JP2007035152A - Optical disc apparatus and method for correcting spherical aberration - Google Patents

Abstract

A jump operation can be completed in a certain time during an interlayer jump in a multilayer optical disc, and further, dynamic and proper correction of spherical aberration generated in a minute spot condensed on a recording layer of the multilayer optical disc Thus, an optical disc apparatus that can be performed in the same manner is obtained.
A first lens 8 and a second lens 9 for converging a light beam to a minute spot on a multilayer optical disc 1, a first lens driving element 10 and a focus driving element 11 for driving the lens, and a focal position of the minute spot. Servo error drive control unit 14 for controlling the spherical aberration, a spherical aberration detection unit 15 for outputting a spherical aberration detection signal, a spherical aberration drive control unit 16 for correcting spherical aberration based on the spherical aberration detection signal, and a controller unit for controlling these 17 until the focus control becomes normal, and the spherical aberration is statically corrected based on a predetermined standard correction amount, and after the focus control is normally operated, correction is made so as to dynamically correct based on the spherical aberration detection signal. Switch methods.
[Selection] Figure 1

Description

  The present invention relates to a focal position control method for an optical disc apparatus for recording and reproducing information on a multilayer optical disc having a plurality of recording layers.

  In recent years, the amount of data handled by digital devices has become enormous, and in order to cope with the enormous amount of data, the demand for high-density recording on optical disks has increased.

  In order to increase the recording density, it is necessary to reduce the spot diameter of the light beam focused on and focused on the optical disk by shortening the wavelength of the laser light source and increasing the numerical aperture (NA) of the objective lens. There is.

  By the way, generally, in an optical disc, the information recording layer is covered with a cover layer in order to protect the information recording layer from dust and scratches. In other words, the light beam emitted from the objective lens passes through the cover layer, and is focused on the information recording layer underneath to perform focus control so that the light beam passes through the cover layer. In doing so, spherical aberration (SA) occurs.

  This spherical aberration is proportional to the thickness of the cover layer and the fourth power of the numerical aperture. Normally, the objective lens is designed to cancel out this spherical aberration, and the spherical aberration of the light beam that has passed through the objective lens and the cover layer is sufficiently small. However, when the thickness of the cover layer deviates from a predetermined value, spherical aberration occurs in the light beam condensed on the information recording layer, the beam diameter increases, and information can be read and written correctly. The problem of disappearing arises.

  Furthermore, in recent years, a multilayer optical disc formed by laminating a plurality of information recording layers has been proposed. Such an optical pickup device for recording / reproducing a multilayer optical disc needs to focus the light beam sufficiently small for each information recording layer of the optical disc.

  However, since the thickness from the surface of the optical disc to each information recording layer is different, the spherical aberration generated when the light beam passes through the cover layer is different for each information recording layer. Therefore, when recording and reproducing a multilayer optical disk, it is necessary to correct spherical aberration for each information recording layer.

  Further, when the objective lens is decentered from the central axis of the collimating lens by the tracking operation in a state where the spherical aberration is corrected, coma aberration occurs in the direction in which the objective lens moves. When correcting spherical aberration of about the substrate thickness error, the amount of coma due to this decentration is small, but the correction amount is relatively small as when correcting spherical aberration for the layer spacing during recording and reproduction of a two-layer disc. If it is large, the influence of coma aberration due to this decentering becomes large, the spot is deteriorated by the tracking operation, and it adversely affects the recording and reproduction of the signal.

  In order to reduce the influence of coma aberration due to the decentering of the objective lens, it is necessary to adopt a double servo system in which the optical head itself performs a tracking operation in accordance with the rotation of the optical disk. However, since the double servo system moves the optical head itself, the mechanism system and the control system become complicated and the cost increases. Moreover, since the movable part is large, it is not suitable for high speed.

  Therefore, the optical head has a mechanism to detect and correct the substrate thickness error and spherical aberration that occurs when recording / reproducing on multiple recording layers, and also detects coma aberration caused by the decentering of the objective lens by tracking operation. By providing a correction mechanism, coma aberration caused by the decentering of the objective lens is reduced when spherical aberration correction is performed, and a double servo is unnecessary, realizing a high-density optical head suitable for higher speed at a lower cost. The technique is disclosed in Patent Document 1.

  The detection of spherical aberration and the detection of coma in the radial direction are performed simultaneously to correct in real time the coma that occurs with the decentration of the objective lens, and the allowable decentration amount of the objective lens is increased. In order to detect the spherical aberration and the coma aberration at the same time, the defocus signal and the tracking error signal of the inner region and the outer region of the reflected light beam are detected, respectively, and the differential signals are used as the spherical aberration and coma aberration signals.

  That is, Patent Document 1 discloses a method of detecting spherical aberration caused by the error of the cover layer thickness as an electrical signal. In this method, the focal position deviation signals of the central portion and the outer peripheral portion of the reflected light beam from the optical disc are individually detected, and the operation signals are detected as spherical aberration signals.

  For example, Patent Document 2 discloses a technique related to an optical disk apparatus that performs recording and reproduction on a multilayer optical disk.

  In FIG. 8, in the optical disc apparatus disclosed in Patent Document 2, changes in various signals in a jump operation when the focal point moves from the first recording layer to the second recording layer (hereinafter referred to as interlayer jump). The timing chart which showed an example is shown. The horizontal axis represents time, and the vertical axis represents voltage.

  If an interlayer jump command is issued while focus control is being performed on the first recording layer, the interlayer jump signal and the spherical aberration correction signal change using a signal corresponding to the command as a trigger. The interlayer jump signal is a kick pulse for starting the movement of the objective lens in order to move the focus position to the second recording layer by escaping the focus control loop for the first recording layer which has been recorded or reproduced so far. KP and a brake pulse BP for ending the above movement of the objective lens in order to shift to the focus control loop for the second recording layer. The spherical aberration correction signal shown in FIG. 8 is a signal waveform when the negative and positive lens groups constituting the spherical aberration correction lens group are moved by a driving method such as screw feed. Using the signal corresponding to the interlayer jump command as a trigger, the interval between the negative lens group and the positive lens group is changed until the spherical aberration correction amount changes from the correction amount A suitable for the first recording layer to the predetermined correction amount B. Voltage is applied to the driving means.

  According to the timing chart shown in FIG. 8, in the optical disc apparatus, when an interlayer jump command is output from the control means at time T1, the spherical aberration correction means starts correcting spherical aberration. Also, a kick pulse KP for moving the focal position from the first recording layer to the second recording layer is output almost simultaneously or after the correction of the spherical aberration is completed. The correction of the spherical aberration is completed at time T2. Then, a brake pulse BP for stopping the focal position in the second recording layer is output at time T3, and the jump between layers and the correction operation of spherical aberration are completed.

  By starting the movement of the focal position from the first recording layer to the second recording layer almost simultaneously with the start of changing the correction amount of the spherical aberration, the effect of performing the interlayer jump in a short time can be achieved. It has gained.

  Further, by completing the change of the correction amount of the spherical aberration before the movement of the focal position to the second recording layer is completed, it is possible to perform the focus control more stably. .

However, if it takes time to change the correction amount of the spherical aberration, the movement of the focal position to the second recording layer may be completed before the change of the correction amount of the spherical aberration is completed. Thus, the effect that the time required for the interlayer jump can be further shortened can be obtained.
JP 2002-358877 (released on December 13, 2002) JP 2002-157750 (published May 31, 2002)

  However, the conventional optical disc apparatus has the following problems.

  The spherical aberration detection method described in Patent Document 1 is based on the premise that focus control is performed and the light beam is focused on the recording layer. This method cannot be used when it is not in focus yet. By the way, in an optical disc apparatus that records and reproduces a multilayer optical disc having a plurality of recording layers, usually focus control is not performed at the time of interlayer jump, but focus control is performed again after interlayer jump. There is no mention of the procedure for jumping between layers.

  On the other hand, in the optical disc apparatus described in Patent Document 2, focus control is performed after correcting spherical aberration by a predetermined value at the time of interlayer jump. That is, there is no mechanism for dynamically detecting spherical aberration. For this reason, in the configuration of the optical disc apparatus described in Patent Document 2, it is impossible to perform correction according to the detected amount of the spherical aberration while detecting the spherical aberration as described in Patent Document 1. In Patent Document 2, the spherical aberration is corrected with a preset correction amount, and the correction amount is constant.

  However, since the spherical aberration is caused by the thickness error of the cover layer of the optical disk or the difference in thickness between the first recording layer and the second recording layer, that is, the difference in the thickness of the intermediate layer. It is not uniform over the entire area, and some variation is allowed. For this reason, if the amount of correction is constant throughout the entire optical disk as in the optical disk device described in Patent Document 2, optimal correction cannot be performed for manufacturing variations in cover layer thickness and intermediate layer thickness. For this reason, there is a problem that the beam diameter cannot be sufficiently narrowed and optimal recording / reproduction may not be performed.

  The present invention has been made in view of the above-described problems, and its purpose is to allow a jump operation to be completed in a substantially constant time at the time of interlayer jump in a multilayer optical disc composed of a plurality of recording layers. To obtain an optical disc apparatus capable of dynamically and appropriately correcting spherical aberration occurring in the plane of the optical disc.

  (1) In an optical disc apparatus that records or reproduces information on a multilayer optical disc having at least a first recording layer and a second recording layer, the light beam is focused on a minute spot on the multilayer optical disc. Optical system, focal position control means for controlling the focal position of the minute spot, and spherical aberration detection means for detecting spherical aberration due to at least one of the condensing optical system or the multilayer optical disk and outputting a spherical aberration detection signal And spherical aberration correcting means for correcting the spherical aberration based on the spherical aberration detection signal, and condensing optics for driving the condensing optical system for moving the focal position of the minute spot or correcting the spherical aberration. A system driving unit, a condensing optical system driving unit, and a control unit for controlling the spherical aberration correcting unit, and the focal position of the minute spot is determined according to the first description. When performing an interlayer jump to change from a layer to the second recording layer, the spherical aberration correction method, after the focal position of the micro spot moves from the first recording layer to the second recording layer, Until it is confirmed that the focus control by the focus position control means is normally performed, a static correction method based on a standard correction amount set in advance corresponding to the second recording layer is used. After confirming the normal operation of the focus control by the focus position control means, the spherical aberration correction means switches the correction method of the spherical aberration so as to be a dynamic correction method based on the spherical aberration detection signal. To do.

  In this configuration, the control means issues a command to perform an interlayer jump to the focal position control means and the spherical aberration correction means. In response to this command, the focal position control means causes the condensing optical system driving means to move the focal position of the minute spot from the first recording layer to the second recording layer. The driving of the optical system is ordered, and the condensing optical system driving means starts moving the condensing optical system. The spherical aberration correction means corrects the spherical aberration of the condensing optical system by a static correction method based on a preset standard correction amount (standard spherical aberration correction amount) corresponding to the second recording layer. Therefore, the condensing optical system driving unit is instructed to drive the condensing optical system, and the condensing optical system driving unit starts to move the condensing optical system. The spherical aberration correction means confirms the normal operation of the focus control by the focus position control means after the focal position of the minute spot has moved to the second recording layer, and then the spherical aberration correction method is changed to the static aberration correction method. From this method, the spherical aberration detection unit switches to a dynamic correction method based on the spherical aberration detection signal in which the spherical aberration is detected, and corrects the spherical aberration of the condensing optical system.

  According to the above configuration, even when the spherical aberration detection unit has not yet output the correct spherical aberration detection signal before normal focus control by the focus control unit is performed at the time of interlayer jump, The spherical aberration correction means starts correcting the spherical aberration using a static correction method based on the standard spherical aberration correction amount. Therefore, the spherical aberration correcting unit can start correcting the spherical aberration of the condensing optical system without waiting for the normal operation of the focus control.

  Therefore, the movement of the focal position and the correction of the spherical aberration are performed in parallel as compared with the case where the spherical aberration correction means starts correcting the spherical aberration after confirming the normal operation of the focus control by the focal position control means. Therefore, the time required for a series of operations accompanying the interlayer jump can be shortened.

  Even if the movement of the focal position fails and the movement of the focal position is performed again, the spherical aberration correction means corrects the spherical aberration using a static correction method based on the standard spherical aberration correction amount. Since it can be performed in parallel, the time to redo the movement of the focal position does not cause a delay in the spherical aberration correction completion time.

  Furthermore, after normal focus control by the focus position control means is started, the spherical aberration detection means may output the correct spherical aberration detection signal based on the spherical aberration actually detected in the multilayer optical disc. it can. In other words, the spherical aberration correction means can dynamically correct the spherical aberration of the condensing optical system based on the spherical aberration detection signal corresponding to the situation of each of the multilayer optical discs. Further, since spherical aberration is corrected to some extent by static correction before starting dynamic correction of spherical aberration, the dynamic correction can be finely corrected.

  As described above, according to the present invention, the time required for the movement of the focal position and the correction of the spherical aberration of the condensing optical system is not wasted at all, and the time can be shortened as compared with the prior art.

  (2) In order to solve the above-described problem, the optical disc apparatus according to the present invention is configured such that the spherical aberration correcting unit corrects the spherical aberration after the focal position control unit starts moving the focal position of the minute spot. It is characterized by starting.

  According to the above configuration, the focal position of the minute spot is moved by the focal position control means prior to the start of spherical aberration correction. In general, the spherical aberration detection means can output the correct spherical aberration detection signal only when normal focus control is performed by the focus position control means. If the movement of the focal position is started before the correction of the spherical aberration, the normal focus control by the focal position control means is performed at an earlier timing than when the movement of the focal position and the correction of the spherical aberration are started at the same time. . Accordingly, the spherical aberration correcting means can perform dynamic correction of the spherical aberration at an earlier timing than when the movement of the focal position and the correction of the spherical aberration are started simultaneously. As a result, optimal correction can be performed for manufacturing variations in cover layer thickness and intermediate layer thickness. Accordingly, the beam diameter can be sufficiently reduced, and optimum recording / reproduction can be performed.

  (3) In order to solve the above problems, the optical disk apparatus according to the present invention continues to correct the spherical aberration by the spherical aberration correcting means when the movement of the focal position by the focal position control means fails. The focus position control means redoes the movement of the focus position.

  According to the above configuration, even if the movement of the focal position fails, the time required for correcting the spherical aberration is usually longer than the time required for the movement of the focal position. This redo is completed while the spherical aberration is being corrected. Therefore, the time required for a series of operations associated with the interlayer jump can always be kept at a substantially constant time necessary for correcting the spherical aberration even when the movement of the focal position fails.

  (4) In order to solve the above-described problem, the optical disk apparatus according to the present invention is configured to stop the driving of the focusing optical system that is driven to move the focal position by an interlayer jump. During the period from when the focus position control means issues a drive stop command to the system drive means until the normal operation of the focus position control by the focus position control means is confirmed, the spherical aberration correction means The correction is started.

  In this configuration, in order to stop the driving of the condensing optical system that is being driven for the movement of the focal position due to the interlayer jump, the focus position control unit instructs the converging optical system driving unit to stop driving. The spherical aberration correction means starts a method for static correction of the spherical aberration during a period from when the normal position movement is confirmed to when normal operation of the focus position control by the focus position control means is confirmed.

  As a result, it is expected that the focus control by the focus control unit will be normal after the focus position control unit issues a drive stop command as the timing when the spherical aberration correction unit starts the static correction method of the spherical aberration. The timing can be set in advance within the above period. This timing is obtained by measuring in advance how long it takes to move the focal position when the focal position is normally moved. The timing allows the dynamic correction of spherical aberration using the spherical aberration detection signal to be started earlier, and even if a retry operation is performed due to the failure to move the focal position, a series of interlayer jumps is performed. In view of the fact that the processing time does not change, it is considered that this is a preferable timing for starting static correction of spherical aberration.

  Even if the focus position movement by the focus position control unit fails and the focus control is not normally performed at the timing, the spherical aberration correction unit uses the standard spherical aberration correction amount to correct the spherical aberration. Start static correction.

  On the other hand, in the method of performing the static correction of spherical aberration after the movement of the focal position is completed and the normal operation of the focal point control is confirmed, if the movement of the focal position accompanying the interlayer jump fails, The time required for a series of operations associated with the interlayer jump is extended by the time required to redo the position movement. However, according to the above configuration, since the re-movement of the focal position is completed during the correction of the spherical aberration, the time required for a series of operations accompanying the interlayer jump is substantially equal to the time required for the correction of the spherical aberration Can be kept in.

  (5) A method for correcting spherical aberration according to the present invention includes a method for correcting spherical aberration performed by an optical disc apparatus that records or reproduces information on a multilayer optical disc including at least a first recording layer and a second recording layer. In the correction method, an interlayer jump is performed to change the focal position of a minute spot formed by converging a light beam on the multilayer optical disk via a condensing optical system from the first recording layer to the second recording layer. When performing, for the correction method of spherical aberration caused by at least one of the condensing optical system or the multilayer optical disc, the focal position of the micro spot moves from the first recording layer to the second recording layer, Until the control of the focal position of the minute spot is normally performed, a static correction method based on a standard correction amount set in advance corresponding to the second recording layer is executed to control the focal position. After it was successful, and executes a dynamic correction method based on the detection signal of the spherical aberration.

  In this method, after the focal position of the micro spot is moved from the first recording layer to the second recording layer, until the focal position of the micro spot is normally controlled, the second recording layer Correspondingly, a static correction method based on a preset standard correction amount is executed, and after the focus position is normally controlled, a dynamic correction method based on the detection signal of the spherical aberration is performed. Execute.

  That is, the condensing optical system is first driven in order to move the focal position of the minute spot from the first recording layer to the second recording layer in response to a command for performing an interlayer jump. Next, the condensing optical system is driven to correct spherical aberration of the condensing optical system by a static correction method based on a preset standard spherical aberration correction amount corresponding to the second recording layer. Is done. After the focal position of the minute spot moves to the second recording layer and confirms the normal operation of the focus control, the spherical aberration correction method is changed from the static method to the detected spherical aberration detection signal. Switching to a dynamic correction method based on this, the spherical aberration of the condensing optical system is corrected.

  According to this method, the static correction method based on the standard spherical aberration correction amount is used even when the correct spherical aberration is not detected before normal focus control is performed at the time of interlayer jump. Start correction of spherical aberration. Therefore, correction of spherical aberration of the condensing optical system can be started without waiting for normal operation of focus control.

  Therefore, as compared with the case where the correction of the spherical aberration is started after confirming the normal operation of the focus control, a series of operations associated with the interlayer jump is required as much as the movement of the focal position and the correction of the spherical aberration are performed in parallel. Time can be shortened.

  Even if the movement of the focal position fails and the movement of the focal position is performed again, the spherical aberration can be corrected in parallel using the static correction method based on the standard spherical aberration correction amount. The time to redo the movement of the position does not cause a delay in the spherical aberration correction completion time.

  Furthermore, after normal focus control is started, dynamic spherical aberration correction based on the spherical aberration actually detected in the multilayer optical disc is performed. That is, by this method, the spherical aberration of the condensing optical system can be dynamically corrected based on the spherical aberration detection signal corresponding to the situation of each of the multilayer optical discs. Further, since spherical aberration is corrected to some extent by static correction before starting dynamic correction of spherical aberration, the dynamic correction can be finely corrected.

  As described above, according to the present invention, the time required for the movement of the focal position and the correction of the spherical aberration of the condensing optical system is not wasted at all, and the time can be reduced as compared with the prior art.

The spherical aberration correction method according to the present invention may be specified as follows.
That is, in a spherical aberration correction method executed by an optical disc apparatus that records or reproduces information on a multilayer optical disc including at least a first recording layer and a second recording layer,
(1) Execute an interlayer jump to change the focal position of a minute spot formed by converging a light beam on the multilayer optical disc via a condensing optical system from the first recording layer to the second recording layer And steps to
(2) determining whether the control of the focal position of the minute spot has been normally performed;
(3) After the focal position of the micro spot is moved from the first recording layer to the second recording layer, until it is determined that the control of the focal position of the micro spot is normally performed, Executing a static correction method based on a standard correction amount set in advance corresponding to the recording layer;
(4) After determining that the control of the focal position is normally performed, executing a dynamic correction method based on the detection signal of the spherical aberration;
A method of correcting spherical aberration, comprising:

  An optical disc apparatus according to the present invention includes a condensing optical system that converges a light beam onto a minute spot on the multilayer optical disc, a focal position control unit that controls a focal position of the minute spot, and the condensing optical system or the multilayer. Spherical aberration detection means for detecting spherical aberration caused by at least one of the optical discs and outputting a spherical aberration detection signal; spherical aberration correction means for correcting the spherical aberration based on the spherical aberration detection signal; and focus of the minute spot A condensing optical system driving means for driving the condensing optical system for moving the position or correcting the spherical aberration, and a control means for controlling the condensing optical system driving means and the spherical aberration correcting means, When performing an interlayer jump to change the focal position of the minute spot from the first recording layer to the second recording layer, the spherical aberration correction method is the minute aberration correction. After the focal position of the pot is moved from the first recording layer to the second recording layer, the second recording layer is confirmed until it is confirmed that the focus control by the focal position control means is normally performed. And a dynamic correction method based on the spherical aberration detection signal after confirming normal operation of the focus control by the focus position control means. As described above, the spherical aberration correction unit switches the correction method of the spherical aberration.

  According to the above configuration, even when the spherical aberration detection unit has not yet output the correct spherical aberration detection signal before normal focus control by the focus control unit is performed at the time of interlayer jump, The spherical aberration correction means starts correcting the spherical aberration using a static correction method based on the standard spherical aberration correction amount. Therefore, the spherical aberration correcting unit can start correcting the spherical aberration of the condensing optical system without waiting for the normal operation of the focus control.

  Therefore, the movement of the focal position and the correction of the spherical aberration are performed in parallel as compared with the case where the spherical aberration correction means starts correcting the spherical aberration after confirming the normal operation of the focus control by the focal position control means. Therefore, the time required for a series of operations accompanying the interlayer jump can be shortened.

  Even if the movement of the focal position fails and the movement of the focal position is performed again, the spherical aberration correction means corrects the spherical aberration using a static correction method based on the standard spherical aberration correction amount. Yes.

  Further, after normal focus control by the focus position control means is started, the spherical aberration detection means outputs the correct spherical aberration detection signal based on the spherical aberration actually detected in the multilayer optical disc. Therefore, the spherical aberration correcting means can dynamically correct the spherical aberration of the condensing optical system based on the spherical aberration detection signal corresponding to the situation of each of the multilayer optical discs.

  In the spherical aberration correction method according to the present invention, the focal position of a minute spot formed by converging a light beam on the multilayer optical disc through a condensing optical system is changed from the first recording layer to the second recording layer. When performing an interlayer jump to change to a layer, a method for correcting spherical aberration caused by at least one of the condensing optical system or the multilayer optical disc, the focal position of the minute spot is changed from the first recording layer to the second recording layer. After moving to the recording layer, a static correction method based on a standard correction amount set in advance corresponding to the second recording layer is executed until the focal position of the minute spot is normally controlled. After the focal position is normally controlled, a dynamic correction method based on the spherical aberration detection signal is executed.

  According to this method, the static correction method based on the standard spherical aberration correction amount is used even when the correct spherical aberration is not detected before normal focus control is performed at the time of interlayer jump. Start correction of spherical aberration. Therefore, correction of spherical aberration of the condensing optical system can be started without waiting for normal operation of focus control.

  Therefore, as compared with the case where the correction of the spherical aberration is started after confirming the normal operation of the focus control, a series of operations associated with the interlayer jump is required as much as the movement of the focal position and the correction of the spherical aberration are performed in parallel. You can save time.

  Even if the movement of the focal position fails and the movement of the focal position is performed again, the spherical aberration can be corrected in parallel using the static correction method based on the standard spherical aberration correction amount. The time to redo the movement of the position does not cause a delay in the spherical aberration correction completion time.

  Furthermore, after normal focus control is started, dynamic spherical aberration correction based on the spherical aberration actually detected in the multilayer optical disc is performed. That is, by this method, the spherical aberration of the condensing optical system can be dynamically corrected based on the spherical aberration detection signal corresponding to the situation of each of the multilayer optical discs. Further, since spherical aberration is corrected to some extent by static correction before starting dynamic correction of spherical aberration, the dynamic correction can be finely corrected.

  As described above, according to the present invention, the time required for the movement of the focal position and the correction of the spherical aberration of the condensing optical system is not wasted at all, and the time can be shortened as compared with the prior art.

A feature of the present invention is that when performing an interlayer jump using a spherical aberration detector that can accurately detect spherical aberration only when the focus control is properly performed, the spherical aberration until the timing when the focus control is normally performed. Instead of waiting for the start of correction, the control means determines that it has reached a timing at which the movement of the focal position will be completed when a predetermined time preset in the control means has elapsed, and starts correcting spherical aberration. There is in point to do. Details will be described below.
[First embodiment]
<Outline of First Embodiment>
The optical disc apparatus of the present embodiment collects a light beam as a minute spot on a multilayer optical disc, and is a lens that is a component of a condensing optical system that collects the light beam when recording or reproducing information on the multilayer optical disc However, if the movement of the focal position of the micro spot is completed and the focus control is operating normally by the time when the movement for correcting the spherical aberration will be completed, the movement of the focal position accompanying the interlayer jump or This was devised from the point of not causing any inconvenience to the spherical aberration correction operation. That is, the correction of the spherical aberration is started at the timing at which the movement of the focal position will be completed after the movement of the focal position accompanying the interlayer jump and before confirming the normal operation of the focus control.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 4 as follows.

<About the block diagram of the first embodiment>
FIG. 1 shows a configuration example of the optical disc apparatus according to the present embodiment. The multilayer optical disc 1 is an optical disc composed of a plurality of recording layers, and is loaded into a spindle motor 2 and rotates.

  The optical pickup 3 records or reproduces information by irradiating the multilayer optical disk 1 with laser beam light (hereinafter simply referred to as laser light). The optical pickup 3 includes a semiconductor laser element 4 as a light source, a hologram element 5, a collimator lens 6, a rising mirror 7, a first lens 8, a second lens 9, and a first lens driving element 10 (condensing optical system driving means). ), A focus driving element 11 (condensing optical system driving means), a tracking driving element (not shown), a light receiving element 12, and the like.

  Next, as a control system of the optical pickup 3, the configuration of a focus control system and a spherical aberration control system related to the present invention will be described. The focus control system includes a servo error detection unit 13 (focus position control unit) and a focus drive control unit 14 (focus position control unit) which will be described later. The spherical aberration control system includes a spherical aberration detector 15 (spherical aberration detector) and a spherical aberration drive controller 16 (spherical aberration detector), which will be described later. A command from the controller unit 17 (control means) is input to the focus drive control unit 14 and the spherical aberration drive control unit 16.

  The operation of the optical pickup 3 is as follows. First, laser light emitted from the semiconductor laser element 4 passes through the hologram element 5 and then becomes parallel light by the collimator lens 6. The optical path of the laser light that has become parallel light is changed by the rising mirror 7 in the direction of the multilayer optical disc 1. Then, the laser light is collected by an objective lens composed of two lenses, the first lens 8 and the second lens 9, and is focused on the multilayer optical disc 1 to form a minute spot. Note that the spherical aberration can be corrected by changing the distance between the first lens 8 and the second lens 9. The first lens driving element 10 is provided for correcting the spherical aberration, and includes a DC motor, a stepping motor, a gear, and the like. The first lens driving element 10 drives the first lens 8 based on a signal from the spherical aberration drive control unit 16 to change the interval between the first lens 8 and the second lens 9. Further, the focus drive element 11 changes the distance between the second lens 9 and the multilayer optical disc 1 by driving the second lens 9 based on a signal from the focus drive control unit 14, and changes the focal position of the minute spot. The desired recording layer on the multilayer optical disc 1 is matched.

  In this way, the laser beam focused on the desired recording layer of the multilayer optical disc 1 is reflected by the recording layer. The reflected light travels in the reverse direction on the optical path and enters the hologram element 5. For example, a pattern as described in Patent Document 1 described above is formed on the hologram element 5. The reflected light is diffracted by the hologram element 5 and received by the light receiving element 12. The light receiving element 12 photoelectrically converts the received reflected light and outputs information on the recording layer of the multilayer optical disc 1 as a reproduction signal. The light receiving element 12 outputs the detected reproduction signal to the servo error detection unit 13 and the spherical aberration detection unit 15.

  The servo error detection unit 13 performs an operation on the input from the light receiving element 12 and detects a focus error signal by, for example, a knife edge method or an astigmatism method, while, for example, by a push-pull method or a phase difference method. A tracking error signal is detected. The focus error signal detected by the servo error detector 13 is output to the focus drive controller 14, and phase compensation is performed by the focus drive controller 14. The focus drive control unit 14 drives the focus drive element 11 with the phase-compensated focus error signal, thereby performing focus control so that the focal position of the minute spot matches the desired recording layer. Similarly, the tracking error signal detected by the servo error detector 13 is output to a tracking drive controller (not shown). A tracking drive control unit (not shown) performs tracking control so that the focal point of the laser beam is positioned on a desired track of a desired recording layer on the multilayer optical disc 1 after performing phase compensation.

  The spherical aberration detector 15 receives the reproduction signal output from the light receiving element 12. The spherical aberration detection unit 15 performs the same calculation as the detection method of the spherical aberration detection signal described in Patent Document 1, detects the spherical aberration detection signal, and outputs it to the spherical aberration drive control unit 16. The spherical aberration drive control unit 16 receives the spherical aberration detection signal and drives the first lens driving element 10 to correct the spherical aberration.

  The controller unit 17 is an interlayer jump that moves the focal position of a minute spot between a plurality of recording layers (the appearance of the first and second recording layers suddenly) (forget the definition of terms used in the claims) In the case of the absence, an interlayer jump command is output to the focus drive control unit 14 and a spherical aberration correction command corresponding to the interlayer jump is output to the spherical aberration drive control unit 16. The servo error detection unit 13 detects success / failure of the interlayer jump and outputs the success / failure information to the controller unit 17. When the controller unit 17 determines that the interlayer jump has failed based on the success / failure information (described in consideration of another expression of the method claims), the controller unit 17 outputs a servo redraw command to the focus drive control unit 14. Upon receiving the interlayer jump command or the servo redraw command, the focus drive control unit 14 outputs a focus control OK signal indicating whether the focus control is normally performed to the spherical aberration drive control unit 16. Upon receiving the spherical aberration correction command, the spherical aberration drive control unit 16 performs static correction with a predetermined value based on the focus control OK signal received from the focus drive control unit 14 when correcting the spherical aberration during the interlayer jump. Switching between correction and dynamic correction based on the spherical aberration detection signal received from the spherical aberration detector 15 is performed. This switching between static correction and dynamic correction will be described in detail later.

  Note that the calculation method used by the spherical aberration detector 15 to detect the spherical aberration detection signal is not limited to the calculation method described in Patent Document 1.

<About the flowchart in the first embodiment>
Next, the operation of the optical disc apparatus according to the present embodiment will be described in detail with reference to the flowchart shown in FIG. 2 regarding the interlayer jump when the controller unit 17 outputs the interlayer jump command and the correction of the spherical aberration accompanying the interlayer jump. . Note that, among the plurality of recording layers of the multilayer optical disc 1, attention is paid to two recording layers that are targets of interlayer jump, and these will be referred to as a first recording layer and a second recording layer, respectively.

  First, the controller unit 17 outputs an interlayer jump command to the focus drive control unit 14 and the spherical aberration drive control unit 16 in order to move the focal position from the first recording layer to the second recording layer (step 1). Hereafter referred to as S1).

  Next, when receiving the interlayer jump command, the focus drive control unit 14 stops the focus control as preparation work for the interlayer jump (S2).

  Next, the focus drive control unit 14 outputs an acceleration pulse (kick pulse) KP for starting the movement of the focal position to the focus drive element 11 (S3).

  Next, the focus drive control unit 14 outputs a deceleration pulse (brake pulse) BP to the focus drive element 11 when the focus position moves to the vicinity of the second recording layer, and moves the second lens 9. Stop at an appropriate position (S4).

  After S4, resumption of focus control (S5 below) and correction of spherical aberration accompanying interlayer jump (S8 below) are started at the same time. First, the flow of focus control processing will be described first, A flow of processing relating to a correction operation for spherical aberration accompanying jumping will be described.

  Next, after completing the output of the deceleration pulse BP, the focus drive control unit 14 resumes the focus control (S5).

  Next, the focus drive control unit 14 determines whether the focus control is normally performed after the focus control is resumed (S6). When the amount of reflected light from the recording surface at the interlayer jump destination exceeds a predetermined level, it is determined that focus control is normally performed, and a focus control OK signal is output to the spherical aberration drive control unit 16.

  Next, after the focus control is resumed, when the focus drive control unit 14 determines that the focus control is abnormal due to the reason that the amount of reflected light has not reached a predetermined level, the controller unit 17 again returns to the focus position, for example. Is returned to the first recording layer, and an interlayer jump is performed again, or a retry operation is repeated such that the focus control (servo) is pulled back so that the focal position is aligned with the second recording layer of the interlayer jump destination (S7).

  Next, after the output of the deceleration pulse BP in S4 is completed, the spherical aberration drive control unit 16 drives the first lens driving element 10 based on a preset standard spherical aberration correction amount, thereby reducing the spherical aberration statically. Correction operation is started (S8).

  It should be noted that since the normal focus control is not yet performed at the start of the focus control in S5, a spherical aberration detection signal that accurately reflects the spherical aberration cannot be detected. However, since the controller unit 17 knows in advance the movement direction and the movement amount for substantially adjusting the focal position to the recording surface of the interlayer jump destination, how much the first lens 8 is moved in which direction and how much. The first lens driving element 10 can be instructed. For this reason, the driving of the first lens driving element 10 can be started even at the start time of the focus control in S5 where normal focus control is not performed.

  Next, a flow of processing relating to a correction operation for spherical aberration accompanying interlayer jump will be described.

  After S4, the spherical aberration drive control unit 16 waits for a focus control OK signal from the focus drive control unit 14. When the focus control OK signal is received, the spherical aberration drive control unit 16 changes the spherical aberration correction method from static correction based on a predetermined value (standard spherical aberration correction amount) to a spherical aberration detection signal. Then, the dynamic correction is switched to drive the first lens 8 (S9).

  In this way, the spherical aberration correction method is switched from the static correction method to the dynamic correction method when the focus control is normal, the spherical aberration detection signal output from the spherical aberration detector 15 is the actual one. This is because the signal reflects the spherical aberration, so that appropriate dynamic correction of the spherical aberration can be performed based on this spherical aberration detection signal.

  Finally, the spherical aberration drive controller 16 determines whether the spherical aberration detection signal output from the spherical aberration detector 15 is within a predetermined level. When the signal is within a predetermined level, the correction of spherical aberration accompanying the interlayer jump is completed. Accordingly, a series of operations accompanying the interlayer jump is completed (S10).

  For convenience of explanation, in S10, when a predetermined level is set for the spherical aberration detection signal and the detected spherical aberration is within this predetermined level, correction of the spherical aberration accompanying the interlayer jump is completed. It is described. However, it is needless to say that the spherical aberration correction operation is not always terminated and the spherical aberration correction is always continued as long as it is within a predetermined level. Alternatively, a configuration may be adopted in which dynamic correction of spherical aberration is performed again when the spherical aberration detection signal exceeds a predetermined level even after completion of the correction operation of spherical aberration associated with the interlayer jump. With these configurations, it is possible to always perform accurate correction for spherical aberration caused by the difference in thickness of the cover layer and the thickness of the recording layers in the plane of the multilayer optical disc 1.

  Further, when the spherical aberration drive control unit 16 starts the correction operation of the spherical aberration by driving the first lens driving element 10 (start of S8), the controller unit 17 issues an interlayer jump command to the spherical aberration drive control unit 16. However, it is more preferable that the focus driving control unit 14 outputs the deceleration pulse BP and stops the movement of the second lens 9 at an appropriate position (S4). . Because, firstly, this timing is close to the time when the focal position of the minute spot finishes moving from the first recording layer to the second recording layer, so it is not wasted even if the spherical aberration correction operation is performed. It is. Second, at this timing, spherical aberration can be dynamically corrected using the spherical aberration detection signal, and a retry operation is performed because focus control has failed during the dynamic correction. This is because the total processing time is considered to be the best point.

<Focal position shift and spherical aberration correction timing associated with interlayer jump>
The time required for the processing from S1 to S6, that is, the time required to move the focus position and determine whether the focus control is normally performed is usually about several milliseconds to several tens of milliseconds.

  On the other hand, it is necessary to finely adjust the distance between the first lens 8 and the second lens 9 to correct the spherical aberration, and the first lens driving element 10 is set using a DC motor or a stepping motor as a power source. It is necessary to drive in small increments. Furthermore, since the first lens 8 is heavier than the second lens 9, it takes longer than the movement of the second lens 9. Usually, it takes several tens of milliseconds to several hundred milliseconds to move the first lens 8 to a position corresponding to a desired recording layer.

  As described above, the time required for moving the second lens 9 for moving the focal position is very short as compared with the time required for moving the first lens 8 for correcting the spherical aberration. For this reason, even if the movement of the focal position (interlayer jump) fails, there is a time margin for retrying the movement of the focal position a plurality of times within the time required for the movement of the first lens 8 thereafter.

  However, conventionally, after performing an interlayer jump, it has been usual to correct spherical aberration after confirming that focus control is normal. That is, if the interlayer jump fails, it is necessary to perform a retry operation for moving the focal position, but the correction of spherical aberration is not started until the retry operation is completed and the focus control is confirmed to be normal.

  For this reason, the time required for completing a series of operations of interlayer jumps is not constant, and when the above retry operation occurs, the time required for a series of operations required for interlayer jumps is increased accordingly.

  However, if the movement of the focal position is completed and the focus control is operating normally by the time when the first lens 8 will complete the movement for correcting the spherical aberration, the focal position associated with the interlayer jump is changed. There is no inconvenience for movement and spherical aberration correction.

  Therefore, the optical disk apparatus according to the present embodiment starts correcting the spherical aberration associated with the interlayer jump after confirming the normal operation of the focus control after moving the focal position associated with the interlayer jump.

  For this reason, the time required for a series of operations for moving the focal position and correcting the spherical aberration associated with the interlayer jump does not need to consider the retry operation time due to the failure of the focal position movement, and is merely an acceleration for moving the focal position. The sum of the time required to output the pulse KP and the deceleration pulse BP and the time required to move the first lens 8 can be obtained. Normally, the time required for the movement of the first lens 8 is longer than the time required for several retry operations, and thus is constant without fluctuation.

<Interlayer jump timing chart>
The timing chart shown in FIG. 3 is shown for a series of operations from when the controller unit 17 outputs an interlayer jump command until the focal position is controlled in a desired recording layer and until the correction of spherical aberration accompanying the interlayer jump is completed. The details will be described.

  The timing chart of FIG. 3 shows that the controller unit 17 has completed the output of the interlayer jump command at the time T1. Upon receiving the interlayer jump command from the controller unit 17, the focus drive control unit 14 first stops focus control at time T1 in order to move the focus position from the first recording layer to the second recording layer. Simultaneously, an acceleration pulse KP is output, and the movement of the second lens 9 is started by the focus driving element 11.

  When the focus position moves to the vicinity of the second recording layer, the focus drive controller 14 outputs a deceleration pulse BP. At time T2, the focus drive control unit 14 completes the output of the deceleration pulse BP and resumes focus control. That is, the focus drive control unit 14 performs focus position control by driving and controlling the focus drive element 11 in accordance with a focus error signal that is an input signal from the servo error detection unit 13. Further, at time T2, the spherical aberration drive control unit 16 drives the first lens drive element 10 to start correcting the spherical aberration associated with the interlayer jump.

  At the time T2, the focus drive control unit 14 is in a state where focus control is not normally performed. Therefore, when driving the first lens driving element 10, the spherical aberration drive control unit 16 does not perform the operation according to the spherical aberration detection signal detected by the spherical aberration detection unit 15, but sets a second preset value. The drive of the first lens 8 is started with a standard spherical aberration correction amount (standard spherical aberration correction amount) in the recording layer as a target value.

  This standard spherical aberration correction amount is set in advance in the spherical aberration drive control unit 16 based on the standard optical disc standard, or the controller unit 17 records each recording when the multilayer optical disc 1 is loaded into the optical disc apparatus. It is preferable to perform an interlayer jump to the layer so that the spherical aberration drive controller 16 learns the spherical aberration correction amount specific to each recording layer in advance.

  At time T3, the focus drive control unit 14 determines that the focus control is normally performed when the amount of light reflected from the multilayer optical disc 1 has reached a predetermined level. This determination may be performed when the focus control is started at time T2, but more accurate determination can be made after a predetermined time has elapsed after the focus control has started and the focus control has settled. ,preferable. If it is determined at time T3 that the focus control is normally performed, the spherical aberration drive control unit 16 indicates that the spherical aberration detection signal output from the spherical aberration detection unit 15 also reflects the correct spherical aberration amount. I can judge. Accordingly, the spherical aberration drive control unit 16 outputs the control for driving the first lens driving element 10 from the spherical aberration detection unit 15 at the time T3 from the static correction operation using the standard spherical aberration correction amount. Switching to a dynamic correction operation based on the actual spherical aberration detection signal.

  At time T4, the spherical aberration drive control unit 16 determines that the correction of the spherical aberration due to the interlayer jump is completed when the spherical aberration detection signal is within a predetermined range, and stops driving the first lens 8. . Thereby, the movement of the focal position and the correction of the spherical aberration, which are a series of operations accompanying the interlayer jump, are completed. Here, in the interlayer jump by the above method, the time required from the output of the interlayer jump command to the completion of a series of operations is T4−T1, and the time required for T1 as the origin is T4.

<Timing chart when interlayer jump fails>
Next, the operation when the interlayer jump fails will be described in detail using the timing chart shown in FIG.

  In the timing chart shown in FIG. 4, similarly to the timing chart when the interlayer jump is successful shown in FIG. 3, the controller unit 17 completes the output of the interlayer jump command at time T1. At the same time, the focus drive controller 14 stops focus control and outputs an acceleration pulse KP.

  At time T2, the focus drive control unit 14 completes the output of the deceleration pulse BP and resumes focus control. At the same time, the spherical aberration drive control unit 16 drives the first lens drive element 10 to start correcting spherical aberration associated with the interlayer jump.

  However, at time T3, the focus drive control unit 14 determines that the focus control is not normally performed because the amount of reflected light from the multilayer optical disc 1 has not reached a predetermined level.

  At time T <b> 3 ′, the controller unit 17 again outputs an interlayer jump command (jump retry command) to the focus drive control unit 14. At time T3 ′, since the spherical aberration drive control unit 16 has already started the spherical aberration correction operation, this interlayer jump command (jump retry command) is ignored and the standard spherical aberration correction amount is set as the target value. The driving of the first lens 8 is continued. On the other hand, the focus drive control unit 14 once returns the focal position to the first recording layer, and then outputs the acceleration pulse KP and the deceleration pulse BP again, so that the desired recording layer at the interlayer jump destination has the focal position. Control to meet. Note that when the focal position is once returned to the first recording layer, the controller unit 17 issues an interlayer jump command, and the focus drive control unit 14 outputs an acceleration pulse KP and a deceleration pulse BP. Is not shown in the timing chart.

  Then, after performing the retry operation of the movement of the focal position associated with the interlayer jump, the focus drive control unit 14 determines again whether the amount of reflected light from the multilayer optical disc 1 has reached a predetermined level at time T3 ″. 4 shows a case where it is determined that the focus control is operating normally at time T3 ″. After this time T3 ″, since the focus control is normally performed, the spherical aberration detector 15 correctly detects the spherical aberration and outputs an appropriate spherical aberration detection signal. Therefore, the spherical aberration drive controller 16 switches the correction control method of the spherical aberration from the static control to the dynamic control so that the first lens 8 is driven according to the spherical aberration detection signal.

  After these operations, the correction of spherical aberration is completed at time T4, and a series of operations of focal point movement and spherical aberration correction accompanying the interlayer jump is completed.

  Here, the time required to drive the second lens 9 to move the focal position is usually very large compared to the time required to drive the first lens 8 to correct the spherical aberration. It is a short time. Therefore, the focus drive control unit 14 can complete the retry operation of the focus position control while the spherical aberration drive control unit 16 is driving the first lens 8. Therefore, even if the movement of the focal position fails and the retry operation is performed, the total time required for the interlayer jump operation is the same as that in the timing chart when the interlayer jump is successful shown in FIG. That is, the time required to complete a series of operations is (T4-T1), and when T1 is the origin, the time required is T4.

<Effect in the first embodiment>
As described above, the optical disk apparatus according to the present embodiment has an effect that even if the interlayer jump fails, the time required for a series of operations accompanying the interlayer jump does not increase and is constant.

  Furthermore, since it can be confirmed that the focus control can be normally performed, the spherical aberration can be corrected based on the spherical aberration detection signal obtained by receiving the reflected light from the multilayer optical disc 1, There is an effect that the spherical aberration can always be corrected optimally for the multilayer optical disc 1.

<Supplementary items>
In the present embodiment, as a spherical aberration correction method, correction is performed by adjusting the distance between the first lens 8 and the second lens 9. However, the spherical aberration may be corrected by using one objective lens and inserting an optical component such as a liquid crystal element that can correct the spherical aberration in the optical path. In this case, the first lens 8 is not driven, but the voltage applied to the optical element such as a liquid crystal element is controlled to correct the spherical aberration. The same effect can be obtained by setting the timing to start the driving.
[Second Embodiment]
<Outline of Second Embodiment>
It is desirable to correct the spherical aberration based on the detected spherical aberration detection signal as much as possible. Therefore, in this embodiment, instead of performing a static spherical aberration correction operation using a preset standard spherical aberration correction amount, a dynamic spherical aberration correction operation is performed using a spherical aberration detection signal from the beginning. Do. For that purpose, since it is necessary to wait for a predetermined time until the focus control becomes normal, a waiting time is provided. However, when the movement of the focal position using the waiting time fails, the completion of the retry operation cannot be waited, and thus the spherical aberration static correction operation is started using the standard spherical aberration correction amount. That is, after the focus position of the minute spot is moved from the first recording layer to the second recording layer, after starting the success / failure confirmation of whether the focus control is successful, the normal operation of the focus control is confirmed. Until, a static correction method based on a standard correction amount set in advance corresponding to the second recording layer is executed, and after confirming the normal operation of the focus control, the dynamic correction based on the spherical aberration detection signal is performed. Correct correction method.

  A second embodiment of the present invention will be described below with reference to FIGS.

  Note that the configuration of the optical disc apparatus in the present embodiment is the same as that in the first embodiment, and thus the description of the configuration is omitted.

<About the flowchart in the second embodiment>
Hereinafter, a series of operations of the interlayer jump of the optical disc apparatus according to the present embodiment will be described in detail with reference to the flowchart shown in FIG.

  First, the controller unit 17 outputs an interlayer jump command to the focus drive control unit 14 and the spherical aberration drive control unit 16 so as to move the focal position from the first recording layer to the second recording layer (S101).

  Upon receiving the interlayer jump command, the focus drive control unit 14 stops the focus control in order to move the focus position from the first recording layer to the second recording layer (S102).

  Subsequently, the focus drive control unit 14 outputs an acceleration pulse KP for moving the focus position with respect to the focus drive element 11 (S103).

  Then, the focus drive control unit 14 outputs the deceleration pulse BP when the focal position moves to the vicinity of the second recording layer, and stops the second lens 9 (step S104).

  The focus drive control unit 14 resumes the focus control after the completion of the output of the deceleration pulse BP (S105).

  Then, the focus drive control unit 14 waits for a time required to start the focus control and operate normally (step S106). The predetermined time may be about several milliseconds.

  After waiting for the predetermined time, the focus drive control unit 14 determines whether the focus control is normally performed (S107).

  Here, when the focus control is not normally performed, the spherical aberration drive control unit 16 cannot perform the correction operation of the spherical aberration based on the spherical aberration detection signal from the spherical aberration detection unit 15, so the standard spherical aberration correction amount is set. Based on this, the driving of the first lens driving element is started (S108).

  Further, the focus drive control unit 14 performs a retry operation for moving the focal position (S109).

  After the retry operation, the focus drive control unit 14 determines again whether the focus control is normally performed (S110). If the focus control is normally performed, the process proceeds to the next S111. If the focus control is not normally performed, the process returns to the previous S109 to repeat the retry operation.

  When it is determined in S107 or S110 that the focus control is operating normally, the spherical aberration drive control unit 16 can perform a spherical aberration correction operation based on the spherical aberration detection signal from the spherical aberration detection unit 15. Therefore, the spherical aberration drive control unit 16 switches the spherical aberration correction control method from static control to dynamic control so that the first lens 8 is driven in accordance with the spherical aberration detection signal (S111).

  The spherical aberration drive controller 16 determines whether the spherical aberration detection signal from the spherical aberration detector 15 is within a predetermined level. If not within the predetermined level, the spherical aberration drive control unit 16 returns to the previous S111 and repeats the spherical aberration correction operation based on the spherical aberration detection signal. If it is within the predetermined level, the spherical aberration drive control unit 16 ends the correction operation of the spherical aberration accompanying the interlayer jump (S112).

  Here, unlike the first embodiment, the spherical aberration drive control unit 16 immediately starts the spherical aberration correction operation targeting the standard spherical aberration correction amount immediately after the output of the deceleration pulse BP, unlike the case of the first embodiment. Instead, it starts after a predetermined time. For this reason, when it can be determined that the focus control is normally performed after a predetermined time has elapsed, the standard spherical aberration correction amount is not used and the movement is performed according to the spherical aberration detection signal from the spherical aberration detector 15 from the beginning. There is an effect that the spherical aberration can be corrected.

  On the other hand, if the focus control has not been performed normally after the predetermined time has elapsed, as in the case of the first embodiment, the static aberration of the spherical aberration is determined based on the preset standard spherical aberration correction amount. Start correction.

<Interlayer jump timing chart>
6 and 7 are timing charts illustrating a series of operations for moving the focal position and correcting the spherical aberration accompanying the interlayer jump in the present embodiment.

  The timing chart shown in FIG. 6 indicates that the controller unit 17 has completed the output of the interlayer jump command from the first recording layer to the second recording layer at time T1. Upon receiving the interlayer jump command from the controller unit 17, the focus drive control unit 14 first stops the focus control and moves the acceleration pulse to the focus drive element 11 in order to move the focus position from the first recording layer to the second recording layer. KP is output and the movement of the second lens 9 is started.

  Then, the focus drive control unit 14 outputs the deceleration pulse BP when the focal position moves near the second recording layer.

  At time T2 when the output of the deceleration pulse BP is completed, the focus drive control unit 14 resumes focus control. That is, the focus position control is performed by controlling the drive of the focus drive element 11 in accordance with the focus error signal that is an input from the servo error detector 13.

  At time T3 after a predetermined time (ΔT) has elapsed from time T2, the focus drive control unit 14 determines whether the focus control is normal. At the same time, the spherical aberration drive control unit 16 starts correcting spherical aberration at time T3. At this point, since the focus control is normal, the spherical aberration drive control unit 16 performs dynamic spherical aberration correction from the beginning according to the spherical aberration detection signal.

  Then, at time T4 ', the spherical aberration drive control unit 16 ends the series of operations, assuming that the spherical aberration is within a predetermined level.

  Here, according to the above method, the time required from the output of the interlayer jump command to the completion of a series of operations is T4 ′ longer than the first embodiment by ΔT, where T1 is the origin.

  This ΔT is a very short time (several milliseconds) compared to the time required to correct the spherical aberration (several tens of milliseconds to several hundreds of milliseconds). While the time required for the interlayer jump increases only by a short time, the spherical aberration correction operation has an effect that dynamic spherical aberration correction can be performed from the beginning based on the spherical aberration detection signal.

<Timing chart when interlayer jump fails>
FIG. 7 shows a timing chart of the operation when the interlayer jump fails.

  In the timing chart of FIG. 7, as in the timing chart of FIG. 6, the controller unit 17 completes the output of the interlayer jump command at time T1.

  At time T2, when the output of the deceleration pulse from the focus drive control unit 14 is completed, the spherical aberration drive control unit 16 starts driving the first lens 8 for spherical aberration correction.

  Then, at time T3 after the lapse of ΔT which is a predetermined time, the spherical aberration drive control unit 16 starts correcting the spherical aberration. However, since the focus control is not normally performed this time, dynamic spherical aberration correction cannot be performed yet. Accordingly, the driving of the first lens 8 is started with the standard spherical aberration correction amount as the target value for the second recording layer.

  At time T3, since the amount of reflected light from the multilayer optical disc 1 has not reached the predetermined level, it is determined that the focus control is not operating normally. Therefore, the controller unit 17 again performs an interlayer jump command (jump retry) at time T3 ′. Command).

  Then, the focus drive control unit 14 outputs the acceleration pulse KP and the deceleration pulse BP again, and performs control so that the desired recording layer has the focal position. Then, after performing the retry operation, it is determined again at time T3 ″ whether the amount of reflected light from the multilayer optical disc 1 has reached a predetermined level.

  The timing chart of FIG. 7 shows a case where it is determined at time T3 ″ that the post-retry focus control is operating normally. After this time T3 ″, the focus control is normal and spherical aberration is detected. The detection unit 15 normally detects spherical aberration and outputs a spherical aberration detection signal. Accordingly, the spherical aberration drive control unit 16 switches the driving of the first lens 8 from static correction using the standard spherical aberration correction amount to dynamic correction performed based on this spherical aberration detection signal.

  Thereafter, at time T4 ', the spherical aberration drive control unit 16 determines that the spherical aberration detection signal has fallen within a predetermined level, and completes correction of the spherical aberration accompanying the interlayer jump. Thus, a series of operations accompanying the interlayer jump is completed.

  Thus, the focus position movement retry operation by the focus drive control unit 14 is performed while the spherical aberration drive control unit 16 corrects the spherical aberration associated with the interlayer jump. Normally, the time required for the retry operation is very short (several milliseconds to several tens of milliseconds), and can be completed during the spherical aberration correction operation. Therefore, even if the movement of the focal position fails and the retry operation is performed, the time required for the series of operations of the interlayer jump actually takes T4 as the origin, as in the timing chart shown in FIG. 'Become.

<Effect in the second embodiment>
As described above, the optical disk apparatus according to the present embodiment has an effect that the total time required for a series of operations of the interlayer jump does not increase even if the movement of the focal position due to the interlayer jump fails. .

  Furthermore, since it can be confirmed that the focus control can be normally performed, the spherical aberration can be corrected based on the spherical aberration detection signal obtained by receiving the reflected light from the multilayer optical disc 1, so that the spherical aberration can always be corrected. There is an effect that spherical aberration can be corrected optimally for the multilayer optical disc 1.

<Supplementary explanation>
In this embodiment, as in the case of the first embodiment, the spherical aberration is corrected by adjusting the distance between the first lens 8 and the second lens 9, but the number of objective lenses is reduced to one. Thus, the spherical aberration may be corrected by inserting an optical component such as a liquid crystal element that can correct the spherical aberration in the optical path. In this case, the first lens 8 is not driven, but the voltage applied to the optical element such as a liquid crystal element is controlled to correct the spherical aberration. Similar to the case of the first embodiment, it is possible to obtain the same effect by setting the timing at which the driving of No. 8 is started.

<Effects in Examples>
The optical disk apparatus according to the present embodiment starts correcting the spherical aberration associated with the interlayer jump after confirming the normal operation of the focus control after moving the focal position associated with the interlayer jump.

  For this reason, the time required for a series of operations for moving the focal position and correcting the spherical aberration associated with the interlayer jump does not need to consider the retry operation time due to the failure of the focal position movement, and is merely an acceleration for moving the focal position. The sum of the time required to output the pulse KP and the deceleration pulse BP and the time required to move the first lens 8 can be obtained. Normally, this time does not vary and is constant.

  Therefore, when developing a device equipped with the optical disk device of the present embodiment, the developer may estimate a certain time as the time required for the interlayer jump, and the system is assumed on the assumption that the time required for the interlayer jump varies. This has the effect of eliminating the need for adjustment.

  In addition, there is an effect that the time required for the interlayer jump can be shortened as compared with the case where the correction of the spherical aberration is started after the movement of the focal position is completed.

  Further, since the spherical aberration can be dynamically corrected according to the actual spherical aberration detection signal detected from the reflected light from the multilayer optical disc 1, there is an effect that the spherical aberration can always be accurately corrected.

<Supplementary information regarding the embodiment>
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The optical disc apparatus of the present invention includes a laser light source, a condensing optical system including an objective lens that receives a light beam emitted from the laser light source and converges it onto a small spot on the optical disc, and a light amount received by the light beam reflected by the optical disc. An optical pickup having a photodetector that outputs an electrical signal in response to the optical signal, a spherical aberration detector that detects the spherical aberration of the condensing optical system, and an optical system that corrects the spherical aberration detection signal in response to the detection signal A motor that rotates the optical disc, and a control circuit that receives a signal obtained from the optical pickup and controls and drives the laser light source, the objective lens, the aberration correction optical system, and the motor, An optical disc that records, reproduces, or only reproduces information on a multilayer optical disc having at least a first recording layer and a second recording layer And a change amount of the spherical aberration correction amount is started after the movement of the focal position of the minute spot from the first recording layer to the second recording layer is started. It can also be set as the structure to do.

  In the optical disc apparatus of the present invention, the timing for starting the change of the correction amount of the spherical aberration is before confirming that the focal position of the minute spot has moved from the first recording layer to the second recording layer. It can also be set as the structure characterized by these.

  In the optical disk device of the present invention, when the focal position of the minute spot fails to move from the first recording layer to the second recording layer, the focal position of the minute spot is maintained while the correction amount of the spherical aberration continues. It is also possible to adopt a configuration characterized by redoing the control.

  The optical disc apparatus of the present invention may be configured such that an appropriate detection signal is output as the spherical aberration detection signal when the focal position of the minute spot is controlled by the recording layer.

  In the optical disk apparatus of the present invention, the correction amount of the spherical aberration is a standard first set in advance until it is confirmed that the focal position of the minute spot has moved from the first recording layer to the second recording layer. The correction amount of the second recording layer is set as a target value, and after confirming that the focal position of the minute spot has moved to the second recording layer, the spherical aberration detection signal is set as the target value of the correction amount. It can also be configured.

  The optical disc apparatus according to the present invention realizes a method of accurately correcting spherical aberration when performing an interlayer jump in an optical disc having a plurality of recording layers. Therefore, the present invention can be applied to an apparatus for recording or reproducing an optical disk having a plurality of recording layers, particularly an optical disk recording / reproducing apparatus such as a DVD-ROM, DVD ± R, DVD ± RW, and next-generation DVD.

It is the block diagram which showed the principal part of the optical disk apparatus in this invention. It is a flowchart explaining a series of operation | movement of the interlayer jump in 1st embodiment. It is a timing chart explaining the series of operations of the interlayer jump in the first embodiment. 6 is a timing chart for explaining a retry operation when the movement of the focal position fails in a series of operations of interlayer jump in the first embodiment. It is a flowchart explaining a series of operation | movement of the interlayer jump in 2nd embodiment. It is a timing chart explaining a series of operation | movement of the interlayer jump in 2nd embodiment. 12 is a timing chart for explaining a retry operation when the movement of the focal position fails in a series of operations of interlayer jump in the second embodiment. It is a timing chart explaining a series of operations of the interlayer jump of the optical disc device in the conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multilayer optical disk 2 Spindle motor 3 Optical pick-up 4 Semiconductor laser element 5 Hologram element 6 Collimator lens 7 Raising mirror 8 First lens (Condensing optical system)
9 Second lens (condensing optical system)
10 First lens driving element (condensing optical system driving means)
11 Focus drive element (condensing optical system drive means)
12 Photodetector 13 Servo error detector (focal position control means)
14 Servo error drive controller (focal position control means)
15 Spherical aberration detector (spherical aberration detector)
16 Spherical aberration drive controller (spherical aberration correction means)
17 Controller (control means)

Claims (5)

In an optical disc apparatus for recording or reproducing information on a multilayer optical disc having at least a first recording layer and a second recording layer,
A condensing optical system for converging a light beam to a minute spot on the multilayer optical disc;
A focal position control means for controlling the focal position of the minute spot;
Spherical aberration detection means for detecting spherical aberration caused by at least one of the condensing optical system or the multilayer optical disc and outputting a spherical aberration detection signal;
Spherical aberration correction means for correcting the spherical aberration based on the spherical aberration detection signal;
A condensing optical system driving means for driving the condensing optical system for moving the focal position of the minute spot or correcting the spherical aberration;
A control means for controlling the condensing optical system driving means and the spherical aberration correcting means,
When performing an interlayer jump to change the focal position of the micro spot from the first recording layer to the second recording layer,
In the spherical aberration correction method, it is confirmed that the focus control by the focus position control means is normally performed after the focal position of the minute spot moves from the first recording layer to the second recording layer. Until this is the static correction method based on a standard correction amount set in advance corresponding to the second recording layer, and after confirming the normal operation of the focus control by the focus position control means, the spherical aberration As a dynamic correction method based on the detection signal,
An optical disc apparatus characterized in that the spherical aberration correction means switches a correction method of the spherical aberration.   2. The optical disc apparatus according to claim 1, wherein the spherical aberration correcting unit starts correcting the spherical aberration after the focal position control unit starts moving the focal position of the minute spot.   When the movement of the focal position by the focal position control means fails, the focal position control means performs the movement of the focal position again while the correction of the spherical aberration by the spherical aberration correction means continues. The optical disc apparatus according to claim 2.   The focus position control means issues a drive stop command to the condensing optical system driving means in order to stop the driving of the condensing optical system that is driven for the movement of the focal position by the interlayer jump. 3. The spherical aberration correcting unit starts a static correction method of the spherical aberration in a period until a normal operation of controlling the focal position by the focal position controlling unit is confirmed. Optical disk device. In a spherical aberration correction method executed by an optical disc apparatus that records or reproduces information on a multilayer optical disc including at least a first recording layer and a second recording layer,
When performing an interlayer jump to change the focal position of a minute spot formed by converging a light beam on the multilayer optical disc via a condensing optical system from the first recording layer to the second recording layer,
Regarding a method for correcting spherical aberration caused by at least one of the condensing optical system or the multilayer optical disc, it corresponds to the second recording layer after the interlayer jump until the focal position of the minute spot is normally controlled. A static correction method based on a standard correction amount set in advance is executed, and after the focus position is normally controlled, a dynamic correction method based on the detection signal of the spherical aberration is executed. A method for correcting spherical aberration.

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