JP2007328842A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive which can achieve focusing servo in multi-layer optical disk. <P>SOLUTION: The drive includes a servo signal generating circuit generating FES (a-FES) by an astigmatic method and FES (d-FES) by a differential astigmatic method from a detected signal, and a FES switching processing circuit switching a-FES and d-FES, a control circuit controlling the FES switching processing circuit so that when a time at which focusing is started using a-FES is assumed to T1, after T1 a time at which seek is started during focusing is assumed to T2, switching from a-FES to d-FES is performed between T1 and T2, and a control circuit controlling the FES switching processing circuit so that after T2, when a time at which seek is finished during focusing is assumed to T3, and a time at which search is started again after T3 is assumed to T4, switching from d-FES to a-FES is performed between T3 and T4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that realizes stable focusing servo of an optical disc.

  As background art in this technical field, there is, for example, JP-A-4-168863. This publication states that "by correcting the cross noise component of the focus error signal generated from the reflected light of the second spot, the occurrence of cross noise can be suppressed and stable writing and reproduction characteristics can be realized." is there.

Japanese Laid-Open Patent Publication No. 4-168631

  Focusing servo is to control the focal position of the light beam so that it matches a predetermined data layer of the optical disk. A state in which the light beam is controlled so as to be in focus is referred to as focusing. In an optical disc apparatus, a differential astigmatism method (hereinafter referred to as DAD: Differential Astigmatic Detection) described in Patent Document 1 is generally used for optical disc focusing servo. The DAD is a detection method that is effective in reducing cross-track noise that occurs during the implementation of focusing, which is a problem of the astigmatism method (hereinafter referred to as AD).

  Searching for an in-focus position in a predetermined data layer of an optical disc is called search. Incidentally, in recent years, a dual-layer DVD having two data layers has been commercialized as a DVD (digital versatile disk). When DAD is used for focusing servo of an optical disc having a plurality of data layers such as the two-layer DVD, a focusing error signal (hereinafter referred to as FES) as if there is an in-focus position at a position other than the in-focus position of the data layer. : Focusing Error Signal) is output, making search difficult. If the search is difficult, focusing may be performed at a position other than the in-focus position. In this way, the fact that the focusing has been performed at a position other than the in-focus position is referred to as erroneous focusing. This also means that the success probability of a movement from a predetermined data layer to another data layer, that is, a so-called focusing jump is lowered, and the high-speed operation of the optical disc apparatus is lowered.

  Operating the optical pickup in the radial direction of the optical disk is called seek. When AD was used instead of DAD, we noticed a problem that an unpleasant sound was generated due to the high-speed fluctuation of the actuator due to the cross track noise generated in the FES during seeking. I also noticed a problem that focusing was lost when cross-track noise was high.

  An object of the present invention is to provide an optical disc apparatus that realizes stable focusing servo of an optical disc.

  The above object can be achieved by, for example, the configuration described in the claims.

  According to the present invention, it is possible to provide an optical disc apparatus that realizes stable focusing servo of an optical disc.

  In each embodiment of the present invention, an optical disk apparatus compatible with DVD recording or reproduction will be described as an example. Of course, each embodiment of the present invention can be applied to an optical disc such as a BD (Blu-ray disc) or a CD (compact disc).

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings, but the present invention is not limited thereby.

  Embodiment 1 of the present invention will be described in detail with reference to the drawings. Here, the focusing servo in the optical disc apparatus corresponding to the recording or reproduction of the dual-layer DVD-R will be described.

  FIG. 1 is a diagram showing an outline of a focusing servo of the optical disc apparatus according to the first embodiment. First, the optical pickup 001 provided in the optical disc apparatus will be described.

  A light beam is emitted from the laser light source 002 as divergent light. In order to record information on or reproduce information from a DVD, a semiconductor laser having a wavelength of about 660 nm is generally used, and the laser light source 002 also emits a light beam having a wavelength of about 660 nm. The path of the light beam emitted from the laser light source 002 is shown by a dotted line 003.

  The light beam emitted from the laser light source 002 enters the diffraction grating 004. The light beam is split into one main light beam and two sub light beams by the diffraction grating 004 (the path of the sub light beam is not shown). The two sub light beams are used for generating a tracking error signal (hereinafter TES) by differential push-pull (hereinafter DPP) and FES by DAD. In addition, since DPP and DAD are well-known techniques, description is abbreviate | omitted. The light beam that has passed through the diffraction grating 004 is reflected by the beam splitter 005 and focused on a predetermined data layer of the optical disk 008 by the objective lens 007 mounted on the actuator 006.

  The optical disk 008 swings in the direction of an arrow 025 due to surface deflection when rotating, and in the radial direction of the optical disk and in the direction of arrow 026 due to the eccentricity of the optical disk. Therefore, the actuator 005 has a function capable of being driven in the direction of the arrow 026 or the arrow 026. The optical disc apparatus can always follow the predetermined track of the predetermined data layer by performing feedback control of the actuator 005 based on the FES and TES. Further, since the optical disk 008 is assumed to be a two-layer DVD-R, there are two data layers. The data layer closer to the objective lens 007 is determined by the standard as Layer 0 (hereinafter referred to as L0) and the data layer far from the objective lens 007 is determined according to the standard.

  The light beam condensed on the optical disk 008 reflects the optical disk 008, passes through the objective lens 007, the beam splitter 005, and the detection lens 009, and reaches a photodetector 010 (hereinafter PD: Photo Detector). The detection lens 009 has a cylindrical lens surface, and the light beam is given a predetermined astigmatism when passing through the detection lens 009, thereby enabling detection of FES by AD or DAD. Since AD is a very common FES detection method, description thereof is omitted. The detection lens 009 has the function of determining the size of the light spot on the PD 010 while simultaneously rotating the direction of astigmatism in a predetermined direction. The light beam guided to the PD 010 is used for detection of an information signal recorded on the optical disc and detection of a servo signal of a light spot collected on the optical disc such as TES and FES.

  Next, circuit control of an optical disc apparatus that performs focusing servo using a detection signal detected from the optical pickup 001 will be described.

  The detection signal detected by the PD 010 is sent to the servo signal generation circuit 020. The servo signal generation circuit 020 generates two FES signals, that is, FES by AD (hereinafter a-FES) and FES by DAD (hereinafter d-FES) by a predetermined calculation. The a-FES and d-FES are sent to the FES switching processing circuit 021. The FES switching processing circuit 021 sends either an a-FES or a d-FES FES to the actuator drive circuit. Note that the FES switching processing circuit 021 has a function of switching between a-FES and d-FES based on a control signal from the control circuit 023. The FES output from the FES switching processing circuit 021 is sent to the actuator drive circuit 022. The actuator drive circuit 022 drives the actuator 006 in the optical pickup based on the selected FES.

  Next, control signals sent from the control circuit 023 to the FES switching processing circuit 021 will be described.

  First, a case where focusing is performed on L0 will be described. The control circuit 023 sends a control signal for selecting the a-FES to the FES switching processing circuit 021 in order to search for the in-focus position of L0. At the time of searching, the optical disc apparatus drives the objective lens 007 in the direction of arrow 025. After searching by driving the actuator 006, focusing is started at the in-focus position of L0. The time for starting this focusing is T1. After the focusing is started, the time when the seek is first started is T2. During seeking, the optical disk apparatus drives the optical pickup 001 in the direction of arrow 026. The control circuit 023 sends a control signal for switching from a-FES to d-FES to the servo signal switching processing circuit 021 between T1 and T2. In the optical disc apparatus, seek is started after switching to d-FES by the FES switching processing circuit 021.

  Next, a case where a focusing jump from L0 to L1 is performed will be described. At present, it is assumed that L0 is reproduced or recorded after T2. In other words, L0 focusing continues at d-FES. Let T3 be the time when the last seek at L0 is completed in the state where focusing is being performed at d-FES. After T3, in order to perform a focusing jump from L0 to L1, the focus position of L1 is searched. If the time for starting the search is T4, the control circuit 023 sends a control signal for switching from d-FES to a-FES between T3 and T4 to the FES switching processing circuit 021. That is, a-FES is used when searching for the in-focus position of L1. After the actuator 006 is driven and searched, focusing is started at the in-focus position of L1. The time for starting this focusing is T5. After starting focusing, the time for starting the first seek in the L1 layer is T6. The control circuit 023 sends a control signal for switching from a-FES to d-FES to the servo signal switching processing circuit 021 between T5 and T6. In the optical disc apparatus, seek is started after switching to d-FES by the FES switching processing circuit 021.

  T1 and T5 and T2 and T6 have the same meaning. In other words, in the present embodiment, the focusing jump and the seek can be realized stably by repeating T1, T2, T3, T4, T1, T2,.

  Next, with reference to FIGS. 2 and 3, it will be described that the above-described stable focusing servo can be realized by using this embodiment.

  FIG. 2 is a schematic diagram showing waveforms of a-FES and d-FES obtained during a search (driving the objective lens in a direction orthogonal to the optical disk). Here, from the left to the right in the figure, the objective lens coincides with the direction in which the objective lens approaches the optical disk from a direction far from the optical disk.

  First, a-FES will be described. When the objective lens is moved closer to the optical disk, the first S-shaped waveform 050 appears in the a-FES due to the L0 layer. The point where the S-shaped waveform 050 and the broken line intersect is the focal point position of L0. Cross-track noise occurs at the in-focus position of the a-FES. This cross track noise is generated in principle as disclosed in Patent Document 1 in the FES by AD.

  When the objective lens is further brought closer to the optical disc, an S-shaped waveform 051 appears in the a-FES from the L1 layer. The point where the S-shaped waveform 051 and the broken line intersect is the in-focus position of L1. Cross track noise also occurs at the in-focus position of L1. These cross-track noises cause the objective lens to vibrate greatly when seeking, causing noise from the optical disc apparatus and defocusing.

  Next, d-FES will be described. When the objective lens is brought closer to the optical disk, an S-shaped waveform that does not exist in the a-FES appears in the d-FES. There is no in-focus position on the optical disk at the appearance position of the S-shaped waveform. This is a so-called fake S-shaped waveform, and this fake S-shaped waveform is hereinafter referred to as overshoot. The reason for this overshoot will be described below. When the objective lens is subsequently moved closer to the optical disk, an S-shaped waveform 052 appears due to the L0 layer. The point where the S-shaped waveform 052 intersects with the broken line is the focal point position of L0. Cross track noise does not occur at the in-focus position of d-FES. DAD is a technology developed for the purpose of optically removing cross-track noise by using a sub light beam.

  When the objective lens is further brought closer to the optical disk, overshoot appears again in the d-FES between the L0 layer and L1. When the objective lens is further brought closer to the optical disk, an S-shaped waveform 053 from the L1 layer appears. The point where the S-shaped waveform 053 and the broken line intersect is the in-focus position of L1. No cross track noise occurs at the in-focus position of L1. Furthermore, when the objective lens is brought closer to the optical disk, a third overshoot occurs. In the d-FES, as shown in the figure, three overshoots occur at positions other than the L0 and L1 layers, so that erroneous focusing is likely to occur. Once erroneous focusing occurs, the driving position of the objective lens is unclear in the optical disc apparatus, so the focusing servo must be retried, and time loss is a problem.

  As described above, in a conventional optical disk apparatus that uses only one of a-FES and d-FES for each optical disk, either cross-track noise or overshoot has been a problem. In the present embodiment, as described with reference to FIG. 1, since a-FES and d-FES are switched at the above timing, both cross-track noise and overshoot can be avoided.

  FIG. 3 is a schematic view showing a-FES and d-FES during focusing servo control, and waveforms of the FES and actuator drive voltage in this embodiment. Here, the effect of this embodiment at the time of focusing servo control will be specifically described with reference to FIG.

  FIG. 3 shows a-FES, d-FES, FES of this embodiment, and actuator drive voltage from the top. In a-FES, d-FES, and FES in this embodiment, the vertical axis represents the FES amplitude, the horizontal axis represents time, the vertical axis of the actuator drive voltage represents the drive voltage, and the horizontal axis represents time. FIG. 3 shows an example in which focusing is performed on a predetermined layer so that it can be easily explained.

  The actuator drive voltage is increased while monitoring the FES waveform from time T0. As the actuator drive voltage is increased, the objective lens approaches the optical disk. Since the FES of this embodiment uses a-FES at first, the same waveform as that of a-FES appears. The amplitude of the FES gradually decreases as a predetermined layer approaches the in-focus position, and then increases gradually over the minimum value. Focusing is triggered by the timing at which this minimum value is detected. The time when the focusing is started is T1.

  From T1, the actuator drive voltage is feedback-controlled by a signal from the FES so that the predetermined layer is always at the in-focus position Vo. By this operation, the focal position can follow the surface vibration of the optical disc. After starting the focusing, a large cross track noise is generated in the a-FES. Similarly, since a large amount of cross track noise is also generated in the FES of the present embodiment, the fluctuation range of the actuator drive voltage becomes very large. Usually, when the cross track noise leaks into the FES as described above, the problem of the sound at the time of seek and the FES detachment as described above occurs.

  The time for the first seek after the start of focusing is T2. In this embodiment, the a-FES is switched to the d-FES between T1 and T2. When switching from a-FES to d-FES, the FES of the present embodiment reduces the occurrence of cross-track noise, and the amplitude of the actuator drive voltage also decreases. For this reason, it is possible to avoid the problem that sound and focusing are lost by seeking after the time T2.

  The time when the last seek in the predetermined data layer is finished in the optical disk apparatus is T3. Thereafter, in order to perform a focusing jump to another data layer, when the time for starting the search for the in-focus position in the other data layer is set to T4 in order to make the focus jump to another data layer, in the FES of this embodiment, T3 and T4 In the meantime, switch from d-FES to a-FES. The search uses a-FES. In d-FES, since a trigger for starting focusing is detected in an overshoot area other than the predetermined data layer, the focusing servo is erroneously started in the overshoot area. Switching is performed so that the in-focus position of the data layer to be reproduced next is not mistaken.

  In other words, as described above, the search uses a-FES, and if the signal is switched to a-FES when starting focusing, erroneous focusing due to overshoot can be avoided, and even when seeking is performed during focusing, crossing is also possible. Smooth seek can be realized because there is almost no track noise. In other words, the present embodiment is devised so that a-FES has no overshoot and it is easy to search the L0 and L1 layers, and d-FES can have both the advantage of smooth seek without cross-track noise. It is something that is elaborate.

  Note that, by repeatedly using the focusing servo control described in FIG. 3 in other data layers, stable focusing servo can be realized in any data layer.

  In FIG. 3, the switching from the a-FES to the d-FES is performed immediately before T2, but of course, there is no problem if the switching is performed anywhere between T1 and T2. Further, although switching from d-FES to a-FESh is performed immediately after T3, of course, there is no problem if switching is performed anywhere between T3 and T4.

  Further, the trigger for starting the focusing is described immediately after the minimum value of FES, and the time T4 for starting the search is described immediately after the maximum value of FES. However, the present invention is not limited to this figure. It does not matter if the trigger to start or the time T4 for starting the search is brought to the in-focus position.

  In the second embodiment, a means for performing the switching process described in the first embodiment more smoothly will be described.

  FIG. 4 illustrates processing for matching the focusing servo gains of the a-FES and the d-FES generated from the servo signal generation processing circuit.

  The a-FES and d-FES generated from the servo signal generation circuit 020 are sent to the maximum / minimum detection circuit 030. The maximum / minimum detection circuit 030 is a comparator that detects each minimum value and each maximum value of a-FES and d-FES, and a signal generated by the maximum / minimum detection circuit 030 is sent to the control circuit 023. A-FES and d-FES amplitude information is obtained from the detected maximum and minimum values. The control circuit 023 has a function of comparing the amplitudes of a-FES and d-FES from the signal generated by the maximum / minimum detection circuit 030 and sending the amplitude ratio (K2) to the gain correction circuit 031 as a signal. The gain correction circuit multiplies the amplitude of a-FES by K2 in accordance with the amplitude ratio. By this control, the amplitudes of a-FES and d-FES can be matched. The control of the gain correction circuit is preferably performed before the time T1.

  The FES detection range is obtained by converting the interval between the maximum value and the minimum value of the FES into the surface shake direction of the optical disc, and the FES detection range corresponds to an error in the surface shake direction of the optical disc. The FES detection range in a normal AS is about 4 to 7 μm. The FES detection range and amplitude are parameters that determine how much actuator drive voltage is applied, but the detection range of d-FES and a-FES is the same, but the amplitude is nearly double, so the actuator drive voltage also changes. End up. If the actuator drive voltage is not changed in spite of the reduced amplitude, for example, in d-FES, applying a drive voltage to the actuator so as to deviate from the in-focus position by 2 μm The actuator driving voltage corresponds to a deviation from the 4 μm sign focal position. For example, when the FES detection range is 4 μm, the focus is deviated from the focal position.

  As described above, when the gain correction circuit is controlled in the previous stage (time before time T1) of the FES switching processing circuit. The sensitivity of the actuator voltage can be prevented from changing from the moment when the d-FES and the a-FES are switched, and it is possible to avoid the loss of focusing at the moment of switching.

  Note that, for example, the actuator driving voltage can be reduced by K2 when the signal is switched between a-FES and d-FES. However, when switching is performed a plurality of times in a multilayer disk or the like, the servo gain must also be switched each time the a-FES and d-FES are switched. If the gain correction circuit is arranged in the previous stage as described in the second embodiment, once the gain correction circuit 031 is driven, it is not necessary to switch the servo gain each time the a-FES and d-FES are switched. The effect is obtained.

  In this embodiment, the configuration is such that the amplitude of the a-FES is corrected. Of course, a configuration in which the amplitude of the d-FES is corrected, and a configuration in which both the amplitudes of the a-FES and d-FES are corrected may be used.

  In the third embodiment, a PD that generates a-FES and d-FES and a servo signal generation circuit will be described.

  FIG. 5 is a schematic diagram of a PD and a servo signal generation circuit.

  First, the PD will be described. The PD has three detection areas 500, 501, and 502. The detection area 500 includes four detection surfaces A, B, C, and D. The detection area 501 includes detection surfaces E1, E2, E3, and E4. The detection area 502 includes detection surfaces F1, F2, F3, and F4. The detection region 500 is irradiated with the main light beam, and the detection regions 501 and 502 are irradiated with the sub light beam. The current detected from each detection surface of the detection region 500 is converted into a voltage by an I / V converter (black triangle in the figure) and then sent to a servo signal generation circuit.

The currents detected from the detection surfaces E1 and F1 are added by an adder 503, converted to a voltage by an I / V converter (black triangles in the figure), and then sent to a servo signal generation circuit.
The currents detected from the detection surfaces E2 and F2 are added by an adder 504, converted to a voltage by an I / V converter (black triangles in the figure), and then sent to a servo signal generation circuit.
The currents detected from the detection surfaces E3 and F3 are added by an adder 505, converted to a voltage by an I / V converter (black triangles in the figure), and then sent to a servo signal generation circuit.
The currents detected from the detection surfaces E4 and F4 are added by an adder 503, converted to a voltage by an I / V converter (black triangles in the figure), and then sent to a servo signal generation circuit.

  In the PD of FIG. 5, the number of output pins to the outside is reduced by internally connecting the detection surfaces E1, F1, and the like.

  Next, the servo signal generation circuit will be described. As for the signal from each detection surface of the PD, for example, the output signal from the detection surface A is hereinafter referred to as A, and the output signal obtained by adding the detection surfaces E1 and F1 is referred to as EF1.

  A and C detected from the PD are added by an adder 507, and B and D are added by an adder 508. The output signals from the adders 507 and 508 are subtracted by the differential 509 to generate a-FES.

  EF1 and EF3 detected from the PD are added by an adder 510, and EF2 and EF3 are added by an adder 511. Next, the output signals from the adders 510 and 511 are subtracted by the differential unit 512 and multiplied by K1 by the coefficient unit 513. K1 is a coefficient for correcting the power ratio between the main light beam and the sub light beam. The output signals from the differential unit 509 and the coefficient unit 513 are subtracted by the differential unit 514 to generate d-FES.

  As described above, a-FES and d-FES can be generated by a general addition, subtraction, and multiplication circuit from a detection signal from a conventional PD.

  In the fourth embodiment, a mechanism in which overshoot occurs in d-FES will be described.

  FIG. 6 is a diagram showing the behavior of the main light beam on the PD when the objective lens is brought closer to the optical disc from the in-focus position. (A) is in-focus position, (B) is close to the optical disk from the in-focus position, and when a-FES takes the maximum value, (C) is further objective until the a-FES signal becomes about zero. This is the main light beam 700 on the PD when the lens is brought close to the optical disk.

As shown in FIG. 6A, the main light beam 700 has the same power on the detection surfaces A, B, C, and D and has a round shape when it is at the in-focus position indicated by the waveform of a-FES. When the objective lens is brought close to the optical disc from the in-focus position and a-FES takes the maximum value, the main light beam 700 has the maximum power of the detection surfaces A and C as shown in FIG. Conversely, the detection surfaces B and D have almost no power. When the objective lens is further raised to a point where the a-FES signal becomes approximately zero, the main light beam 700 becomes largely blurred as shown in FIG. Since the detection surfaces A, B, C, and D are evenly incident, the a-FES is approximately zero. Since the main light beam 700 is greatly blurred, it enters the detection surfaces E2 and F4. At this time, the main light beam 700 is considerably deviated from the in-focus position, and thus has defocus aberration and astigmatism, so that there is a difference in power incident on E2 and F4. This power difference causes an overshoot. Although the power of the main light beam entering E2 and F4 is small, it is multiplied by K1 by the servo signal generation circuit, so that the overshoot that occurs is so large that it cannot be ignored.
This is because, in general, the power of the sub light beam is reduced with respect to the main light beam, for example, in order to prevent the sub light beam from recording the optical disk during recording. In a general optical disc apparatus, the power ratio of the main light beam to the sub light beam is about 10: 1 to 20: 1. For this reason, the output signal obtained from the sub light beam is multiplied by K1 as described in the third embodiment.

  This overshoot also occurs in a single-layer optical disc. The present embodiment is not limited to a multi-layer optical disc, and can also be used for a single-layer optical disc. For example, when this embodiment is used for a DVD-RAM with a Land / Groove structure and a large amount of cross track noise, it is possible to avoid a smooth seek that is not affected by the cross track noise and erroneous focusing due to overshoot, and to be stable. A focusing servo can be realized.

  In the fifth embodiment, an optical disk device 300 on which an optical pickup 001 is mounted will be described. FIG. 7 shows a schematic block diagram of an optical disc apparatus 300 on which an optical pickup 001 is mounted. A signal detected from the optical pickup 001 is sent to a servo signal generation circuit 020, a front monitor circuit 309, and an information signal reproduction circuit 310 provided in the optical disc apparatus 300. The servo signal generation circuit 020 detects TES, a-FES, and d-FES suitable for each optical disc from the detection signal of the optical pickup. The detected a-FES and d-FES are sent to the maximum / minimum detection circuit 030, and detection signals of the maximum and minimum values of the a-FES and d-FES are sent to the control circuit 023. The control circuit 023 detects the amplitude ratio of each amplitude from the maximum value and the minimum value, and drives the gain correction circuit 031 so that the amplitude ratio is equal. The gain correction circuit 031 multiplies a-FES or d-FES based on the control signal sent from the control circuit 023 and sends each FES to the FES switching processing circuit 031. The FES switching circuit receives the above-described command from the control circuit 023, switches between a-FES and d-FES, and sends the selected FES to the actuator drive circuit 022 to drive the objective lens actuator in the optical pickup 100 for focusing. I do. The TES is sent to the control circuit 023, and the control circuit 023 drives the actuator driving circuit 022 based on the TES to perform tracking as necessary.

  The front monitor circuit 309 detects the power monitor signal of the laser light source from the detection signal from the front monitor, and drives the laser light source control circuit 303 based on this to control the power on the optical disc 008 accurately. The information signal reproduction circuit 310 reproduces the information signal recorded on the optical disc 008 from the detection signal, and the information signal is output to the information signal output terminal 310.

  When recording information is input from the recording information input terminal 312, the recording information signal conversion circuit 312 converts the recording information into a predetermined laser driving recording signal. The recording signal for driving the laser is sent to the control circuit 023, and the laser light source control circuit 303 is driven to control the power of the laser light source, and the recording signal is recorded on the optical disc 008. A seek control circuit 302 and a spindle motor drive circuit 301 are connected to the control circuit 023, and position control of the optical pickup 001 in the seek direction and rotation control of the spindle motor 314 of the optical disk 008 are performed.

FIG. 3 is a diagram illustrating a focusing servo of the optical disc apparatus according to the first embodiment. Schematic showing waveforms of a-FES and a-FES in Example 1 The figure which showed the relationship between FES and an actuator drive voltage in Example 1. FIG. 10 illustrates a process for matching the focusing servo gains of the a-FES and the d-FES generated from the servo signal generation processing circuit according to the second embodiment. FIG. 6 is a diagram for explaining a PD and a servo signal generation circuit according to a third embodiment. The figure which showed the behavior of the main light beam on PD in Example 4 FIG. 10 is a diagram for explaining processing of an optical disc device according to a fifth embodiment.

Explanation of symbols

001: Optical pickup, 300: Optical disk device, 020: Servo signal generation circuit, 021 ... FES switching processing circuit, 022 ... Actuator drive circuit, 023 ... Control circuit

Claims (8)

An optical pickup for detecting a signal from the optical disc;
A servo signal generation circuit that generates a first focusing error signal and a second focusing error signal from a detection signal detected by the optical pickup;
An optical disc apparatus comprising a focusing error signal switching processing circuit for switching between the first and second focusing error signals,
Search for the focal point position of the optical disc using the first focusing error signal, and T1 is a time for starting focusing to the focal point position based on the search result,
After T1, when the time to start driving the optical pickup in the radial direction of the optical disk during the focusing is set to T2,
A control circuit for controlling the focusing error signal switching processing circuit so that a focusing error signal used between T1 and T2 is switched from the first focusing error signal to the second focusing error signal; An optical disc apparatus characterized by the above. An optical pickup for detecting a signal from the optical disc, a servo signal generating circuit for generating a first focusing error signal and a second focusing error signal from the detection signal detected by the optical pickup, and the first and second In an optical disc apparatus comprising a focusing error signal switching processing circuit for switching with a focusing error signal of
T3 is a time when driving of the optical pickup in the radial direction of the optical disc is finished during the focusing using the second focusing error signal.
After T3, when the time to start searching for the in-focus position of the optical disc again is T4,
A control circuit for controlling the focusing error signal switching processing circuit so that a focusing error signal used between T3 and T4 is switched from the second focusing error signal to the first focusing error signal; An optical disc apparatus characterized by the above. An optical pickup for detecting a signal from the optical disc, a servo signal generating circuit for generating a first focusing error signal and a second focusing error signal from the detection signal detected by the optical pickup, and the first and second In an optical disc apparatus comprising a focusing error signal switching processing circuit for switching a focusing error signal of
Search for the focal point position of the optical disc using the first focusing error signal, and T1 is a time for starting focusing to the focal point position based on the search result,
After T1, the time to start driving the optical pickup in the radial direction of the optical disc during the focusing is T2,
A control circuit for controlling the focusing error signal switching processing circuit so as to switch a focusing error signal used between T1 and T2 from the first focusing error signal to the second focusing error signal;
After T2, the time when the optical pickup has been driven in the radial direction of the optical disc during the focusing using the second focusing error signal is defined as T3.
After T3, when the time to start searching for the in-focus position of the optical disc again is T4,
A control circuit for controlling the focusing error signal switching processing circuit so that a focusing error signal used between T3 and T4 is switched from the second focusing error signal to the first focusing error signal; An optical disc apparatus characterized by the above. The optical disk apparatus according to claim 1, wherein
An optical disk device includes a laser light source, a diffraction grating that branches a light beam emitted from the laser light source into at least three light beams, a main light beam and two sub light beams, and the three light beams to the optical disk. An objective lens for condensing each of the three light beams independently, an optical component for giving a predetermined astigmatism to the reflected light beam of the three light beams from the optical disc, and the three light beams A photodetector having at least three light receiving areas for receiving three reflected light beams from the optical disc,
An optical disc apparatus comprising an optical pickup for outputting a detection signal necessary for a focusing error signal by an astigmatism method from each light receiving region of the photodetector for receiving the three light beams. The optical disc apparatus according to claim 4, wherein
The servo signal generation circuit includes the first focusing error signal by the astigmatism method generated by a predetermined calculation from a signal detected from the light receiving region that receives the main light beam, the main light beam, and two sub-lights. An optical disc apparatus, wherein the second focusing error signal is generated by a differential astigmatism method generated by a predetermined calculation from a signal detected from each light receiving region that receives a light beam. The optical disc apparatus according to claim 5, wherein
The optical disc apparatus includes a maximum / minimum detection circuit that detects the maximum value and the minimum value of the first and second focusing error signals, and a gain correction circuit that multiplies the first or second focusing error signal by a coefficient. ,
The amplitudes of the first and second focusing error signals are compared from the maximum and minimum values of the first and second focusing error signals detected from the maximum / minimum detection circuit, and the amplitude ratio of the amplitudes is 1. An optical disc apparatus comprising: a control circuit for controlling the gain correction circuit to multiply the first or second focusing error signal by a coefficient. The optical disc apparatus according to claim 6, wherein
The optical disk apparatus according to claim 1, wherein the gain correction circuit is arranged in a stage preceding the focusing error signal switching processing circuit. An optical pickup for detecting a signal from the optical disc;
A servo signal generation circuit that generates a first focusing error signal and a second focusing error signal from a detection signal detected by the optical pickup;
A controller for controlling the focus by switching the first and second focusing error signals;
An optical disc device comprising:

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