JPH0668487A - Tracking error signal generating device - Google Patents

Abstract

PURPOSE:To eliminate the influence of a shift in the position of a tracking pit by detecting the actual recording position of the tracking pit on an optical disk, and generating a tracking error signal according to a corresponding playback signal and sampling it at a correct position. CONSTITUTION:A timing control circuit 13 generates gate signals GA and GB corresponding to time ranges of one clock before and after a specific pulse rises according to a clock signal CLK and supplies them to AND circuits 15 and 16. A differentiating circuit 14A, on the other hand, differentiates the playback signal SPB to detect a zero-crossing point and supplies a peak detection signal PE to the AND circuits 15 and 16, which output sampled signals SMP1 and SMP2 corresponding to the peak positions of wobble pits. Sample holding circuits 17 and 18 generate signals A and B according to those signals SMP and a subtracter 19 finds a tracking error signal TE'=A-B. In an on-track state, TE'=0 holds. In this constitution, sampling is performed at correct timing even if the tracking pit shifts in position owing to rotation jitters, etc., of a recording device, and the tracking error signal can securely be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking error signal generator, and more particularly to a sampled servo system (sample
and a tracking error signal generating device for generating a tracking error signal from an optical disc of high density recording using a d servo method).

[0002]

2. Description of the Related Art A sampled servo recording format is known as a conventional optical disk recording format.

FIG. 4 shows the recording format of a sampled servo type optical disc. The sampled servo type optical disc does not have a pre-group (guide groove) on the recording film of the optical disc, and 137 in one track.
Servo areas (fields) are pre-formatted at 6 locations. For sampled servo optical disks, tracking errors and recording / recording
The feature is that a clock for reproduction and the like can be generated by sampling.

In the program area PA of the optical disk DK
As shown in FIG. 4, the optical disc DK is
A spiral signal track that expands to the circumference
Has been formed. One track is divided into 32 sectors
Has been. Each sector consists of 43 segments.
Each one segment consists of 18 bytes. 1 sec
The first segment # 0 of the
Sector synchronization signal S for_sync(2 bits) and its
Sector address S for indicating the address of the sector
_ADR(16 bits) is pre-formatted. The
Reformat is the mastering of the optical disc DK
Is done in the process of. Each of segments # 1 to # 42
Is a 2-byte servo area F_SAnd 16-byte data area
Area F_DAnd 18 bytes in total.

FIG. 5 shows a servo area F_SRecord format
Indicates the 2-byte servo area F _SIs 1 byte at a time
It is divided into two sub-bytes # 1 and # 2. The servo
The first wobble pit P is at the 3rd bit in byte # 1.
_W1, The second wobble pit P at the 8th bit_W2Is that
Pre-formatted. This first wobble
Tut P_W1The position of 16 tracks as shown in FIG.
P for (A)_W1AIt is the third bit like
It becomes P when it becomes a rack (B)_W1BMove to the 4th bit like
It In this way, the first wobble pit every 16 tracks
P_W1By switching the position of,
The number of racks can be detected accurately.

The first wobble pit P _W1 and the second wobble pit P _W2 are arranged to be offset from each other in the trace direction left and right (in the radial direction of the write-once optical disc DK) by 1/4 of the track pitch with the track center TC as a boundary. The tracking error detection is performed based on the difference between the amount of return light at the first wobble pit P _W1 and the amount of return light at the second wobble pit P W2. A clock pit CP for synchronization is pre-formatted in the 12th bit of the servo byte # 2. Second wobble pit P _W2 and clock pit C
A mirror surface having an interval of 19 channel clocks is formed between P and P, and 19 channel clocks are counted during this period to synchronize each segment, and a focus error occurs during this synchronization detection period. Detection is also done. FIG. 5 shows the tracking signal S _T1 (S _{T1 A} or S _T1B ) obtained by reading the above servo area F _S with laser light and the sector synchronization signal S _sync .

Next, a method of tracking error detection by wobble pits will be described with reference to FIG. A is a case where the read beam passes on the center axis (track center axis) of the pair of wobble pits P _W1 and P _W2, and the RF signal in that case is shown as S _A. When the light passes through the vicinity of the pit, the amount of reflected light becomes small due to the diffraction effect of light, and the light becomes dark, and when it passes directly above the clock pit CP, it becomes the darkest. B is the case where the read beam has passed the inner circumference side of the track center axis, and the RF signal at that time is S _B
Indicated as. In this case, to pass just above the wobble pits P _W1, dark portion due to the wobble pits P _W1 still darker than the dark portion due to the wobble pits P _W2. C
Is the case where the read beam has passed the outer peripheral side of the track center axis, and the RF signal in this case is shown as S _C ,
In this case, a waveform opposite to S _B is shown.

Here, the signal value obtained by performing signal sampling at the time of the wobble pit P _W1 is SAMPLE.
(T ₁ ) and the signal value obtained by signal sampling at the time of the wobble pit P _W2 is SAMPLE (T ₂ ).
As the difference between them, SAMPLE (T ₁ ) -SAMPLE
Taking (T ₂ ), the value of A is zero, the value of B is a negative value, and the value of C is a positive value. Therefore, SAMPLE
If (T ₁ ) -SAMPLE (T ₂ ) = TE, then TE
Can be used as a tracking error signal.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to servo system, wobble pit P for servo_W1, P
_W2Or clock pit CP on the optical disk in advance
You can make it (pre-pit) and use the pit train
Obtaining various information for servos such as locking error signals
become.

When reading information, the laser light reflected at the signal pit PT is diffracted by the pits and the amount of light returning to the optical pickup is reduced, and it can be regarded as a dark portion. On the contrary, since the intermediate portion between the signal pits PT is a mirror surface and all the laser light is reflected, the amount of return light increases and can be regarded as a bright portion. In order to read the servo information accurately, it is necessary to read these contrasts without error,
For that purpose, conventionally, as shown in FIG. 7A, the track pitch T _P needs to be larger than the spot diameter B _L of the laser light (about 1.6 μm).

In this case, in order to improve the recording density of the optical disk DK, FIG. 7B or FIG. 7C is used.
As shown, conventional 1/2 the track pitch T _P
Considering the case of shortening to about (0.8 μm), there are an on-track state where the laser beam center is on the recording track axis center and an off-track state where the laser beam center is off the recording track axis center. There is a problem that the difference in light amount becomes small and accurate servo cannot be performed, and there is a limit in narrowing the track pitch.

In order to solve this, the applicant has proposed a method in which wobble pits are thinned and recorded (Japanese Patent Application No. Hei 0).
3-64978). FIG. 8 shows the structure of tracks and pits of a CAV optical disk used in the double density recording method proposed by the applicant.

As shown in FIG. 8, in the 2k-th recording track, the wobble pits P _W (2k-
1) and a wobble pit P _W (2k) are provided, a synchronous pit P _SYNC and a recording track identification pit P _DET are provided on the recording track axis, and a data area follows. The next (2k + 1) th recording track has a wobble pit P _W (2k) and a wobble pit P _W (2k + 1) in a zigzag pattern opposite to the 2kth recording track.
In this configuration, the synchronous pit P _SYNC is provided on the recording track axis, but the recording track identification pit P _DET is not provided.

In this case, for the 2kth recording track, the wobble pit P _W (2k-1) corresponds to the first wobble pit P _W1 , and the wobble pit P _W (2k) corresponds to the second wobble pit P _W2 . However, the second (2k +
For the 1) th recording track, the wobble pit P _W
(2k + 1) corresponds to the first wobble pit P _W1 , and the wobble pit P _W (2k) corresponds to the second wobble pit.

In this way, the 2kth recording track and the (2k + 1) th recording track share the wobble pit P _W (2k) with each other. Therefore, this is because one of the staggered wobble pits is thinned out for each recording track, and as a result, the recording track pitch T _P = 2L and T _P = 4L (see FIG. 7). Recording track pitch width T compared to (a))
_P is shortened to 1/2. Therefore, since the number of recordable tracks can be doubled, the recording density can be doubled.

FIG. 9 shows the reproduction of the recording signal of the optical disk of FIG.
The basic configuration of the reproducing apparatus is shown. The playback device 10P
Reproduction signal S of the taking beam LB_PBDecode (= RF signal)
Play data D_PBDecoder 11 for outputting
Playback signal S with no PLL circuit_PBBased on the clock
A clock extraction circuit 12 that outputs a signal CLK, and a clock
First sample of sampling signal A based on signal CLK
Sampling signal SMPP1 and sampling signal B second sampling
Polarity of tracking signal SMPP2 and tracking error signal TE
The polarity switching signal POL for switching (reversing) is output.
The timing control circuit 13 to output the first sampling signal
Playback signal S based on the signal SMPP1 _PBTo sample
Hold the sampling signal A_PFirst sump that outputs
Ring hold circuit 31 and second sampling signal SMPP
Playback signal S based on 2_PBSample and hold,
Sampling signal B_PSecond sampling ho which outputs
Circuit 32, the first sampling and holding circuit 31,
And the output sampler of the second sampling and holding circuit 32
The original tracking error signal TE '
And the original tracking error signal
Tracking error signal TE by switching the polarity of signal TE '
And a polarity switching circuit 20 for outputting as
ing.

In this case, when the wobble pits are recorded as a pre-format, a rotation jitter or the like occurs in the recording device, and for example, as shown in FIG.
The recording position of the wobble pit of the second recording track and the second (2
When the recording position of the wobble pit of the (k + 2) th recording track is not on the same radial line but is displaced (deviation amount = Δ
x), since the sampling timing is always fixed to the pulse number of the clock signal = 3, 5 (indicated by circled numbers in the figure), when the (2k + 1) th recording track is reproduced due to the deviation of the sampling timing. In some cases, a correct tracking error signal cannot be obtained. That is, even when the (2k + 1) th recording track is the ON recording track, the tracking error signal TE
Therefore, the correct tracking error signal TE cannot be obtained.

Therefore, an object of the present invention is to easily obtain a tracking error signal even if the recording track pitch is made narrower than the reading laser beam spot diameter for high density recording, and at the same time, for tracking error signal generation tracking. It is an object of the present invention to provide a tracking error signal generation device that can generate a correct tracking error signal even when the recording position of a pit is displaced due to the recording device.

[0019]

In order to solve the above problems, according to the present invention, a recording track is formed in a spiral shape, and a data information area for recording data information and a servo control information recording area are formed in the recording track. A tracking error signal generation device for generating a tracking error signal from a reproduction signal of a sampled servo type optical disc having a servo control information area and a tracking pit used for generating a tracking error signal in the servo control information area. Therefore, the peak timing corresponding to the tracking pit of the reproduction signal is detected, and the tracking error signal is generated and output based on the reproduction signal at the peak timing.

[0020]

According to the present invention, the tracking error signal generation device detects the peak timing corresponding to the tracking pit of the reproduction signal, and generates and outputs the tracking error signal based on the reproduction signal at the peak timing.

Therefore, even if the recording position of the tracking pit is deviated due to the rotation jitter of the recording apparatus, the sampling can be performed at the correct timing, and the accurate tracking error signal can be generated.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of the reproducing apparatus.

The reproducing apparatus 10 has a decoder 11 for decoding the reproduction signal S _PB (= RF signal) of the read beam LB and outputting reproduction data D _PB , and a PLL circuit (not shown), based on the reproduction signal S _PB. A clock extraction circuit 12 that outputs a clock signal CLK, and a sampling timing signal SMP of the sampling signal A based on the clock signal CLK.
Gate signal G _A used for generating the _A, the sampling signal B
Of the gate signal G _B used to generate the sampling timing signal SMP _B and the tracking error signal TE, which outputs a polarity switching signal POL for switching (reversing) the polarity, and the peak position of the reproduction signal S _PB. The first sampling signal SM is obtained by taking the logical product of the peak timing detection circuit 14 that detects and outputs the peak detection signal PE and the peak detection signal PE and the gate signal G _A.
The first AND circuit 15 that outputs P1 and the peak detection signal P
A second AND circuit 16 which logically ANDs E and the gate signal G _B and outputs the second sampling signal SMP2, and the reproduction signal S _PB is sampled and held based on the first sampling signal SMP1 and the sampling signal A is output. First sampling and holding circuit 17 and second sampling signal SM
The reproduction signal S _PB is sampled and held based on P2,
A second sampling and holding circuit 18 that outputs a sampling signal B; a subtractor 19 that takes the difference between the sampling signals output from the first and second sampling and holding circuits 17 and 18 and outputs the original tracking error signal TE ′; A polarity switching circuit 20 for switching the polarity of the original tracking error signal TE 'and outputting it as the tracking error signal TE.

The peak timing detection circuit 14 generates and outputs a differential signal DIF of the reproduction signal SPB.
A and a zero-cross detection circuit 14B that detects a zero-cross point of the differential signal DIF and outputs a peak detection signal PE.

Next, the tracking error signal generating operation will be described with reference to FIG. First, as shown in FIG. 2A, a case where the read beam LB traces on the recording track TR _{2n + 1} will be described. In this case, it is assumed that the servo pits (PW ₁ , PW ₂ , CP) are misaligned (deviation amount: Δx) due to the rotation jitter of the recording device during wobble pit recording.

First, conventional sampling signals SMPP1 and SMPP2 (FIG. 2) corresponding to the clock signal CLK obtained when the recording track TR _2n is reproduced by the read beam LB.
Consider the case where the reproduction signal S _PB is sampled based on the timing corresponding to (c). here,
The first sampling signal SMPP1 corresponds to the rising timing of the pulse number of the clock signal CLK = 5 (shown by the circled numbers in the figure), and the second sampling signal SMPP2 the pulse number of the clock signal CLK = 3 (the circled numbers in the figure) It is assumed to correspond to the rising timing of ().

In this case, as shown by the "+" mark on the curve of the reproduced signal S _PB in FIG. 4B, the wobble pit PW ₁ '
The reproduction signal S _PB is sampled at the timing corresponding to the recording position of the wobble pit PW ₁ when the peak corresponding to is to be sampled, and the correct tracking error signal TE cannot be obtained.

Therefore, in this embodiment, the differentiating circuit 1
4A and the zero-cross detection circuit 14B, the zero-cross point of the differential signal of the reproduction signal S _PB , that is, the reproduction signal S _PB.
The peak of _PB is detected, and the first AND circuit 15 or the second A circuit
A gate signal corresponding to a time range in which a desired wobble pit may be detected by the ND circuit 16 is generated,
The reproduction signal SPB is sampled assuming that the detection timing of the peak existing in the time range is the sampling timing of the desired wobble pit.

That is, the timing at which the wobble pits should ideally exist (in the above example, the clock signal CLK
Of the peak detection signal PE detected while the gate signal is generated while the gate signal is generated during the "H" level. Playback signal S at timing
_The tracking error signal TE is generated by sampling _PB .

Specifically, the timing control circuit 13 is
Based on the clock signal CLK, a gate signal G _A corresponding to a time range of 1 clock before and after the rising timing of pulse number = 5 and a gate signal corresponding to a time range of 1 clock before and after the rising timing of pulse number = 5 G _B is generated and the gate signal G _A is supplied to the first AND circuit 15
And outputs the gate signal G _B to the second AND circuit 16.

On the other hand, the differentiating circuit 14A differentiates the reproduced signal S _PB and outputs the differentiating signal DIF to the zero-cross detecting circuit 14B. In response to this, the zero-cross detecting circuit 14B detects the zero-cross point of the differentiating signal DIF and detects the peak detecting signal. The PE is output to the first AND circuit 15 and the second AND circuit 16.

The first AND circuit 15 has a peak detection signal P.
The first sampling signal which is the logical product of E and the gate signal G _A and corresponds to the peak position of the wobble pit PW ₁ ′.
Outputs SMP1. Further, the second AND circuit 16 takes the logical product of the peak detection signal PE and the gate signal G _A and outputs the second sampling signal SMP2 corresponding to the peak position of the wobble pit PW ₂ .

As a result, the first sampling and holding circuit 17 samples and holds the reproduction signal S _PB based on the first sampling signal SMP1, and the wobble pit P
The sampling signal A corresponding to the peak level of W ₁ 'is output. In addition, the second sampling and holding circuit 18
Is a reproduction signal S _PB based on the second sampling signal SMP2.
Is sampled and held, and a sampling signal B corresponding to the peak level of the wobble pit PW ₂ is output.

Accordingly, the subtractor 19 obtains the original tracking error signal TE 'by the following equation and outputs it. TE ′ = A−B This original tracking error signal TE ′ is, for example, when the read beam LB is in the on-track state on the recording track TR _{2n + 1} being reproduced, The signal levels become equal and the original tracking error signal TE '= 0.

Further, the read beam LB is the recording track TR.
_When shifted to the _{2n + 2} side, the reading peak of the sampling signal B is in the on-track state (see FIG. 2B).
Will be smaller than On the other hand, the sampling signal A has a read peak larger than that in the on-track state (see FIG. 2B). As a result, the original tracking error signal TE 'becomes TE' = AB> 0, and it is possible to detect the deviation of the reading beam LB to the recording track TR _{2n + 2} side and the deviation amount.

Further, the read beam LB is the recording track TR _2n.
When it is shifted to the side, the sampling signal B has a read peak size larger than that in the on-track state (see FIG. 2B). On the other hand, the sampling signal A has a read peak size on track (see FIG. 4B).
Will be smaller than As a result, the original tracking error signal TE 'becomes TE' = AB <0, and it is possible to detect the deviation of the reading beam LB toward the recording track TR _2n side and the deviation amount.

By the way, in this embodiment, since wobble pits are thinned out for recording in order to perform high density recording, recording tracks of odd numbers (2n + 1, 2n + 3, ...) And even numbers (2n). , 2n + 2, ...) Recording tracks (recording tracks in which wobble pits are formed during recording) have the polarity of the original tracking error signal TE ′ inverted. Therefore, the polarity switching signal PO from the timing control circuit 13
A tracking error signal obtained from an optical disk in which wobble pits are provided for all recording tracks by inverting the polarity of an original tracking signal TE 'obtained by a recording track having an odd number by L by a polarity switching circuit 20 as in the prior art. A tracking error signal TE having the same polarity as Specifically, when the read beam LB is scanning on the even-numbered recording tracks, TE = TE ′, and when the read beam LB is scanning on the odd-numbered recording tracks, TE = -TE '

Therefore, even when the recording position of the servo pit, especially the tracking error signal generating pit such as the wobble pit, which is caused by the rotation jitter of the recording device at the time of recording the wobble pit on the optical disc, is correct. It becomes possible to obtain the tracking error signal TE. Further, the number of recording tracks provided with wobble pits is half of all recording tracks, and the recording density can be improved. Further, since the tracking error signal can be obtained without being affected by the wobble pits of the adjacent recording tracks, tracking control can be easily performed even at a narrow recording track pitch.

In the above embodiments, the wobble pits are provided in the even-numbered recording tracks, but it is also possible to provide the wobble pits in the odd-numbered recording tracks. In this case, it is necessary to reverse the polarity switching of the polarity switching circuit 20 to the case described above.

Further, in the above description, the case where the wobble pit is used as the tracking pit has been described, but as shown in FIG. 3A, the recording track is formed in one spiral curve shape. The present invention can also be applied to the case where the tracking pits TP are formed on the different radial lines and on each recording track between a plurality of adjacent (4 in FIG. 3A) recording tracks. In this case, it is necessary to change the generation timing of the gate signal for each traced recording track.

Further, in the above description, the case where the recording tracks are formed in the shape of one spiral curve has been described. For example, as shown in FIG. 3B, three parallel recording tracks are formed. Is formed in a spiral curve shape (so-called three spiral structure), and the central recording track TRm
_The present invention can also be applied to the case where the tracking pit TP is formed only in the area ₂ .

[0042]

According to the present invention, the actual recording position of the tracking pit on the optical disk is detected, and the tracking error signal is generated based on the reproduction signal corresponding to the recording position. As a result, even if the recording position of the tracking pit is deviated, the sampling can be performed at the correct timing, and the tracking error signal can be easily and reliably generated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical disc reproducing apparatus.

FIG. 2 is a diagram illustrating generation of a tracking error signal.

FIG. 3 is a diagram illustrating another embodiment of the present invention.

FIG. 4 is a diagram illustrating a recording format of a sampled servo system.

FIG. 5 is a diagram illustrating a recording format of a conventional servo area.

FIG. 6 is a diagram illustrating conventional tracking error detection by wobble pits.

FIG. 7 is a diagram illustrating a conventional problem.

FIG. 8 is a diagram illustrating a proposal for solving a conventional problem.

FIG. 9 is a block diagram showing a schematic configuration of a playback device corresponding to the proposal of FIG.

FIG. 10 is a diagram for explaining points to be improved in the proposal of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Reproducing apparatus 11 ... Decoder 12 ... Clock extraction circuit 13 ... Timing control circuit 14 ... Peak detection circuit 14A ... Differentiation circuit 14B ... Zero cross detection circuit 15 ... 1st AND circuit 16 ... 2nd AND circuit 17 ... 1st sampling hold circuit 18 ... Second sampling and holding circuit 19 ... Subtractor 20 ... Polarity switching circuit _SPB ... Reproduction signal CP ... Clock pit DK ... Optical disk LB ... Read beam DIF ... Differentiation signal PE ... Peak detection signal TE ... Tracking error signal TE '... Original tracking Error signal

Claims (2)

[Claims] 1. A recording track is formed, and a data information area for recording data information and a servo control information area for servo control information recording are provided in the recording track, and a tracking error is present in the servo control information area. A tracking error signal generation device for generating a tracking error signal from a reproduction signal of a sampled servo type optical disc provided with a tracking pit used for signal generation, which detects a peak timing corresponding to the tracking pit of the reproduction signal. A tracking error signal generation device for generating and outputting a tracking error signal based on the reproduction signal at the peak timing. 2. The tracking error signal generating device according to claim 1, wherein a differential signal generating means for outputting a differential signal of the reproduction signal, and a zero cross detecting means for detecting a zero cross point of the differential signal and outputting a zero cross detection signal. And a gate signal generation means for outputting a gate signal having a predetermined time width including the detection timing of the tracking pit, a logical product of the zero-cross detection signal and the gate signal, and a sampling timing signal corresponding to the peak timing. Timing signal generating means, sampling means for sampling the reproduction signal based on the sampling timing signal and outputting a sampling signal, and a tracking error signal generating means for generating and outputting a tracking error signal based on the sampling signal. A tracking error signal generation device comprising: a step.