JP2007287219A - Reproducing method of optical disk, and reproducing device of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reproducing method of an optical disk, and a reproducing device of the optical disk by which auxiliary information can be demodulated accurately from a wobble signal however recording states of adjacent tracks of a track to be traced and an inner peripheral side and an outer peripheral side to be traced are combined when auxiliary information is demodulated from the wobble signal in the optical disk in which the auxiliary information including address information is recorded as the wobble signal at the boundary part of a land track and a groove track, where information can be recorded. <P>SOLUTION: Since the recording states of the track to be traced and the adjacent track of the inner peripheral side and the outer peripheral side of the track to be traced are discriminated and the wobble signal Wa is binarized using a threshold value Th being optimum for combination of the recording state, an auxiliary signal Ad can be demodulated from a binarized wobble signal Wb obtained by binarization. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc recording / reproducing method and an optical disc recording / reproducing apparatus for recording / reproducing a digital information signal on an optical disc, and in particular, when reproducing auxiliary information from a wobble formed at a boundary between a groove track and a land track of the optical disc. The present invention relates to an auxiliary information reproducing method and an auxiliary information reproducing apparatus.

  As an information recording system for an optical disc, there are a land / groove system capable of recording in each of lands and grooves (grooves), and a wobble / groove system capable of recording in grooves and wobbles (swells) formed so as to meander in the radial direction. The land groove method is suitable for high density recording, and the wobble groove method is resistant to minute defects. In recent years, there is a wobble / land groove method as a method having these advantages, and there is a DVD-RAM as an optical disk using the wobble / land groove method as a format.

  In the DVD-RAM, a groove track and a land track on which information signals can be recorded / reproduced alternately exist spirally, and the groove track and the land track are switched at a connection point for each track. The track structure is a groove track recording system. In the track structure, a header is formed so as to divide the track into sectors including the connection point, and auxiliary information including address information is recorded therein.

  However, in the recording format of the optical disc in which the header is formed in such a manner as to divide the track into sectors as in the DVD-RAM, the recording capacity is reduced by the amount of the formed header. In addition, since the header exists in such a manner that the track is divided for each sector, there is a possibility that the groove track and the land track are interrupted only by that portion, and further improvement is desired.

  On the other hand, as an optical disk format that maintains the continuity of the track (recording information), there is known a format in which only the groove track is used as a recording track, such as DVD-RW, and address information is formed by prepits in the land portion. Yes.

  In the recording format such as the above-mentioned DVD-RW, recording / reproduction can be continuously performed in the track direction, and the line density is reduced by the absence of the header, but the land track is used only as auxiliary information including address information. Therefore, it is desired to improve the density and capacity.

  When considering recording and reproduction of audio information and image information on a higher-density and large-capacity optical disk, when using an optical disk (DVD-RAM) that can record and reproduce on both the land track and the groove track, Further, it is desirable to realize a recording format capable of continuous recording / reproduction without taking addressing means by the header.

  The following [Patent Document 1] discloses an invention relating to an optical information recording medium (optical disc), an optical information recording / reproducing method and apparatus for solving the above problems. As shown in the schematic diagram of FIG. 3, the optical disc disclosed in this [Patent Document 1] has land tracks 101 and groove tracks 102 capable of recording / reproducing information signals alternately adjacent to each other in the disc radial direction. The wobble 52 in which auxiliary information including address information of the land track 101 is recorded as a wobble signal is formed at a part of the boundary portion on one side of the land track 101, and the boundary on one side of the groove track 102 is formed. A wobble 51 in which auxiliary information including the address information of the groove is recorded as a wobble signal is formed in a part of the section. The wobble 52 in the land track 101 and the wobble 51 in the groove track 102 are formed shifted in the track direction, and a wobble 50 having a fixed period is formed in a boundary portion other than the wobbles 51 and 52. The synchronization signal is obtained by detecting the signal recorded in the wobble 50.

  In general, in order to reproduce a wobble signal from a wobble formed at a track boundary, a track on which a wobble to be reproduced is formed is irradiated with a laser beam for tracing. At this time, as shown by a laser irradiation spot S in FIG. 3, the irradiated laser light is a track to be traced (groove track 102 in FIG. 3), an adjacent track on the inner circumference side of the track to be traced, and a trace. Irradiation must be performed so as to straddle adjacent tracks on the outer periphery side of the disk of the track to be performed. The reflected light of the laser irradiated so as to straddle the track to be traced and the adjacent tracks on the inner and outer circumference sides to be traced is detected by dividing into two in the track scanning direction, that is, the inner and outer circumferential sides of the optical disk. The wobble signal detection unit reproduces the wobble signal by taking the difference between the two reflected lights.

  According to the optical disk disclosed in [Patent Document 1], recording and reproduction can be performed on both the land track 101 and the groove track 102, and the boundary between the wobble 52 and the groove track 102 formed at the boundary portion of the land track 101. Since the auxiliary information including the address information and the synchronization signal can be obtained from the wobble 51 formed in the section and the wobble 50 having a constant period, it is not necessary to form a header in a form of dividing the track for each sector. Therefore, it is possible to continuously record and reproduce information signals on the track while being a high-density and large-capacity optical disk capable of recording and reproducing information signals on both the land track 101 and the groove track 102.

JP 2003-178464 A

  As described above, in the optical disc disclosed in [Patent Document 1], in order to reproduce the wobble signal from the wobble formed at the boundary portion of the land track or the groove track, the track to be traced and the track to be traced are reproduced. It is necessary to irradiate the laser beam so as to straddle both adjacent tracks on the inner peripheral side and the outer peripheral side to obtain the reflected light. However, the amount of reflected light of the irradiated laser light varies depending on the recording state of each track. For this reason, depending on the combination of the recording state of the track to be traced and the adjacent track recording state of the track to be traced, the amplitude of the waveform of the wobble signal detected from the wobble may vary, or the wobble signal There is a problem that a wobble signal cannot be reproduced accurately, such as when erroneous detection occurs during demodulation.

  The above problem will be described in detail with reference to FIGS. FIG. 4 is a schematic diagram of the land track and groove track of the optical disk in FIG. 3 in which the recording state of the recording area of each track is added. The hatched portion in FIG. 4 represents a recorded area in a recorded state, and the white portion in FIG. 4 represents a recorded area in an unrecorded state.

  Here, suppose a case where a wobble signal is reproduced from the wobble 51a formed at the boundary portion of the groove track 102a in FIG. As described above, in order to reproduce the wobble signal from the wobble 51a of the groove track 102a, the groove track 102a, the land track 101a adjacent to the groove track 102a on the inner periphery side of the disk, and the groove track 102a are adjacent to the outer periphery side of the disk. It is necessary to irradiate the laser so as to straddle the land track 101b.

  Here, for example, when information signals are recorded continuously from the inner circumference side of the optical disk, the land track 101a on the inner circumference side of the groove track 102a is in a recorded state as shown by the irradiation spot Sb, and the groove The land track 101b on the outer peripheral side of the track 102a is in an unrecorded state. When overwriting the recorded area, as shown by the irradiation spot Sc, the land tracks 101a and 101b adjacent to the inner and outer peripheral sides of the groove track 102a are both recorded. As described above, when a certain amount of information signals are recorded on the optical disc, the recorded areas of the land track 101 and the groove track 102 include a recorded area and a non-recorded recording area. Therefore, as shown in the irradiation spot Sa, when the land tracks 101a and 101b adjacent to the inner and outer peripheral sides of the groove track 102a are both unrecorded, or as shown in the irradiation spot Sd, the groove track It is easily assumed that the land track 101a on the inner peripheral side of 102a is in an unrecorded state and the land track 101b on the outer peripheral side of the groove track 102a is in a recorded state.

  Since the reflectance of the laser light differs between the recorded area and the unrecorded state of each track, a difference occurs in the amount of reflected light received by the optical pickup. For this reason, the amplitude of the light amount of the wobble signal detected from the wobble also changes according to the recording state of each track. If the optical disk is a phase change type, the amount of reflected light is larger when the recording area of the track is unrecorded. Therefore, when the adjacent tracks on both the inner and outer sides of the track to be traced are unrecorded The amplitude of the amount of light of the wobble signal obtained is increased. On the other hand, if the track recording area is in the recorded state, the amount of reflected light is smaller than in the unrecorded state. Therefore, it is obtained when the adjacent tracks on both the inner and outer sides of the track to be traced are in the recorded state. The amplitude of the light amount of the wobble signal to be produced becomes small. The difference in reflectance depending on the recording state differs depending on the type of optical disk. For example, in a write-once type optical disk of a dye system, the amount of reflected light is large in a recorded state, contrary to a phase change type optical disk, and unrecorded The amount of reflected light becomes smaller in the state.

  As described above, the change in the amount of reflected light depending on the recording state of the track varies depending on the type of the optical disc, but in the following description, the phase change type optical disc is used as an example.

  FIG. 5 is a diagram for explaining binarization of the wobble signal in the conventional method for reproducing auxiliary information of an optical disc. Note that the wobble signals Wa1, Wa2, and Wa3 in FIG. 5 correspond to the wobble signals obtained in the recording state of each track of the irradiation spots Sa, Sb, and Sc in FIG.

  From FIG. 5, the wobble signal Wa1 obtained at the irradiation spot Sa in which the recording areas of the adjacent tracks on both the inner and outer sides of the track to be traced are in an unrecorded state has a large light intensity, and on the contrary, the track to be traced. The wobble signal Wa3 obtained at the irradiation spot Sc in which the recording areas of the adjacent tracks on both the inner and outer peripheral sides are in a recorded state has a small amount of light. Further, the wobble signal obtained at the irradiation spot Sb in which the recording area of the adjacent track on the inner circumference side of the track to be traced is in a recorded state and the recording area of the adjacent track on the outer circumference side of the track to be traced is in an unrecorded state. Wa2 has an amplitude of the light amount between the wobble signal Wa1 and the wobble signal Wa3.

  In order to demodulate the wobble signal into auxiliary information including address information, it is necessary to binarize the wobble signal into a binary wobble signal. In general, binarization of a wobble signal is performed using a certain threshold as a reference. Here, in FIG. 5, a case is considered where binarization of the wobble signals Wa1 to Wa3 is performed using the threshold value Th4 as a reference. As the binarized wobble signal Wb1 obtained by binarizing the wobble signal Wa1 using the threshold Th4 as a reference, a signal equivalent to the signal Wc given as auxiliary information is obtained. However, when the wobble signals Wa2 and Wa3 having a small amplitude of light amount are binarized using the same threshold Th4 as a reference, the obtained binarized wobble signals Wb2 and Wb3 are the threshold Th4 used as a binarization reference. Is not an optimum value for binarization of the wobble signals Wa2 and Wa3, and therefore, a deviation as shown by a broken line in FIG. 5 occurs between the signal Wc given as auxiliary information.

  As described above, when the auxiliary information including the address information is demodulated from the binarized wobble signals Wb2 and Wb3 which are shifted from the signal Wc given as the auxiliary information, the auxiliary information is accurately detected due to erroneous detection. Cannot be demodulated.

  The present invention has been made in view of the above circumstances, and address information is provided at the boundary between the land track and the groove track, which are alternately adjacent to each other in the radial direction and in which information can be recorded, and between the land track and the groove track. In the optical disc in which the auxiliary information including the wobble signal is recorded, when the auxiliary information including the address information is demodulated from the wobble signal obtained from the wobble, the tracks to be traced and the adjacent tracks on the inner and outer sides of the track to be traced An object of the present invention is to provide an optical disk reproducing method and an optical disk reproducing apparatus that can accurately demodulate auxiliary information including address information from the wobble signal in any combination of track recording states.

The present invention relates to an optical disc having grooves and lands that are alternately adjacent in the radial direction and in which information can be recorded, and wobbles in which auxiliary information Ad is recorded as a wobble signal Wa at the boundary between the grooves and the lands. 10 is a method of reproducing an optical disc by reproducing the auxiliary information Ad by irradiating a laser beam,
Detecting a recording state of the information in the groove and land in the range irradiated with the laser light, and setting a threshold Th serving as a reference when binarizing the wobble signal Wa based on the recording state; The above problem is solved by providing an optical disc reproducing method characterized in that the auxiliary information Ad is obtained by binarizing the wobble signal Wa on the basis of a set threshold Th.

Further, the optical disk 10 includes grooves and lands that are alternately adjacent in the radial direction and capable of recording information, and wobbles in which auxiliary information Ad is recorded as a wobble signal Wa at the boundary between the grooves and the lands. On the other hand, an optical disk reproducing apparatus for reproducing the auxiliary information Ad by irradiating a laser beam,
A laser beam irradiation unit for irradiating the optical disk 10 with a laser beam;
A wobble signal detector 12 for detecting the wobble signal Wa in the range irradiated with the laser beam;
A light amount detector 13 for detecting the light amount of the laser beam reflected by the optical disc 10;
A threshold setting unit 14 for setting a threshold Th serving as a reference when binarizing the wobble signal Wa based on the detected amount of laser light;
A binarization unit 15 that binarizes the wobble signal Wa on the basis of the set threshold Th,
An auxiliary information reproducing unit 16 for obtaining the auxiliary information Ad from the binarized wobble signal;
The above-mentioned problems are solved by providing an optical disk reproducing device characterized by having the following.

  The optical disc playback method and optical disc playback apparatus according to the present invention have the above-described configuration, and thus land tracks and groove tracks that are alternately adjacent in the radial direction and can record information, and the land tracks and grooves. In an optical disc in which auxiliary information including address information is recorded as a wobble signal at the boundary with the track, a track to be traced and a track to be traced when demodulating the auxiliary information including address information from the wobble signal obtained from the wobble The auxiliary information including address information can be accurately demodulated from the wobble signal in any combination of recording states of adjacent tracks on the inner and outer peripheral sides.

  Embodiments of an optical disc reproducing method and an optical disc reproducing apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an auxiliary information reproducing apparatus for an optical disc according to the present invention. FIG. 2 is a diagram for explaining binarization of a wobble signal in the method for reproducing auxiliary information of an optical disc according to the present invention. In FIG. 1, description and description of blocks that are not directly related to the present invention, such as recording and reproduction of information signals, are omitted.

  An auxiliary information reproducing apparatus 50 for an optical disc according to the present invention shown in FIG. 1 detects a laser irradiation unit having an optical pickup 11 that irradiates the optical disc 10 with laser light and detects reflected light from the optical disc 10, and an optical pickup 11. A wobble signal detector 12 for detecting the wobble signal Wa from the reproduced signal Ws, a light amount detector 13 for detecting the amount of reflected light of each track received by the optical pickup 11 and obtaining a light amount signal St, and a light amount detector The threshold value setting unit 14 for setting the threshold value Th for binarizing the wobble signal Wa from the light amount signal St from the 13 and the threshold value Th set by the threshold value setting unit 14 for the wobble signal Wa from the wobble signal detection unit 12 are set. The binarization unit 15 that performs binarization on the basis and the binarized binarized wobble signal Wb are restored to auxiliary information Ad including address information. And an auxiliary information reproducing unit 16.

  The optical pickup 11 of the laser irradiation unit irradiates the optical disk 10 with laser light and receives reflected light from the optical disk 10. When the optical pickup 11 irradiates the optical disk 10 with laser light, the laser light is irradiated so as to straddle the track to be traced and the adjacent track on the inner peripheral side and outer peripheral side of the track to be traced. Thereby, the reflected light of the irradiated laser beam includes the wobble signal Wa from the wobble in the range irradiated with the laser beam. The optical pickup 11 detects the reproduction signal Ws including the wobble signal Wa from the reflected light.

  The wobble signal detection unit 12 detects the wobble signal Wa from the reproduction signal Ws detected by the optical pickup 11 and outputs the wobble signal Wa to the binarization unit 15. The wobble signal Wa obtained at this time varies in amplitude of light quantity depending on the combination of the recording state of the track to be traced and the adjacent track on the inner circumference side and outer circumference side of the track to be traced as described above.

  The light amount detector 13 detects the light amount of the reflected light of each track from the reflected light of the track to be traced received by the optical pickup 11 and the adjacent track on the inner peripheral side and outer peripheral side of the track to be traced. Output to the threshold setting unit 14 as St. In addition, since the reflectance of the laser beam is different between when the recording area of each track is in a recorded state and when it is not recorded, the amount of reflected light when the recording area of the track is in a recorded state, There is a discernable difference from the amount of reflected light when the recording area is unrecorded.

  Based on the light amount signal St of each track from the light amount detection unit 13, the threshold setting unit 14 selects an optimum threshold Th corresponding to the combination of recording states of each track and outputs the selected threshold value Th to the binarization unit 15. It should be noted that the threshold value Th is set to an optimal value for all combinations of recording states of tracks in a memory (not shown) in advance or is acquired in advance by learning at the initial stage.

  The binarization unit 15 binarizes the wobble signal Wa from the wobble signal detection unit 12 using the optimum threshold Th corresponding to the combination of recording states of each track obtained from the threshold setting unit 14 as a reference. The binarized wobble signal Wb is obtained.

  The auxiliary information reproducing unit 16 demodulates the binarized wobble signal Wb obtained by the binarizing unit 15 into auxiliary information Ad including address information.

  The auxiliary information Ad including the obtained address information is output to the recording / reproducing condition setting unit 17. Based on the auxiliary information Ad demodulated by the auxiliary information reproducing unit 16, the recording / reproducing condition setting unit 17 sends a predetermined signal to the servo control circuit 18, the laser drive circuit 19 and the like, and the optical disc 10 under the conditions in accordance with the auxiliary information Ad. The information signal is recorded or reproduced.

  Next, in FIG. 2, the wobble signal binarization in the optical disk auxiliary information reproducing method according to the present invention is converted into the wobble signal Wa1, obtained in the recording state of each of the irradiation spots Sa, Sb, Sc in FIG. An example of binarization of Wa2 and Wa3 will be described. Note that the wobble signals Wa1, Wa2, and Wa3 in FIG. 2 also change the amplitude of the light amount depending on the combination of the track to be traced and the recording area of the adjacent track on both the inner and outer sides of the track as in FIG.

  When binarization of the wobble signal Wa1 obtained at the irradiation spot Sa is performed, the light amount detection unit 13 detects the light amount of reflected light from each track received by the optical pickup 11, and tracks to be traced and tracks to be traced. A light amount signal St indicating that all the recording areas of the adjacent tracks on the inner and outer peripheral sides are in an unrecorded state is output to the threshold setting unit 14. The threshold setting unit 14 receives the light amount signal St from the light amount detection unit 13 indicating that all the recording areas of each track are in an unrecorded state, and the wobble signal Wa when all the recording areas of each track are in an unrecorded state. The threshold value Th <b> 1 that is optimal for binarization is selected and output to the binarization unit 15. The binarizing unit 15 binarizes the wobble signal Wa1 using the threshold Th1 selected by the threshold setting unit 14 as a reference, and obtains a binarized wobble signal Wb4.

  When binarization of the wobble signal Wa2 obtained at the irradiation spot Sb is performed, the light amount detection unit 13 detects the light amount of reflected light from each track received by the optical pickup 11, and the inner circumference side of the track to be traced is detected. A light amount signal St indicating that the recording area of the adjacent track has been recorded and the recording area of the adjacent track on the outer periphery side of the track to be traced is in an unrecorded state is output to the threshold setting unit 14. The threshold setting unit 14 is in a state where the recording area of the adjacent track on the inner circumference side of the track to be traced from the light amount detection unit 13 is already recorded, and the recording area of the adjacent track on the outer circumference side of the track to be traced and the track to be traced is In response to the light quantity signal St indicating that the recording is not performed, the recording area of the adjacent track on the inner circumference side of the track to be traced is recorded, and the adjacent track on the outer circumference side of the track to be traced and the track to be traced is recorded. A threshold value Th2 that is optimal for binarization of the wobble signal Wa when the recording area is unrecorded is selected and output to the binarization unit 15. The binarization unit 15 binarizes the wobble signal Wa2 using the threshold Th2 selected by the threshold setting unit 14 as a reference, and obtains a binarized wobble signal Wb5.

  When binarization of the wobble signal Wa3 obtained at the irradiation spot Sc is performed, the light amount detection unit 13 detects the amount of reflected light from each track received by the optical pickup 11, and the recording area of the track to be traced is not yet recorded. In the recording state, a light amount signal St indicating that the recording areas of adjacent tracks on both the inner and outer sides of the track to be traced is in a recorded state is output to the threshold setting unit 14. The threshold setting unit 14 indicates that the recording area of the track to be traced from the light quantity detection unit 13 is in an unrecorded state, and the recording areas of adjacent tracks on both the inner and outer sides of the track to be traced are in a recorded state. The wobble signal Wa when the recording area of the track to be traced is in an unrecorded state and the recording areas of the adjacent tracks on both the inner and outer sides of the track to be traced are in a recorded state. The threshold value Th3 that is optimal for binarization is selected and output to the binarization unit 15. The binarization unit 15 binarizes the wobble signal Wa3 using the threshold Th3 selected by the threshold setting unit 14 as a reference to obtain a binarized wobble signal Wb6.

  As described above, since the optimum threshold values Th1 to Th3 are set for the wobble signals Wa1 to Wa3 and binarization is performed for the wobble signals Wa1 to Wa3, the obtained binarized wobble signals Wb4, Wb5, and Wb6 are always auxiliary. This is equivalent to the signal Wc given as information, and no deviation or the like occurs. Even if such binarized wobble signals Wb4, Wb5, and Wb6 are demodulated to auxiliary information Ad including address information by the auxiliary information reproducing unit 16, no erroneous detection or the like occurs, and the auxiliary information Ad including address information is accurately detected. Demodulated.

  In the above description, the example in which the track to be traced is an unrecorded groove track has been described. However, even if the track to be traced is a recorded track or a land track, the track can be obtained. Since the threshold Th corresponding to the light quantity signal St to be set is set, the auxiliary information Ad including the address information can be accurately demodulated by the same procedure.

  From the above, according to the optical disk reproducing method and optical disk reproducing apparatus of the present invention, it is assumed that the track to be traced and the adjacent track on the inner peripheral side and outer peripheral side of the track to be traced are in any combination of recording states. In addition, the recording state of the track to be traced and the adjacent track on the inner periphery side and the outer periphery side of the track to be traced are discriminated, and the wobble signal Wa is binarized using a threshold Th that is optimal for the combination of the recording states as a reference. Therefore, the obtained binarized wobble signal Wb is always equivalent to the signal Wc given as auxiliary information, and the auxiliary information Ad can be accurately demodulated from the binarized wobble signal Wb.

  The change in the amount of reflected light depending on the recording state of each track changes not only in the recording state of the track but also in the amount of reflected light depending on the density of recording pits. In this case, the threshold value Th in the threshold value setting unit 14 may be set by a predetermined calculation based on the light amount signal St of each track from the light amount detection unit 13. By setting the threshold Th by a predetermined calculation based on the light amount signal St, it is possible to cope with changes in the amount of reflected light depending on the density of the recording pits of the recorded track in addition to the combination of the recording states of each track. A proper threshold Th can be set as appropriate.

  In this example, the phase change type optical disk has been described as an example. However, the present invention is not limited to the phase change type optical disk. For example, the optical disk other than the phase change medium, such as a write once type optical disk, may be used. Besides being applicable, the present invention can be modified and implemented without departing from the gist of the present invention.

1 is a block diagram of an auxiliary information reproducing apparatus for an optical disc according to the present invention. It is a figure explaining the binarization of the wobble signal in the reproducing method of auxiliary information of the optical disc according to the present invention. It is a schematic diagram of a land track and a groove track of a conventional optical disc. It is the schematic diagram which showed the recording state of the land track and groove track of the conventional optical disk. It is a figure explaining the binarization of the wobble signal in the reproduction | regenerating method of the auxiliary information of the conventional optical disk.

Explanation of symbols

11 Optical pickup
12 Wobble signal detector
13 Light intensity detector
14 Threshold setting unit
15 Binarization part
16 Auxiliary information playback unit
17 Recording / playback condition setting section
50 Auxiliary information reproducing device
Ws Playback signal
Wa, Wa1, Wa2, Wa3 wobble signal
Wb, Wb1 to Wb6 Binary wobble signal
St light quantity signal
Th, Th1, Th2, Th3 threshold values
Ad auxiliary information

Claims (2)

Laser light is applied to an optical disc having grooves and lands that are alternately adjacent to each other in the radial direction and each of which can record information, and wobbles in which auxiliary information is recorded as wobble signals at the boundary between the grooves and the lands. A method of reproducing an optical disc for irradiating and reproducing the auxiliary information,
The recording state of the information in the grooves and lands in the range irradiated with the laser light is detected, and a threshold value serving as a reference for binarizing the wobble signal is set based on the recording state. A method of reproducing an optical disc, wherein the auxiliary information is obtained by binarizing the wobble signal with reference to a threshold value. Laser light is applied to an optical disc having grooves and lands that are alternately adjacent to each other in the radial direction and each of which can record information, and wobbles in which auxiliary information is recorded as wobble signals at the boundary between the grooves and the lands. An optical disk reproducing device for irradiating and reproducing the auxiliary information,
A laser beam irradiation unit for irradiating the optical disk with a laser beam;
A wobble signal detection unit for detecting the wobble signal in a range irradiated with the laser beam;
A light amount detection unit for detecting the light amount of the laser beam reflected by the optical disc;
A threshold value setting unit for setting a threshold value serving as a reference when binarizing the wobble signal based on the amount of the detected laser beam;
A binarization unit that binarizes the wobble signal on the basis of the set threshold value,
An auxiliary information reproducing unit that obtains the auxiliary information from the binarized wobble signal;
An optical disc reproducing apparatus comprising:

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