JP2008276821A - Warp detecting method of optical disk, recording method of optical disk, and optical disk recording and playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording method by which the detection of a warp direction and a warp angle of an optical disk can be performed at a low cost, and favorable recording quality can be obtained depending on the detected result. <P>SOLUTION: The recording method of the optical disk has a step for detecting the reflected light of a preceding sub-beam and a succeeding sub-beam as RF signals, respectively, a step for detecting a change in the intensity of the RF signal of the preceding sub-beam and a change in the intensity of the RF signal of the succeeding sub-beam and detecting the direction of the warp of the optical disk, a step for detecting a warp angle of the optical disk from a relation between the intensity of the RF signal of the preceding sub-beam and the intensity of the RF signal of the succeeding sub-beam, and the warp angle, and a step for correcting the direction of the laser beam for recording based on the detected direction of the warp and the detected angle of the warp of the optical disk. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disk recording method and an optical disk recording / reproducing apparatus, and detects a warp of an optical disk and corrects it based on this to prevent a decrease in recording quality.

  An optical disk such as a CD-R (recordable CD), DVD ± R (recordable DVD), or BD-R (recordable Blu-ray disk) has a recording layer and a reflective layer on one surface of a light-transmitting disk-shaped substrate. And a structure in which a protective layer is formed as necessary. A spiral or concentric groove called a groove is formed on the surface of the substrate on which the recording layer and the reflective layer are formed, and a convex part called a land is formed between adjacent grooves. In such an optical disk, recording is performed by irradiating a recording laser beam on a recording layer on the groove to form pits. The length of the pits, the portion between the pits (hereinafter referred to as a space). ) And their arrangement are read out by irradiating with a reproduction laser beam.

  In such an optical disk recording, the recording quality deteriorates due to manufacturing errors such as thickness variation and warpage of the optical disk and lens tilt of an objective lens or the like in the pickup unit of the optical disk recording / reproducing apparatus. For example, with regard to the warping of an optical disc, the recording spot quality or the reproduction laser beam is inclined with respect to the optical axis, and aberrations are generated, the beam spot power distribution changes, and the pit shape is disturbed, resulting in recording quality. There is a problem that will decrease. Therefore, the optical disc recording / reproducing apparatus needs a means for correcting the direction of the recording laser beam or the reproducing laser beam so as to follow the warp of the optical disc.

As a means for correcting the direction of the recording laser beam or the reproducing laser beam, for example, as disclosed in JP-A-11-144280, the relative tilt angle between the objective lens and the optical disk is tilted. There has been proposed an optical disc apparatus that detects an angle of an objective lens by detecting with a sensor.

Japanese Patent Laid-Open No. 2005-235348 proposes an optical disc apparatus that includes a tilt sensor that detects the tilt of the optical disc and a tilt sensor that detects the tilt of the objective lens, and performs offset adjustment of the tilt amount of the tilt sensor. Yes.

JP-A-11-144280 JP 2005-235348 A

However, the above-described prior art requires a tilt sensor for detecting the warp of the optical disk or the tilt angle of the objective lens. In addition, a circuit for driving the tilt sensor is required. Therefore, there is a problem that the structure of the optical disc recording / reproducing apparatus becomes complicated and the cost is increased.

The present invention proposes a method for detecting a warp of an optical disc, which can detect the direction of the warp and the angle of the warp at a low cost. The present invention also proposes a recording method and a recording / reproducing apparatus capable of obtaining good recording quality using this detection method.

  In the present invention, as a method of detecting the warp of the optical disk, a spiral or concentric groove is formed on one surface of the light-transmitting disk-shaped substrate, and a land is formed between adjacent grooves. A recording layer and a reflective layer are formed on the surface of the substrate where the groove and the land are formed, and information is sequentially recorded on the recording layer on the groove from the inner periphery toward the outer periphery. In a method for detecting warpage of an optical disk, a main beam to be a recording laser beam or a reproduction laser beam irradiated with a spot on an arbitrary part of the groove, and an outer periphery of the groove irradiated with the main beam The front sub-beam irradiated with the spot aligned with the land portion adjacent to the side, and the inner peripheral side of the groove irradiated with the main beam The optical disk is irradiated with a subsequent sub-beam irradiated with a spot on an adjacent land portion, and the reflected light of the preceding sub-beam and the subsequent sub-beam is detected as an RF signal, and the intensity of the RF signal is determined. Based on the above, an optical disc warpage detection method for detecting the direction and angle of warpage of the optical disc is proposed.

  The preceding sub-beam and the following sub-beam used for warpage detection in the above method are normally used for tracking, and are provided in, for example, an optical disc recording / reproducing apparatus employing the three-beam method. The optical disk warpage detection method of the present invention does not need to be newly provided with a tilt sensor or the like for detecting the warpage of the optical disk, and can be realized by using a conventionally provided device. The angle of warpage can be detected at a low cost.

  Further, in the present invention, as an optical disc recording method, a step of irradiating a recording laser beam to record information on the optical disc, and interrupting the recording and switching to a reproducing laser beam, the recorded portion of the groove Irradiating the outermost groove with a main beam of the reproduction laser beam and aligning the spot with the land adjacent to the outer peripheral side of the outermost groove of the recorded portion of the groove Irradiating a sub-beam; irradiating a subsequent sub-beam by aligning a spot with a land adjacent to the inner peripheral side of the outermost groove in the recorded portion of the groove; and the preceding sub-beam and the subsequent sub-beam Detecting the reflected light of each as an RF signal, and changing the intensity of the RF signal of the preceding sub-beam. Detecting a change in the intensity of the RF signal of the succeeding sub beam to detect the direction of warping of the optical disc; and the intensity of the RF signal of the preceding sub beam and the intensity and warping of the RF signal of the succeeding sub beam. Detecting the warp angle of the optical disc from the relationship with the angle of the optical disc, correcting the direction of the recording laser beam based on the detected warp direction and the warp angle of the optical disc, and the recording laser. And a step of resuming recording after correcting the direction of light.

According to the recording method described above, the correction of the direction of the recording laser beam is performed based on the warp direction and the warp angle of the optical disc detected based on the intensity of the RF signal of the sub beam. Information can be recorded.

Note that the decrease in the intensity of the sub-beam RF signal may be caused by a cause other than the warp of the optical disk. For this reason, depending on the direction of warping of the optical disc, it may not be possible to distinguish the decrease in RF signal intensity due to a cause other than warping. Therefore, in the present invention, in addition to the above recording method, after correcting the direction of the recording laser beam and restarting the recording, the recording is interrupted again and switched to the reproducing laser beam, and the recorded data before correction is recorded. Spotting the groove and the recorded groove after correction to irradiate the spot and outputting a reproduction signal before and after correction, and detecting the reproduction signal to detect the recording quality before and after correction. An optical disk recording method is further proposed, which further includes a step and a step of comparing the recording quality before correction with the recording quality after correction to detect the presence or absence of erroneous correction. According to this recording method, whether or not the decrease in the intensity of the sub-beam RF signal is caused by a factor other than warping is detected by detecting whether the recording quality after correction is improved or deteriorated compared to the recording quality before correction. Can be determined.

Further, in the present invention, as an optical disk recording / reproducing apparatus, a laser diode that emits a recording laser beam or a reproducing laser beam, a main beam that is irradiated with a laser beam from the laser diode with a spot aligned with the groove, A preceding sub-beam irradiated with a spot on the land adjacent to the outer peripheral side of the groove irradiated with the main beam and a land adjacent to the inner peripheral side of the groove irradiated with the main beam irradiated with the spot aligned An optical pickup unit having an optical branching unit for branching to the subsequent sub-beam, a photodetector for detecting reflected light of the preceding sub-beam and the subsequent sub-beam from the optical disc as an RF signal, and from the optical pickup unit An RF signal intensity detector that reads the RF signal and detects the intensity of the RF signal; A warp detection unit that performs calculation based on a signal from the RF signal intensity detection unit, calculates a warp direction of the optical disc and calculates a warp angle, and an optical pickup unit based on a calculation result of the warp detection unit. An optical disc recording / reproducing apparatus having an optical pickup driving control unit to be driven is proposed.

According to the recording / reproducing apparatus, it is possible to detect the direction of the warp and the angle of the warp without providing a special means such as a tilt sensor. Therefore, it is possible to obtain an optical disc recording / reproducing apparatus capable of recording information with good recording quality at low cost.

  The present invention also proposes an optical disc recording / reproducing apparatus that further includes a characteristic value detecting unit that detects a characteristic value serving as an evaluation index of recording quality by reading a reproduction signal from the optical pickup unit in addition to the recording / reproducing apparatus. . According to this recording / reproducing apparatus, it is possible to determine whether or not the decrease in the intensity of the sub-beam RF signal is caused by a cause other than warping.

  According to the present invention, it is possible to detect the warp direction and the warp angle of an optical disk at low cost, and it is possible to obtain good recording quality based on the detection result.

A functional block diagram of a recording apparatus according to an embodiment of the present invention will be described with reference to FIG. The optical disc recording / reproducing apparatus 100 has a memory 126 for storing data in the middle of processing, data of processing results, reference data in processing (for example, strategy data corresponding to each media ID), and the processing for performing the processing described below. A calculation unit 125 including a memory circuit in which a program is recorded, a laser diode drive control unit 122 that controls the recording laser beam and the reproduction laser beam, and an RF signal intensity detection unit 123 that detects the intensity of the sub-beam RF signal. A characteristic value detection unit 124 that detects a reproduction signal and detects a characteristic value used for recording quality evaluation, an optical pickup 110, and an optical pickup drive control unit that controls the direction of laser light emitted from the optical pickup. 121, a rotation control unit (not shown) and a motor (not shown) of the optical disc 150, Including servo control unit for pickup 110 (not shown) or the like.

  The optical pickup 110 also splits the light from the objective lens 114, the beam splitter 116, the detection lens 115, the collimating lens 113, the laser diode 111, the photodetector 117, and the laser diode 111 into a main beam and a sub beam. A light branching means 112 such as a diffraction grating and a tilt correcting actuator 118 for correcting the tilt angle of the objective lens 114 are included. In the optical pickup 110, an actuator (not shown) operates in accordance with control of a servo control unit (not shown), and focusing and tracking are performed. The photodetector 117 includes a detector PDm that detects the reflected light of the main beam, and detectors PDs1 and PDs2 that detect the reflected light of the sub beam.

  The calculation unit 125 is connected to the memory 126, the RF signal intensity detection unit 123, the characteristic value detection unit 124, the optical pickup drive control unit 121, the laser diode drive control unit 122, a rotation control unit and a servo control unit (not shown), and the like. . The arithmetic unit 125 functions as a warp detection unit by executing a program stored in the memory circuit. Further, the characteristic value detection unit 124 is connected to the photodetector 117 and the calculation unit 125. Further, the RF signal intensity detection unit 123 is connected to the photodetector 117 and the calculation unit 125. The optical pickup drive control unit 121 is connected to the calculation unit 125 and the optical pickup 110. The laser diode drive control unit 122 is connected to the calculation unit 125 and the laser diode 111. The arithmetic unit 125 is also connected to an input / output system (not shown) via an interface unit (not shown).

  Next, an outline of processing when data is recorded on the optical disc 150 will be described. First, the arithmetic unit 125 or a separately provided data modulation circuit (not shown) performs a modulation process on the data to be written on the optical disc 150, and the data after the modulation process is converted into the laser diode drive control unit 122. Output to. The laser diode drive control unit 122 drives the laser diode 111 with the received data according to specified recording conditions to output a recording laser beam. The recording laser light is irradiated onto the optical disc 150 through the light branching means 112, the collimating lens 113, the beam splitter 116, and the objective lens 114, thereby forming spaces and pits on the optical disc 150.

  An outline of processing when data recorded on the optical disc 150 is reproduced will be described. In accordance with an instruction from the calculation unit 125, the laser diode drive control unit 122 drives the laser diode 111 to output a reproduction laser beam. The reproducing laser light is irradiated onto the optical disc 150 through the light branching means 112, the collimating lens 113, the beam splitter 116, and the objective lens 114. The reflected light from the optical disk 150 is input to the PD 117 via the objective lens 114, the beam splitter 116, and the detection lens 115. The PD 117 converts the reflected light from the optical disc 150 into an electrical signal and outputs it to a data demodulation circuit (not shown) or the like. The data demodulating circuit performs predetermined decoding processing on the output reproduction signal, and displays the decoded data on an input / output system (not shown) via the arithmetic unit 125 and the interface unit (not shown). To display the playback data.

  Next, a method for detecting the warpage of the optical disk according to the present invention will be described with reference to FIGS. FIG. 2B is a partially enlarged view showing a state in which the optical disc 150 is irradiated with the main beam, the preceding sub beam, and the subsequent sub beam. Grooves GV1 and GV2 are recorded grooves, and groove GV2 is the outermost periphery of the recorded grooves. The groove GV3 is an unrecorded groove. A land LN1 is formed between the groove GV1 and the groove GV2, and a land LN2 is formed between the groove GV2 and the groove GV3. The main beam is irradiated with the spot on the groove GV2 to form a main spot MB. The preceding sub beam irradiates the land LN2 adjacent to the outer peripheral side of the groove GV2 with a spot so as to form a preceding sub spot SB1. The preceding sub-spot SB1 is disposed before the traveling direction of the main spot MB, and the succeeding sub-spot SB2 is disposed behind the traveling direction of the main spot MB. Here, the preceding and following indicate the positional relationship with respect to the main spot when viewed in the radial direction. Since the optical disc is recorded from the inner periphery toward the outer periphery, the outer periphery side is preceding and the inner periphery side is following. It becomes. Therefore, the preceding sub spot SB1 may be disposed behind the main spot MB in the traveling direction, and the trailing sub spot SB2 may be disposed before the main spot MB in the traveling direction. Reflected light from the main spot MB, the preceding sub-spot SB1, and the subsequent spot SB2 are detected by the detectors PDm, PDs1, and PDs2, respectively, thereby generating a reproduction signal and a sub-beam RF signal.

  As shown in FIG. 2A, when the optical disk is not warped, no aberration occurs in the irradiated beam, and the power distribution becomes a beam spot having symmetry. The main spot MB is formed in accordance with the groove GV2, and the preceding sub spot SB1 and the subsequent sub spot SB2 are formed in accordance with the land LN2 and the land LN1, respectively. At this time, the preceding sub-spot SB1 and the succeeding sub-spot SB2 are formed so as not to cover the grooves GV1, GV2, and GV3.

  FIGS. 3A and 4A show a state in which the optical disk is warped. The warp of the optical disk is bent toward the light source of the beam as shown in FIG. 3 (a), and is bent toward the opposite side of the light source of the beam as shown in FIG. 4 (a). There is. Here, a warp as shown in FIG. 3A is a positive warp, and a warp as shown in FIG. 4A is a negative warp.

  In the case of plus warping, the power distribution of the beam spot shifts to the outer peripheral side, so that the main spot MB, the preceding sub spot SB1, and the subsequent sub spot SB2 spread toward the outer peripheral side as shown in FIG. Formed. As a result, the preceding sub spot SB1 is formed so as to cover the groove GV3 adjacent to the outer peripheral side of the land LN2, and the subsequent sub spot SB2 is formed so as to cover the groove GV2 adjacent to the outer peripheral side of the land LN1. The succeeding sub spot SB2 reads the pit PT formed in the groove GV2, and the intensity of the RF signal of the sub beam changes. A state in which the intensity of the RF signal of the sub beam is changed by reading the pits of the groove adjacent to the sub spot in this way is referred to as crosstalk. On the other hand, the preceding sub-spot SB1 is in the groove GV3, but since no pit is formed in the groove GV3, the intensity of the sub-beam RF signal hardly changes. Therefore, no crosstalk occurs.

  In the case of negative warping, the power distribution of the beam spot shifts to the inner peripheral side, so that the main spot MB, the preceding sub spot SB1, and the subsequent sub spot SB2 are directed toward the inner peripheral side as shown in FIG. It is formed to spread. As a result, the preceding sub spot SB1 is formed so as to cover the groove GV2 adjacent to the inner peripheral side of the land LN2, and the subsequent sub spot SB2 is formed so as to cover the groove GV1 adjacent to the inner peripheral side of the land LN1. . Since the succeeding sub spot SB2 reads the pit PT formed in the groove GV1, the intensity of the sub beam RF signal changes and crosstalk occurs. On the other hand, since the preceding sub spot SB1 reads the pit PT formed in the groove GV2, the intensity of the RF signal of the sub beam changes and crosstalk occurs.

  The above results are summarized in the table shown in FIG. According to this table, it is possible to determine whether the direction of the warp of the optical disc is a positive warp or a negative warp by detecting the presence / absence of crosstalk of the sub beam. Also, as the angle of warpage increases, the area of the sub-spot that covers the groove increases, so that the intensity of the RF signal of the sub-beam when crosstalk occurs changes more greatly. FIG. 6 is a graph showing the relationship between the warp angle of the optical disk and the intensity of the RF signal of the sub beam. By using the relationship between the warp angle and the intensity of the RF signal of the sub beam, the warp angle can be detected. The relationship between the angle of the warp and the intensity of the RF signal of the sub beam may be input from the outside to the memory circuit of the arithmetic unit of the optical disc recording / reproducing apparatus 100 and read, or the medium ID (for specifying the manufacturer, etc.) It may be stored in the memory 126 as strategy data corresponding to (identification data) and read when necessary.

  Next, the recording method of the present invention will be described with reference to FIG. FIG. 7 is a flowchart showing a recording procedure on the optical disc 150. First, the optical disc 150 is inserted into the optical disc recording / reproducing apparatus 100 (S1). The optical disc recording / reproducing apparatus 100 reads a media ID recorded in advance on the optical disc 150 (S2). Subsequently, the strategy corresponding to the media ID is read from the memory 126 (S3). Subsequently, after the optimum output of the recording laser beam is specified in accordance with the read strategy data, recording on the optical disc 150 is started (S4). Subsequently, the recording is temporarily interrupted (S5). Since there is almost no warpage on the inner peripheral side, recording is performed without correction, and the process is interrupted when reaching an area where the influence of the warpage is expected to start.

  Subsequently, the recording laser beam is switched to the reproducing laser beam so that the main spot MB is aligned with the outermost groove GV2 of the recorded grooves. At the same time, the preceding sub spot SB1 is aligned with the land LN2 adjacent to the outer peripheral side of the groove GV2, and the subsequent sub spot SB2 is aligned with LN1 adjacent to the inner peripheral side of the groove GV2. (S6).

  Subsequently, the reflected light of the preceding sub-spot SB1 and the succeeding sub-spot SB2 is detected by the detectors PDs1 and PDs2 of the photodetector 117 to detect the RF signal of each sub-beam, and the intensity of the RF signal of this sub-beam is detected by the RF signal intensity detecting unit. 123 (S7). Based on the detected intensity change of the RF signal of the preceding sub-beam and the succeeding sub-beam, each intensity change is detected, and based on this, the calculation unit 126 determines whether the plus warp or the minus warp according to the determination criteria shown in the table of FIG. Determine (S8).

  If it is determined in step S8 that the warp is positive, the calculation unit 126 calculates the warp angle of the optical disc using the relationship between the warp angle of the optical disc and the intensity of the sub-beam RF signal as shown in FIG. (S9). Subsequently, based on the calculated warp angle, a control signal is transmitted from the calculation unit 126 to the optical pickup drive control unit 121, the tilt correction actuator 118 is driven to perform tilt correction of the objective lens 114, and the direction of the laser light Is corrected (S10). Note that when tilt correction is performed, the entire optical pickup 110 may be driven. In this manner, steps S4 to S10 are repeated until recording on the optical disc 150 is completed (S11).

  If it is determined in step S8 that the warp is negative, the warp angle of the optical disk is calculated in the same manner as in the case of positive warp (S81), and the tilt correction actuator 118 is driven to perform tilt correction of the objective lens 114, thereby performing the laser. The direction of light is corrected (S82). Here, in the case of negative warping, the intensity of the RF signal changes in both the preceding sub spot SB1 and the subsequent sub spot SB2. Therefore, the following steps are performed in order to distinguish from changes in the RF signal due to causes other than warping.

  First, after correcting the tilt of the objective lens 114, the recording is resumed, and then the recording is interrupted again. Next, switching to the reproduction laser beam, the main spot MB is aligned with the recorded groove before correction and the recorded groove after correction, and the reflected light is detected by the detector PDm of the photodetector 110, before and after correction. Are output respectively. Subsequently, the output reproduction signal is transmitted to the characteristic detector 124, and a characteristic value used for evaluation of recording quality is detected (S83). The characteristic value used for recording quality evaluation includes a DCJ (Data Clock Jitter) value, an asymmetry value, or a β value.

  Next, based on the characteristic value detected in step S83, the recording quality before and after lens tilt correction is compared (S84). If the recording quality is improved, it is determined that the cause of the change in the intensity of the RF signal is warping, and the process proceeds to step S11. On the other hand, if the recording quality is deteriorated, it is determined that the cause of the change in the intensity of the RF signal is other than warping, and the corrected tilt angle is returned to the angle before correction (S85). Thereafter, the process proceeds to step S11.

  The recording method of the present invention has been described based on the flowchart of FIG. 7. The procedure of the flowchart can be executed by an existing optical disc recording / reproducing apparatus by causing the memory circuit of the arithmetic unit 125 to read in the form of a program. is there. Accordingly, it is not necessary to use a special recording / reproducing apparatus having a tilt sensor or the like for detecting the warp of the optical disk, and it becomes possible to detect the warp and correct the direction of the laser at a low cost.

It is a functional block diagram which shows the optical disk recording / reproducing apparatus of this invention. (A) is a schematic diagram showing the relationship between a disk and a beam when there is no warp, and (b) is a schematic diagram showing the arrangement of main spots and sub-spots when there is no warp. (A) is a schematic diagram showing the relationship between a disk and a beam in the case of plus warping, and (b) is a schematic diagram showing the arrangement of main spots and sub-spots in the case of plus warping. (A) is a schematic diagram showing the relationship between the disk and the beam in the case of negative warping, and (b) is a schematic diagram showing the arrangement of main spots and sub-spots in the case of negative warping. It is a table | surface which shows the relationship between the presence or absence of the crosstalk of a sub beam, and the direction of curvature. It is a graph which shows the relationship between the angle of curvature of an optical disk, and the intensity | strength of the RF signal of a sub beam. It is a flowchart which shows the recording method of this invention.

Explanation of symbols

100 Optical disc recording / reproducing apparatus
110 Optical pickup
111 Laser diode
112 Optical branching means 113 Collimating lens
114 Objective lens 115 Detection lens 116 Beam splitter 117 Photo detector 118 Tilt correction actuator 121 Optical pickup drive control unit 122 Laser diode drive control unit 123 RF signal intensity detection unit 124 Characteristic value detection unit 125 Calculation unit 126 Memory 150 Optical disk

Claims (5)

A spiral or concentric groove is formed on one surface of the light-transmitting disk-shaped substrate, a land is formed between adjacent grooves, and the surface of the substrate on which the groove and the land are formed. In a method for detecting warpage of an optical disc in which a recording layer and a reflective layer are formed and information is sequentially recorded on the recording layer on the groove from the inner periphery toward the outer periphery,
A main beam serving as a recording laser beam or a reproduction laser beam irradiated with a spot on an arbitrary portion of the groove, and a spot on a land portion adjacent to the outer peripheral side of the groove irradiated with the main beam Irradiating the optical disc with a preceding sub-beam irradiated together and a subsequent sub-beam irradiated with a spot aligned with a portion of the land adjacent to the inner peripheral side of the groove irradiated with the main beam,
A method of detecting a warp of an optical disc, wherein the reflected light of the preceding sub beam and the subsequent sub beam is detected as an RF signal, and the warp direction and the warp angle of the optical disc are detected based on the intensity of the RF signal. . A spiral or concentric groove is formed on one surface of the light-transmitting disk-shaped substrate, a land is formed between adjacent grooves, and the surface of the substrate on which the groove and the land are formed. In the recording method of the optical disc, wherein a recording layer and a reflective layer are formed, and information is sequentially recorded on the recording layer on the groove from the inner periphery toward the outer periphery,
Irradiating a recording laser beam to record information on the optical disc;
Suspending the recording and switching to the reproducing laser beam, irradiating the main beam of the reproducing laser beam with a spot on the outermost groove of the recorded portion of the groove; and
Irradiating the preceding sub-beam with a spot on a land adjacent to the outer peripheral side of the outermost groove of the recorded portion of the groove;
Irradiating a trailing sub-beam by aligning a spot with a land adjacent to the inner peripheral side of the outermost peripheral groove of the recorded portion of the groove;
Detecting the reflected light of the preceding sub-beam and the subsequent sub-beam as RF signals respectively;
Detecting a change in intensity of the RF signal of the preceding sub-beam and a change in intensity of the RF signal of the subsequent sub-beam to detect the direction of warping of the optical disc;
Detecting the warp angle of the optical disc from the relationship between the RF signal intensity of the preceding sub-beam and the RF signal intensity of the subsequent sub-beam and the warp angle;
Correcting the direction of the recording laser beam based on the detected warp direction and the warp angle of the optical disc;
Resuming recording after correcting the direction of the recording laser beam;
An optical disc recording method comprising:   After correcting the direction of the recording laser beam and restarting recording, the recording is interrupted again and switched to the reproducing laser beam, and the spot is aligned with the recorded groove before correction and the recorded groove after correction. Irradiating and outputting a reproduction signal before and after correction, detecting the reproduction signal and detecting recording quality before and after correction, recording quality before correction and recording after correction The optical disk recording method according to claim 2, further comprising a step of comparing the quality and detecting the presence or absence of erroneous correction. A spiral or concentric groove is formed on one surface of the light-transmitting disk-shaped substrate, a land is formed between adjacent grooves, and the surface of the substrate on which the groove and the land are formed. In a recording / reproducing apparatus in which a recording layer and a reflective layer are formed, and recording is performed on an optical disc configured such that information is sequentially recorded on the recording layer on the groove from the inner periphery toward the outer periphery.
A laser diode that emits a recording laser beam or a reproducing laser beam; and
A main beam irradiated with a laser beam from the laser diode with a spot aligned with the groove, and a preceding sub-beam irradiated with a spot aligned with a land adjacent to the outer peripheral side of the groove irradiated with the main beam; A light branching means for branching to a sub beam that is irradiated with a spot on a land adjacent to the inner peripheral side of the groove irradiated with the main beam;
A photodetector for detecting reflected light of the preceding sub-beam and the succeeding sub-beam from the optical disc as an RF signal;
An optical pickup unit having
An RF signal intensity detection unit that detects an RF signal intensity by reading an RF signal from the optical pickup unit;
A warp detecting means for performing calculation based on a signal from the RF signal intensity detecting unit, detecting a warp direction of the optical disc and calculating a warp angle;
An optical pickup drive control unit for driving the optical pickup unit based on a calculation result of the warp detection means;
An optical disc recording / reproducing apparatus comprising: 5. The optical disk recording / reproducing apparatus according to claim 4, further comprising a characteristic value detecting unit that reads a reproduction signal from the optical pickup unit and detects a characteristic value that is an evaluation index of recording quality.

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