JP4695585B2 - Optical disc recording method and optical disc recording apparatus - Google Patents

Description

  The present invention relates to a recording method and a recording apparatus for optimizing the power of a recording laser beam when recording data on an optical disk.

  An optical disk such as CD-R (recordable CD), DVD ± R (recordable DVD), or BD-R (recordable Blu-ray Disc) has a recording layer and a reflective layer on one surface of a light-transmitting circular 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. 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.

  When a recording layer is irradiated with a recording laser beam to form pits, heat may be generated and the shape of the pits may be deformed, resulting in a decrease in recording characteristics (for example, jitter characteristics). In order to prevent the deformation of the pits, the power of the recording laser beam is adjusted. The power adjustment of the recording laser beam is performed as follows. First, recording is performed by changing the output of the recording laser beam in a power calibration area (for example, an area called PCA in the DVD-R) located on the inner circumference side of the data recording area of the optical disk. Next, an optimum output is calculated from the recording result. Next, recording is performed in the data recording area of the optical disk with the recording laser beam having the output thus obtained.

However, the recording sensitivity of the recording layer of the optical disk is not constant within the disk surface and may vary depending on production conditions. In such an optical disk, since the optimum output of the recording laser beam changes, there may occur a portion where optimum recording characteristics cannot be obtained when recording is performed with the output calculated by the above method fixed. In view of such problems, a so-called ROPC (Running Optimum Power Control) has been proposed that performs recording in the data area and simultaneously detects the recording state and corrects the output of the recording laser beam based on the result. Yes.

For example, Japanese Patent Application Laid-Open No. 2003-263740 discloses an index for detecting the recording light state of a recording disk from the output of a recording laser beam and a predetermined coefficient by detecting the reflected light level of a recording pit and the reflected light level of a recording space. And a method of controlling the output of the recording laser beam based on this index is disclosed. Japanese Patent Laid-Open No. 2003-228840 discloses a method that enables ROPC by using the rate of change of the degree of modulation during recording and reproduction as an index for determining the output of the recording laser beam.

JP 2003-263740 A JP 2003-228840 A

However, in the above-described prior art, only the signal amplitude of the pit formation portion or space portion of the write RF signal (signal obtained by detecting the reflected light of the disc at the time of recording) is detected. Can only be detected. Since the detected modulation changes depending on the optical disk, recording speed, and recording pulse setting, a correction coefficient is required for each recording condition, or for CAV (Constant Angular Velocity) recording in which the recording speed fluctuates within the optical disk surface. There was a problem that it was not suitable.

In other words, each time recording conditions such as the recording speed change, the recording is interrupted and the output is corrected, so that there is a problem that the recording time becomes long and high-speed recording becomes difficult. This problem has become more prominent as the recording density of the optical disk increases.

The present invention solves such problems and proposes a recording method capable of performing optimal ROPC control without interrupting recording even when the recording conditions fluctuate.

  In the present invention, as a first solution, a test recording step for performing test recording by changing the output of the recording laser beam in a predetermined pattern in the power calibration area of the optical disc, and for recording based on the result of the test recording An optical disc recording method comprising: an output calculation step for calculating an output of a laser beam; and a data recording step for optimally recording data in a data recording area of the optical disc by an output of the recording laser beam calculated in the output calculation step. In the data recording step, the recording state by the main beam of the recording laser beam is sequentially detected by the sub beam, and the asymmetry value detecting step for detecting the recording asymmetry value from the detection result, and the recording asymmetry value is constant. And an output correction step for correcting the output of the recording laser beam, The asymmetry value detecting step includes: a sub-beam RF signal sampling step for sampling a sub-beam RF signal detected by the sub-beam; an evaluation index sampling step for sampling an evaluation index derived based on the sub-beam RF signal; A discriminating step for discriminating whether or not the sub-beam RF signal is an extremum by the evaluation index, and proposes an optical disc recording method.

The recording state of the optical disk is usually determined based on the asymmetry value, and it is possible to obtain an optimum recording state by performing output control so that the asymmetry value becomes constant. According to the first solution, since recording is performed while detecting the asymmetry value in real time, the deviation between the detected asymmetry value and the target asymmetry value can be corrected in real time, and the asymmetry value during recording can be kept constant. Recording can be performed while maintaining.

In addition, as an evaluation index in the first solving means, there are a method using a differential signal of a sub-beam RF signal and a method using a tangential push-pull signal. The differential signal of the sub-beam RF signal is obtained by differentiating the sub-beam RF signal. When the value is 0, the sub-beam RF signal is determined as an extreme value, that is, a peak voltage or a bottom voltage in the data length of the pit or space at that time. The tangential push-pull signal detects the intensity difference of the sub-beam photodetectors divided in the linear velocity direction. When the value is 0, the sub-beam RF signal is the extreme value or peak in the data length of the pit or space at that time. Voltage or bottom voltage.

  In the present invention, as the second solving means, the output calculating step in the first solving means detects the recording asymmetry value in the test recording step, and the recording state in the test recording step is for reproduction. Detecting with a laser beam and detecting a reproduction asymmetry value from the result, and calculating a recording laser beam output from the relationship between the recording asymmetry value and the reproduction asymmetry value. A featured optical disk recording method is proposed.

According to the second solution means, the sensitivity difference and offset in the asymmetry detection means between the asymmetry during reproduction and the asymmetry during recording can be canceled, so that the asymmetry value during reproduction in the optimum recording state can be obtained. The target value of asymmetry during recording can be set, and good recording can be performed.

  Further, in the present invention, as an apparatus for realizing such a solution, a recording unit that performs recording by irradiating a recording laser beam on an optical disc, an output calculation unit that calculates an output of the recording laser beam, Output control means for controlling the output of the pre-recording laser light based on the result calculated by the output calculating means, wherein the recording means comprises a laser diode for emitting the recording laser light, An optical branching means for branching the recording laser light from the laser diode into a main beam and a sub-beam, and a photodetector for detecting reflected light of the main beam and the sub-beam from the optical disk as an RF signal, the output calculating means Is an evaluation index deriving means for deriving an evaluation index based on the sub-beam RF signal detected by the photodetector Sampling means for discriminating whether or not the sub-beam RF signal sampled by sampling the sub-beam RF signal and the evaluation index is an extremum, and recording asymmetry based on the data sampled by the sampling means An optical disc recording apparatus comprising: an asymmetry value detecting means for detecting a value; and an output correcting means for correcting the output of the recording laser beam so that the recording asymmetry value is constant. To do.

  According to the above apparatus, by detecting the recording state with the sub beam branched from the recording laser beam, the data is not affected by the change in the state of the optical disk, the change in the recording speed, or the change in the recording pulse. It becomes possible to automatically control the output of the recording laser beam during recording.

  According to the present invention, even when recording conditions such as recording sensitivity, recording speed, or recording pulse of the recording layer of the optical disk fluctuate, optimal ROPC control can be performed without interrupting recording.

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 recording pulse generation unit 122 that generates a recording laser light pulse and generates a signal indicating the sampling timing of a sub-beam RF signal that is a reproduction signal; An evaluation index deriving circuit 123 for deriving a signal serving as an evaluation index from the RF signal, a signal for instructing a sampling timing from the recording pulse generation unit 122, and a signal from the evaluation index deriving circuit 123, sampling of the sub beam RF signal. Sampling circuit 124 to perform and pick up Including a part 110, an output control section 121, a servo control unit or the like for rotation control section and the motor and the pickup unit 110 of the optical disc 150 (not shown).

  The pickup unit 110 also branches the light from the objective lens 114, the beam splitter 116, the detection lens 115, the collimator lens 113, the laser diode 111, the photodetector 117, and the laser diode 111 into a main beam and a sub beam. An optical branching unit 112 such as a diffraction grating is included. In the pickup unit 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 sampling circuit 124, the output control unit 121, a rotation control unit and a servo control unit (not shown), and the like. The arithmetic unit 125 functions as an asymmetry value detection unit, an optimization determination unit, and an output correction unit by executing a program stored in the memory circuit. Further, the sampling circuit 124 is connected to the photodetector 117, the calculation unit 125, the evaluation index derivation circuit 123, the recording pulse generation unit 122, and the like. The output control unit 121 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 data modulation circuit (not shown) provided separately performs a modulation process on the data to be written on the optical disc 150 and outputs the data after the modulation process to the output control unit 121. To do. The output control unit 121 drives the laser diode 111 with the received data according to the specified recording condition 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 to form pits in the recording layer of the optical disc 150.

  An outline of processing when data recorded on the optical disc 150 is reproduced will be described. The output control unit 121 drives the laser diode 111 in accordance with an instruction from the calculation unit 125 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. Reflected light from the optical disk 150 is input to the photodetector 117 via the objective lens 114, the beam splitter 116, and the detection lens 115. The photodetector 117 converts the reflected light from the optical disc 150 into an electric 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, the optical disk recording method according to the first embodiment will be described with reference to FIGS. The description here will be made for the case where the shortest data length minus the longest data length is an asymmetry value of 3T-14T, but the same applies to the case of 3T-11T, 2T-8T, or 3T-8T, for example. FIG. 2 is a schematic diagram showing a state in which recording on the optical disc 150 is performed. Recording on the optical disc 150 is performed by irradiating the recording layer on the groove GV of the optical disc with the main beam MB of the recording laser beam to form pits. The sub-beam SB1 of the recording laser light is disposed in front of the main beam MB, and the sub-beam SB2 is disposed behind the main beam MB. The reflected light of the main beam MB and the sub beams SB1 and SB2 is detected by the detectors PDm, PDs1 and PDs2, respectively, thereby generating a write RF signal and a sub beam RF signal. The detectors PDm, PDs1, and PDs2 are divided into two to four. For example, in the main beam MB, it is possible to detect a light intensity difference between areas A, B, C, and D. Since it is the sub beam SB2 that can detect the recording state by the main beam MB, the sub beam RF signal is assumed to be that of the sub beam SB2 behind the main beam MB in the traveling direction.

  FIG. 3 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 (identification data for specifying a manufacturer or the like) 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, according to the read strategy data, test recording is performed so as to form a predetermined pit and space pattern in the power calibration area of the optical disc 150 (S4). In order to specify the optimum output of the recording laser beam, different recording powers are set in the output control unit 121 and are written a predetermined number of times for predetermined pit and space patterns.

  Subsequently, the optimum output of the recording laser beam and the target asymmetry value are specified from the result of the test recording by the asymmetry value detection means and the optimization determination means of the calculation unit 125 (S5). The optimum output of the laser beam for recording is evaluated by, for example, an asymmetry value for the pattern written in the power calibration area in the test recording, and the output of the laser beam having the optimum asymmetry value read in advance corresponding to the media ID is set. The above-mentioned optimum asymmetry value is set as the target asymmetry value. At this time, the pattern written in the test recording is evaluated by the recording characteristics such as jitter characteristics, the recording laser output that gives the best result is set as the optimum recording laser output, and the asymmetry value at that time is also set as the target asymmetry value. good.

  Subsequently, a control signal is sent from the output correction means of the calculation unit 125 to the output control unit 121 based on the optimum output of the recording laser beam and the target asymmetry value specified in step S5, whereby the laser diode 111 records the recording laser. Data is recorded on the recording area of the optical disc 150 by irradiating light (S6). When the data recording ends, the flowchart of FIG. 3 ends.

  Here, the process performed in step S6 will be described based on the flowchart of FIG. First, pits are formed in the recording area of the optical disc 150 by the main beam MB set to the optimum output of the recording laser light specified in step S5, and the pits and spaces are sequentially read by the reflected light of the sub beam SB2, and the sub beam RF Generate a signal. Based on this sub-beam RF signal, the asymmetry value at the time of recording is detected by the asymmetry value detection means of the calculation unit 125 (S61). Subsequently, the optimization judgment unit of the calculation unit 125 compares the recording asymmetry value detected in step S61 with the target asymmetry value specified in step S5, and detects the difference (S62). Subsequently, it is determined whether or not the difference detected in step S62 is within a predetermined range, and it is determined whether or not the output of the recording laser beam needs to be corrected (S63). Based on the determination in step S63, if necessary, a control signal is sent from the output correction means of the calculation unit 125 to control the output control unit 121 to perform output correction. If not necessary, output correction is not performed (S64). . Steps S61 to S64 are repeated until the data recording is completed (S65). In this way, recording on the optical disc 150 is performed by ROPC control.

  Further, the process performed in step S61 will be described with reference to FIGS. First, the reflected light of the sub beam SB2 is received by the detector PDs2, and a sub beam RF signal is generated. Next, the sub beam RF signal is read into the sampling circuit 124 (S611). Details of step 611 are as follows. The laser diode 111 irradiates the recording laser beam with the output signal shown in FIG. 6B, for example, under the control of the output control unit 121 and the recording pulse generation unit 122.

  At this time, the recording pulse generator 122 generates a sampling timing signal shown in FIG. 6A, and this sampling timing signal is input to the sampling circuit 124. This sampling timing signal is generated at a timing at which a stable portion of the output signal in FIG. 6B can be sampled. Since the center pulse of the output signal is relatively stable, it is desirable to generate the sampling timing signal when the recording pulse has a long data length so that the center pulse can be taken as long as possible. In this case, the data length is preferably 6T or more. It is assumed that the signals in FIGS. 6A to 6G are synchronized.

  On the other hand, the sub beam SB2 passes through pits and spaces shown in FIG. 6C, for example. When the pits and spaces shown in FIG. 6C are read with a beam having a constant light intensity, the generated sub-beam RF signal has a waveform shown in FIG. However, since the sub beam SB2 is branched from the main beam, it has a change in light intensity shown in FIG. 6 (e). Therefore, the sub-beam RF signal has a waveform as shown in FIG. The sub beam RF signal thus generated is sampled by the sampling circuit 124.

  Subsequently, the sub-beam RF signal is read into an evaluation index deriving circuit 123 (here, referred to as a differentiating circuit), and a differential signal of the sub-beam RF signal as shown in FIG. 6G is derived. The differential signal of the sub beam RF signal is sampled by the sampling circuit 124 (S612).

  Subsequently, it is determined whether or not the sampling value of the sub beam RF signal is an extreme value (maximum value or minimum value) (S613). By the sampling timing signal in FIG. 6A, the points A and B are sampled for the sub-beam RF signal in FIG. It is determined whether or not the value of the differential signal of the sub beam RF signal in FIG. In this case, it is determined that point A is not an extreme value because the value of the differential signal of the sub-beam RF signal is not zero. On the other hand, point B is determined to be an extreme value because the differential signal value of the sub-beam RF signal is zero.

  The sampling value determined to be an extreme value is stored in the memory 126 (S614), and, for example, steps S611 to S614 are repeated until a predetermined number of samples are sampled (reproduction area end) (S615). The stored sampling data becomes the peak voltage or the bottom voltage of each pit and space as shown in the eye pattern of FIG.

  Subsequently, in the asymmetry value detection means of the calculation unit 125, the sampling value stored in the memory 126 is plotted with the signal voltage and the number of samples to create a histogram as shown in FIG. 8 (S616). When the sampling values are averaged, an average value C is calculated. The peak I3H closest to the average value C on the higher voltage side than the average value C is the peak voltage of the shortest pit, and the peak I3L closest to the average value C on the lower voltage side than the average value C is the bottom voltage of the shortest space. is there. The peak I14H farthest from the average value C on the higher voltage side than the average value C is the longest pit peak voltage, and the peak I14L farthest from the average value C on the lower voltage side than the average value C is the longest space bottom voltage. It is.

Subsequently, using the peak voltage of the longest pit and the shortest pit obtained in step 616 and the bottom voltage data of the longest space and the shortest space,
Asymmetry value =
{(I3H + I3L) / 2- (I14H + I14L) / 2} / (I14H-I14L)
The asymmetry value at the time of recording is calculated by the formula shown by (S617). After calculating the recording asymmetry value in this way, the process proceeds to step S62 in the flowchart of FIG.

  Next, an optical disk recording method according to the second embodiment will be described with reference to FIGS. The second embodiment is different from the first embodiment in that a tangential push-pull signal is used as an evaluation index in the recording asymmetry value detection method.

  FIG. 9 is a schematic diagram showing a state in which recording on the optical disk 150 is performed. The tangential push-pull signal is represented by a difference in light intensity before and after the traveling direction. Therefore, the detector PDs2 that detects the reflected light of the sub beam is divided into front and rear. Here, the tangential push-pull signal is (G1 + H1) − (G2 + H2).

  FIG. 10 shows a flowchart of recording asymmetry value detection. The sub-beam RF signal is sampled in the same manner as in the first embodiment (S611), the sub-beam tangential push-pull signal is sampled (S612 '), and the sub-beam tangential push-pull signal of the sampled sub-beam RF signal is 0. It is determined whether or not there is (S613 ′). Since the fact that the tangential push-pull signal becomes 0 indicates that there is no difference in light intensity before and after the detector PDs2, it is determined that the sampling value is an extreme value. Thereafter, as in the first embodiment, the extreme sampling value is stored in the memory 126 (S614), and steps S611 to S614 are repeated until a predetermined number of samples are sampled (reproduction area end) (S615). Then, a histogram is created based on the sampling value (S616), and the recording asymmetry value is calculated (S617).

  Next, an optical disk recording method according to the third embodiment will be described with reference to FIG. FIG. 11 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 (S11). The optical disc recording / reproducing apparatus 100 reads the media ID recorded in advance on the optical disc 150 (S12). Subsequently, the strategy corresponding to the media ID is read from the memory 126 (S13). Subsequently, according to the read strategy data, test recording is performed so as to form a predetermined pit and space pattern in the trial writing area of the optical disc 150 (S14).

  Subsequently, a recording asymmetry value is detected in this test recording (S15). FIG. 5 (evaluation index: differential signal of sub-beam RF signal) or FIG. 10 (evaluation index: tangential push-pull signal) is used for the method of detecting the asymmetry value during recording.

  Subsequently, a reproduction laser beam is irradiated to a predetermined pit and space pattern formed in the test recording, and an asymmetry value during reproduction is detected (S16). The reproduction laser beam has a constant output, and the asymmetry value is obtained by a normal calculation method.

  Subsequently, the calculation unit 125 calculates the relationship between the recording asymmetry value and the reproduction asymmetry value (S17). A recording asymmetry value of a certain test recording pattern and a reproducing asymmetry value obtained by reproducing the same test recording pattern with a reproducing laser beam are obtained, and this is performed for a plurality of test recording patterns. A correlation graph as shown in FIG.

  Subsequently, the reproducing asymmetry value X when the optimum recording state is reached is determined, and the recording asymmetry value Y at that time is specified as the target asymmetry value (S18). The reproduction asymmetry value X may be read and used if there is data of the optimum asymmetry value corresponding to the media ID.

  Subsequently, the output control unit 121 irradiates the recording laser beam from the laser diode 111 based on the optimum output of the recording laser beam specified in step S18 and the target asymmetry value, and records data in the recording area of the optical disc 150. Perform (S19). The data recording in step S19 is performed according to the procedure of the flowchart shown in FIG. Note that the recording asymmetry value calculation method in the data recording step S19 is different from the method in step S15, that is, one is a method using a differential signal of a sub-beam RF signal and the other is a method using a tangential push-pull signal. Good. However, considering the simplicity of the apparatus and the like, both are preferably performed by the same method. According to the third embodiment, the sensitivity difference and offset in the asymmetry detection means between the asymmetry during reproduction and the asymmetry during recording can be canceled, so that the asymmetry during recording can be controlled with higher accuracy.

It is a functional block diagram which shows the optical disk recording / reproducing apparatus of this invention. It is a schematic diagram which shows the state which is recording on the optical disk in 1st embodiment of this invention. It is a flowchart which shows the recording procedure to the optical disk in 1st embodiment of this invention. It is a flowchart which shows the procedure of output correction | amendment. It is a flowchart which shows the procedure which calculates the recording asymmetry value in 1st embodiment of this invention. (A) is a sampling timing signal, (b) is an output signal of a recording laser beam, (c) is a pit and space read by a sub beam, (d) is a waveform of an RF signal when the light intensity is constant, ( e) is an output signal of the sub beam, (f) is a sub beam RF signal, and (g) is a differential signal of the sub beam RF signal. It is a figure which shows the image of sampling. It is the histogram calculated | required from the sampling value. It is a schematic diagram which shows the state which is recording on the optical disk in 2nd embodiment of this invention. It is a flowchart which shows the procedure which calculates the asymmetry value at the time of recording in the 2nd embodiment of this invention. It is a flowchart which shows the recording procedure to the optical disk in 3rd embodiment of this invention. It is a graph which shows the correlation of the recording asymmetry value and reproduction | regeneration asymmetry value of step S17 and step S18 in 3rd embodiment of this invention.

Explanation of symbols

100 Optical disc recording / reproducing apparatus
110 Pick-up part
111 Laser diode
112 Optical branching means 113 Collimating lens
DESCRIPTION OF SYMBOLS 114 Objective lens 115 Detection lens 116 Beam splitter 117 Photo detector 121 Output control part 122 Recording pulse production | generation part 123 Evaluation index derivation circuit 124 Sampling circuit 125 Operation part 126 Memory 150 Optical disk

Claims (8)

A test recording step for performing test recording by changing the output of the recording laser beam in a predetermined pattern in the power calibration area of the optical disc;
An output calculating step of calculating the output of the recording laser beam based on the result of the test recording;
A data recording step for optimally recording data in the data recording area of the optical disc by the output of the recording laser beam calculated in the output calculating step;
In an optical disc recording method comprising:
The data recording step includes
An asymmetry value detection step of sequentially detecting a recording state of the main beam of the recording laser beam by a sub beam and detecting an asymmetry value at the time of recording from the detection result;
An output correction step for correcting the output of the recording laser beam so that the asymmetry value during recording is constant;
Have
The asymmetry value detecting step includes:
A sub-beam RF signal sampling step of sampling a sub-beam RF signal detected by the sub-beam;
An evaluation index sampling step of sampling an evaluation index derived based on the sub-beam RF signal;
A discriminating step for discriminating whether or not the sampled sub-beam RF signal is an extreme value by the evaluation index;
An optical disc recording method comprising:   The optical disc recording method according to claim 1, wherein the evaluation index is a differential signal of a sub-beam RF signal.   The optical disk recording method according to claim 1, wherein the evaluation index is a tangential push-pull signal. The output calculation step includes:
Detecting a recording asymmetry value in the test recording step;
Detecting a recording state in the test recording step by a reproducing laser beam, and detecting an asymmetry value at the time of reproduction from the result;
Calculating the output of the recording laser beam from the relationship between the recording asymmetry value and the reproducing asymmetry value;
The optical disk recording method according to claim 1, comprising:   2. The optical disk recording method according to claim 1, wherein the sampling in the asymmetry value detecting step is performed for an output signal having a data length of 6T or more. A recording means for performing recording by irradiating the optical disc with a recording laser beam;
Output calculating means for calculating the output of the recording laser beam;
Output control means for controlling the output of the pre-recording laser beam based on the result calculated by the output calculation means;
In an optical disc recording apparatus having
The recording means includes
A laser diode that emits a recording laser beam; a light branching unit that branches the recording laser beam from the laser diode into a main beam and a sub beam; a photodetector that detects reflected light of the main beam and the sub beam from the optical disk as an RF signal; , And
The output calculation means includes
Evaluation index deriving means for deriving an evaluation index based on the sub-beam RF signal detected by the photodetector;
Sampling means for discriminating whether or not the sub-beam RF signal sampled by sampling the sub-beam RF signal and the evaluation index is an extrema;
An asymmetry value detecting means for detecting a recording asymmetry value based on the data sampled by the sampling means; an output correcting means for correcting the output of the recording laser beam so that the recording asymmetry value is constant;
An optical disc recording apparatus comprising: 7. The optical disk recording apparatus according to claim 6, wherein the evaluation index deriving unit is a differentiating circuit for differentiating the sub beam RF signal to derive a sub beam differential signal. 7. The optical disk recording apparatus according to claim 6, wherein the evaluation index deriving unit is a push-pull signal circuit that derives a tangential push-pull signal of the sub-beam RF signal.