JP2006155778A - Recording control method for optical disk recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording control method for an optical disk recording/reproducing device, capable of recording a signal in an optical disk by a laser beam emitted from a laser diode incorporated in an optical pickup. <P>SOLUTION: Every time changing the value of a tilt coil driving signal supplied to a tilt adjusting coil 18, by comparing the levels of RF signals obtained by reproducing the pits of different lengths recorded in an optical disk D, the spot diameter of a signal track direction is detected. By detecting the level of a tracking error signal in the inoperative state of a tracking servo, the spot diameter of a direction perpendicular to the signal track is detected, and the value of a tilt driving signal is set so that the ratio of the spot diameters of the track direction and the perpendicular direction is within a predetermined value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording control method for an optical disk recording / reproducing apparatus that performs a signal recording operation on an optical disk with laser light emitted from a laser diode incorporated in an optical pickup.

  2. Description of the Related Art An optical disk recording / reproducing apparatus that performs a signal recording operation on an optical disk with laser light emitted from a laser diode has become widespread. As an optical disk recording / reproducing apparatus, an apparatus using an optical disk called CD and an apparatus using an optical disk called DVD are generally used.

  The signal recording operation on the optical disk is performed by forming pits on a signal track provided on the optical disk with laser light. The length of such pits is 3T, 4T. In a DVD disc, 3T, 4T... 14T are specified.

  The recording operation on the optical disk is performed by supplying a drive pulse corresponding to the recording signal to the laser diode, that is, a pulse signal as shown in FIG. It is set based on the recording strategy set according to the characteristics.

  Such a recording strategy is set such that the spot shape of the laser light emitted from the optical pickup is constant, and the diameter in the tangential direction of the track, that is, the tangential direction is constant. However, the direction of the laser beam spot is not constant and differs depending on the optical pickup. Therefore, the optimum recording operation cannot be performed only by setting the recording strategy without considering the spot shape.

  In order to improve such a point, a technique for adjusting the spot direction of a laser beam with respect to a track on an optical disc has been developed (see, for example, Patent Document 1).

  In addition, the recording density has been increased to record many signals on the disc. However, in order to perform high-density recording accurately, it is necessary to irradiate the signal surface of the disc in an optimal state. is there. In order to perform such an operation, not only the focus control operation for focusing the laser beam on the signal surface and the tracking control operation for following the signal track are accurately performed, but also the relative relationship between the signal surface of the disc and the objective lens. It is necessary to perform an operation for correcting the angle deviation, that is, a tilt control operation. An optical pickup configured to perform such a tilt control operation has been developed (see, for example, Patent Document 2).

  A technique for detecting the inclination of the optical pickup relative to the disk and adjusting the inclination has been developed (see, for example, Patent Document 3).

Further, in an optical disk recording / reproducing apparatus, it is necessary to perform an operation of causing a laser beam emitted from an optical pickup to follow a signal track, and such a control operation is generally performed by a circuit called a tracking servo. There are various tracking control methods for performing such tracking control operation, but based on the phase difference between the signals obtained by adding the signals obtained from the diagonally arranged photodetectors in the quadrant photodetector. A method using a generated tracking error signal, that is, a phase difference detection method is common (see, for example, Patent Document 4).
JP-A-8-63777 JP 2002-197698 A JP 2001-52362 A JP 2001-266373 A

  The technique described in Patent Document 1 requires a precise adjustment at the time of manufacturing the optical pickup, and thus has a problem that the manufacturing cost increases. In addition, even if an optical pickup adjusted in this way is used and incorporated in an optical disc recording / reproducing apparatus, the relationship with the spot shape with respect to the track due to the displacement of the mounting position or the change of the spot shape accompanying the focus control operation. Is difficult to keep constant.

  Thus, since the relationship between the track on the optical disk and the spot shape of the laser beam is not constant, the recording operation set in advance in accordance with the recording characteristics of the optical disk is performed in an optimal state. There is a problem that it cannot be done.

  The present invention intends to provide a recording control method capable of solving such a problem.

  The present invention compares the level of an RF signal obtained by reproducing pits of different lengths recorded on an optical disk every time the value of a tilt coil drive signal supplied to a tilt adjustment coil is changed. The spot diameter in the direction perpendicular to the signal track is detected by detecting the spot diameter in the track direction and detecting the level of the tracking error signal when the tracking servo is in the non-operating state. The value of the tilt drive signal is set so that the ratio of the spot diameters in the perpendicular direction is within a predetermined value.

  In the present invention, the level comparison operation is performed by an RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disc.

  The present invention is configured to detect the spot diameter based on the level difference between the maximum level and the minimum level of the tracking error signal.

  Further, the present invention provides a recording strategy memory circuit in which a plurality of recording strategies corresponding to the ratio of the spot diameter in the track direction and the spot diameter in the perpendicular direction are provided, and the recording strategy stored in the recording strategy memory circuit is converted to the spot diameter. The recording strategy is set by selecting based on the ratio.

The present invention compares the level of an RF signal obtained by reproducing pits of different lengths recorded on an optical disk every time the value of a tilt coil drive signal supplied to a tilt adjustment coil is changed. The spot diameter in the direction perpendicular to the signal track is detected by detecting the spot diameter in the track direction and detecting the level of the tracking error signal when the tracking servo is in the non-operating state. Since the value of the tilt drive signal is set so that the spot diameter ratio in the perpendicular direction is within a predetermined value, the spot shape of the laser beam can be made a shape suitable for performing an accurate recording operation. In the present invention, the level comparison operation is obtained by reproducing the shortest pit and the longest pit recorded on the optical disc. In other words, since the RF signal level obtained from the pit having the largest level difference to be compared is compared, the spot shape detection operation can be performed accurately.

  In the present invention, since the spot diameter is detected based on the level difference between the maximum level and the minimum level of the tracking error signal, the level detection operation can be easily performed.

  Further, the present invention provides a recording strategy memory circuit in which a plurality of recording strategies corresponding to the ratio of the spot diameter in the track direction and the spot diameter in the perpendicular direction are provided, and the recording strategy stored in the recording strategy memory circuit is converted to the spot diameter. Since the recording strategy is set by selecting on the basis of the ratio, it is possible to generate a laser drive signal suitable for the recording operation, and as a result, the signal recording operation to the disc can be performed accurately. .

  The present invention is implemented in an optical disc recording / reproducing apparatus configured to perform a recording operation using an optical pickup in which a tilt adjusting coil for adjusting the tilt of an objective lens is incorporated.

  FIG. 6 is a circuit diagram for explaining a circuit for generating a tracking error signal according to the present invention, that is, a phase difference detection method. In the figure, reference numeral 1 denotes a four-divided photodetector that receives laser light reflected from the optical disk D, and is composed of four photodetectors A, B, C, and D.

  Reference numeral 2 denotes a first adder circuit that adds signals obtained from the photodetectors A and C constituting the quadrant photodetector 1. Reference numeral 3 denotes a photodetector B and D that constitutes the quadrant photodetector 1. This is a second adder circuit for adding the received signals. Reference numeral 4 denotes a first equalizer circuit for correcting the frequency of the first addition signal output from the first addition circuit 2, and reference numeral 5 denotes a second equalizer for correcting the frequency of the second addition signal output from the second addition circuit 3. It is a circuit.

  Reference numeral 6 denotes a first comparator circuit to which the first addition signal whose frequency is corrected by the first equalizer circuit 4 is input. When the input signal exceeds a predetermined level, a first pulse that becomes H (high) during that time. It is configured to output a signal. Reference numeral 7 denotes a second comparator circuit to which the second addition signal whose frequency has been corrected by the second equalizer circuit 5 is input, and outputs a second pulse signal that attains an H level when the input signal exceeds a predetermined level. Is configured to do.

  Reference numeral 8 denotes a phase difference detection circuit that receives a first pulse signal output from the first comparator circuit 6 and a second pulse signal output from the second comparator circuit 7 and detects a phase difference between the two pulse signals. When the phase of the first pulse signal is ahead of the phase of the second pulse signal, the first output terminal 8A for outputting the first detection pulse signal having a width corresponding to the phase difference and the phase of the second pulse signal are A second output terminal 8B is provided for outputting a second detection pulse signal having a width corresponding to the phase difference when the phase is advanced from the phase of the first pulse signal.

Reference numeral 9 denotes a first low-pass filter circuit to which a signal output from a first output terminal 8A provided in the phase difference detection circuit 8 is input. Reference numeral 10 denotes a second output terminal provided in the phase difference detection circuit 8 A second low-pass filter circuit to which a signal output from 8B is input, 11 is a subtraction circuit to which the output signals of the first low-pass filter circuit 9 and the second low-pass filter circuit 10 are input, and the difference between the input signals The signal is output to the output terminal 11A as a tracking error signal.

  As described above, the phase difference detection type tracking error signal generation circuit is configured. Next, the detection operation will be described with reference to the waveform diagrams shown in FIGS. FIG. 7A shows the waveforms of the first addition signal output from the first equalizer circuit 4 and the second addition signal output from the second equalizer circuit 5, and the solid line indicates the first addition signal and the broken line. Is the second addition signal.

  FIG. 7B shows the waveform of the first pulse signal output from the first comparator circuit 6, and the level of the first addition signal exceeds the comparison reference level VR shown in FIG. The period is shown at the H level. FIG. 7C shows the waveform of the second pulse signal output from the second comparator circuit 7, and the level of the second addition signal exceeds the comparison reference level VR shown in FIG. The period is shown at the H level.

FIG. 7D shows the waveform of the first detection pulse signal output to the first output terminal 8A of the phase difference detection circuit 8, and the phase of the first pulse signal is ahead of the phase of the second pulse signal. The period of time is indicated by H level. FIG. 7E shows the waveform of the second detection pulse signal output to the second output terminal 8B of the phase difference detection circuit 8, and the phase of the second pulse signal is advanced from the phase of the first pulse signal. FIG. 8 is a waveform diagram showing the level change of the tracking error signal output to the output terminal 11A of the subtracting circuit 11, and the deviation of the light beam with respect to the signal track, that is, off. Since the phase difference amount changes according to the track, the level of the tracking error signal changes according to the phase difference.

  The tracking control operation in the optical disk recording / reproducing apparatus according to the present invention is performed by using the tracking error signal obtained by the circuit described above. Next, the optical disk recording / reproducing apparatus according to the present invention shown in FIG. 1 will be described.

  In FIG. 1, reference numeral 12 denotes an optical pickup incorporating a laser diode 13 for irradiating laser light. An objective lens 14 for focusing the laser light emitted from the laser diode 13 on the signal surface of the optical disk D, and the optical disk D Tracking is performed to receive the laser beam reflected from the light and convert it into an electric signal, and to displace the optical detector 15 and the objective lens 14 including the quadrant optical detector 1 shown in FIG. A coil 16, a focusing coil 17 that displaces the objective lens 14 in a direction perpendicular to the signal surface of the optical disk D, and a tilt adjustment coil 18 that adjusts the angle of the objective lens 14 with respect to the disk D are incorporated.

  In such a configuration, the main body of the optical pickup 12 is configured to be displaced in the radial direction of the optical disc D by a pickup feeding motor (not shown). Since such a driving mechanism may use a known mechanism, the description thereof is omitted.

Reference numeral 19 denotes an optical output signal processing circuit to which an electrical signal obtained from the photodetector 15 is input as an optical signal, and generates a tracking error signal for generating a tracking error signal indicating a deviation from the signal track of the laser light as described above. The circuit is built in. The optical output signal processing circuit 19 incorporates a focus error signal generation circuit (not shown) that outputs a focus error signal indicating a focus shift with respect to the recording layer of the laser light.

  The optical output signal processing circuit 19 incorporates a signal reproduction circuit (not shown) that generates a signal obtained by binarizing the reproduction signal of the signal recorded on the optical disc D. The optical output signal processing circuit 19 incorporates an RF signal reproduction circuit (not shown) for outputting an RF signal that is a reproduction signal read from the optical disc D. Since the operation of generating various signals by the optical output signal processing circuit 19 is performed by a known circuit, the description thereof is omitted.

  Reference numeral 20 denotes a tracking servo circuit to which a tracking error signal output from an output terminal 11A of a tracking error signal generation circuit incorporated in the optical output signal processing circuit 19 is input, and a tracking coil based on the input tracking error signal A tracking control operation is performed by supplying a drive signal to the tracking coil 16.

  Reference numeral 21 denotes a focus servo circuit to which a focus error signal generated and output by the optical output signal processing circuit 19 is input, and supplies a focusing coil driving signal based on the input focus error signal to the focusing coil 17. Is configured to perform a focus control operation.

  The focusing coil drive signal supplied from the focus servo circuit 21 to the focusing coil 17 is accompanied by a DC voltage that displaces the objective lens 14 to an operating position that is a position for focusing the recording layer of the optical disk D and surface vibration of the optical disk D. In order to correct the focus shift, it is composed of a high-frequency signal for displacing the objective lens 14 at a high speed. Since such a signal is well known, a description thereof will be omitted.

  A tilt control circuit 22 supplies a tilt drive signal to the tilt adjustment coil 18 based on a tilt adjustment signal obtained from the focus servo circuit 21. When the focus position is displaced according to the inclination between the objective lens 14 and the optical disc D, the focus servo circuit 21 outputs a drive signal for displacing the position of the objective lens 14 in order to correct the displacement. Therefore, if a drive signal is supplied to the tilt adjustment coil 18 based on the drive signal output from the focus servo circuit 21, a tilt control operation for adjusting the tilt of the objective lens 14 with respect to the optical disc D can be performed.

  Reference numeral 23 denotes a digital signal processing circuit that inputs a reproduction signal binarized by a binarization circuit provided in the optical output signal processing circuit 19 and performs digital signal processing. It is configured to demodulate various signals such as synchronization signals, position information data, and recording signals. Reference numeral 24 denotes a system control circuit for controlling each operation of the optical disk recording / reproducing apparatus. By using the synchronization signal generated by the digital signal processing circuit 23, the rotation control operation of the optical disk D by the spindle motor and the reproduction signal and recording signal are controlled. It is configured to control a processing operation and a signal transmission / reception operation with a host device such as a personal computer provided outside. Such a system control circuit 24 is configured by a microcomputer, and is configured to perform various control operations based on program software stored in a flash ROM or the like provided therein.

  Reference numeral 25 denotes an RF signal level detection circuit that receives an RF signal output from the optical output signal processing circuit 19 and detects the level of the signal. The shortest pit recorded on the optical disc D, for example, a 3T signal and It is configured to detect the level of the RF signal obtained from the signal of the longest pit, for example, 14T.

The operation of detecting the RF signal level obtained by reproducing such 3T signal and 14T signal is as follows:
When the 3T signal and the 14T signal are recognized from the signal obtained by the digital signal processing circuit 23, the detection can be performed based on the level detection operation control signal output from the system control circuit 24.

  Reference numeral 26 denotes a first level memory circuit whose operation is controlled by the system control circuit 24, and is configured to store the level L1 of the RF signal corresponding to 3T detected by the RF signal level detection circuit 25. Yes. Reference numeral 27 denotes a second level memory circuit whose operation is controlled by the system control circuit 24. The second level memory circuit 27 is configured to store an RF signal level L2 corresponding to 14T detected by the RF signal level detection circuit 25. Yes.

  The system control circuit 24 is configured to calculate a ratio R1 from L2 / L1 when the RF signal levels L1 and L2 are stored in the first level memory circuit 26 and the second level memory circuit 27, respectively. Yes.

  Reference numeral 28 denotes a signal recording circuit to which a recording signal input from a personal computer or the like and a test signal generated by the system control circuit 24 are input. The recording signal is subjected to encoding processing such as interleaving in accordance with the standard of the optical disc D. Has an effect. Since the encoding process by the signal recording circuit 28 is well known, its description is omitted.

  Reference numeral 29 denotes a laser drive signal generation circuit to which the recording signal encoded by the signal recording circuit 28 is input, and a drive signal suitable for forming 3T, 4T... 14T pits corresponding to the recording signal, That is, it is configured to generate a pulse signal as shown in FIG. A laser drive circuit 30 outputs a signal for driving the laser diode 13 in accordance with the drive signal generated and output from the laser drive signal generation circuit 29.

  Reference numeral 31 denotes a first spot diameter memory circuit which is incorporated in the system control circuit 24 and connected to control the data write operation and data read operation, and is detected by the RF signal level detection circuit 25. The spot diameter S1 in the signal track direction, that is, the radial direction is stored as table data in accordance with the value of the ratio R1 calculated based on the RF signal levels L1 and L2 obtained corresponding to the 3T and 14T pits. Yes.

  Reference numeral 32 denotes a tracking error signal level detection circuit for detecting the level of the tracking error signal output from the tracking error signal output terminal 11A provided in the optical output signal processing circuit 19, and a peak which is the maximum level of the tracking error signal. A level between the level and the lowest level, that is, a level indicated by EV in FIG. 8 is detected, and the detected level is binarized and output to the system control circuit 24. Yes.

  Reference numeral 33 denotes a defocus value setting circuit for setting a defocus value which is a control voltage supplied from the focus servo circuit 21 to the focusing coil 17, and the operation is controlled by the system control circuit 24. Reference numeral 34 denotes a second spot diameter memory circuit incorporated in the system control circuit 22 and connected to control the data writing and reading operations. The defocus value, error signal level EV, and spot Data indicating the relationship with the diameter is stored as table data.

A laser drive signal control circuit 35 whose operation is controlled by the system control circuit 24 is configured to control a drive signal generation operation by the laser drive signal generation circuit 29. Reference numeral 36 denotes a recording strategy memory circuit whose operation is controlled by the system control circuit 24. The spot diameter S1 obtained by the ratio R1, the spot diameter S2 obtained by the level EV of the tracking error signal, and the ratio of S1 and S2. Strategy data set based on R2 (S2 / S1) is stored as table data.

  The recording drive signal generation control operation for the laser drive signal generation circuit 29 by the laser drive signal control circuit 35 is performed based on the table data obtained from the recording strategy memory circuit 36. That is, the drive signal supplied from the laser drive signal generation circuit 29 to the laser drive circuit 30 is a pulse signal as shown in FIG. 3, and when a 3T pit is formed, a signal of only the first pulse P1 and 4T In the case of forming the pit, the signal composed of the leading pulses P1 and P2 is outputted to the laser driving circuit 30. In the case of forming the 5T pit, the driving signal composed of the leading pulses P1, P2 and P3 is outputted to the laser driving circuit 30. Thus, the width of the pulses P1, P2, and P3 and the interval between the pulses are changed and set based on the table data obtained from the recording strategy memory circuit 36.

  In such a configuration, the operation / non-operation of the tracking servo circuit 20 is configured to be selectively controlled by the system control circuit 24, and the tracking error signal level EV detection operation by the tracking error signal level detection circuit 32 is performed by the tracking servo. The circuit 20 is configured to be in a non-operating state. The signal for performing the level detection operation of the tracking error signal uses, for example, a test signal recorded in a test writing area provided for performing a laser output setting operation on the inner circumference side of the optical disc D. It is configured.

  In addition, a groove called a pregroove is formed on the recording optical disk D, and the optical disk D is driven to rotate based on a synchronization signal or position information data obtained by demodulating the wobble signal obtained from the pregroove. And the displacement operation of the optical pickup 12 is controlled.

  The RF signal level detection operation by the RF signal level detection circuit 25 is performed by, for example, applying 3T and 14T test signals to the test writing area provided for performing the laser output setting operation on the inner circumference side of the optical disc D, for example. It is configured to record and reproduce the recorded signal.

  The drive voltage value supplied from the tilt control circuit 22 to the tilt adjustment coil 18 can be changed stepwise by the control operation of the system control circuit 24.

  As described above, the optical disk recording / reproducing apparatus according to the present invention is configured. Next, the operation will be described. When the reproduction operation of the signal recorded on the optical disc D is performed, the rotation control operation of the spindle motor is performed, and the optical disc D is rotationally driven at a predetermined linear velocity. Such a control operation for keeping the linear velocity constant includes a synchronization signal read from the optical disc D and a synchronization signal generated from a synchronization signal generation circuit (not shown) connected to be controlled by the system control circuit 24. Are synchronized with each other, but since such operations are well known, the description thereof will be omitted.

  The drive signal supplied to the laser diode 13 for reproducing the signal recorded on the optical disc D is set so as to obtain a laser output necessary for performing the reproduction operation. The laser light emitted from the laser diode 13 is collected by the objective lens 14 and focused on the signal surface of the optical disk D. Such focusing operation is performed by a servo operation by the focus servo circuit 21. Is called.

  The focus control operation by the focus servo circuit 21 is performed using a signal obtained from the photodetector 15 that is irradiated with laser light reflected from the signal surface of the optical disc D. A signal obtained from the photodetector 15 is input to the optical output signal processing circuit 19, a focus error signal is generated based on the signal, and the focus error signal is input to the focus servo circuit 21. When such a focus error signal is input to the focus servo circuit 21, a drive signal for displacing the objective lens 14 in a direction to reduce the level of the focus error signal is supplied from the focus servo circuit 21 to the focusing coil 17. . As a result of supplying such a drive signal to the focusing coil 17, an operation of focusing the laser beam on the signal surface of the optical disc D, that is, a focus control operation can be performed.

  Although the focus control operation is performed as described above, the tracking control operation can be performed in the same manner. That is, when the spot of the laser light emitted from the laser diode 13 deviates from the signal track on the optical disk D, a tracking error signal of a level corresponding to the magnitude of the deviation is output to the tracking error signal output terminal of the optical output signal processing circuit 19 11A.

  When such a tracking error signal is input to the tracking servo circuit 20, a driving signal for displacing the objective lens 14 is supplied from the tracking servo circuit 20 to the tracking coil 16 in a direction to reduce the level of the tracking error signal. . As a result of supplying such a drive signal to the tracking coil 16, an operation of causing the laser beam to follow a signal track provided on the signal surface of the optical disc D, that is, a tracking control operation can be performed.

  As described above, the focus control operation by the focus servo circuit 21 and the tracking control operation by the tracking servo circuit 20 are performed. Next, the tilt control operation will be described. The tilt control operation by the tilt control circuit 22 is performed by supplying a drive signal generated based on the signal obtained from the focus servo circuit 11 as described above. The tilt control operation is performed by the system control circuit 14. This is performed based on the reference drive signal supplied from. That is, the tilt control operation is performed in a state where the tilt of the objective lens 14 with respect to the signal surface of the optical disc D is set to an optimum state by supplying a reference drive signal set by an operation described later to the tilt adjustment coil 18. It is configured.

  As a result of the focus control operation, the tracking control operation, and the tilt control operation described above, a signal recorded on the signal track of the optical disc D can be read. A signal track of the optical disc D is recorded with a plurality of pits having different lengths, and an RF signal corresponding to the length of the pits is generated by the optical output signal processing circuit 19 and binarized. Is output.

  The binarized signal output from the optical output signal processing circuit 19 is input to the digital signal processing circuit 23, and demodulation operation is performed by the digital signal processing circuit 23. The data signal demodulated by the digital signal processing circuit 23 is output to a personal computer or the like via the system control circuit 24.

  As described above, the reproducing operation in this embodiment is performed. Next, the recording operation will be described. The rotation control operation of the optical disc D by the spindle motor during the recording operation, the tracking control operation by the tracking servo circuit 20, the focus control operation by the focus servo circuit 21, and the tilt control operation by the tilt control circuit 22 are performed in the same manner as in the above-described reproduction operation. Is called.

  A recording signal output from the personal computer is input to the signal recording circuit 28 and encoded by the signal recording circuit 28. Since the recording signal encoded by the signal recording circuit 28 is input to the laser drive signal generation circuit 29, the laser drive signal generation circuit 29 inserts a pit having a length corresponding to the input recording signal into the optical disc. A drive signal for forming the signal track D is output to the laser drive circuit 30.

  In such a case, the pulse waveform of the drive signal supplied to the laser drive circuit 30 is generated based on the strategy data selected from the recording strategy memory circuit 36. When the pulse waveform drive signal thus generated and controlled is supplied to the laser drive circuit 30, a drive signal corresponding to the pulse waveform is supplied from the laser drive circuit 30 to the laser diode 13.

  When such a drive signal is supplied to the laser diode 13, a laser beam corresponding to the pulse is emitted from the laser diode 13, and a pit is formed on the signal track of the optical disc D. The length of the pit formed by such an operation is 3T, 4T... 14T corresponding to the signal standard of the optical disc D.

  As described above, the recording operation in this embodiment is performed. Next, the gist of the present invention will be described.

  FIG. 2 shows the relationship between the pits P formed on the signal track of the optical disc D and the laser light spot S. FIG. In FIG. 2A, when the shape of the spot S is an ellipse and the major axis direction is perpendicular to the track direction, FIG. 2B shows the shape of the spot S being an ellipse and the track direction. When the major axis direction is inclined by about 45 degrees, FIG. 2C shows a case where the shape of the spot S is an ellipse and the track direction and the major axis direction coincide.

  The spot S of the laser beam that acts to form the pits P on the optical disk D is a portion (effective length) that overlaps the pits P in FIG. 2, and the length direction of the pits P is apparent from each state. That is, the effective length which is the length in the tangential direction is different.

  In addition, when a signal recorded on the optical disc D is read or when a signal is recorded on the optical disc D, an operation of reading a wobble signal from a pregroove formed on the optical disc D is performed. As the spot S when performing such an operation, the length in the direction perpendicular to the signal track, that is, the radial direction of the optical disc D is important.

  In such a configuration, when the inclination of the objective lens 14 with respect to the optical disc D is changed, the shape of the spot S changes. That is, in FIG. 2, the value and ratio of the spot diameter S1 in the tangential direction that is the signal track direction and the spot diameter S2 in the radial direction that is the direction perpendicular to the signal track are changed.

  The present invention improves the wobble signal reproduction characteristics due to the change in recording characteristics due to the difference in effective length due to the difference in the shape of the spot S and the size of the spot S in the radial direction of the disk, that is, in the radial direction. In particular, by changing the value of the tilt coil drive signal for performing the tilt control operation, the spot shape suitable for performing the recording / reproducing operation is set and the recording strategy is changed according to the spot shape. is there.

Next, an operation for detecting the shape of the spot S that causes the effective length to be different in the recording operation will be described. When the test signal recorded when adjusting the laser output is reproduced in the test writing area provided on the optical disc D, the RF signal and the binarized signal are output from the optical output signal processing circuit 19 as described above. The

  The RF signal output from the optical output signal processing circuit 19 is in the state of being input to the RF signal level detection circuit 25, and the RF signal level detection circuit 25 operates to detect the level of the input RF signal. It is in a state to do. In this state, since the binarized signal output from the optical output signal processing circuit 19 is input to the digital signal processing circuit 23, the 3T signal and the 14T signal are input from the input signals. Detection operation can be performed.

  When the 3T signal is detected, a control operation is performed by the system control circuit 24, and an operation of storing the level L1 of the RF signal detected by the RF signal level detection circuit 25 at that time in the first level memory circuit 26 is performed. Is called. Similarly, when the 14T signal is detected, a control operation is performed by the system control circuit 24, and the second level memory circuit 27 stores the level L2 of the RF signal detected by the RF signal level detection circuit 25 at that time. Is done.

  When the storage operation of level L1 in the first level memory circuit 26 and the storage operation of level L2 in the second level memory circuit 27 are performed, the level ratio R1 of the RF signal is set to L2 by the arithmetic processing operation by the system control circuit 24. / L1.

  As for the level of the RF signal output from the optical output signal processing circuit 19, the level L1 obtained from the 3T signal having the shortest pit length is the smallest, and the level L2 obtained from 14T being the longest pit length is the largest. Further, the level of the RF signal changes corresponding to the effective length of the spot S with respect to the pit P. That is, as the effective length becomes shorter, a larger change in reflected light can be obtained, and the level of the RF signal increases.

  On the other hand, the ratio of the effective length of the spot S to the length of the pit P varies depending on the size of the effective length. However, since the pit length is defined by the recording standard of the optical disc D, 3T and 14T The length of is constant. As a result, the level of the RF signal obtained from the 3T and 14T pits changes depending on the effective length of the spot S, and the rate of change also differs.

  When the length of the effective length of the spot S is SA and the value of L1 is LA1 and the value of L2 is LA2, the ratio RA is LA2 / LA1 and the length of the effective length of the spot S is SB. When the value is LB1 and the value of L2 is LB2, the ratio RB is LB2 / LB1. Then, the ratios RA and RB obtained in this way are different with the difference in the effective length of the spot S.

  When the ratio of the RF signal level obtained from 3T and 14T is obtained with the pit length being constant, the effective length of the spot S of the laser beam with respect to the pit can be detected. In addition, since the shape of the laser light spot S in the optical pickup 12 is determined at the time of manufacturing the optical pickup 12, the effective length is detected to detect the spot S in the signal track direction with respect to the laser light signal track. The spot diameter S1 can be obtained from the table data stored in the first spot diameter memory circuit 23.

  As described above, the operation for detecting the spot diameter S1 in the signal track direction of the spot S is performed. Next, the operation for detecting the spot diameter S2 in the direction perpendicular to the signal track of the spot S will be described.

  Such a detection operation is performed by reproducing a test signal recorded at the time of adjusting the laser output in a test writing area provided in the optical disc D. Such a reproduction operation does not operate the tracking servo circuit 20. It is performed in the state made into the state.

  The movement of the optical pickup 12 to the trial writing area can be performed by a known operation called search. That is, the position information recorded on the signal track of the optical disk D is read by repeatedly performing the track jump operation of the optical pickup 12, and the optical pickup 12 is read at the desired track, that is, the position where the test signal is recorded. It can be moved.

  When it is recognized that the optical pickup 12 has moved to a desired position by such an operation, a control operation for setting the tracking servo circuit 20 to an inoperative state while the focus control operation by the focus servo circuit 21 is performed. Is performed by the system control circuit 24.

  In such a state, the test signal recorded in the test writing area of the optical disc D is read out, but the test signal cannot be read out normally because the tracking servo circuit 20 is stationary. In such a state, the difference between the spot S of the laser beam and the signal track becomes large, so that the level of the tracking error signal output to the tracking error signal output terminal 11A greatly varies.

  In the present invention, the tracking error signal level detection circuit 32 detects the level EV of the tracking error signal output from the tracking error signal output terminal 11A, and outputs the detected level value to the system control circuit 24. Is going. Therefore, the system control circuit 24 can recognize the level EV of the tracking error signal.

  Next, the relationship between the level EV of the tracking error signal and the spot length L in the radial direction of the spot S which is the irradiation shape of the laser beam, that is, the spot diameter in the radial direction will be described with reference to FIGS.

  FIG. 4 shows the relationship between the defocus value, tracking error signal EV, and spot length L when the optical system of the optical pickup 12 has no astigmatism. In the figure, a solid line T indicates a change in the level EV of the tracking error signal with respect to a change in the defocus value of the focus servo circuit 21, and a solid line L indicates a change in the spot length L with respect to a change in the defocus value of the focus servo circuit 21. Is shown.

  FIG. 5 shows the relationship between the defocus value, tracking error signal EV and spot length L when the optical system of the optical pickup 12 has astigmatism. In the figure, a solid line T indicates a change in the level EV of the tracking error signal with respect to a change in the defocus value of the focus servo circuit 21, and a solid line L indicates a change in the spot length L with respect to a change in the defocus value of the focus servo circuit 21. Is shown.

  As apparent from the change in the level EV of the tracking error signal and the change in the spot length L shown in FIGS. 4 and 5, the relationship between the level EV of the tracking error signal and the spot length L changes in contrast. is there. Accordingly, if data indicating the relationship between the level EV of the tracking error signal and the spot length L for each defocus value is stored in the second spot diameter memory circuit 34 as table data, the tracking error signal level detection circuit 28 performs tracking. By detecting the level EV of the error signal, the spot length L, that is, the spot diameter S2 perpendicular to the signal track of the spot S with respect to the signal track of the laser beam can be obtained from the table data.

As described above, the detection operation of the spot diameter S1 in the signal track direction and the spot diameter S2 in the direction perpendicular to the signal track is performed. In the present invention, such detection operation is performed from the tilt control circuit 22 to the tilt adjustment coil 18. By changing the level of the drive signal supplied to the lens, the inclination of the objective lens 14 is changed each time it is changed stepwise. That is, each time the drive voltage value supplied from the tilt control circuit 22 to the tilt adjustment coil 18 is changed stepwise from the minus side to the plus side, the aforementioned spot diameters S1 and S2 are detected.

  When the tilt of the objective lens 14 with respect to the optical disc D is changed by changing the drive voltage supplied to the tilt adjustment coil 18, the shape of the spot S changes, so that the spot diameters S1 and S2 change. When the values of the spot diameters S1 and S2 are obtained each time the drive voltage supplied to the tilt adjustment coil 18 is changed, an operation for calculating the ratio R2 from the obtained spot diameters S1 and S2 is performed.

  The shape of the spot S can be recognized from the ratio R2 thus obtained, and the size of the spot S can be determined from the spot diameters S1 and S2.

  As described above, when the value of the ratio R2 obtained from the spot diameters S1 and S2 is obtained, the ratio R2 is within a predetermined value, that is, the shape of the spot S is a shape suitable for performing the recording operation and the reproducing operation. In order to determine whether or not it is within a preset value range, it is determined whether or not it is within a predetermined range, and a tilt setting drive which is a drive signal supplied to the tilt adjustment coil 18 that obtains a spot shape within a predetermined range. An operation of storing a signal value in a memory circuit (not shown) provided in the tilt control circuit 22 is performed. The value of the tilt setting drive signal set by such an operation is, for example, an intermediate value when the ratio R2 obtained at the level of the plurality of drive signals changed in stages is within a predetermined value. Set to the value of.

  In this way, the recording operation can be performed by setting the drive signal value supplied from the tilt control circuit 22 to the tilt adjustment coil 18. The recording operation is performed by selecting data stored as table data in the recording strategy memory circuit 36 based on the shape of S and the spot diameters S1 and S2.

  That is, the data selected and read from the recording strategy memory circuit 36 is a laser having a pulse waveform suitable for recording a signal on the optical disk D using the laser beam having the shape of the spot S, that is, the spot diameters S1 and S2. Since the drive signal is data that can be generated from the laser drive signal generation circuit 29, the signal recording operation on the optical disc D can be performed accurately.

1 is a block circuit diagram showing an embodiment of an optical disc recording / reproducing apparatus according to the present invention. It is explanatory drawing which shows the relationship between the pit formed in the signal track | truck of an optical disk, and the spot of a laser beam. It is a signal waveform diagram for demonstrating operation | movement of this invention. It is a characteristic view for demonstrating operation | movement of this invention. It is a characteristic view for demonstrating operation | movement of this invention. 1 is a block circuit diagram showing an embodiment of a tracking error signal generation circuit used in the present invention. FIG. 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

D optical disc 12 optical pickup 13 laser diode 15 photodetector 16 tracking coil 17 focusing coil 18 tilt adjustment coil 19 optical output signal processing circuit 20 tracking servo circuit 21 focus servo circuit 22 tilt control circuit 24 system control circuit 25 RF signal level Detection circuit 28 Signal recording circuit 29 Laser drive signal generation circuit 30 Laser drive circuit 31 First spot diameter memory circuit 32 Tracking error signal level detection circuit 33 Defocus value setting circuit 34 Second spot diameter memory circuit 35 Laser drive signal control circuit 36 Recording strategy memory circuit

Claims (4)

An optical system having a tilt adjustment coil for adjusting the tilt of the objective lens and configured to perform a tracking control operation by a tracking error signal generated based on a phase difference between signals obtained from the quadrant photodetector. A recording control method for an optical disc recording / reproducing apparatus configured to record a signal on an optical disc by using a pickup and forming a plurality of pits having different lengths by a laser beam on the optical disc, and supplying the signal to a tilt adjustment coil Each time the value of the tilt coil drive signal is changed, the spot diameter in the signal track direction is detected and tracked by comparing the level of the RF signal obtained by reproducing the pits of different lengths recorded on the optical disc Tracking error when the servo is inactive -By detecting the level of the signal, the spot diameter in the direction perpendicular to the signal track is detected, and the value of the tilt drive signal is set so that the ratio of the spot diameter in the track direction to the spot diameter in the direction perpendicular to the track is within a predetermined value. A recording control method for an optical disc recording / reproducing apparatus, wherein the recording control method is set. 2. The recording control method according to claim 1, wherein the level comparison operation is performed by an RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disc. 2. The recording control method according to claim 1, wherein the spot diameter is detected based on a level difference between a maximum level and a minimum level of the tracking error signal. A recording strategy memory circuit is provided in which a plurality of recording strategies corresponding to the ratio of the spot diameter in the track direction and the spot diameter in the direction perpendicular to the recording direction are provided, and the recording strategy stored in the recording strategy memory circuit is selected based on the ratio of the spot diameters The recording control method according to claim 1, wherein the recording strategy is set by doing so.

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