JP2005243136A - Recording control method of optical disk recording or reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording control method of an optical disk recording or reproducing apparatus which can record a signal on a disk by an optical pickup. <P>SOLUTION: After an offset adjustment signal is recorded in a test writing area established in an inner periphery side of the disk while changing a tilt angle, the operation for reproducing the offset adjustment signal is performed, and an optimum tilt angle T1 is found from changes of recording characteristics determined from the reproducing signal. Then, after the offset adjustment signal is recorded in the test writing area established in a periphery side of the disk while changing the tilt angle, the operation for reproducing the offset conditioning signal is performed and an optimum tilt angle T2 is found from changes of recording characteristics determined from the reproducing signal. When a difference of angle between the tilt angles T1 and T2 is greater than a prescribed value, the change operation of recording rate to the high-speed side is determined to be improper. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recording control method for an optical disc recording / reproducing apparatus configured to record a signal on a disc by laser light emitted from an optical pickup and to perform reproduction operation of the signal recorded on the disc by laser light. .

  An optical disk playback device that performs an operation of reading a signal recorded on a disk using an optical pickup is widely used. In addition to the playback function, a signal is recorded on the disk by a laser beam emitted from the optical pickup. An optical disc recording / reproducing apparatus configured so as to be capable of recording is commercially available.

  The recording disk is provided with a groove called a pregroove, and is configured such that time information, that is, address data, can be obtained by demodulating a wobble signal obtained from the pregroove. The optical disk recording / reproducing apparatus is configured to generate address data based on address data obtained from the disk, and record the signal on the disk by performing an encoding process for adding the address data to the recording signal. .

  The optical disk recording / reproducing apparatus is configured to perform a focus control operation and a tracking control operation because it is necessary to accurately irradiate the laser beam emitted from the optical pickup onto the signal track on the disk surface. Such focus control operation is performed by supplying a driving current to a focusing coil that displaces the objective lens in a direction perpendicular to the disk surface, and the tracking control operation is performed by a tracking coil that displaces the objective lens in the radial direction of the disk. This is done by supplying a drive current to.

  Recently, the recording density has been increased because it is required to record a large number of signals on the disk, and in order to increase the density, laser light is irradiated onto the disk surface in an optimum state. There is a need to. In order to perform such an operation, an optical pickup configured to be able to perform an operation of correcting a relative angular deviation between the disc and the objective lens, that is, a tilt adjustment operation has been developed (for example, Patent Documents). 1).

  In addition, when recording a signal on a disk in an optical disk recording / reproducing apparatus, it is necessary to set the laser light output level to an optimum level for the recording characteristics of the disk. There is a technique in which a test signal is recorded in a writing area while changing the level of the laser output, and the laser output is adjusted and set by reproducing the recorded signal (see, for example, Patent Document 2).

  The recording operation on the disc in the optical disc recording / reproducing apparatus is performed with the disc rotated at a constant linear velocity. When the disc is rotated at a constant linear velocity, the inner circumference side of the disc In this case, the rotational angular velocity of the disk is higher than that on the outer peripheral side. Therefore, it is difficult to rotate the disk from the inner periphery side to the outer periphery side at the same constant high linear velocity.

As a method for solving such a problem, the linear velocity is changed to a high velocity as the recording position moves from the inner circumference side to the outer circumference side of the disc, that is, when the recording position moves to a position where the recording linear velocity can be increased. A technique called so-called ZONE-CLV has been developed (see, for example, Patent Document 3).
JP 2002-197698 A JP-A-8-45099 JP 2002-358642 A

  When performing a recording operation by a method called ZONE-CLV, an operation is performed to change the recording linear velocity to a high linear velocity when the recording position is moved to the outer peripheral side. The recording operation cannot be performed accurately at a high linear velocity. In such an optical disc recording / reproducing apparatus, when the recording operation cannot be normally performed during the recording operation, the recording operation is performed again by reducing the recording linear velocity. In the case of a write-once disc that can only be performed, there is a problem that the disc is wasted.

  The present invention is intended to provide a recording control method for an optical disc recording / reproducing apparatus capable of solving such a problem.

  The present invention records the offset adjustment signal while changing the tilt angle in the test writing area provided on the inner periphery side of the disc, performs the reproduction operation of the offset adjustment signal, and determines the recording determined from the reproduction signal. The optimum tilt angle T1 is obtained from the change in characteristics, and then the offset adjustment signal is recorded while changing the tilt angle in the test writing area provided on the outer peripheral side of the disc, and then the offset adjustment signal is reproduced. The optimum tilt angle T2 is obtained from the change in the recording characteristics determined from the reproduction signal, and when the angle difference between the tilt angles T1 and T2 is larger than a predetermined value, it is determined that the operation for changing the recording speed to the high speed side is impossible. It is configured as follows.

  The present invention uses an optical pickup provided with a tilt adjustment coil for adjusting the tilt of an objective lens and can change the recording speed to a high speed when the recording position is moved from the inner peripheral position to the outer peripheral position of the disk. A control method for a recording / reproducing apparatus, which records an offset adjustment signal while changing the tilt angle in a test writing area provided on the inner circumference side of the disc, and then performs a reproduction operation of the offset adjustment signal to reproduce the reproduction signal. The optimum tilt angle T1 is obtained from the change in the recording characteristics determined from the above, and then the offset adjustment signal is recorded while changing the tilt angle in the test writing area provided on the outer peripheral side of the disc. The optimum tilt angle T2 is obtained from the change in the recording characteristics determined from the reproduction signal, and the tilt angle T If and when the angle difference of T2 is greater than the predetermined value. Thus determines improper operation of changing to the high-speed side of the recording speed, it is possible to perform the recording operation accurately.

  Further, according to the present invention, since the laser output adjustment operation is performed after the tilt angle setting operation, the laser output setting operation that matches the recording characteristics of the disc can be performed.

In the present invention, it is possible to detect the tilt of the disc by using the test writing areas provided on the inner and outer peripheral sides of the disc, and to change the recording speed based on the detected tilt. Determine whether.

  FIG. 1 is a flowchart for explaining a recording control method of the present invention, FIG. 2 is a circuit diagram showing an embodiment of an optical disk recording / reproducing apparatus according to the present invention, and FIGS. 3, 4 and 5 show operations of the present invention. It is a signal waveform diagram for explaining.

  In FIG. 2, reference numeral 1 denotes a disk that is rotationally driven by a spindle motor (not shown). On the inner and outer peripheral sides, a test writing that sets the laser output in accordance with the recording characteristics of the disk when performing a recording operation. An area is provided. In addition, the disc 1 is configured such that position information data is recorded in a groove called a pregroove, and a signal recording / reproducing operation is performed based on a wobble signal obtained from the groove.

  Reference numeral 2 denotes a laser diode 3 that emits laser light emitted to the disk 1 and a monitor diode (not shown) that monitors the level of laser light emitted from the laser diode 3. The optical pickup 4 includes a photodetector 4 that receives laser light reflected from the signal surface, and is configured to be moved in the radial direction of the disk by a pickup feed motor (not shown).

  The optical pickup 2 includes a focusing coil 5 that displaces an objective lens (not shown) in a direction perpendicular to the signal surface of the disk 1, a tracking coil 6 that displaces the objective lens in the radial direction of the disk 1, and A tilt adjustment coil 7 for adjusting the angle of the objective lens with respect to the signal surface of the disk 1 is incorporated.

  Reference numeral 8 denotes an RF signal amplifier circuit that receives a signal obtained from the photodetector 4 incorporated in the optical pickup 2 and amplifies the signal. The RF signal amplification circuit 8 shapes the RF signal and binarizes the signal. It is configured to output. Reference numeral 9 denotes a focusing control operation for focusing the laser beam on the signal surface of the disk 1 on the basis of a focus error signal and a tracking error signal generated from the signal obtained from the photodetector 4, and causing the laser beam to follow the signal track. A pickup control circuit that performs a tracking control operation, and is configured to output a focusing control signal based on a focus error signal and a tracking control signal based on a tracking error signal.

  Reference numeral 10 denotes a focusing coil driving circuit to which a focusing control signal output from the pickup control circuit 9 is input, and is configured to supply a driving signal to the focusing coil 5 incorporated in the optical pickup 2. . Reference numeral 11 denotes a tracking coil driving circuit to which a tracking control signal output from the pickup control circuit 9 is input, and is configured to supply a driving signal to the tracking coil 6 incorporated in the optical pickup 2. .

  Reference numeral 12 denotes a digital signal processing circuit that receives the binarized signal output from the RF signal amplifying circuit 8 and performs a processing operation on the signal, and is configured to perform a demodulation processing operation on various signals. Reference numeral 13 denotes a signal reproducing circuit to which the signal demodulated by the digital signal processing circuit 12 is input, and 14 denotes a system control circuit for controlling each operation of the optical disk recording / reproducing apparatus.

Reference numeral 15 denotes a β value detection circuit that detects the β value from the signal output from the RF signal amplifier circuit 8 and outputs the detected β value to the system control circuit 14. Here, such a β value will be described. FIG. 3 is a waveform diagram of a signal reproduced from the signal recorded on the disk 1, and A1 and A2 are a positive peak level and a negative peak level of the high-frequency signal.

  Under such conditions, the β value is expressed as β = (A1 + A2) / (A1−A2). When this β value becomes a value set based on the recording characteristics of the disc, the laser output suitable for the recording operation is obtained. Value. On the other hand, the relationship between the tilt of the objective lens with respect to the signal surface of the disk 1, that is, the tilt angle and the β value has a characteristic that the β value increases as the tilt adjustment becomes better.

  Such characteristics will be described. In FIG. 3, P indicates a pit formed by irradiating the disk 1 with laser light, and indicates the relationship between the waveform of the reproduction signal and the pit. FIG. 4 shows a state in which the tilt adjustment is better than the state shown in FIG. 3, and the shape of the pit P formed when recording is performed with the same laser output, the laser beam is more efficient. Therefore, it is formed large. As apparent from the reproduction waveform diagram shown in FIG. 4, when the shape of the pit P is increased, the positive peak level of the high-frequency signal is increased and the negative peak level is decreased. As described above, when the tilt angle adjustment is good, the values of A1 and A2 change, and as a result, the β value increases.

  Reference numeral 16 denotes a tilt control circuit for controlling the operation by the system control circuit 14 and performing a tilt control operation using a drive signal output from the focusing coil drive circuit 10. Reference numeral 17 denotes an operation controlled by the system control circuit 14. The memory circuit is configured to store data obtained from the tilt control circuit 16, that is, tilt angle data.

  Reference numeral 18 denotes an amplifying circuit for amplifying the signal output from the tilt control circuit 16, reference numeral 19 denotes a capacitor for cutting a DC signal out of the driving signal output from the focusing coil driving circuit 10, and reference numeral 20 passes through the capacitor 19. The amplifier circuit receives an alternating current signal and amplifies the signal. An adder circuit 21 adds the DC signal amplified by the amplifier circuit 18 and the AC signal amplified by the amplifier circuit 20. Reference numeral 22 denotes a tilt coil drive circuit to which the signal added by the adder circuit 21 is input so that a tilt adjustment drive signal is supplied to the tilt adjustment coil 7 incorporated in the optical pickup 2. It is configured.

  Reference numeral 23 denotes a laser driving circuit for supplying a driving signal to the laser diode 3 incorporated in the optical pickup 2, and reference numeral 24 encodes a recording signal inputted through the system control circuit 14 into a signal for recording on the disk 1. The signal recording circuit supplied to the laser drive circuit 23 is configured to output an offset adjustment signal during the tilt angle detection operation.

  Further, the disk 1 is rotationally driven and controlled so that the linear velocity is constant by a spindle motor. On the inner peripheral side of the disk 1, the disk 1 is rotationally driven at a constant linear velocity, for example, four times the specified linear velocity, As it moves to the outer peripheral side, it is configured to be driven to rotate at a constant linear velocity of 8 times and further at a constant linear velocity of 12 times. Each time the recording speed is changed, the laser output level and the signal processing speed of the digital signal processing circuit 12 and the like are changed corresponding to the recording speed.

As described above, the optical disk recording / reproducing apparatus according to the present invention is configured. Next, the operation will be described. In a state in which a normal recording operation and reproduction operation are performed, a focus error signal and a tracking error signal are generated from a signal obtained from the photodetector 4 incorporated in the optical pickup 2, and based on the error signal A control operation for performing the focusing control operation and the tracking control operation is performed by the pickup control circuit 9.

  When a control operation for performing each operation by the pickup control circuit 9 is performed, a control signal is output from the pickup control circuit 9 to the focusing coil drive circuit 10 and the tracking coil drive circuit 11. As a result, a driving signal is supplied from the focusing coil driving circuit 10 and the tracking coil driving circuit 11 to the focusing coil 5 and the tracking coil 6. As a result of such an operation, a focusing control operation for focusing the laser light emitted from the optical pickup 2 on the signal surface on the disk 1 and a tracking control operation for following the signal track can be performed.

  As described above, the focusing control operation and the tracking control operation by the pickup control circuit 9 are performed. Next, the tilt control operation will be described. In order to perform the tilt control operation, first, an operation for setting an offset value used for correcting a shift in the angle between the signal surface of the disk 1 and the objective lens of the optical pickup 2 is performed. The operation for setting the offset value is performed by causing the system control circuit 14 to output a signal for setting the offset value to the tilt control circuit 16.

  In such an operation, in a state where the normal tilt control operation is not performed, the tilt angle from the tilt coil drive circuit 22 to the tilt adjustment coil 7 is stepped by one step by a control signal output from the tilt control circuit 16. This is done by outputting a signal for changing.

  When such a control signal is output from the tilt control circuit 16, a drive signal for changing the tilt of the objective lens in one direction in one direction is supplied from the tilt coil drive circuit 22 to the tilt adjustment coil 7. Is done. As a result, the objective lens is tilted by one step in the direction of tilt adjustment by the drive operation of the tilt adjusting coil 7.

  During the offset detection operation, an operation of changing the tilt of the objective lens one step at a time based on the control signal output from the tilt control circuit 16 is performed. This operation is performed on the inner peripheral side and the outer peripheral side of the disc 1. This is performed while recording an offset adjustment signal in the provided test writing area. That is, the signal recording circuit 24 outputs an offset adjustment signal to the laser driving circuit 23, and the operation of recording the signal in the trial writing area of the disk 1 by the laser beam output from the laser diode 3 is performed. When such a recording operation is performed, the relationship between the recording position and the level of the signal output from the tilt control circuit 16 is stored in the memory circuit 17.

  When the operation of changing the angle of the objective lens based on the signal output from the tilt control circuit 16 is completed, the reproduction operation of the offset adjustment signal recorded on the disc 1 is performed. In such a signal reproduction operation, the optical pickup 2 is moved to the position where the offset adjustment signal recording operation is started and the drive signal is not supplied to the tilt adjustment coil 7, that is, the objective lens is in a neutral position. This is done in

  When the reproduction operation of the offset adjustment signal recorded while changing the angle of the objective lens with respect to the disk 1, that is, the tilt angle, the level of the RF signal reflected from the disk 1 changes. The offset adjustment signal recorded in the test writing area provided on the disk 1 is amplified by the RF signal amplification circuit 8 and then input to the β value detection circuit 15.

RF as the tilt of the objective lens relative to the signal surface of the disc 1 is adjusted in the correct direction.
The A1 value obtained from the signal increases and the A2 value decreases. Therefore, when the recorded signal is reproduced while the tilt angle is changed stepwise, the β value becomes smaller after the maximum value.

  As described above, when the offset adjustment signal is recorded while the angle of the objective lens is changed stepwise from the direction in which the tilt adjustment is performed by the drive operation of the tilt adjustment coil 7, the β value obtained from the RF signal as the reproduction signal is obtained. Therefore, the value of the control signal output from the tilt control circuit 16 when the drive voltage at the position where the offset adjustment signal with the largest β value is recorded is supplied to the tilt adjustment coil 7 is offset. An operation of storing the value in the memory circuit 17 as a value is performed.

  The above-described operation for obtaining the offset value is performed in a test writing area provided on the inner circumference side of the disc 1. When such operation is completed, the optical pickup 2 is then provided on the outer circumference side of the disc 1. The offset value is set on the outer peripheral side by moving to the trial writing area. Since such an operation can be performed in the same manner as the above-described operation, description thereof is omitted.

  As described above, the offset value setting operation at the inner and outer peripheral positions of the disk 1 is performed. Next, the tilt adjustment operation will be described.

  When the optical disk recording / reproducing apparatus is in a recording state, when the relationship between the optical pickup 2 and the disk 1 is in a state where tilt adjustment is required, a drive signal for changing the angle of the objective lens to the tilt adjustment coil 7. However, the tilt adjustment signal for changing the angle is performed using a drive signal supplied to the focusing coil 5.

  The drive signal supplied from the focusing coil drive circuit 10 to the focusing coil 5 is a signal in which an AC signal is superimposed on a DC voltage. That is, the DC voltage is a signal for setting the position of the objective lens to the operating position, and the AC signal is a signal for displacing the objective lens by following the fast movement of the disk 1. The AC signal described above is a signal for displacing the objective lens to the operating position in accordance with the positional relationship between the signal surface of the disk 1 and the optical pickup 2, and tilt adjustment is performed by utilizing the level change of the drive signal. Can be done.

  A change component of the drive signal output from the focusing coil drive circuit 10 to the focusing coil 5 is extracted as a tilt adjustment signal, and the extracted signal is calculated from the offset value stored in the memory circuit 16. A signal obtained by adding an offset value corresponding to the recording position is supplied to the tilt coil drive circuit 22 as a signal for tilt control. The offset value corresponding to the recording position is the offset value stored in the memory circuit 17, that is, the difference between the offset value on the inner circumference side and the offset value on the outer circumference side, and the distance between the inner circumference side and the outer circumference side of the disk 1. Can be calculated based on this.

  As a result of such an operation, a tilt adjustment drive signal is supplied from the tilt coil drive circuit 22 to the tilt adjustment coil 7, so that the angle of the optical pickup 2 with respect to the disc 1 is optimized. Operation, that is, tilt adjustment operation is performed.

  As described above, each adjustment operation in the present embodiment is performed. Next, a recording control method that is the gist of the present invention will be described with reference to the flowchart shown in FIG.

  When the disc 1 is mounted on the disc mounting portion provided in the optical disc recording / reproducing apparatus for performing the recording operation, first, the optical pickup 2 is moved to the test writing area provided on the inner periphery side of the disc 1 ( Step A).

  When the optical pickup 2 moves to the test writing area provided on the inner circumference side of the disc 1, the offset adjustment signal is recorded while the tilt angle is changed stepwise, and the reproduction characteristics of the recorded offset adjustment signal are recorded. To determine the optimum tilt angle T1 (step B). Such a tilt angle T1 can be performed in the same manner as the operation for obtaining the offset value described above. That is, the offset value and the angle of the objective lens corresponding to the offset value are stored in the memory circuit 17 as table data, and the angle corresponding to the optimum offset value obtained by the offset value setting operation described above is set on the inner circumference side. Is set and stored as the tilt angle T1 (step C).

  When the storage operation of the tilt angle T1 obtained in the test writing area provided on the inner peripheral side in the memory circuit 17 is completed, the optical pickup 2 is moved to the test writing area on the outer peripheral side of the disk 1 ( Step D). Such a movement operation to the test writing area can be performed by detecting address data obtained from the pregroove, but since such an operation can be performed by a well-known search operation, the description thereof is omitted.

  When the optical pickup 2 moves to the test writing area provided on the outer peripheral side of the disc 1, the offset adjustment signal is recorded while the tilt angle is changed stepwise, and from the reproduction characteristics of the recorded offset adjustment signal. An optimum tilt angle T2 is obtained (step E). Such a tilt angle T2 can be obtained by the same operation as the tilt angle T1 described above.

  When the tilt angles T1 and T2 are obtained by the above-described operation, the difference between T1 and T2 is then obtained (step F). When the difference between the tilt angles T1 and T2, that is, the absolute value | T1-T2 | is obtained by such an operation, it is determined whether or not the magnitude is larger than the set value T0 (step G). The set value T0 is an angle serving as a reference for determining whether or not the recording linear velocity on the outer peripheral side can be changed due to the influence of the warp of the disk 1. That is, if the absolute value | T1-T2 | is larger than the set value T0, it can be determined that the warp of the disk 1 is large.

  If it is determined in step G that the absolute value | T1-T2 | is smaller than T0, it is determined that the recording speed can be changed to the high speed side because the warp of the disk 1 is small (step H). Conversely, if it is determined in step G that the absolute value | T1-T2 | is greater than T0, it is determined that the recording speed cannot be changed to the high speed side because the warpage of the disk 1 is large (step I). ).

  By performing such a determination operation, whether or not the recording speed changing operation is performed when the recording position is moved to a position where the recording speed changing operation can be performed can be set before starting the recording operation. . Accordingly, since the speed changing operation at which the recording operation cannot be normally performed is not performed, the recording operation can be normally performed from the inner circumference side to the outer circumference side of the disk 1.

  As described above, the tilt angle of the optical pickup 2 can be set to an optimum state in the test writing areas provided on the inner peripheral side and the outer peripheral side. If the setting operation of the laser output suitable for performing the recording operation later is performed, the setting operation of the laser output suitable for the recording operation can be performed accurately and efficiently. Such a laser output setting operation can be performed by performing a test signal recording operation while changing the laser output, and recognizing the recording characteristics of the recorded test signal. Can be performed by using the β value detection circuit 15 described above.

  In the test writing areas provided on the inner and outer peripheral sides, a test signal is recorded while changing the laser output, the recorded test signal is reproduced, and β detected by the β value detecting circuit 15 The laser output recording the test signal whose value is suitable for the characteristics of the disc 1 is set as the laser output suitable for the recording operation of the disc.

  As described above, each operation of this embodiment is performed, but the offset adjustment signal is reproduced, and the change in the recording characteristic corresponding to the tilt angle is detected by the β value of the reproduced signal. The signal level can also be used. That is, the better the angle of the objective lens with respect to the signal surface of the disc 1, the larger the shape of the pits recorded on the disc, and the higher the RF signal level of the recorded signal.

  FIG. 5 shows the waveform of the RF signal obtained from the RF signal amplifying circuit 8. The solid line A shows the peak level and the solid line B shows the bottom level. Therefore, each detection circuit for detecting the peak level and the bottom level of the RF signal is provided instead of the β value detection circuit 15, and the change in the recording characteristic corresponding to the tilt angle can be detected by detecting the change in each level. It will be possible.

  Since the peak level increases as the relationship between the objective lens and the signal surface of the disk 1 becomes better, and the bottom level decreases, the peak level is maximized or the bottom level is minimized. It can be recognized that the tilt angle corresponding to this point is the optimum tilt angle.

3 is a flowchart for explaining a recording control method of the present invention. It is a circuit diagram which shows one Example of the optical disk recording / reproducing apparatus based on this invention. It is a signal waveform diagram for demonstrating operation | movement of this invention. It is a signal waveform diagram for demonstrating operation | movement of this invention. It is a signal waveform diagram for demonstrating operation | movement of this invention.

Explanation of symbols

1 disc
2 Optical pickup
3 Laser diode
4 photodetectors
5 Focusing coil
7 Tilt adjustment coil
8 RF signal amplifier circuit
DESCRIPTION OF SYMBOLS 9 Pickup control circuit 10 Focusing coil drive circuit 12 Digital signal processing circuit 14 System control circuit 15 β value detection circuit 16 Tilt control circuit 17 Memory circuit 22 Tilt coil drive circuit 23 Laser drive circuit 24 Signal recording circuit

Claims (6)

An optical disk recording / reproducing apparatus using an optical pickup having a tilt adjusting coil for adjusting the tilt of an objective lens and capable of changing a recording speed to a high speed when the recording position is moved from the inner peripheral position of the disk to the outer peripheral position. This is a control method. After recording the offset adjustment signal while changing the tilt angle in the test writing area provided on the inner circumference side of the disc, the reproduction operation of the offset adjustment signal is performed, and the determination is made from the reproduction signal. The optimum tilt angle T1 is obtained from the change in the recording characteristics, and after the offset adjustment signal is recorded while changing the tilt angle in the test writing area provided on the outer periphery side of the disc, the reproduction operation of the offset adjustment signal is performed. The optimum tilt angle T2 is obtained from the change in recording characteristics determined from the reproduction signal, and the tilt angles T1 and T2 are calculated. When time difference is greater than a predetermined value, recording control method of the optical disc recording and reproducing apparatus is characterized in that so as to determine improper operation of changing to the high-speed side of the recording speed. 2. The recording control method according to claim 1, wherein the laser output adjustment operation is performed after the tilt angle setting operation. 2. The recording control method according to claim 1, wherein a change in recording characteristics is detected by a β value obtained from an RF signal. 2. The recording control method according to claim 1, wherein a change in recording characteristics is detected by a level of an RF signal. 5. A recording control method according to claim 4, wherein a change in recording characteristics is detected by a peak level of the RF signal. 5. The recording control method according to claim 4, wherein a change in recording characteristics is detected by a bottom level of the RF signal.

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