JPH06187649A - Method and its device for regenerating wobble signal in optical disk - Google Patents

Abstract

PURPOSE:To obtain a method for generating a wobble signal in an optical disk capable of regenerating always a correct wobble signal, and its device. CONSTITUTION:The level of one voltage V1 between voltages V1, V2 corresponding to received light quantities bisected in a left and right direction in a track is changed basing on a controlled voltage Vcon by a gain variable circuit 30. The difference between a voltage V4 obtained by such a manner and the voltage V2 is generated by a subtracter 41 to be a wobble signal WB. The controlled voltage Vcon is generated by making the wobble signal pass through a low-pass filter 42. Thus, a spindle control, especially the spindle control at the time of a tracking-off is performed stablly since a correct wobble signal WB is always regenerated. Furthermore, a search-miss is remarkably reduced since AITP data are regenerated correctly even when the eccentricity or a skew generated in the optical disk.

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 disk and its apparatus.

[0002]

2. Description of the Related Art Conventionally, a write-once optical disc (CD-W
O), a recordable optical disc 1 such as a magneto-optical disc (CD-MO), as shown in FIG. 2, has a track 2 which is prewound (meandering) with a slight amplitude in its recording area in advance.
Is formed in a spiral shape. The swell of this track expresses absolute time information called ATIP (Absolute Time In Pregroove) data, and has 22.05 KHz as a basic frequency, and the frequency is the length corresponding to 1 bit of ATIP data (frequency of 44.1 KHz). FSK (Frequent) so that it changes ± 1 KHz depending on the content of the bit every 7 cycles), that is, whether this bit is “1” or “0”.
ency Shift Keying) Modulated.

Further, one frame of ATIP data is
The frame is composed of a large number of consecutive frames each including a constant number (84 bits) of bits and having a fixed pattern 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.

When the information is actually recorded on the optical disk, the standard defines that the ATIP data and the subcode data should be recorded in frame synchronization. Therefore, 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

For example, the one-beam push-pull method is shown in FIG.
The wobble signal was reproduced with the circuit configuration shown in.

That is, in FIG. 3, 10 is an optical pickup, and as a photodetector 11 for receiving the reflected light from the optical disk, a well-known four-division photodetector 1 is used.
1 is used. Further, the voltages V1 and V2 corresponding to the total amount of received light of the detectors 11a and 11d located on the left side of the track and the total amount of received light of the detectors 11b and 11c located on the right side are generated by the summing amplifiers 21 and 22, respectively. , V2 is the read signal (RF
The signal) is output from the adder 23. Further, the voltage V3, which is the difference between the voltages V1 and V2, is generated by the subtractor 24,
This voltage V3 is output as the tracking error signal TE. Furthermore, the voltage V3 of the tracking error signal TE is passed through the band pass filter 25 to reproduce the wobble signal WB.

[0008]

However, the above-mentioned conventional wobble signal reproducing device has the following problems.

That is, the tracking error signal TE is the difference between the left and right of the return light reflected from the optical disc on the photodetector of the optical pickup 10. Therefore, when the objective lens moves following the eccentricity of the optical disc, the spot of the returning light naturally moves left and right on the photodetector in the optical pickup 10. Here, considering the case where the return light has noise, if the incident light intensities to the photodetectors 11a to 11d are all at the same level, noise will not be superimposed on the tracking error signal TE, but the left and right incidents will not occur. When the light intensity level is different (the voltage V1 level is different from the voltage V2 level),
Noise is superimposed on the tracking error signal TE, and the C / N of the wobble signal WB is reduced.

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 an area in which information is recorded, it is biased to the optical disk. If there is a core, etc., the signal component of the recorded information is superimposed on the wobble signal to lower the C / N,
The ATIP data cannot be accurately reproduced, which greatly hinders the search and causes a malfunction.

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 an apparatus thereof which can always reproduce an accurate wobble signal.

[0012]

In order to achieve the above object, the present invention provides, in claim 1, at least the reflected light from an optical disk having a track meandering based on absolute time information. In the wobble signal reproducing method for an optical disc, the wobble signal is detected by using a photodetector that is divided into two in the left-right direction, and a wobble signal that changes corresponding to the meandering of the track is reproduced from the detection result.
Changing the level of the signal output from the one photodetector so that the level of the signal output from one photodetector of the two divided photodetectors becomes equal to the level of the signal output from the other photodetector; A wobble signal reproducing method for an optical disc is proposed, in which a signal having a difference level between the signal level and the level of the signal output from the other photodetector of the two-divided photodetector is generated and used as the wobble signal.

According to a second aspect of the present invention, the reflected light from the optical disk having the track meandering based on the absolute time information is detected by using a photodetector which is divided into at least two lateral directions of the track, and the reflected light is detected. In a wobble signal reproducing apparatus for an optical disc that reproduces a wobble signal that changes corresponding 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 is changed based on a control signal. And a subtraction circuit for outputting a signal having a level of a difference between the level of the signal output from the other photodetector of the photodetector divided into two and the level of the output signal of the gain variable circuit. , Of the frequency component below the predetermined frequency in the output signal of the subtraction circuit The propose wobble signal reproducing apparatus of an optical disk that includes a low pass filter for outputting as said control signal.

[0014]

According to the first aspect of the present invention, the level of the signal output from one photodetector of the two split photodetectors that receives the reflected light from the optical disc that is the object of information recording / reproduction is from the other photodetector. The level of the signal output from the one photodetector is changed so as to be equal to the level of the output signal, and the level of the signal and the level of the signal output from the other photodetector of the two-divided photodetector are changed. A signal having a difference level of is generated and used as a wobble signal. As a result, the noise components of both signals output from the two photodetectors are canceled out, and the noise components in the wobble signal are reduced or eliminated.

According to a second aspect of the present invention, the level of the signal output from one photodetector of the two photodetectors divided into two that receives the reflected light from the optical disc that is the object of recording and reproducing information is based on the control signal. A signal having a level that is changed by the gain variable circuit and has 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 gain variable circuit is output by the subtraction circuit. . 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, since the control signal output from the low-pass filter has a level corresponding to the level difference between the signal output from the gain variable circuit and the signal output from the other photodetector, this control is performed. By controlling the level of the signal output from the one photodetector by the signal to be approximately the same as the level of the signal output from the other photodetector, both noise components are canceled in the subtractor, and The noise component in the signal output from the subtractor, that is, the wobble signal is reduced or removed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, the same components as those in the conventional example described above are represented 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, and 23
Is an adder, 24 is a subtractor, 30 is a variable gain circuit, 41
Is a subtracter, and 42 is a low-pass filter.

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.
The voltage output from 11c is input and a voltage V2 obtained by adding these is output. In addition, the adders 23 have voltages V1 and V
2 is input, these are added by the adder 23 and output as a read signal (RF signal), and the voltage V
The voltage V3, which is the difference between 1 and V2, is generated by the subtractor 24, and this voltage V3 is output as the tracking error signal TE. Further, the voltage V1 output from the summing amplifier 21
Is input to the subtractor 41 as the voltage V4 whose voltage value has been changed to a predetermined value by the variable gain circuit 30. The subtractor 41 inputs the voltage V4 and the voltage V2 and outputs the difference between them as a wobble signal WB. Further, the voltage value of the voltage V4 output from the variable gain circuit 30 is changed based on the control voltage Vcon obtained by passing the wobble signal WB through the low pass filter 42.

That is, the variable gain circuit 30 includes a triangular wave generator 31, an adder 32, a comparator 33, an electronic switch 34,
It is composed of a low-pass filter 35, and the voltage V1 is input to the first contact 34a of the electronic switch 34. further,
The second contact 34b of the electronic switch 34 is grounded, and the contact piece 34c is connected to the input terminal of the low-pass filter 35. The electronic switch 34 is switched by the control voltage Vse output from the comparator 33,
When se is high level, the contact piece 34c is connected to the second contact 34b, and when se is low level, the contact piece 34c is connected to the first contact point 3b.
4a.

On the other hand, the subtractor 41 inputs the voltage V4 and the voltage V2, and outputs the voltage of the difference between the voltage V4 and the voltage V2 as the wobble signal WB. The wobble signal WB is input to the low-pass filter 42 and has a predetermined frequency, for example 40K.
Only frequency components below Hz are extracted and output as the control voltage Vcon described above.

As a result, as shown in FIG. 4, the control voltage Vcon output from the low-pass filter 42 is added to the triangular wave voltage Va output from the triangular wave generator 31 by the adder 32, and the comparator 33 as the voltage Vb. It is input to the non-inverting input terminal of. The voltage Vb is compared with a predetermined threshold voltage Vth by the comparator 33, and the control voltage Vse output from the comparator 33 is obtained by comparing the voltage Vb with the threshold voltage Vth.
It becomes high level when it is larger, and becomes low level when the voltage Vb is equal to or lower than the threshold voltage Vth.

Here, the frequency of the triangular wave voltage Va output from the triangular wave generator 31 is set to 10 times or more the signal frequency included in the voltage V1. As a result, the pulse width of the control voltage Vse is changed according to the level of the control voltage Vcon, and the electronic switch 34 is correspondingly changed.
Are switched, and the voltage Vc input to the low-pass filter 35 is the voltage V1 which is intermittent. The high-pass component of the voltage Vc is removed by the low-pass filter 35, the output voltage V4 thereof is smoothed, and its level changes in accordance with the pulse width of the control voltage Vse. Therefore,
As shown in FIG. 5, since the level of the voltage V4 is almost the same as the level of the voltage V2, the noise component N of the voltage V4 is
1 and the noise component N2 of the voltage V2 are cancelled, and the wobble signal WB in which the noise component is reduced or removed is generated.

That is, assuming that the outputs of the photodetectors 11a to 11d are A, B, C, and D, and noise is mixed in the outputs of the photodetectors 11a to 11d, the component of the voltage V1 becomes (A + D + n1), and the voltage V1 becomes The component of V2 is (B + C + n2). Where n1,
n2 is a noise component, these are in phase, and the level of n1 is proportional to (A + D) and the level of n2 is (B +
Proportional to C). Therefore, by controlling the level of the voltage V1 so that the noise components n1 and n2 cancel each other, the wobble signal WB from which the noise component is removed can be reproduced.

As described above, according to this embodiment, since the accurate wobble signal WB can be reproduced at all times, the spindle control, particularly the 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.

The configuration in this embodiment is an example,
It goes without saying that the present invention is not limited to this.

[0026]

As described above, according to claim 1 of the present invention, the noise components of both signals output from the two photodetectors are canceled and the noise components in the wobble signal are reduced or eliminated. An accurate wobble signal can always be reproduced, spindle control, particularly 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 disk. Therefore, search mistakes can be significantly reduced.

According to a second aspect of the present invention, the offset component of the wobble signal is used as a control signal, and the level of the signal output from one photodetector of the photodetectors divided in the left and right direction of the track by the control signal is set to the other level. Since the noise component superimposed on both signals is canceled by the subtracter, the noise component in the wobble signal should be reduced or removed. You can 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. Furthermore, even if eccentricity or SKEW occurs on the optical disc, A
Since the ITP data can be reproduced accurately, the search error can be greatly reduced, which is a very excellent effect.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating tracks formed on an optical disc.

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

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

FIG. 5 is a diagram for explaining the operation of the embodiment of the present invention.

[Explanation of symbols]

10 ... Optical pickup, 11a-11d ... Photo detector, 21, 22 ... Summing amplifier, 23 ... Adder, 24 ...
Subtractor, 30 ... Gain variable circuit 31 ... Triangle wave generator, 3
2 ... Adder, 33 ... Comparator, 34 ... Electronic switch, 35
... low-pass filter, 41 ... subtractor, 42 ... low-pass filter.

Claims (2)

[Claims] 1. Reflected light from an optical disc having a track formed in a meandering manner based on absolute time information is detected using at least a photodetector divided into two in the left-right direction of the track, and the track is detected from the detection result. In the wobble signal reproducing method for an optical disc, which reproduces a wobble signal that changes in accordance with the meandering, the level of the signal output from one photodetector of the two divided photodetectors becomes the level of the signal output from the other photodetector. A signal having the level of the difference between the level of the signal output from the one photodetector and the level of the signal output from the other photodetector of the two-divided photodetector is changed to be equal. To generate the wobble signal, Wobble signal reproduction method of an optical disk according to symptoms. 2. Reflected light from an optical disc having a track formed in a meandering manner based on absolute time information is detected by using a photodetector divided into at least two lateral directions of the track, and the track is detected from the detection result. In a wobble signal reproducing apparatus for an optical disc that reproduces a wobble signal that changes in accordance with the meandering, a gain that changes and outputs the level of a signal output from one photodetector of the two divided photodetectors based on a control signal. A variable circuit, a subtraction circuit that outputs a signal having 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 gain variable circuit, and a subtraction circuit of the subtraction circuit. Only the frequency component below a predetermined frequency in the output signal is used as the control signal. A wobble signal reproducing device for an optical disc, comprising: