JP2002208141A - Filter circuit with phase adjusting function, phase demodulating circuit and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter circuit with the phase adjusting function capable of exactly specifying the position on media by adjusting not only the frequency characteristic but also the phase characteristic in accordance with an input signal frequency. SOLUTION: In the state that the filter circuit 16 having the frequency and phase characteristics being variable with a signal from the outside is set to the desirable frequency characteristic by a 1st control signal from a frequency control circuit 17, the device is arranged so that the phase with the high sensitivity for the change with respect to the frequency is also correctable in accordance with the frequency of an input signal by adjusting the phase characteristic by a 2nd control signal from a phase adjustment circuit 20 so as to keep the phase difference constant between the input signal and the output signal of the filter circuit 16 detected by a phase detecting circuit 19. Thus, the phase generated by the filter circuit 16 or the peripheral circuits is removed, and the phase difference between the input signal and the output signal is kept to be constant independently of the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter circuit having a function of automatically adjusting a phase change of a filter circuit accompanying a frequency change, a phase demodulation circuit, such a filter circuit and a phase demodulation. The present invention relates to an optical disk device provided with a circuit.

[0002]

2. Description of the Related Art Generally, in a recording medium, in order to accurately detect a linear velocity at each radial position, a track engraved on a medium when a constant linear velocity (CLV) type rotation control is performed. A format is adopted in which the frequency of a wobble signal that can be detected from undulations (wobbles) is constant. Of course, the information to be recorded has a constant linear velocity. Also, address information is required so that a rough position in an unrecorded area can be specified. One example of this is to apply phase modulation to wobbles as disclosed in Japanese Patent Application Laid-Open No. 10-69646. A way is being considered.

On the other hand, in order to improve the reproduction speed of such media, a linear velocity is increased to twice or three times, or a constant angular velocity (CAV) method for making the rotation speed constant is generally used. Is coming. In the CAV method, the frequency of information and wobbles recorded increases as the outer periphery of the medium is accessed. These high-speed flows also exist during recording.

During recording, the rotational speed and linear velocity of the medium are detected based on the frequency of the wobble signal. Naturally, since the frequency of the wobble signal changes according to the recording speed, it is necessary to change the characteristics of the detection circuit accordingly. In particular, in the case of the CAV system, the frequency of the wobble signal changes continuously.

In view of such a situation, for example, Japanese Patent Laid-Open No.
According to Japanese Patent Publication No. 1-203681, a method of controlling a cutoff frequency (center frequency) of a BPF (bandpass filter) for detecting a wobble signal is proposed. That is, the frequency of a signal passing through the BPF is converted into a voltage using a dummy circuit whose phase changes according to the input signal frequency, and the voltage controls the center frequency of the BPF.

[0006]

Since the amplification factor of the BPF changes as it deviates from the center frequency, it is necessary to always use the detection signal frequency as the center frequency. But BP
Another great specialty of F is that the phase changes significantly around the center frequency. The amplification rate changes gradually near the center frequency, but the phase change rate is the highest.

Therefore, in the case of the conventional example shown in Japanese Patent Application Laid-Open No. H11-203681, when the frequency characteristics of a BPF are determined by voltage control by a dummy circuit, the frequency-phase characteristics of the dummy circuit, the BPF frequency characteristics, etc. The error in the frequency tracking ability increases due to individual variations. Even if care is taken to satisfy the same characteristics, due to differences in circuit configuration, wiring layout during integration, etc.,
Variations occur. Of course, it is possible to perform control such that the amplification factor does not deviate from the center frequency and the BPF output is not interrupted, but it is impossible to expect the accuracy of controlling the phase of the BPF having a large change rate near the center frequency.

[0008] The following problem arises when the phase around (change) of the BPF changes depending on the frequency. It can be said that the wobble signal obtained from the medium indicates an accurate position on the medium. In the case of appending or rewriting information on recording media, information is overwritten to rewrite information.Because the position on the media is specified with high accuracy so that the previously recorded data is not destroyed, recording is started. It is necessary to detect a signal having the same phase as a BPF output regardless of the frequency of the wobble signal. Since the format of the CD media is such that the data at the connection portion can be destroyed, rough addition and overwriting are performed based on the address information. However, it goes without saying that data loss is large. On the other hand, in the case of DVD media, it is necessary to minimize data loss, and the accuracy cannot be obtained only with address information. For this reason, a method is used in which a clock is generated based on the wobble signal to determine the position more accurately. However, when the phase around the BPF occurs, the clock also shifts, and there is a variation in specifying the position on the medium. Occurs. In the case of the CAV method or the like, the frequency changes seamlessly. Therefore, if the phase rotation characteristic of the filter circuit has frequency dependence, correction using a fixed value cannot be used.

In the case of the above-described conventional example, a specific position on the medium is displaced by an amount corresponding to the phase generated due to the determination of the frequency characteristic of the BPF using the dummy circuit. Even if the phase around is fixed regardless of the frequency in one circuit, it is not always the same as the circuit of another device.

Although the wobble contains address information, the position on the medium which can be detected by the address information cannot be solved because the time scale is completely different from the problem around the phase and the time scale is large.

In view of the above, the present invention provides a filter circuit with a phase adjustment function that can accurately specify a position on a medium by adjusting not only the frequency characteristic but also the phase characteristic according to the input signal frequency. It is an object of the present invention to provide an optical disc device provided with a phase demodulation circuit including a circuit.

Further, according to the present invention, the phase adjustment of the filter is
By using a configuration similar to the phase demodulation circuit configuration for address detection, additional scale down due to sharing of circuits,
It is an object of the present invention to provide a phase demodulation circuit that can achieve a cost merit and can obtain a good demodulation performance by stabilizing a filter characteristic, and an optical disc device including the phase demodulation circuit.

[0013]

According to a first aspect of the present invention, there is provided a filter circuit having a phase adjustment function, wherein a frequency characteristic and a phase characteristic are variable by an external signal, and the filter circuit mainly has a frequency characteristic. A frequency control circuit for generating a first control signal to be determined, a phase control circuit for generating a second control signal mainly for determining a phase characteristic of the filter circuit, and an input signal and an output signal of the filter circuit. A phase detection circuit for detecting a phase difference, wherein the output of the phase detection circuit is kept constant while the filter circuit is set to a desired frequency characteristic by the first control signal from the frequency control circuit. As described above, the phase characteristics of the filter circuit are adjusted by the second control signal from the phase control circuit.

Therefore, in a state where the filter circuit is set to a desired frequency characteristic by the first control signal, the phase characteristic is controlled by the second control signal so as to keep the phase difference between the input signal and the output signal of the filter circuit constant. , The phase around the phase with high change sensitivity to frequency can be corrected according to the input signal frequency, the phase around the filter circuit and its peripheral circuits is removed, and the phase difference between the input signal and the output signal is removed. Can be kept constant regardless of the frequency.

According to a second aspect of the present invention, in the filter circuit with the phase adjusting function according to the first aspect, the filter circuit includes a band-pass filter, and an input signal and an output signal of the filter circuit are controlled by the second control signal. Was adjusted so as to eliminate the phase difference.

Accordingly, a band pass filter (BPF) in which the filter circuit has both a phase lead characteristic and a phase delay characteristic
And the second control signal adjusts the phase difference between the input signal and the output signal of the filter circuit so that the phase difference between the input signal and the output signal is adjusted to 0 instead of a specific value. And the circuit can be simplified. Further, since the BPF has a characteristic that the amplification factor becomes maximum and flat at a frequency around 0 around the phase, the phenomenon that the amplification factor of the filter circuit greatly changes due to the phase adjustment is also eliminated.

According to a third aspect of the present invention, in the filter circuit with the phase adjusting function according to the first or second aspect, a pseudo signal generator for selectively outputting a pseudo signal of a desired frequency to the filter circuit; A storage circuit for storing the level of the second control signal for keeping the output of the phase detection circuit constant, and sequentially changing the frequency of the pseudo signal by the pseudo signal generator to the filter circuit. In addition to the output, the level of the second control signal at each frequency is stored in the storage circuit.

Therefore, a pseudo signal of a desired frequency is output by the pseudo signal generator, the frequency is sequentially changed and input to the filter circuit, and the output of the phase detection circuit is kept constant at each frequency. Since the level of the control signal is stored, the frequency characteristics around the phase of the filter circuit can be detected by the variable frequency pseudo signal even when there is no input signal. In addition, even when the input signal is modulated and the frequency or waveform changes, by using a pseudo signal having a stable frequency and waveform,
Around the phase can be accurately detected.

According to a fourth aspect of the present invention, in the filter circuit with the phase adjusting function according to the first, second or third aspect, the pseudo signal generator determines a frequency of the pseudo signal to be output by the first control signal. The frequency of the pseudo signal and the cutoff frequency of the filter circuit are set to be equal.

Therefore, the pseudo signal generator can determine the frequency of the pseudo signal by the first control signal. By setting the frequency of the pseudo signal and the cutoff frequency of the filter circuit to be equal, the pseudo signal generator can set the frequency of the filter circuit. Set the cutoff frequency not from the frequency detection result of the input signal,
In the case where the pseudo signal frequency setting and the filter circuit cutoff frequency setting are different from each other, it is possible to prevent occurrence of a phase rotation detection error, for example, in the case where the pseudo signal frequency setting is determined based on a calculated value obtained from a radius position or the like.

According to a fifth aspect of the present invention, there is provided a filter circuit having a cutoff frequency characteristic and a phase characteristic variable by an external signal, and a wobble signal based on an output of the filter circuit of a wobble signal obtained from a medium. A carrier generation circuit that generates a sine wave signal corresponding to a carrier wave of the superimposed phase modulation information, a multiplier that multiplies the sine wave signal by the wobble signal, and phase modulation information from the multiplication result of the multiplier. A phase demodulation circuit for demodulating, the multiplier input switching means for selectively switching one input to the multiplier from a sine wave signal by the carrier generation circuit to an output signal of the filter circuit; By switching the input from the sine wave signal to the output signal of the filter circuit, the wobble signal of the multiplier and the filter Phase adjustment control means for detecting the phase difference between the wobble signal and the output signal of the filter circuit from the result of multiplication with the output signal of the filter circuit, and adjusting the phase of the filter circuit so that the phase difference disappears. .

Therefore, when a filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal is mounted on the phase demodulation circuit, a multiplier originally provided in the phase demodulation circuit is used as the phase detection circuit. By sharing, the same operation as in the case of claim 1 or 2 can be obtained, and an increase in circuit scale and cost due to the addition of the phase adjustment function of the filter circuit can be avoided.

According to a sixth aspect of the present invention, there is provided a filter circuit having a cutoff frequency characteristic and a phase characteristic variable by an external signal, and a wobble signal based on an output of the filter circuit of a wobble signal obtained from a medium. A carrier generation circuit capable of generating a sine wave signal corresponding to a carrier wave of the superimposed phase modulation information and generating a sine wave signal of a specific frequency by an external signal; and multiplying the wobble signal by the sine wave signal. A phase demodulation circuit for demodulating phase modulation information from the multiplication result of the multiplier, wherein an input to the filter circuit and one input to the multiplier are provided by the carrier generation circuit from the wobble signal. Filter input switching means for selectively switching to a sine wave signal, and the other input to the multiplier for generating the carrier wave A multiplier input switching means for selectively switching a sine wave signal by a path to an output signal of the filter circuit; and a sine wave signal of a specific frequency output from the carrier wave generation circuit, and an input to the filter circuit from the wobble signal. By switching to the sine wave signal of the specific frequency by the carrier generation circuit, and by switching the input to the multiplier to a sine wave signal of the specific frequency by the carrier generation circuit and an output signal of the filter circuit, The phase difference between the sine wave signal of the specific frequency and the output signal of the filter circuit is detected from the result of multiplication of the sine wave signal of the specific frequency by the multiplier and the output signal of the filter circuit, and the phase difference is detected. Phase adjustment control means for adjusting the phase of the filter circuit so as to eliminate the problem.

Therefore, when a filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal is mounted on the phase demodulation circuit, a multiplier originally provided in the phase demodulation circuit is used as the phase detection circuit. A third aspect of the present invention is to share the carrier generation circuit originally provided in the phase demodulation circuit as a pseudo signal generator.
The same operation as in the case (1) can be obtained, and an increase in circuit scale and cost due to the phase adjustment function of the filter circuit and the addition of the pseudo signal generator can be avoided.

According to a seventh aspect of the present invention, in the phase demodulation circuit according to the fifth or sixth aspect, the phase adjustment control means includes:
A peak detection circuit for detecting a peak value of the output signal of the multiplier is provided, and the phase of the filter circuit is adjusted so that the output of the peak detection circuit is maximized.

Therefore, since the phase of the filter circuit is adjusted so that the peak value of the output signal of the multiplier becomes maximum, the phase difference becomes exactly 0 with a simple circuit configuration from the result of the multiplication of the multiplier. An adjustment value can be determined.

[0027] The optical disk device of the invention according to claim 8 is
A phase demodulation circuit comprising the filter circuit with a phase adjusting function according to any one of claims 1 to 4, and demodulating phase modulation information based on a wobble signal obtained from a medium, or a phase demodulation circuit according to any one of claims 5 to 7. A phase demodulation circuit is provided.

Therefore, a phase demodulation circuit including the filter circuit with a phase adjusting function according to any one of claims 1 to 4 and demodulating phase modulation information based on a wobble signal obtained from a medium, or any one of claims 5 to 7 By providing the phase demodulation circuit described in any one of the above, the same operation as the invention described in each claim can be obtained.

According to a ninth aspect of the present invention, in the optical disk device of the eighth aspect, a storage means for storing a phase adjustment value is provided, and prior to recording information on the medium, the filter circuit of the filter circuit at a necessary wobble frequency is required. A phase adjustment value is stored in the storage unit, and the phase adjustment of the filter circuit is performed using the phase adjustment value stored in the storage unit according to a wobble frequency detected during actual recording on the medium. I did it.

Therefore, prior to recording information on the medium, the phase adjustment value of the filter circuit at the required wobble signal frequency is stored in the storage means, and is stored in accordance with the detected wobble signal frequency during actual recording. Since the phase adjustment of the filter circuit is performed using the phase adjustment value, the phase of the wobble signal and the output signal of the filter circuit are constant regardless of the wobble signal frequency, and the current access on the medium indicated by the wobble is performed. The position can be accurately determined from the output signal of the filter circuit.

[0031]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. First, an outline of an optical disc apparatus including a phase demodulation circuit including a characteristic filter circuit with a phase adjustment function of the present invention will be described with reference to FIG. This optical disk device is a DVD-R or DVD
An optical pickup 3 for irradiating a spot of a laser beam to the medium 1 driven and rotated by a spindle motor 2 and detecting a reflected light thereof; Is provided.
A reproduction circuit 4 for performing arithmetic processing on a signal detected by the optical pickup 3 as a reproduction signal, and a decoder 5 for converting a format of a user data component in the signal generated by the reproduction circuit 4 are provided. It is configured to be sent to an external host (not shown) via a CPU 6 having a microcomputer configuration having a memory as a memory. The information to be recorded is sent from an external host to the encoder 7 via the CPU 6, the format is converted by the encoder 7, and the laser control circuit 8 controls the light emission of the laser according to the information bit to thereby control the optical pickup 3. Is recorded on the medium 1 through the semiconductor laser.

On the other hand, rotation information, address information, and the like are sent from the reproduction circuit 4 to the phase demodulation circuit 9, and a wobble signal and phase modulation information are detected. The wobble signal is sent to the servo circuit 10 and the clock generation circuit 11, and the servo circuit 10
Then, the rotation of the spindle motor 2 is controlled, and the clock generation circuit 11 generates an accurate clock following the rotation of the medium and sends it to the encoder 7. The phase modulation information is sent to the address decoder 12, and reproduces the address information of the access position.

Here, the phase demodulation circuit 9 is roughly
The carrier wave of the phase modulation information superimposed on the wobble signal based on the output of the filter circuit 13 with the phase adjustment function of the characteristic wobble signal obtained from the medium 1 and the characteristic filter circuit 13 with the phase adjustment function according to the present embodiment. A carrier generation circuit that generates a sine wave signal; and a multiplier that multiplies the wobble signal and the sine wave signal, and a configuration that demodulates phase modulation information for the address decoder from a multiplication result of the multiplier. Have been.

As a method of generating a wobble signal used in the present embodiment, the simplest example is the optical pickup 3.
In this case, the signal is detected from the push-pull signal (one of the track error signals) obtained from the difference between the right and left light receiving element dividing lines along the track. In FIG. It is described as it is.

Next, the filter circuit 13 with a phase adjusting function
Will be described with reference to FIG. First, there is provided a filter circuit 16 whose cut-off frequency characteristic can be varied by a control signal (either a voltage signal or a clock signal) supplied from the outside. The configuration of the filter is low-pass filter (LPF) or high-pass filter (HP
F) may be used, but a circuit having both a phase lead component and a phase lag component in combination, such as a band-pass filter (BPF), is easy to use. LPF and HP
Since F is for delaying or advancing the phase, a specific phase rotation amount other than 0 is adjusted as a target. In addition, in the frequency range where the phase changes, the amplification factor also changes greatly, so care must be taken when using it. That point, B
The PF has both delay and advance characteristics centered around 0 around the phase, and the amplification factor is maximum and flat at a frequency at which the phase greatly changes. FIG. 3 shows the frequency characteristics (amplification rate, phase) of the BPF. It can be seen that the amplification rate becomes maximum and flat near the cutoff frequency (center frequency), and that the phase has the largest change rate around zero.

The filter circuit 16 is a frequency control circuit 1
The cut-off frequency is determined by the first control signal input from. Although FIG. 2 shows that the first control signal is output from the CPU 18, the first control signal is generated by detecting the frequency of the input signal of the filter circuit 16 as in the conventional example. May be configured. On the other hand, a phase comparison circuit 19 as a phase detection circuit for detecting a phase difference between an input signal and an output signal of the filter circuit 16 is provided. Then, the phase control circuit 20 adjusts the phase characteristic of the filter circuit 16 using the second control signal so that the phase difference detected by the phase comparison circuit 19 becomes a specific value (0 in the case of BPF).

The adjustment of the phase characteristic is performed by the frequency control circuit 1
7, the first control signal by the phase control circuit 20 is set as a rough cut-off frequency, the second control signal by the phase control circuit 20 is set to a precise cut-off frequency, and the first control signal by the frequency control circuit 17 is A method in which the cutoff frequency is mainly set and the second control signal by the phase control circuit 20 is mainly set separately only around the phase may be used. In the present embodiment, for example, the frequency control circuit 17
With the filter circuit 16 set to a desired frequency characteristic by the first control signal from the phase control circuit 20, the second control signal from the phase control circuit 20 controls the filter circuit 16 to maintain the output of the phase comparison circuit 19 constant. Adjust the phase characteristics.

According to such a circuit configuration, since the input signal and the phase of the filter circuit 16 can be detected in real time, the phase can be sequentially adjusted even when the frequency changes seamlessly such as in the CAV method.

Incidentally, the filter circuit 13 with a phase adjusting function of the present embodiment includes a pseudo signal generator 21 for outputting a signal (pseudo signal) of a desired frequency.
The switching of the switching means 22 such as an analog switch provided on the input side of the filter circuit 16 allows the pseudo signal generated by the pseudo signal generator 21 to be input to the filter circuit 16. Further, a storage circuit 23 for storing the level of the second control signal output from the phase control circuit 20 to the filter circuit 16 is added.

Therefore, when the pseudo signal generator 21 is used, the input signal to the filter circuit 16 is converted to the pseudo signal generator 2.
1 and the phase of the pseudo signal of the desired frequency generated by the pseudo signal generator 21 and the phase of the output signal of the filter circuit 16 are compared by the phase comparison circuit 19.

The frequency of the pseudo signal generator 21 is set by a CPU.
18 and so on. Therefore, the frequency of the pseudo signal generated and output by the pseudo signal generator 21 is sequentially changed and input to the filter circuit 16, and for each frequency,
The level of the second control signal obtained by the phase control circuit 20 is stored in the storage circuit 23 together with the frequency.

According to this, even if there is no input signal, the frequency characteristic around the phase of the filter circuit 16 can be detected by the variable frequency pseudo signal. Also, when the input signal is modulated and the frequency or waveform changes,
By using a pseudo signal having a stable frequency and waveform, it is possible to accurately detect around the phase.

When the frequency control circuit 17 detects the frequency of the input signal and outputs the first control signal, the phase difference due to the cutoff frequency shift of the filter circuit 16 due to the frequency detection error is also corrected by such phase adjustment. Can be removed. The first control signal of the frequency control circuit 17 is C
In the case where the setting is made from the PU 18 or the like, it is desirable that the setting is performed using a signal common to the frequency setting to the pseudo signal generator 21. That is, the pseudo signal generator 21 can determine the frequency of the pseudo signal with the first control signal. By setting the frequency of the pseudo signal and the cutoff frequency of the filter circuit 16 to be equal, the pseudo signal generator 21 When the cutoff frequency setting is determined not by the frequency detection result of the input signal but by the calculated value obtained from the radius position, etc., the phase around the phase due to the difference between the pseudo signal frequency setting and the filter circuit cutoff frequency setting It is possible to prevent the occurrence of a detection error.

FIGS. 4 and 5 show a second embodiment of the present invention.
It will be described based on. Portions or corresponding portions described in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

First, the configuration of the optical disk device is shown in FIG.
In the present embodiment, the filter circuit 1 basically replaces the phase demodulation circuit 9 in FIG.
6, a phase demodulation circuit 31 including the carrier generation circuit 14 and the multiplier 15.

FIG. 4 is a block diagram showing a configuration example of such a phase demodulation circuit 31. An outline of the phase demodulation circuit 31 will be described. In order to extract a phase modulation component from a wobble signal, a carrier which is not modulated at the same frequency and phase as the wobble signal is generated, and the phase of the carrier and the phase of the wobble signal are changed. It is common to make a comparison. Therefore, noise and phase modulation components are removed from the wobble signal by the filter circuit 16, and a stable sine wave signal (sine wave signal) is generated by the carrier generation circuit 14 based on the signal. This SI
The N-wave signal has the same frequency as the wobble signal, and basically the phase does not change stably. The amplitude is desirably the same value as the fundamental wave (SIN wave component excluding noise) of the wobble signal. The wobble signal is output from the carrier generation circuit 14 by the multiplier 15.
Performs multiplication operation with SIN wave. Although not shown, the multiplied output of the multiplier 15 is processed by an integrator, a sample-and-hold circuit, and the like to demodulate the phase modulation information.

Here, in order to adjust the phase of the filter circuit 16, it is necessary to detect the phases of the input signal and the output signal. In the present embodiment, the phase demodulation circuit 31 is used instead of the phase comparison circuit 19 described above. In this case, a multiplier 15 originally included in the apparatus is used. For this reason, in the present embodiment, the multiplier input switching means 32 such as an analog switch for selectively switching one input to the multiplier 15 from the SIN wave signal by the carrier generation circuit 14 to the output signal of the filter circuit 16 is provided. CPU 18
Switching is controlled by the phase adjustment control means 33 constituted by the above.

When the multiplier 15 is used as a substitute for the phase comparison circuit 19, SIN which is one of the input signals of the multiplier 15 is used.
The wave signal is switched to the output signal of the filter circuit 16. The wobble signal and the output signal of the filter circuit 16 are multiplied by a multiplier 15.
, A sine wave whose frequency is doubled is obtained as shown in FIG. The solid line shows the case without phase shift, and the dotted line shows the case with phase shift.

The output of the multiplier 15 has the largest maximum amplitude and average value when the two input signal phases match. If the two input signals are out of phase, the amplitude is reduced and the average level is also reduced. Therefore, the point where the phase difference between the two signals is 0 can be obtained by detecting the point having the maximum amplitude, the maximum average value, or the maximum peak value. Among them, the peak value having the highest detection sensitivity is the peak value. The peak value of the output of the multiplier 15 is detected by the peak detection circuit 34, and the maximum value of the filter circuit 16 (by the second control signal) is obtained. The phase is set via the CPU 18.

In order to adjust the phase of the filter circuit 16 in the absence of an input signal (wobble signal), the carrier generation circuit 14 can be used as a substitute for the pseudo signal generator 21. For this reason, the filter input switching means 3 such as an analog switch for selectively switching the input to the filter circuit 16 and one input to the multiplier 15 from the wobble signal to the sine wave signal by the carrier generation circuit 14.
5 is controlled by the phase adjustment control means 33 for switching.

Therefore, when the phase adjustment of the filter circuit 16 is performed without the wobble signal, the filter circuit 16
Is switched from the wobble signal, which is the input signal of the multiplier 15 and the input signal of the multiplier 15, to the SIN wave signal of the specific frequency output from the carrier generation circuit 14. The phase comparison method between the sine wave signal of the specific frequency and the output signal of the filter circuit 16 conforms to the case described above. If the output signal frequency of the carrier generation circuit 14 is set equal to the first control signal of the filter circuit 16, the configuration is simple and good.

When the phase demodulation circuit 9 and the phase demodulation circuit 31 including such a filter circuit 13 with a phase adjusting function are mounted on an actual optical disk apparatus, a wobble signal is input and the output is output by another block. When the phase of the filter circuit is adjusted in real time in a used state, a pseudo signal is generated before actual recording, etc., and the phase is adjusted in advance according to the frequency. For example, it may be assumed that the phase adjustment value stored in the memory as a storage unit in the above-described method is used during the actual recording.

In the former case where the phase is adjusted in real time,
There is no need for a phase adjustment waiting time before recording or a pseudo signal generator, but since the phase demodulation circuit 9 or 31 is used in actual operation, a relatively large-scale phase comparison circuit is required and an input signal If there is modulation in the phase comparison, errors tend to occur in the phase comparison result. In this regard, the latter can perform stable phase adjustment only by adding a small improvement to the system equipped with the phase demodulation circuit 9 or 31 and adding the small-scale peak detection circuit 34.

[0054]

According to the filter circuit with the phase adjusting function of the present invention, the input signal and the output signal of the filter circuit are set in a state where the filter circuit is set to a desired frequency characteristic by the first control signal. The phase characteristic is adjusted by the second control signal so as to keep the phase difference constant, so that even a phase having a high change sensitivity to frequency can be corrected according to the input signal frequency, and the filter circuit and its peripheral circuits can be corrected. And the phase difference between the input signal and the output signal can be kept constant irrespective of the frequency.

According to the second aspect of the present invention, in the filter circuit with the phase adjusting function according to the first aspect, the filter circuit includes a band-pass filter (BPF) having both a phase lead characteristic and a phase delay characteristic. The control signal is adjusted so as to eliminate the phase difference between the input signal and the output signal of the filter circuit, so that the phase difference between the input signal and the output signal can be adjusted to 0 instead of a specific value. Can be simplified. Further, since the BPF has a characteristic that the amplification factor becomes maximum and flat at a frequency around 0 around the phase, the phenomenon that the amplification factor of the filter circuit greatly changes due to the phase adjustment is also eliminated.

According to the third aspect of the present invention, in the filter circuit with the phase adjusting function according to the first or second aspect, a pseudo signal of a desired frequency is output by the pseudo signal generator,
Since the frequency is sequentially changed and input to the filter circuit, and the level of the second control signal that keeps the output of the phase detection circuit constant at each frequency is stored, the frequency can be changed even when there is no input signal. The frequency characteristic around the phase of the filter circuit can be detected by the pseudo signal of the above, and even when the input signal is modulated and the frequency or the waveform changes, by using the pseudo signal of the stable frequency and waveform. , Around the phase can be accurately detected.

According to the invention set forth in claim 4, according to claim 1,
4. The filter circuit with a phase adjustment function according to 2 or 3,
The pseudo signal generator can determine the frequency of the pseudo signal by the first control signal. The frequency of the pseudo signal is set to be equal to the cutoff frequency of the filter circuit. Is not determined by the frequency detection result of the input signal, but by the calculated value obtained from the radius position, etc., the phase detection error due to the deviation between the pseudo signal frequency setting and the filter circuit cutoff frequency setting. Occurrence can be prevented.

According to the phase demodulation circuit of the present invention, when a filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal is mounted on the phase demodulation circuit, the phase demodulation circuit inherently has Since the multiplier provided in (1) is commonly used as the phase detection circuit, the same operation as in the case of claim 1 or 2 can be obtained, and the increase in circuit scale and cost due to the addition of the phase adjustment function of the filter circuit. Up can be avoided.

According to the phase demodulation circuit of the present invention, when a filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal is mounted on the phase demodulation circuit, the phase demodulation circuit is inherently used in the phase demodulation circuit. Is shared as a phase detection circuit, and the carrier generation circuit originally provided in the phase demodulation circuit is shared as a pseudo signal generator. A similar effect can be obtained, and an increase in circuit scale and an increase in cost due to the phase adjustment function of the filter circuit and the addition of the pseudo signal generator can be avoided.

According to the seventh aspect of the present invention, in the phase demodulation circuit according to the fifth or sixth aspect, the phase of the filter circuit is adjusted so that the peak value of the output signal of the multiplier becomes maximum. The adjustment value at which the phase difference becomes 0 can be accurately obtained from the result of the multiplication by the multiplier with a simple circuit configuration.

According to the optical disk apparatus of the present invention, the phase modulation information is demodulated based on the wobble signal obtained from the medium, including the filter circuit having the phase adjusting function according to any one of the first to fourth aspects. Since the phase demodulation circuit or the phase demodulation circuit according to any one of claims 5 to 7 is provided, the same effect as the invention described in each claim can be obtained.

According to the ninth aspect of the present invention, in the optical disk device according to the eighth aspect, prior to recording information on the medium, the phase adjustment value of the filter circuit at the required wobble signal frequency is stored in the storage means. However, during actual recording, the phase adjustment of the filter circuit is performed using the phase adjustment value stored according to the detected wobble signal frequency, so that the wobble signal and the output signal of the filter circuit are independent of the wobble signal frequency. And the current access position on the medium indicated by the wobble can be accurately determined from the filter circuit output signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of an optical disk device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a filter circuit with a phase adjustment function.

FIG. 3 is a frequency characteristic diagram of a BPF.

FIG. 4 is a block diagram illustrating a configuration example of a phase demodulation circuit according to a second embodiment of the present invention.

FIG. 5 is an operation waveform diagram thereof.

[Explanation of symbols]

 Reference Signs List 1 media 9 phase demodulation circuit 13 filter circuit with phase adjustment function 14 carrier generation circuit 15 multiplier 16 filter circuit 17 frequency control circuit 19 phase detection circuit 20 phase adjustment circuit 21 pseudo signal generator 23 storage circuit 31 phase demodulation circuit 32 multiplier Input switching means 33 Phase adjustment control means 34 Peak detection circuit 35 Filter circuit input switching means

Claims (9)

[Claims] 1. A filter circuit whose frequency characteristics and phase characteristics are variable by an external signal, a frequency control circuit that generates a first control signal that mainly determines the frequency characteristics of the filter circuit, A phase control circuit that generates a second control signal that mainly determines phase characteristics; and a phase detection circuit that detects a phase difference between an input signal and an output signal of the filter circuit. The first signal from the control circuit;
With the desired frequency characteristics set by the control signal of
A filter circuit having a phase adjustment function, wherein a phase characteristic of the filter circuit is adjusted by the second control signal from the phase control circuit so as to keep an output of the phase detection circuit constant. 2. The filter circuit according to claim 1, wherein the filter circuit includes a band-pass filter, and the second control signal adjusts the input signal and the output signal of the filter circuit so as to eliminate a phase difference. Filter circuit with phase adjustment function. 3. A pseudo signal generator for selectively outputting a pseudo signal of a desired frequency to the filter circuit, and a level of the second control signal for keeping the output of the phase detection circuit constant. And a storage circuit for storing, wherein the frequency of the pseudo signal by the pseudo signal generator is sequentially changed and output to the filter circuit, and the level of the second control signal at each frequency is stored in the storage circuit. The filter circuit with a phase adjustment function according to claim 1, wherein the filter circuit is stored. 4. The pseudo signal generator is capable of determining the frequency of the pseudo signal output by the first control signal, and sets the frequency of the pseudo signal equal to the cutoff frequency of the filter circuit. 4. The filter circuit with a phase adjustment function according to claim 1, wherein the filter circuit has a phase adjustment function. 5. A filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal, and phase modulation information superimposed on the wobble signal based on an output of the filter circuit of a wobble signal obtained from a medium. A carrier generation circuit that generates a sine wave signal corresponding to the carrier wave; and a multiplier that multiplies the wobble signal and the sine wave signal, and a phase demodulation circuit that demodulates phase modulation information from a result of the multiplication by the multiplier. A multiplier input switching means for selectively switching one input to the multiplier from a sine wave signal by the carrier generation circuit to an output signal of the filter circuit; and one input to the multiplier to the sine wave By switching from the signal to the output signal of the filter circuit, the wobble signal of the multiplier and the output signal of the filter circuit are switched. Phase adjustment control means for detecting a phase difference between the wobble signal and the output signal of the filter circuit from a result of multiplication of the filter circuit and performing a phase adjustment of the filter circuit so that the phase difference disappears. Phase demodulation circuit. 6. A filter circuit whose cutoff frequency characteristic and phase characteristic are variable by an external signal, and phase modulation information superimposed on the wobble signal based on an output of the filter circuit of a wobble signal obtained from a medium. A carrier generation circuit capable of generating a sine wave signal corresponding to a carrier wave and generating a sine wave signal of a specific frequency by an external signal, and a multiplier for multiplying the wobble signal and the sine wave signal, A phase demodulation circuit for demodulating phase modulation information from a result of the multiplication by the multiplier, wherein an input to the filter circuit and one input to the multiplier are selectively used from the wobble signal to a sine wave signal by the carrier generation circuit. Filter input switching means for switching the other input to the multiplier; A multiplier input switching means for selectively switching the output from the filter circuit to a sine wave signal having a specific frequency from the carrier generation circuit, and an input to the filter circuit from the wobble signal by the carrier generation circuit. By switching to the sine wave signal of the specific frequency, and by switching the input to the multiplier to the sine wave signal of the specific frequency by the carrier generation circuit and the output signal of the filter circuit, the multiplier of the multiplier A phase difference between the sine wave signal of the specific frequency and the output signal of the filter circuit is detected from a multiplication result of the sine wave signal of the specific frequency and the output signal of the filter circuit, and the phase difference is eliminated so that the phase difference disappears. Phase adjustment control means for adjusting the phase of the filter circuit;
A phase demodulation circuit comprising: 7. The phase adjustment control means includes a peak detection circuit for detecting a peak value of an output signal of the multiplier,
7. The phase demodulation circuit according to claim 5, wherein the phase of the filter circuit is adjusted so that the output of the peak detection circuit is maximized. 8. A phase demodulation circuit including the filter circuit with a phase adjustment function according to claim 1 and demodulating phase modulation information based on a wobble signal obtained from a medium. An optical disc device comprising the phase demodulation circuit according to claim 1. 9. A storage device for storing a phase adjustment value,
Prior to recording information on the medium, a phase adjustment value of the filter circuit at a required wobble frequency is stored in the storage means in advance, and the storage means is stored in accordance with a wobble frequency detected during actual recording on the medium. 9. The optical disk device according to claim 8, wherein the phase adjustment of the filter circuit is performed using the phase adjustment value stored in the optical disk device.