JP2005166088A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive which can stably control tracking and focusing by suppressing the influence of the surface wobbling of the disk. <P>SOLUTION: The surface wobbling detector 50 of this disk drive detects the amount of surface wobbling from the output signals (focusing error signals) of the focusing error detector 20 at low recording speed (linear speed) and stores it in the memory 58. The controller 40 obtains the biasing amount from the surface wobbling and outputs it to the biasing section 56 to apply the bias signal corresponding to the area of recording. Accordingly, correct focusing servo is made possible by maintaining a constant distance between the focusing lens of the optical pickup 14 and the optical disk 12 even when recording at high linear speed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus for recording or reproducing a signal on an optical disc using a converged light beam applied to the optical disc apparatus.

  2. Description of the Related Art Optical information recording media (optical disks) capable of recording information such as write-once type with laser light are known. As this optical disc, a large-capacity optical disc (so-called CD-R) is known as compared with a flexible disc, and information recording is performed by converting a laser beam in the near infrared region (for example, a wavelength near 780 nm) into a CD-R. This is done by irradiating. The irradiated portion of the recording layer absorbs laser light and locally rises in temperature, and information is recorded by a change in optical characteristics due to a physical or chemical change (for example, generation of pits).

  In recent years, with the progress of the information society, the amount of information distributed has been increasing, and in response to the demand for a larger capacity optical information recording medium, a larger capacity optical disc (recordable digital vasatile disc, so-called DVD). -R and DVD-RW) are being distributed. This DVD-R has a transparent disk shape in which the guide groove (pre-groove) for tracking the irradiated laser beam is narrower than half of the CD-R (0.74 to 0.8 μm). On the substrate, a recording layer made of a dye, a light reflection layer, and, if necessary, a protective layer are sequentially provided. Information recording / reproduction on the DVD-R can be performed at a higher density than the CD-R by irradiation with a laser beam having a wavelength shorter than that of the CD-R (for example, a wavelength of 630 nm to 680 nm).

  Such recording and reproduction on the optical disk is performed by a dedicated recording and reproduction device. For example, an optical disc apparatus irradiates an information track provided on an optical disc with a light spot and performs focus control to follow the optical spot on the optical disc to compensate for the defocus. Tracking control is made to follow to compensate.

  In other words, the optical spot is caused to follow the information track while suppressing the influence of errors due to disturbances such as surface blurring and eccentricity of the optical disc or external vibration by focus control and tracking control. For this reason, a gain is set in focus control and tracking control.

  However, when the gain is set, the gain is fixed, and it is sometimes difficult to follow the light spot in the case of an optical disc having a large surface deviation or eccentricity beyond the gain.

Therefore, a technique for improving the followability of the light spot has been proposed (see Patent Document 1). In this technology, the low frequency component of the optical disc is extracted by detecting the low frequency component of the focus signal and tracking signal, and the amplification factor of the low frequency component is increased. This enables stable focus control and tracking control without increasing focus control and tracking control gain.
Japanese Patent Laid-Open No. 6-4989 (pages 5 to 8, FIGS. 1 and 8)

  However, since the optical disk has a large capacity, the recording speed has been increased, and there are cases where the tracking performance that was possible at the time of low speed cannot be obtained at high speed. For example, media manufacturers such as DVD-R supply media based on their own technology or supply multiple types of media. Depending on the manufacturing conditions and storage conditions, some of the optical discs may be subtle. Even for a medium that supports high-speed recording, such as deformation, the mechanical properties (surface runout, etc.) of the medium hardly changed from those for low-speed recording. For this reason, to obtain the follow-up performance that was possible at the time of low speed must be absorbed by the apparatus side.

  In view of the above facts, an object of the present invention is to obtain an optical disc apparatus capable of performing focus control on an optical disc in the best state regardless of the type of the optical disc.

  In order to achieve the above object, an optical disc apparatus of the present invention comprises at least rotating means for rotating an optical information recording medium capable of additional recording, and converging means for converging a light beam on the recording surface of the optical information recording medium. The focusing means is focused on the recording surface by a drive signal having a predetermined frequency characteristic based on a deviation from the focused state when the converging means is moved in a direction substantially perpendicular to the recording surface of the optical information recording medium. Focusing means for moving the converging means; moving means for moving the light beam in the radial direction of the optical information recording medium; position detecting means for detecting a position of the optical beam in the radial direction of the optical information recording medium; Based on deviation from the in-focus state when the optical information recording medium is rotated at a predetermined low speed for a plurality of regions in the radial direction of the optical information recording medium, the plurality of areas Setting means for determining a bias signal corresponding to the surface shake amount obtained by determining the surface shake amount of the optical information recording medium for each of the areas, and when rotating the optical information recording medium at a high speed faster than the low speed, An adding means for discriminating to which area the position of the light spot of the optical information recording medium belongs based on the detection result of the position detecting means, and adding the bias signal stored corresponding to the discriminated area to the drive signal And.

  According to the present invention, the setting means corresponds to the surface shake amount obtained by obtaining the surface shake amount by the deviation from the in-focus state when the plurality of regions in the radial direction of the optical information recording medium are rotated at a low speed. Define the bias signal. When the optical information recording medium is rotated at a high speed higher than the low speed, that is, when the signals of various detection systems of the apparatus shift to the high frequency side, it corresponds to the region where the light spot determined by the additional means is located. The bias signal stored in this way is added to the drive signal. As a result, it is possible to suppress a focus error caused by a surface shake caused by deformation or the like existing in at least a part of the optical information recording medium, to enable stable focusing, and to perform accurate focus control and tracking control. An optical disc device can be provided.

  Specifically, the optical disc apparatus of the present invention converges the light beam onto the recording surface of the optical information recording medium by the converging means while rotating the optical information recording medium such as an optical disc at least capable of additional recording by the rotating means. Record the data. The converging means is movable in a direction substantially perpendicular to the recording surface of the optical information recording medium, and the focusing means generates a drive signal based on the deviation from the in-focus state, and the drive signal generates a drive signal on the recording surface. The convergence means is moved so as to focus. This drive signal is a drive signal having a predetermined frequency characteristic and a so-called focus servo servo gain determined, and the servo gain decreases as the frequency increases. For this reason, as the rotation of the optical information recording medium becomes higher, the range in which the focused state is maintained becomes narrower, and the number of cases where a large deviation from the focused state is detected increases. In this case, if at least a part of the optical information recording medium is deformed (polar deformation), a displacement such as surface runout occurs. As a result, a focusing state cannot be obtained by the movement of the converging unit by the focusing unit, so-called defocused state, and a light spot due to the convergence of the converging unit cannot be obtained, and accurate recording cannot be performed.

  Therefore, the setting means determines a bias signal corresponding to the surface shake amount of the optical information recording medium. In other words, the setting means has the surface of the optical information recording medium for each of the plurality of areas due to deviation from the focused state when the plurality of areas in the radial direction of the optical information recording medium are rotated at a predetermined low speed. Find the runout amount. A bias signal corresponding to the obtained surface shake amount is determined. This bias signal is a signal for offset-moving the converging means so that the recording surface can be focused by a drive signal having a predetermined frequency characteristic.

  When determining the amount of surface shake, by moving the light beam in the radial direction of the optical information recording medium by the moving means, while detecting the position of the optical beam in the radial direction of the optical information recording medium by the position detecting means, Both movement of the light beam and position detection can be achieved.

  When the optical information recording medium is rotated at a high speed faster than the low speed, the adding means determines which area the position of the light spot of the optical information recording medium belongs to based on the detection result of the position detecting means. The bias signal stored corresponding to the area is added to the drive signal.

  Thereby, by suppressing a focusing error caused by surface blurring due to deformation of at least a part of the optical disc, stable focusing can be performed and accurate focus control can be performed.

  The focusing means includes a focusing means for moving the converging means in a direction substantially perpendicular to the recording surface of the optical information recording medium, and a deviation from the in-focus state in which the light beam is converged on the optical information recording medium. A focusing error detecting means for detecting the focusing error, and controlling the focusing means to focus on the recording surface of the optical information recording medium by a drive signal having a predetermined frequency characteristic based on the detection result of the focusing error detecting means. And focusing control means.

  The focusing means preferably maintains the in-focus state by moving the converging means. Therefore, the focusing means for moving the converging means includes the focusing means and moves the converging means in a direction substantially perpendicular to the recording surface of the optical information recording medium by the focusing means. Then, the deviation from the in-focus state is detected by the in-focus error detecting means, and the in-focus control means focuses on the recording surface of the optical information recording medium with a drive signal having a predetermined frequency characteristic according to the deviation from the in-focus state. The focusing means is controlled to do so. As a result, it is possible to control as much as possible while detecting a deviation from the in-focus state, and it is possible to maintain the in-focus more preferably, and it is possible to perform stable focusing.

  The setting means stores an error signal for storing a detection signal of the focusing error detection means when the optical information recording medium is rotated at a predetermined low speed for a plurality of radial regions of the optical information recording medium. And a bias setting means for determining a surface shake amount of the optical information recording medium for each area based on a detection signal stored in the storage means and setting a bias signal corresponding to the obtained surface shake amount. , Can be included.

  The setting means for determining the bias signal can predetermine the bias signal corresponding to the surface shake amount. However, the setting for each optical information recording medium can be performed by detecting the shape of each optical information recording medium. Is possible and preferable. Therefore, the error storage means stores the detection signal of the focusing error detection means when the optical information recording medium is rotated at a predetermined low speed for each of a plurality of regions in the radial direction of the optical information recording medium. The plurality of areas may be stored for each track for high accuracy, but since a similar detection signal from the focusing error detection means is obtained in the vicinity of adjacent tracks, a predetermined area is determined in advance. It is preferable. Then, the bias setting means obtains the surface shake amount of the optical information recording medium for each region based on the detection signal stored in the storage means and sets a bias signal corresponding to the obtained surface shake amount. Thereby, the setting for each optical information recording medium becomes possible.

  The bias setting unit corresponds to the surface shake acceleration obtained by obtaining the surface shake acceleration of the optical information recording medium in each region with respect to each of a plurality of rotation speeds based on the detection result of the focus error detection unit. To determine the bias signal.

  The surface shake detected by the rotation of the optical information recording medium is detected as the degree of the deformation width of the surface shape with respect to unit time, that is, the surface shake speed as the characteristic of the detection signal. For this reason, if the acceleration which is the degree of the speed is detected, it can be predicted how much the surface shake will occur. Therefore, the bias setting means determines the bias signal corresponding to the surface shake acceleration obtained by obtaining the surface shake acceleration of the optical information recording medium in each region for each of a plurality of rotational speeds from the detection result of the focus error detection means. Thus, instead of setting the bias according to the result of detecting the surface shake state, it is possible to apply the bias of the predicted result. For this reason, it is possible to apply a bias in advance, and quick processing is possible.

  The optical disc apparatus includes a procedure according to the following information recording method. Specifically, a drive signal for converging the light spot on the recording surface of the optical information recording medium while detecting the focus of the light spot that converges the light beam on the recording surface of the optical information recording medium capable of at least additional recording. An optical disc apparatus including an output means for outputting, wherein the optical information recording medium is an information recording method for recording data by focusing the light beam on a recording surface of the optical information recording medium while rotating the optical information recording medium. For a plurality of areas in the radial direction of the optical information recording medium, an error signal indicating a deviation from the focus when the optical information recording medium is rotated at a predetermined low speed is stored, and the error signal is stored for each area. When the data is recorded on the optical information recording medium while rotating at a high speed faster than the low speed, a bias voltage of the optical information recording medium is set. DOO positions to determine if they belong to any area, characterized by adding the bias signal to the driving signal according to the determined area and rotational speed.

  In this way, even if there is a deformation in at least a part of the optical information recording medium, the focus error due to the surface shake can be suppressed without increasing the gain of the focus control system. And stable focus control is possible.

  As described above, according to the present invention, it is possible to perform stable tracking and perform accurate tracking control and focus control by suppressing a focusing error caused by surface blurring caused by deformation of at least a part of the optical disc. Therefore, the optical disc apparatus capable of accurate tracking control and focus control can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an optical disc apparatus 10 according to the present embodiment records signals on an optical disc 12 and reproduces signals from the optical disc 12. An optical pickup 14 incorporating a light source (not shown) such as a semiconductor laser is provided. Have. The optical pickup 14 includes a detector (not shown) such as a photodiode that receives reflected light obtained by reflecting a light beam emitted from a light source (not shown) reflected by the optical disk 12. The optical disc apparatus 10 also includes a motor drive unit 16 that rotates the optical disc 12 and a feed motor unit 18 that transports the optical pickup 14 in the radial direction of the optical disc 12.

  The optical pickup 14 includes a converging lens (converging means) for converging the light beam on the recording surface of the optical disc 12, a focus actuator for moving the converging lens in a direction crossing the recording surface, and a converging lens for the optical disc 12. It incorporates a tracking actuator that moves a small amount in the radial direction. The operations of these focus actuator and tracking actuator are controlled during so-called focus servo or tracking servo. That is, the focus actuator moves the converging lens in a direction substantially perpendicular to the recording surface of the optical disc 12 to follow the recording surface, and the tracking actuator moves the light spot in the radial direction of the optical disc 12. Thus, the information track of the optical disk 12 is tracked.

  This tracking actuator moves the converging lens in the radial direction of the optical disk 12 by a small amount within the optical pickup 14 to follow the information track, so that it can follow all the information tracks on the recording surface of the optical disk 12. In this case, it is necessary to move the optical pickup 14 itself. Therefore, the optical pickup 14 is connected to the feed motor unit 18, and the optical pickup 14 is moved in the radial direction of the optical disk 12 by the feed motor unit 18.

  A focus error detection unit 20 and a tracking error detection unit 30 are connected to the optical pickup 14. The focus error detection unit 20 is connected to a focus control unit 24 via a focus phase compensation unit 22, and the focus control unit 24 is connected to the optical pickup 14. The tracking error detection unit 30 is connected to the tracking control unit 34 via the tracking phase compensation unit 32, and the tracking control unit 34 is connected to the optical pickup 14.

  The focus error detection unit 20 detects a focused state when the light beam is converged (outputs a focus error signal). The focus phase compensation unit 22 outputs a signal for compensating for the phase shift from the in-focus state based on the output signal (focus error signal) of the focus error detection unit 20. The focus control unit 24 drives and controls the focus actuator of the optical pickup 14 based on the output of the focus phase compensation unit 22.

  The focus actuator of the optical pickup 14 that performs focus servo is configured by the focus actuator of the optical pickup 14, the focus error detection unit 20, the focus phase compensation unit 22, and the focus control unit 24. When focus servo is applied by the focus control system having these configurations, the distance between the convergent lens and the recording surface of the optical disc 12 is maintained constant.

  The tracking error detection unit 30 detects a positional deviation between the information track and the light beam (converged light spot) on the recording surface of the optical disc 12. A signal for compensating for the phase shift between the light spot and the information track is output from the output signal of the tracking error detector 30. The tracking control unit 34 drives and controls the tracking actuator of the optical pickup 14 based on the output of the tracking phase compensation unit 32.

  These tracking actuator of the optical pickup 14, the tracking error detection unit 30, the tracking phase compensation unit 32, and the tracking control unit 34 constitute a tracking control system of the optical disc apparatus 10 that performs tracking servo. When tracking servo is applied by the tracking control system configured as described above, the position of the light spot converged by the converging lens is maintained so as to follow the information track of the optical disc 12.

  As is well known, the optical disk 12 is rotated so that the linear velocity is constant (for example, 1.4 m / s or 3.5 m / s). For this reason, the rotational speed of the optical disk 12 is controlled according to the position of the optical pickup 14. Therefore, the optical disc apparatus 10 includes a rotation detection unit 44 and a rotation control unit 42, and the optical pickup 14 is connected to the rotation detection unit 44, and the rotation detection unit 44 is connected to the motor via the rotation control unit 42. It is connected to the drive unit 16. The rotation detection unit 44 and the rotation control unit 42 constitute a rotation control system of the optical disc apparatus 10 that performs rotation servo. When rotation servo is applied by the rotation control system having these configurations, the linear velocity is maintained constant at the position of the light spot converged on the optical disk 12 (in the radial direction of the optical disk 12).

  The optical disc apparatus 10 according to the present embodiment includes a controller 40. As will be described later, the controller 40 controls application of a bias signal obtained based on an output signal (focus error signal) of the focus error detection unit 20 when the optical disk 12 is rotated at a low speed during high-speed rotation. It is. The controller 40 has a computer configuration not shown, and further includes a memory 58 for storing various data used when applying a bias signal.

  The controller 40 is connected to a surface vibration detection unit 50, a movement control unit 52, a region detection unit 54, and a bias applying unit 56. A focus control unit 24, a tracking control unit 34, and a rotation control unit 42 are also connected.

  The surface vibration detection unit 50 detects the surface vibration amount of the optical disk 12 from the output signal (focus error signal) of the focus error detection unit 20 when the optical disk 12 is rotated at a low speed in the detection mode described later. The result is output to the controller 40. The movement control unit 52 controls the movement of the optical pickup 14 in the radial direction of the optical disc 12 in the detection mode. The area detection unit 54 detects which area of the plurality of areas predetermined on the optical disk 12 the position of the light spot converged by the optical pickup 14 is in a recording mode to be described later. The bias applying unit 56 applies a bias signal corresponding to the rotation speed of the optical disc 12 and the region where the light spot is located in the recording mode.

  The motor drive unit 16 and the rotation control unit 42 of the present embodiment correspond to the rotation unit of the present invention, and the converging lens built in the optical pickup 14 corresponds to the convergence unit of the present invention. Further, the portion where the optical pickup 14 is controlled by the focus error detection unit 20, the focus phase compensation unit 22, and the focus control unit 24 corresponds to the focus unit of the present invention. The feed motor unit 18 corresponds to the moving unit of the present invention, and the tracking control unit 34 and the area detecting unit 54 correspond to the position detecting unit of the present invention. Further, the surface vibration detection unit 50 and the controller 40 of the present embodiment correspond to the setting unit of the present invention, and the bias applying unit 56 corresponds to the addition unit of the present invention.

  Further, the focus actuator of the present embodiment corresponds to the focusing means of the present invention, the focus error detection unit 20 corresponds to the sum / error error detection unit of the present invention, and the focus phase compensation unit 22 and the focus control unit 24 correspond to the present invention. This corresponds to the focus control means of the invention.

  The memory 58 of the present embodiment corresponds to an error storage unit of the present invention, and a portion for setting a signal to be supplied to the bias applying unit 56 in the controller 40 corresponds to a bias setting unit of the present invention.

  Here, the following performance of the optical pickup 14 will be described. FIG. 2 shows a characteristic diagram regarding the focus performance. 2A shows the frequency characteristics of the focus actuator of the optical pickup 14, FIG. 2B shows the frequency characteristics of the focus phase compensation unit 22, and FIG. 2C shows the focus control system described above. The transfer frequency characteristics are shown.

  In the transfer frequency characteristic shown in FIG. 2C, the reciprocal of the gain is the suppression ratio of the focusing tracking error. Therefore, an error caused by the surface shake of the optical disk 12 can be suppressed by increasing the gain near the rotation frequency of the optical disk 12.

  The tracking performance is substantially the same except that the frequency is different from the focus performance described above, and the description thereof is omitted.

  Next, the operation principle of the optical pickup 14 of the present embodiment that enables accurate recording will be described.

  The optical disk 12 is premised on being formed with high flatness, but often has local deformation or deflection depending on the manufacturing and storage conditions. In recent years, high-speed recording has progressed, and as the recording speed increases, the influence of local deformation, deflection, and the like appears significantly during recording. That is, if the optical disk 12 has local deformation or deflection, the local deformation portion causes a behavior that causes surface vibration, and a focus error (in-focus error) increases, so that accurate recording is not performed. . In the present embodiment, even the optical disc 12 having such a locally deformed portion enables high-speed recording with a simple configuration.

  FIG. 3 shows an optical disc 12 having a local deformation portion 13. The deforming portion 13 has a displacement in a direction intersecting the recording surface with respect to other areas on the optical disc 12. FIG. 4 is a characteristic diagram for explaining the level fluctuation of the optical pickup 14 in the optical disk 12 having the deforming portion 13. This level fluctuation indicates the drive voltage supplied to the optical pickup 14 when the optical pickup 14 follows the recording surface by the focus servo while rotating the optical disk 12 at a constant linear velocity.

  FIG. 4A shows the drive voltage characteristics of the optical pickup 14 when the optical disk 12 is rotated at a low speed (for example, a single speed). In this characteristic diagram, time TA indicates the tracking time when the deforming portion 13 is tracked by the optical pickup 14, and voltage VA indicates a variable voltage. When the optical disk 12 is rotated at a high linear velocity (for example, 8 × speed), as shown in FIG. 4B, the follow-up time of the deformation unit 13 is shortened from time TA to time TB. On the other hand, the voltage of the level variation cannot follow the surface fluctuation unless the voltage VA is maintained.

  However, in practice, as shown in FIG. 4C, the follow-up time of the deformation unit 13 is shortened from the time TA to the time TB, but the level fluctuation voltage decreases from the voltage VA to the voltage VB. This is considered that the surface vibration due to rotation could not be absorbed by the focus servo, and the optical pickup 14 could not follow. That is, it is considered that the distance between the recording surface of the optical disk 12 and the optical pickup 14 cannot be kept constant and the optical pickup 14 cannot be moved. For this reason, since a temporary defocus state is generated, accurate information cannot be recorded. As described above, information can be recorded accurately when the optical disk 12 is rotated at a low linear velocity, but the accuracy of information recording is lost as the speed increases.

  In this case, the focus servo characteristic should be improved, that is, the focus servo gain should be increased, but depending on the amount of increase, the tracking performance is deteriorated by the occurrence of beat (oscillation) during normal focus servo. It may happen.

  The inventor has conducted various experiments that the behavior of the optical pickup 14 changes as the linear velocity during recording (hereinafter referred to as recording velocity) is increased.

  FIG. 5 shows the characteristics of the focus error signal with respect to the recording speed. FIG. 5 (A) shows 1 × speed, FIG. 5 (B) shows 2 × speed, FIG. 5 (C) shows 4 × speed, and FIG. Double speed, FIG. 5 (E) shows 8 * speed. Note that the linear side degree of 1 × speed is 3.49 ± 0.03 m / s, and in the figure, the measurement range is obtained by measuring one round at the position of the optical disk 12 at a radius of 55 mm. As can be understood from FIG. 5, the fluctuation of the focus error signal increases as the recording speed increases.

  6 shows the in-plane distribution of the surface shake amount of the optical disk 12, FIG. 6A shows the surface shake amount at a position with a radius of 55 mm from the center of the disk, and FIG. 6B shows the position at a position with a radius of 40 mm from the center of the disk. Surface runout amount, FIG. 6C shows the surface runout amount at a radius of 25 mm from the disc center. As can be understood from FIG. 6, the surface runout occurs in the same angle region on the optical disc 12, and the fluctuation amount of the surface runout increases as it moves to the outer periphery of the optical disc 12.

  7 shows the in-plane distribution of the surface shake acceleration of the optical disk 12, FIG. 7A shows the surface shake acceleration at a position with a radius of 55 mm from the center of the disk, and FIG. 7B shows the position at a position with a radius of 40 mm from the center of the disk. Surface runout acceleration, FIG. 7C, shows the runout acceleration at a radius of 25 mm from the center of the disk. As understood from FIG. 7, the fluctuation of the surface shake acceleration occurs in the same angle region on the optical disk 12, and the surface shake acceleration increases as the movement to the outer periphery of the optical disk 12.

  In view of the above, the present inventor increases the focus servo gain by applying a bias to the optical pickup 14 itself, rather than improving the focus servo characteristics, when operating the optical pickup 14 during high-speed recording. It was found that the following performance can be obtained.

  That is, it is assumed that the focus error signal obtained when the recording speed is low, although the time is shortened, does not vary even when the recording speed is high. As described above, when the follow-up performance of the optical pickup 14 deteriorates as the recording speed increases, the drive error characteristic of the optical pickup 14 decreases, but the focus error signal increases.

  This is because the deterioration of the tracking performance of the optical pickup 14 with respect to the recording surface of the optical disk 12 appears in the focus error signal. The focus error signal at the time of good tracking performance fluctuates in its characteristic pattern even during high-speed recording. There seems to be no.

  For this reason, even if the recording speed is high by estimating the surface shake location on the basis of the focus error signal when the recording speed is low and applying a bias to the optical pickup 14 at the surface shake location. It is considered that the following performance can be secured.

  FIG. 8 is an explanatory diagram showing this principle. As shown in FIG. 8A, the driving voltage of the optical pickup 14 in the deforming unit 13 is the waveform CH1 when the recording speed is low, but becomes the waveform CH2 when the recording speed is high. In order to interpolate the fluctuation between the waveform CH1 and the waveform CH2, as shown in FIG. 8B, a bias waveform CH3 that is the difference between them is generated. The bias waveform CH3 may be within a difference value between the waveform CH1 and the waveform CH2 (CH3 ≦ CH1-CH2).

  By applying the bias waveform CH3 to the drive voltage, as shown in FIG. 8C, the drive waveform becomes a waveform CH4 that substantially matches the waveform CH1 when the recording speed is low, and the recording speed is high. Even if there is, follow-up performance can be secured.

  The bias waveform CH3 can be predicted from the focus error signal. As for the surface shake, a focus error signal having a fluctuation component is actually obtained with respect to a substantially constant focus error signal obtained when the focus servo is applied to the optical disk 12 serving as a reference having a high flatness. The fluctuation component appearing at the position corresponding to the surface shake increases as the recording speed of the optical disc 12 increases. Since this increased amount corresponds to the recording speed, it is possible to obtain a tendency corresponding to the recording speed by an experiment or the like in advance. In addition, as a signal substituted for the focus error signal used here, a drive signal itself for driving the focus actuator may be used. In this case, the fluctuation component appearing at the position corresponding to the surface shake can be obtained by passing the drive signal through the low-pass filter.

  Hereinafter, the operation of the present embodiment will be described. When the optical disc apparatus 10 of the present embodiment is activated and information recording on the optical disc 12 is instructed, the controller 40 executes a processing routine shown in FIG. This process is executed in either a detection mode in which a bias signal is set while detecting a focus error signal at a low recording speed, or a recording mode in which information is recorded by applying the bias signal. The

  In step 100 of FIG. 9, the initial setting of the optical disc apparatus 10 is executed. In this initial setting, various data in the detection mode and the recording mode are set. The data set in the detection mode includes a detection area on the optical disc 12, a linear velocity for controlling the rotation of the optical disc 12, a moving range (an area described later) of the optical pickup 14, and the like. In the recording mode, the recording speed for recording information on the optical disk 12 is set. After these settings, the following processing is set to be executed in the detection mode.

  In the next step 102, the linear velocity that is the recording velocity is switched (set) to the low linear velocity in the detection mode, and the rotation of the optical disk 12 is started. That is, the controller 40 outputs a rotation instruction to the rotation control unit 42 so that the optical disc 12 is rotated at a low speed, for example, DVD, at a linear speed of 1 × speed: 3.5 m / s. The rotation of the motor drive unit 16 is controlled.

  In the next step 104, a tracking position is designated by setting an area on the optical disk 12. That is, the controller 40 outputs a movement instruction to the movement control unit 52 so that the position of the optical pickup 14 is positioned at the designated tracking position, and the movement of the feed motor unit 18 is controlled by the movement control unit 52. At this time, a signal is output to the tracking control unit 34 to perform tracking servo.

  In the present embodiment, as shown in FIG. 3, the recording range of the optical disc 12 is classified into six areas of areas 12A, 12B, 12C, 12D, 12E, and 12F, and the following processing (detection) areas are made. . A predetermined position in each zone is set as a tracking position. In the present embodiment, a case where the recording range of the optical disc 12 is classified into six areas will be described, but the present invention is not limited to six. That is, it may be 5 or less, or 7 or more. The number of classifications may be classified in the area where the behavior of the focus error signal is representatively represented for the optical disc 12, and is preferably classified in about 5 mm steps in the radial direction after the radius of 40 mm. This is because, in principle, it is considered that the amount of surface deflection at the inner periphery is small.

  In step 104, first, the innermost area 12A is set, and in the next step 106, focus servo is applied. That is, a signal for compensating for a phase shift due to the focus error signal of the focus error detection unit 20 is output from the focus phase compensation unit 22, and based on this, the focus control unit 24 moves the focus actuator of the optical pickup 14 to the converging lens and the optical disk. Drive control is performed so that the distance between the 12 recording surfaces is kept constant.

  However, the follow-up performance of the converging lens deteriorates as the rotation of the optical disk 12 increases. For this reason, it is difficult to keep the distance between the convergent lens and the recording surface of the optical disk 12 constant, and the focus error signal varies. This variation corresponds to the surface deflection amount and position of the optical disk 12.

  Therefore, in the next step 108, the focus error signal is read and stored in the memory 58 in the next step 110. The process of step 108 corresponds to the process of the surface vibration detection unit 50. That is, the surface shake detection unit 50 stores the focus error signal read as the output of the focus error detection unit 20 as it is in the memory 58 as the surface shake amount in the area 12A, or calculates the surface shake amount from this focus error signal. The memory 58 is obtained and stored. When the surface shake amount is obtained from the focus error signal, a fluctuation component with respect to the substantially constant focus error signal obtained when the focus servo is applied with the optical disk 12 serving as a reference having high flatness is obtained as an amount corresponding to the surface shake. be able to. Note that, as the amount corresponding to the surface shake, the surface shake speed or the surface shake acceleration may be obtained from the output signal of the focus error detection unit 20 and stored.

  In the next step 112, it is determined whether or not the above process has been completed for all the areas set in the above step 102. If there is a remaining area, the process returns to step 104 and the above process is repeatedly executed. On the other hand, when the above process is completed for all areas, the result in step 112 is affirmative and the process proceeds to step 114.

  In step 114, the focus correction amount to be corrected when the recording speed is high is obtained from the focus error signal (surface shake amount) stored in the memory 58. In obtaining the focus correction amount, the increase amount of the focus error signal is predicted when the recording speed is high. That is, as described above, the component that appears as the surface shake in the focus error signal increases as the recording speed of the optical disc 12 increases. This is because the movement (focus control) in the optical axis direction of the optical pickup 14 (convergence lens) is at a speed (acceleration) that cannot be followed, and temporarily enters a defocus state. The tendency of the moving speed (acceleration) of the convergent lens that cannot be followed can be obtained in advance corresponding to the recording speed by experiments or the like. This is because the speed (acceleration) of the component appearing as surface shake in the focus error signal obtained at a low recording speed increases as the recording speed increases. If the velocity (acceleration) of the component that appears as surface vibration exceeds the tolerance of the focus servo, the optical pickup 14, that is, the converging lens cannot follow.

  Therefore, in the present embodiment, the bias signal is set according to the speed (acceleration) of the component that appears as surface shake at a low recording speed. This bias signal is determined in advance with respect to the magnitude of the speed (acceleration) of the component that appears as surface shake, and the speed (focus control) in which the optical pickup 14 (converging lens) moves in the optical axis direction (focus control) can follow ( To compensate for (acceleration).

  In the next step 116, the mode is set to the recording mode, and the linear velocity as the recording speed is switched (set) to the linear velocity in the recording mode, that is, the recording velocity set in the above step 100, and the optical disk 12 is rotated. To start. That is, the controller 40 outputs a rotation instruction to the rotation control unit 42 so that the optical disc 12 is rotated at a low speed, for example, a quadruple linear velocity, and the rotation control unit 42 controls the rotation of the motor driving unit 16. .

  In the next step 118, the tracking position on the optical disc 12 on which recording is performed is grasped. The grasping of the tracking position is to detect which of the set areas is included in the area detection unit 54. In the next step 120, a focus correction amount is given. That is, the controller 40 reads the focus correction amount (calculated in step 114) of the area grasped in step 118 and outputs it to the bias applying unit 56. In step 122, processing such as information recording is executed.

  Therefore, the focus control unit 24 outputs a signal obtained by adding a bias signal to the normal drive signal of the optical pickup 14 to the optical pickup 14 as a drive signal (see FIG. 8). As a result, the convergent lens of the optical pickup 14 can perform recording while maintaining a certain distance from the optical disk 12.

  In the next step 124, the negative determination is repeated until the processing of step 122 is completed. If the determination is negative, the process returns to step 118. If the determination is affirmative, the routine is ended.

  Thus, since the surface shake location is estimated based on the focus error signal when the recording speed is low, and recording is performed by applying a bias to the optical pickup 14 at the surface shake location, the recording speed is high. Thus, even when information is recorded on the optical disc 12, the in-focus state can be maintained without performing a so-called defocus state in which the focus error signal increases, and accurate focus control can be performed.

It is a block diagram which shows the structure of the optical disk apparatus concerning embodiment of this invention. FIG. 4A shows frequency characteristics of an optical pickup, FIG. 4A is a frequency characteristic of a focus actuator, FIG. 4B is a frequency characteristic of a focus phase compensator, and FIG. 4C is a diagram showing transmission frequency characteristics of a focus control system of an optical disc apparatus. . It is an image figure which shows the optical disk which has a local deformation | transformation part. The characteristic diagram for demonstrating the level fluctuation | variation of the optical pick-up in the optical disk which has a deformation | transformation part is shown, (A) is the drive voltage characteristic of an optical pick-up when an optical disk is rotated at a low linear velocity, (B) is high The driving voltage characteristic of the optical pickup which should be obtained when rotating at the speed, (C) shows the driving voltage characteristic of the optical pickup actually obtained. The characteristics of the focus error signal with respect to the recording speed are shown. (A) is 1 × speed, (B) is 2 × speed, (C) is 4 × speed, (D) is 6 × speed, and (E) is 8 × speed. The in-plane distribution of the surface shake amount of the optical disc is shown, (A) shows the position of the radius 55 mm from the center of the disc, (B) shows the position of the radius 40 mm, and (C) shows the surface shake amount at the position of radius 25 mm. The in-plane distribution of the surface vibration acceleration of the optical disk is shown, (A) shows the position of the surface vibration at a radius of 55 mm from the center of the disk, (B) shows the position of the radius of 40 mm, and (C) shows the surface vibration acceleration at the position of the radius 25 mm. FIG. 5A shows a drive signal to an optical pickup provided in the optical disc apparatus according to the embodiment of the present invention, FIG. 5A shows a drive signal fluctuation caused by a change in recording speed, and FIG. The driving signal at the time of high-speed recording is shown. 6 is a flowchart showing a flow of information recording in the optical disc apparatus according to the embodiment of the present invention.

Explanation of symbols

CH1 ... Waveform CH2 ... Waveform CH3 ... Bias Waveform 10 ... Optical Disc Device 12 ... Optical Discs 12A-12F ... Area 13 ... Deformation Unit 14 ... Optical Pickup 16 ... Motor Drive Unit 18 ... Feed Motor Unit 20 ... Focus Error Detection Unit 22 ... Focus Phase Compensation unit 24 ... focus control unit 30 ... tracking error detection unit 32 ... tracking phase compensation unit 34 ... tracking control unit 40 ... controller 42 ... rotation control unit 44 ... rotation detection unit 50 ... surface vibration detection unit 52 ... movement control unit 54 ... Area detecting unit 56 ... Bias applying unit 58 ... Memory

Claims (5)

A rotating means for rotating an optical information recording medium capable of at least additional recording;
A converging means for converging a light beam on the recording surface of the optical information recording medium;
The focusing means is focused on the recording surface by a drive signal having a predetermined frequency characteristic based on a deviation from the focused state when the focusing means is moved in a direction substantially perpendicular to the recording surface of the optical information recording medium. Focusing means for moving the convergence means;
Moving means for moving the light beam in the radial direction of the optical information recording medium;
Position detecting means for detecting a position of the light beam in the radial direction of the optical information recording medium;
For each of the plurality of regions in the radial direction of the optical information recording medium, based on the deviation from the in-focus state when the optical information recording medium is rotated at a predetermined low speed. Setting means for determining a bias signal corresponding to the surface shake amount obtained by calculating the surface shake amount of the optical information recording medium;
When the optical information recording medium is rotated at a high speed faster than the low speed, it is determined which area the position of the light spot of the optical information recording medium belongs based on the detection result of the position detecting means, and the determined area Appending means for appending the correspondingly stored bias signal to the drive signal;
An optical disc device comprising: The focusing means includes
Focusing means for moving the convergence means in a direction substantially perpendicular to the recording surface of the optical information recording medium;
A focus error detecting means for detecting a deviation from a focused state in which the light beam is converged on the optical information recording medium;
Focusing control means for controlling the focusing means so as to focus on the recording surface of the optical information recording medium by a drive signal having a predetermined frequency characteristic based on the detection result of the focusing error detecting means;
The optical disk apparatus according to claim 1, comprising: The setting means includes
Error storage means for storing a detection signal of the focusing error detection means when the optical information recording medium is rotated at a predetermined low speed for a plurality of radial directions of the optical information recording medium;
Bias setting means for determining a surface shake amount of the optical information recording medium for each area based on a detection signal stored in a storage means, and setting a bias signal corresponding to the obtained surface shake amount;
The optical disc apparatus according to claim 2, comprising: The bias setting means includes
Based on the detection result of the focusing error detection means, a bias signal is determined corresponding to the surface shake acceleration obtained by obtaining the surface shake acceleration of the optical information recording medium in each of the regions for each of a plurality of rotational speeds. The optical disk apparatus according to claim 3. Output means for outputting a drive signal for converging the light spot on the recording surface of the optical information recording medium while detecting the focus of the light spot having converged the light beam on the recording surface of the optical information recording medium capable of at least additional recording An information recording method for an optical disk device, wherein the data is recorded by focusing the light beam on a recording surface of the optical information recording medium while rotating the optical information recording medium,
For a plurality of areas in the radial direction of the optical information recording medium, storing an error signal representing a deviation from the focus when the optical information recording medium is rotated at a predetermined low speed,
For each region, set a bias voltage based on the error signal,
When recording data on the optical information recording medium while rotating at a high speed faster than the low speed, determine which region the position of the optical spot of the optical information recording medium belongs;
An information recording method for an optical disc apparatus, wherein the bias signal is added to the drive signal in accordance with the determined area and rotational speed.

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