JP2004145922A - Optical disk device, and prepit signal detection method for optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the jitters of a write clock signal caused by a wobbling signal and a prepit signal which are detected from a recording track. <P>SOLUTION: The optical disk device carries out control for the rotation and recording of an optical disk based on a rotation control wobbling signal detected from the recording track of an optical disk and a recording position search prepit signal detected from a land track between adjacent recording tracks. This device is provided with a radial push-pull signal output means for outputting a radial push-pull signal based on the reflected light of an optical beam radiated to the recording track and the land track adjacent to each other, a threshold value supply means for supplying a threshold value to extract a prepit signal, a binarized prepit detecting means for comparing the radial push-pull signal with the threshold value to detect a binarized prepit signal with the boundary of the threshold value in the radial push-pull signal, and a prepit signal width correcting means for correcting the width of the binarized prepit singal to a fixed value. As a result, fluctuation in the width of an LPP signal is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disk device and a method for detecting a pre-pit signal of the optical disk device.
[0002]
[Prior art]
Recording-type optical disks on which data can be recorded by using a laser beam include, for example, data write-once optical disks such as CD-R, DVD-R, and DVD + R, and CD-RW, DVD-RW, There is a rewritable (ReWritable) optical disk (optical recording medium) such as a DVD + RW.
[0003]
In such an optical disk, a device for improving the reliability of information recording / reproduction has been devised by using two methods called groove wobbling and land prepit as a preformat. As shown in FIG. 5, first, a groove track 4 as a track for storing information is formed on the substrate of the optical disc 1. The groove track 4 wobbles at a frequency based on a reference clock for controlling the rotation of the optical disc 1. The area between the adjacent groove tracks 4 is called a land track 2, on which prepits 3 are formed. The pre-pits 3 include address information, synchronization signals, and the like (hereinafter, these are collectively referred to as LPP (Land Pre-Pit, pre-pit) signals) required for position search at the time of recording information on the optical disc 1. Is expressed.
[0004]
Here, in an optical disc apparatus for recording / reproducing information on / from the optical disc 1, at the time of information recording, a light beam B is irradiated so that the center thereof coincides with the center of the groove track 4, and the recorded information is recorded on the groove track 4. An information recording pit corresponding to is formed. At this time, a part of the light spot SP is set so as to be irradiated also on the land tracks 2 located on both sides of the groove track 4 irradiated with the light beam B. The optical disk device detects a radial push-pull signal based on the reflected light of the light spot SP. Specifically, a signal including a wobbling frequency component (hereinafter, referred to as a WBL (Wobble) signal) is obtained based on the reflected light from the groove track 4. Further, an LPP signal is obtained based on the reflected light from the land track 2. A radial push-pull signal is generated by superimposing the LPP signal on a predetermined phase position of the WBL signal.
[0005]
The optical disk device extracts the WBL signal and the LPP signal included in the radial push-pull signal, and performs control related to rotation of the optical disk 1 and recording / reproduction of information on / from the optical disk 1 based on the extracted signals. .
[0006]
Explaining the extraction of the LPP signal, the WBL signal is compared with a fixed threshold (slice level), and only a signal exceeding the threshold is extracted. By taking the logical product of the extracted signal and the gate signal synchronized with the WBL signal, the LPP signal superimposed on the WBL signal is extracted (for example, see Patent Document 1).
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-293855
[Problems to be solved by the invention]
In the prior art described above, there is a problem that the width of the LPP signal extracted at the time of recording fluctuates and the jitter of the write clock signal cannot be reduced.
[0009]
The fluctuation of the width of the LPP signal is caused by the modulation by the Write pulse of an LD (laser diode) that irradiates the laser light, or the reflected light of the laser light at a position between the mark and the space area in the recording data. It is to receive light. Further, even when the power level of the laser beam is different, the width of the LPP signal binarized at the slice level varies.
[0010]
In particular, the waveform of the LPP signal in the recording area is subjected to the pulse modulation of the LD described above, and the signal in a portion other than the pre-pit is also increased. Therefore, there is a high possibility that a signal in a portion other than the pre-pit is erroneously detected as an LPP signal. Therefore, there is a high possibility that the LPP signal detected at the time of recording has a different width from the actual LPP signal.
[0011]
Due to such a change in the LPP signal width, an extra control voltage is generated in the PLL control signal when comparing the phases of the PLL control in generating the write clock signal. Therefore, in the PLL control of the write clock signal, the VCO jitter is deteriorated, and the best recording cannot be performed.
[0012]
[Means for Solving the Problems]
Therefore, in the main invention according to the present invention, a wobble signal for rotation control detected from a recording track of an optical disk and a pre-pit signal for recording position search detected from a land track between the adjacent recording tracks are used. An optical disc device for controlling rotation and recording of the optical disc,
Radial push-pull signal output means for outputting a radial push-pull signal based on reflected light of a light beam applied to the adjacent recording track and land track, and a threshold for extracting the pre-pit signal. Threshold supply means for supplying, a binary pre-pit detection means for comparing the radial push-pull signal with the threshold, and detecting the pre-pit signal binarized at the threshold in the radial push-pull signal; And a pre-pit signal width correction means for correcting the width of the binarized pre-pit signal to a constant value.
Other features of the present invention will be apparent from the accompanying drawings and the description of the present specification.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
===== Disclosure Overview =====
At least:
In the optical disc device according to the present invention, the wobble signal for rotation control detected from a recording track of the optical disc and the pre-pit signal for recording position search detected from a land track between the adjacent recording tracks, It controls the rotation and recording of the optical disk,
Radial push-pull signal output means for outputting a radial push-pull signal based on reflected light of a light beam applied to the adjacent recording track and land track, and a threshold for extracting the pre-pit signal. Threshold supply means for supplying, a binary pre-pit detection means for comparing the radial push-pull signal with the threshold, and detecting the pre-pit signal binarized at the threshold in the radial push-pull signal; And a pre-pit signal width correction means for correcting the width of the binarized pre-pit signal to a constant value.
[0014]
The constant value used by the pre-pit signal width correction means may be a width of a pre-pit signal obtained from an unrecorded area of the optical disc.
Storage means may be provided for storing the constant value used by the pre-pit signal width correction means.
The apparatus may further include a pre-pit signal width measuring means for measuring a width of the binarized pre-pit signal detected by the binarized pre-pit detecting means.
[0015]
The pre-pit signal width correction means may correct the width of the pre-pit signal measured by the pre-pit signal width measurement means to the constant value read from the storage means.
The pre-pit signal width correction unit may replace the width of the pre-pit signal measured by the pre-pit signal width measurement unit with the constant value read from the storage unit.
[0016]
The apparatus further includes a pre-pit signal rising detecting means for detecting a rising timing of the binarized pre-pit signal detected by the binarizing pre-pit detecting means, wherein the pre-pit signal width correcting means is configured to detect the rising of the pre-pit signal. With the timing as a starting point, the constant value read from the storage means can be used as the width of the pre-pit signal.
[0017]
In the method for detecting a prepit in an optical disc device according to the present invention, a wobble signal for rotation control detected from a recording track of the optical disc and a prepit signal for recording position search detected from a land track between the adjacent recording tracks include Based on, to control the rotation and recording of the optical disk,
Outputting a radial push-pull signal based on reflected light of a light beam applied to the recording track and the land track adjacent to each other, and supplying a threshold for extracting the pre-pit signal; Comparing the radial push-pull signal with the threshold value, detecting the binarized pre-pit signal at the threshold value in the radial push-pull signal, and setting the binarized pre-pit signal width to a constant value. And correcting to
[0018]
===== Example =====
<<<< Overall system configuration >>>>
A schematic configuration of an entire system including an optical disk device according to an embodiment of the present invention will be described with reference to FIG. The optical disc device 10 includes an optical pickup 11, a WBL (wobble signal) detector 12, an LPP detector 13, a write clock generator 14, a decoder 15, a spindle motor 16, a spindle servo circuit 17, an optical pickup servo circuit 18, a processor 19, An interface unit 20, an encoder 21, a laser control unit 22, and a ROM 23 are provided.
[0019]
The optical disk device 10 is connected to an external host computer 24 via the interface unit 20. Data SWD to be recorded on the optical disk 1 is input from the host computer 24 to the optical disk device 10.
[0020]
The optical pickup 11 is means for recording / reproducing data on / from an optical disk, and includes a laser diode, a beam splitter, an objective lens, a photodiode, etc. (all not shown). The optical pickup 11 irradiates a recording track of the optical disc 1 with a light beam B based on a laser control signal SDL. The reflected light of the irradiated light beam B is received by the first divided light receiving unit and the second divided light receiving unit of the photodiode. The first divided light receiving section and the second divided light receiving section are optically parallel to the tangential direction of the recording track.
[0021]
The optical pickup 11 includes a focus servo for correcting the focal point of the light beam B on the surface of the optical disk 1, a tracking servo for correcting a deviation between the center of the incident light beam B and the track center, and an optical axis of the light beam B. A mechanism for performing various servo controls such as a tilt servo for correcting a deviation of the orthogonal relationship with the optical disc 1 is incorporated. The configuration of the optical pickup 11 is realized, for example, by using a known hardware configuration as shown in FIG. 1-8 on page 17 of “Basic chapter 18 on DVD & DVC” issued by Dempa Shimbun.
[0022]
As shown in FIG. 2, the WBL detection unit 12 outputs a wobble (WBL) signal B.WBL. P. F. (Band Pass Filter) circuit 12a, comparator 12b and the like. The radial push-pull signal SDT detected based on the reflected light of the light beam B is the wobble signal B. P. F. Input to the circuit 12a. Wobble signal B. P. F. The high-frequency noise component in the radial push-pull signal SDT is removed by the circuit 12a, and the WBL signal component A_WBL is extracted. The WBL signal component A_WBL (minus side) is compared with the reference voltage (plus side) by the comparator 12b to output a binary WBL signal. This binarized WBL signal is output to the write clock generator 14, the spindle servo circuit 17, and the like shown in FIG. The reference voltage input to the comparator 12b is an analog value obtained by converting a zero-cross level (threshold voltage) specified by the processor 19 by a DAC (D / A converter) (not shown). If the comparator 12b has a hysteresis characteristic, the noise resistance can be improved, and the binarized WBL signal can be detected with high accuracy and reliability.
[0023]
As shown in FIG. 2, the LPP detection unit 13 includes a level switching circuit 13a, an amplitude adjustment circuit 13b, and a difference calculator 13c as a radial push-pull signal output unit.
In addition, the LPP detection unit 13 includes a DAC (D / A converter, threshold value supply means) 13d for adjusting the slice level of the LPP detection and a comparator (binary pre-pit detection means) 13e.
[0024]
In this configuration, the amplitude of the output signal of each of the above-described first and second divided light receiving units is adjusted and adjusted by the processing of each of the circuits 13a, 13b, and 13c in the mark and the space area of the recording data during recording. The difference calculation of the signals is performed. As a result of the difference operation, a radial push-pull signal SDT is detected.
[0025]
On the other hand, the digital value Vs specified by the processor 19 is input to the LPP detection slice / level adjustment DAC 13d. Based on this digital value Vs, the LPP detection slice level adjusting DAC 13d generates a slice level Sref. The comparator 13e compares the slice level Sref (plus side) with the radial push-pull signal SDT (minus side) detected based on the reflected light of the light beam B. As a result of this comparison, the comparator 13e outputs a binary LPP signal LPP. The binarized LPP signal LPP is output to the write clock generator 14, the decoder 15, and the like shown in FIG. If the comparator 13e has hysteresis characteristics, the noise resistance can be improved, and the binarized LPP signal LPP can be detected with high accuracy and reliability.
[0026]
As shown in FIG. 3, the write clock generator 14 generates a write clock (WCLK) signal for recording information on the optical disc 1, and outputs the signal to the LPP width edge counter circuit 14n, the decoder 15, and the like. More specifically, the write clock generation unit 14 includes an LPP Window circuit 14a, an LPPGate circuit 14b, a phase offset circuit 14c, phase comparators 14d and 14e, LPFs (Low Pass Filters) 14f and 14g, a VCO circuit 14h, a frequency divider 14i, a wobble. It includes a filter circuit 14j and charge pump circuits 14k and 14l.
[0027]
In addition, the write clock generation unit 14 includes an LPP signal edge counter circuit (pre-pit signal width measurement unit) 14m, an LPP signal width correction circuit (pre-pit signal width correction unit) 14n, and an LPP correction width setting register (storage unit) 14o. Prepare.
[0028]
The LPP window circuit 14a and the LPPGate circuit 14b remove an unnecessary signal LPP from the input binary LPP signal LPP. The LPP Window circuit 14a removes unnecessary pulses generated due to a defect of the optical disc 1, an improper setting of the slice level Sref, and the like. On the other hand, the LPPGate circuit 14b matches the level difference between the write state and the read state in the level switching circuit 13a shown in FIG. As a result, the LPPGate circuit 14b extracts only the b2 signal having a small variation from the binary LPP signal LPP using the GATE signal. Thus, the binarized LPP signal LPP that has passed through the window circuit 14a and the LPPGate circuit 14b is input to the LPP signal edge counter circuit 14m. The write clock signal WCLK from the VCO 14h is also input to the LPP signal edge counter circuit 14m. Then, the LPP signal edge counter circuit 14m counts the period from the rising edge to the falling edge of the input binary LPP signal LPP using the write clock signal WCLK. That is, the count value output from LPP signal edge counter circuit 14m indicates the width of detected binary LPP signal LPP.
[0029]
The count value fluctuates due to the modulation of the Write pulse or the like, as described in the related art. In order to suppress this variation, the count value output from the LPP signal edge counter circuit 14m is corrected to a fixed constant value by the LPP signal width correction circuit.
[0030]
As a method of correcting the fixed constant value, the LPP signal width correction circuit 14n reads the fixed pulse width stored in the LPP correction width setting register 14o, and changes the count value by the LPP signal edge counter circuit 14m to the fixed pulse width. Replace with Then, the LPP signal width correction circuit 14n supplies the fixed pulse width to the phase comparator 14d.
[0031]
In addition, as a modification of the method of correcting the LPP signal edge counter circuit 14m with a circuit (prepit signal rising detection means) for detecting the rising edge timing in the binary LPP signal LPP, as a modified example of the method of correcting the LPP signal edge counter circuit 14m. . Alternatively, the LPP signal edge counter circuit 14m does not output a count value, but detects and outputs a rising edge timing signal. That is, the timing of the rising edge is detected without counting the actual width of the binarized LPP signal LPP that may fluctuate, and the LPP signal width correction circuit 14n supplied with this timing signal starts the timing at the start point ( The reference pulse width may be supplied to the phase comparator 14d.
[0032]
Here, the setting of the fixed pulse width stored in the LPP correction width setting register 14o will be described. During reproduction of the optical disk, the width of the binary LPP signal LPP in the unrecorded area is measured. That is, at the time of reproduction, as described above, the period from the rising edge to the falling edge of the binary LPP signal LPP in the unrecorded area is counted by the LPP signal edge counter circuit 14m. This counting operation is repeated for a fixed period, and the average value of the count value is stored in the LPP correction width setting register 14o as a fixed pulse width. By measuring the unrecorded area of the optical disk in this way, a stable binarized LPP signal can be obtained as a fixed pulse width.
[0033]
Next, as shown in FIG. 3, the binary WBL signal WBL obtained by the WBL detector 12 is input to the phase comparator 14e via the wobble filter circuit 14j. The write clock signal WCLK divided by the frequency divider 14i is also input to the phase comparator 14e. The binary WBL signal WBL input to the phase comparator 14e is compared in phase with the frequency-divided write clock signal WCLK, and the phase component is input to the LPF 14g. The control signal obtained from the LPF 14g through which this phase component has passed is input to the VCO 14h. As a result, the write clock signal WCLK from the VCO 14h is locked to the binary WBL signal WBL. The write clock signal WCLK locked to the binary WBL signal WBL is input to the phase offset circuit 14c. As a result, the phase of the write clock signal WCLK is offset (moved) near the binarized LPP signal LPP.
[0034]
The output of the phase offset circuit 14c is input to the above-described phase comparator 14d. As a result, the output of the phase offset circuit 14c is compared in phase with the fixed pulse width from the LPP signal width correction circuit 14n, and the phase component passes through the charge pump circuit 141 and the LPF 14f. The output of the LPF 14f is input to the VCO 14h as a control signal. Therefore, the phase of write clock signal WCLK locked to binary WBL signal WBL can be matched to binary LPP signal LPP. That is, the write clock signal WCLK is PLL-controlled to the binary WBL signal WBL and the binary LPP signal LPP.
[0035]
Here, the operation of correcting the count value output from the LPP signal edge counter circuit 14m to a fixed constant value by the LPP signal width correction circuit will be described with reference to waveform diagrams of various signals (1) to (7) shown in FIG. It will be described with reference to FIG. The signals (2), (5), (6) and (7) are also described in the block circuit of FIG. First, the original binary LPP signal has a pulse waveform of a constant width as shown by the physical LPP signal (1) in the figure.
[0036]
However, conventionally, as described above, the width of the binarized LPP signal fluctuates, resulting in a waveform as indicated by (2) in the figure. As a result, the charge pump 141 in which the latter half of the pulse waveform of the binarized LPP signal in (2) is inverted with respect to the rising edge of the PLL VCO clock signal (write clock signal) in (3) in FIG. Has a waveform as indicated by (4) in the figure. The output signal of the charge pump 141 is based on the output of the phase comparator 14d as described above. In the output signal of the charge pump 141 having the waveform indicated by {circle around (4)} in the figure, a black portion in the waveform corresponds to a disturbance in the output of the phase comparator 14d, and this disturbance causes an extra control voltage of the PLL control signal. Causes generation. That is, this extra control voltage causes the VCO jitter to deteriorate.
[0037]
On the other hand, in the embodiment according to the present invention, as shown by (5) in the figure, the LPP signal after correction based on the fixed pulse width is output from the LPP signal width correction circuit 14n in FIG. As a result, the charge pump 141 in which the latter half of the pulse waveform of the binarized LPP signal in (5) is inverted with respect to the rising edge of the PLL VCO clock signal (write clock signal) in (6) in FIG. Has a stable waveform without fluctuation as indicated by {circle around (7)} in the figure. The stable waveform {circle around (7)} in this figure approximates an ideal waveform obtained by inverting the latter half of the pulse waveform having the constant width {circle around (1)} in the figure with the middle point as a boundary. Therefore, the output of the phase comparator 14d is not disturbed, the control voltage of the control signal of the PLL is stabilized, and the deterioration of the VCO jitter can be prevented.
[0038]
As shown in FIG. 1, the decoder 15 decodes address information and a synchronization signal from the binary LPP signal, and outputs a timing signal SWT in which the decoded content is associated with the WCLK signal to the processor 19.
[0039]
The spindle servo circuit 17 is a servo mechanism of the spindle motor 16 for rotating the optical disk. When the wobbling frequency information such as the binary WBL signal and the WBL signal component A_WBL is input from the WBL detection unit 12, the spindle servo circuit 17 outputs a spindle control signal SSS to the spindle motor 16 based on the wobbling frequency information. The servo of the rotation of the spindle motor 16 is controlled.
[0040]
The optical pickup servo circuit 18 is a servo mechanism of the optical pickup 11. The optical pickup servo circuit 18 generates a pickup servo control signal SSP for a servo mechanism of the optical pickup 11 such as focus, tracking, tilt, etc., based on a signal detected by a photodiode or the like of the optical pickup 11. Output to pickup 11. The optical pickup 11 to which the pickup servo control signal SSP has been input adjusts the offset value of each servo mechanism so that the focus and tracking are shifted and the tilt angle becomes zero.
[0041]
The processor 19 uses the timing signal SWT input from the decoder 15 to change the track position on the optical disk 1 corresponding to the address information included in the timing signal SWT from the host computer 24 via the interface unit 20. The control relating to the recording operation of the received recording data SWD is performed. When the optical disk device 10 detects information already recorded on the optical disk 1 by the optical pickup 11, the processor 19 performs 8-16 demodulation, error correction, and the like on the detected information. The control related to the reproduction operation for the subsequent information is also performed. As described above, the processor 19 controls the entire optical disc device 10 relating to recording and reproduction of the optical disc 1.
[0042]
The ROM 23 stores data relating to various types of information, and is accessed by the processor 19. The data stored in the ROM 23 includes a zero-cross level Vref input to the WBL detection unit 12 and a digital value Vs input to the LPP detection unit 13.
[0043]
The encoder 21 includes an ECC generator (not shown), an 8-16 modulator, a scrambler, and the like, and forms an ECC block that is a unit for performing error correction during reproduction based on the recording data SWT reflecting the timing signal SWT. At the same time, a modulated signal SRE that has been subjected to interleaving, 8-16 modulation, and scrambling for the ECC block is output to the laser control unit 22.
[0044]
The laser control unit 22 outputs a laser drive signal SDL for driving a laser diode (not shown) in the optical pickup 11 to emit a light beam B to the optical pickup 11 based on the modulation signal SRE.
[0045]
As described above, the embodiment of the present invention has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist of the invention.
[0046]
In the present embodiment, the width of the LPP signal extracted during recording is prevented from fluctuating and is made constant to stabilize the write clock jitter. This can improve the signal quality after recording.
[0047]
【The invention's effect】
Variations in the width of the LPP signal can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a system including an optical disk device according to an embodiment of the present invention.
FIG. 2 is a functional block diagram mainly including a WBL detection unit 12 and an LPP detection unit 13 according to an embodiment of the present invention.
FIG. 3 is a functional block diagram mainly illustrating a write clock generation unit 14 according to an embodiment of the present invention.
FIG. 4 is a waveform diagram showing main signals of the optical disc device according to one embodiment of the present invention.
FIG. 5 is a diagram illustrating a preformat of an optical disc.
[Explanation of symbols]
1 optical disk, 2 land tracks, 3 pre-pits,
4 groove tracks, 10 optical disk devices, 11 optical pickups,
12 WBL detector,
12a wobble (WBL) signal P. F. (Band Pass Filter) circuit,
12b comparator, 13 LPP detector,
13a level switching circuit,
13b amplitude adjustment circuit, 13c difference calculator,
13d LPP detection slice / level adjustment DAC (threshold supply means),
13e comparator (binary pre-pit detecting means),
14 write clock generator,
14m LPP signal edge counter circuit (pre-pit signal width measuring means),
14n LPP signal width correction circuit (pre-pit signal width correction means),
14o LPP correction width setting register (storage means),
15 decoder, 16 spindle motor,
17 spindle servo circuit, 18 optical pickup servo circuit,
19 processor, 20 interface unit, 21 encoder,
22 laser control unit, 23 ROM, 24 host computer

Claims (8)

Based on a wobble signal for rotation control detected from a recording track of the optical disc and a pre-pit signal for recording position search detected from a land track between adjacent recording tracks, the rotation and recording of the optical disc are performed. An optical disk device that performs control,
Radial push-pull signal output means for outputting a radial push-pull signal based on reflected light of a light beam applied to the recording track and the land track adjacent to each other,
Threshold supply means for supplying a threshold for extracting the pre-pit signal,
Binarized pre-pit detection means for comparing the radial push-pull signal with the threshold and detecting the binarized pre-pit signal at the threshold in the radial push-pull signal;
Pre-pit signal width correction means for correcting the width of the binarized pre-pit signal to a constant value;
An optical disk device comprising: 2. The optical disk apparatus according to claim 1, wherein the constant value used by the pre-pit signal width correction unit is a width of a pre-pit signal obtained from an unrecorded area of the optical disk. 3. The optical disk device according to claim 1, further comprising a storage unit that stores the constant value used by the pre-pit signal width correction unit. 4. The optical disc apparatus according to claim 1, further comprising a pre-pit signal width measuring unit that measures a width of the binarized pre-pit signal detected by the binarized pre-pit detecting unit. . The method according to claim 4, wherein the pre-pit signal width correction unit corrects the width of the pre-pit signal measured by the pre-pit signal width measurement unit to the constant value read from the storage unit. Optical disk device. 6. The optical disk according to claim 5, wherein the pre-pit signal width correction unit replaces the width of the pre-pit signal measured by the pre-pit signal width measurement unit with the constant value read from the storage unit. apparatus. A pre-pit signal rising detecting means for detecting a rising timing of the binarized pre-pit signal detected by the binarized pre-pit detecting means;
4. The pre-pit signal width correction unit according to claim 3, wherein the pre-pit signal width correction unit sets the constant value read from the storage unit as a width of the pre-pit signal, using the timing of the rise of the pre-pit signal as a starting point. Optical disk device. Based on a wobble signal for rotation control detected from a recording track of the optical disc and a pre-pit signal for recording position search detected from a land track between adjacent recording tracks, the rotation and recording of the optical disc are performed. A pre-pit detection method for an optical disk device that performs control,
Outputting a radial push-pull signal based on reflected light of a light beam applied to the recording track and the land track adjacent to each other,
Supplying a threshold value for extracting the pre-pit signal;
Comparing the radial push-pull signal with the threshold, and detecting the binarized pre-pit signal at the threshold in the radial push-pull signal;
Correcting the width of the binarized pre-pit signal to a constant value;
A method for detecting a pre-pit in an optical disk device, comprising:

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