JP3494405B2 - Demodulation circuit, information recording / reproducing device using the same, phase demodulation system, and phase difference removal method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DVD-DVD having a wobble containing address information consisting of phase modulation in a track.
RW (Digital Video or Versatile Disk-ReWr
itable) information recording and reproducing apparatus for media such as a disk, a demodulation circuit used for address demodulation in the device, relates to a phase demodulation system, and the phase difference removing method.

[0002]

2. Description of the Related Art Generally, in recording media, in order to accurately detect the linear velocity at each radial position during manufacture,
It adopts a format for wobbling a track so that the wobble signal frequency becomes constant when CLV (constant linear velocity) rotation control is performed. Therefore, the information recording / reproducing apparatus for the medium detects the wobbling signal to control the rotation of the medium or generate the recording clock. Also, address information is required so that the recording position in the unrecorded area can be specified,
For example, as disclosed in Japanese Patent Application Laid-Open No. 10-69646, a method of performing phase modulation on the above-mentioned track wobble has been considered. Although this phase modulation method can be classified into more detailed methods, the required amount of information and the S / N (Signal Noise Ratio) of the detection signal are in a trade-off like other modulation methods. In the case of an optical disc, the signal quality obtained from the medium is poor, so the binary phase modulation method (BPSK or DPSK, binary modulation of 0 ° and 180 °) capable of obtaining a relatively high S / N is most suitable.

As a demodulation circuit for this phase-modulated address information (wobbling signal), Japanese Patent Publication No. 6-1989.
The analog system shown in Japanese Patent Laid-Open No.
There is a digital system disclosed in Japanese Patent No. 260413. Based on the wobbling signal, these generate a carrier wave on which the phase information is superimposed by a PLL or the like in the subsequent stage,
The phase difference between them (0 ° or 180 ° in the case of BPSK) is detected and the information is demodulated. However, if a phase shift occurs between the original carrier component of the wobbling signal and the carrier generated by the PLL, the performance of phase demodulation deteriorates and erroneous detection frequently occurs.

[0004]

These conventional examples are systems used in the field of cameras and communication, and the following problems occur in optical discs.

With an optical disc, only a very low signal quality can be obtained in the area after data recording. Therefore, after passing the wobbling signal through a filter such as a BPF, a carrier required for demodulation is generated from a signal generated by a PLL or the like based on the signal. Since this filter efficiently removes a phase modulation component and a noise component that are disturbances, it has a configuration in which a phase change (delay) easily occurs. Further, when accessing the medium by CAV (constant angular velocity) rotation on the optical disc, the carrier frequency of the wobbling signal changes depending on the radial position, so the phase change (delay) by the above-mentioned filter.
Is particularly likely to occur. This phase change causes a phase shift between the original carrier wave component of the wobbling signal and the generated carrier wave, which deteriorates the detection accuracy as described above.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a demodulation circuit capable of properly detecting a phase shift and correcting the shift and accurately demodulating, and an information recording / reproducing apparatus using the demodulation circuit.

[0007]

A demodulation circuit according to a first aspect of the present invention is a demodulation circuit for detecting position information on a medium recorded by wobbling of a track by using a two-phase phase modulation method. A carrier generation circuit for detecting a carrier wave of a wobbling signal obtained from the medium, and a phase adjustment for generating a phase comparison signal having a phase difference of 90 ° with the output signal of the carrier generation circuit and finely adjustable in phase. A circuit and a multiplier that multiplies the wobbling signal and the phase comparison signal are provided, and the phase difference between the wobbling signal and the phase comparison signal is detected from the output level of the multiplier.

Therefore, since the phase difference is detected based on the multiplication result of the phase comparison signal having a phase difference of 90 ° from the carrier wave and the wobbling signal, the carrier wave detecting system and the wobbling signal detecting system are used when the frequency changes. Even if a difference occurs in the delay amount of, the phase shift between the carrier wave and the wobbling signal can be detected. In particular, the digital circuit can be easily constructed.

According to a second aspect of the present invention, in the demodulation circuit according to the first aspect, a low-pass detector connected to the output side of the multiplier is provided, and the phase difference is detected by the low-pass detector. This is performed based on the detected low-frequency component of the output signal of the multiplier.

Therefore, the phase difference is detected from the carrier wave by 90 degrees.
Since it is performed based on the low-frequency component of the multiplier output of the phase comparison signal and the wobbling signal having the phase difference of °, the phase shift can be detected with the simplest circuit configuration.

According to a third aspect of the present invention, in the demodulation circuit according to the first or second aspect, an integrator connected to the output side of the multiplier is provided, and the detection of the phase difference is detected by the integrator. According to the result of integration of the output signals of the multiplier,

Therefore, the phase difference is detected from the carrier by 90
Since it is performed based on the integration result of the output of the multiplier of the phase comparison signal having a phase difference of ° and the wobbling signal, it is possible to detect the phase shift with high detection accuracy with a simple configuration.

According to a fourth aspect of the present invention, in the demodulation circuit according to the first, second or third aspect, an amplitude detection circuit for detecting the amplitude of the wobbling signal and a gain for reaching a preset target amplitude are calculated. And an amplitude adjustment circuit for multiplying the phase comparison signal by the gain.

Therefore, the amplitude of the wobbling signal is detected, the gain reaching the preset target amplitude is calculated,
Since the gain is multiplied by the phase comparison signal, it is possible to stably detect the phase shift without using an AGC circuit that keeps the amplitude of the wobbling signal constant, especially in the case of a digital circuit. The invention according to claim 5 is a contract
In the demodulation circuit according to any one of the first to fourth aspects,
The wobbling signal is controlled to have a constant amplitude.
The invention according to claim 6 is the invention according to any one of claims 1 to 5.
In the demodulation circuit described above, the phase difference is detected by a wob
The phase modulation format should be performed in a specific area.
It was The invention according to claim 7 is the demodulation circuit according to claim 6.
Where the specific region is a wobble phase modulation former
On the other hand, it is a region where no phase change occurs. Claim 8
The described invention is the restoration according to any one of claims 1 to 7.
In the adjustment circuit, the phase adjustment circuit outputs the output of the multiplier.
Force level to the wobbling signal and the phase comparison signal
By adjusting the phase difference with
The phase difference between the output signal of the composition circuit and the wobbling signal is 0.
The phase is controlled so that

A demodulation circuit according to a ninth aspect of the present invention is a demodulation circuit that detects position information on a medium recorded by wobbling of tracks by using a two-phase phase modulation method, and is obtained from the medium. A carrier generation circuit that detects the carrier wave of the wobbling signal, a phase adjustment circuit that generates a phase comparison signal whose phase can be finely adjusted based on the output signal of this carrier generation circuit, and a selection signal that specifies a specific timing based on this phase comparison signal And a switch for turning on / off the output of the subtractor that performs the subtraction operation of the wobbling signal and the phase comparison signal by the selection signal. The phase difference between the wobbling signal and the phase comparison signal is detected from the output level.

Therefore, the output of the subtractor of the phase comparison signal obtained from the wobbling signal and the carrier wave is turned on / off by the selection signal generated based on the phase comparison signal, and the position of the wobbling signal and the phase comparison signal is determined by the output. Since the phase difference is detected, the phase shift between the carrier wave and the wobbling signal can be detected even when the delay amount between the carrier wave detecting system and the wobbling signal detecting system is different, such as when the frequency changes. Further, in the analog method, it is not necessary to generate an analog signal having a 90 ° phase difference with a carrier wave, which requires a large-scale circuit.

According to a tenth aspect of the present invention, in the demodulation circuit according to the ninth aspect , an integrator connected to the output side of the switch is provided, and the phase difference is detected by the integrator detected by the integrator. I decided to do it based on the results.

Therefore, since the phase shift is detected based on the integrated result of the outputs of the switches, the phase shift can be detected with high detection accuracy with a simple structure.

The demodulation circuit according to the invention of claim 11 is 2
A demodulation circuit for detecting position information on a medium recorded by wobbling a track using a phase-phase modulation method, a carrier generation circuit for detecting a carrier wave of a wobbling signal obtained from the medium, and a carrier generation circuit. A phase adjustment circuit that generates a phase comparison signal whose phase can be finely adjusted based on the output signal of the circuit, a selection signal generation circuit that outputs a selection signal at a specific timing based on the phase comparison signal, the wobbling signal, and the phase A subtractor for performing a subtraction operation on the comparison signal; an inverting circuit for inverting the output signal of the subtractor; and a selector for selecting the output of the subtractor and the output of the inverting circuit by the selection signal, The phase difference between the wobbling signal and the phase comparison signal is detected from the output level of the selector.

Therefore, the subtraction calculation result of the phase comparison signal obtained from the wobbling signal and the carrier wave and its inversion result are
Since the phase difference between the wobbling signal and the phase comparison signal is detected by the output selected by the selection signal created based on the phase comparison signal, the delay between the carrier detection system and the wobbling signal detection system, such as when the frequency changes Even if there is a difference in amount, the phase shift between the carrier wave and the wobbling signal can be detected. Since the sensitivity of the detection signal is doubled as compared with the case of the invention described in claim 5, stable detection is also possible. Further, in the analog method, it is not necessary to generate an analog signal having a 90 ° phase difference with a carrier wave, which requires a large-scale circuit.

According to a twelfth aspect of the present invention, in the demodulation circuit according to the eleventh aspect , the selector includes an integrator connected to an output side of the selector, and the phase difference is detected by the integrator. It was performed based on the integrated result of the output of.

Therefore, since the phase shift is detected based on the integrated result of the output of the selector, the phase shift can be detected with high detection accuracy with a simple structure.

According to a thirteenth aspect of the present invention, in the demodulation circuit according to any one of the ninth to twelfth aspects, the wobbling signal is controlled to have a constant amplitude.

Therefore, since the wobbling signal whose amplitude is controlled to a constant value is used, the level of the phase deviation detection signal does not change according to the amplitude, and the phase deviation can be detected with high accuracy.

According to a fourteenth aspect of the present invention, in the demodulation circuit according to any one of the ninth to thirteenth aspects, the detection of the phase difference is performed in a specific area on the wobble phase modulation format. I did it.

Therefore, since the phase difference is detected at a specific position in the wobble phase modulation format, even if the detection method is such that the level of the phase shift detection signal is affected by the phase modulation data, a constant phase is detected. A stable phase shift amount can be detected based on the influence of the modulation data.

According to a fifteenth aspect of the present invention, in the demodulation circuit according to the fourteenth aspect , the specific region is a region in which no phase change occurs in the wobble phase modulation format.

Therefore, since the phase difference is detected in the area where the phase does not change in the wobble phase modulation format, there are many choices of detection signals and the phase shift can be detected with a simple circuit configuration. Further, in the phase modulation, there are many regions where the phase change does not occur due to the generation of the carrier wave, and therefore, the detection timing of the phase shift becomes rich.

According to a sixteenth aspect of the present invention, in the phase demodulating circuit according to any one of the ninth to fifteenth aspects, the phase adjusting circuit is configured so that the detected phase difference becomes zero. The phase of the phase comparison signal is controlled.

[0030] Thus, as the phase difference detected by the detection processing of the phase difference by demodulating circuit to 15 according claims 9 becomes 0, since the control the phase of the phase adjustment circuit, dynamically changing carrier It is possible to construct a system that automatically follows the difference in the delay amount of the wobbling signal.

According to a seventeenth aspect of the invention, there is provided an information recording / reproducing apparatus in which an optical system for condensing a light beam on a medium and condensing reflected light from the medium on a light receiving element, and the light receiving element to the medium. A reproducing circuit that detects the above information, a servo circuit that detects the position data of the condensed light beam on the medium from the light receiving element, and controls the position of the light beam on the medium based on the position data. A mechanism system for moving the position of the laser light is provided, and the position data on the medium is detected using the demodulation circuit according to claim 16 .

Therefore, since the demodulation circuit according to claim 16 is used as the demodulation circuit of the information recording / reproducing apparatus, the adjustment process can be omitted, and an inexpensive and highly reliable apparatus can be manufactured. Further, the invention according to claim 18 is a phase demodulation system for detecting position information on a medium recorded by wobbling of tracks by using a two-phase phase modulation method, wherein a wobbling signal obtained from the medium is used. A bandpass filter for removing noise, a circuit that generates a phase comparison signal based on a carrier wave of the wobbling signal that has passed through the bandpass filter, and a phase difference between the wobbling signal obtained from the medium and the phase comparison signal. And a tracking system for adjusting the phase of the phase comparison signal so that the angle becomes 90 °.
The invention according to claim 19 is the phase demodulation system according to claim 18 , wherein the tracking system multiplies a wobbling signal obtained from the medium by the phase comparison signal, and an output level of the multiplier. A detector for detecting a phase difference between the wobbling signal obtained from the medium and the phase comparison signal based on the above. The invention according to claim 20 is the phase demodulating system according to claim 18 or 19 , wherein the tracking system is
A low pass filter for removing noise from a wobbling signal obtained from the medium is provided, and the phase comparison is performed so that a phase difference between the wobbling signal passed through the low pass filter and the phase comparison signal is 90 °. Adjust the phase of the signal. Further, the invention according to claim 21 is
In order to extract the phase modulation component recorded by wobbling on the track in the medium using the two-phase phase modulation method, the position of the carrier of the wobbling signal that has passed through the bandpass filter and the position of the wobbling signal obtained from the medium. A phase difference removing method for removing a phase difference, the step of generating a phase comparison signal by a phase comparison signal generation circuit based on a carrier wave of the wobbling signal that has passed through the bandpass filter, and a wobbling signal obtained from the medium. Adjusting the phase of the phase comparison signal by the tracking system so that the phase difference from the phase comparison signal becomes 90 °.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
Or, it demonstrates based on FIG. First, a schematic configuration and an operation of an optical disc device which is an information recording / reproducing device commonly used in each embodiment described later will be described with reference to FIG.

The light emitted from the light source 1 such as a semiconductor laser is coupled lens 2, beam splitter 3, 1/4.
The optical system 6 including the wave plate 4 and the objective lens 5 focuses the light on the recording surface 7 a on the medium 7. The reflected light from the recording surface 7a returns to the optical system 6 again, and the beam splitter 3
Through the condenser lens 8 and condensed on the light receiving element 9 to be converted into an electric signal. The output of the light receiving element 9 is usually converted from current to voltage by the I / V amplifier 10 and various calculations are performed, but there are also cases where calculations are performed with the current as it is. Usually light receiving element
9 and the I / V amplifier 10 are divided into a plurality of parts, and a focus error signal indicating the distance between the media surface and the light spot focus, a track error signal indicating the position of the track on the media surface and the light spot, and the media 7 Recording side 7
An operation such as an RF signal for detecting the information recorded on a is performed. In FIG. 1, the focus error signal and the track error signal are calculated in the servo circuit 11, and the mechanical system 12 is driven from the position data of them to move the light spot to the target position. Further, the information on the recording surface 7a of the medium 7 is calculated into an RF signal in the reproducing circuit 13 and sent to the signal processing (not shown) in the subsequent stage. A laser driver 14 drives the light source 1.

It should be noted that the wobbling signal used in the present embodiment and each of the embodiments described later is obtained from the reproduced signal because the detection method differs depending on the divided shape of the light receiving element 9, but it is the simplest. Since the example is a case of detecting from the push-pull signal (one of the track error signals) obtained from the difference between the left and right of the light receiving element dividing line along the track, the push-pull signal output from the servo circuit 11 will be described below. Description will be made on the assumption that the demodulation circuit 15 operates based on the signal. Here, the demodulation circuit 15 is characteristically configured in each of the embodiments.

First, in order to extract the phase modulation component from the wobbling signal obtained from the optical system 6, it is necessary to generate a carrier wave that is not modulated with the same frequency and phase as the wobbling signal. Therefore, the basic phase demodulation operation of the demodulation circuit 15 will be described with reference to the block diagram shown in FIG. 2 and the demodulated signal waveform diagram shown in FIG.

First, a BPF (bandpass filter) is used to remove noise and phase modulation components from the wobbling signal.
A carrier signal is generated using a carrier generation circuit 18 including a band limiting filter such as 16 and a PLL (Phase Locked Loop) 17 for generating a stable signal. This carrier signal has the same frequency as the wobbling signal and the phase is stable. On the other hand, the wobbling signal is passed through an LPF (low pass filter) 19 in order to remove only the noise component, and a multiplier 20 performs multiplication calculation with the carrier signal. The output signal from the multiplier 20 is a low band detector 21 (phase shift A), an integrator 22 (phase shift B), or a low band detector 23 (phase shift) that obtains a low band component of the output signal of the integrator 22. By inputting into C) or the like, phase demodulation information for detecting the phase shift is obtained.

Although FIG. 3 shows the wobbling signal and the carrier signal which have been subjected to the phase modulation, the output of the multiplier 20 and the output of the low frequency detector 21, the phase modulation information and the low frequency detector 21. As can be seen by comparing the outputs, the phase modulation information is reproduced. The basic phase demodulation operation is as described above.

In addition to the basic configuration and operation of such phase demodulation, the characteristic configuration and operation according to the present embodiment will be described with reference to FIGS. 2, 4 and 5.
(Corresponding to the inventions described in 2, 3, 12 and 13).

In this embodiment, a phase adjusting circuit 24 is added to detect the phase shift between the carrier wave signal generated by the carrier wave generating circuit 18 and the wobbling signal. The phase of the BPF 16 that removes noise components and phase modulation components included in the wobbling signal easily changes depending on the frequency. Therefore, the carrier wave signal generated from the signal that has passed through the BPF 16 and the LPF 1 with a small phase change
A phase difference occurs in the wobbling signal that passes only 9. Therefore, the phase adjustment circuit 24 generates a phase comparison signal having a phase difference of 90 ° from the carrier signal. Assuming that the carrier signal is a sin wave (sine wave), the phase comparison signal has a relationship of a cos wave (cosine wave). In the case where the phase adjusting circuit 24 has an analog circuit configuration, it may be easier to design if it is included in the circuit of the PLL 17, so that it may be used. When the phase comparison signal and the wobbling signal that has passed through the LPF 19 are multiplied by the multiplier 20, a signal that changes according to the phase shift 90 + α degrees α between the two is obtained from the multiplication result. This phase shift of α is the same as the phase shift between the generated carrier wave signal and the wobbling signal.

An example of this signal waveform is shown in FIGS. 4 shows a case where there is no phase shift, and FIG. 5 shows a case where there is a phase shift. Here, each signal shown in these figures is: PMin: After LPF of wobbling signal (left axis) cos: Phase comparison signal (left axis) Mpy x: Multiplier output (left axis) ave x: Multiplier output Low frequency component (left axis) Int x: Integration result of multiplier output (right axis).

From FIG. 4, when there is no phase shift, that is, since the phase difference between the LPF 19 of the wobbling signal and the phase comparison signal is 90 °, the low-frequency component ave has a 0 level and the integration result Int has a specific level. Up and down the standard. But,
When there is a phase shift as shown in FIG. 5, the low frequency component ave is 0.
Changes to a certain level on the plus side, and the integrated result Int gradually increases. If the polarity of the phase shift is opposite,
The low-frequency component ave is on the negative side, and the integration result Int is in the decreasing direction. As an ave detection circuit, a low band detector 2 such as an LPF for detecting a low band component of the output of the multiplier 20 is used.
Examples of the detection circuit for 1 and Int include an integrator 22 that integrates the output of the multiplier 20. It is also effective to use the low frequency detector 23 that detects the low frequency component of the output of the integrator 22.

Then, the phase adjusting circuit 24 finely adjusts the phase of the phase comparison signal so that the detected phase difference becomes zero. That is, by controlling the phase of the phase adjustment circuit 24 so that the detected phase difference becomes 0, there is a system that automatically follows the delay amount difference between the carrier signal and the wobbling signal, which changes dynamically. Can be built.

A second embodiment of the present invention will be described with reference to FIGS. The same components as those of the entire structure of the information recording / reproducing apparatus and the parts shown in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted (the same applies to the following embodiments). This embodiment corresponds to the invention described in claims 5 to 8.

In the present embodiment, the phase adjustment circuit 2
A circuit for outputting a phase comparison signal capable of finely adjusting the phase of the carrier wave signal generated by the carrier wave generation circuit 18 around 0 ° as 5 is used. That is, if the carrier wave signal is a sin wave, the phase comparison signal is also a sin wave. The subtractor 26 subtracts the difference between the wobbling signal passed through the LPF 19 and the phase comparison signal in order to detect the phase shift.
Ask in. The polarity of the output of the subtracter 26 is further inverted by the inverting circuit 27. In the selection signal generation circuit 28, a selector signal (corresponding to a binarized signal of a cos wave) indicating a section corresponding to a phase of 90 ° to 270 ° based on the phase comparison signal is switched by a selector 29 (or a switch (not shown)). ) Is output. In the case of a switch (not shown), the output of the subtractor 26 is turned on / off according to the selection signal, and in the case of the selector 29, the output of the subtractor 26 and the output of the inverting circuit 27 are switched. The output of the selector 29 (or switch) is a signal indicating the phase shift α between the carrier wave signal and the wobbling signal. The signal level is set according to the phase shift.

Waveform examples for detecting the phase shift are shown in FIGS. 7 and 8. FIG. 7 shows a state without phase shift, and FIG. 10 shows a state with phase shift. Here, each signal shown in these figures is: PMin: after LPF of wobbling signal (left axis) sin: phase comparison signal (left axis) sub: selector output (left axis) sel: selection signal (numerical value is irrelevant , H / L only) Int x: Selector output integration result (right axis).

From FIG. 7, when there is no phase shift, neither the selector output sub nor the integration result Int is 0. When there is a phase shift, the output of the subtractor 26 is 27 on the negative side at 90 ° to 270 ° of the phase comparison signal, and 0 ° to 90 °.
In the range of 0 ° to 360 °, the output is made on the plus side (there may be the opposite). 90 ° of the phase comparison signal depending on the selection signal
At 270 °, the output of the inverting circuit 27 is selected and the signal converted to the positive side is output, and 0 ° to 90 ° and 270 ° to 360 are output.
At 0, the output of the subtractor 26 is selected as it is and output to the circuit in the subsequent stage. This is shown in FIG. When a switch is used instead of the selector 29, only half the phase comparison (only the output of the subtractor 26) is performed, so the signal level becomes half compared to the selector 29 method. As a circuit in the latter stage of the selector 29 or the switch output, a low band detector 30 such as an LPF for detecting the low band of the sub signal, and an integrator 31 for detecting the Int signal may be used.

The third embodiment of the present invention will be described with reference to FIG. The present embodiment corresponds to the invention described in claims 4 and 9.

As described above, the phase shift is detected by the output levels of the multiplier 20 and the subtractor 26.
This level changes depending on the amplitude of the wobbling signal or the phase comparison signal which is the input signal. Generally, the carrier wave is controlled to have a constant amplitude, but since the wobbling signal is a signal detected from the medium 7, an amplitude change occurs. Therefore, it is preferable to install an AGC circuit or the like for controlling the amplitude of the wobbling signal at a stage before the demodulation circuit 15. Of course, in order to suppress the amplitude fluctuation after passing the LPF 19,
The signal after LPF may be kept constant.

Further, the amplitude of the wobbling signal is detected,
The amplitude of the phase comparison signal may be changed. This method can be easily realized when it is configured by a digital circuit. This block diagram is shown in FIG. The wobbling signal is digitized by an ADC (analog / digital converter) 32. Further, as in the case described above, the carrier generation circuit 1
At 8, a carrier signal is generated. The carrier signal is ADC
It may be generated from the already binarized wobbling signal instead of the 32 output. Since it is generated by a digital circuit, this carrier signal is a binarized signal. The sin wave data is stored in the ROM 33 in order to output the sin wave shape of the wobbling signal as the phase comparison signal. Normally, the data of the ROM 33 is output at a timing controlled by the output of the phase adjusting circuit 24 and the output of the counter 34 to form a phase comparison signal. The digital wobbling signal and the phase comparison signal thus generated can be detected by the multiplier 20 and the subtractor 26 in the same manner as described above. Here, the amplitude of the wobbling signal is detected by the amplitude detection circuit 35 based on the data taken in by the ADC 32, and the difference from the preset target amplitude is obtained as a gain. This gain may be multiplied by the data in the ROM 33, the result stored in the RAM 36, and output from the RAM 36 as a phase comparison signal. This R
The portion composed of the OM 33 and the RAM 36 is the amplitude adjusting circuit 37. Further, the phase adjusting circuit 24 generates a phase comparison signal in which a phase shift of 0 ° or 90 ° is generated based on the carrier signal, but in this digital configuration, it is easy to change the start address of the counter 34. It is also possible to cause a phase shift.

A fourth embodiment of the present invention will be described with reference to FIGS. The present embodiment relates to claim 10.
And 11 corresponds to the invention.

The phase modulation format is usually divided into a sync area including a special pattern for synchronization, a data area including address information and the like, and a constant phase area for pulling in a carrier wave (see FIG. 3). ). In this, because the phase modulation data cannot be predicted in the data area,
It is difficult to obtain the effect of the present invention. Waveform changes in the case of the fourth embodiment at the phase change point (2 wobbles) are shown in FIGS. 10 and 11. FIG. 10 shows the case without phase shift, and FIG. 11 shows the case with phase shift. The first half 1 wobble has the same phase relationship as in the second embodiment, but the second half 1 wobble has the opposite phase shift detection characteristic because the PMin signal having a 180 ° phase difference from the carrier wave is input. Therefore, ave is 0 as in the case where there is a phase shift and the case where there is no phase shift.
Becomes The last value of Int is the same value with or without phase shift, but the low-frequency component of Int (not shown, but may be considered as an average) is on the plus side to detect the phase shift. . The same applies to the case of the second embodiment.

From this fact, since the phase detection value has a correlation with the phase modulation data, it is necessary to predict the phase information at the detection point in implementing the present invention. Since the pattern can be predicted in the synchronization region, if the number of wobbles, which is the change point of the phase, is limited, the low frequency detection circuit 2 that detects the low frequency component of Int as described with reference to FIGS. 10 and 11.
A phase shift of 3 or the like can be detected. However, the detection method is also simple, and the method that can be expected to be accurate is the method of detecting the phase shift in the constant phase region.

[0054]

According to the demodulation circuit of the present invention, the phase difference is detected based on the multiplication result of the phase comparison signal having a phase difference of 90 ° from the carrier wave and the wobbling signal. Even if there is a difference in the amount of delay between the carrier detection system and the wobbling signal detection system, such as when the signal changes, the phase shift between the carrier and the wobbling signal can be detected. it can.

According to the invention described in claim 2, in the demodulation circuit according to claim 1, the phase difference is detected from the carrier wave by 9
Since it is performed based on the low-frequency component of the multiplier output of the phase comparison signal having a phase difference of 0 ° and the wobbling signal,
The phase shift can be detected with the simplest circuit configuration.

According to the third aspect of the present invention, in the demodulation circuit according to the first or second aspect, the phase difference is detected by the output of the multiplier of the phase comparison signal having a phase difference of 90 ° from the carrier wave and the wobbling signal. Since the calculation is performed based on the integration result, it is possible to detect the phase shift with high detection accuracy with a simple configuration.

According to the invention of claim 4, claim 1,
In the demodulation circuit described in 2 or 3, the amplitude of the wobbling signal is detected, the gain that reaches the preset target amplitude is calculated, and the gain is multiplied by the phase comparison signal, so that it is particularly configured digitally. In the case of the circuit, the phase shift can be stably detected without using the AGC circuit which keeps the amplitude of the wobbling signal constant.

According to the demodulation circuit of the ninth aspect of the present invention, the output obtained by turning on / off the subtractor output of the phase comparison signal obtained from the wobbling signal and the carrier wave by the selection signal generated based on the phase comparison signal. By detecting the phase difference between the wobbling signal and the phase comparison signal, the carrier and the wobbling are detected even when there is a difference in the delay amount between the carrier detection system and the wobbling signal detection system, such as when the frequency changes. In addition to being able to detect the phase shift of the signal, it is not necessary to generate an analog signal having a 90 ° phase difference from the carrier wave, which requires a large-scale circuit in the analog method.

According to the invention of claim 10 ,
In the demodulation circuit described in 9 , the phase shift is detected based on the integrated result of the outputs of the switches, so that the phase shift can be detected with high detection accuracy with a simple configuration.

According to the demodulation circuit of the eleventh aspect of the present invention, the subtraction calculation result of the phase comparison signal obtained from the wobbling signal and the carrier wave and its inversion result are selected by the selection signal generated based on the phase comparison signal. Since the phase difference between the wobbling signal and the phase comparison signal is detected by this output, even if there is a difference in the amount of delay between the carrier detection system and the wobbling signal detection system, such as when the frequency changes, Since the phase shift of the wobbling signal can be detected and the sensitivity of the detection signal is doubled as compared with the case of the invention of claim 9 , stable detection is possible, and further, the analog method Does not need to generate an analog signal having a 90 ° phase difference with a carrier wave, which requires a large-scale circuit.

According to the invention of claim 12 ,
In the demodulation circuit described in 11 , the phase shift is detected based on the integrated result of the output of the selector, so that the phase shift can be detected with high detection accuracy with a simple configuration.

According to the invention of claim 13 ,
In the demodulation circuit described in any one of 9 to 12 , since the wobbling signal controlled to have a constant amplitude is used, the level of the phase shift detection signal does not change according to the amplitude, and the phase with high accuracy is obtained. Deviation can be detected.

According to the invention of claim 14 ,
In the demodulation circuit described in any one of 9 to 13 , since the phase difference is detected at a specific position in the wobble phase modulation format, the level of the phase shift detection signal is affected by the phase modulation data. Even with the detection method, a stable phase shift amount can be detected with a constant degree of influence of phase modulation data.

According to the invention of claim 15 ,
In the demodulation circuit described in 14 , the phase difference is detected in the area where the phase change does not occur in the wobble phase modulation format, so there are many detection signal options and the phase shift can be detected with a simple circuit configuration. Also, in the phase modulation, there are many regions in which the phase change does not occur due to the generation of the carrier wave, and therefore, the detection timing of the phase shift becomes rich.

According to the invention of claim 16 ,
In the phase demodulation circuit according to any one of 9 to 15, so that the phase difference detected by the detection processing of the phase difference due to the demodulation circuit of claims 9 to 15, wherein is 0, and controls the phase of the phase adjustment circuit Therefore, it is possible to construct a system that automatically follows the delay amount difference between the carrier wave and the wobbling signal, which changes dynamically.

According to the information recording / reproducing apparatus of the invention described in claim 17, a demodulating circuit of the information recording / reproducing apparatus is provided.
Since the demodulation circuit described in 16 is used, the adjustment process can be omitted, and an inexpensive and highly reliable device can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an optical disk device common to each embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a demodulation circuit according to the first embodiment of the present invention.

FIG. 3 is a waveform diagram showing a basic demodulated signal example of a demodulation operation.

FIG. 4 is a signal waveform diagram when there is no phase shift.

FIG. 5 is a signal waveform diagram when there is a phase shift.

FIG. 6 is a block diagram showing a configuration example of a demodulation circuit according to a second embodiment of the present invention.

FIG. 7 is a signal waveform diagram when there is no phase shift.

FIG. 8 is a signal waveform diagram when there is a phase shift.

FIG. 9 is a block diagram showing a configuration example of a demodulation circuit according to a third embodiment of the present invention.

FIG. 10 is a signal waveform diagram in the case where there is no phase shift according to the fourth embodiment of this invention.

FIG. 11 is a signal waveform diagram when there is a phase shift.

[Explanation of symbols]

6 Optical system 7 media 9 Light receiving element 11 Servo circuit 12 Mechanical system 13 Playback circuit 15 Demodulation circuit 18 Carrier wave generation circuit 20 multiplier 21 Low frequency detector 22 Accumulator 24,25 Phase adjustment circuit 26 Subtractor 27 Inversion circuit 28 Selection signal generation circuit 29 selector 31 integrator 35 Amplitude detection circuit 37 Amplitude adjustment circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 20/14 351 G11B 7/004 H04L 27/22

Claims (21)

(57) [Claims] 1. A demodulation circuit for detecting position information on a medium recorded by wobbling of a track by using a two-phase phase modulation method, the carrier generation for detecting a carrier of a wobbling signal obtained from the medium. A circuit, a phase adjustment circuit for generating a phase comparison signal having a phase difference of 90 ° with the output signal of the carrier wave generation circuit, and capable of finely adjusting the phase, and a multiplication process of the wobbling signal and the phase comparison signal. A demodulator circuit for detecting the phase difference between the wobbling signal and the phase comparison signal from the output level of the multiplier. 2. A low-pass detector connected to an output side of the multiplier, wherein the phase difference is detected based on a low-pass component of an output signal of the multiplier detected by the low-pass detector. The demodulation circuit according to claim 1, which is configured to perform. 3. An integrator connected to the output side of the multiplier, wherein the phase difference is detected based on an integration result of output signals of the multiplier detected by the integrator. The demodulation circuit according to Item 1 or 2. 4. An amplitude detection circuit that detects the amplitude of the wobbling signal, and an amplitude adjustment circuit that calculates a gain that reaches a preset target amplitude and multiplies the gain by the phase comparison signal. The demodulation circuit according to 1, 2, or 3. 5. The wobbling signal is controlled to have a constant amplitude.
The demodulation according to any one of claims 1 to 4, which is controlled.
circuit. 6. The wobble phase modulation is used for detecting the phase difference.
The format is performed in a specific area.
6. The demodulation circuit according to any one of 5 to 5. 7. The specific region is a wobble phase modulation frame.
Requested to be a region on the format where the phase does not change
The demodulation circuit according to Item 6. 8. The phase adjustment circuit outputs the output of the multiplier.
From the level to the wobbling signal and the phase comparison signal
The carrier wave is generated by adjusting the phase difference of
The phase difference between the output signal of the circuit and the wobbling signal is 0
8. The phase is controlled so that
The demodulation circuit described in. 9. A demodulation circuit for detecting position information on a medium recorded by wobbling a track by using a two-phase phase modulation method, the carrier wave generation detecting a carrier wave of a wobbling signal obtained from the medium. A circuit, a phase adjustment circuit that generates a phase comparison signal whose phase can be finely adjusted based on the output signal of this carrier generation circuit, and a selection signal generation circuit that outputs a selection signal at a specific timing based on this phase comparison signal, A subtractor for performing a subtraction operation between the wobbling signal and the phase comparison signal; and a switch for turning on / off the output of the subtractor according to the selection signal, and the wobbling signal and the phase from the output level of the switch. A demodulation circuit that detects the phase difference from the comparison signal. 10. comprises a multiplier connected to the output side of the switch, the detection of the phase difference, according to claim 9, wherein you performed based on the output of the accumulation result of the switch to be detected by the integrator Demodulator circuit. 11. A demodulation circuit for detecting position information on a medium recorded by wobbling a track by using a two-phase phase modulation method, the carrier wave generation for detecting a carrier wave of a wobbling signal obtained from the medium. A circuit, a phase adjustment circuit that generates a phase comparison signal whose phase can be finely adjusted based on the output signal of this carrier generation circuit, and a selection signal generation circuit that outputs a selection signal at a specific timing based on this phase comparison signal, A subtracter that performs a subtraction operation of the wobbling signal and the phase comparison signal, an inverting circuit that inverts the output signal of the subtractor, and a selector that selects the output of the subtractor and the output of the inverting circuit by the selection signal. And a phase difference between the wobbling signal and the phase comparison signal is detected from the output level of the selector. Tone circuit. 12. comprising the connected integrator to an output side of said selector, detecting the phase difference, according to claim 11, wherein that to perform on the basis of the integration result of the output of said selector which is detected by the integrator Demodulator circuit. 13. The demodulation circuit according to any one of the wobbling signal to claims 9 are controlled to a constant amplitude 12. 14. The phase difference detection is performed in a specific area in a wobble phase modulation format.
14. The demodulation circuit according to any one of 9 to 13 . 15. The demodulation circuit according to claim 14 , wherein the specific region is a region in which no phase change occurs in the wobble phase modulation format. 16. The phase adjustment circuit, the phase demodulation circuit according to any one of claims 9 to 15 detected phase difference to control the phase of said phase comparison signal such that 0. 17. An optical system for condensing a light beam on a medium and condensing reflected light from the medium on a light receiving element, and a reproducing circuit for detecting information on the medium from the light receiving element. A servo circuit for detecting the position data of the light beam on the medium from the light receiving element and controlling the position of the light beam on the medium based on the position data; and a mechanism system for moving the position of the laser beam. An information recording / reproducing apparatus, comprising: the demodulating circuit according to claim 8 or 16 , wherein the position data on the medium is detected. 18. A phase demodulation system for detecting position information on a medium recorded by wobbling a track using a two-phase phase modulation method, for removing noise from a wobbling signal obtained from the medium. A band pass filter, a circuit that generates a phase comparison signal based on a carrier wave of the wobbling signal that has passed through the band pass filter, and a phase difference between the wobbling signal obtained from the medium and the phase comparison signal is 90 °. And a tracking system that adjusts the phase of the phase comparison signal as described above. 19. The tracking system includes a multiplier that multiplies the wobbling signal obtained from the medium and the phase comparison signal, and the wobbling signal and the phase obtained from the medium based on an output level of the multiplier. The phase demodulation system according to claim 18 , further comprising: a detector that detects a phase difference from the comparison signal. 20. The tracking system includes a low pass filter for removing noise from a wobbling signal obtained from the medium, and a phase difference between the wobbling signal passed through the low pass filter and the phase comparison signal. phase demodulation system of claim 18 or 1 9 but adjusting the phase comparison signal phase to be 90 °. 21. A carrier of the wobbling signal that has passed through a bandpass filter and the medium to extract a phase modulation component recorded by wobbling on a track in the medium using a two-phase phase modulation method. A phase difference removing method for removing the phase difference of the wobbling signal, wherein the phase comparing signal generating circuit generates a phase comparing signal based on the carrier wave of the wobbling signal passed through the band pass filter; Adjusting the phase of the phase comparison signal by a tracking system so that the phase difference between the wobbling signal and the phase comparison signal becomes 90 °.