JPH09326122A - Method and device for regenerating wobble signal of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always regenerate a precise wobble signal with simple constitution. SOLUTION: A quadripartite photodetector 11 is divided into two parts in the left/right directions of a track on an optical disk, and the level of a composite signal V1 outputted from one side photodetectors 11a, 11b is changed based on a control voltage Vcon. A difference signal V5 having the level of a difference between the level-changed signal V4 and the level of the composite signal V2 outputted from the other side photodetectors 11c, 11d is generated, and the difference signal V5 is made the control voltage Vcon through a low-pass filter 34 when an EFM signal is a high level based on the EFM signal regenerated from an RF signal obtained from reflection light from an optical disk, and the difference signal V5 is regenerated as the wobble signal WB through a band-pass filter 35. Thus, the wobble signal without noise and EFM signal components is regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wobble signal reproducing method used in an information recording / reproducing apparatus for an optical disc and its apparatus.

[0002]

2. Description of the Related Art Conventionally, a write-once optical disc (CD-WO) has been used.
As shown in FIG. 2, the recordable optical disc 1 is provided with a spirally formed track 2 which is wavy (meandering) with a slight amplitude in advance in the recording area. The swell of this track is ATIP (Absolute Time In P
It represents absolute time information called regroove data, and has 22.05 KHz as the basic frequency and its frequency is ATI.
Content of bit for each length corresponding to 1 bit of P data (7 cycles of frequency 44.1KHz), that is, this bit is "1"
FSK (Frequency Shift Keying) modulation is performed so as to change ± 1 KHz depending on whether it is 0 or 0.

Further, one frame of ATIP data is
It is composed of a large number of continuous frames consisting of a bit string including a constant (84 bits) of bits and having a fixed pattern of frame synchronization signal at a predetermined position, and each frame is repeated at a frequency of 75 Hz.

On the other hand, when recording information such as audio and video on the above-mentioned recordable optical disc, the number of channels of the song, the presence / absence of pre-emphasis, the song number, the time from the beginning of the song, from the innermost circumference of the disc The control information indicating the absolute time of the subcode data, that is, the subcode data is also recorded at the same time. In this subcode data, one frame has a fixed number of bits (98 bits) (however, the unit length corresponding to one bit is A
(It is different from the case of TIP data) and is composed of a number of frames consisting of a bit string having a fixed pattern frame synchronization signal at a predetermined position, and each frame is recorded at a frequency of 75 Hz.

[0005] Here, when information is actually recorded on an optical disk, the ATIP data and subcode data must be recorded in a frame-synchronous manner according to the standard, so that the ATIP data is reproduced. There is a need. Therefore, when the ATIP data is conventionally reproduced, the above-mentioned undulation is detected and reproduced as an analog signal (wobble signal) having a undulation period, and demodulated by an FSK demodulation circuit using an analog PLL circuit or the like. It was

However, in reproducing the wobble signal,
There were the following problems.

That is, the tracking error signal is the difference between the left and right sides of the return light reflected from the optical disc on the photodetector of the optical pickup. Therefore, when the objective lens moves following the eccentricity of the optical disk, the spot of the returning light naturally moves left and right on the photodetector in the optical pickup. Here, considering the case where the returned light has noise, if the incident light intensities to the respective photodetectors are all at the same level, noise will not be superimposed on the tracking error signal, but the left and right incident light intensity levels , The noise and the EFM signal component are superimposed on the tracking error signal, and C / of the wobble signal WB
It lowers N.

For example, in the above-mentioned write-once type optical disc, there is an area in which information is recorded and an unrecorded area, and when a wobble signal is reproduced in the area in which information is recorded, it is biased to the optical disk. If there is a core, the signal component of the recorded information, that is, the EFM signal component is superimposed on the wobble signal to lower the C / N, the ATIP data cannot be accurately reproduced, and the search is greatly hindered, causing a malfunction. I will end up.

In order to reduce such malfunctions,
For example, in the 1-beam push-pull method, Japanese Patent Laid-Open No. 6-44
The wobble signal is reproduced by the circuit configuration disclosed in Japanese Patent No. 568.

That is, as shown in FIG. 3, the wobble signal reproducing device includes adders 71A and 71B and subtractors 72A and 72A.
B, coupling capacitors 73A to 73C, variable amplifier circuit 7
4, clamp circuits 75A and 75B, peak hold circuits 76A and 76B, an amplifier circuit 77, and a bandpass filter (BPF) 78.

Further, 10 is an optical pickup, and a well-known four-divided photodetector 11 is used as the photodetector 11 for receiving the reflected light from the optical disk. Also, the detector 11 located on the left side of the truck
Voltages V1 and V2 corresponding to the total amount of light received by a and 11d and the total amount of light received by the detectors 11b and 11c located on the right side.
Are generated by the summing amplifiers 71A and 71B.

Here, at the voltages V1 and V2, the light quantity of the reflected light beam from the optical disk changes in accordance with the pits within a predetermined range, and the groove changes in the radial direction of the light beam, so that only a predetermined level is reached. In the biased state, the signal level changes in a short cycle according to the pit, and further the entire signal level changes according to the groove.

On the other hand, the voltage V1 is input to the variable amplifier circuit 74 via the coupling capacitor 73A, and the voltage V2 is supplied as the signal S2 via the coupling capacitor 73B to the clamp circuit 7.
5B and the non-inverting input terminal of the subtracter 72A.

The output signal S from the variable amplifier circuit 74
1 is a clamp circuit 75A via a coupling capacitor 73C
And to the inverting input terminal of the subtractor 72A.

The output signal of the clamp circuit 75A is passed through the peak hold circuit 76A as a signal S3 and the subtracter 72B is operated.
Of the clamp circuit 75B, and the output signal of the clamp circuit 75B is input to the non-inverting input terminal of the subtracter 72B as the signal S4 via the peak hold circuit 76B. Further, the output signal S5 of the subtractor 72B is amplified by the amplifier 77 and then input to the variable amplification circuit 74 as a control signal.

Further, the wobble signal WB is reproduced by passing the output signal of the subtractor 72A through the band pass filter 78.

According to the above configuration, the signal level of the input signal S1 is corrected so that the signal level of the RF component that changes depending on the pit becomes equal between the input signals S1 and S2, and then the difference signal between them is generated. Further, since the wobble signal WB is reproduced, even if the incident position of the reflected light beam on the optical pickup 10 changes due to aging or the like, it is possible to reduce mixing of the RF component into the wobble signal WB.

[0018]

However, the above-mentioned conventional wobble signal reproducing device has a problem that the structure is complicated and the number of parts is increased to increase the cost.

In view of the above problems, it is an object of the present invention to provide a wobble signal reproducing method for an optical disc and a device therefor which can always reproduce an accurate wobble signal with a simple structure.

[0020]

In order to achieve the above-mentioned object, the present invention has, in claim 1, a track formed meandering based on absolute time information, and a pit is formed along the track. The reflected light from the optical disc is detected by using a photodetector which is divided into at least two in the left and right direction of the track, and a wobble signal reproduction of the optical disc which reproduces a wobble signal that changes corresponding to the meandering of the track from the detection result. In the method, a level of a signal output from one photodetector of the two-divided photodetectors is changed based on a control signal, and a difference between the level-changed signal and a level of a signal output from the other photodetector is changed. A difference signal having a level is generated, and based on the EFM signal obtained from the reflected light,
After sample-holding the difference signal, the sample-hold signal is used as the control signal through a low-pass filter,
A wobble signal reproducing method for an optical disc is proposed in which the difference signal is reproduced as a wobble signal through a bandpass filter.

According to the wobble signal reproducing method for the optical disk, the level of the signal output from one photodetector of the two divided photodetectors which receives the reflected light from the optical disk which is the object of recording / reproducing information is controlled by the control signal. The level is changed. Further, a difference signal having a difference level between the level-changed signal level and the level of the signal output from the other photodetector is generated, and the wobble signal is reproduced by passing the difference signal through a bandpass filter. It Here, as the control signal, the difference signal is sampled and held based on the EFM signal obtained from the reflected light from the optical disc, and further generated through a low-pass filter, and the control signal from the one photodetector corresponds to the EFM signal. Since the output signal levels are changed and the offsets of the output signal levels from both photodetectors are made substantially the same level, the noise components of both signals output from the two photodetectors, that is, the EFM that is in-phase in both signals. The signal components are canceled out, and the noise component in the wobble signal is reduced or eliminated.

According to a second aspect of the present invention, there is a track formed in a meandering manner on the basis of absolute time information, and reflected light from an optical disc having pits formed along the track is at least in the lateral direction of the track. In a wobble signal reproducing method for an optical disc, which detects using a photo detector divided into two, and reproduces a wobble signal which changes corresponding to the meandering of the track from the detection result, outputs from both photo detectors of the two photo detectors. The level of the signal to be changed is respectively changed based on the first control signal and the second control signal, and a difference signal having a difference level of the level-changed signal levels is generated, and the EFM signal obtained from the reflected light is generated. After the sampled and held the difference signal based on the Together form a first control signal, the inverting the first control signal a second control signal and none proposes a wobble signal reproducing method of an optical disc for reproducing the sample-and-hold signal as the wobble signal through the band-pass filter.

According to the wobble signal reproducing method for the optical disk, the levels of the signals output from both photodetectors of the two-divided photodetectors that receive the reflected light from the optical disk that is the object of recording and reproducing information are the first and the first. 2 The level is changed by the control signal. Also,
A difference signal having the level difference of the signal level changed is generated, the difference signal is sample-held based on the EFM signal obtained from the reflected light from the optical disc, and the sample-held signal is band-pass filtered. The wobble signal is reproduced by passing through. The first control signal is generated by passing the sampled and held signal through a low pass filter, and the second control signal is generated by inverting the first control signal. Here, the first and second control signals are generated by being sampled and held based on the EFM signal, and the output signal levels from the photodetectors of both are changed according to the EFM signal, and the output from both photodetectors is changed. Since the signal level offsets are set to substantially the same level, the noise components of both signals output from the two photodetectors, that is, the EFM signal components having the same phase in both signals are canceled, and the noise components in the wobble signal are reduced. Alternatively, the level of the wobble signal reproduced can be maintained at a substantially constant level while being removed.

Further, in claim 3, there is a track formed meandering based on the absolute time information, and reflected light from the optical disk having pits formed along the track is at least in the left and right direction of the track. In a wobble signal reproducing apparatus for an optical disc which detects using a photo detector divided into two parts and reproduces a wobble signal which changes corresponding to the meandering of the track from the detection result, the photo detector output from one of the photo detectors divided into two parts. A variable amplifier circuit for changing and outputting the level of a signal to be output based on a control signal; a level of a signal output from the other photodetector of the two-divided photodetector and a level of an output signal of the variable amplifier circuit. A subtraction circuit for outputting a signal having a difference level and reflection from the optical disc A sample and hold circuit that samples and holds the output signal of the subtraction circuit based on the EFM signal obtained from the above, and a low-pass filter that outputs only the frequency component of a predetermined frequency or less in the output signal of the sample and hold circuit as the control signal. And a band filter for inputting the output signal of the subtraction circuit and outputting a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the signal, a wobble signal reproducing apparatus for an optical disc is proposed.

According to the wobble signal reproducing apparatus for the optical disk, the level of the signal output from one photodetector of the two divided photodetectors which receives the reflected light from the optical disk which is the recording / reproducing target of information becomes the control signal. On the basis of the difference signal, the difference signal is changed by the variable amplification circuit based on the differential amplification circuit, and the subtraction circuit generates a difference signal having a difference level between the level of the signal output from the other photodetector of the two divided photodetectors and the level of the output signal of the variable amplification circuit. Is output. Further, only the frequency component below a predetermined frequency in the output signal of the subtraction circuit, that is, the offset component is output as the control signal by the low pass filter. Here, the control signal output from the low-pass filter is an EFM obtained from the reflected light from the optical disc.
The difference signal is sampled and generated based on the signal, and the output signal level from the one photodetector is changed corresponding to the EFM signal. Further, the control signal corresponds to the level difference between the signal output from the variable amplifier circuit and the signal output from the other photodetector only when the EFM signal obtained from the reflected light from the optical disc is present. Since it becomes a signal having a level, the subtractor is controlled by controlling the level of the signal output from the one photodetector to be substantially the same as the level of the signal output from the other photodetector by this control signal. , Both noise components are canceled out, and the noise component in the signal output from the subtractor, that is, the wobble signal is reduced or eliminated. Further, the band-pass filter outputs a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the output signal of the subtraction circuit to reproduce the wobble signal.

According to a fourth aspect of the present invention, a reflected light from an optical disk having a track meandering based on absolute time information and having pits formed along the track is provided at least in the lateral direction of the track. In a wobble signal reproducing apparatus for an optical disc which detects using a photo detector divided into two parts and reproduces a wobble signal which changes corresponding to the meandering of the track from the detection result, the photo detector output from one of the photo detectors divided into two parts. A variable output circuit that changes the level of a signal to be output based on a first control signal and outputs the level of the signal output from the other photodetector of the two-divided photodetector based on a second control signal. And a second variable amplifier circuit for changing and outputting the output signal level, and an output signal level of the first variable amplifier. Wherein a subtraction circuit for outputting a signal having a level difference between the output signal level of the second variable amplifier, EFM obtained from the light reflected from the optical disk and
A sample-hold circuit that samples and holds the output signal of the subtraction circuit based on the signal; a low-pass filter that outputs, as the first control signal, only the frequency component below a predetermined frequency in the output signal of the sample-hold circuit; An inverting circuit that inverts a first control signal and outputs it as the second control signal, and an output signal of the sample and hold circuit are input, and a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the signal is output. We propose a wobble signal reproducing apparatus for an optical disc, which is provided with a bandpass filter.

According to the wobble signal reproducing apparatus for the optical disk, the level of the signal output from one photodetector of the two photodetectors divided into two, which receives the reflected light from the optical disk as the information recording / reproducing target, is the first and the second. A difference signal that is changed by the first and second variable amplifier circuits based on the second control signal and that has a difference level between the output signal levels of the first and second variable amplifier circuits is output by the subtractor circuit. It Further, only the frequency component below the predetermined frequency in the output signal of the subtraction circuit, that is, the offset component is output as the first control signal by the low-pass filter. Here, the first control signal output from the low-pass filter is generated by sample-holding the difference signal based on the EFM signal obtained from the reflected light from the optical disc, and the first control signal corresponds to the EFM signal. The output signal level from the photo detector of is changed. Also, the second control signal is generated by inverting the first control signal by an inverting circuit. Further, the first and second control signals correspond to the difference between the signal levels output from the first and second variable amplifier circuits only when the EFM signal obtained from the reflected light from the optical disc is present. Since the signals have the same level, the control signals control the levels of the signals output from the photodetectors to be substantially the same, so that both noise components are canceled in the subtractor, and the subtraction is performed. It is possible to reduce or remove the noise component in the signal output from the device, that is, the wobble signal, and maintain the level of the reproduced wobble signal at a substantially constant level. Further, the band-pass filter outputs a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the output signal of the sample hold circuit to reproduce the wobble signal.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In the figure, the same components as those of the above-described conventional example are denoted by the same reference numerals. That is, 10 is an optical pickup using the one-beam push-pull method, 21, 22
Is a summing amplifier, 23 is an adder, 24 is a subtractor, 31 is a variable amplifier circuit, 32 is a subtractor, 33 is an electronic switch, 34
Is a low pass filter (LPF), 35 is a band pass filter (BPF), and 36 is a hold capacitor.

The optical pickup 10 is provided with a well-known 4-divided photodetector 11, and tracking correction is performed by using the total received light amount of the detectors 11a and 11d located on the left side of the track and the total received light amount of the detectors 11b and 11c located on the right side of the track. , And the total amount of light received by the detectors 11a and 11c located on the diagonal line and the detectors 11b and 1c.
Focus correction can be performed by the astigmatism method or the like using the total received light amount of 1d.

The summing amplifier 21 inputs the voltages output from the photodetectors 11a and 11d of the optical pickup 10 and outputs a voltage V1 obtained by adding them, and the summing amplifier 22 outputs the photodetectors 11b and 11b of the optical pickup 10.
11c, and outputs a voltage V2 obtained by adding them.

The voltages V1 and V2 are input to the adder 23, which are added by the adder 23 and output as a read signal (RF signal).
The difference voltage V3 is generated by the subtractor 24, and this voltage V3
3 is output as the tracking error signal TE.

Further, the voltage V1 output from the summing amplifier 21 is supplied to the variable amplifier circuit 3 via the coupling capacitor C1.
1 is input to the control voltage V by the variable amplifier circuit 31.
The voltage value is input to the subtractor 32 as the voltage V4 whose voltage value is changed to a predetermined value based on con. The voltage V4 is input to the non-inverting input terminal of the subtractor 32, and the voltage V2 is input to the inverting input terminal via the coupling capacitor C2.
Outputs these differences as a difference signal V5. The difference signal V5 is input to the first contact 33a of the electronic switch 33 and the band pass filter 35.

The second contact 33b of the electronic switch 33 is opened, and the contact piece 33c is connected to the input terminal of the low-pass filter 34 and grounded via the hold capacitor 36. Further, the electronic switch 33 is switched by the EFM signal reproduced from the RF signal,
When the signal is at high level, the contact piece 33c is connected to the first contact 33a.
, And the contact piece 33c is connected to the second contact 33b when the level is low.

Here, the electronic switch 33 and the hold capacitor 36 constitute a sample hold circuit.

When the difference signal V5 is input to the low-pass filter 42 through the electronic switch 33, the low-pass filter 34 causes the difference signal V5 to have a predetermined frequency, for example, 4
Only the frequency component of 0 KHz or less is extracted and output as the above-mentioned control voltage Vcon.

On the other hand, the difference signal V5 input to the bandpass filter 35 is a frequency component within a predetermined frequency band by the bandpass filter 35, that is, a frequency within a predetermined frequency band centering on the frequency 22.05 KHz of the wobble signal. Only the component is extracted and output as the wobble signal WB.

Next, the operation of this embodiment having the above-mentioned configuration will be described based on the signal waveform diagram of FIG. When information is recorded on the optical disk, that is, when a track in which pits are formed is reproduced, the RF signal becomes that modulated by the EFM signal. Therefore, from the RF signal to EF
The M signal can be reproduced.

However, the voltages V1 and V2 required for reproducing the wobble signal are mixed with the EFM signal, and the levels of the voltages V1 and V2 are different. Here, in the present embodiment, the voltage V1 is corrected by the variable amplifier circuit 31 so that the EFM signal components mixed in the voltages V1 and V2 become equal.
4 is generated and the difference signal V5 between the voltage V4 and the voltage V2 is further generated by the subtractor 32.
A voltage V5 in which no component is mixed is obtained, and the wobble signal is reproduced from this voltage V5.

In correcting the voltage V1 in the variable amplifier 31, the difference signal V5 is input to the low-pass filter 34 only when the EFM signal is at the high level H, and the low-pass filter 34 causes the envelope component of the difference signal V5, that is, EF.
The M signal component is extracted, and this is used as a control voltage Vcon to correct the voltage V1.

Therefore, as shown in FIG. 4, the level of the voltage V4 is almost the same as the level of the voltage V2, so that the noise component and the EFM signal component of the voltage V4 and the noise component and the EFM signal component of the voltage V2 are generated. A wobble signal WB that is canceled and the noise component and the EFM signal component are reduced or removed is generated.

Here, in the signal waveform shown in FIG. 4, since the control voltage Vcon is positive, the variable amplifier circuit 31 operates to decrease the gain, and when the voltage V4 is smaller than the voltage V2, the control voltage Vcon becomes negative. Therefore, the variable amplifier circuit 31 operates to increase the gain.

As described above, according to this embodiment, the accurate wobble signal WB can be always reproduced with a simple structure, so that spindle control, particularly spindle control at the time of tracking off, can be stably performed. Furthermore, since the AITP data can be accurately reproduced even if the optical disk has eccentricity or skew (SKEW), search errors can be significantly reduced. Further, even if the optical pickup changes with time or the characteristics of the optical disc medium change, the servo can always be automatically applied to the best point of C / N.

Next, a second embodiment of the present invention will be described. FIG. 5 is a configuration diagram showing a second embodiment of the present invention. In the figure, the same components as those of the above-described conventional example are denoted by the same reference numerals. That is, 10 is an optical pickup using the 1-beam push-pull method, 21 and 22 are summing amplifiers,
23 is an adder, 24 is a subtractor, 41A and 41B are variable amplification circuits, 42 is a subtractor, 43 is an electronic switch, 44 is a hold capacitor, 45 is a differential amplifier, 46 is a low-pass filter (LPF), and 47 is inverting. The amplifier 48 is a bandpass filter (BPF).

The optical pickup 10 is provided with a well-known four-divided photodetector 11, and tracking correction is performed by using the total received light amount of the detectors 11a and 11d located on the left side of the track and the total received light amount of the detectors 11b and 11c located on the right side of the track. , And the total amount of light received by the detectors 11a and 11c located on the diagonal line and the detectors 11b and 1c.
Focus correction can be performed by the astigmatism method or the like using the total received light amount of 1d.

The summing amplifier 21 inputs the voltages output from the photodetectors 11a and 11d of the optical pickup 10 and outputs a voltage V1 obtained by adding these, and the summing amplifier 22 outputs the photodetectors 11b and 11b of the optical pickup 10.
11c, and outputs a voltage V2 obtained by adding them.

The voltages V1 and V2 are input to the adder 23, which are added by the adder 23 and output as a read signal (RF signal).
The difference voltage V3 is generated by the subtractor 24, and this voltage V3
3 is output as the tracking error signal TE.

Further, the voltage V1 output from the summing amplifier 21 is supplied to the variable amplifier circuit 4 via the coupling capacitor C1.
The voltage V which is input to 1A and whose voltage value is changed to a predetermined value based on the control voltage Vcon1 by the variable amplifier circuit 41A.
It is input to the non-inverting input terminal of the subtractor 42 as a.

Further, the voltage V2 output from the adder 22
Is input to the variable amplifier 41B via the coupling capacitor C2, and is input to the inverting input terminal of the subtractor 42 as the voltage Vb whose voltage value has been changed to a predetermined value by the variable amplifier 41B based on the control voltage Vcon2.

The subtractor 42 outputs the difference between the input voltages Va and Vb as a difference signal Vc. The difference signal Vc is input to the first contact 43a of the electronic switch 43 and the input terminal of the bandpass filter 48.

The second contact 43b of the electronic switch 43 is opened, and the contact piece 43c is connected to the non-inverting input terminal of the differential amplifier 45 and grounded via the hold capacitor 44. Further, the electronic switch 43 is switched by the EFM signal reproduced from the RF signal,
When the signal is high level, the contact piece 43c is connected to the first contact 43a.
, And the contact piece 43c is connected to the second contact 43b when the level is low.

The output terminal of the differential amplifier 45 is connected to its inverting input terminal and also to the input terminal of the low pass filter 46.

Here, the electronic switch 43, the hold capacitor 44 and the differential amplifier 45 constitute a sample hold circuit.

When the hold signal Vd output from the differential amplifier 45 is input to the low-pass filter 46, the low-pass filter 46 extracts only a frequency component of a predetermined frequency, for example, 40 KHz or less from the hold signal Vd, and Is output as the control voltage Vcon1.

Further, the control voltage Vcon1 is supplied to the inverting amplifier circuit 4
The sign is inverted by 7 and is output as the control voltage Vcon2.

On the other hand, the difference signal Vc input to the bandpass filter 48 is a frequency component within a predetermined frequency band by the bandpass filter 48, that is, a frequency within a predetermined frequency band centering on the frequency 22.05 KHz of the wobble signal. Only the component is extracted and output as the wobble signal WB.

According to the second embodiment having the above-mentioned structure, when a track on which information is recorded on the optical disk, that is, a pit is reproduced, its RF signal is considered to be modulated by the EFM signal. Become. Therefore, R
The EFM signal can be reproduced from the F signal.

However, the voltages V1 and V2 required for reproducing the wobble signal are mixed with the EFM signal, and the levels of the voltages V1 and V2 are different.

Here, in the present embodiment, these voltages V
Variable amplifier circuits 41A and 41B generate voltages Va and Vb in which the levels of voltages V1 and V2 are corrected so that the EFM signal components mixed in 1 and V2 become equal and a voltage level equal to or higher than a predetermined value is obtained. This voltage Va, V
By generating the difference signal Vc of b by the subtractor 42, the hold signal Vd in which the EFM component is not mixed is obtained,
A wobble signal is reproduced from this hold signal Vd.

Voltage V in variable amplifiers 41A and 41B
In the correction of 1 and V2, the difference signal Vc is sampled and held only when the EFM signal is at the high level H, the envelope component of the hold signal Vd, that is, the EFM signal component is extracted by the low-pass filter 46, and this is controlled by the control voltage. Vco
The voltage V1 is corrected as n1. Furthermore, the control voltage V
By inverting con1 to obtain the control voltage Vcon2 and correcting the voltage V2 by this, the variable amplifier circuits 41A and 41A
B is in push-pull operation. As a result, the wobble signal can always be reproduced at an optimum constant level.

Therefore, the level of the voltage Va is made substantially the same as the level of the voltage Vb, so that the noise component and EFM signal component of the voltage Va and the noise component and EF of the voltage Vb are obtained.
The wobble signal WB in which the M signal component is canceled and the noise component and the EFM signal component are reduced or removed is generated.

As described above, according to the present embodiment, the wobble signal WB having an accurate and optimum level can always be reproduced with a simple structure, so that spindle control, particularly spindle control at the time of tracking off, can be stably performed. You can Furthermore, eccentricity or skew (S
Since the AITP data can be accurately reproduced even if the KEW) occurs, search errors can be significantly reduced. Further, even if the optical pickup changes with time or the characteristics of the optical disc medium change, the servo can always be automatically applied to the best point of C / N.

It is needless to say that the configurations of the first and second embodiments described above are examples, and the present invention is not limited to this.

[0063]

As described above, according to the wobble signal reproducing method for the optical disk of the first aspect of the present invention, the EF
In synchronization with the M signal, the noise components of both signals output from the two photo detectors, that is, the EFM signal components are canceled and the noise components in the wobble signal are reduced or eliminated, so that an accurate wobble signal can always be reproduced. ,
Spindle control, especially spindle control at the time of tracking off, can be stably performed, and AITP data can be accurately reproduced even if eccentricity or SKEW occurs on the optical disc, and search mistakes can be greatly reduced. You can Further, even if the optical pickup changes with time or the characteristics of the optical disc medium change, the servo can always be automatically applied to the best point of C / N.

According to the wobble signal reproducing method of the optical disc of the second aspect, the noise component of both signals output from the two photodetectors, that is, the EFM signal component is canceled in synchronization with the EFM signal, and the wobble signal is generated. Since the noise component in the signal is reduced or removed, the wobble signal of an accurate optimum level can always be reproduced, the spindle control, particularly the spindle control at the time of tracking off, can be stably performed, and the eccentricity or SKEW on the optical disk can be performed. Even if the error occurs, the AITP data can be accurately reproduced, and the search error can be greatly reduced. Further, even if the optical pickup changes with time or the characteristics of the optical disc medium change, the servo can always be automatically applied to the best point of C / N.

According to the wobble signal reproducing apparatus for an optical disc of the third aspect, the offset component of the wobble signal, that is, E is synchronized with the EFM signal with a simple structure.
The FM signal component is used as a control signal, and the level of the signal output from one photodetector of the photodetectors divided into two in the left and right direction of the track by the control signal becomes substantially the same as the level of the signal output from the other photodetector. Since the noise components superimposed on both signals are canceled by the subtracter, the noise components in the wobble signal can be reduced or removed. As a result, an accurate wobble signal can always be reproduced, so that spindle control, particularly spindle control at the time of tracking off, can be stably performed. further,
AIT even if eccentricity or SKEW occurs on the optical disc
Since P data can be reproduced accurately, search errors can be greatly reduced. Further, even if the optical pickup changes with time or the characteristics of the optical disc medium change, the servo can always be automatically applied to the best point of C / N.

According to the wobble signal reproducing apparatus for an optical disc of the fourth aspect, the offset component of the wobble signal, that is, E is synchronized with the EFM signal with a simple structure.
The FM signal component is used as a control signal, and the level of the signal output from both photodetectors of the photodetectors divided into two in the left and right direction of the track is controlled by the control signal to be substantially the same, and the subtractor subtracts both signals. Since the noise component superposed on is canceled, the noise component in the wobble signal can be reduced or removed. As a result, the wobble signal of the optimum level can always be reproduced accurately, so that spindle control, particularly spindle control at the time of tracking off, can be stably performed. Furthermore, since the AITP data can be accurately reproduced even if the optical disk is eccentric or SKEW, search errors can be greatly reduced. Further, even if the optical pickup is changed with time or the characteristics of the optical disk medium is changed, it is possible to automatically apply the servo to the best point of C / N.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a view for explaining tracks formed on an optical disk;

FIG. 3 is a configuration diagram showing a conventional example.

FIG. 4 is a signal waveform diagram explaining the operation of the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

[Explanation of symbols]

10 ... Optical pickup, 11a-11d ... Photo detector, 21, 22 ... Summing amplifier, 23 ... Adder, 24 ...
Subtractor, 31 ... Variable amplifier circuit, 32 ... Subtractor, 33 ... Electronic switch, 34 ... Low pass filter, 35 ... Band pass filter, 41A, 41B ... Variable amplifier, 42 ... Subtractor, 43 ... Electronic switch, 44 ... Hold Capacitors,
45 ... Differential amplifier, 46 ... Low pass filter, 47 ... Inversion amplifier, 48 ... Band pass filter.

Claims (4)

[Claims] 1. A photodetector having a track formed in a meandering manner based on absolute time information, and reflecting light from an optical disk having pits formed along the track is at least divided into two in the left-right direction of the track. In the wobble signal reproducing method for an optical disc, the level of a signal output from one of the photodetectors divided into two is detected by using a wobble signal reproducing method that reproduces a wobble signal that changes corresponding to the meandering of the track from the detection result. Based on the EFM signal obtained from the reflected light, a difference signal having a level of a difference between the level-changed signal and the level of the signal output from the other photodetector is generated. Sample and hold the difference signal, and then pass the sample and hold signal through a low pass filter. It said control signal and without wobble signal reproducing method of the optical disc, characterized in that for reproducing the difference signal as the wobble signal through the bandpass filter Te. 2. A photodetector having a track formed in a meandering manner based on absolute time information, and reflecting light from an optical disc having pits formed along the track is at least divided into two in the left-right direction of the track. In the wobble signal reproducing method for an optical disc, which reproduces a wobble signal that changes corresponding to the meandering of the track based on the detection result, and a level of a signal output from both photo detectors of the two divided photo detectors. Respectively on the basis of the first control signal and the second control signal to generate a difference signal having a level difference of the level-changed signal levels, and based on the EFM signal obtained from the reflected light, After sample-holding the difference signal, the sample-hold signal is passed through the low-pass filter to the first control signal. Together form a said inverts the first control signal a second control signal and without wobble signal reproducing method of the optical disc, characterized in that for reproducing the sample-and-hold signal as the wobble signal through the band-pass filter. 3. A photodetector having a track formed in a meandering manner based on absolute time information, and reflecting light from an optical disk having pits formed along the track is at least divided into two in the left-right direction of the track. In the wobble signal reproducing apparatus of the optical disc for detecting a wobble signal which changes according to the meandering of the track based on the detection result, the level of the signal output from one photodetector of the two divided photodetectors. And a variable amplifier circuit that outputs the variable amplifier circuit based on a control signal, and a level of a difference between a level of a signal output from the other photodetector of the two-divided photodetector and a level of an output signal of the variable amplifier circuit. A subtraction circuit for outputting a signal, and an EF obtained from the reflected light from the optical disc A sample-hold circuit that samples and holds the output signal of the subtraction circuit based on the M signal; a low-pass filter that outputs only a frequency component below a predetermined frequency in the output signal of the sample-hold circuit as the control signal; A wobble signal reproducing apparatus for an optical disc, comprising: a band filter for inputting an output signal of the circuit and outputting a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the signal. 4. A photodetector having a track formed in a meandering manner based on absolute time information, and reflecting light from an optical disk having pits formed along the track is at least divided into two in the left-right direction of the track. In the wobble signal reproducing apparatus of the optical disc for detecting a wobble signal which changes according to the meandering of the track based on the detection result, the level of the signal output from one photodetector of the two divided photodetectors. And a first variable amplifier circuit for changing and outputting based on a first control signal, and a level of a signal output from the other photodetector of the two-divided photodetector is changed and output based on a second control signal. A second variable amplifier circuit for controlling the output signal level of the first variable amplifier and the second variable amplifier circuit. A subtraction circuit that outputs a signal having a level of difference from the output signal level of the amplification circuit, and a sample hold circuit that samples and holds the output signal of the subtraction circuit based on the EFM signal obtained from the reflected light from the optical disc. A low-pass filter that outputs only a frequency component of a predetermined frequency or lower in the output signal of the sample hold circuit as the first control signal; and an inverting circuit that inverts the first control signal and outputs the second control signal. And a band filter for inputting the output signal of the sample-hold circuit and outputting a signal having a frequency within a predetermined frequency band including the frequency of the wobble signal in the signal, a wobble signal reproducing apparatus for an optical disc. .