JP3289804B2 - Optical disk and optical disk reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and an optical disk reproducing apparatus, and more particularly, to canceling mixed crosstalk by using read signals of a plurality of signal tracks.
The present invention relates to an optical disc reproducing apparatus suitable for reproducing a recording signal of a desired signal track.

[0002]

2. Description of the Related Art Conventionally, a signal pit array is spirally arranged on a signal recording surface from an inner peripheral side to an outer peripheral side of a disk.
2. Description of the Related Art An optical disk on which a signal is recorded by forming a track by a signal pit string is known. In such an optical disc, a method of increasing the recording density of pits in the track direction,
2. Description of the Related Art A method of narrowing a beam of a reading laser beam, a method of narrowing a track pitch, and the like have been increasing the density and capacity of information recorded on an optical disk.

In the method of narrowing the track pitch, the track pitch is limited by the diameter of the light spot condensed on the disk. Therefore, if the track pitch is narrowed without changing the spot diameter, signals of adjacent tracks are reproduced together. As a result, there is a problem that crosstalk becomes large and a desired signal cannot be reproduced.

As a countermeasure against the influence of the crosstalk, three light spots are irradiated on each of three adjacent tracks, signals are read from the respective tracks, and the crosstalk mixed in the read signal of the center track is calculated as follows. A method of canceling by the read signals of the other two tracks on both sides thereof has been proposed. For example, JP-A-3-40
In the method proposed in Japanese Patent Publication No. 225, a frequency variable filter is provided, the frequency characteristics of the output are changed so as to eliminate crosstalk, and crosstalk is canceled by finding an optimum point. There is also proposed a method of obtaining a cancellation coefficient such that there is no correlation between signals of adjacent tracks (see "Nikkei Electronics" [Nikkei BP] No. 495 (1990.3.19), pp. 98 to 99).

[0005]

As described above, when reproducing a high-density optical disc, a crosstalk canceling operation is always performed. For this reason, even when the crosstalk is sufficiently small, the effect of noise or the like is considered as crosstalk, and a crosstalk canceling operation is performed. As a result, there is a problem that the extra signal component of the reproduced signal is increased. is there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disk reproducing apparatus capable of prohibiting the operation of the crosstalk cancel operation when the crosstalk cancel operation is unnecessary.

[0007]

According to the present invention, there is provided an optical disk reproducing apparatus for receiving reflected light from at least one light spot applied to a signal track of an optical disk and reproducing a recorded signal of the signal track. In the apparatus, at the time of reproducing a recording signal of the signal track, a canceling unit for canceling crosstalk from an adjacent signal track, a detecting unit for detecting an amount of crosstalk from an adjacent signal track, and a signal detected by the detecting unit. And control means for prohibiting the operation of the canceling means when the crosstalk amount is smaller than a predetermined value.

In the reproducing apparatus according to the present invention, the detecting means extracts a cancellation coefficient based on a recording signal from an adjacent signal track and calculates a sum of the cancellation coefficients. The control means prohibits the operation of the cancel means when the total cancel coefficient from the detection means is smaller than a predetermined value.

Furthermore, the optical disk reproducing apparatus of the present invention is
Crosstalk cancel operation prohibition flag in certain areas
An optical disc player that plays back an optical disc recorded in advance
A raw device, and receives the reflected light from the at least one light spot is irradiated on the signal track of the optical disc, the optical disc reproducing apparatus for reproducing a recording signal of the signal track, reproduction of the recorded signal of the signal track Sometimes, canceling means for canceling crosstalk from an adjacent signal track, detecting means for detecting a track pitch of the optical disc, and when the track pitch detected by the detecting means is larger than a predetermined value, the canceling means And control means for prohibiting the operation.

[0010]

According to the present invention, the amount of crosstalk from an adjacent signal track is detected, and when the amount of crosstalk is smaller than a predetermined value, the operation of the canceling means is prohibited.

Further, according to the present invention, the track pitch of the optical disk is detected, and when the track pitch is larger than a predetermined value, the influence of crosstalk is considered to be small.
The operation of the cancellation means is prohibited.

Further, according to the present invention, when reproducing an optical disk in which a crosstalk canceling operation prohibition flag is recorded in a predetermined area in advance, when the operation prohibition flag is detected, the operation of the canceling means is prohibited.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a relationship between an optical disk and a detection circuit.

1, signal tracks T, T,... Formed of pits P, P,... Are formed on an optical disk 10, and three adjacent signal tracks 12 of the signal tracks T, T,. , 14, and 16 are irradiated with three light spots 20, 22, and 24 from the light beam radiator 18 one after another. Light spots 20, 22, 2
4 are respectively received by photodetectors 28, 30, and 32 in a detection circuit 26, and read signals 34, 36, and
38. As described later, the crosstalk mixed in the read signal 36 based on the central signal track 14 is caused by the adjacent signal tracks 12 and 16 on both sides of the read signal 36.
Is canceled by the read signals 34 and 38 based on.

FIG. 2 shows a block circuit of an optical disk reproducing apparatus according to a first embodiment of the present invention. In FIG. 2, read signals 34, 36, and 38 indicate read signals from the photodetectors 28, 30, and 32 in FIG. 2, and a read signal 36 based on a central signal track is a crosstalk canceling signal connected in series. The output signals pass through devices 40 and 42, while the read signals 34 and 34 based on adjacent tracks on both sides are output.
38 is supplied to digital filters (variable frequency filters) 44 and 46, respectively. Digital filter 4
4 is supplied to one input terminal of a comparator 50, and the other input terminal of the comparator 50 is supplied with the read signal 36.
And supplies a comparison signal 52 to a coefficient calculator 54. The coefficient calculator 54 calculates a coefficient based on the comparison signal 52 and supplies the coefficient to the digital filter 44. The digital filter 44 determines the read signal 34 based on the coefficient.
Process. Thus, the digital filter 44
Calculates the crosstalk signal 55 from the read signal 34 based on one adjacent track, and the crosstalk signal 55 is supplied to the crosstalk canceler 42 via the B side of a switch 56 described later. Crosstalk canceler 42
Removes the crosstalk due to one adjacent track from the read signal 36 based on the crosstalk signal 55.

Similarly, the digital filter 46, the comparator 60, and the coefficient calculator 62 determine the crosstalk signal 64 from the read signal 38 based on the other adjacent track. Is supplied to the crosstalk canceller 40 through the B side of the above. The crosstalk canceller 40 removes crosstalk due to the other adjacent track from the read signal 36 based on the crosstalk signal 64.

The coefficients from the coefficient calculator 54 are supplied to a summer 68, which calculates the sum of the coefficients. When the sum of the coefficients is smaller than a predetermined value, the summer 68 determines that the area is a wide track pitch area where crosstalk cancellation is unnecessary, and switches the switch 56 to the A side. As a result, the crosstalk signal 55 is not supplied to the crosstalk canceller 42,
The operation of the crosstalk canceler 42 is prohibited.

Similarly, the summer 70 is operated by the coefficient calculator 6
The sum of the coefficients from 2 is obtained. If the sum of the coefficients is smaller than a predetermined value, the switch 66 is switched to the A side. As a result, the crosstalk signal 64 is not supplied to the crosstalk canceller 40, and the crosstalk canceler 40 is in an operation prohibited state.

FIG. 3 shows a block circuit of an optical disk reproducing apparatus according to a second embodiment of the present invention. In FIG. 3, the read signals 34, 36, 38 indicate read signals from the photodetectors 28, 30, 32 of FIG.
The read signal 36 based on the center signal track is supplied to a delay circuit 72, while the read signals 34 and 38 based on adjacent tracks on both sides are respectively converted into digital filters 74 and
76. Read signal 7 from the delay circuit 72
7 is output through the crosstalk canceller 78. On the other hand, a crosstalk signal 80 from the digital filter 74 is supplied to a crosstalk canceller 78 via a switch B, which will be described later, and the crosstalk canceler 78 performs one-way operation based on the crosstalk signal 80. Is removed from the read signal 77. Similarly, the digital filter 7
The crosstalk signal 84 from the switch 8
6 is supplied to the crosstalk canceler 78 via the B side, and the crosstalk canceler 78 removes the crosstalk due to the other adjacent track from the read signal 77 based on the crosstalk signal 84.

Here, in a predetermined area of the optical disk, for example, in a sector header, flags relating to the crosstalk canceling operation and the operation prohibition are recorded in advance as follows.

Flag: Crosstalk cancel operation, operation prohibition 11: Crosstalk by adjacent tracks on both sides is canceled. 10: Only the cross stroke by one adjacent track (track 12 in FIG. 2) is cancelled.

01: Cancel only the cross stroke by the other adjacent track (track 16 in FIG. 2). 00: Do not cancel crosstalk by adjacent tracks on both sides.

In order to read the sector header of the optical disk, the read signal 36 is supplied to a sector header reader 88, and the reader 88 operates the switches 82 and 86 and the crosstalk canceller 78 based on the flag of the sector header. Control is performed as follows.

Flag: switch 82: switch 86: crosstalk canceller 78 11: B side: B side: ON operation 10: B side: A side: ON operation 01: A side: B side: ON operation 00:- :--: Off operation As described above, the reader 88 controls the switches 82 and 86 and the crosstalk canceller 78 to perform a predetermined operation of canceling the crosstalk specified in the flag of the sector header of the optical disk. The operation is prohibited.

Next, FIG. 4 shows various track pitches.
Have been. Referring to FIG.
Rack T₁, T_Two, T_Three, T_Four, T _FiveIs formed
And the sign d₁, D_Two, D_Three, D_FourIs the track pitch
Show.

When the light beam spot 92 is on the track T ₂ , the track pitches d ₁ and d ₂ are detected,
Since both track pitches d ₁ and d ₂ are smaller than the predetermined value, crosstalk based on adjacent tracks T ₁ and T ₃ on both sides is canceled.

The light beam spot 94 is located on the track T
If there on ₃ detects the track pitch d ₂ and d _3. Since the track pitch d ₂ is smaller than the predetermined value, the crosstalk is crosstalk based on the inner side of the adjacent track T ₂ is canceled, since the track pitch d ₃ is greater than a predetermined value, based on the outer side of the adjacent track T ₄ Is not canceled.

Further, the light beam spot 96 is located on the track T
₄ , the track pitches d ₃ and d ₄ are detected, and since both track pitches d ₃ and d ₄ are both larger than a predetermined value, crosstalk based on adjacent tracks T ₃ and T ₅ on both sides is generated. Not canceled.

[0029]

As described above, according to the present invention, when the crosstalk cancel operation is unnecessary, the crosstalk operation is prohibited, so that the extra signal component of the reproduced signal is not increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an optical disk and a detection circuit.

FIG. 2 is a block circuit diagram of the optical disc reproducing apparatus according to the first embodiment of the present invention.

FIG. 3 is a block circuit diagram of an optical disc reproducing apparatus according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of various track pitches.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical disk 12, 14, 16 ... Signal track 40, 42 ... Crosstalk canceller 44, 46 ... Digital filter 56, 66 ... Switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/013

Claims (4)

(57) [Claims] 1. A method comprising: receiving reflected light from at least one light spot applied to a signal track of an optical disc;
An optical disc reproducing apparatus for reproducing a recording signal of the signal track, a canceling unit for canceling crosstalk from an adjacent signal track when reproducing the recording signal of the signal track, and detecting an amount of crosstalk from an adjacent signal track. An optical disc reproducing apparatus, comprising: a detecting unit for performing the operation of the canceling unit when the amount of crosstalk detected by the detecting unit is smaller than a predetermined value. 2. The optical disk reproducing apparatus according to claim 1, wherein said detecting means extracts a cancel coefficient based on a recording signal from an adjacent signal track, and obtains a total sum of said cancel coefficients. An optical disc reproducing apparatus for prohibiting the operation of the canceling means when the total sum canceling coefficient from the detecting means is smaller than a predetermined value. 3. Receiving reflected light from at least one light spot applied to a signal track of an optical disc,
An optical disc reproducing apparatus for reproducing a recording signal of the signal track; a canceling unit for canceling crosstalk from an adjacent signal track when reproducing the recording signal of the signal track; a detecting unit for detecting a track pitch of the optical disc; An optical disc reproducing apparatus, comprising: control means for prohibiting the operation of the canceling means when the track pitch detected by the detecting means is larger than a predetermined value. 4. A signal of an optical disc in which a crosstalk cancel operation prohibition flag is recorded in a predetermined area in advance.
At least one light spot on the track
These reflected lights are received and the recording signal of the signal track is
In the optical disc reproducing apparatus for reproducing, when reproducing the recording signal of the signal track, an adjacent signal track is reproduced.
Cancel hand to cancel the crosstalk from a click
A step and the crosstalk cap of a predetermined area of the optical disc.
Detecting means for detecting the operation inhibition flag, and detecting the key when the detection means detects the operation inhibition flag.
An optical disc reproducing device comprising: a control unit for prohibiting the operation of the cancel unit .