup is fixed, and then the operation proceeds to the seek operation to configure the servo signal processing circuit. An optical disc reproducing apparatus characterized in that when the PLL is unlocked, the track is turned on as it is, the PLL is pulled in, and the time constant of the built-in filter of the servo signal processing circuit is returned to the reproduction linear velocity tracking. 2. A waveform equalizing circuit having a first time constant control terminal, wherein a laser beam is applied to an optical disc from a pickup, the reflected light is detected and taken out as a reproduction signal, and the reproduction signal is equalized in waveform. A tracking error signal generation circuit having a second time constant control terminal for generating a tracking error signal from the output of the pickup and controlling the time constant of the built-in filter; detecting and outputting a ripple signal from the output of the pickup; An RF ripple signal generation circuit having a third time constant control terminal for controlling a time constant of the built-in filter, wherein the first time constant control terminal has a first clock whose frequency is proportional to the reproduction linear velocity. To control the time constant of the waveform equalization circuit so as to follow the reproduction linear velocity. The second and third time constant control terminals are connected to the first clock. And a second clock having a constant frequency, and the time constants of the built-in filters of the tracking error signal generation circuit and the RF ripple signal generation circuit follow the reproduction linear velocity or do not follow. An optical disc reproducing apparatus characterized in that the user can select either one of fixed and fixed. 3. The frequency of the second clock is an intermediate frequency between the frequency of the first clock during the innermost reproduction and the frequency of the first clock during the outermost reproduction. 3. The optical disk reproducing device according to 2. 4. The optical disk according to claim 2, wherein the frequency of the second clock when seeking from the inner circumference to the outer circumference is higher than the frequency of the first clock before the seek. Playback device. 5. The optical disk according to claim 2, wherein the frequency of the second clock when seeking from the outer circumference to the inner circumference is lower than the frequency of the first clock before seeking. Playback device. 6. A waveform equalizing circuit provided with a first time constant control terminal, wherein a laser beam is applied from an optical disk to a pickup, a reflected light is detected and taken out as a reproduced signal, and the reproduced signal is equalized in waveform. A tracking error signal generating circuit having a second time constant control terminal for generating a tracking error signal from an output of the pickup and controlling a time constant of the built-in filter; An RF ripple signal generation circuit having a third time constant control terminal for controlling a time constant; and a frequency-voltage conversion circuit for converting a clock frequency into a voltage, wherein the first time constant control terminal has a reproduction line. A signal obtained by converting the first clock whose frequency is proportional to the speed into a voltage by the frequency-voltage conversion circuit is input, and the signal is followed by the reproduction linear speed. Controlling the time constant of the waveform equalization circuit; selecting and inputting either the output of the frequency-voltage conversion circuit or the fixed voltage to the second and third time constant control terminals; An optical disc reproducing apparatus characterized in that the time constant of an error signal generating circuit and a built-in filter of the RF ripple signal generating circuit can be selected to follow the reproducing linear velocity or to be fixed without following. 7. The fixed voltage of the voltage source includes a voltage value obtained by converting a frequency of a first clock at the time of innermost reproduction and a first voltage at the time of outermost reproduction.
7. An intermediate voltage of a voltage value obtained by converting the frequency of the clock of the clock signal by the frequency-voltage conversion circuit.
An optical disc playback device according to claim 1. 8. The fixed voltage of the voltage source when seeking from the inner circumference to the outer circumference is a voltage value higher than a voltage value obtained by converting the frequency of the first clock before the seek by the frequency-voltage conversion circuit. 7. The optical disk reproducing apparatus according to claim 6, wherein: 9. The fixed voltage of the voltage source when seeking from the outer circumference to the inner circumference is a voltage value lower than a voltage value obtained by converting the frequency of the first clock before the seek by the frequency-voltage conversion circuit. 7. The optical disk reproducing apparatus according to claim 6, wherein: