JP2005267800A - Disk driver and calibration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To complete highly precise calibration in a short period of time. <P>SOLUTION: A disk driver 1 decodes reproduced signals being reproduced from an optical disk 100 by a Viterbi decoding method. The disk driver 1 includes an analog signal processor 16 which is used to obtain light receiving signals SD from an optical pickup 5, that is used to irradiate laser light beams L1 to the optical disk 100 and to detect reflected laser light beams L2, and generate reproduced RF signals, a Viterbi decoder 25A which is used to generate state data that express state transition itself in Viterbi decoding, a quality index generator 25B which is used to compute the difference between an amplitude reference value corresponding to the state transition recognized from the state data and a reproduced signal value that is obtained by A/D converting the reproduced RF signals and express superiority or inferiority of the quality of the reproduced RF signals on the basis of the difference and a CPU2 which is used to conduct calibration of the optical pickup 5 on the basis of a quality index value CQ. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a disk drive device, and is suitably applied to a disk drive device that records and reproduces data on, for example, an optical disk.

  Conventionally, in a disk drive device, data such as video and audio is recorded on an optical disk such as a CD (Compact Disc) and a DVD (Digital Versatile Disc), and the data is reproduced.

  Further, in order to cope with variations in manufacturing of optical disks, the disk drive device also needs to perform focus servo offset adjustment (that is, calibration) for each optical disk when the optical disk is inserted or when power is turned on.

In view of this, for example, there has been proposed a technique (for example, see Patent Document 1) in which focus servo offset adjustment is performed based on the amplitude of a reproduction signal (reproduction RF signal) actually read from an optical disk by a disk drive device.
Japanese Patent Laid-Open No. 10-283644 (page 9, FIG. 1)

  Recently, there has been a demand for a large capacity for optical discs, and data can be recorded at a high density by shortening the wavelength of the laser light, relatively increasing the numerical aperture of the objective lens, and thinning the cover layer of the optical disc. Possible disk drive devices have been developed.

  In the disk drive device having such a configuration, since the numerical aperture of the focus lens is relatively large and the thickness of the cover layer of the optical disk is relatively small, it is necessary to correct the spherical aberration of the laser light by an expander lens or the like.

  Further, the disk drive device needs to calibrate the position of the expander lens together with the focus servo for each optical disk having variations.

  However, in the disk drive device, when the reflected signal from the optical disk has astigmatism and other aberrations, the amplitude of the reproduced RF signal does not necessarily match the optimum value of the decoding result.

  That is, even if the disk drive device calibrates the focus servo and the expander lens based on the amplitude of the reproduction RF signal, the data recorded on the optical disk is not necessarily reproduced with the highest accuracy. In addition, there is a problem that it takes time to measure the amplitude of such a reproduction RF signal.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a disk drive device and a calibration method capable of completing highly accurate calibration in a short time.

  In order to solve this problem, in the present invention, in a disk drive device that decodes a reproduction signal reproduced from a disk-shaped recording medium by a Viterbi decoding method, the disk-shaped recording medium is irradiated with laser light and the reflected light is detected. Corresponding to the state transition recognized from the state data, the reproduction signal generating means for acquiring the light reception signal from the optical unit and generating the reproduction signal, the Viterbi decoding means for generating the state data representing the state transition itself in Viterbi decoding Quality index generation for calculating a difference between the amplitude reference value and a reproduction signal value generated by A / D converting the reproduction signal, and generating a quality index value representing the quality of the reproduction signal based on the difference And a control means for calibrating the optical unit based on the quality index value.

  As a result, the optical unit can be calibrated according to the difference between the amplitude reference value and the reproduction signal value in Viterbi decoding.

  Further, in the present invention, in a calibration method of a disk drive device for decoding a reproduction signal reproduced from a disk-shaped recording medium by a Viterbi decoding method, an optical for irradiating the disk-shaped recording medium with a laser beam and detecting the reflected light A reproduction signal generation step for acquiring a light reception signal from the unit to generate a reproduction signal, a Viterbi decoding step for generating state data representing the state transition itself in Viterbi decoding, and an amplitude corresponding to the state transition recognized from the state data Quality index generation for calculating a difference between a reference value and a reproduced signal value generated by A / D converting the reproduced signal, and generating a quality index value representing superiority or inferiority of the reproduced signal based on the difference And a control step for calibrating the optical unit based on the quality index value. It was.

  As a result, the optical unit can be calibrated according to the difference between the amplitude reference value and the reproduction signal value in Viterbi decoding.

  According to the present invention, it is possible to calibrate an optical unit according to a difference between an amplitude reference value and a reproduction signal value in Viterbi decoding, and thus complete a highly accurate calibration in a short time. A calibration method can be realized.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) Overall Configuration of Disk Drive Device In FIG. 1, reference numeral 1 denotes a disk drive device according to the present invention as a whole, and the CPU 2 controls the entire disk drive device 1 through a disk controller 3. The disk drive device 1 operates in response to a read / write command supplied from an external host device 200, and records and reproduces data with respect to the optical disk 100.

  The optical disk 100 is placed on a turntable (not shown), and is rotationally driven by a spindle motor 4 as a driving means when accessing (recording and reproducing) data. Then, data recorded on the optical disc 100 and ADIP (Address In Pre Groove) information are read by the wobbling groove by an optical pickup 5 (details will be described later) as an access means.

  The slide drive unit 14 reciprocates the optical pickup 5 in the disk radial direction under the control of the servo drive circuit 15.

  The read channel front end 17 of the analog signal processor 16 generates a reproduction RF signal based on a light reception signal SD (details will be described later) supplied from the optical pickup 5 and inputs it to the analog-digital converter 20. On the other hand, the matrix amplifier 18 performs a matrix operation on the received light signal SD to generate a focus error signal FE and a tracking error signal TE for servo control, and a push-pull signal PP which is information on the wobbling groove, and outputs them. Input to the analog-digital converter 20. Further, the PLL unit 19 generates a read clock RCK from the reproduction RF signal.

  The analog-digital converter 20 converts the reproduction RF signal, the focus error signal FE, the tracking error signal TE, and the push-pull signal PP into digital signals and inputs them to the digital signal processor 21.

  The digital signal processor 21 includes a write pulse generator 22, a servo signal processor 23, a wobble signal processor 24, and an RF signal processor 25.

  The wobble signal processor 24 decodes the push-pull signal PP, extracts ADIP information composed of addresses, physical format information, and the like, and supplies them to the CPU 2.

  The servo signal processor 23 generates various servo drive signals for focus (described later), expander (described later), tracking, slide, and spindle based on the focus error signal FE and tracking error signal TE. To the servo drive circuit 15. The servo signal processor 23 supplies a servo drive signal for instructing operations such as focus search, track jump, and seek to the servo drive circuit 15 in accordance with a command from the CPU 2. The servo drive circuit 15 drives the slide drive unit 14 and the spindle motor 4 based on the servo drive signal.

  The RF signal processor 25 performs Viterbi decoding processing on the reproduction RF signal read from the optical disc 100 to obtain reproduction data.

  That is, the Viterbi decoder 25A of the RF signal processor 25 is based on the value of the reproduced RF signal (reproduced signal value) at each timing defined according to the read clock RCK, and is estimated from the state transition pattern determined by the RLL encoding method. The likelihood state is selected sequentially. The Viterbi decoder 25 </ b> A generates reproduction data RD based on the selected series of state data, and supplies this to the disk controller 3.

  At this time, the quality index generator 25B of the RF signal processor 25, based on the maximum likelihood state selected by the Viterbi decoder 25A, has an amplitude reference value acxxx that is a theoretical value of an ideal reproduction RF signal in which no amplitude fluctuation or the like has occurred. Ask for. Further, the quality index generator 25B calculates the average value of the difference values e [t] between the reproduction signal value cxxx of the reproduction RF signal and the amplitude reference value acxxx at each sample time.

  The average value of the difference values e [t] corresponds to an error between the ideal waveform of the reproduced RF signal and the actual waveform, and represents the quality of the reproduced RF signal. The quality index generator 25B outputs the average value as a quality index value CQ indicating the quality of the reproduction RF signal.

  For example, as shown in FIG. 2, ac000, ac001, ac011, ac111, ac110, whose amplitude reference values at the sample times at times t−3, t−2, t−1, t, t + 1, t + 2, and t + 3 are indicated by broken lines. Assuming that ac100 and ac000 are the reproduction signal values at that time, respectively c000, c001, c011, c111, c110, c100, and c000, the difference value at each sample time is e [t−3] = ac000− shown by a thick solid line. c000, e [t-2] = ac001-c001, e [t-1] = ac011-c011, e [t] = ac111-c111, e [t + 1] = ac110-c110, e [t + 2] = Ac100-c100, e [t + 3] = ac000-c000. The quality index generator 25B has the following formula CQ = (e [t−3] + e [t−2] + e [t−1] + e [t] + e [t + 1] + e [t + 2] + e [t + 3]) / 7 to calculate the quality index value CQ.

  As described above, the disk drive device 1 is adapted to generate the reproduction data RD by Viterbi decoding the reproduction RF signal by the Viterbi decoder 25A, and at the same time calculate the quality index value CQ by the quality index generator 25B.

  Incidentally, the quality index generator 25B calculates the quality index value CQ in a short time in order to perform only a simple arithmetic processing such as taking the difference between the reproduction signal value of the reproduction RF signal and the amplitude reference value and calculating the average value thereof. can do.

  Incidentally, the disk controller 3 (FIG. 1) has an encoding / decoding unit 31, an ECC (Error Correcting Code) processing unit 32, and a host interface 33.

  During reproduction, the disk controller 3 performs decoding processing on the reproduction data RD supplied from the RF signal processor 25 by the encoding / decoding unit 31, and further performs error correction processing by the ECC processing unit 32, via the host interface 33. The data is transferred to an external host device 200 (for example, a personal computer).

  The encoding / decoding unit 31 of the disk controller 3 extracts subcode information, address information, management information, and additional information from information obtained by the decoding process, and supplies these information to the CPU 2.

  Further, the CPU 2 executes a recording operation on the optical disc 100 in response to a write command from the host device 200.

  That is, at the time of recording, the disk controller 3 adds an error correction code to the recording data supplied from the host device 200 by the ECC processing unit 32, and further the RLL (Run Length Limited) for the recording data by the encoding / decoding unit 31. The data is encoded and encoded into an RLL (1, 7) code, and then supplied to the write pulse generator 22 of the digital signal processor 21.

  The write pulse generator 22 performs processing such as waveform shaping on the recording data to generate laser modulation data DL, and supplies this to the optical pickup 5. The optical pickup 5 performs data writing on the optical disc 100 in accordance with the laser modulation data DL.

(2) Configuration of Optical Pickup As shown in FIG. 3, the optical pickup 5 controls the output of a laser diode 10 serving as a laser light source by an APC (Auto Power Control) circuit 13 that receives supply of laser modulation data DL. The laser beam L1 is emitted and sequentially passed through a collimator lens 41, a beam splitter 42, a movable lens 43A and a fixed lens 43B of an expander 43 that corrects the spherical aberration of the laser beam, and an objective lens 44 that is an output end of the laser beam. The signal recording surface of the optical disc 100 is irradiated.

  Incidentally, in the optical pickup 5, the expander lens 43 prevents the spherical aberration of the laser beam L1 that occurs because the numerical aperture of the objective lens 44 is relatively large and the thickness of the cover layer on the signal recording surface of the optical disc 100 is relatively thin. It is made to correct by.

  Here, the movable lens 43A of the expander 43 is held by an actuator 12A so as to be movable in the directions of arrows a and b, and the actuator 12A is controlled based on the expander servo signal CE from the servo drive circuit 15 (FIG. 1). Thus, the spherical aberration of the laser beam L1 is appropriately corrected.

  The objective lens 44 is held by the biaxial actuator 12B so as to be movable in the focus direction (that is, the directions of the arrows a and b) and the tracking direction. The objective lens 44 is based on the focus servo signal CF from the servo drive circuit 15 (FIG. 1). The laser beam L1 is focused on the signal recording surface of the optical disc 100 under the control of the shaft actuator 12B.

  The optical pickup 5 reflects the reflected laser light L2 reflected by the signal recording surface of the optical disc 100 by the beam splitter 42 through the objective lens 44, the fixed lens 43B and the movable lens 43A of the expander 43 in this order, and collimator lens 45 The light is irradiated to the photodetector 11 via.

  The photodetector 11 has a plurality of photodiodes, and each photodiode receives the reflected light from the optical disc 100 and photoelectrically converts it, generates a received light signal SD corresponding to the received light quantity and generates an analog signal processor 16. (FIG. 1).

  As described above, the optical pickup 5 controls the movable lens 43A and the objective lens 44 of the expander 43 so as to irradiate the laser light L1 corrected for spherical aberration on the recording surface of the optical disc 100 in a focused manner. Has been made.

(3) Calibration Using Quality Index Value By the way, since the optical disc 100 has a relatively small cover layer on the signal recording surface, an error may occur in the thickness of the cover layer when the optical disc 100 is manufactured.

  However, the disk drive device 1 is required to always generate the reproduction data RD with the highest possible accuracy for the optical disk 100 in which an error may occur in the cover layer thickness.

  For this reason, the disk drive device 1 sets the reference position of the objective lens 44 and the movable lens 43A of the expander 43 when the power is turned on while the optical disk 100 is set and when a new optical disk 100 is set. A so-called calibration is performed for each optical disc 100.

  In this calibration, the disk drive device 1 uses the reference position of the movable lens 43A of the expander 43 (hereinafter referred to as the expander position Ex) and the biaxial actuator 12B to move the objective lens 44 based on the quality index value CQ. Two values of the focus bias Fb when adjusting to the reference position are adjusted.

  At this time, since the quality index value CQ corresponds to an error between the ideal waveform of the reproduction RF signal and the actual waveform, the disk drive apparatus 1 may perform calibration so that the quality index value CQ is as small as possible.

  At the same time, it is desirable that the disk drive device 1 completes this calibration in as short a time as possible and can immediately start the next operation such as data recording or reproduction.

  Here, as shown by a solid line in FIG. 4, the disk drive device 1 has a characteristic that the quality index value CQ draws a downward convex curve with respect to the expander position Ex as the spherical aberration reference value. Therefore, the expander position Ex may be set to the expander position Ex0 when the quality index value CQ takes a minimum value.

  At the same time, as shown by a solid line in FIG. 5, the disk drive device 1 has a characteristic that the quality index value CQ draws a downward convex curve with respect to the focus bias Fb. What is necessary is just to set to the focus bias Fb0 when the quality index value CQ takes the minimum value.

  However, in the disk drive device 1, the expander position Ex and the focus bias Fb have a subordinate relationship with respect to the quality index value CQ.

  For example, in the disk drive device 1, the expander position Ex is set to the expander position Ex0 (FIG. 4) at which the quality index value CQ is a minimum value, and then the focus bias Fb is set to the quality index value CQ at the expander position Ex0. Is changed to the focus bias Fb0 (FIG. 5) that takes a minimum value.

  Then, as indicated by the wavy line in FIG. 4, the characteristic of the quality index value CQ with respect to the expander position Ex is changed by changing the focus bias Fb, and the minimum position of the quality index value CQ is moved from the expander position Ex0. End up.

  Further, in the disk drive apparatus 1, the focus bias Fb is set to the focus bias Fb0 (FIG. 5) at which the quality index value CQ is a minimum value, and then the expander position Ex is kept at the focus bias Fb0 while the quality index value CQ is the minimum. Assume that the value is changed to the expander position Ex0 (FIG. 4).

Then, as indicated by the wavy line in FIG. 5, the characteristic of the quality index value CQ with respect to the focus bias Fb changes due to the change of the expander position Ex, and the minimum position of the quality index value CQ moves from the focus bias Fb0. End up.

  Thus, since the expander position Ex and the focus bias Fb have a subordinate relationship with each other with respect to the quality index value CQ, the disk drive device 1 has the expander when the quality index value CQ is kept small. It is necessary to set the position Ex and the focus bias Fb in consideration of mutual influences.

  Here, as shown in FIG. 6, in the quality index characteristic diagram showing the characteristics of the quality index value CQ with respect to the focus bias Fb and the expander position Ex, if the quality index value CQ is divided into regions that have the same level, The boundary line of each region draws a concentric ellipse pattern (hereinafter referred to as a characteristic pattern), and the quality index value CQ is the smallest in the area of the quality index value CQ1, which is the central area of the characteristic pattern.

  For this reason, the disk drive device 1 may be such that the set point P indicated by the combination of the set value of the focus bias Fb and the set value of the expander position Ex is as close as possible to the center of the characteristic pattern.

  However, since the recording characteristics of the optical disc 100 are different for each optical disc 100, and the characteristic pattern in the quality index characteristic diagram is also different for each optical disc 100, the set point P cannot be determined uniformly.

  Therefore, the disk drive device 1 first fixes the focus bias Fb and sets the expander position Ex so that the quality index value CQ is minimized.

  This means, for example, that the set point P1 is moved to the set point P2 in the quality index characteristic diagram (FIG. 6).

  Next, the disk drive device 1 sets the focus bias Fb so that the quality index value CQ becomes the smallest with the expander position Ex set immediately before.

  This means, for example, that the set point P2 is moved to the set point P3 in the quality index characteristic diagram.

  In this manner, the disk drive device 1 alternately repeats the setting of the expander position Ex and the setting of the focus bias Fb, thereby sequentially setting points P2, P3, and P4 from the setting point P1 in the quality index characteristic diagram. Thus, the characteristic index value CQ can be gradually reduced from the outside of the characteristic pattern toward the central portion while moving in parallel with any of the coordinate axes, that is, the quality index value CQ can be reduced stepwise.

  Then, the disk drive device 1 can directly reduce the error between the ideal waveform and the actual waveform of the reproduction RF signal by reducing the quality index value CQ, and other indices such as the amplitude of the reproduction RF signal. Compared with the case of using the reproduction data, the Viterbi decoder 25A can decode the reproduction data with higher accuracy.

  In the actual calibration, the disk drive device 1 performs the setting of the expander position Ex, the setting of the focus bias Fb, and the setting of the expander position Ex again, so that the required time is minimized. Thus, the quality index value CQ is reduced while suppressing the noise to perform effective calibration.

(4) Calibration Processing Procedure Next, a calibration processing procedure when the disk drive device 1 alternately sets the expander position Ex and the focus bias Fb using the quality index value CQ will be described with reference to the flowchart shown in FIG. Will be described in detail.

  The CPU 2 of the disk drive device 1 enters from the start step of the routine RT1 of the calibration processing procedure when the power is turned on while the optical disk 100 is set or when a new optical disk 100 is set, and step SP1. , The expander position Ex and the focus bias Fb are set to the initial expander position ExA0 and the initial focus bias FbA0, respectively, and the process proceeds to the next step SP2.

  Here, in the disk drive device 1, the initial expander position ExA0 and the initial focus bias FbA0 are set such that the quality index value CQ is minimized when the standard optical disk 100 is set. Therefore, the quality index value CQ is not necessarily minimum.

  In step SP2, the CPU 2 moves the optical pickup 5 so that the laser light L1 can be applied to a calibration area provided in advance on the optical disc 100, and proceeds to the next step SP3.

  By the way, when data is recorded on a track adjacent to the read target track, the disk drive device 1 is slightly affected by the adjacent track when reading the data from the read target track. However, the range of the focus bias Fb from which the data can be read correctly becomes narrower than when no data is recorded.

  Therefore, the disk drive apparatus 1 is affected by the adjacent tracks by performing calibration using tracks in which data is recorded on both adjacent tracks (hereinafter referred to as calibration tracks) in the calibration area. Even in this case, the quality index value CQ can be reliably reduced.

  In step SP3, the CPU 2 writes predetermined calibration data in the calibration track of the calibration area of the optical disc 100 and its adjacent track, and then proceeds to the expander position setting subroutine SRT1 shown in FIG.

  In the expander position setting subroutine SRT1, the CPU 2 enters from the start step and proceeds to step SP11. As shown in FIG. 9A, the current expander position Ex (in this case, the initial expander position is maintained while the focus bias Fb is fixed). The calibration data is read from the calibration track while changing to five equally spaced intervals (ie, expander positions ExA-2, ExA-1, ExA0, ExA1 and ExA2) with the panda position ExA0) as the center, and each expander position The quality index value CQ at Ex is calculated, and the process proceeds to the next step SP12.

  In step SP12, the CPU 2 obtains a quadratic approximate curve S1 based on the calculated five quality index values CQ, and proceeds to the next step SP13.

  In step SP13, the CPU 2 determines whether or not an appropriate approximate curve has been obtained, that is, the correlation coefficient of the quadratic approximate curve S1 is equal to or greater than a predetermined threshold, and the quadratic coefficient of the approximate curve is positive (that is, lower). In addition, it is determined whether or not there is a minimum value in the range of 5 points.

  If a negative result is obtained here, this means that the correlation coefficient is lower than a predetermined threshold because there are points out of the approximate curve among the five quality index values CQ, or the quadratic order of the approximate curve. This indicates that the coefficient was negative (that is, convex upward) or that the approximate curve was monotonically increasing or monotonically decreasing and there was no local minimum in the range of 5 points. When this happens, the CPU 2 moves to the next step SP14.

  In step SP14, the CPU 2 does not change the five expander positions Ex as they are to obtain an approximate curve appropriately, or the current expander position Ex located at the center and the other four expander positions Ex are not changed. Each of the intervals is widened, or all five expander positions Ex are shifted to the side where the quality index value CQ becomes smaller, and the process returns to step SP11 again.

  On the other hand, if a positive result is obtained in step SP13, the CPU 2 proceeds to the next step SP15.

  In step SP15, the CPU 2 sets the expander position Ex when the quality index value CQ takes the minimum value as a new expander position Ex (in this case, the expander position ExB0), and moves to the next step SP16 to execute the extractor. The panda position setting subroutine SRT1 is terminated and the process returns to the original routine RT1 (FIG. 7).

  Thus, the CPU 2 can calculate the minimum value of the approximate curve with high accuracy by obtaining an appropriate approximate curve of the quality index value CQ, and can expand the quality index value CQ with certainty. The position Ex can be set.

  Here, the CPU 2 has performed the processing of the expander position setting subroutine SRT1 in the quality index characteristic diagram (FIG. 6) from the set point P1 (initial focus bias FbA0, initial expander position ExA0) to the set point P2 (initial This indicates that the focus bias FbA0 and the expander position ExB0) have been moved.

  Subsequently, the CPU 2 proceeds from the routine RT1 to a focus bias setting subroutine SRT2 shown in FIG.

  In the focus bias setting subroutine SRT2, the CPU 2 enters from the start step and proceeds to step SP21. As shown in FIG. 9B, the CPU 2 has an equal interval centered on the current focus bias Fb (in this case, the initial focus bias FbA0). The calibration data is read from the calibration track while changing in five ways (that is, focus biases FbA-2, FbA-1, FbA0, FbA1, and FbA2), and the quality index value CQ at each focus bias Fb at this time is calculated. The process proceeds to the next step SP22.

  In step SP22, as in step SP12, the CPU 2 obtains a quadratic approximate curve S2 based on the calculated five quality index values CQ, and proceeds to the next step SP23.

  In step SP23, as in step SP13, the CPU 2 determines whether or not an appropriate approximate curve has been obtained, that is, the correlation coefficient of the quadratic approximate curve S2 is equal to or greater than a predetermined threshold value, and the quadratic order of the approximate curve. It is determined whether or not the coefficient is positive (ie, convex downward), and there is a minimum value in the range of 5 points.

  If a negative result is obtained here, this means that the correlation coefficient is lower than a predetermined threshold because there are points out of the approximate curve among the five quality index values CQ, or the quadratic order of the approximate curve. This indicates that the coefficient was negative (that is, convex upward) or that the approximate curve was monotonically increasing or monotonically decreasing and there was no local minimum in the range of 5 points. When this happens, the CPU 2 moves to the next step SP24.

  In step SP24, the CPU 2 does not change the five focus biases Fb as they are, or determines the intervals between the current focus bias Fb located at the center and the other four focus biases Fb in order to appropriately obtain the approximate curve. Either widen or shift all five focus biases Fb to the side where the quality index value CQ becomes smaller, and return to step SP21 again.

  On the other hand, when a positive result is obtained in step SP23, the CPU 2 proceeds to next step SP25.

  In step SP25, the CPU 2 sets the focus bias Fb when the quality index value CQ takes the minimum value as a new focus bias Fb (in this case, the focus bias FbB0), moves to the next step SP26, and the focus bias setting subroutine. End SRT2 and return to the original routine RT1 (FIG. 7).

  Here, the fact that the CPU 2 has performed the processing of the focus bias setting subroutine SRT2 is that the setting point P2 (initial focus bias FbA0, expander position ExB0) to the setting point P3 (focus bias FbB0) in the quality index characteristic diagram (FIG. 6). , To the expander position ExB0).

  Subsequently, the CPU 2 shifts again from the routine RT1 to the expander position setting subroutine SRT1 shown in FIG. 8, and performs the above-described series of processing to newly set the expander position ExC0 as shown in FIG. 9C. Then, after returning to the routine RT1 (FIG. 7) again, the routine proceeds to the next step SP4 and the routine RT1 is terminated.

  Here, the fact that the CPU 2 has made the setting again by the expander position setting subroutine SRT1 is that the setting point P3 (focus bias FbB0, expander position ExB0) to the set point P4 (focus bias) in the quality index characteristic diagram (FIG. 6). FbB0, expander position ExC0).

  Thus, by alternately setting the expander position Ex and the focus bias Fb, the disk drive apparatus 1 can gradually approach the center area of the characteristic pattern from the initial set point P1 in the quality index characteristic diagram, and the quality index value CQ That is, the error between the ideal waveform of the reproduced RF signal and the actual waveform can be reduced stepwise.

(5) Operation and Effect In the above configuration, the disk drive device 1 sets the expander position Ex and the focus bias Fb so as to keep the quality index value CQ as small as possible when performing calibration on each optical disk 100. Set alternately one by one.

  At this time, the disk drive apparatus 1 sets the expander position Ex and the focus bias Fb, and suppresses the quality index value CQ that is output from the quality index generator 25B at any time, thereby reducing the ideal waveform of the reproduced RF signal and the actual waveform. The error from the waveform can be suppressed to a small level.

  In other words, since the reproduction RF signal input to the Viterbi decoder 25A by the disk drive device 1 is brought close to the ideal waveform directly, another (indirect) index such as the amplitude of the reproduction RF signal is used. Compared to the case, the Viterbi decoder 25A can decode the reproduction data with higher accuracy.

  In addition, when calculating the quality index value CQ, the disk drive apparatus 1 performs only an easy calculation process such as calculating the addition average of the difference between the reproduction signal value of the reproduction RF signal and the amplitude reference value by the quality index generator 25B. Therefore, the quality index generator 25B can be easily configured, and the quality index value CQ can be calculated in a short time.

  Further, the disk drive device 1 alternately sets the expander position Ex and the focus bias Fb that are subordinate to each other with respect to the quality index value CQ, whereby the set value of the focus bias Fb and the focus bias Fb in the quality index characteristic diagram of FIG. The set point P represented by the set value of the expander position Ex can be brought close to the central area of the characteristic pattern in a stepwise manner, and the quality index value CQ can be reliably set to be kept small.

  At this time, the disk drive apparatus 1 performs quality setting while setting the expander position Ex, setting the focus bias Fb, and setting the expander position Ex again only three times to minimize the required time. The index value CQ can be reduced.

  In addition, when setting the expander position Ex and the focus bias Fb, the disk drive apparatus 1 obtains an approximate curve based on only the five quality index values CQ and calculates the local minimum value in a very short time. Can be completed.

  At this time, the disk drive device 1 can calculate a minimum value of the approximate curve with high accuracy by obtaining an appropriate approximate curve of the quality index value CQ, and reliably reduce the quality index value CQ. The expander position Ex and the focus bias Fb can be set.

  According to the above configuration, the disk drive device 1 alternately sets the expander position Ex and the focus bias Fb by using the quality index value CQ when performing calibration for each optical disk 100, and the quality. By reducing the index value CQ, the error between the ideal waveform and the actual waveform of the reproduced RF signal can be suppressed directly and reliably without requiring time for the calibration. Can be completed in a short time.

(6) Other Embodiments In the above-described embodiment, a total of three settings such as setting of the expander position Ex, setting of the focus bias Fb, and setting of the expander position Ex are performed again. However, the present invention is not limited to this, and the setting of the expander position Ex and the focus bias Fb may be repeated alternately over a total of four or more times. In this case, calibration is required. Although the time increases, the quality index value CQ can be further reduced, so that the reproduction data RD can be generated with higher accuracy.

  Incidentally, in this case, instead of setting the expander position Ex, the focus bias Fb may be set first.

  Further, in the above-described embodiment, the case where the quality index value CQ used when obtaining the quadratic approximate curve is set to 5 points has been described, but the present invention is not limited to this, and 6 points or 9 points. For example, an arbitrary number may be used, and by increasing the number of quality index values CQ, the time required to obtain the approximate curve increases, but the approximate curve can be obtained with higher accuracy.

  At this time, in addition to changing the expander position Ex and the focus bias Fb when calculating the quality index value CQ at equal intervals, the expander position Ex and the focus bias Fb may be changed at arbitrary intervals, respectively. This interval may be changed at the time of setting and at the time of the second setting.

  In the above-described embodiment, the case where the recording layer of the optical disc 100 is one has been described. However, the present invention is not limited to this, and calibration is performed for each layer when the recording layer of the optical disc 100 is two or more. May be performed. Furthermore, in this case, the number of quality index values CQ and the number of times of setting the expander position Ex and the focus bias Fb when obtaining an approximate curve for each layer may be changed.

  Further, in the above-described embodiment, the case where the optical pickup 5 uses the expander 43 to correct the spherical aberration has been described. However, the present invention is not limited to this, and other spherical aberrations such as a liquid crystal element can be corrected. A correction method may be used.

  Further, in the above-described embodiment, the case where the calibration is performed on the optical disc 100 capable of recording and reproducing data has been described. However, the present invention is not limited to this, and the optical disc 100 for reproduction only is used. Calibration may be performed. In this case, instead of writing and reading calibration data in the calibration area of the optical disc 100, arbitrary data in an arbitrary area recorded on the optical disc 100 is selected as calibration data. Read out.

  Further, in the above-described embodiment, the optical pickup 5 as the optical unit, the analog signal processor 16 as the reproduction signal generation means, the Viterbi decoder 25A as the Viterbi decoding means, and the quality index generation as the quality index generation means Although the case where the disk drive device 1 as the disk drive device is configured by the device 25B and the CPU 2 as the control means has been described, the present invention is not limited to this, and other optical units having various configurations, and reproduction signal generation The disk drive device may be configured by the means, the Viterbi decoding means, the quality index value generating means, and the control means.

  The present invention can be used in various types of disk drive devices such as a recordable DVD (Digital Versatile Disc) drive and a CD-RW (Compact Disc-Rewritable) drive in addition to the Blu-ray Disc (trademark) type disk drive device. .

1 is a schematic block diagram showing a configuration of a disk drive device according to the present invention. It is a basic diagram with which it uses for description of an amplitude reference value and a reproduction signal value. It is a basic diagram which shows the structure of an optical pick-up. It is a basic diagram which shows the relationship between an expander position and a quality index value. It is a basic diagram which shows the relationship between a focus bias and a quality index value. It is a basic diagram which shows a quality parameter | index characteristic diagram. It is a flowchart which shows a calibration process procedure. It is a flowchart which shows an expander position setting subroutine. It is a basic diagram with which it uses for description of the setting of the expander position and focus bias using a quality index value. It is a flowchart which shows a focus bias setting subroutine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Disk drive apparatus, 2 ... CPU, 5 ... Optical pick-up, 12A ... Actuator, 12B ... Biaxial actuator, 16 ... Analog signal processor, 25A ... Viterbi decoder, 25B ... Quality index generation , 43... Expander, 43 A... Movable lens, 44.

Claims (12)

In a disk drive device for decoding a reproduction signal reproduced from a disk-shaped recording medium by a Viterbi decoding method,
Reproduction signal generation means for generating a reproduction signal by irradiating the disk-shaped recording medium with laser light and acquiring a light reception signal from an optical unit that detects the reflected light;
Viterbi decoding means for generating state data representing the state transition itself in Viterbi decoding;
A quality index indicating the difference between the amplitude reference value corresponding to the state transition recognized from the state data and the reproduction signal value obtained by A / D converting the reproduction signal, and indicating the superiority or inferiority of the reproduction signal based on the difference Quality index generation means for generating values;
And a control means for calibrating the optical unit based on the quality index value. The optical unit is
A focus adjusting means for adjusting the focus of the laser beam in a state where a focus bias is applied;
Spherical aberration correction means for correcting the spherical aberration of the laser beam based on the spherical aberration correction value,
The control means includes
2. The disk drive device according to claim 1, wherein a spherical aberration reference value serving as a reference for the spherical aberration correction value and the focus bias are set using the quality index value. The control means includes
The disk drive device according to claim 2, wherein the focus bias and the spherical aberration reference value are alternately set. The control means includes
An approximate curve based on each quality index value when the focus bias or the spherical aberration correction value is changed is obtained, and the focus bias or the spherical aberration reference value so that the quality index value takes a minimum value in the approximate curve The disk drive device according to claim 2, wherein: The optical unit is
Spherical aberration correction means for correcting the spherical aberration of the laser beam based on the spherical aberration correction value,
The control means includes
The disk drive device according to claim 1, wherein a spherical aberration reference value serving as a reference for the spherical aberration correction value is set using the quality index value. The control means includes
An approximate curve based on each quality index value when the spherical aberration correction value is changed is obtained, and the spherical aberration reference value is set so that the quality index value takes a minimum value in the approximate curve. The disk drive device according to claim 5. The optical unit is
A focus adjusting means for adjusting the focus of the laser beam with a focus bias applied;
The control means includes
The disk drive device according to claim 1, wherein the focus bias is set using the quality index value. The control means includes
The approximate bias based on each quality index value when the focus bias is changed is obtained, and the focus bias is set so that the quality index value takes a local minimum value in the approximate curve. The disk drive device described. In a calibration method of a disk drive device for decoding a reproduction signal reproduced from a disk-shaped recording medium by a Viterbi decoding method,
A reproduction signal generation step of generating a reproduction signal by irradiating the disk-shaped recording medium with a laser beam and obtaining a received light signal from an optical unit that detects the reflected light;
A Viterbi decoding step for generating state data representing the state transition itself in Viterbi decoding;
The difference between the amplitude reference value corresponding to the state transition recognized from the state data and the reproduction signal value generated by A / D converting the reproduction signal is calculated, and the quality of the reproduction signal is calculated based on the difference. A quality index generation step for generating a quality index value representing superiority or inferiority of,
And a control step for calibrating the optical unit based on the quality index value. The optical unit is
A focus adjusting means for adjusting the focus of the laser beam in a state where a focus bias is applied;
Spherical aberration correction means for correcting the spherical aberration of the laser beam based on the spherical aberration correction value,
The above control steps are:
The calibration method according to claim 9, wherein a spherical aberration reference value serving as a reference for the spherical aberration correction value and the focus bias are respectively set using the quality index value. The optical unit is
Spherical aberration correction means for correcting the spherical aberration of the laser beam based on the spherical aberration correction value,
The above control steps are:
The calibration method according to claim 9, wherein a spherical aberration reference value serving as a reference for the spherical aberration correction value is set using the quality index value. The optical unit is
A focus adjusting means for adjusting the focus of the laser beam with a focus bias applied;
The above control steps are:
The calibration method according to claim 9, wherein the focus bias is set using the quality index value.

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