JP2009140573A - Optical disk drive and focus jump method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid maladjustment of spherical aberration upon failure of focus jump and prevent a focus servo from becoming unstable. <P>SOLUTION: Before performing focus jump operation that moves a focus of a laser beam from a first recording layer to a second recording layer of an optical disk 3, a spherical aberration correcting amount SA by a spherical aberration correcting mechanism 115 is changed from a first correcting amount SA1 which is suitable for the first recording layer, to a third correcting amount SA2 between the second correcting amount SA4 which is suitable for the second recording layer and the first correcting amount SA1, and after performing focus jump operation, whether or not the focus jump operation succeeds is determined based on a light receiving amount level detected by a light detecting section 130 before and after the focus jump operation, and, when it is determined that the focus jump operation fails, the spherical aberration correcting amount by the spherical aberration correcting mechanism 115 is returned from the third correcting amount SA2 to the first correcting amount SA1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc device and a focus jump method, and more particularly to an optical disc device and a focus jump method for avoiding erroneous spherical aberration adjustment when a focus jump fails.

  An optical disc device is a device for recording information on an optical disc using a laser beam or reproducing recorded information. In this optical disk apparatus, laser light emitted from a light source is collected by an objective lens, spot-irradiated on a recording layer of the optical disk, and reflected light (returned light) of the laser light reflected by the optical disk is received by a light detection unit. Has a pickup. Then, the optical disc apparatus calculates a detection signal of the amount of light received by the light detection unit, generates a servo signal such as a tracking error signal or a focus error signal, and servo-controls the irradiation position of the laser beam spot on the optical disc. Yes.

  Optical disks handled by such an optical disk device include, for example, high density optical disks such as CD (Compact Disk), DVD (Digital Versatile Disc), and Blu-ray Disc (hereinafter referred to as “BD”). In recent years, multilayer disks having a plurality of recording layers have been used to store more information. When recording / reproducing information on such a multi-layer disc, it is necessary to switch the information recording / reproducing position by the optical pickup among a plurality of recording layers. For example, in the case of a two-layer disc, when the recording / reproducing position is switched from the first recording layer (current recording layer) to the second recording layer (target recording layer), the focal position of the objective lens included in the optical pickup (that is, , A laser beam spot position) is moved from the first recording layer to the second recording layer.

  By the way, the problem of spherical aberration is known as a problem that may occur during recording / reproduction of an optical disc. The spherical aberration is mainly caused by a thickness error of a light transmission layer (cover layer, intermediate layer, etc.) of the optical disc, and distorts the return light reflected by the optical disc, so that information cannot be correctly recorded and reproduced. Since this spherical aberration increases as the numerical aperture NA of the objective lens increases, particularly when an objective lens having a high numerical aperture NA (for example, NA = 0.8 or more) is used to cope with a high-density optical disk. Increases the influence of spherical aberration. Therefore, in a high-density multilayer disc, distortion occurs in the focus error signal due to the influence of spherical aberration, and thus there is a problem that stable focus jump cannot be realized.

  In order to cope with such a problem, a recording layer (target recording layer) to which the focus jump is performed in advance before the focus jump is performed using a spherical aberration correction mechanism including an optical unit such as an expander lens or a liquid crystal element including two lens groups. ), There is a method of correcting spherical aberration. However, this method has a problem in that the current focus servo may be lost as a result of correcting the spherical aberration so as to match the target recording layer before the focus jump.

  Therefore, in order to solve such a problem, for example, Patent Document 1 discloses that an optical unit for correcting spherical aberration is placed in advance on the target recording layer as much as possible within the range in which the current focus servo is not removed before the focus jump. There has been proposed a method of maintaining a state in which spherical aberration is corrected. In the method of Patent Document 1, before the focus jump, the correction state of the optical unit for correcting spherical aberration is set to an intermediate correction state between the correction state Sc optimal for the current recording layer and the correction state Sd optimal for the target recording layer. After moving to Sd ′ and performing a focus jump, the correction state of the optical unit is moved from an intermediate correction state Sd ′ to an optimal correction state Sd for the target recording layer.

Japanese Patent Laid-Open No. 2003-16660

  However, in the actual focus jump, the focus position does not reach the target recording layer even if the focus jump is performed due to the fluctuation of the surface of the optical disk or the variation of the biaxial sensitivity. There is a failure). Furthermore, since the tracking servo is in a state where the tracking servo is lowered during the focus jump (tracking servo OFF state), it is determined whether or not the recording layer focused after the focus jump is the same recording layer as before the focus jump, It is not easy to determine the success or failure of a focus jump.

  However, in the method described in Patent Document 1, the correction state of the optical unit for correcting spherical aberration is changed from the intermediate correction state Sd ′ to the target recording layer without taking any action even when the focus jump fails. It will change to the optimal correction state Sd. As a result, there is a problem that the spherical servo is erroneously adjusted such that the optimum correction state Sd is applied to the target recording layer with respect to the current recording layer, and the focus servo becomes unstable.

  As a method to avoid the focus servo becoming unstable when the focus jump fails, the focus servo is turned off before the focus jump (focus servo OFF), and the focus servo is adjusted to the target recording layer after the focus jump. A method of re-calling can be considered. However, this method is not practical because it takes a very long time to apply the focus servo again. Therefore, there is a demand for a method that can prevent the focus servo from becoming unstable when the focus jump is executed with the focus servo applied.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to avoid erroneous adjustment of spherical aberration at the time of focus jump failure and to make the focus servo unstable. It is an object of the present invention to provide a new and improved optical disc apparatus and focus jump method which can be prevented.

  In order to solve the above-described problems, according to an aspect of the present invention, there is provided an optical disc apparatus for recording or reproducing information on an optical disc having a plurality of recording layers: recording a laser beam from a light source on the optical disc. An objective lens for focusing on the layer; an actuator for moving the objective lens so that the focal point of the laser beam is aligned with the recording layer of the optical disc; and a light detection unit that receives the reflected light of the laser beam on the optical disc A spherical aberration correction mechanism for correcting spherical aberration, provided on an optical path between the light source and the objective lens, and a control unit for controlling a spherical aberration correction amount by the spherical aberration correction mechanism. The control unit performs the focus jump operation for moving the focal point of the laser light from the first recording layer to the second recording layer of the optical disc. The spherical aberration correction amount by the surface aberration correction mechanism is changed from the first correction amount suitable for the first recording layer to the second correction amount suitable for the second recording layer and the first correction amount. After the focus jump operation is performed, the success or failure of the focus jump operation is determined based on the received light level detected by the light detection unit before and after the focus jump operation. When it is determined that the focus jump operation has failed, a spherical aberration correction amount by the spherical aberration correction mechanism is returned from the third correction amount to the first correction amount. The

  When the control unit determines that the focus jump operation is successful, the control unit determines a spherical aberration correction amount by the spherical aberration correction mechanism from the third correction amount, the third correction amount, and the second correction amount. And the fourth correction amount between the first correction amount and the fourth correction amount before and after the change from the third correction amount to the fourth correction amount. When it is determined whether there is a malfunction related to the focus, the spherical aberration correction amount by the spherical aberration correction mechanism is changed from the fourth correction amount to the first correction amount or the third correction amount. You may make it return to.

  A focus servo mechanism for controlling the actuator based on a signal representing the amount of received light detected by the light detection unit is further provided, and the fourth correction amount is a focus on the first recording layer by the focus servo mechanism. The spherical aberration correction amount may be set within a range where the servo does not deviate.

  A focus servo mechanism for controlling the actuator based on a signal representing the amount of received light detected by the light detection unit is further provided, and the third correction amount is a focus on the second recording layer by the focus servo mechanism. The spherical aberration correction amount may be set within a range where the servo does not deviate.

  A focus servo mechanism for controlling the actuator based on a signal indicating the amount of received light detected by the light detection unit is further provided, and the focus servo by the focus servo mechanism is turned on during the focus jump operation. Also good.

  The control unit has a signal level of an RF signal, a push-pull signal, or a pull-in signal that is generated from a signal that represents the amount of light received by a plurality of light receiving elements included in the light detection unit as the light reception amount level detected by the light detection unit. May be used.

  The control unit detects the first received light amount level detected by the light detection unit before the focus jump operation and the detection unit after the focus jump operation to determine whether the focus jump operation is successful. The second received light amount level may be compared, and if the first received light amount level and the second received light amount level are substantially the same, it may be determined that the focus jump operation has failed. .

  The control unit determines a third received light amount detected by the light detection unit before changing from the third correction amount to the fourth correction amount in order to determine whether or not there is a malfunction related to the focus. The level is compared with the fourth received light amount level detected by the detector after the change from the third correction amount to the fourth correction amount, and the fourth received light amount level is compared with the third received light amount level. If the received light amount level is smaller, it may be determined that there is a malfunction related to the focus.

  In order to solve the above-described problem, according to another aspect of the present invention, an objective lens for condensing laser light from a light source on the recording layer of the optical disc, and the focal point of the laser light is the focus of the optical disc. Provided on an optical path between the light source and the objective lens, an actuator that moves the objective lens so as to fit the recording layer, a light detector that receives the reflected light of the laser beam on the optical disc, and a spherical surface An optical disc apparatus comprising a spherical aberration correction mechanism for correcting aberrations and a control unit for controlling a spherical aberration correction amount by the spherical aberration correction mechanism, wherein the focal point of the laser beam is focused between the plurality of recording layers of the optical disc. A focus jump method for moving the spherical aberration correction amount by the spherical aberration correction mechanism from a first correction amount suitable for the first recording layer, Changing the second correction amount suitable for the second recording layer to a third correction amount between the first correction amount and the focus of the laser beam on the first recording layer of the optical disc; Performing a focus jump operation for moving the recording medium to the second recording layer; determining a success or failure of the focus jump operation based on a received light amount level detected by the light detection unit before and after the focus jump operation; Returning a spherical aberration correction amount by the spherical aberration correction mechanism from the third correction amount to the first correction amount when it is determined that the focus jump operation has failed. A focus jump method is provided.

  As described above, according to the present invention, it is possible to avoid an erroneous adjustment of the spherical aberration when the focus jump fails and to prevent the focus servo from becoming unstable.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, the overall configuration of the optical disc apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram showing the configuration of the optical disc apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the optical disc apparatus 1 according to the present embodiment stores various information on the optical disc 3 based on instructions from an external host device (for example, a personal computer, a digital video camera, etc., not shown). Is a device capable of reproducing the information recorded on the optical disc 3. In general, the optical disc apparatus 1 includes an optical pickup 10 that performs information recording and reproduction operations on the optical disc 3 using laser light, a disc drive unit 20 that rotationally drives the optical disc 3, and an optical pickup 10. And a control circuit 30 for controlling the disk drive unit 20.

  If the optical disk 3 is a storage medium that uses light for reading and writing information, for example, a high-density optical disk such as a CD, a DVD, or a BD (Blu-ray Disc), a magneto-optical disk such as an MO (Magneto-Optical disk), or the like. Any optical disc can be used. The optical disc 3 may be, for example, a read-only optical disc (CD-ROM (Read Only Memory), DVD-ROM, BD-ROM, etc.), a write-once optical disc (CD-R (CD Recordable), DVD-R, BD-R, etc.) or rewritable optical discs (CD-RW (CD Rewritable), DVD-RW, BR-RECD-RAM, DVD-RAM, MO, etc.) etc. There may be. The optical disc 2 is a multi-layer disc having a plurality of recording layers, details of which will be described later (see FIG. 3).

  Next, the optical pickup 10 will be described. The optical pickup 10 reads and writes information with respect to the optical disc 3 by irradiating the laser beam condensed on the optical disc 3 and receiving the reflected light. The optical pickup 10 detects a laser diode (Laser Diode: LD) 110 that is an example of a light source (light emitting element) that emits laser light, an LDD (LD Driver) 144 for driving the LD 110, and an emission power of the LD 110. An FPDIC (Front PDIC: not shown) and an objective lens 120 that is disposed opposite to the recording surface of the optical disc 3 and collects the laser light incident from the LD 110 and irradiates the recording layer of the optical disc 3 with spot light. (Condensing lens), a light detection unit 130 that receives reflected light (return light) of the laser beam on the optical disc 3 and detects the amount of received light, and a biaxial actuator that moves the objective lens 120 at least in the focus direction and the tracking direction 140, and the optical pickup 10 is moved in the radial direction of the optical disk 3. A slide motor 142 serving as a feed mechanism; an LD driver 144 that drives the laser diode 110; and an optical system 150 that guides the laser light from the LD 110 to the optical disc 3 and guides the reflected light from the optical disc 3 to the light detection unit 130. Prepare.

  Among these, the biaxial actuator 140 corresponds to the actuator of the present invention, and moves the objective lens 120 so that the focal point of the laser light is aligned with the recording layer of the optical disc 3. The biaxial actuator 140 moves the objective lens 120 at high speed and with high accuracy in the tracking direction (the disk radial direction parallel to the recording surface of the optical disk 3) and the focus direction (the direction perpendicular to the recording surface of the optical disk 3). . By finely adjusting the position of the objective lens 120 in the focus direction and the tracking direction by the biaxial actuator 140, the position control (focus control, tracking control) of the irradiation position of the light spot of the laser beam on the optical disc 3 can be performed. . Thereby, the irradiation position of the light spot of the laser beam (the focal position of the objective lens 120) is changed according to the surface shake of the optical disk 3 during the rotation (shift in the height direction of the objective lens 120 with respect to the optical disk 3). Accurate alignment with the recording layer. Further, the irradiation position of the light spot of the laser light can be made to accurately follow the target track in accordance with the track shake of the optical disc 3 (the deviation of the objective lens 120 relative to the optical disc 3 in the disc radial direction, ie, the track modulation component). it can.

  The light detection unit 130 has a function of receiving reflected light (return light) of laser light from the optical disc 3 and detecting the amount of light received. The light detection unit 130 includes, for example, an opto-electronic integrated circuit (OEIC) having a plurality of light receiving elements, an amplifier, and the like, a PDIC (Photo Detector IC), and the like. The light detection unit 130 includes a plurality of light receiving elements (eg, a photodetector: PD) arranged in a predetermined pattern, and an analog signal (hereinafter, “detection signal”) obtained by photoelectrically converting the amount of light received by each light receiving element into an electrical signal. Is output to the control circuit 30.

  The optical system 150 is composed of optical system components for guiding the laser light emitted from the LD 110 to the recording surface of the optical disk 3 and guiding the reflected light of the laser light on the optical disk 3 to the light detection unit 130. For example, the optical system 150 generates a main beam (0th order diffracted light) and a side beam (± 1st order diffracted light) from the laser light emitted from the LD 110 and irradiates the optical disc 3 with the main beam and the side beam. In addition to forming an optical path, a light guide path is formed in the light detection unit 130 for reflected light from the optical disc 3.

  Here, a specific example of the optical system 150 of the optical pickup 10 according to the present embodiment will be described in detail with reference to FIG. FIG. 2 is a schematic diagram illustrating a configuration example of the optical system 150 of the optical pickup 10 according to the present embodiment.

  As shown in FIG. 2, as an incident optical path of laser light, for example, laser light emitted from a laser diode 110 as a light source includes a collimator lens 111, an anamorphic prism 112, a grating 113, a beam splitter 114, a beam extract. The light passes through the panda 115 and the quarter-wave plate 116 in order, is incident on the objective lens 120 and is irradiated onto the optical disk 3. Further, as the optical path of the reflected light (returned light) of the laser light, the laser light reflected by the optical disc 3 is the objective lens 120, the quarter wavelength plate 116, the beam expander 115, the beam splitter 114, the collimator lens 121, the hologram. The light passes through the plate 122 and the cylindrical lens 123 in order, is incident on the light detection unit 130, and is received.

  Specifically, the laser light emitted from the laser diode 110 is converted from divergent light to parallel light by the collimator lens 111 and then shaped from an elliptical shape to a circular cross-sectional shape by the anamorphic prism 112. Further, this laser beam is transmitted through a grating 113, which is a diffraction grating, to one main beam (main beam: zero-order diffracted beam) and a plurality of (for example, two in the case of normal 3-beam DPP) side beams (sub-beams). : ± 1st order diffracted light). The main beam is a laser beam that forms a main spot for recording / reproducing information on the recording surface of the optical disc 3. Further, for example, the two side beams are laser beams having a certain aberration having opposite polarities and forming a pair of side spots at positions separated from the main spot on the recording surface of the optical disc 3. . In the illustrated example, a three-beam laser beam is used. However, the laser beam is not limited to this example, and an arbitrary laser beam such as a one-beam method or a five-beam method may be used.

  The laser light (main beam and side beam) emitted from the grating 113 passes through the beam splitter 114 and enters a beam expander 115 that is an optical unit for correcting spherical aberration. In addition, the beam splitter 114 reflects a part of the laser light and irradiates the front monitor photodetector 118 with the reflected light via the collimator lens 117. The front monitor photodetector 118 photoelectrically converts incident laser light to detect the amount of received light, and outputs this detection signal to the system controller 70 of the control circuit 30. In response to this, the system controller 70 and the LD driver 144 perform feedback control so that the emission intensity of the laser light emitted from the laser diode 110 is constant.

  The beam expander 115 is an example of a spherical aberration correction mechanism of the present invention, and has a function of correcting spherical aberration generated due to an error in the interlayer thickness of the multilayer disk. The beam expander 115 includes, for example, a movable concave lens 115a that is moved in the optical axis direction by a driving mechanism such as a stepping motor 160, and a fixed convex lens 115b. The beam expander 115 corrects the spherical aberration by changing the divergence / convergence degree of the laser light incident on the objective lens 120 by adjusting the distance between the concave lens 115a and the convex lens 115b. Such a beam expander 115 is suitable for correcting spherical aberration that appears prominently when a two-group objective lens 120 having a high numerical aperture (for example, NA = 0.85) is used. The state of the expander 115 (for example, the position of the concave lens 115a with respect to the convex lens 115b) is detected by an expander position sensor (not shown), and is output to the system controller 70 of the control circuit 30 described later as an expander position signal. This expander position signal corresponds to the spherical aberration correction amount by the expander 115.

  The laser light emitted from such a beam expander 115 is incident on the quarter wavelength plate 116 via a rising mirror (not shown). This quarter-wave plate 116 gives a phase difference of 90 ° to the incident laser beam, converts linearly polarized light into circularly polarized light and makes it incident on the objective lens 120, and also reflects the circularly polarized laser beam reflected by the optical disk 3. Converts light into linearly polarized light. The objective lens 120 is composed of, for example, a two-group objective lens and has a numerical aperture NA = 0.85. The objective lens 120 condenses the laser light that has passed through the beam expander 115 and irradiates a light spot (the main spot and the side spot) on the recording layer of the optical disc 3. By changing the phase of the recording layer of the optical disc 3 by irradiation with the main spot, various types of information are recorded, rewritten, or reproduced on the recording track of the optical disc 3. At the time of irradiation, position control of the objective lens 120 using the biaxial actuator 140, that is, tracking control, is performed so that the main spot is irradiated to the center of the track with an appropriate spot diameter (that is, in a focused state). And focusing control is performed.

  In an actual optical disc 3 such as a DVD, a recording track for recording information is called a “groove” and is formed in a groove shape having waviness with a predetermined amplitude and a predetermined frequency. A protrusion called a “land” is formed in. In the optical pickup 10 according to the present embodiment, the main spot is irradiated to the groove of the optical disc 3 and the side spot is irradiated to the land, but the present invention is not limited to such an example.

  Further, the laser light irradiated onto the optical disc 3 as described above is reflected after the light intensity is modulated by the recording information of the recording track of the optical disc 3, and the reflected laser light is reflected by the objective lens 120, 1/4. The light passes through the wave plate 116 and the beam expander 115 and is reflected by the beam splitter 114. The laser beam reflected by the beam splitter 114 is converted into convergent light by the collimator lens 121, and then a focus error signal is obtained by, for example, the SSD method (spot size detection method) by the hologram plate 122 and the cylindrical lens 123, for example. In addition to the above optical processing, the light is split into two side beams and a main beam and is incident on the light detection unit 130. The light detection unit 130 includes a plurality of light receiving elements (PD) that respectively receive the reflected light of the main beam and the side beam irradiated onto the optical disc 3, and the amount of light received detected by each light receiving element. A detection signal to be expressed is output to the control circuit 30. The optical system 150 of the optical pickup 10 according to the present embodiment has been described above with reference to FIG.

  With reference to FIG. 1 again, the disk drive unit 20 will be described. The disk drive unit 20 includes a spindle motor 22 that rotationally drives the optical disk 3, a spindle 24 that is connected to the spindle motor 22 and rotatably supports the optical disk 3, and a disk clamp 26 that fixes the optical disk 3 to the spindle 24. And a turntable (not shown) on which the optical disk 3 is placed. The spindle motor 22 is controlled by a system controller 70 (for example, a control microcontroller) and a spindle driver 72 provided in the control circuit 30, and rotates the optical disc 3 at a predetermined speed.

  Next, the control circuit 30 will be described. The control circuit 30 is a device that controls each unit of the optical disc apparatus 1. The control circuit 30 generates a servo signal (tracking error signal, focus error signal, etc.) and a reproduction signal based on the detection signal of each light receiving element input from the light detection unit 130, and the matrix circuit 40. A digital signal processor (DSP) 50 that generates a servo drive signal (tracking drive signal, focus drive signal, etc.) based on the servo signal input from the, and a servo drive signal input from the DSP 50 A driver 60 that drives each drive unit of the optical pickup 10, a system controller 70 that controls the operation of each unit of the optical disk device 1, and a spindle that drives the pindle motor 22 based on instructions from the system controller 70 And a driver 72.

  The matrix circuit 40 includes a matrix calculation circuit, an amplification circuit, and the like, and performs a matrix calculation process on the detection signal input from the light detection unit 130 to servo-control (for example, tracking) each drive unit. An error signal TE, a focus error signal FE, and a sum signal (pull-in signal: PI)) are generated. The tracking error signal TE is generated by a push-pull method, a differential push-pull method (DPP) or the like, and the focus error signal FE is generated by a spot size detection method, an astigmatism method, or the like.

  For example, the PD pattern of the light detection unit 130 includes four-divided light receiving elements A, B, C, and D for main beams (0th order diffracted light), and two divided light receiving elements E and F for side beams (+ 1st order diffracted light). In the case of the two-divided light receiving elements G and H for side beams (−1st order diffracted light), the DPP tracking error signal TE and the focus error signal FE are obtained by the following equations. In the following equations, A to H represent detection signals in the light receiving elements A to H, MPP is a main push-pull signal, SPP is a side push-pull signal, and k is a coefficient.

TE = MPP-k. (SPP1 + SPP2)
= {(A + B)-(C + D)}-k · {(E−F) + (G−H)}
FE = (A + C)-(B + D)

  The matrix circuit 40 includes an RF (Radio Frequency) amplifier (not shown). An RF signal that is a high-frequency signal representing the reproduction result of information recorded on the optical disc 3 is input from the light detection unit 130 to the matrix circuit 40, and the RF amplifier amplifies the RF signal to generate a reproduction signal, Output to the DSP 50. This reproduction signal is AD converted by the DSP 50 and then output to the host device. Note that the RF amplifier and the matrix circuit 40 may be configured separately.

  The DSP 50 generates a tracking error signal and a focus error signal by phase-compensating the tracking error signal and the focus error signal input from the matrix circuit 40, and outputs them to the tracking driver 62 and the focus driver 64. The DSP 50 outputs a signal in which the low frequency of the tracking error signal is emphasized by a low frequency emphasis filter (not shown) to the slide motor driver 66 as a slide drive signal. Further, the DSP 50 generates an expander drive signal based on an instruction from the system controller 70 and outputs the expander drive signal to the stepping motor 160 that is a drive actuator of the expander 115.

  The driver 60 includes, for example, a tracking driver 62, a focus driver 64, a slide motor driver 66, and an expander driver 68. The tracking driver 62 outputs a drive signal for driving the biaxial actuator 140 based on the tracking drive signal input from the DSP 50. The focus driver 64 outputs a drive signal for driving the biaxial actuator 140 based on the focus drive signal input from the DSP 50. The slide motor driver 66 outputs a drive signal for driving the slide motor 142 based on the slide drive signal input from the DSP 50. The expander driver 68 outputs a drive signal for driving the stepping motor 160 of the expander 115 based on the expander drive signal input from the DSP 50.

  The system controller 70 includes, for example, a microcontroller, a CPU, and the like, and controls each part of the servo system and the recording / reproducing system in the optical disc apparatus 1. The system controller 70 can be arbitrarily controlled by programming. The system controller 70 functions as a focus jump control unit that controls the focus jump operation, and also functions as a spherical aberration correction control unit that controls a spherical aberration correction amount by the expander 115 that is a spherical aberration correction mechanism. (See FIG. 5).

  The configuration of the optical disc apparatus 1 according to the present embodiment has been described above. In the present embodiment, a focus servo mechanism that performs focus servo includes, for example, the optical pickup 10, the matrix circuit 40, the DSP 50, the focus driver 64, and the like. The focus servo mechanism controls the actuator (the biaxial actuator 140) based on a signal (the detection signal) indicating the amount of received light detected by the light detection unit (the light detection unit 130). The spherical aberration correction mechanism for correcting the spherical aberration includes, for example, the expander 115 and the stepping motor 160 of the optical pickup 10 described above, and the control unit that controls the spherical aberration correction amount by the spherical aberration correction mechanism is as follows. It comprises a matrix circuit 40, a DSP 50, an expander driver 68, a system controller 70, and the like.

  Next, a configuration example of the optical disc 3 according to the present embodiment and a recording / reproducing operation for the optical disc 3 will be described. Hereinafter, an example in which the optical disc 3 is a high-density multilayer disc such as a Blu-ray disc (BD) will be described.

  The disc size of the BD is, for example, a diameter of 120 mm and a disc thickness of 1.2 mm. When recording / reproducing information on such a BD, for example, a phase change mark (for example, a phase change mark (BD) is applied to the BD under a combination of a laser beam having a wavelength of 405 nm (so-called blue laser) and an objective lens 120 having a numerical aperture NA of, for example, 0.85. (Phase change mark) is recorded and reproduced. In this case, the track pitch is, for example, 0.32 μm, the linear density is, for example, 0.12 μm / bit, and a data block of 64 KB (kilobytes) is used as one recording / playback unit, and the format efficiency is about 82%. For example, data of about 23.3 GB (gigabytes) can be recorded on one recording layer of the disc. Furthermore, the data storage capacity can be further increased by forming the recording layer into a multi-layer structure and using a BD as a multi-layer disk. For example, by using a double-layer disk, the data storage capacity is 46.6 GB which is twice the above. It can be. Of course, an n-layer structure of three or more layers is also possible, and the data storage capacity can be increased to n times the above.

  FIG. 3 is an explanatory diagram schematically showing a disc structure when the optical disc 3 is, for example, a BD double-layer disc. As shown in FIG. 3, the optical disc 3 has a structure in which a recording layer L0, an intermediate layer 5, a recording layer L1, and a cover layer 6 are laminated in this order on a polycarbonate substrate 4. The thickness of the disk is, for example, about 1.2 mm, the thickness of the polycarbonate substrate 4 is, for example, about 1.1 mm, and the thickness of the intermediate layer 5 is, for example, about 25 μm.

  When recording / reproducing information on the optical disc 3 in FIG. 3, the laser beam 7 collected by the objective lens 120 is incident from the cover layer 6 side and focused on one of the recording layers L0 and L1 to be recorded / reproduced. Let In this focusing operation, the objective lens 120 is moved in the focusing direction by the biaxial actuator 140 so that the focal point (light spot position) of the laser beam 7 is aligned with the recording layer L0 or L1 to be recorded / reproduced. For example, as shown by the solid line in FIG. 3, when the laser beam 7 is focused on the recording layer L1, the return light reflected by the recording layer L1 is detected by the light detection unit 130, and a reproduction signal is detected from the detection signal. An RF signal is generated.

  In a multilayer disc, it is necessary to switch the recording / reproducing position between the plurality of recording layers L0 and L1. Therefore, the focus for moving the focal position of the objective lens 120 (that is, the light spot position of the laser beam) from the currently focused recording layer L1 (current recording layer) to the other recording layer L0 (target recording layer). Perform a jump. Such a focus jump is executed by moving (jumping) the objective lens 120 by a predetermined interlayer distance (distance between the recording layers L0 and L1) in the focus direction by the actuator 140.

  Here, the spherical aberration SA of the objective lens 120 when the optical disk 3 is used will be described with reference to FIG. Since the objective lens 120 having a high numerical aperture NA is used for a high-density multilayer disc such as a BD shown in FIG. 3, the influence of the spherical aberration SA caused by the disc layer thickness error becomes significant. For this reason, it is necessary to correct the spherical aberration by a spherical aberration correction mechanism such as the expander 115.

  The spherical aberration SA has an optimum correction amount that varies depending on the thickness of the optical disc 3 up to the recording layer L0 or L1 that is a focus target. Therefore, the optimal spherical aberration correction amount SA_L0 for the recording layer L0 and the optimal spherical aberration correction amount SA_L1 for the recording layer L1 are different values. If the spherical aberration correction amount for the recording layer currently being recorded / reproduced is deviated, the received light amount of the return light detected by the light detection unit 130 is decreased, so that the signal level of the focus error signal FE is also reduced and the focus servo is disabled. It becomes stable.

  In particular, when performing the above-mentioned focus jump, the optimum spherical aberration correction amount also changes abruptly according to the switching of the recording layer to be recorded / reproduced, so that the spherical aberration correction amount shifts and the focus servo becomes unstable. Cheap. That is, in general, the response speed of the stepping motor 160 of the expander 115 that corrects spherical aberration is slower than the response speed of the biaxial actuator 140 that performs focus jump. Therefore, simultaneously with the focus jump, the spherical aberration correction amount by the expander 115 cannot be quickly changed from the correction amount SA_L1 suitable for the current recording layer L1 to the correction amount SA_L0 suitable for the target recording layer L0. Accordingly, since the spherical aberration is corrected with the correction amount SA_L1 suitable for the original recording layer L1 with respect to the target recording layer L0 after the focus jump, the deviation of the spherical aberration correction amount becomes large, and the focus servo is easily lost. .

  For this reason, in the technique of Patent Document 1, the spherical aberration correction amount is not changed at once from the current correction amount SA_L1 to the target correction amount SA_L0, but is corrected at another stage to prevent the focus servo from being lost. is doing. That is, before the focus jump, the spherical aberration correction amount is changed from the current correction amount SA_L1 to an intermediate correction amount SA_MID between SA_L1 and SA_L0, and after the focus jump, the intermediate correction amount SA_MID is changed to the target correction amount SA_L0. To do.

  However, as described above, the focus jump may fail due to the surface shake of the optical disc 3 or the variation of the biaxial sensitivity. However, in the spherical aberration adjustment method of Patent Document 1, even when the focus jump from the current recording layer LI to L0 fails, the target correction amount SA_L0 is finally changed. For this reason, there is a problem that an erroneous adjustment of the spherical aberration SA in which the target correction amount SA_L0 is applied to the current recording layer L1 occurs, and the focus servo becomes unstable.

  Therefore, in order to solve such a problem, in this embodiment, the success or failure of the focus jump from the current recording layer L1 to the target recording layer L is determined by detecting the received light level P of the return light before and after the focus jump. If the focus jump is successful, the spherical aberration correction amount SA is adjusted to the target correction amount SA_L0. If the focus jump is unsuccessful, the target correction amount SA_L0 is adjusted. Do not do it. Thereby, it is possible to avoid focus misadjustment when the focus jump fails and to prevent the focus servo from becoming unstable.

  Here, with reference to FIG. 4, the principle of the method for determining the success or failure of the focus jump according to the present embodiment will be described. FIG. 4 is a graph showing the relationship between the received light level P of the return light (reflected light) from the optical disc 3 and the spherical aberration correction amount SA. Note that the received light level P of the return light corresponds to the received light amount of the return light detected by the light detection unit 130 when the arbitrary recording layer L of the optical disc 3 is irradiated with the laser light with the focal position being aligned. Represents the signal level.

  As shown in FIG. 4, the received light level P of the return light from the arbitrary recording layer L of the optical disc 3 becomes the maximum value Pmax when the spherical aberration correction amount SA is the optimum correction amount SA_L for the recording layer L. The spherical aberration correction amount SA decreases as it deviates from the optimal correction amount SA_L. Thus, the received light level P of the return light has a peak (maximum value Pmax) when the spherical aberration correction amount SA is the optimum correction amount SA_L. The relationship between the received light level P of return light and the spherical aberration correction amount SA shows the same tendency for an arbitrary recording layer L of the optical disc 3.

  As described above, since the optimum spherical aberration correction amount SA_L is different for each of the recording layers L0 and L1 (SA_L0 ≠ SA_L1), the peak position of the received light amount level of the return light is also the recording layer L on which the laser light is focused. (Refer to FIG. 6). Accordingly, when the focus jump is successful with the spherical aberration correction amount SA fixed, the received light level P of the return light changes before and after the focus jump.

  Therefore, the success or failure of the focus jump can be determined using the relationship between the return light received light level P and the spherical aberration correction amount SA as shown in FIG. That is, when the received light amount level P of the return light before and after the focus jump is detected and the received light amount level P has changed, it is determined that the focus jump has succeeded and the received light amount level P has not changed. Can be determined as a focus jump failure.

  Further, as the light reception level P of the return light shown in FIG. 4, any signal level corresponding to the amount of the return light detected by the light detection unit 130 can be used. For example, the return light reception level P is generated by the matrix circuit 40. RF signal, push-pull signal (PP signal) or pull-in signal (PI signal) can be used. The PP signal is a difference signal for generating a push-pull tracking error signal TE, and the TE signal varies in the same manner as the PP signal.

  These RF signals, PP signals (or TE signals), and PI signals all have their signal levels lowered when the spherical aberration correction amount SA is shifted. In this respect, the focus error signal FE is the same, but since the S-shaped level of the FE signal cannot be detected unless the focus servo is removed, when the focus jump is performed with the focus servo turned on, the FE signal receives the amount of received light. Not suitable as level P.

  Therefore, in the present embodiment, the level of the tracking light signal TE (hereinafter referred to as “TE level”) and the level of the pull-in signal PI (hereinafter referred to as “PI level”) are used as the received light amount level P of the return light. To do. By using such a TE signal (corresponding to a PP signal) and a PI signal, it is possible to detect the received light level of the return light without removing the focus servo during focus jump and without turning off the focus servo.

  Further, FIG. 4 shows a boundary value P0 of the received light amount level P of the return light within a range where the focus servo is not removed. If the received light amount level P of the return light is less than the boundary value P0, the received light amount level is too low and the focus servo may be lost, and the focus servo operation cannot be stably executed. The return light received light level P is not less than the boundary value P0 when the spherical aberration correction amount SA is not less than the lower limit value SA_Lmin and not more than the upper limit value SA_Lmax. Such a range of the spherical aberration correction amount SA (SA_Lmax ≦ (SA ≦ SA_Lmax) corresponds to “a range in which the focus servo with respect to the recording layer of the optical disk by the focus servo mechanism cannot be removed”. The range of the spherical aberration correction amount SA that does not cause the focus servo to deviate is obtained by measuring the relationship between the spherical aberration correction amount SA and the received light amount level P of the return light as shown in FIG. Can do.

  As will be described later, in this embodiment, when the focus jump from the current recording layer L1 to the target recording layer L0, the spherical aberration correction amount SA is set to the correction amount SA1 suitable for the current recording layer L1 and the target recording layer L0. Are moved stepwise to intermediate correction amounts SA2 and SA3 with a correction amount SA4 suitable for the above (see FIG. 7). At this time, the intermediate correction amounts SA2 and SA3 are set to a correction amount SA (SA_L1max ≦ SA ≦ SA_L1max and SA_L0max ≦ SA ≦ SA_L0max) within a range in which the focus servo is not lost in both the current recording layer L1 and the target recording layer L0. Is set. As a result, it is possible to prevent the focus servo from being lost regardless of whether the focus jump is successful or failed.

  As described above, in the optical disc apparatus 1 according to the present embodiment, the success or failure of the focus jump is determined by detecting the received light level (TE level, PI level) of the return light before and after the focus jump. Accordingly, the spherical aberration correction amount SA is adjusted stepwise. Hereinafter, a method for executing the focus jump operation accompanied by the adjustment of the spherical aberration correction amount SA will be described in detail.

  First, with reference to FIG. 5, the configuration for performing the adjustment operation of the spherical aberration correction amount SA and the focus jump operation in the optical disc apparatus 1 according to the present embodiment will be described in more detail. FIG. 5 is a schematic diagram showing a configuration of a main part of the optical disc apparatus 1 according to the present embodiment, mainly showing elements related to the adjustment operation of the spherical aberration correction amount SA and the focus jump operation, and other elements are shown. Is omitted.

  As shown in FIG. 5, the optical pickup 10 includes the LD 110, the expander 115, the objective lens 120, the light detection unit 130, the biaxial actuator 140, the stepping motor 160, and the like described above. By changing the interval between the concave lens 115a and the convex lens 115b (see FIG. 2) of the expander 115 by the stepping motor 160, the spherical aberration correction amount SA by the expander 115 is adjusted. The spherical aberration correction amount SA by the expander 115 is expressed, for example, by the relative position of the concave lens 115a to the convex lens 115b of the expander 115 (hereinafter referred to as “expander position”). Since this spherical aberration correction position corresponds to the spherical aberration correction amount SA by the expander 115, the expander position may be controlled in order to control the spherical aberration correction amount SA. This expander position is detected by the expander position sensor 162 and output to the system controller 70.

  The DSP 50 includes a focus phase compensation circuit 51 that compensates the phase of the focus error signal in order to stably close the focus servo, a switch circuit 52 that switches between the focus servo operation and the focus jump operation, and a kick pulse for focus jump. A kick pulse generating circuit 53 for generating, and a stepping logic circuit 54 for generating a stepping drive signal for driving the stepping motor 160 of the expander 115 are provided. The switch circuit 52, kick pulse generation circuit 53, and stepping logic circuit 54 are controlled by a system controller 70.

  The switch circuit 52 connects either the phase compensation circuit 51 or the kick pulse generation circuit 53 to the focus driver 64 based on an instruction from the system controller 70. Thus, the focus drive signal output from the DSP 50 to the focus driver 64 is switched between the focus error signal phase-compensated by the focus phase compensation circuit 51 and the kick pulse signal for kick-focus-jump. The focus driver 62 controls the voltage of the focus coil 141 according to the focus drive signal (focus error signal or kick pulse signal) input from the DSP 50.

  Further, by installing a predetermined program in the system controller 70, the system controller 70 causes the focus jump control unit 74 for controlling the focus jump operation and the spherical aberration for controlling the spherical aberration correction amount by the expander 115. It functions as the correction control unit 76.

  The focus jump control unit 74 switches the switch circuit 52 to the focus jump side in order to execute the focus jump, and controls the kick pulse generation circuit 53 to perform a focus jump from the current recording layer to the target recording layer. Generate a kick pulse. The spherical aberration correction control unit 76 controls the stepping logic circuit 54 so that the expander 115 generates a stepping drive signal for setting the spherical aberration correction amount to a predetermined amount.

  Next, the focus servo operation, the focus jump operation, and the spherical aberration correction operation by the optical disc apparatus 1 having the above configuration will be described.

  First, the focus servo operation will be described. During execution of the focus servo, the switch circuit 52 is controlled to the Servo side by the system controller 70, and the focus servo is closed (focus servo ON state). Then, the light detection unit 130 of the optical pickup 10 detects the amount of light received from the optical disc and outputs a detection signal representing the amount of light received. The detection signal is subjected to matrix calculation processing by the matrix circuit 40 to generate a focus error signal FE. This FE signal is phase-compensated by the focus phase compensation circuit 51 of the DSP 50 to become a focus drive signal. This focus drive signal is output to the focus drive 64 via the switch circuit 52. The focus driver 64 outputs a drive signal corresponding to the focus drive signal to the biaxial actuator 140 to control the voltage applied to the focusing coil 141. As a result, the biaxial actuator 140 is driven to move the objective lens 120 in the focus direction so that the focal position matches the recording layer being recorded / reproduced.

  Next, the focus jump operation will be described. The focus jump operation is performed with the tracking servo open (tracking servo OFF state) while the focus servo is closed (focus servo ON state). During the focus jump, the switch circuit 52 is temporarily switched to the Jump side under the control of the system controller 70, and the kick pulse signal generated by the kick pulse generation circuit 53 is output to the focus driver 62. The focus driver 64 outputs a drive signal corresponding to the kick pulse signal to the biaxial actuator 140 and applies it to the focusing coil 141. As a result, the biaxial actuator 140 is driven to execute a focus jump operation for moving the focal position (light spot position) of the objective lens 120 from the current recording layer to another recording layer.

  Next, the spherical aberration correction operation will be described. The expander position representing the spherical aberration correction amount SA by the expander 115 is detected by the expander position sensor 162 and input to the system controller 70. The spherical aberration correction controller 76 of the system controller 70 controls the stepping logic circuit 54 based on the detected current expander position, and generates an expander drive signal for moving the expander position to a desired position.

  During normal recording / reproduction, the target value of the spherical aberration correction position SA (expander position) is determined so that the level (amplitude value) of the RF signal generated by the matrix circuit 40 is maximized. A signal whose phase is compensated for is output to the expander driver 68 as an expander drive signal. On the other hand, at the time of focus pull-in or focus jump, the spherical aberration correction amount SA (expander position) is controlled so as to follow a predetermined target value read from a memory (not shown). Details of the spherical aberration correction operation during the focus jump will be described later.

  Next, a focus jump method in the optical disc apparatus 1 described above will be described with reference to FIGS. FIG. 6 is a flowchart showing the focus jump method in the optical disc apparatus 1 according to the present embodiment. FIG. 7 shows the relationship between the received light level P of return light and the spherical aberration correction amount SA in the focus jump method of FIG. It is explanatory drawing shown.

  In the example of FIGS. 6 and 7, in the multilayer disc 3 of FIG. 3, the recording layer L0 (target recording layer L0) from the recording layer L1 (current recording layer L1) that is currently in focus to the focus jump destination. An example of focus jump to) will be described. Further, as the received light amount level P of the return light, the level of the pull-in signal PI generated by the matrix circuit 40 (hereinafter referred to as “PI level”) and the level of the tracking error signal TE (hereinafter referred to as “TE level”). An example of use will be described.

  Further, as shown in FIG. 7, the optimum spherical aberration correction amount SA in the current recording layer L1 is SA1 (hereinafter referred to as “current correction amount SA1”), and the optimum spherical aberration correction amount in the target recording layer L0. SA is SA4 (hereinafter referred to as “target correction amount SA4”) (SA4> SA1). Further, SA_L0min in FIG. 7 indicates a lower limit value of the spherical aberration correction amount SA in a range where the focus servo cannot be deviated in the target recording layer L0, and SA_L1max is a spherical aberration correction amount in a range where the focus servo is not deviated in the target recording layer L0. The upper limit value of SA shall be shown.

  Further, before the execution of the flow shown in FIG. 6, the received light amount for each recording layer is set in advance so that the received light amount level P (PI level, TE level) of the return light in each recording layer L0, L1 of the optical disc 3 becomes equal. It is assumed that the level P correction gain is adjusted. By this correction gain adjustment, the light reception level P of the return light in each of the recording layers L0 and L1 is normalized, and the difference in the light reception level of the return light between the current recording layer L1 and the target recording layer L0 is obtained. It can be lost. The flow of FIG. 6 will be described below with reference to FIG. 7 as appropriate.

  As shown in FIG. 6, first, before the focus jump, the system controller 70 turns off the tracking servo and sets it to the OFF state (step S10). Since the tracking operation is unnecessary in the focus jump operation, the tracking servo is turned off. However, the focus servo is not dropped and remains on. Thereby, since the focus servo operation can be continued even during the focus jump operation, it is not necessary to re-apply the focus servo after the focus jump, and it is possible to avoid the problem that it takes a very long time to re-apply the focus servo.

  Next, the received light level P (PI level, TE level) of the return light from the current recording layer L1 of the optical disc 3 is measured in the state of the optimum current correction amount SA1 in the current recording layer L1 (step S12). The measured value of the received light amount level P is A.

  Thereafter, as shown in FIG. 7, before the focus jump, the spherical aberration correction amount SA by the expander 115 is set in advance within the range in which the focus servo for the target recording layer L0 is not removed (SA_L0max ≦ SA ≦ SA_L0max). Is changed to an intermediate correction amount SA2 between the current correction amount SA1 and the target correction amount SA4 (hereinafter referred to as “first intermediate correction amount SA2”) (step S14). Thereby, even if the focus jump fails in the subsequent step S18, the focus servo can be prevented from being removed. Needless to say, the first intermediate correction amount SA2 is within a range in which the focus servo with respect to the current recording layer L1 at which the focal position is in focus is not lost (SA_L1max ≦ SA ≦ SA_L1max). Thereby, it is possible to prevent the focus servo from being lost before the focus jump due to the change of the spherical aberration correction amount SA in step S14.

  Further, before the focus jump, the light reception level P (PI level, TE level) of the return light from the current recording layer L1 of the optical disc 3 is measured with the spherical aberration correction amount SA being the first intermediate correction amount SA2. (Step S16). The measured value of the received light amount level P at this time is B.

  Thereafter, a focus jump from the current recording layer L1 to the target recording layer L0 is executed (step S18), and the focal position of the objective lens 120 is moved from the current recording layer L1 to the target recording layer L0.

  Next, after the focus jump, the light reception level P (PI level, TE level) of the return light from the current recording layer L1 of the optical disc 3 is measured with the spherical aberration correction amount SA being the first intermediate correction amount SA2. (Step S20). The measured value of the received light amount level P at this time is C.

  Thereafter, the success or failure of the focus jump in S18 is determined based on the measured values A, B, and C of the received light amount level P of the return light (step S22). As shown in FIG. 7, when the spherical aberration correction amount SA is the first intermediate correction amount SA2, the light reception level P of the return light is received by the target recording layer L0 more than the light reception level of the current recording layer L1. The level is smaller. Therefore, if the focus jump is successful, the measured value A> B> C should be satisfied, and if the focus jump is unsuccessful, the measured value A or B ≦ C may be satisfied. Therefore, the success or failure of the focus jump can be determined by comparing the measurement values A and B with the measurement value C. In addition, even if it does not compare both the measured value A and B with the measured value C, you may make a determination by comparing either measured value A or B with the measured value C.

  As a result of the determination, if the measured value A or B ≦ C, it is determined that the focus jump has failed, and the process proceeds to step S24. In this case, the spherical aberration correction amount SA is returned from the first intermediate correction amount SA2 to the current correction amount SA1 (step S24), the tracking servo is turned on, and then the address of the optical disk 3 is confirmed (step S26). The process of S22 is retried (step S28).

  On the other hand, when the measured value A> C and B> C in step S22, it is determined that the focus jump is successful, and the process proceeds to step S30.

  In step S30, as shown in FIG. 7, the spherical aberration correction amount SA by the expander 115 is set within the range in which the focus servo for the current recording layer L1 cannot be removed (SA_L1max ≦ SA ≦ SA_L1max). To a correction amount SA3 intermediate between the first intermediate correction amount SA2 and the target correction amount SA4 (hereinafter referred to as “second intermediate correction amount SA3”) (step S30). Accordingly, it is possible to prevent the focus servo from being lost due to the change of the spherical aberration correction amount SA in step S30. Furthermore, since the spherical aberration correction amount SA is not changed from SA2 to SA4 at a time but is changed stepwise from SA2 → SA3 → SA4, it is possible to more reliably prevent the focus servo from being lost. Needless to say, the second intermediate correction amount SA3 is within a range (SA_L0max ≦ SA ≦ SA_L0max) in which the focus servo with respect to the target recording layer L0 in focus is not deviated.

  Next, in the state where the spherical aberration correction amount SA is the second intermediate correction amount SA3, the received light amount level P (PI level, TE level) of the return light from the target recording layer L0 of the optical disc 3 is measured (step S32). The measured value of the received light amount level P at this time is D.

  Thereafter, based on the measured values C and D of the received light amount level P of the return light, the presence / absence of a malfunction related to the focus is determined (step S34). As shown in FIG. 7, since SA3 is closer to SA4 than SA2, when the spherical aberration correction amount SA is changed from SA2 to SA3, the light reception level P of the return light at the target recording layer L0 increases. Therefore, when there is no malfunction related to the focus, for example, when the focus jump is successful and the focus servo is in a normal state, the measured value D> C should be satisfied. On the other hand, when there is a malfunction related to the focus, for example, when the focus jump fails or when the focus servo is in an abnormal state, there is a possibility that the measured value D ≦ C. Therefore, by comparing the measured value C and the measured value D, it is possible to re-determine the success or failure of the focus jump and determine whether the focus servo operation is normal or abnormal.

  As a result of the determination, if the measured value D> C, it is determined that the focus jump has been successful, the focus servo is in a normal state, and there is no malfunction related to the focus, and the process proceeds to step S36. The aberration correction amount SA is changed from the second intermediate correction amount SA3 to the target correction amount SA4 (step S36), and all the processes are ended.

  On the other hand, if the measured value D ≦ C in step S34 and the measured value D is lower than the predetermined value by more than C, the focus control is performed such that the focus jump has failed or the focus servo is abnormal. It is determined that some problem has occurred in the system and there is a malfunction related to the focus, and the process proceeds to step S38. In this case, the spherical aberration correction amount SA is returned from the second intermediate correction amount SA3 to the first intermediate correction amount SA2 (step S38), and the target recording layer L0 of the optical disc 3 when the spherical aberration correction amount SA is in the state SA2 (or The received light level P (PI level, TE level) of the return light from the current recording layer L1 is measured again (step S40). The measured value of the received light amount level P at this time is C ′. Thereafter, based on the remeasured measurement value C ′ and the measurement value, it is determined whether there is a malfunction related to the focus (step S42). If the result of this determination is that the measurement value C ′ <D, it is determined that there is no malfunction related to the focus, and the process proceeds to step S36. On the other hand, when the measured value C ′ ≧ D, it is determined again that there is a malfunction related to the focus, and the process returns to step 24 to return the spherical aberration correction amount SA from SA2 to SA1 (step S24), and the tracking servo. Is turned on, the address of the optical disk 3 is confirmed (step S26), and the retry process of S10 to S22 is performed (step S28).

  The optical disc apparatus 1 according to the present embodiment and the focus jump method using the same have been described above. According to the present embodiment, when the focus jump from the current recording layer L1 to the target recording layer L0, the received light level P of the return light is detected before and after the focus jump, and the detected values A, B, and C are compared. As a result, the success or failure of the focus jump from the current recording layer L1 to the target recording layer L is determined. For this reason, when it is determined that the focus jump is successful, the spherical aberration correction amount SA is adjusted to the target correction amount SA4, and when it is determined that the focus jump has failed, the target correction amount is adjusted. A response such as returning to the current correction amount SA1 without performing the adjustment to SA4 is performed. Thereby, it is possible to avoid focus misadjustment when the focus jump fails and to prevent the focus servo from becoming unstable. Further, it can be avoided that the signal reading performance after the tracking servo is turned on and the operation becomes unstable due to the SA misadjustment when the focus jump fails.

  Further, in the present embodiment, when the focus jump is performed, the spherical aberration correction amount SA is not changed from the current correction amount SA1 to the target correction amount SA4 at a time, but instead is changed from SA1 → SA2 → SA3 → SA4. The correction amount is changed stepwise so as to approach the target correction amount SA4 from the correction amount SA1. At this time, the intermediate correction amounts SA2 and SA3 are set to a correction amount SA (SA_L0max ≦ SA ≦ SA_L1max) in a range where the focus servo does not deviate in both the current recording layer L1 and the target recording layer L0. As a result, it is possible to prevent the focus servo from being lost regardless of whether the focus jump is successful or failed. Therefore, it is possible to prevent the focus servo from becoming unstable when the focus jump is executed with the focus servo applied.

  Further, since the spherical aberration correction amount SA is adjusted stepwise using the plurality of intermediate correction amounts SA2 and SA3, normal / abnormal focus jump and focus servo operation are performed a plurality of times in the state of each intermediate correction amount SA2 and SA3. Can be judged. Accordingly, since the determination can be performed more accurately, it is possible to prevent the focus servo from being more reliably removed and to prevent the focus servo from becoming unstable.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the example in which the expander 115 is used as the spherical aberration correction mechanism has been described, but the present invention is not limited to such an example. The spherical aberration correction mechanism may be configured by, for example, an optical element such as a liquid crystal element or a spherical aberration correction element as long as it can correct spherical aberration caused by the multilayer disk. That is, as a method of correcting spherical aberration, for example, a method of correcting by phase using a refractive index change of a liquid crystal element, a divergence of laser light incident on an objective lens by adjusting a distance between a laser light source and a collimator. -A method of correcting by changing the degree of convergence may be used. In these cases, instead of the expander position according to the above-described embodiment, the spherical aberration correction amount SA is determined by, for example, a phase change amount associated with a change in the refractive index of the liquid crystal element, an interval between the laser light source and the collimator It can be adjusted.

  In FIGS. 6 and 7, the example in which the focus jump is performed from the recording layer L1 to the recording layer L0 in the dual-layer disc has been described. Can be executed.

  In the above embodiment, the spherical aberration correction amount SA is adjusted stepwise using the two intermediate correction amounts SA2 and SA3. However, the present invention is not limited to such an example. For example, the spherical aberration correction amount SA may be adjusted in stages using only one intermediate correction amount (for example, SA2 or SA3), or three or more intermediate correction amounts (for example, SA2, SA3,...). The spherical aberration correction amount SA may be adjusted stepwise using SAn). As the number of intermediate correction amounts used increases, the success or failure of the focus jump or the malfunction of the focus servo can be determined more accurately. At this time, if any of the intermediate correction amounts is set to a correction amount SA within a range in which the focus servo does not deviate in both the current recording layer L1 and the target recording layer L0, erroneous adjustment of the focus servo can be avoided.

It is explanatory drawing which shows the structure of the optical disk apparatus concerning the 1st Embodiment of this invention. It is a schematic diagram which shows the structural example of the optical system of the optical pick-up concerning the embodiment. It is explanatory drawing which shows typically the structure of the double layer disc concerning the embodiment. It is a graph which shows the relationship between the light reception amount level P of the return light from the optical disk 3 concerning the embodiment, and spherical aberration correction amount SA. It is the schematic which shows the structure of the principal part of the optical disk apparatus concerning the embodiment. 4 is a flowchart showing a focus jump method in the optical disc apparatus according to the embodiment. 4 is a flowchart showing a focus jump method in the optical disc apparatus according to the embodiment. FIG. 7 is an explanatory diagram showing a relationship between a received light amount level P of return light and a spherical aberration correction amount SA in the focus jump method of FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 3 Optical disk 4 Polycarbonate substrate 5 Intermediate | middle layer 6 Cover layer 10 Optical pick-up 20 Disk drive part 22 Spindle motor 30 Control circuit 40 Matrix circuit 50 DSP
51 Focus Phase Compensation Circuit 52 Switch Circuit 53 Kick Pulse Generation Circuit 54 Stepping Logic Circuit 60 Driver 62 Tracking Driver 64 Focus Driver 66 Slide Motor Driver 68 Expander Driver 70 System Controller 72 Spindle Driver 74 Focus Jump Control Unit 76 Spherical Aberration Correction Control Unit 110 Laser diode 120 Objective lens 130 Photodetector 140 Biaxial actuator 142 Slide motor 144 LD driver 150 Optical system 160 Stepping motor 162 Expander position sensor L0, L1 Recording layer

Claims (9)

An optical disc apparatus for recording or reproducing information on or from an optical disc having a plurality of recording layers:
An objective lens for condensing a laser beam from a light source on the recording layer of the optical disc;
An actuator for moving the objective lens so that the laser beam is focused on the recording layer of the optical disc;
A light detection unit that receives the reflected light of the laser beam on the optical disc;
A spherical aberration correction mechanism provided on an optical path between the light source and the objective lens for correcting spherical aberration;
A control unit for controlling a spherical aberration correction amount by the spherical aberration correction mechanism;
With
The controller is
Before performing the focus jump operation for moving the focal point of the laser beam from the first recording layer to the second recording layer of the optical disc, the spherical aberration correction amount by the spherical aberration correction mechanism is applied to the first recording layer. Changing from a suitable first correction amount to a third correction amount between the second correction amount suitable for the second recording layer and the first correction amount;
After performing the focus jump operation, the success or failure of the focus jump operation is determined based on the received light amount level detected by the light detection unit before and after the focus jump operation,
An optical disc apparatus characterized in that, when it is determined that the focus jump operation has failed, the spherical aberration correction amount by the spherical aberration correction mechanism is returned from the third correction amount to the first correction amount. The controller is
When it is determined that the focus jump operation is successful, the spherical aberration correction amount by the spherical aberration correction mechanism is changed from the third correction amount to a fourth between the third correction amount and the second correction amount. Change the correction amount to
Based on the received light amount level detected by the detection unit before and after the change from the third correction amount to the fourth correction amount, it is determined whether there is a malfunction related to the focus,
When it is determined that there is a malfunction related to the focus, the spherical aberration correction amount by the spherical aberration correction mechanism is returned from the fourth correction amount to the first correction amount or the third correction amount. The optical disc apparatus according to claim 1. A focus servo mechanism for controlling the actuator based on a signal representing the amount of received light detected by the light detector;
The optical disc apparatus according to claim 2, wherein the fourth correction amount is set to a spherical aberration correction amount in a range in which focus servo with respect to the first recording layer by the focus servo mechanism is not lost. A focus servo mechanism for controlling the actuator based on a signal representing the amount of received light detected by the light detector;
2. The optical disk apparatus according to claim 1, wherein the third correction amount is set to a spherical aberration correction amount in a range in which focus servo with respect to the second recording layer by the focus servo mechanism is not removed. A focus servo mechanism for controlling the actuator based on a signal representing the amount of received light detected by the light detector;
2. The optical disc apparatus according to claim 1, wherein a focus servo by the focus servo mechanism is in an on state during the focus jump operation.   The control unit has a signal level of an RF signal, a push-pull signal, or a pull-in signal that is generated from a signal that represents the amount of light received by a plurality of light receiving elements of the light detection unit as the light reception amount level detected by the light detection unit. The optical disk apparatus according to claim 1, wherein: The controller is
In order to determine the success or failure of the focus jump operation, a first received light amount level detected by the light detection unit before the focus jump operation, and a second light reception detected by the detection unit after the focus jump operation. Compare with quantity level,
2. The optical disc apparatus according to claim 1, wherein when the first received light amount level and the second received light amount level are substantially the same, it is determined that the focus jump operation has failed. The controller is
In order to determine whether or not there is a malfunction related to the focus, a third received light amount level detected by the light detection unit before the change from the third correction amount to the fourth correction amount, and the first Comparing the fourth received light amount level detected by the detection unit after the change from the correction amount of 3 to the fourth correction amount,
3. The optical disc apparatus according to claim 2, wherein when the fourth received light amount level is smaller than the third received light amount level, it is determined that there is a malfunction related to the focus. 4. An objective lens for condensing laser light from a light source on the recording layer of the optical disc, an actuator for moving the objective lens so that the focal point of the laser light is aligned with the recording layer of the optical disc, and the optical disc in the optical disc A light detector that receives reflected light of the laser beam, a spherical aberration correction mechanism for correcting spherical aberration, provided on the optical path between the light source and the objective lens, and spherical aberration by the spherical aberration correction mechanism A focus jump method for moving the focal point of the laser beam between the plurality of recording layers of the optical disc, comprising: a control unit that controls a correction amount;
The spherical aberration correction amount by the spherical aberration correction mechanism is changed from the first correction amount suitable for the first recording layer to the second correction amount suitable for the second recording layer and the first correction amount. Changing to a third correction amount in between;
Performing a focus jump operation for moving the focal point of the laser beam from the first recording layer to the second recording layer of the optical disc;
Determining the success or failure of the focus jump operation based on the received light level detected by the light detector before and after the focus jump operation;
Returning the spherical aberration correction amount by the spherical aberration correction mechanism from the third correction amount to the first correction amount when it is determined that the focus jump operation has failed;
A focus jump method characterized by comprising:

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