JP2005276257A - Optical disk device and its focus search method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device capable of shortening focus search time and preventing the collision of an objective lens with the recording surface of an optical disk while flexibly dealing with the displacement of the recording surface of an optical disk from a reference plane according to the radial direction position of the optical disk, and its focus search method. <P>SOLUTION: This device comprises a measuring means 15 for measuring the displacing amount of the recording surface of an optical disk from a reference surface according to the radial direction position of the optical disk 3 during the reproducing or recording thereof; and a correcting means 17 for correcting a driving signal supplied to a moving means 8 for focus search performed again after the reproducing or recording based on the displacing amount of the recording surface of the optical disk 3 from the reference surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus and a focus search method thereof, and in particular, by supplying a drive signal to an objective lens moving means in an optical pickup, the objective lens is moved in a direction orthogonal to the optical disc to perform a focus search. The present invention relates to an optical disc apparatus suitable for performing the same and a focus search method thereof.

  2. Description of the Related Art Conventionally, an optical disc apparatus that reproduces or records an optical disc using an optical pickup equipped with an objective lens has been adopted as a means for reproducing information recorded on an optical disc such as a CD or DVD and recording information on the optical disc. It was.

  In such an optical disc apparatus, when the optical disc is reproduced or recorded, the focused spot of the laser beam from the optical pickup focused through the objective lens is just focused on the recording surface of the optical disc. In other words, focus servo is performed to maintain the distance of the objective lens with respect to the optical disk.

  However, the range in which this focus servo is possible is limited to a very narrow range of about ± 20 μm in the direction perpendicular to the recording surface of the optical disc from the just focus position.

  For this reason, before reproduction or recording, a position where focus servo loop, which is a mechanism for performing focus servo, is turned off and where focus servo can be performed (hereinafter referred to as “focus retractable position”) will be described. ) Until the objective lens is moved, and then the focus servo loop is turned on to execute the focus servo. As a start-up process for reproduction or recording operation, focus search and focus servo are executed, and then spindle servo and tracking servo are executed. When the start-up process is completed, scanning for reproduction or recording with a condensing spot condensed through the objective lens becomes possible.

  Here, FIG. 8 shows an example of the above-described focus search. As shown in FIG. 8, when performing the focus search, the objective lens is moved in a direction orthogonal to the recording surface of the optical disk. A drive signal such as a drive voltage is supplied to a moving means such as an actuator.

  When this drive signal is changed up and down as shown in FIG. 8, the moving means moves the objective lens so as to approach or separate from the recording surface of the optical disk. Such supply of the drive signal is repeated until a focus retractable position is detected.

  At this time, a standard for detecting the focus retractable position is to detect the S-shaped waveform S of the focus error signal as shown in FIG.

  The focus error signal is a signal obtained by detecting reflected light from the optical disk that changes with the focus search operation of the objective lens by, for example, an astigmatism method using a cylindrical lens.

  In such a focus search, in order to detect a focus retractable position, the focus retractable position must exist within the movement range of the objective lens.

  However, the recording surface of the optical disc is not a perfect plane, but has a displacement from the reference plane according to its radial position due to various error factors. The error factors include the optical disc surface runout, the runout of the turntable of the optical disc apparatus for mounting the optical disc, the turntable height variation, the skew gear variation in the turntable rotation mechanism, or the movement means. Variations in drive sensitivity can be considered.

  Here, the “reference plane” refers to an ideal plane formed by the recording surface of the optical disc on the assumption that there are no various error factors described above (hereinafter the same). When the recording surface of the optical disc is a reference plane, the objective lens can take a certain distance from the recording surface regardless of the radial position of the optical disc.

  Therefore, when performing a focus search, the amplitude of the drive signal supplied to the moving means is sufficiently large in order to reliably detect the focus retractable position regardless of the displacement of the recording surface of the optical disc from the reference plane. It was necessary to set.

  As a result, conventionally, it is necessary to perform a useless search by moving the objective lens to a position outside the vicinity of the focus retractable position, and the time from the start of the focus search to the start of the focus servo becomes longer. It was.

  In addition, even when the distance between the recording surface of the optical disk and the objective lens is closer than the other position in the radial direction of the optical disk, the movement range of the objective lens is the same as the other positions. Therefore, the objective lens may collide with the optical disc, and at least one of the objective lens and the optical disc may be damaged.

  Therefore, various proposals for restricting the movement range of the objective lens during the focus search have been made so far in order to solve such a problem.

  For example, in the invention described in Patent Document 1, information on the focus servo-on time when the focus search is performed is stored in the memory, and the information stored in the memory is referred to at the next focus search. Thus, the focus search is performed near the lens position where the focus servo is turned on.

  In the invention described in Patent Document 2, the radius area of the disc is divided into an inner peripheral side and an outer peripheral side in advance, and the focus search range is widened on the outer peripheral side.

JP-A-6-301986 JP 2002-170250 A

  However, in the invention described in Patent Document 1, although it is described that the focus search is performed in the vicinity of the focus servo on point, from the reference plane of the recording surface of the optical disc corresponding to the radial position of the optical disc described above. There is no description or suggestion of a specific means for solving the problem associated with the displacement of.

  In the invention described in Patent Document 2, since the focus search range is fixedly set to be narrow on the inner peripheral side of the optical disc and wide on the outer peripheral side, the recording surface of the optical disc is, for example, the inner peripheral side. In the case of displacement so that the distance from the objective lens becomes larger toward the side, it is not possible to cope with it at all.

  Therefore, conventionally, various problems associated with the displacement of the recording surface of the optical disc from the reference plane in accordance with the radial position of the optical disc due to warpage of the optical disc, that is, the focus servo start delay problem and the objective lens In fact, no effective proposal has been made to solve the problem of collision between the optical disk and the recording surface of the optical disk.

  Therefore, the present invention has been made in view of such a problem, and at the time of focus search while flexibly dealing with the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc. By stopping the movement range of the objective lens to the minimum necessary range, the time required for the focus search can be shortened, and the collision between the objective lens and the recording surface of the optical disk can be avoided in advance. And a focus search method thereof.

  In order to achieve the above-described object, the optical disk apparatus according to the present invention is characterized by including a moving means for moving the objective lens of the optical pickup along a direction orthogonal to the recording surface of the optical disk by supplying a drive signal. An optical disc apparatus for performing a focus search while moving the objective lens by the moving means before performing reproduction or recording, wherein the optical disc according to a radial position of the optical disc during reproduction or recording of the optical disc Measuring means for measuring the amount of displacement of the recording surface from the reference plane, and a drive signal supplied to the moving means for the focus search when performing a focus search again after the reproduction or recording, And a correction means for correcting based on the amount of displacement of the recording surface from the reference plane. That.

  According to such a configuration, when the optical disc is played back or recorded, the amount of displacement from the reference plane of the recording surface of the optical disc according to the radial position of the optical disc, such as warpage of the optical disc, is measured by the measuring means. In the case where the focus search is performed again after reproduction or recording by the correction means, the drive signal supplied to the movement means for the focus search is displaced from the reference plane of the recording surface of the optical disc. Correction can be made based on the amount.

  As a result, regardless of the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc, it is possible to set the movement range of the objective lens in the focus search that flexibly corresponds to the displacement. It becomes possible.

  In the present application, “reproduction or recording” does not mean only a case where information on an optical disc is actually output as sound or an image, or a state where information is written to the optical disc.

  For example, in an optical disk device corresponding to a recent multi-session optical disk, when the optical disk is set on a turntable, the entire lead-in area is first read in order to examine the structure of the optical disk. Such an operation can be executed only after a just focus state (focus servo on) is obtained, and such an operation is also included in “reproduction”. In addition, an operation for detecting a writable area of the optical disc after the just focus is obtained is included in the “recording”. Needless to say, the focus servo is continued during the reproduction or recording operation.

  The optical disc apparatus according to the present invention is characterized in that the measuring means measures the amount of displacement from the reference plane of the recording surface of the optical disc based on the low frequency component of the drive signal during reproduction or recording.

  And according to such a structure, it becomes possible to measure reliably the displacement amount from the reference plane of the recording surface of an optical disk with a simple structure.

  Further, the optical disc apparatus according to the present invention is characterized in that the correction means corrects the drive signal based on the amount of displacement from the reference plane of the recording surface of the optical disc with respect to the focus search profile for performing the focus search. The point is to correct.

  And according to such a structure, it becomes possible to correct | amend the drive signal at the time of a refocus search appropriately with a simple structure.

  Furthermore, the focus search method of the optical disc apparatus according to the present invention is characterized in that a drive signal is supplied to a moving means that moves the objective lens of the optical pickup in a direction perpendicular to the recording surface of the optical disc by supplying the drive signal. Thus, the focus search method of the optical disc apparatus for performing the focus search by moving the objective lens by the moving means before performing the reproduction or recording of the optical disc, The drive supplied to the moving means for the focus search when measuring the amount of displacement from the reference plane of the recording surface of the optical disc according to the position in the radial direction and performing the focus search again after the reproduction or recording The signal is based on the amount of displacement of the recording surface of the optical disc from the reference plane. Stomach lies in the fact that correction.

  According to such a method, no matter what displacement the recording surface of the optical disc has from the reference plane according to the radial position of the optical disc, the objective lens in the focus search that flexibly corresponds to the displacement can be used. It is possible to set the movement range.

  Also, the focus search method of the optical disc apparatus according to the present invention is characterized in that the amount of displacement from the reference plane of the recording surface of the optical disc is measured based on the low frequency component of the drive signal during reproduction or recording.

  According to such a method, it is possible to reliably measure the amount of displacement of the recording surface of the optical disc from the reference plane by a simple method.

  Furthermore, the focus search method of the optical disc apparatus according to the present invention is characterized in that a drive signal is obtained by correcting a focus search profile for performing a focus search in accordance with the amount of displacement from the reference plane of the recording surface of the optical disc. The point is to correct.

  And according to such a method, it becomes possible to correct | amend the drive signal at the time of a refocus search appropriately by a simple method.

  According to the optical disc device of the present invention, the time required for the focus search can be shortened to flexibly cope with the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc, and the optical disc reproducing operation or The recording operation can be started quickly, and the product life can be improved by effectively avoiding the collision between the objective lens and the recording surface of the optical disk.

  Further, according to the optical disc apparatus of the present invention, the optical disc is provided with the measuring means for measuring the displacement amount of the recording surface of the optical disc from the reference plane based on the low frequency component of the drive signal at the time of reproduction or recording. The focus search time can be shortened more efficiently and inexpensively while flexibly responding to the displacement of the recording surface of the optical disc from the reference plane according to the position in the radial direction of the objective lens and the recording surface of the optical disc. Can be avoided in advance.

  Furthermore, according to the optical disc apparatus of the present invention, the correction means for correcting the drive signal by correcting the focus search profile for performing the focus search according to the amount of displacement from the reference plane of the recording surface of the optical disc. From the start of the focus search to the start of the focus servo more efficiently and cheaply while flexibly responding to the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc. The time can be shortened and the collision between the objective lens and the recording surface of the optical disk can be avoided in advance.

  Furthermore, according to the focus search method of the optical disc apparatus according to the present invention, the time required for the focus search is reduced while flexibly responding to the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc. Thus, the reproducing operation or recording operation of the optical disc can be started quickly, and further, the collision between the objective lens and the recording surface of the optical disc can be avoided in advance and the product life of the optical disc apparatus can be improved.

  Further, according to the focus search method of the optical disc apparatus according to the present invention, the amount of displacement of the recording surface of the optical disc from the reference plane is measured based on the low frequency component of the drive signal at the time of reproduction or recording. The focus search time can be shortened more efficiently and inexpensively while flexibly responding to the displacement of the recording surface of the optical disc from the reference plane according to the position in the radial direction, and the objective lens and the recording surface of the optical disc Can be effectively avoided.

  Further, according to the focus search method of the optical disc apparatus according to the present invention, the drive signal is corrected by correcting the focus search profile for performing the focus search according to the amount of displacement from the reference plane of the recording surface of the optical disc. As a result, the time from the start of the focus search to the start of the focus servo can be more efficiently and inexpensively while flexibly responding to the displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc. Thus, the collision between the objective lens and the recording surface of the optical disk can be avoided in advance.

  Embodiments of an optical disc apparatus according to the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, the optical disc apparatus 1 in this embodiment has a turntable 2, and an optical disc 3 such as a CD or a DVD is mounted on the turntable 2.

  Further, the optical disc apparatus 1 has an optical pickup 5 provided with an objective lens 4 at a position facing the recording surface of the optical disc 3. The optical pickup 5 reproduces information recorded on the optical disc 3 by irradiating the recording surface of the optical disc 3 with laser light and detecting reflected light from the recording surface of the laser light. ing.

The optical pickup 5 is provided with a four-divided photodiode 7 composed of D _{A to} D _D as an element that receives reflected light from the recording surface of the optical disc 3. Of the 4 division photodiode 7, D _A and A D _C, are connected in parallel with each other, these D _A and D _C is adapted to output (A + C) signal by receiving the reflected light ing. Furthermore, 4 of the divided photodiode 7, the D _B and D _D, are connected in parallel to each other, these D _B and D _D, by receiving the reflected light, to output the (B + D) signal It has become.

Here, in the just focus state, as shown in FIG. 2A, the reflected light is equally applied to D _{A to} D _D of the four-division photodiode 7. On the other hand, when the laser beam spot is too far from the signal surface, the reflected light strikes the number D _A and D _C as shown in FIG. 2 (b), strikes less in D _B and D _D. Further, when the laser beam spot is too close to the signal surface is reflected light strikes the number D _B and D _D As shown in FIG. 2 (c), strikes less the D _A and D _C. Therefore, (A + C) − (B + D) indicates an error between the focal point of the laser light spot and the signal surface.

  Returning to FIG. 1, the optical pickup 5 is provided with a moving means 8 for the objective lens 4 such as an actuator. The moving means 8 moves the objective lens 4 to the recording surface of the optical disc 3 by supplying a drive signal. It is made to move along a direction orthogonal to the direction.

  An RF amplifier 9 is connected to the output side of the optical pickup 5, and the signal from the four-division photodiode 7, that is, the above-described (A + C) signal and (B + D) signal are input to this RF amplifier 9. It has come to be.

  The RF amplifier 9 creates a focus error signal FE by individually converting the input (A + C) signal and (B + D) signal into current-voltage, and also adds the (A + C) signal and the (B + D) signal. A signal is generated and the focus error signal and the sum signal are output.

  A focus servo circuit 11 is connected to the output side of the RF amplifier 9, and the focus error signal FE and the sum signal output from the RF amplifier 9 are input to the focus servo circuit 11. .

  The focus servo circuit 11 outputs a focus servo signal for performing focus servo based on the input of the focus error signal FE.

  A focus servo driver 12 is connected to the output side of the focus servo circuit 11, and the focus servo driver 12 amplifies the focus servo signal output from the focus servo circuit 11 to drive the focus servo drive signal ( Hereinafter, it is output to the moving means 8 as a “focus servo drive signal”.

  A focus servo loop for performing focus servo is formed by the elements of the optical pickup 5, the RF amplifier 9, the focus servo circuit 11, and the focus servo driver 12, and this focus servo loop is turned on or off. The servo circuit 11 is used.

  When the focus servo loop is off, a focus search signal for performing a focus search is output from the focus servo circuit 11 to the focus servo driver 12. At this time, the focus servo driver 12 amplifies the focus search signal and outputs it to the moving means 8 as a drive signal for focus search (hereinafter referred to as “focus search drive signal”).

  A servo controller 13 is connected to the focus servo circuit 11, and the servo controller 13 manages a focus search profile for performing a focus search.

  The servo controller 13 controls the focus servo circuit 11 according to the focus search profile, such as setting the amplitude of the focus search signal during the focus search.

  In the present embodiment, the servo controller 13 is a measurement unit that measures the amount of displacement of the recording surface of the optical disc from the reference plane according to the radial position of the optical disc 3 when the optical disc 3 is played back. Part 15.

  When the optical disk 3 is reproduced, the measuring unit 15 receives a focus servo drive signal and reproduction address information of the optical disk.

  Then, the measurement unit 15 determines from the reference plane of the recording surface of the optical disc 3 according to the radial position of the optical disc 3 based on the low frequency component of the input focus servo drive signal and the reproduction address information of the optical disc. The displacement is measured.

  More specifically, the measurement unit 15 obtains the displacement amount from the reference plane of the recording surface of the optical disc 3 from the low frequency component of the focus servo drive signal, and the radial position information of the optical disc 3 from the reproduction address information of the optical disc 3. Is obtained, the amount of displacement from the reference plane of the optical disc 3 corresponding to each position in the radial direction of the optical disc 3 is measured.

  By measuring the amount of displacement of the recording surface of the optical disk 3 from the reference plane (hereinafter, abbreviated as “the amount of displacement of the optical disk 3”) by the measuring unit 15, surface deflection such as warpage of the optical disk 3 and the surface of the turntable 2 Various errors such as fluctuation, variation in the height of the turntable 2, variation in skew gear in the rotation mechanism of the turntable 2, variation in driving sensitivity of the moving means 8, and the like are quantitatively detected.

  The displacement amount of the optical disk 3 may be measured based on the low frequency component of the focus servo signal instead of the low frequency component of the focus servo drive signal. As described above, since the focus servo signal is a signal that can be converted into the focus servo drive signal by amplifying the focus servo signal by the focus servo driver 12, the displacement of the waveform similar to that of the focus servo drive signal is detected. Because it can be done.

  The displacement amount of the optical disc 3 measured by the measuring unit 15 is stored in a memory 16 connected to the servo controller 13 in a state of having a correspondence relationship with the radial position information of the optical disc 3. .

  In addition, the servo controller 13 has a correcting unit 17 as correcting means for correcting the focus search drive signal when the focus search is performed again after the reproduction of the optical disc 3. In the case where the focus search is performed again after the reproduction of the optical disc 3, an external impact is applied to the optical disc apparatus 1 during the reproduction, so that the objective lens 4 is vibrated and the focus servo is kept on. The case where it becomes impossible to do it is mentioned.

  The correction unit 17 reads the displacement amount of the optical disc 3 stored in the memory 16 and corrects the focus search profile by offsetting the read displacement amount to the focus search profile.

  Thereby, the amplitude of the focus search signal is corrected by the corrected focus search profile, and as a result, the amplitude of the focus search drive signal generated by amplifying the focus search signal is corrected.

  For example, as shown in FIG. 3, when the optical disc 3 has a warp such that the distance from the objective lens 4 becomes closer as it goes outward in the radial direction, that is, the radial position of the optical disc 3 is outward. As an example, the displacement of the recording surface of the optical disc 3 from the reference plane increases toward the non-recording surface side.

  In this case, the reference position of the focus search profile is corrected by the correction unit 17 so that the reference position of the focus search profile is displaced in the anti-recording surface direction toward the outer side in the radial direction of the optical disk 3 along the warp of the optical disk 3. Accordingly, the upper limit (recording surface side) and lower limit (counter recording surface side) of the amplitude of the focus search signal are displaced in the anti-recording surface direction toward the outer side in the radial direction of the optical disc 3 with the displacement of the reference position. It is corrected to.

  As a result, the focus search drive signal generated by amplifying the focus search signal also follows the displacement of the reference position at the upper limit (recording surface side) and lower limit (anti-recording surface side) of the amplitude as shown in FIG. Thus, correction is made so that the optical disk 3 is displaced in the direction opposite to the recording surface as it goes outward in the radial direction.

  As another example, as shown in FIG. 4, when the optical disc 3 has a warp such that the distance from the objective lens 4 increases toward the outside in the radial direction, the reference position of the search profile is Correction is made so as to be displaced in the recording surface direction toward the outer side in the radial direction of the optical disk 3 along the warp of the optical disk 3. Accordingly, the upper limit (recording surface side) and lower limit (counter recording surface side) of the amplitude of the focus search signal are corrected so as to be displaced in the recording surface direction toward the outer side in the radial direction of the optical disc 3 with the displacement of the reference position. Is done.

  As a result, the focus search drive signal generated by amplifying the focus search signal also follows the displacement of the reference position with the upper limit (recording surface side) and lower limit (anti-recording surface side) of the amplitude as shown in FIG. Thus, correction is made so that the optical disk 3 is displaced in the direction opposite to the recording surface as it goes outward in the radial direction.

  In addition to those shown in FIGS. 3 and 4, for example, the distance from the objective lens 4 increases as the optical disc 3 moves toward the center in the radial direction, and the distance from the objective lens 4 decreases toward the inside and outside. In the case of such a curved displacement, the reference position of the focus search profile is corrected so as to have a curved displacement along the displacement, and the upper and lower limits of the focus search drive signal are also The correction is made so as to follow the displacement of the position.

  Thus, regardless of the displacement of the recording surface of the optical disc 3 from the reference plane according to the radial position of the optical disc 3, the moving range of the objective lens 4 in the focus search that flexibly corresponds to the displacement is set. Can be done.

  Further, the displacement of the optical disk 3 can be easily measured based on the low frequency component of the focus servo drive signal at the time of reproduction by the measuring unit 15, and the focus can be obtained by correcting the focus search profile by the correcting unit 17. Since the search drive signal can be easily corrected, the optimum movement range of the objective lens 4 in the focus search can be set easily and appropriately.

  Each of the above components is a main component for performing the focus servo and focus search in FIG. 1, but in addition to this, the optical disk device 1 is provided with various components for reproducing the optical disk 3. ing.

  That is, as shown in FIG. 1, a spindle motor 19 is disposed on the same axis as the turntable 2, and the spindle motor 19 rotates the optical disk 3 on the turntable 2. .

  A spindle servo circuit 20 is connected to the spindle motor 19, and the spindle servo circuit 20 performs spindle servo that drives the spindle motor 19 so that the linear velocity is constant.

  The servo controller 13 described above is connected to the input side of the spindle servo circuit 20, and the servo controller 13 controls the spindle servo circuit 20 for spindle servo.

  A tracking servo circuit 21 is connected to the output side of the RF amplifier 9, and a tracking error signal TE is input to the tracking servo circuit 21 from the RF amplifier 9. The tracking servo circuit 21 outputs a tracking servo signal for performing tracking servo for a tracking actuator (not shown) disposed in the optical pickup 5 based on the input tracking error signal TE.

  A tracking servo driver 22 is connected to the output side of the tracking servo circuit 21. The tracking servo driver 22 amplifies the tracking servo signal input from the tracking servo circuit 21 and tracks it as a driving signal for tracking servo. Output to the actuator.

  As a result, the tracking actuator appropriately moves the objective lens 4 in the eccentric direction to perform tracking servo.

  The tracking servo circuit 21 is also connected to the servo controller 13 in the same manner as the focus servo circuit 11, and receives control such as setting of a tracking servo signal from the servo controller 13.

  A system controller 24 is connected to the servo controller 13 and the RF amplifier 9, and the system controller 24 performs overall control of the system necessary for reproduction of the optical disc apparatus 1.

  A sled servo circuit 25 is connected to the output side of the system controller 24, and the sled servo circuit 25 transfers the optical pickup 5 at a predetermined speed in the radial direction of the optical disc 3 under the control of the system controller 24. Is supposed to do.

  A thread motor 26 is connected to the output side of the thread servo circuit 25, and the thread motor 26 transports the optical pickup 5 in the radial direction of the optical disk 3 based on the thread servo by the thread servo circuit 25. ing.

  A digital signal processing circuit 27 is connected to the output side of the RF amplifier 9, and the (A + C) signal and the (B + D) signal output from the quadrant photodiode 7 are input to the digital signal processing circuit 27. It has become so.

  The digital signal processing circuit 27 reproduces and outputs audio information and image information recorded on the optical disc 3 from these signals as digital signals.

  A D / A converter 29 is connected to the output side of the digital signal processing circuit 27, and the digital signal output from the digital signal processing circuit 27 is input to the D / A converter 29. Yes.

  The D / A converter 29 decodes the digital signal into an analog signal.

  As a result, the reproduction information of the optical disc 3 is output as audio or image.

  Next, FIG. 5 shows a more detailed configuration of the focus servo circuit 11 described above.

  The focus servo circuit 11 has a focus search signal generation circuit 30. The focus search signal generation circuit 30 generates a focus search signal according to the focus search profile corrected by the correction unit 17, and outputs the focus search signal. It has become.

The terminal SW ₁ of the switch 31 is connected to the output side of the focus search signal generation circuit 30, and the terminal SW ₁ is connected to the focus servo driver 12 via the switch 31, so that the focus search signal is focused. It is output to the servo driver 12.

  The focus search signal output to the focus servo driver 12 is amplified by the focus servo driver 12 as described above and then output as a focus search drive signal.

  The focus servo circuit 11 has a zero cross detection circuit 33 for detecting the zero cross point of the focus error signal.

  The zero cross detection circuit 33 has an operational amplifier 34, and a focus error signal from the RF amplifier 9 is input to a non-inverting input terminal of the operational amplifier 34. On the other hand, the inverting input terminal of the operational amplifier 34 is grounded.

  The zero-cross detection circuit 33 outputs a status signal via the output terminal of the operational amplifier 34 when the focus error signal is at the zero level.

Furthermore, the terminal SW _{2 of the} switch 31 is connected to the non-inverting input terminal of the operational amplifier 34 of the zero cross detection circuit 33, and this terminal SW ₂ is connected to the focus servo driver 12 via the switch 31, The focus servo loop is switched on.

  Further, the focus servo circuit 11 has a focus state detection circuit 35 for detecting the focus state of the laser light irradiated on the recording surface of the optical disc 3.

  The focus state detection circuit 35 has an operational amplifier 36, and the sum signal from the RF amplifier 9 is input to the non-inverting input terminal of the operational amplifier 36. On the other hand, a reference voltage generation circuit 38 is connected to the inverting input terminal of the operational amplifier 36, and the reference voltage generation circuit 38 inputs a reference voltage to the operational amplifier 36.

  The focus state detection circuit 35 compares the sum signal with the reference voltage, and outputs a focus state signal when the sum signal is larger than the reference voltage.

  A switch control circuit 39 for performing switching control of the switch 31 is connected to the output terminal of the operational amplifier 34 of the zero cross detection circuit 33 and the output terminal of the operational amplifier 36 of the focus state detection circuit 35.

The switch control circuit 39, a status signal from the zero cross detection circuit 33, when both the state signal from the focus state detection circuit 35 is input, to perform control to connect the switch 31 to the terminal SW ₂ It has become. Thus, the focus servo loop is turned on, the focus error signal of zero level as a focus servo signal, are outputted through the terminal SW ₂ to a focus servo driver 12.

On the other hand, the switch control circuit, when there is no at least one input status signals from the status signal and the focus state detection circuit 35 from the zero-cross detection circuit 33, so as to perform control to connect the switch 31 to the terminal SW ₂ Yes. Thus, the focus servo loop is turned off, the focus search signal from the focus search signal generating circuit 30, are outputted through the terminal SW ₁ to the focus servo driver 12.

  Next, an embodiment of a focus search method for an optical disc apparatus according to the present invention will be described with reference to FIGS.

  Note that the focus search method of the optical disk apparatus in the present embodiment is performed using the optical disk apparatus 1 shown in FIGS.

  Here, FIG. 6 is a flowchart showing a series of processing steps until the warpage amount of the optical disc 3 as the displacement amount of the optical disc 3 in the focus search method of the optical disc apparatus of the present embodiment is measured.

  FIG. 7 shows a focus search method for the optical disk apparatus according to the present embodiment. The focus search drive signal is corrected based on the warpage amount of the optical disk measured through the processing of FIG. It is a flowchart which shows a series of process steps which perform a focus search.

  First, after the measurement of the warp amount of the optical disk 3 is started, it is determined in step 1 (ST1) of FIG. 6 whether or not the optical disk 3 is being reproduced. If it is being reproduced, the process proceeds to step 2 (ST2). If not being reproduced, the measurement of the warping amount of the optical disc 3 is terminated.

  In step 2 (ST2), the measurement unit 15 acquires a low frequency component of the focus servo drive signal.

  Next, in step 3 (ST3), the measurement unit 15 acquires the current reproduction address information and also acquires the radial position information of the optical disc 3 from the reproduction address information.

  Through the processes of step 2 (ST2) and step 3 (ST3), the warpage amount of the optical disc 3 is measured in a state having a correspondence relationship with the radial position of the optical disc 3.

  Next, in step 4 (ST4), the warpage amount of the optical disk 3 and the radial position information measured by the measurement unit 15 are stored in the memory 16 connected to the servo controller 13, thereby measuring the warpage amount of the optical disk 3. Exit.

  When the focus servo ON state cannot be maintained for some reason during the reproduction in FIG. 6, the focus search shown in FIG. 7 is started by turning off the focus servo loop.

  That is, after starting the focus search, as shown in step 11 (ST11) in FIG. 7, the radial position of the optical disc 3 is calculated from the reproduction address (previous reproduction address) at the time of reproduction in FIG.

  Next, in step 12 (ST12), the correction unit 17 reads the displacement amount of the optical disk 3 stored in the memory 16, and calculates a necessary offset from the warpage amount of the optical disk 3.

  As a result, the focus search profile is corrected based on the calculated offset.

  Next, in step 13 (ST13), the slew rate of the focus search drive signal is set based on the focus search profile corrected by the correction unit 17.

  Next, in step 14 (ST14), the amplitude above the reference position (see FIGS. 3 and 4) in the focus search drive signal is set, and in step 15 (ST15), the amplitude below the reference position is set. The

  Thereby, the amplitude of the focus search drive signal is corrected to a suitable value based on the displacement amount of the optical disc.

  The focus search drive signal correction process in step 12 (ST12) to step 14 (ST14) can be uniquely performed by correcting the focus search signal according to the focus search profile corrected by the correction unit.

  Next, in step 16 (ST16), a focus search based on the corrected focus search drive signal is executed.

  Next, in step 17 (ST17), it is determined whether or not a focus retractable position is detected based on the focus error signal. If it is detected, the focus search is terminated. Return to ST11).

  Therefore, according to the present embodiment, by correcting the focus search drive signal in accordance with the displacement amount of the optical disc 3, the recording surface of the optical disc 3 can be displaced from the reference plane in accordance with the radial position of the optical disc 3. Even if it has, the moving range of the objective lens 4 in the focus search corresponding to the displacement can be set.

  As a result, the focus search time can be shortened, and the problem of collision between the objective lens 4 and the optical disk 3 can be avoided.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed.

  For example, the present invention can be effectively applied to various optical disk devices such as in-vehicle navigation devices.

  Although not described in the above embodiment, the present invention can be effectively applied to an optical disc apparatus that performs recording on an optical disc.

1 is a block diagram showing an embodiment of an optical disc apparatus according to the present invention. Explanatory drawing which shows the focus servo error detection method in embodiment of the optical disk device based on this invention Explanatory drawing which shows the aspect of correction | amendment of the search profile of a focus search in relation to the displacement of an optical disk in embodiment of the optical disk device based on this invention. FIG. 3 is an explanatory diagram showing a correction mode different from FIG. 3 of the search profile of the focus search in relation to the displacement of the optical disc in the embodiment of the optical disc apparatus according to the present invention. 1 is a block diagram showing a configuration around a focus servo circuit in an embodiment of an optical disc apparatus according to the present invention. 5 is a flowchart showing a process for measuring the amount of displacement of an optical disc in an embodiment of a focus search method for an optical disc apparatus according to the present invention 7 is a flowchart showing a focus search drive signal correction process and a focus search process based on the corrected focus search drive signal in an embodiment of a focus search method for an optical disc apparatus according to the present invention. FIG. 3 is a diagram showing a focus search method for an optical disc apparatus that has been conventionally employed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 3 Optical disk 4 Objective lens 5 Optical pick-up 8 Moving means 9 RF amplifier 11 Focus servo circuit 12 Focus servo driver 13 Servo controller 15 Measuring part 16 Memory 17 Correction part 30 Focus search signal generation circuit

Claims (6)

A moving means for moving the objective lens of the optical pickup along a direction perpendicular to the recording surface of the optical disc by supplying a drive signal, and moving the objective lens by the moving means before reproducing or recording the optical disc; An optical disc device that performs a focus search while
Measuring means for measuring a displacement amount from a reference plane of a recording surface of the optical disc according to a radial position of the optical disc during reproduction or recording of the optical disc;
Correction means for correcting a drive signal supplied to the moving means for the focus search when performing the focus search again after the reproduction or recording based on a displacement amount from a reference plane of the recording surface of the optical disc; An optical disc apparatus comprising:   2. The optical disc apparatus according to claim 1, wherein the measuring unit measures a displacement amount of a recording surface of the optical disc from a reference plane based on a low frequency component of the drive signal at the time of reproduction or recording. .   The correction unit corrects the drive signal by correcting the focus search profile for performing the focus search according to a displacement amount from a reference plane of a recording surface of the optical disc. The optical disc apparatus according to claim 1 or 2. By supplying a drive signal to a moving means that moves the objective lens of the optical pickup in a direction orthogonal to the recording surface of the optical disk by supplying a drive signal, the moving means before the reproduction or recording of the optical disk. A focus search method of an optical disc apparatus that performs a focus search by moving the objective lens,
Measure the amount of displacement from the reference plane of the recording surface of the optical disc according to the radial position of the optical disc when reproducing or recording the optical disc,
When the focus search is performed again after the reproduction or recording, the drive signal supplied to the moving means for the focus search is corrected based on the amount of displacement from the reference plane of the recording surface of the optical disc. Focus search method for optical disc apparatus.   5. The focus search method for an optical disc apparatus according to claim 4, wherein a displacement amount of the recording surface of the optical disc from a reference plane is measured based on a low frequency component of the drive signal at the time of reproduction or recording.   5. The drive signal is corrected by correcting the focus search profile for performing the focus search according to a displacement amount of a recording surface of the optical disc from a reference plane. 6. A focus search method for an optical disc apparatus according to item 5.