JP4360302B2 - Disc playback device, sync pattern detection method, disc rotation control method - Google Patents

Description

  The present invention relates to a disk playback apparatus for a disk recording medium such as an optical disk, a synchronization pattern detection method and a disk rotation control method that can be employed in the disk playback apparatus.

JP 2000-187946 A

As a technique for recording / reproducing digital data, optical disks (including magneto-optical disks) such as CD (Compact Disk), MD (Mini-Disk), and DVD (Digital Versatile Disk) are used as recording media. There is data recording technology.
The optical disc includes a read-only type in which data is recorded with embossed pits as known as CD, CD-ROM, DVD-ROM, and the like, MD, CD-R, CD-RW, DVD-R. , DVD-RW, DVD + RW, DVD-RAM, and the like can record user data. In the recordable type, data can be recorded by utilizing a magneto-optical recording method, a phase change recording method, a dye film change recording method, or the like. The dye film change recording method is also called a write-once recording method, and can be recorded only once and cannot be rewritten. On the other hand, the magneto-optical recording method and the phase change recording method can rewrite data and are used for various purposes such as recording of various content data such as music, video, games, application programs and the like.
In recent years, a high-density optical disk called a Blu-ray Disc has been developed, and the capacity has been significantly increased.

By the way, in a reproduction-only optical disk such as a CD-ROM or DVD-ROM, rotation control of the spindle motor is performed using information obtained from a reproduction RF signal read from the disk.
Among them, there is a method using a frame synchronization pattern recorded on an optical disc. The frame synchronization pattern detection methods are roughly classified into the following two types.
1. A PLL is applied to the RF signal, and a frame synchronization pattern is detected by pattern matching from a data string obtained by sampling the RF signal using a PLL clock (a clock synchronized with the RF signal), and synchronization protection is performed.
2. The RF signal is sampled with a fixed clock (clock that is asynchronous to the RF signal) without applying a PLL to the RF signal, and the longest T is detected from the data string, for example, the longest T is detected as a frame synchronization pattern. There is a method to perform synchronization protection according to. T indicates the length of the reproduced mark, pit, or space on the basis of the channel bit. A method in which this method is further devised is disclosed in Patent Document 1 described above.

However, in the above method 2, due to the rotational fluctuation of the disk, a data pattern having a long T is erroneously detected as a frame synchronization pattern, and the synchronization protection performance is deteriorated, so that the spindle control stability deteriorates. was there.
This will be described with reference to FIGS.
FIG. 7 shows a configuration for detecting a unique pattern as a synchronous pattern, and an input RF data string is a data string obtained by sampling an RF signal with a fixed asynchronous clock.
For the RF data string, first, the window processor 51 extracts a data string only for the period specified by the window signal Wd, and the T length is compared with the threshold thUP by the threshold comparison processor 52 in the extracted data string period. Is done. The threshold thUP is stored in the threshold register 53 and supplied to the threshold comparison processing unit 52.
The comparison result in the threshold value comparison processing unit 52 becomes a unique pattern detection timing signal DUP, that is, a frame synchronization pattern detection signal.

This process is shown in FIG. FIG. 8A shows the length of T of the pattern due to pits or spaces that appear sequentially in the RF data string.
The unique pattern UP as the frame synchronization pattern appears periodically as the longest T pattern as shown in the figure. For example, in the CD system, the 11T / 11T (pit or mark / space) pattern is the synchronization pattern, and in the Blu-ray disc, the 9T / 9T pattern is the synchronization pattern.
In order to extract such a unique pattern UP, first, a pattern in a period during which the unique pattern UP cannot be generated is excluded by the window signal Wd in FIG. 8B as a unique pattern detection window.
For example, as shown as the pattern P2 in FIG. 8A, there is a T data pattern close to the unique pattern UP, which may be erroneously detected as the unique pattern UP. By eliminating patterns outside the period of Wd, erroneous detection due to the pattern P2 is prevented.
Next, the threshold value comparison processing unit 52 compares the fixed length thUP set for detecting the unique pattern UP with the T length of each pattern. The threshold value thUP is indicated by a broken line in FIG.
If the sampling pattern length of the unique pattern UP from the RF data string is Lup,
Lup> thUP
The unique pattern UP is detected according to the conditions.
FIG. 8C shows a synchronization pattern detection signal DUP obtained as a result of the comparison process.

However, when the rotational frequency of the disk fluctuates, the pattern length of the RF data string sampled with a fixed clock fluctuates in proportion. The one-dot chain line in FIG. 8 (a) shows the transition of the rotational frequency of the disk. When the particular pattern UP is particularly noted, it can be seen that the detected T length varies in proportion to the rotational frequency. .
That is, the T length is long when the disk rotation is low, and the T length is short when the disk is high.
Here, if the threshold thUP is fixed, particularly when the disk rotation is slow, the threshold thUP does not become an appropriate value, and a relatively long T data pattern is mistaken as a unique pattern UP. Cheap. In the example of FIG. 8A, the pattern P1 has a T length exceeding the threshold thUP, and this pattern P1 has a period that is not excluded by the window signal Wd. , It will be detected as a synchronization pattern.

In order to avoid such erroneous detection of the synchronization pattern, the threshold thUP may be set high. However, when the disk rotation speed becomes high (for example, the rightmost unique pattern UP in FIG. 8A). Considering this, the threshold thUP cannot be set too high. That is, it is necessary to set the threshold thUP as shown in FIG. 8A as a value that covers the assumed rotation frequency fluctuation. Therefore, there is a possibility that a relatively long T data pattern is erroneously detected as a synchronization pattern. is there.
Further, the above Patent Document 1 discloses a technique for varying the detection window period by the window signal Wd, but even if this technique is applied, a long T data pattern is generated in a period that is not excluded by the window signal Wd. Sometimes the possibility of false detection remains.
Depending on the erroneous detection of the synchronization pattern, the synchronization is lost and the stability of the rotation speed control of the spindle motor is thereby impaired, which causes a decrease in the reproduction operation performance.

  Therefore, an object of the present invention is to prevent erroneous detection of a synchronization pattern and to realize stable synchronization protection and spindle control.

A disk reproducing apparatus according to the present invention comprises a spindle means for rotationally driving a disk recording medium, a reading means for reading an information signal from the disk recording medium, an information signal read by the reading means being sampled by an asynchronous clock, and a data string A data string generating means for outputting the data, a synchronization pattern detecting means for detecting a synchronization pattern from the data string supplied from the data string generating means, and a timing for detecting a timing interval of the synchronization pattern detected by the synchronization pattern detecting means An interval detection unit; and a spindle control unit that performs rotation control of the spindle unit based on a detection timing of the synchronization pattern by the synchronization pattern detection unit. The synchronization pattern detection means detects the synchronization pattern by comparing the pattern length appearing in the data string of the information signal with a threshold value variably set based on the timing interval detected by the timing interval detection means.
Further, it further comprises window generating means for generating a window signal based on the timing interval detected by the timing interval detecting means, and the synchronization pattern detecting means is configured to detect the information signal within a period defined by the window signal. The pattern length appearing in the data string is compared with the threshold value, and the synchronization pattern is detected based on the comparison result.
The synchronization pattern detection means sets first and second threshold values based on the timing interval detected by the timing interval detection means, and sets the pattern length appearing in the data string of the information signal to the first and second values. The synchronization pattern is detected by comparing with the threshold value.

  Further, the disk reproducing apparatus of the present invention comprises a spindle means for rotationally driving a disk recording medium, a reading means for reading an information signal from the disk recording medium, and an information signal read by the reading means is sampled by an asynchronous clock, By comparing the data string generating means for outputting as a data string and the pattern length appearing in the data string supplied from the data string generating means with a threshold value variably set according to the rotational speed of the disk recording medium, Synchronization pattern detecting means for detecting.

The synchronization pattern detection method of the present invention includes a synchronization pattern detection step of detecting a synchronization pattern by comparing a pattern length appearing in a data string obtained by sampling an information signal read from a disk recording medium with an asynchronous clock with a threshold value. A timing interval detection step for detecting a timing interval of the synchronization pattern detected in the synchronization pattern detection step, and a threshold setting step for variably setting the threshold based on the timing interval detected in the timing interval detection step. Prepare.
In addition, a window generation step for generating a window signal based on the timing interval detected in the timing interval detection step is further provided. In the synchronization pattern detection step, the information signal is detected within a period defined by the window signal. The pattern length appearing in the data string is compared with the threshold value, and the synchronization pattern is detected based on the comparison result.
In the threshold setting step, the first and second thresholds are set based on the timing interval detected in the timing interval detection step. In the synchronization pattern detection step, the pattern length appearing in the data string of the information signal is A synchronization pattern is detected by comparing with the first and second threshold values.

  In the synchronous pattern detection method of the present invention, the pattern length appearing in the data string obtained by sampling the information signal read from the disk recording medium with the asynchronous clock is variably set according to the rotational speed of the disk recording medium. A synchronization pattern is detected by comparing with a threshold value.

  The disk rotation control method of the present invention includes a synchronization pattern detection step for detecting a synchronization pattern by comparing a pattern length appearing in a data string obtained by sampling an information signal read from a disk recording medium with an asynchronous clock with a threshold value. A timing interval detection step for detecting a timing interval of the synchronization pattern detected in the synchronization pattern detection step; a threshold setting step for variably setting the threshold based on the timing interval detected in the timing interval detection step; A spindle control step for controlling the rotation of the disk recording medium based on the detection timing of the synchronization pattern in the synchronization pattern detection step.

  That is, according to the present invention, the synchronization pattern is detected by comparing the pattern length appearing in the data string with respect to the information signal read from the disk recording medium. A pattern length appearing in a data string obtained by sampling an information signal with an asynchronous clock varies depending on the disk rotation frequency. A threshold for comparing the pattern length is variably set based on a timing interval of the synchronous pattern. The timing interval of the synchronization pattern is in accordance with the disk rotation frequency (disk rotation speed), that is, the threshold value is varied in accordance with the disk rotation frequency.

According to the present invention, a synchronization pattern is detected by comparing a pattern length appearing in a data string obtained by sampling an information signal read from a disk with an asynchronous clock with a threshold, and the threshold is a timing interval of the synchronization pattern. It is set to be variably set according to.
As a result, the threshold value fluctuates in accordance with the fluctuation of the pattern length according to the disk rotation frequency. Therefore, the threshold value is an appropriate value for determining the unique pattern length as the synchronization pattern regardless of the disk rotation frequency. Become. For this reason, erroneous detection of the synchronization pattern can be reduced, and there is an effect that stable synchronization protection and spindle rotation control can be realized.

In addition, excluding the pattern other than the detection window period by the window signal from the synchronization pattern detection further reduces the erroneous detection of the synchronization pattern.
Further, the first and second threshold values are set based on the timing interval of the synchronization pattern, and the synchronization pattern is detected by comparing the pattern length appearing in the data string of the information signal with the first and second threshold values. By doing so, erroneous detection of the synchronization pattern can be reduced. For example, if a pattern length between the first threshold value and the second threshold value is detected as a synchronization pattern, even if a pattern longer than the synchronization pattern occurs due to a defect or the like, it can be eliminated.

Hereinafter, a disk reproducing apparatus according to an embodiment of the present invention will be described.
FIG. 1 shows a frame synchronization pattern detection and spindle rotation control system in the disk reproducing apparatus of this example.
Of course, as a disk playback device, the information signal (RF signal) read processing circuit section read from the disk, the interface with external equipment, the servo drive system such as tracking / focus / slide, and the servo control system are controlled. A system controller and other circuit units and mechanisms are provided, but illustration and description thereof are omitted.

The disk 90 is loaded on a turntable (not shown) and is rotationally driven by the spindle motor 10 during the reproducing operation.
Then, information recorded as a pit row in the track on the disk 90 is read by the optical pickup (optical head) 11.
In the pickup 11, a laser diode serving as a laser light source, a photodetector for detecting reflected light, an objective lens serving as an output end of the laser light, and a laser recording light are irradiated onto the disk recording surface via the objective lens. An optical system for guiding the reflected light to the photodetector is formed.

Reflected light information obtained by irradiating the disk 90 with laser is detected by a photodetector and supplied to the RF amplifier 1 as a signal read from the disk 90 (electrical signal corresponding to the amount of received light).
The RF amplifier 1 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, a filter, an auto gain control circuit, a waveform equalizer, and the like corresponding to output currents from a plurality of light receiving elements as a photodetector, and reproduces data. The necessary signal is generated. For example, a reproduction RF signal corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, and the like are generated.
Note that the RF amplifier 1 may be provided in the pickup 11.

The binarization circuit 2 samples the reproduction RF signal from the RF amplifier 1 to obtain binary RF data. At this time, a fixed frequency asynchronous clock, that is, a clock not synchronized with the RF signal is used as the sampling clock. As a condition for the sampling clock, since it is necessary to obtain the length of the pattern from the RF data string, the average frequency needs to be known, and it is desirable that the variation in frequency is small.
Then, as shown in FIG. 2, the binarization circuit 2 slices the input RF signal at a predetermined slice level, binarizes it, samples it with the sampling clock, and converts it into an RF data string.

In the following, T refers to the length of a mark (or pit) or space when the length of a reproduced mark or pit or space is sampled with a synchronous clock applied with a PLL. The pattern refers to a mark (pit) / space or a combination of them as one unit, and the pattern length refers to the total T length of the pattern.
The sampling pattern length refers to the total number of samples when the pattern is sampled with the sampling clock.

The RF data string obtained by the binarization circuit 2 is supplied to a reproduction processing system (not shown) for reproduction signal processing, and is also supplied to the unique pattern detection units 3 and 4 shown in the figure.
The unique pattern detection unit (HUNT) 3 detects a unique pattern in the RF data string input from the binarization circuit 2 in a state where synchronization protection is not applied. This unique pattern is a unique pattern in the frame synchronization pattern included in the reproduction RF signal. Then, a detection timing signal DupH corresponding to the detection of the unique pattern is output.

The unique pattern detection unit (SYNC) 4 detects a unique pattern in the RF data string input from the binarization circuit 2 in a state where synchronization protection is applied. In addition to the RF data string, a window signal Wd from the window generation unit 8 and a unique pattern interval signal CTm from the unique pattern interval holding unit 7 are used as an input for detection.
And the unique pattern detection part 4 outputs the detection timing signal DupS according to the detection of the unique pattern similarly to the unique pattern detection part 3.

The detection result selector 5 detects the detection timing of the unique pattern detection unit 3 based on the synchronization state signal H / S indicating the synchronization protection state of the unique pattern interval counter and synchronization protection unit 6 (hereinafter abbreviated as interval counter / synchronization protection unit 6). The signal DupH or the detection timing signal DupS of the unique pattern detection unit 4 is selected.
That is, the detection timing signal DupH is selected when the synchronization state of the interval counter / synchronization protection unit 6 is the HUNT state (synchronization not established state), and the detection timing signal when the synchronization state is the SYNC state (synchronization established state). Select DupS. The selected detection timing signal DupH or DupS is supplied to the interval counter / synchronization protection unit 6.

The interval counter / synchronization protection unit 6 has a unique pattern interval counter that counts unique pattern intervals with a clock, and a synchronization protection function using the value of the unique pattern interval counter and a unique pattern detection timing signal.
For example, here, the synchronization protection function has a two-state state machine. These are the HUNT state and the SYNC state, respectively.
The HUNT state is a state where synchronization is not established. In this case, synchronization is attempted using the detection result selected by the detection result selector 5, that is, the detection timing signal DupH from the unique pattern detection unit 3. As a result, when synchronization is established, the state enters a synchronization protected state, that is, a SYNC state, and a synchronization protection operation is performed.
The interval counter / synchronization protection unit 6 measures the unique pattern interval with the unique pattern interval counter that is reset / started by the detection timing signal DupH or DupS, and calculates the count value CT (that is, a value indicating the unique pattern interval). The data is output to the unique pattern interval holding unit 7 and the window generating unit 8. The count value CT indicating the unique pattern interval can also be said to be rotational speed information of the disk 90.
Further, the interval counter / synchronization protection unit 6 generates a unique pattern timing signal TMup from the unique pattern interval counter and outputs it to the spindle control circuit 9 together with the synchronization state signal H / S.
The unique pattern timing signal TMup is a signal that indicates the timing stably for each frame by complementing the timing when the unique pattern cannot be detected due to disturbance in a state where synchronization protection is established. That is, the unique pattern timing signal TMup is a signal as appropriate rotation speed information for spindle control.

The unique pattern interval holding unit 7 holds the unique pattern interval value CT output from the unique pattern interval counter. The retained unique pattern interval value CTm is output to the unique pattern detection unit 3 and the spindle control circuit 9.
The window generator 8 generates a window signal Wd from the value CT of the unique pattern interval counter and outputs it to the unique pattern detector 4. The window signal Wd is for preventing the unique pattern detection unit 4 from erroneously detecting the unique pattern.
The spindle controller 9 inputs the unique pattern timing signal TMup, the synchronization state signal H / S from the interval counter / synchronization protection unit 6, the unique pattern interval value CTm from the unique pattern interval holding unit 7, and the like. By controlling the rotation of the spindle motor 10, the disk 90 is rotated so that the pickup 11 has an appropriate linear velocity.

In such a configuration, the operation of the unique pattern detection unit 3 is as follows.
As described above, the unique pattern detection unit 3 detects a unique pattern in a state where synchronization protection is not applied.
FIG. 3 shows an example of unique pattern detection from RF data. As the rotational frequency of the disk fluctuates as shown by the one-dot chain line in FIG. 3A, the detected sampling pattern length fluctuates in proportion.
In the unique pattern detection unit 3, the threshold value th set to a fixed value as shown in FIG. 3A is compared with the pattern length of the input RF data sequence, and a pattern having T exceeding the threshold value th is obtained. The detection timing signal DupH is output as the unique pattern UP as shown in FIG.
However, if the unique pattern UP is to be detected with the fixed threshold value th, it is necessary to determine the threshold value th in consideration of the rotational frequency fluctuation of the disk 90. If the threshold value th that covers the assumed rotation frequency variation as shown by the broken line in FIG. 3A is used, T of the data pattern that is not the unique pattern UP, such as the patterns P1 and P2, is erroneously detected as a unique pattern (FIG. 3). (Signal marked with ☆ in 3 (b)).
However, the detection timing signal DupH from the unique pattern detection unit 3 is used only during a short HUNT state period (for example, several frames) until synchronization is established by the interval counter / synchronization protection unit 6 and the synchronization protection state is established. Therefore, even if there is a false detection as shown in FIG. 3B, there is no practical problem.

Next, the operation of the unique pattern detection unit 4 will be described. As described above, the unique pattern detection unit 4 detects the unique pattern UP in a state where synchronization protection is applied.
Here, as described with reference to FIG. 7, if the unique pattern UP is detected using the window signal Wd and the threshold value thUP as a fixed value, a false detection is caused by the variation in the pattern length corresponding to the variation in the rotational frequency of the disk 90. Is likely to occur.
As described above, in the unique pattern detection unit 3 functioning in the HUNT state, there is no problem in some erroneous detections. However, in the unique pattern detection unit 4 that outputs the timing signal DupS used in the SYNC state, the unique pattern UP is erroneously detected. We must prevent it as much as possible. This is because an erroneous detection of the unique pattern UP becomes a disturbance in the synchronization protection state, which causes a loss of synchronization and the spindle rotation control becomes unstable.

Therefore, the unique pattern detection unit 4 of this example is configured as shown in FIG. 4 so that erroneous detection of the unique pattern UP can be reduced.
The RF data string from the binarization circuit 2 is input to the window processing unit 41 in the unique pattern detection unit 4. The window processing unit 41 eliminates a false unique pattern from the input RF data string using the synchronization protection window signal Wd generated by the window generation unit 8.
Further, the threshold value comparison processing unit 42 uses the variable threshold value thL calculated by the unique pattern detection threshold value generation unit 44 to eliminate the false unique pattern based on the sampling pattern length threshold value.
At this time, in order to calculate the threshold value thL in the unique pattern detection threshold value generation unit 44, the reference calculation unit 45 first inputs the unique pattern interval value CTm from the unique pattern interval holding unit 7, and uses the interval value CTm as the original value. The reference value Lref of the sampling pattern length of the unique pattern is calculated. A calculation formula is shown.
Lref = Lint × (Lup_cent / Lint_cent)
here,
Lint: number of samples with sampling clock of unique pattern interval Lup_cent: sampling pattern length of unique pattern when disk is rotating at frequency Fx Lint_cent: sampling clock of UP interval when disk is rotating at frequency Fx This is the number of samples.
Note that the frequency Fx is arbitrary. This is introduced for convenience in order to obtain the unique pattern length Lup_cent and the unique pattern interval Lint_cent at the same frequency.

Next, the unique pattern detection threshold value generation unit 44 calculates a variable threshold value thL. The calculation formula is as follows.
thL = Lref−OFL
Here, OFL is an offset that determines a threshold value for determining the unique pattern UP.
That is, a value obtained by subtracting the value of the offset OFL from the reference value Lref calculated from the unique pattern interval becomes the threshold thL for identifying the unique pattern.
The offset OFL is stored in the offset register 43 and supplied to the unique pattern detection threshold value generator 44 for the above calculation.

Then, the threshold comparison processing unit 42 eliminates false unique patterns under the following conditions.
Lup> thL
Here, Lup is the sampling pattern length of the unique pattern UP from the RF data string.
In the threshold comparison processing unit 42, if this Lup> thL is established, the relationship between the sampling pattern length of the unique pattern UP and the number of samplings of the unique pattern interval is appropriate. Therefore, the unique pattern timing is adopted, and Lup> thL is established. If not, it is judged as a false unique pattern and eliminated. The result is output as a unique pattern UP timing signal DupS.

The processing of the above unique pattern detection unit 4 is shown in FIG.
FIG. 5A shows the length of the pattern T due to pits or spaces that appear sequentially in the RF data string.
The unique pattern UP as the frame synchronization pattern appears periodically as the longest T pattern as illustrated.
For this reason, first, T in a period in which the unique pattern UP cannot be generated is eliminated by the window signal Wd in FIG. 5B as the unique pattern detection window.
For example, as shown as a pattern P2 in FIG. 5A, there is a T data pattern close to the unique pattern UP. However, since this is a period outside the window, it is excluded by the window processing unit 41.
Next, the threshold value comparison processing unit 42 compares the threshold value thL variably set as described above with the T length of each pattern in order to detect the unique pattern UP. The threshold thL is set by subtracting the offset OFL from the reference value Lref calculated from the unique pattern interval value CTm. Accordingly, the threshold value thL is changed as indicated by the broken line in accordance with the change in the disk rotation frequency of the one-dot chain line.
As shown in the figure, the reference value Lref is the T length of the immediately preceding unique pattern, and the threshold value thL indicated by the broken line is set by subtracting the offset OFL from the reference value Lref.
Then, the threshold value thL is an appropriate value for identifying the unique pattern UP and other data patterns according to the disk rotation frequency.
Therefore, for example, as shown as a pattern P1 in FIG. 5A, a relatively long T data pattern that cannot be eliminated by the window processing unit 41 and is a data pattern within the window can be eliminated by the threshold thL. .
As a result, as shown in FIG. 5C, for example, a timing signal DupS that does not erroneously detect the patterns P1 and P2 as the unique pattern UP is output.

Note that the offset OFL set in the offset register 43 may be determined as appropriate in consideration of the relationship between the unique pattern UP and other data patterns and the fluctuation of the sampling result caused by sampling with the asynchronous clock in the binarization circuit 2.
For example, in the DVD system, the length of the unique pattern UP is 14T, and the longest data pattern is 11T. At this time, if the frequency of the sampling clock is the same as the frequency of the channel clock of the RF signal, it is considered appropriate to have a margin of about one clock in consideration of fluctuations caused by sampling. Then, the offset OFL = −1 clock, that is, thL = Lref−1 may be set.
For example, in the Blu-ray Disc system, the unique pattern UP is 9T / 9T (in this case, the pattern length is 18T), and the longest data pattern is 8T / 8T (pattern length is 16T). In such a case as well, if it is considered appropriate to give a margin of one clock in consideration of fluctuations caused by sampling, etc., if offset OFL = −1 clock, that is, thL = Lref−1. Good.

As described above, the unique pattern detection unit 4 variably sets the threshold thL for comparing pattern lengths based on the unique pattern interval value CTm. Since the unique pattern interval value CTm is in accordance with the disk rotation frequency, the threshold thL is variable in accordance with the fluctuation of the disk rotation frequency. As a result, it is possible to output the timing signal DupS in which the false unique pattern is appropriately excluded.
By eliminating the false unique pattern in the timing signal DupS, the synchronization protection is stabilized, and the unique pattern timing signal TMup to the spindle controller 9 is also stabilized, so that stable rotation control of the spindle motor 10 is performed. be able to.

By the way, in the above embodiment, it can be said that the unique pattern detection unit 4 uses the lower limit of the T length as the unique pattern UP as the threshold thL. That is, a T pattern longer than the threshold thL is set as a unique pattern UP in the frame synchronization pattern.
However, for example, due to the influence of defects (scratches and dirt) on the disk 90, a long T abnormal pattern (T pattern longer than the frame synchronization pattern) that is impossible on the format may occur.
When such a long T abnormal pattern occurs in the window, it is erroneously detected as a unique pattern only by comparing with the threshold thL that is the lower limit of the T length.
In order to eliminate such erroneous detection of an abnormal pattern, the unique pattern detection threshold value generation unit 44 sets the second threshold thU as the upper limit of the unique pattern UP in addition to the first threshold thL as the lower limit, It is appropriate for the threshold comparison processing unit 42 to eliminate false unique patterns using both the thresholds thL and thU.

For example, the offset register 43 stores an offset OFU for calculating the second threshold thU in addition to the offset OFL.
Then, the unique pattern detection threshold value generation unit 44 sets the first threshold value thL to thL = Lint × (Lup_cent / Lint_cent) −OFL as described above.
= Lref-OFL
And calculating the second threshold thU as
thU = Lint × (Lup_cent / Lint_cent) + OFU
= Lref + OFU
Calculate as
In the threshold comparison processing unit 42,
thL <Lup <thU
Only UP candidates that satisfy the above are adopted as unique patterns UP.

FIG. 6 shows an operation of eliminating the false unique pattern with such threshold values thL and thU.
As indicated by broken lines in FIG. 6A, the threshold values thL and thU are variably set according to the disk rotation frequency indicated by the alternate long and short dash line.
Then, assume that an abnormal pattern has occurred within the window period, such as pattern P3. However, since this abnormal pattern P3 does not satisfy the condition of Lup <thU, it is eliminated by the threshold comparison processing unit 42, and as a result, the timing signal DupS from which the false unique pattern is eliminated is output as shown in FIG. 6C. Will be able to.

Note that the offset OFU may be determined as appropriate in consideration of the relationship between the unique pattern UP and other data patterns and the fluctuation of the sampling result due to sampling with an asynchronous clock, as with the offset OFL.
Similar to the above example, the length of the unique pattern UP is 14T in the DVD, and in that case, if it is appropriate to give a margin of about 2 clocks in consideration of fluctuations due to sampling, etc., the offset is offset. OFU = + 2 clocks.
In addition, even when the unique pattern UP is 9T / 9T (pattern length is 18T), if it is considered appropriate to allow a margin of about 2 clocks in consideration of variation due to sampling, The offset OFU = + 2 clocks.

Although the embodiment has been described above, the present invention is not limited to the configuration of the above example, and various modifications can be considered. For example, an example in which the window generation unit 8 and the window processing unit 41 are not provided is also conceivable.
Further, the present invention can be applied not only to a disk reproducing apparatus but also to a disk recording / reproducing apparatus.

It is a block diagram of the principal part of the disc reproducing | regenerating apparatus of embodiment of this invention. It is explanatory drawing of the binarization process of embodiment. It is explanatory drawing of the unique pattern detection operation | movement in the HUNT state of embodiment. It is a block diagram of the unique pattern detection part (SYNC) of embodiment. It is explanatory drawing of the unique pattern detection operation | movement in the SYNC state of embodiment. It is explanatory drawing of the unique pattern detection operation | movement using the 1st, 2nd threshold value of embodiment. It is a block diagram of the conventional unique pattern detection part. It is explanatory drawing of the conventional unique pattern detection operation | movement.

Explanation of symbols

1 RF amplifier, 2 binarization circuit, 3 unique pattern detection unit (HUNT), 4 unique pattern detection unit (SYNC), 5 detection result selector, 6 interval counter / synchronization protection unit, 7 unique pattern interval holding unit, 8 window Generation unit, 9 Spindle control unit, 10 Spindle motor, 11 Pickup, 41 Window processing unit, 42 Threshold comparison processing unit, 43 Offset register, 44 Unique pattern detection threshold value generation unit, 45 Reference calculation unit

Claims (5)

Spindle means for rotationally driving the disk recording medium;
Reading means for reading an information signal from the disk recording medium;
A data string generating means for sampling the information signal read by the reading means with a fixed-frequency asynchronous clock and outputting it as a data string;
Synchronization pattern detection means for detecting a synchronization pattern from the data string supplied from the data string generation means;
Timing interval detection means for detecting the timing interval of the synchronization pattern detected by the synchronization pattern detection means;
Spindle control means for controlling rotation of the spindle means based on the detection timing of the synchronization pattern by the synchronization pattern detection means,
The synchronization pattern detection means includes
A first threshold in which a pattern length appearing in the data string that changes in accordance with the rotational frequency of the disk recording medium is shorter than a pattern length of the synchronization pattern detected at the immediately preceding detection timing by a first offset length; A disk reproducing apparatus that detects a synchronization pattern when the value is between a second threshold value that is longer than the pattern length of the synchronization pattern detected at the timing by a second offset length.   2. The disc reproducing apparatus according to claim 1, further comprising window generating means for generating a window signal based on the timing interval detected by the timing interval detecting means. A synchronization pattern detection step of detecting a synchronization pattern by comparing a pattern length appearing in a data string obtained by sampling an information signal read from a disk recording medium with a fixed-frequency asynchronous clock with a threshold;
A timing interval detection step for detecting a timing interval of the synchronization pattern detected in the synchronization pattern detection step;
A threshold setting step for variably setting the threshold based on the timing interval detected in the timing interval detection step,
The threshold value is a first threshold value that is shorter than the pattern length of the synchronization pattern detected at the immediately preceding detection timing by the first offset length, and a second offset length that is shorter than the pattern length of the synchronization pattern detected at the immediately preceding detection timing. It consists of a long second threshold value, when the pattern length appearing in the data stream which varies depending on the rotation frequency of said disk recording medium is a value between the first threshold and the upper Symbol second threshold value, the synchronization A synchronization pattern detection method for detecting a pattern. The synchronization pattern detection method according to claim 3 , further comprising a window generation step of generating a window signal based on the timing interval detected in the timing interval detection step. A synchronization pattern detection step of detecting a synchronization pattern by comparing a pattern length appearing in a data string obtained by sampling an information signal read from a disk recording medium with a fixed-frequency asynchronous clock with a threshold;
A timing interval detection step for detecting a timing interval of the synchronization pattern detected in the synchronization pattern detection step;
A threshold setting step for variably setting the threshold based on the timing interval detected in the timing interval detection step;
A spindle control step for controlling the rotation of the disk recording medium based on the detection timing of the synchronization pattern in the synchronization pattern detection step;
With
The synchronization pattern detection step includes
A first threshold in which a pattern length appearing in the data string that changes in accordance with the rotational frequency of the disk recording medium is shorter than a pattern length of the synchronization pattern detected at the immediately preceding detection timing by a first offset length; A disk rotation control method for detecting a synchronization pattern when the value is between a second threshold value and a second offset length longer than the pattern length of the synchronization pattern detected at the timing.

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