JP2001167442A - Cross talk removing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain more accurate reproduced signals by generating a cross talk signal while considering an error in the servo system of a reader and removing a cross talk component caused by the error of the servo system from main track signal. SOLUTION: The device is provided with a coefficient computing section 31 which determines and outputs a coefficient value in accordance with the magnitude of a focus error signal caused by focus deviation, a cross talk signal 1 generating section 32 which generates first and second cross talk signals using the coefficient value given by the section 31 from the track signals of both sides adjacent to a main track, a cross talk signal 2 generating section 33 and a differential computing circuit 35 which subtracts the sum of the first and the second cross talk signals from the main track signals and outputs reproduced signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a DVD (digital
The present invention relates to a crosstalk removing apparatus that is used in an optical information reproducing apparatus using an optical disc such as a video disc and removes a crosstalk signal in consideration of a change in a crosstalk component due to an error in a reading optical servo system.

[0002]

2. Description of the Related Art Conventionally, in an optical disk, when the recording density is increased, if the track pitch is made smaller than the spot of the light beam, the peripheral portion of the spot is caught by a recording mark of an adjacent track. Noise, that is, so-called crosstalk, occurs due to mixing of reflected light from recording marks existing in the recording mark. That is, it is important to suppress the crosstalk noise because the recording density becomes high, and the crosstalk canceller (crosstalk canceller) is required.
) Is known.

For example, in order to cancel the above-mentioned crosstalk, a signal of a main track is read, and signals obtained by irradiating sub-beams on tracks adjacent to both sides of the main track are respectively multiplied by a certain coefficient. There is a method of generating a talk signal and reducing a crosstalk component from a main track signal. An apparatus for generating a crosstalk signal using a certain coefficient by which a signal obtained by irradiating the sub-beam is multiplied is disclosed in, for example, JP-A-6-25 / 1994.
No. 9776, Japanese Unexamined Patent Application Publication No. 10-222846, and Japanese Unexamined Patent Application Publication No. 7-334931.

That is, in Japanese Patent Application Laid-Open No. 6-259776, "a crosstalk reducing apparatus for an optical information reproducing apparatus", the gain of a variable gain amplifier circuit is controlled according to whether a signal in a track is a mark or a space. By doing so, crosstalk is eliminated. Also, Japanese Patent Application Laid-Open No. 10-22
In the "Recording Medium Reproducing Apparatus" of Japanese Patent No. 2846, the level of the crosstalk signal is corrected depending on whether the signal in the track is a pit or a mirror. Also, Japanese Patent Application Laid-Open
In the “crosstalk removing device” of JP-A-3344931, after reading a signal with one optical system and giving a delay of two tracks to generate a signal of an adjacent track in a pseudo manner,
The calculation by the filter is performed to reduce the crosstalk component from the main track signal.

[0005]

However, in the conventional apparatus as described above, errors in the servo system (focus error, tracking error, and tilt error) in the actual reading device with respect to the ideal optical position.
Is not taken into account, the crosstalk component from the adjacent first track and second track cannot be removed due to the error remaining in the servo system in the main track being read, and the crosstalk component is not included in the main track signal. There is a problem in that an accurate reproduced signal cannot be obtained due to the presence of a component.

The present invention has been made in view of the above, and generates a crosstalk signal in consideration of an error of a servo system in a reading device, so that a crosstalk component caused by the error of the servo system can be converted into a main track signal. To obtain a more accurate reproduction signal.

[0007]

According to a first aspect of the present invention, there is provided a crosstalk removing apparatus comprising: a main track signal of a main track to be reproduced;
In a crosstalk removing device for removing a crosstalk signal from both tracks adjacent to the main track,
A coefficient output means for determining and outputting a coefficient value corresponding to the magnitude of a focus error signal due to a focus shift, and the coefficient value given by the coefficient output means from each track signal on both sides adjacent to the main track. A crosstalk signal generating means for generating first and second crosstalk signals, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduced signal; It is provided with.

According to the present invention, the coefficient value is increased when the crosstalk component due to an error (focus error) of the focus servo system is the largest, and the coefficient value is decreased when the crosstalk component is the least. Such a characteristic is given to the crosstalk signal generation means, a first crosstalk signal is generated from the first adjacent track signal and the coefficient value, and a second crosstalk signal is generated from the second adjacent track signal and the coefficient value. Is generated, the sum of the two generated crosstalk signals is subtracted from the main track signal, and a reproduced signal from which a crosstalk component is removed is output.
It is possible to obtain a crosstalk signal in which a change in a crosstalk component due to an error in the focus servo system is considered.

Further, in the crosstalk removing apparatus according to the present invention, a crosstalk signal is removed from a main track signal of a main track to be reproduced from a track on both sides adjacent to the main track. In the removing device, a coefficient value corresponding to the magnitude of a tracking error signal due to a tracking shift is determined and output by a coefficient output unit, and the coefficient output unit is provided by the coefficient output unit from each track signal on both sides adjacent to the main track. A crosstalk signal generating means for generating first and second crosstalk signals using a coefficient value; and subtracting a sum of the first and second crosstalk signals from the main track signal to output a reproduction signal. Output means.

According to the present invention, when the crosstalk component of one adjacent track is the largest (small) and the crosstalk component of the other adjacent track is small (many) due to an error (tracking error) of the tracking servo system, A characteristic is given to the crosstalk signal generating means such that the coefficient of one adjacent track is maximum (minimum) and the coefficient of the other adjacent track is minimum (maximum), and a crosstalk signal of each adjacent track is generated. The generated 2
By subtracting the sum of the two crosstalk signals from the main track signal and outputting the reproduced signal with the crosstalk component removed, it is possible to obtain a crosstalk signal that takes into account the change in the crosstalk component due to errors in the tracking servo system. Becomes

According to a third aspect of the present invention, there is provided a crosstalk removing apparatus for removing, from a main track signal of a main track to be reproduced, crosstalk signals from tracks on both sides adjacent to the main track. In the removing apparatus, a coefficient value corresponding to the magnitude of a tilt error signal due to a tilt shift is determined and output by a coefficient output unit, and the coefficient output unit is provided by the coefficient output unit from each track signal on both sides adjacent to the main track. A crosstalk signal generating means for generating first and second crosstalk signals using a coefficient value; and subtracting a sum of the first and second crosstalk signals from the main track signal to output a reproduction signal. Output means.

According to the present invention, when the crosstalk component of one adjacent track is the largest (small) and the crosstalk component of the other adjacent track is small (many) due to an error (tilt error) of the tilt servo system, Is given to the crosstalk signal generating means so that the coefficient of the adjacent track becomes maximum (minimum) and the coefficient of the other adjacent track becomes minimum (maximum), and the crosstalk signal of each adjacent track is generated. By subtracting the sum of the two generated crosstalk signals from the main track signal and outputting a reproduced signal from which the crosstalk component has been removed, a crosstalk signal that takes into account the change in the crosstalk component due to an error in the tilt servo system is obtained. Becomes possible.

According to a fourth aspect of the present invention, there is provided a crosstalk removing apparatus for removing, from a main track signal of a main track to be reproduced, crosstalk signals from tracks on both sides adjacent to the main track. In the removing device, a coefficient value corresponding to the magnitude of the focus error signal and the magnitude of the tracking error signal is determined and output from the coefficient output means, and the coefficient output means receives the respective track signals on both sides adjacent to the main track from the coefficient output means. And a crosstalk signal generating means for generating first and second crosstalk signals using the coefficient values obtained, and subtracting the sum of the first and second crosstalk signals from the main track signal to obtain a reproduced signal. Output means for outputting.

According to the present invention, the coefficient is determined according to the magnitude of the error (focus error) of the focus servo system and the error (tracking error) of the tracking servo system, and the two adjacent tracks on both sides of the main track are determined according to the coefficient. By generating a crosstalk signal for each track, subtracting the sum of the two generated crosstalk signals from the main track signal, and outputting a reproduced signal from which the crosstalk component has been removed, errors in the focus servo system and the tracking servo system can be obtained. It is possible to obtain a crosstalk signal in consideration of the amount of change in the crosstalk component due to.

Further, in the crosstalk removing apparatus according to the present invention, a crosstalk signal is removed from a main track signal of a main track to be reproduced from a track on both sides adjacent to the main track. In the removing device, a coefficient value corresponding to the magnitude of the focus error signal, the magnitude of the tracking error signal, and the magnitude of the tilt error signal is determined and output from the coefficient output means, and the respective track signals on both sides adjacent to the main track. A crosstalk signal generating means for generating first and second crosstalk signals using the coefficient values provided by the coefficient output means; and a sum of the first and second crosstalk signals from the main track signal. And output means for outputting a reproduced signal.

According to the present invention, the coefficient is determined according to the magnitude of the error of the focus servo system (focus error), the error of the tracking servo system (tracking error), and the error of the tilt servo system (tilt error). , The crosstalk signals of two adjacent tracks on both sides of the main track are generated, the sum of the two generated crosstalk signals is subtracted from the main track signal, and the reproduction signal from which the crosstalk component has been removed is output, thereby achieving focus. It is possible to obtain a crosstalk signal in consideration of a change in a crosstalk component due to an error in the servo system, tracking servo system, and tilt servo system.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a crosstalk removing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

[Embodiment 1] In this embodiment 1,
In the furcus servo system, the gain for the first adjacent track signal and the gain for the second adjacent track signal are changed in accordance with the focus error signal to generate first and second crosstalk components, and An example in which the generated crosstalk component is removed will be described.

FIG. 1 is an explanatory diagram showing a change in beam shape due to a focus shift and a positional relationship between a main track and an adjacent track in a state where tracking errors can be ignored. In FIG, Tm is the main track, T ₁ adjacent tracks (1), T ₂ is adjacent tracks (2). Bb is the beam shape when focused, and Ba and Bc represent the beam shapes when the focus is shifted in the opposite direction about Bb. Here, beam B
b is close to a perfect circle, the beam Ba has a vertically long elliptical shape, and the beam Bc has a horizontally long elliptical shape.

As is apparent from FIG. 1, the vertically long elliptical beam Ba has the largest portion on the adjacent tracks T ₁ and T ₂ . That is, in the case of the beam Ba, the crosstalk component from the adjacent tracks T ₁ and T ₂ becomes the largest. On the other hand, the horizontally long elliptical beam Bc has the least portion on the adjacent tracks T ₁ and T _2, and
₁ and the crosstalk component from T ₂ becomes the least. In this example, since the tracking error is negligible, the changes (characteristics) due to the focus shift in the adjacent tracks T ₁ and T ₂ are the same.

FIG. 2 is an explanatory diagram showing an example of focus error detection using the astigmatism method. A, b, in FIG.
c corresponds to each of the reflected lights of the beams Ba, Bb, and Bc in FIG. 1, and the reflected lights a, b, and c are received by the respective divided surfaces 21, 22, 23, and 24 of the four-divided photosensor 20. Is shown.

Here, an operation (21 + 23)-(22 + 24) is performed on the output of the four-divided photosensor 20 (the output of each of the divided surfaces 21, 22, 23, and 24) to generate a focus error signal as shown in FIG. get. That is, FIG.
In FIG. 2 (b), the amount of received light is equal on each surface, so that the value is "0" (zero). The amount of received light by a vertically long beam is (22 + 24) larger than (21 + 23), so it is minus side, (2)
Since (2 + 24) is smaller than (21 + 23), it is a positive value. Note that a, b, and c in FIG.
, B, and c.

In this embodiment, an example of focus error detection by the astigmatism method has been described. However, if the focus error signal can be detected by another method such as the knife edge method, if the focus error signal can be detected by the astigmatism method, However, the present invention is not limited to this.

Next, a crosstalk removing circuit using the focus error signal detected as described above will be described. FIG. 5 is a block diagram showing the configuration of the crosstalk removing circuit according to the first embodiment of the present invention. The above-described focus error signal, the main track and the adjacent track 1 and 2 signals are input, and the crosstalk component is reduced. It outputs the canceled reproduction signal.

The crosstalk elimination circuit receives the focus error signal and supplies a coefficient value to a subsequent crosstalk signal generation unit. A crosstalk signal 1 generation unit 32 for generating a crosstalk signal, and a crosstalk signal 2 generation unit 33 for generating a crosstalk signal from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 31
And an addition circuit 34 for adding the output values of the crosstalk signal 1 generation unit 32 and the crosstalk signal 2 generation unit 33, and subtracting the sum of the crosstalk signals output from the addition circuit 34 from the main track signal to obtain a reproduced signal. And a differential operation circuit 35 for outputting.

In the above crosstalk removing circuit, first,
For example, the characteristic shown in FIG. 4 is given to the coefficient calculating unit 31 and the crosstalk signal of the adjacent track 1 (the adjacent track T ₁ in FIG. ₁ ) and the adjacent track 2 (the adjacent track T in FIG. ₂ ) The crosstalk signal is determined. A, b, and c in FIG. 4 correspond to the focus error signal values of a, b, and c in FIG.
That is, the coefficient value is increased in the state of Ba (the state where the crosstalk component is the largest) in FIG. 1, and the state of Bc (the state where the crosstalk component is the least) in FIG.
In such a case, a characteristic for reducing the coefficient value is given to each of the crosstalk signal 1 generation unit 32 and the crosstalk signal 2 generation unit 33.

The crosstalk signal 1 generating section 32 generates a first crosstalk signal from the input adjacent track 1 signal and the coefficient value of the coefficient calculating section 31, and the crosstalk signal 2 generating section 33 receives the first crosstalk signal. The second crosstalk signal is generated from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 31, and the two crosstalk signals are input to the addition circuit 34. This makes it possible to obtain a crosstalk signal in which a change in the crosstalk component due to an error in the focus servo system is considered. Then, the addition circuit 34
The two crosstalk signals are added to form a differential operation circuit 3
Enter 5 Further, the sum of the two crosstalk signals is subtracted from the main track signal to the differential operation circuit 35,
A reproduced signal from which a crosstalk component has been removed is output.

Therefore, in the first embodiment, it is possible to obtain a crosstalk signal of each of two adjacent tracks in consideration of a change in a crosstalk component due to a focus servo system error (focus error signal). , The crosstalk signal can be removed from the main track signal, and more accurate reproduction signal output can be realized.

[Embodiment 2] In this embodiment 2,
In the tracking servo system, the gain for the first adjacent track signal and the gain for the second adjacent track signal are changed according to the tracking error signal, and the first
An example will be described in which a second crosstalk component is generated and the generated crosstalk component is removed from the main track signal.

FIG. 6 is an explanatory diagram showing a change in beam position due to tracking deviation and a positional relationship between a main track and an adjacent track in a state where a focus error can be ignored. Here, as in Embodiment 1 described above,
The main track is Tm, the adjacent track (1) is T ₁ , and the adjacent track (2) is T ₂ . Further, Bb is the beam shape when the tracking is correct, Ba state are shifted to the adjacent track (2) T ₂ side, Bc is representative of the state is shifted to the adjacent track (1) T ₁ side I have.

As is apparent from FIG. 6, when a state of Ba is, the crosstalk component from the crosstalk component most adjacent track (1) T ₁ side from the adjacent tracks (2) T ₂ is small. On the other hand, when the state is Bc,
Crosstalk component from the crosstalk component most adjacent tracks (2) T ₂ side from the adjacent track (1) T ₁ side is smaller. Therefore, in a circuit as described below, the characteristic of the adjacent track 1 and the characteristic of the adjacent track 2 shown in FIG. Are obtained, two crosstalk signals are obtained.

FIG. 8 is a block diagram showing the configuration of a crosstalk removing circuit according to a second embodiment of the present invention. It outputs a reproduction signal in which a talk component has been canceled.

The crosstalk removing circuit shown in FIG.
A coefficient calculation unit 41 that receives a tracking error signal and supplies a coefficient value to a subsequent crosstalk signal generation unit, and generates a crosstalk signal 1 that generates a crosstalk signal from the adjacent track 1 signal and the coefficient value of the coefficient calculation unit 41 Part 42
And a crosstalk signal 2 generation unit 43 that generates a crosstalk signal from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 41, and the output values of the crosstalk signal 1 generation unit 42 and the crosstalk signal 2 generation unit 43. Adding circuit 44
And a differential operation circuit 45 that subtracts the sum of the crosstalk signals output from the addition circuit 44 from the main track signal and outputs a reproduced signal.

In the crosstalk elimination circuit configured as described above, the coefficient calculating section 41 instructs the crosstalk signal 1 generating section 42 and the crosstalk signal 2 generating section 43 to the state of Ba in FIG. When the crosstalk component from the first track is the largest and the crosstalk component from the adjacent track 1 is the smallest), the characteristic that the coefficient of the adjacent track 2 in FIG. On the other hand, in the Bc state in FIG. 6 (the crosstalk component from the adjacent track 1 is the largest and the crosstalk component from the adjacent track 2 is the smallest), the coefficient of the adjacent track 1 in FIG. A characteristic is provided such that the coefficient of 2 is minimized.

The crosstalk signal 1 generator 42 generates a first crosstalk signal from the input adjacent track 1 signal and the coefficient value of the coefficient calculator 41, and the crosstalk signal 2 generator 43 receives the first crosstalk signal. A second crosstalk signal is generated from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 31, and the two crosstalk signals are input to the addition circuit 44. This makes it possible to obtain a crosstalk signal that takes into account the change in the crosstalk component due to an error in the tracking servo system. Then, the addition circuit 44
Add the two crosstalk signals and input the result to the differential operation circuit 45. Further, the differential operation circuit 45
The sum of the two crosstalk signals is subtracted from the main track signal to output a reproduced signal from which crosstalk components have been removed.

Therefore, in the second embodiment, it is possible to obtain crosstalk signals of two adjacent tracks in consideration of a change in crosstalk component due to an error of the tracking servo system (tracking error signal). , The crosstalk signal can be removed from the main track signal, and more accurate reproduction signal output can be realized. The tracking error may be detected by a technique such as a push-pull method or a DPD method.

[Third Embodiment] In the third embodiment,
In the tilt servo system, the gain for the first adjacent track signal and the gain for the second adjacent track signal are changed in accordance with the tilt error signal to generate first and second crosstalk components. An example in which the generated crosstalk component is removed will be described.

FIG. 9 is an explanatory diagram showing a change in beam shape due to a tilt shift and a positional relationship between a main track and an adjacent track. Note that the tilt means a positional relationship (optical axis deviation) between an axis set perpendicular to the recording surface of the disc and an axis of the optical system. In FIG. 9, Bb represents the beam shape when the tilt is matched, and Ba and Bc represent the beam shapes when the tilt is shifted in the opposite direction about Bb.

As is apparent from FIG. 9, when a state of Ba is, the crosstalk component from the crosstalk component most adjacent track (1) T ₁ side from the adjacent tracks (2) T ₂ is small. On the other hand, when the state is Bc,
Crosstalk component from the crosstalk component most adjacent tracks (2) T ₂ side from the adjacent track (1) T ₁ side is smaller. Thus, in a circuit as described below, the characteristics of the adjacent track 1 and the characteristics of the adjacent track 2 shown in FIG.
Two crosstalk signals are obtained in consideration of a change in a crosstalk component due to an error in the tilt servo system.

FIG. 11 is a block diagram showing a configuration of the crosstalk removing circuit according to the third embodiment of the present invention.
The above-mentioned tilt error signal (see FIG. 10), the main track and the adjacent track 1 and 2 signals are input, and a reproduced signal in which a crosstalk component is canceled is output.

The crosstalk elimination circuit shown in FIG. 11 receives a tilt error signal and supplies a coefficient value to a subsequent crosstalk signal generation unit. Crosstalk signal 1 generation unit 52 that generates a crosstalk signal from coefficient values
And the crosstalk signal 2 generation unit 53 that generates a crosstalk signal from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 51, and the output values of the crosstalk signal 1 generation unit 52 and the crosstalk signal 2 generation unit 53. Adding circuit 54
And a differential operation circuit 55 that subtracts the sum of the crosstalk signals output from the adder circuit 54 from the main track signal and outputs a reproduced signal.

In the crosstalk elimination circuit configured as described above, the coefficient calculation unit 51 instructs the crosstalk signal 1 generation unit 52 and the crosstalk signal 2 generation unit 53 to the state of Ba in FIG. , The crosstalk component from the adjacent track 1 is the largest, and the crosstalk component from the adjacent track 1 is the smallest). On the other hand, in the Bc state in FIG. 9 (the crosstalk component from the adjacent track 1 is the largest and the adjacent track 2
When the crosstalk component is small), the characteristic that the coefficient of the adjacent track 1 in FIG. 10 is the largest and the coefficient of the adjacent track 2 is the smallest is given.

The crosstalk signal 1 generator 52 generates a first crosstalk signal from the input adjacent track 1 signal and the coefficient value of the coefficient calculator 51, and the crosstalk signal 2 generator 53 receives the first crosstalk signal. The second crosstalk signal is generated from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 51, and the two crosstalk signals are input to the addition circuit 54. As described above, it is possible to obtain a crosstalk signal in which a change in the crosstalk component due to an error in the tracking servo system is considered. Then, the addition circuit 44
The two crosstalk signals are added and the differential operation circuit 5
Enter 5 Further, the sum of the two crosstalk signals is subtracted from the main track signal to the differential operation circuit 55,
A reproduced signal from which a crosstalk component has been removed is output.

Therefore, in the third embodiment, it is possible to obtain crosstalk signals of two adjacent tracks in consideration of a change in crosstalk component due to an error (tilt error signal) in the tilt servo system. The crosstalk signal can be removed from the main track signal, and more accurate reproduction signal output is realized.
The tilt error is detected by incorporating a tilt sensor or a pickup.

[Embodiment 4] By the way, in the above-described Embodiments 1 and 2, when errors in both the focus and tracking servo systems cannot be ignored, as is apparent from FIGS. It is necessary to consider two error components. Thus, in the fourth embodiment, in the focus servo system and the tracking servo system, the first
An example in which the gain for the adjacent track signal and the gain for the second adjacent track signal are changed to generate the first and second crosstalk components, and the generated crosstalk component is removed from the main track signal will be described. .

FIG. 12 is a block diagram showing a configuration of the crosstalk removing circuit according to the fourth embodiment of the present invention.
The above-mentioned focus error signal (see FIG. 4) and tracking error signal (see FIG. 7), the main track and the adjacent track 1 and 2 signals are input, and a reproduction signal in which a crosstalk component is canceled is output.

The crosstalk elimination circuit shown in FIG. 12 receives a focus error signal and a tracking error signal, and supplies a coefficient value to a crosstalk signal generator at the subsequent stage. A crosstalk signal 1 generation unit 62 that generates a crosstalk signal from the coefficient value of the calculation unit 61; a crosstalk signal 2 generation unit 63 that generates a crosstalk signal from the adjacent track 2 signal and the coefficient value of the coefficient calculation unit 61; An addition circuit 64 for adding the output values of the crosstalk signal 1 generation unit 62 and the crosstalk signal 2 generation unit 63; and a reproduction signal is output by subtracting the sum of the crosstalk signals output from the addition circuit 64 from the main track signal. A differential operation circuit 65.

In the crosstalk removing circuit configured as described above, the crosstalk signal 1 generation unit 6 is provided to the coefficient calculation unit 61 in consideration of both characteristics as shown in FIGS.
2 (first crosstalk signal) and an input coefficient to the crosstalk signal 2 generator 63 (second crosstalk signal) are determined and supplied. Then, the crosstalk signal 1 generation unit 62 and the crosstalk signal 2 generation unit 63 generate respective crosstalk signals, and the addition circuit 74
To enter. As described above, it is possible to obtain a crosstalk signal in which a change in a crosstalk component due to an error between the focus servo system and the tracking servo system is considered.
Then, the addition circuit 64 adds the two crosstalk signals and inputs the result to the differential operation circuit 65. Further, the sum of the two crosstalk signals is subtracted from the main track signal to the differential operation circuit 65, and a reproduced signal from which a crosstalk component has been removed is output.

Therefore, in the fourth embodiment, the crosstalk signal of each of two adjacent tracks in consideration of the change in the crosstalk component due to the error (focus error signal, tracking error signal) between the focus servo system and the tracking servo system. Therefore, the crosstalk signal can be removed from the main track signal, and more accurate reproduction signal output can be realized.

[Fifth Embodiment] As is clear from FIGS. 1, 6 and 9 in the first to third embodiments, the error of the three servo systems of focus, tracking and tilt cannot be ignored. Needs to consider these three error components. Therefore, in the fifth embodiment, in the focus servo system, the tracking servo system, and the tilt servo system, the gain for the first adjacent track signal and the second adjacent track signal in accordance with the focus error signal, the tracking error signal, and the tilt error signal. In the following, an example will be described in which first and second crosstalk components are generated by changing the gain with respect to, and the generated crosstalk components are removed from the main track signal.

FIG. 13 is a block diagram showing the configuration of the crosstalk removing circuit according to the fifth embodiment of the present invention.
The focus error signal (see FIG. 4), the tracking error signal (see FIG. 7), and the tilt error signal (see FIG. 1)
0), a main track and adjacent track 1 and 2 signals are input, and a reproduced signal in which a crosstalk component is canceled is output.

The crosstalk removing circuit shown in FIG. 13 receives a focus error signal, a tracking error signal, and a tilt error signal, and supplies a coefficient value to a subsequent crosstalk signal generating section, and an adjacent track. A crosstalk signal 1 generating section 72 for generating a crosstalk signal from one signal and a coefficient value of the coefficient calculating section 71 and a crosstalk signal 2 generating a crosstalk signal from an adjacent track 2 signal and a coefficient value of the coefficient calculating section 71 Part 7
3, an addition circuit 74 for adding the output values of the crosstalk signal generation units 72 and 73, and a differential operation circuit for outputting a reproduction signal by subtracting the sum of the crosstalk signals output from the addition circuit 74 from the main track signal. 75.

In the crosstalk elimination circuit configured as described above, the coefficient calculation section 71
Considering the three characteristics shown in FIG.
The input coefficient to the generator 72 (first crosstalk signal) and the input coefficient to the crosstalk signal 2 generator 73 (second crosstalk signal) are determined and supplied. Then, the crosstalk signal generator 72 and the crosstalk signal 2 generator 73
Thus, respective crosstalk signals are generated and input to the adding circuit 74. This makes it possible to obtain a crosstalk signal in which a change in the crosstalk component due to errors in the focus servo system, tracking servo system, and tilt servo system is considered. Then, the addition circuit 74 adds the two crosstalk signals and inputs the result to the differential operation circuit 75. Further, the sum of the two crosstalk signals is subtracted from the main track signal to the differential operation circuit 65, and a reproduced signal from which a crosstalk component has been removed is output.

Therefore, in the fifth embodiment, the two adjacent servo cells, which take into account the change in the crosstalk component due to errors (focus error signal, tracking error signal, tilt error signal) between the focus servo system, the tracking servo system, and the tilt servo system, are taken into account. Since it is possible to obtain the crosstalk signal of each of the tracks, the crosstalk signal can be removed from the main track signal, and more accurate reproduction signal output can be realized.

[0055]

As described above, according to the crosstalk removing apparatus according to the present invention (claim 1), when the crosstalk component due to the error (focus error) of the focus servo system is the largest, the coefficient value is reduced. To the crosstalk signal generating means so as to reduce the coefficient value when the crosstalk component is the least, and to generate the first crosstalk signal from the first adjacent track signal and the coefficient value. Then, a second crosstalk signal is generated from the second adjacent track signal and the coefficient value, and the generated 2nd crosstalk signal is generated.
Subtracting the sum of the two crosstalk signals from the main track signal to obtain a crosstalk signal that takes into account the change in the crosstalk component due to errors in the focus servo system (the deviation of the actual reading position from the ideal optical position) Therefore, crosstalk noise is removed from the signal of the main track to be reproduced, and a more accurate reproduced signal can be output.

Further, according to the crosstalk removing apparatus according to the present invention (claim 2), the crosstalk component of one adjacent track due to an error (tracking error) of the tracking servo system is the largest (smallest) and the other adjacent track is the largest. When the crosstalk component of a track is small (large), the characteristic that one of adjacent tracks has a maximum (minimum) coefficient and the other adjacent track has a minimum (maximum) coefficient is provided to the crosstalk signal generation means. Then, a crosstalk signal of each adjacent track is generated, and the sum of the two generated crosstalk signals is subtracted from the main track signal, whereby a change in the crosstalk component due to an error in the tracking servo system (ideal optical position) Crosstalk signal that takes into account the actual reading position shift with respect to Crosstalk noise from the signal of the main track of interest is removed, it is possible to output a more accurate reproduction signal.

According to the crosstalk removing apparatus of the present invention (claim 3), the crosstalk component of one adjacent track due to an error (tilt error) of the tilt servo system is the largest (smallest) and the other adjacent track is the largest. Is given to the crosstalk signal generating means such that the coefficient of one adjacent track is maximum (minimum) and the coefficient of the other adjacent track is minimum (maximum) when the crosstalk component is small (large). , A crosstalk signal of each adjacent track is generated, and the sum of the two generated crosstalk signals is subtracted from the main track signal. The crosstalk signal can be obtained in consideration of the shift of the reading position of the Crosstalk noise is removed from the click signal, can output a more accurate reproduction signal.

Further, according to the crosstalk removing apparatus of the present invention (claim 4), the coefficient is determined according to the magnitude of the error of the focus servo system (focus error) and the error of the tracking servo system (tracking error). The crosstalk signals of the two adjacent tracks on both sides of the main track are generated in accordance with the coefficient, and the sum of the two generated crosstalk signals is subtracted from the main track signal to thereby obtain the focus servo system and the tracking servo system. Since it is possible to obtain a crosstalk signal in consideration of a change in a crosstalk component due to an error (a deviation of an actual reading position from an ideal optical position), crosstalk noise is reduced from a signal of a main track to be reproduced. It is removed and a more accurate reproduction signal can be output.

Further, according to the crosstalk removing apparatus of the present invention (claim 5), an error of the focus servo system (focus error), an error of the tracking servo system (tracking error), and an error of the tilt servo system (tilt error). Is determined according to the magnitude of the crosstalk signal, crosstalk signals of two adjacent tracks on both sides of the main track are generated in accordance with the coefficient, and the sum of the generated two crosstalk signals is subtracted from the main track signal. Since it is possible to obtain a crosstalk signal in consideration of a change in a crosstalk component due to an error in a focus servo system, a tracking servo system, and a tilt servo system (a deviation of an actual reading position from an ideal optical position), a reproduction target is obtained. Crosstalk noise is removed from the main track signal It is possible to output the raw signal.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a change in beam shape due to a focus shift and a positional relationship between a main track and an adjacent track in a state where tracking errors can be ignored.

FIG. 2 is an explanatory diagram showing an example of focus error detection using an astigmatism method.

FIG. 3 is a graph showing a focus error signal.

FIG. 4 is a characteristic graph showing a coefficient value of a focus error signal given to a coefficient calculation unit.

FIG. 5 is a block diagram illustrating a configuration of a crosstalk removing circuit according to the first embodiment of the present invention;

FIG. 6 is an explanatory diagram showing a change in beam position due to tracking deviation and a positional relationship between a main track and an adjacent track in a state where a focus error can be ignored.

FIG. 7 is a characteristic graph showing a coefficient value of a tracking error signal provided to a coefficient calculation unit.

FIG. 8 is a block diagram illustrating a configuration of a crosstalk removing circuit according to a second embodiment of the present invention;

FIG. 9 is an explanatory diagram showing a change in beam shape due to a tilt shift and a positional relationship between a main track and an adjacent track.

FIG. 10 is a characteristic graph showing a coefficient value of a tilt error signal given to a coefficient calculation unit.

FIG. 11 is a block diagram illustrating a configuration of a crosstalk removing circuit according to a third embodiment of the present invention;

FIG. 12 is a block diagram illustrating a configuration of a crosstalk removing circuit according to a fourth embodiment of the present invention;

FIG. 13 is a block diagram illustrating a configuration of a crosstalk removing circuit according to a fifth embodiment of the present invention;

[Explanation of symbols]

 31, 41, 51, 61, 71 Coefficient calculation unit 32, 42, 52 Crosstalk signal 1 generation unit 33, 43, 53 Crosstalk signal 2 generation unit 34, 44, 54, 64, 74 Addition circuit 35, 45, 55 , 65, 75 Differential operation circuit 62, 72 Crosstalk signal 1 generator 63, 73 Crosstalk signal 2 generator

Claims (5)

[Claims] 1. A crosstalk removing apparatus for removing a crosstalk signal from a track on both sides adjacent to a main track from a main track signal of a main track to be reproduced, the magnitude of a focus error signal due to a focus shift. A coefficient output means for determining and outputting a coefficient value according to the following: a first coefficient value using the coefficient value given from the coefficient output means from each track signal on both sides adjacent to the main track;
And a crosstalk signal generating means for generating a second crosstalk signal, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduction signal. A crosstalk removing device, comprising: 2. A crosstalk removing apparatus for removing a crosstalk signal from a track on both sides adjacent to the main track from a main track signal of a main track to be reproduced, the magnitude of a tracking error signal due to a tracking error. A coefficient output means for determining and outputting a coefficient value according to the following: a first coefficient value using the coefficient value given from the coefficient output means from each track signal on both sides adjacent to the main track;
And a crosstalk signal generating means for generating a second crosstalk signal, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduction signal. A crosstalk removing device, comprising: 3. A crosstalk removing apparatus for removing a crosstalk signal from a track on both sides adjacent to the main track from a main track signal of a main track to be reproduced, the magnitude of a tilt error signal due to a tilt shift. A coefficient output means for determining and outputting a coefficient value according to the following: a first coefficient value using the coefficient value given from the coefficient output means from each track signal on both sides adjacent to the main track;
And a crosstalk signal generating means for generating a second crosstalk signal, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduction signal. A crosstalk removing device, comprising: 4. A crosstalk removing apparatus for removing, from a main track signal of a main track to be reproduced, crosstalk signals from tracks on both sides adjacent to the main track, the magnitude of the focus error signal and the tracking error signal A coefficient output means for determining and outputting a coefficient value corresponding to the magnitude, and a first coefficient value provided from the coefficient output means from each track signal on both sides adjacent to the main track.
And a crosstalk signal generating means for generating a second crosstalk signal, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduction signal. A crosstalk removing device, comprising: 5. A crosstalk removing apparatus for removing, from a main track signal of a main track to be reproduced, crosstalk signals from tracks on both sides adjacent to the main track, the magnitude of the focus error signal and the tracking error signal A coefficient output means for determining and outputting a coefficient value in accordance with the magnitude and the magnitude of the tilt error signal; and a coefficient output means for outputting the coefficient value given from the coefficient output means from each track signal on both sides adjacent to the main track. 1
And a crosstalk signal generating means for generating a second crosstalk signal, and an output means for subtracting the sum of the first and second crosstalk signals from the main track signal and outputting a reproduction signal. A crosstalk removing device, comprising: