JP4419702B2 - Reproduction device, defect detection device, defect detection method - Google Patents

Description

  The present invention relates to a defect detection apparatus, a defect detection method, and a reproduction apparatus having a defect detection apparatus that detect a defect appearing on a signal read from a recording medium.

JP-A-1-92972

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. An optical disk is a generic term for recording media that irradiate laser light onto a disk in which a thin metal plate is protected with plastic, and read signals by changes in reflected light.
The optical disc includes, for example, a read-only type as known as CD, CD-ROM, DVD-ROM, MD, CD-R, CD-RW, DVD-R, DVD-RW, DVD + RW, DVD -There is a type in which user data can be recorded as known in RAM and the like. In the recordable type, data can be recorded by using 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.

The recording / reproducing system for these optical discs detects scratches, dirt, recording film defects, and other defects on the disc, and performs prescribed actions to prevent the recording / reproducing operation from becoming unstable due to these effects. It has been performed conventionally.
The reproduction RF signal waveform of an optical disc may include a peak with high reflectance called a white spot and a peak with low reflectance called a black dot, and these are generally collectively called a defect.
A circuit configuration for defect detection is disclosed in, for example, the above-mentioned Patent Document 1.

As a defect detection method, a circuit that performs top hold and bottom hold on a reproduction RF signal read from a disk, takes a difference between them, and binarizes a portion where the envelope becomes small can be considered. FIG. 4 shows a configuration example of the defect detection apparatus of the system. FIG. 5 shows the operation waveform.
The defect detection apparatus shown in FIG. 4 includes a buffer 32, a top peak hold circuit 33, a bottom peak hold circuit 34, a subtractor 35, a comparator 37, and a reference voltage source 36.

The RF signal input to the terminal 31 is supplied to the top peak hold circuit 33 and the bottom peak hold circuit 34 via the buffer 32.
The input RF signal is shown in FIG. For simplicity, the reproduction RF signal is described as a single carrier. The RF signal includes a defective portion called a black dot, that is, a portion in which a part of the RF signal is no signal.
The RF signal is top peak-held by the top peak hold circuit 33, whereby a top hold signal TP indicated by a solid line in FIG. 5B is obtained. Further, by bottom peak holding by the bottom peak hold circuit 34, a bottom hold signal BT shown by a broken line in FIG. 5B is obtained.
The top hold signal TP and the bottom hold signal BT are subtracted by (TP-BT) by the subtractor 35 to obtain a subtraction result signal Sd in FIG.
The comparator 37 is supplied with the comparison reference voltage Th from the reference voltage source 36, and compares the subtraction result signal Sd with the comparison reference voltage Th. The binarized signal as a comparison result in the comparator 37 is set as the defect signal DF in FIG.
That is, since the subtraction result signal Sd is a signal indicating the amplitude of the reproduction RF signal, the level of the subtraction result signal Sd is equal to or less than a certain threshold value (comparison reference voltage Th) (for example, ½ or less of a normal reproduction RF signal). And the defect signal DF is output. Note that the defect signal DF in this example is low active.

According to the defect detection apparatus of FIG. 4 described above, defect detection as so-called black dots can be performed satisfactorily.
However, some defects are called white spots. For example, if the mirror surface is partially exposed due to poor molding or peeling of the recording film of the disk, the amount of reflected light locally increases. When a defect called a white spot exists, the RF signal level partially maximizes as shown in the RF signal in FIG.

When the white spot exists in this way, the defect detection apparatus of FIG. 4 cannot correctly detect the defect.
The RF signal in FIG. 6A is top-peak-held by the top-peak hold circuit 33. Here, the top-peak hold operation sufficiently follows the fluctuation on the positive side on the charge-side time constant, but on the discharge side. The time constant cannot quickly follow the minus side due to the nature of detecting the envelope of the circuit. Therefore, the output top hold signal TP is as shown by the solid line in FIG.
Also, in the bottom peak hold circuit 34 that holds the RF signal in the bottom peak, the charge side time constant sufficiently follows the fluctuation on the minus side, but the discharge side time constant is quickly on the plus side due to the property of detecting the envelope of the circuit. Since it cannot follow, the output bottom hold signal BT is as shown by a broken line in FIG.
That is, the peak hold circuits 33 and 34 cannot follow the amplitude with a large fluctuation, and the top hold signal TP and the bottom hold signal BT as shown in FIG. As shown in FIG. 6C, the subtraction result signal Sd, which is the output of 35, does not fall below the comparison reference voltage Th that is the threshold value of the comparator 37. As a result, the defect signal DF remains at the H level, that is, the defect cannot be detected.

  In the configuration of FIG. 4, even if the input RF signal is passed through an HPF (high pass filter), peaks appear at the transition from the signal section of the RF signal to the defect section and at the transition from the defect section to the signal section. Therefore, stable defect detection cannot be performed.

  In view of such a problem, an object of the present invention is to enable appropriate defect detection with a simple configuration, not limited to black dots and white spots.

The reproducing apparatus of the present invention comprises a reading means for reading an information signal from a recording medium, a reproduction processing means for performing signal processing for information reproduction on the information signal read by the reading means, and a reading means for reading. Defect detection means for generating a defect detection signal from the outputted information signal, and control means for controlling a signal processing operation in the reproduction processing means in accordance with the defect detection signal generated by the defect detection means.
The defect detection means is a defect detection apparatus according to the present invention, and is a filter means that blocks a low frequency component of the information signal and sets the level of the defect signal portion in the information signal to a substantially amplitude center level of the information signal. , Binarizing means for binarizing the output of the filter means, peak detecting means for performing peak detection on the output of the binarizing means, and binarizing the output of the peak detecting means to obtain a defect detection signal And a defect detection signal generating means.
The binarizing means is composed of a hysteresis comparator and outputs two systems of binarized signals as complementary outputs, and the peak detection means corresponds to the two systems of binarized signals, respectively. The defect detection signal generation means is provided and binarizes the outputs of the two systems of peak detection means, and generates a defect detection signal by logical operation of the respective binary signals.
The defect detection method of the present invention includes a filtering step that blocks a low-frequency component of an information signal read from a recording medium and sets the level of the defect signal portion in the information signal to a substantially amplitude center level of the information signal; A binarization step for binarizing the output obtained in the filtering step, a peak detection step for performing peak detection on the output obtained in the binarization step, and an output obtained in the peak detection step. A defect detection signal generation step for obtaining a defect detection signal by binarization.

That is, in the present invention, low-frequency cuts of defects such as a peak in a high reflectance direction due to a white spot and a low reflectance peak due to a black dot, which are included in a reproduction RF signal (information signal) of an optical disk or the like. To bring it to the center of the reproduction RF signal. After that, binarization and peak detection are performed, and the peak detection output is binarized to obtain a defect detection signal (defect signal).
In particular, a reproduction RF signal that has been cut off at a low frequency is binarized by a hysteresis comparator that sets two threshold values near the midpoint of the amplitude of the reproduction RF signal. Complementary outputs of the hysteresis comparator are respectively input to the peak hold circuit, and pulses having a long time are binarized by the comparator of the next stage and detected by the time constant of the peak hold circuit. Then, a defect pulse is generated by superimposing the outputs of these comparators (AND (logical product) if the defect portion is “low active” and OR (logical sum) if the defect portion is “high active”)).

According to the defect detection apparatus and the defect detection method of the present invention, there is an effect that defect detection can be favorably performed from an information signal (reproduced RF signal) regardless of black dots and white spots.
In addition, since the reproduction apparatus of the present invention can accurately detect a defect, it is possible to appropriately perform a process that copes with the defect and improve reproduction performance.

Embodiments of the present invention will be described below.
FIG. 1 is a block diagram of a reproduction system of the optical disk reproducing apparatus according to the embodiment. The disk 1 is loaded on a turntable (not shown), and is rotated at a constant linear velocity (CLV) or a constant angular velocity (CAV) by a spindle motor 2 during a reproducing operation.
The optical pickup (optical head) 3 irradiates the disc 1 with laser light, and the reflected light is detected, whereby the information recorded on the disc 1 is read. For example, when the disc 1 is a read-only disc on which information is recorded by emboss pits, reflected light information for the emboss pit row is detected. When the disc 1 is a recordable disc such as a rewritable disc or a write-once disc, information recorded as a phase change pit mark or a dye change pit mark recorded on the recording track is detected as reflected light information. Is done.
In addition, in a rewritable disc and a write-once disc, a wobbling groove is formed as a recording track, and address information and the like are recorded by the wobbling groove. In order to extract the address information and the like, reflected light information related to the wobbling of the groove is recorded. Is also detected.

  In the pickup 3, 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, a laser beam is irradiated onto the disk recording surface via the objective lens, and An optical system (not shown) for guiding the reflected light to the photodetector is formed. For example, in the case of a system using a Blu-ray disc as the disc 1, the laser diode outputs a so-called blue laser having a wavelength of 405 nm, for example, and the NA by the optical system is 0.85.

Reflected light information from the disk 1 is detected by a photodetector, and is supplied to the matrix circuit 4 as an electric signal corresponding to the amount of received light.
The matrix circuit 4 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as photodetectors, and generates necessary signals by matrix calculation processing.
For example, a high-frequency signal (reproduction RF signal) corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, and the like are generated.
Further, a push-pull signal is generated as a signal related to groove wobbling, that is, a signal for detecting wobbling.
The focus error signal and tracking error signal are supplied to a servo processing circuit system (not shown), and the push-pull signal is supplied to a wobble signal processing system (not shown).

FIG. 1 shows a reproduction system that performs signal processing on the reproduction RF signal output from the matrix circuit 4.
The reproduction RF signal is first clamped by the clamp circuit 5 to remove unnecessary DC components. Further, the AGC (Auto Gain Control) circuit 6 performs AGC processing to adjust the amplitude level, and the equalizer 7 equalizes so as to have a predetermined frequency characteristic.
The reproduced RF signal processed in this way is supplied to the PLL unit 8 and binarized, and a reproduced clock CK synchronized with the binarized reproduced RF data DT is generated.
The reproduction RF data DT and the reproduction clock CK are supplied to the decoder 9. The decoder 9 decodes the reproduction RF data DT using the reproduction clock CK. That is, decoding processing corresponding to the encoding format of the recording data on the disc 1, error correction, deinterleaving, and the like are performed, and thereby reproduction data is demodulated.

The reproduction RF signal is also supplied to the defect detection circuit 12. The defect detection circuit 12 generates a defect signal DF for detecting black dots and white spots, and supplies the defect signal DF to the reproduction system controller 10 with the configuration described later.
The playback system controller 10 is a control unit that controls the playback system shown in the figure. The system controller 11 is a control unit that controls the entire apparatus.
The reproduction system controller 10 receives a reproduction timing gate signal from the system controller 11 and outputs a clamp pulse, an AGC enable signal, and a PLL enable signal.
The clamp circuit 5 performs a clamp process according to the clamp pulse.
The AGC circuit 6 performs AGC processing in response to the AGC enable signal. When an AGC hold signal is supplied from the reproduction system controller 10, the AGC circuit 6 holds the AGC processing.
The PLL unit 8 generates a reproduction clock according to the PLL enable signal. When a PLL hold signal is supplied from the reproduction system controller 10, the PLL unit 8 holds the PLL process.

The defect detection circuit 12 detects a portion having a smaller envelope from the reproduction RF signal as a defect section, and outputs a defect signal DF, which is an output thereof, to the reproduction system controller 10. The reproduction system controller 10 receives the defect signal. In the defect detection period by the DF, the clamp circuit 5 clamps with a clamp pulse so that the level difference of the reproduction RF signal due to the defect is taken.
Further, the reproduction controller 10 outputs an AGC hold signal and holds the AGC process of the AGC circuit 6 during the defect detection period by the defect signal DF, thereby preventing an inappropriate AGC process from being performed. That is, an operation in which the AGC process is performed in the defective portion (non-signal portion) of the reproduction RF signal to maximize the AGC gain is prevented.
Further, the reproduction controller 10 outputs a PLL hold signal during the defect detection period by the defect signal DF and holds the PLL processing of the PLL unit 8 so that the PLL is disturbed by the defect and the reproduction clock CK is in an inappropriate state. To prevent becoming.

For example, a reproducing apparatus having such a reproducing system is characterized in the configuration of the defect detection circuit 12 in this example.
FIG. 2 shows the configuration of the defect detection circuit 12, and FIG. 3 shows its operation waveform.
The defect detection circuit 12 includes a high pass filter (HPF) 22, a hysteresis comparator 23, top peak hold circuits 24 and 25, comparators 26 and 27, and an AND gate 28.

A reproduction RF signal from the matrix circuit 4 is input to the terminal 21. A waveform example of the reproduction RF signal is shown in FIG. In this example, for simplicity, the reproduction RF signal is represented as a single carrier. The reproduction RF signal includes defect portions as white spots and black dots as shown in the figure.
The input reproduction RF signal is cut off by the HPF 22 at a low frequency. FIG. 3B shows the signal RFh subjected to the low-frequency cutoff filter processing by the HPF 22. As can be seen from the figure, depending on the HPF 22, there are white spots (peaks with high reflectivity) and black dots (low reflectivity peaks) included in the playback RF signal at the center level of the playback RF signal. To come.

This signal RFh is supplied to the hysteresis comparator 23. The hysteresis comparator 23 raises the output to the H level when the signal RFh exceeds the level L1, and performs a comparison process for setting the output to the L level when the signal RFh falls below the level L2. Then, by this hysteresis comparison process, the binarized signal CP1 of FIG. Furthermore, the hysteresis comparator 23 outputs a binary signal CP2 of FIG. 3D, which is an inverted signal of the binary signal CP1, as a complementary output.
The binarized signal CP1 is supplied to the top peak hold circuit 24 and is top peak held, whereby the peak hold signal PK1 of FIG.
Further, the binarized signal CP2 is supplied to the top peak hold circuit 25 and is top peak held, whereby the peak hold signal PK2 of FIG.

The peak hold signal PK1 output from the top peak hold circuit 24 is compared with the threshold value Th1 shown in FIG. 3E by the comparator 26 and binarized again, and the binarized signal S1 in FIG. Is output.
The peak hold signal PK2 output from the top peak hold circuit 25 is compared with the threshold value Th1 shown in FIG. 3F by the comparator 27 and binarized again, and the binarized signal S2 shown in FIG. Is output.
The level of the threshold Th1 in the comparators 26 and 27 is the midpoint level of the output of the hysteresis comparator 23.
The binarized signals S1 and S2 output from the comparators 26 and 27 are logically ANDed by an AND gate 28, which is converted into an active-low defect signal DF as shown in FIG. Is output.

As can be seen from the above operation, a defect detection result for black dots is obtained as the binarized signal S1, and a defect detection result for white spots is obtained as the binarized signal S2. Since it is low active, the defect signal DF, which is the logical product of these, becomes a defect detection signal indicating both black dots and white spots.
In other words, in this example, the defect such as the peak in the high reflectance direction due to the white spot included in the reproduction RF signal and the peak in the low reflectance due to the black dot is blocked at a low frequency so that the center of the reproduction RF signal is obtained. bring up.
Then, binarization (CP1, CP2) is performed by the hysteresis comparator 23 in which two threshold values are set around the midpoint of the amplitude of the reproduction RF signal. Complementary outputs of the hysteresis comparator 23 are input to the top peak hold circuits 24 and 25, respectively, and a pulse having a long time is binarized and detected by the comparators 26 and 27 in the next stage according to the time constant of the top peak hold circuit (S1, S1). S2). The long pulse detected as the binarized signals S1 and S2 is a pulse in the black dot section on the binarized signal CP1 on the top peak hold circuit 24 and the comparator 26 side. On the side of 25 and the comparator 27, it is a pulse in a white spot section on the binarized signal CP2. The defect signal DF is generated by the logical product of the outputs of the comparators 26 and 27.
By such an operation, defect detection can be performed satisfactorily with a simple configuration regardless of black dots and white spots. In addition, since the defect detection can be performed accurately in the reproduction apparatus shown in FIG. 1, the processing corresponding to the defect detection, that is, the clamp, the AGC hold, and the PLL hold can be appropriately performed as described above, and the reproduction performance is improved. Can do.

Various modifications can be considered for the present invention.
In the configuration of the defect detection circuit 12 of FIG. 2, when the defect signal DF is a high active signal (the binarized signals S1 and S2 are inverted signals with respect to FIGS. 3G and 3H, respectively). ), The defect signal DF is configured to take a logical sum by supplying the binary signals S1 and S2 to the OR gate.
In FIG. 2, the binarized signal S <b> 2 inverted with respect to the binarized signal S <b> 1 is output as the complementary output of the hysteresis comparator 23, but the inverted signal may not be used. That is, a configuration in which a bottom peak hold circuit is provided instead of the top peak hold circuit 25 and the binarized signal S1 is supplied to both the top peak hold circuit 24 and the bottom peak hold circuit is also conceivable. Of course, in that case, it is obvious that the positive / negative relationship and the logical operation of the comparison process of the comparator 27 may be designed in accordance with it.

It is also conceivable to realize the circuit by inputting a binarized signal S1 to a digital circuit and detecting a portion where the polarity does not change (a circuit detecting a portion where the signal does not toggle for a certain period of time).
It is also conceivable to digitize the input reproduction RF signal and digitize all the blocks in FIG.
Furthermore, it is conceivable to add an AGC circuit to the input unit having the configuration shown in FIG.
If noise outside the target band is a problem, a band pass filter (BPF) may be provided instead of the HPF 22. In that case, the low-frequency cutoff frequency of the BPF is the same as that of the HPF 22, and the high-frequency cutoff frequency is a frequency that can block out-of-band noise.

It is a block diagram of the reproduction | regeneration system of the reproducing | regenerating apparatus of embodiment of this invention. It is a block diagram of a defect detection circuit of an embodiment. It is explanatory drawing of the operation waveform of the defect detection circuit of embodiment. It is a block diagram of the conventional defect detection apparatus. It is explanatory drawing of the defect detection operation | movement waveform with respect to the conventional black dot. It is explanatory drawing of the defect detection operation | movement waveform with respect to the conventional white spot.

Explanation of symbols

  1 disk, 3 pickup, 4 RF matrix circuit, 5 clamp circuit, 6 AGC circuit, 7 equalizer, 8 PLL section, 9 decoder, 10 playback system controller, 11 system controller, 12 defect detection circuit, 22 HPF, 23 hysteresis comparator, 24,25 top peak hold circuit, 26,27 comparator, 28 AND gate

Claims (3)

Reading means for reading an information signal from the recording medium;
Reproduction processing means for performing signal processing for information reproduction on the information signal read by the reading means;
Defect detection means for generating a defect detection signal from the information signal read by the reading means;
Control means for controlling the signal processing operation in the reproduction processing means according to the defect detection signal generated by the defect detection means,
The defect detection means is
By cutting a low frequency component of said information signal, the level of the defect signal portion to be the peak to peak and low reflectance direction towards high reflectivity in the information signal, substantially amplitude central level of the information signal Filtering means to
A binarizing means comprising a hysteresis comparator for binarizing the output of the filter means, and outputting two binarized signals as complementary outputs ;
Two systems of peak detection means provided corresponding to each of the two systems of binarization signals output from the binarization means and respectively performing peak detection;
Defect detection signal generation means for generating a defect detection signal by binarizing the outputs of the two systems of peak detection means, and performing logical operations on the respective binary signals ;
Playback device equipped with. By cutting a low frequency component of the read from the recording medium information signals, the level of the defect signal portion to be the peak to peak and low reflectance direction towards high reflectivity in the information signal, the information signal Filter means having a substantially amplitude center level of
A binarizing means comprising a hysteresis comparator for binarizing the output of the filter means, and outputting two binarized signals as complementary outputs ;
Two systems of peak detection means provided corresponding to each of the two systems of binarization signals output from the binarization means and respectively performing peak detection;
Defect detection signal generation means for generating a defect detection signal by binarizing the outputs of the two systems of peak detection means, and performing logical operations on the respective binary signals ;
Defect detection device provided with. By cutting a low frequency component of the read from the recording medium information signals, the level of the defect signal portion to be the peak to peak and low reflectance direction towards high reflectivity in the information signal, the information signal A filtering step with a substantially amplitude center level of
A binarization step for outputting two systems of binarization signals as complementary outputs of a hysteresis comparator that binarizes the output obtained in the filtering step;
A peak detection step for outputting two systems of peak detection corresponding to each of the two systems of binary signals obtained in the binarization step;
A defect detection signal generation step of generating a defect detection signal by binarizing each of the two systems of outputs obtained in the peak detection step and performing a logical operation on each of the binarized signals ;
Defect detection method Ru equipped with.

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