JP4153498B2 - Optical storage - Google Patents

Description

Optical discs are attracting attention as a core storage medium for multimedia that has been rapidly developing in recent years. For example, looking at 3.5-inch MO cartridges, in addition to the conventional 128 MB, in recent years, 230 MB, 540 MB, A high-density recording medium of 640 MB is also provided.

  An optical storage device known as an optical disk drive using such an MO cartridge medium is a seek control that positions a light beam at a designated target track on the medium when a write command or a read command is received from a host device. And pull in. Next, on-track control for causing the light beam to follow the track center based on the tracking error signal is performed, and a write operation or a read operation based on a command from the host device is performed.

  In the on-track control, a tracking error signal indicating the amount of deviation from the track center is sampled at a predetermined time by an AD converter and read as a digital signal value so that the error between the target position indicating the track center and the current position becomes zero. The actuator mounted on the carriage is driven to feedback control the position of the light beam.

  During this on-track control, when the light beam passes through an ID area composed of embossed pits arranged at regular intervals on the medium track, a phenomenon occurs in which the level of the tracking error signal varies.

With respect to the fluctuation of the tracking error signal due to the return light in the ID area, when the signal value sampled by the AD converter is passed through the PID filter by the DSP that has been conventionally performing on-track control, the P term The gain of the D term or D term is reduced from the normal one, making the tracking of the tracking error signal steep level change caused by the ID area insensitive, and the fluctuation of the tracking error signal caused by the return light of the ID area as disturbance It prevents you from joining.
JP-A-9-63085

  The suppression of the level fluctuation of the tracking error signal due to such a conventional ID region is based on making the servo response insensitive by reducing the gain of the PID filter. However, if the gain of the PID filter is lowered, the tracking performance of the servo also becomes poor with respect to the detection component of the original deviation amount with respect to the track center included in the fluctuating tracking error signal. is there.

  For this reason, there is a problem that the level fluctuation of the tracking error signal due to the ID region is not sufficiently suppressed, and the on-track control becomes unstable. Further, since the level fluctuation of the tracking error signal due to the ID region is not sufficiently suppressed, there is a problem that the off-track slice level set for off-track detection is exceeded and off-track is erroneously detected.

The present invention provides an optical storage device that sufficiently suppresses fluctuations in the level of a tracking error signal caused by an ID area on a medium track and reduces adverse effects without impairing the servo response of on-track control. Objective.

  FIG. 1 is a diagram illustrating the principle of the present invention. First, the present invention relates to an actuator for moving an objective lens that irradiates a light beam to a medium in a direction crossing the track of the medium, and a tracking error corresponding to a position in the direction crossing the track of the light beam based on a received light output of the medium return light. Tracking error signal generation circuit that generates a signal, seek control unit that moves the light beam to the target track by controlling the actuator, and on-track control unit that tracks the target beam by controlling the actuator based on the tracking error signal And an optical storage device.

  As shown in FIG. 1 (A), the present invention relates to such an optical storage device. In the on-track control, when the light beam passes through the ID area on the medium track, a signal fluctuation appears in the tracking error signal. And a correction processing unit 100 that corrects the tracking error signal so as to reduce the signal fluctuation in this judgment section, suppresses the fluctuation of the tracking error signal due to the ID region, and performs feedback control for on-track control. Prevent instability.

  As shown in FIG. 1B, the correction processing unit 100 includes a correction timing determination unit 202, a correction value determination unit 200, and a correction unit (adder) 204. The correction timing determination unit 102 determines an interval in which a level fluctuation due to the ID area on the medium track of the tracking error signal (TES signal) appears as the correction timing. The correction value determination unit 200 determines a correction value used for correcting the tracking error signal. Further, the correction unit 204 performs the correction determined by the correction value determination unit 200 at the correction timing determined by the correction timing determination unit 202 with respect to the signal value read by sampling and digitally converting the tracking error signal with a predetermined period by the AD converter 92. Correct using the value. Here, the specific form of the correction processing unit 100 in FIG.

(Correction by target value and difference immediately after fluctuation)
The correction value determination unit 200 obtains a difference between a signal value first sampled by the AD converter after the correction start timing and a predetermined target value and determines the difference as a correction value, and the correction unit 204 sets the AD converter after the correction start timing. The correction value is subtracted from each of the signal values for a predetermined sample period including the first sampled signal value to correct.

  In this way, the difference between the value immediately after the signal fluctuation and the predetermined target value is used as a correction value, and the fluctuation is reduced by subtracting it from the signal value during the fluctuation period. Even if there is, the correction by the correction value corresponding to the drop of the signal from the target value can always be stably performed.

(Correction using the previous average value)
The correction value determination unit 200 calculates an average value of the signal values sampled by the AD converter over a predetermined sample period from the correction start timing for each correction timing, and determines the correction value as one correction unit. The correction value calculated at the previous correction timing is corrected by subtracting it from each of the signal values for a predetermined sample period including the signal value first sampled by the AD converter after the correction start timing.

  Thus, by subtracting the average value of the sample values in the previous signal fluctuation as the current correction value from the signal value during the fluctuation period to reduce the fluctuation, correction corresponding to the signal fluctuation in the preceding ID region can be performed. As compared with the case where the correction value is determined from the current signal fluctuation, stable correction can be performed even if the TES data obtained by AD conversion varies from one to another.

(Correction using the previous fluctuation waveform)
The correction value determination unit 200 stores, as a correction value, a signal value (fluctuation waveform value) sampled by the AD converter over a predetermined sample period from the correction start timing for each correction timing. The signal value stored at the correction timing is read and subtracted from each of the signal values for a predetermined sample period including the signal value first sampled by the AD converter after the correction start timing.

  In this way, the sample value of the fluctuation waveform in the previous signal fluctuation is stored as a correction value, and subtracted from the signal value during the current fluctuation period to reduce the fluctuation, thereby approximating the signal fluctuation waveform caused by each ID region. When the value is high, it is possible to correct the signal fluctuation almost completely.

(Correction by averaging multiple fluctuation waveforms)
The correction value determination unit 200 stores a plurality of signal values read from the AD converter over a predetermined sample period from the correction start timing for each correction timing, and signals stored at the same sample position for a predetermined number of times already stored. An average value is calculated and determined as a correction value. For example, the correction value determination unit 200 calculates an average value of signal values at the same sample position for two times stored in the previous cycle and the previous cycle for each correction timing, and determines a correction value.

  As described above, according to the present invention, when the light beam passes through the ID area on the medium track, the timing of the level fluctuation that appears as a drop in the signal level in the tracking error signal is determined as the correction timing. The tracking error signal obtained in step 1 is corrected to suppress the signal fluctuation caused by the ID area to reduce the influence of the signal fluctuation, and the on-track control becomes unstable due to the fluctuation of the tracking error signal caused by the ID area. This can be reliably prevented and stable on-track control can be realized.

In addition, the tracking error signal in which the signal variation caused by the ID region is corrected is detected off-track by comparing the tracking error signal with the off-track slice level, thereby erroneously off-tracking due to the signal variation caused by the ID region during on-track control. Can be reliably prevented from being erroneously detected.

<Contents>
1. Device configuration2. 2. Variation of tracking error signal Correction processing (1) Correction by difference before and after fluctuation (2) Correction by target value and difference immediately after fluctuation (3) Correction by previous average value (4) Correction by previous fluctuation waveform (5) Average of multiple fluctuation waveforms (6) Judgment of optimum correction timing (7) Compression of signal fluctuation (8) Clip of signal fluctuation

1. Device Configuration FIG. 2 is a circuit block diagram of an optical disk drive which is an optical storage device of the present invention. The optical disk drive according to the present invention includes a control unit 10 and an enclosure 11. The control unit 10 includes an MPU 12 that performs overall control of the optical disk drive, an interface 17 that exchanges commands and data with the host device, and an optical disk controller that performs processing necessary for reading and writing data to and from the optical disk medium. ODC) 14, DSP 16, and buffer memory 18 are provided. The buffer memory 18 is shared by the MPU 12, the optical disk controller 14, and the upper interface 17.

  The optical disk controller 14 is provided with a formatter 14-1 and an ECC processing unit 14-2. At the time of write access, the formatter 14-1 generates a recording format by dividing the NRZ write data into sector units of the medium, and the ECC processing unit 14-2 generates and adds an ECC code for each sector write data unit. If so, a CRC code is generated and added. Further, the sector data after the ECC encoding is converted into, for example, a 1-7 RLL code.

  At the time of read access, the demodulated sector read data is subjected to 1-7 RLL reverse conversion, CRC check is performed by the ECC processing unit 14-2, error detection is corrected, and NRZ data in units of sectors is further concatenated by the formatter 14-1. A read data stream is transferred to the host device.

  A write LSI circuit 20 is provided for the optical disk controller 14, and a write modulator 21 and a laser diode control circuit 22 are provided in the write LSI circuit 20. The control output of the laser diode control circuit 22 is given to a laser diode unit 30 provided in the optical unit on the enclosure 11 side. The laser diode unit 30 integrally includes a laser diode 30-1 and a monitor detector 30-2. The write modulator 21 converts the write data into a data format by PPM recording or PWM recording.

  In this embodiment, any one of 128 MB, 230 MB, 540 MB, and 640 MB can be used as an optical disc that performs recording and reproduction using the laser diode unit 30, that is, a rewritable MO cartridge medium. Of these, the 128 MB MO cartridge medium employs pit position recording (PPM recording) for recording data in accordance with the presence or absence of marks on the medium. The recording format of the medium is zone CAV, and the number of zones in the user area is one zone for a 128 MB medium.

  For the 230 MB, 540 MB, and 640 MB MO cartridge media for high density recording, pulse width recording (PWM recording) is employed in which the edge of the mark, that is, the leading edge and the trailing edge correspond to the data. Here, the difference in storage capacity between the 640 MB medium and the 540 MB medium is due to the difference in sector capacity. When the sector capacity is 2048 bytes, the difference is 640 MB, while when the sector capacity is 512 bytes, the difference is 540 MB. The recording format of the medium is zone CAV, and the number of zones in the user area is 10 zones for 230 MB media, 11 zones for 640 MB media, and 18 zones for 540 MB media.

  As described above, the optical disk drive of the present invention is compatible with MO cartridges having a storage capacity of 128 MB, 230 MB, 540 MB or 640 MB. Therefore, when the MO cartridge is loaded into the optical disk drive, the ID part formed by the embossed pits of the medium is first read, and the MPU 12 recognizes the type of the medium from the pit interval, and notifies the write LSI circuit 20 of the type result. To do.

  The sector write data from the optical disk drive 14 is converted into PPM recording data by the write modulator 21 if it is a 128 MB medium, and converted to PWM recording data if it is a 230 MB, 540 MB or 640 MB medium. Then, the PPM recording data or the PWM recording data converted by the write modulation unit 21 is given to the laser diode control circuit 22 and written to the medium by the light emission driving of the laser diode 30-1.

  A read LSI circuit 24 is provided as a read system for the optical disc drive 14, and a read demodulator 25 and a frequency synthesizer 26 are built in the read LSI circuit 24. To the read LSI circuit 24, the light reception signal of the beam return light from the laser diode 30-1 by the ID / MO detector 32 provided in the enclosure 11 is input as an ID signal and an MO signal via the head amplifier 34. Has been.

  The read demodulation unit 25 of the read LSI circuit 24 is provided with circuit functions such as an AGC circuit, a filter, a sector mark detection circuit, etc., and generates a read clock and read data from the input ID signal and MO signal, The PWM recording data is demodulated to the original NRZ data. Further, since the zone CAV is adopted as the control of the spindle motor 40, the frequency division ratio setting control for generating the clock frequency corresponding to the zone is performed from the MPU 12 to the frequency synthesizer 26 built in the read LSI circuit 24. ing.

The frequency synthesizer 26 is a PLL circuit provided with a programmable frequency divider, and generates a reference clock having a predetermined specific frequency according to the zone position of the medium as a read clock. That is, the frequency synthesizer 26 is configured by a PLL circuit having a programmable frequency divider, and a reference clock having a frequency fo according to a frequency division ratio (m / n) set by the MPU 12 according to a zone number is obtained.
fo = (m / n) · fi
Occurs according to

  Here, the frequency division value n of the denominator of the frequency division ratio (m / n) is a specific value corresponding to the type of the 128 MB, 230 MB, 540 MB or 640 MB medium. Further, the frequency division value m of the molecule is a value that changes according to the zone position of the medium, and is prepared in advance as table information of a value corresponding to the zone number for each medium.

  The read LSI circuit 24 further outputs a MOXID signal E4 to the DSP 16. The MOXID signal E4 is a signal which becomes H level (bit 1) in the MO area which is the data area and falls to L level (bit 0) in the ID area where the embossed pits are formed. It is a signal which shows the physical position of.

  The read data demodulated by the read LSI circuit 24 is given to the optical disk controller 14, and after the inverse conversion of 1-7RLL, the CRC processing and the ECC processing are performed by the encoding function of the ECC processing unit 14-2 to restore the NRZ sector data. After being connected to the stream of NRZ read data by the formatter 14-1, the data is transferred to the host device by the host interface 17 via the buffer memory 18.

  A detection signal of a temperature sensor 36 provided on the enclosure 11 side is given to the MPU 12 via the DSP 16. The MPU 12 controls the read, write, and erase light emission powers in the laser diode control circuit 22 to optimum values based on the environmental temperature inside the apparatus detected by the temperature sensor 36.

  The MPU 12 controls the spindle motor 40 provided on the enclosure 11 side by the driver 38 via the DSP 16. Since the recording format of the MO cartridge is zone CAV, the spindle motor 40 is rotated at a constant speed of, for example, 3000 rpm. The MPU 12 controls the electromagnet 44 provided on the enclosure 11 side via the driver 42 via the DSP 16. The electromagnet 44 is disposed on the side opposite to the beam irradiation side of the MO cartridge loaded in the apparatus, and supplies an external magnetic field to the medium during recording and erasing.

  The DSP 16 has a servo function for positioning the beam from the laser diode unit 30 with respect to the medium. The seek control unit 84 seeks to the target track and performs on-track, and the seek control unit 84 transmits the beam to the target track. Is provided with an on-track control unit 86 that follows the track center.

  In order to realize the servo function of the DSP 16, an FES detector 45 that receives the beam return light from the medium is provided in the optical unit on the enclosure 12 side, and the FES detection circuit (focus error signal detection circuit) 46 is connected to the FES detector 45. A focus error signal is generated from the received light output and input to the DSP 16.

  Further, a TES detector 47 for receiving the beam return light from the medium is provided in the optical unit on the enclosure 11 side, and the TES detection circuit (tracking error signal detection circuit) 48 generates the tracking error signal E1 from the light reception output of the TES detector 47. And input to the DSP 16. The tracking error signal E1 is input to a TZC detection circuit (track zero cross detection circuit) 50, and a track zero cross pulse E2 is generated and input to the DSP 16.

  On the enclosure 11 side, a lens position sensor 54 for detecting the lens position of the objective lens that irradiates the medium with the laser beam is provided, and the lens position detection signal (LPOS) E3 is input to the DSP 16. Further, the DSP 16 controls and drives the focus actuator 60, the lens actuator 64, and the VCM 68 via drivers 58, 62, and 66 in order to control the position of the beam spot on the medium.

  Here, the outline of the enclosure 11 in the optical disk drive is as shown in FIG. In FIG. 3, a spindle motor 40 is provided in a housing 67, and an MO cartridge 70 is inserted into the hub of the rotating shaft of the spindle motor 40 from the inlet door 69 side, so that the internal MO medium 72 is connected to the spindle motor 40. Loading to be mounted on the hub of the rotating shaft is performed.

  A carriage 76 is provided below the MO medium 72 of the loaded MO cartridge 70 so as to be movable in the direction crossing the medium track by the VCM 68.

  An objective lens 80 is mounted on the carriage 76, and a beam from a laser diode provided in the fixed optical system 78 is incident through a prism 82, and a beam spot is imaged on the medium surface of the MO medium 72.

  The objective lens 80 is controlled to move in the optical axis direction by the focus actuator 60 shown in the enclosure 11 of FIG. 2, and can be moved by the lens actuator 64 in the radial direction across the medium track, for example, within a range of several tens of tracks. The position of the objective lens 80 mounted on the carriage 76 is detected by the lens position sensor 54 in FIG.

  The lens position sensor 54 sets the lens position detection signal to zero at the neutral position where the optical axis of the objective lens 80 is directly above, and is a lens corresponding to the movement amount having different polarities for the movement toward the outer side and the movement toward the inner side. The position detection signal E3 is output.

  FIG. 4 is a functional block diagram of a seek control unit and an on-track control unit realized by the DSP 16 provided in the control unit 10 of FIG.

  First, a lens servo system for the lens actuator 64 which is a main body of low speed seek control will be described. The lens servo system is divided into a speed control system, an on-track servo system, and a lens position servo system. First, the speed control system inputs the track zero cross signal E2 to the track counter 110, obtains the time of the track zero cross interval from the clock count, and obtains the beam speed by the speed detector 112.

  The output of the speed detector 112 takes an error from the target speed from the register 116 at the addition point 114, and after phase compensation for the speed error is performed by the phase compensator 120 via the servo switch 118, the adder 122 is added. Is given to.

  The on-track servo system corresponding to the on-track control unit 86 in FIG. 2 inputs the tracking error signal E1 that has passed through the amplifier 88 and the low-pass filter 90 provided in the TES detection circuit 48 in FIG. At 92, sampling is performed with a sample clock of a predetermined frequency, converted into digital data (hereinafter referred to as “TES data”), and read into the DSP 16.

  The TES data read by the AD converter 92 is corrected by the TES offset set by the register 94 at the addition point 96, and then input to the correction processing unit 100 for correcting the signal fluctuation in the ID area according to the present invention. The MOXID signal E4 is input to the correction processing unit 100. The correction timing is determined from the falling edge of the MOXID signal E4 to the L level, and the signal fluctuation occurs over a predetermined sample period, for example, 4 sample periods 4T from the falling detection. The correction which suppresses is performed.

  The TES data corrected by the correction processing unit 100 is multiplied by a gain by the compensator 102 and subjected to a high-frequency gain increase for phase compensation, and then subjected to proportional, integral, and differential calculations by a PID calculator (PID filter) 104. Is then input to the adder 122 via the servo switch 106. The TES data corrected by the correction processing unit 100 is input to the off-track measurement unit 108. When a predetermined off-track slice level is exceeded, an off-track detection signal is notified to the disk controller 14 in FIG. The operation is prohibited until the off-track error is resolved.

  Further, as a lens position servo system, the lens position detection signal E3 is fetched as digital data by the AD converter 144, the LPOS offset is corrected by the register 148 by the adder 146, the phase compensation is performed by the phase compensator 150, and then the PID calculator A proportional-integral-derivative operation is performed at 152 and input to the adder 122 via the servo switch 156. Incidentally, TES offset cancellation can be added to the input side of the servo switch 156 by the register 154.

  The speed error signal of the speed control system, the tracking error signal of the on-track servo system, and the lens position error signal of the lens position servo system are added by the adder 122 and phase compensated by the phase compensator 158. Thereafter, after the track offset is corrected by the register 162 at the addition point 160, it is converted into an analog signal by the DA converter 166, and is output to the driver side as a current instruction value for the lens actuator 64.

  Next, the servo system of the VCM 64 that is the main body in high-speed seek control will be described. The servo system of the VCM 68 constitutes a servo system for feedforward control based on the error between the target track position during seek and the current track position. First, the current position by the register 168 of the beam detected by the counter 110 based on the track zero cross signal E2 is compared with the target track position of the register 172 by the adder 170, and a position error signal corresponding to the number of remaining tracks with respect to the target track position. Is generated.

  The output of the adder 170 is subjected to phase compensation by the phase compensator 174 and then subjected to proportional, integral, and differential operations by the PID computing unit 176, and further phase compensation is performed by the phase compensator 180 via the servo switch 178. And supplied to the IIR 188 via the adder 182. Further, after phase compensation is performed by the phase compensator 190, the adder 192 receives correction by the VCM offset by the register 194, and is given to the adder 198 through the limit 196.

  The adder 198 corrects the eccentricity of the medium by reading from the eccentricity memory 200. For the position error signal of the VCM servo subjected to the eccentricity correction by the adder 198, different polarities are set by the register 202 according to the seek in the inner direction and the seek in the outer direction. It is converted into an analog signal by the DA converter 206, converted into a VCM current instruction value by the VCM 68, and output to the driver side.

  Further, the output of the phase compensator 150 of the lens position servo system provided in the lens servo system is branched to the adder 182 of the VCM servo system and is input via the PID calculator 184 and the servo switch 186. . Therefore, when the lens seek is performed by driving the objective lens by the lens actuator 64 with the servo switch 186 turned on, the lens position error signal generated by the adder 146 based on the lens position detection signal at this time is converted into the PID calculator. A position error signal is added to the adder 182 of the VCM position servo system via 184 and the servo switch 186.

  For this reason, the VCM 68 controls the position of the carriage so that the lens position offset becomes zero by driving the lens actuator 64. Since servo control based on the error signal of the lens position detection signal by such a lens actuator is added to the servo system of the VCM 68, this is called double servo.

  FIG. 5 shows the control mode applied to the servo system of FIG. 4 and the on / off states of the servo switches 118, 106, 156, 178 and 186. The servo system control mode is divided into a track-off mode, a track-on mode (on-track control mode), a fine seek mode, and a position seek mode. The control contents in each mode are as shown in FIG.

  In the track-off mode, the servo switch 156 is turned on with the focus servo enabled, and the lens actuator 64 controls the objective lens to the zero position. For this reason, in the track-off mode, only the beam can be focused on the medium while the beam is stopped.

  In the track-on mode (on-track control mode), on-track control is performed by driving the lens actuator 64 with a tracking error signal by turning on the servo switch 106 with the focus servo enabled. Further, when the servo switch 186 is turned on, the VCM servo system is subjected to position servo based on the lens position detection signal so that the VCM offset and the eccentric offset can be compensated. In this track-on mode, the correction processing of the present invention is performed for the signal variation of the tracking error signal caused by the ID area.

  The fine seek mode is a control for moving the beam to the target position by the speed control of the lens actuator 64 and the feedforward control of the VCM 68 when an access to the target cylinder is instructed from the host device. That is, the speed of the lens actuator 64 is controlled by turning on the servo switch 118 with the focus servo enabled.

  Further, when the servo switch 178 is turned on, feedforward control is performed according to the error of the current track position with respect to the target track. Further, by turning on the servo switch 186, a double servo is applied to control the lens to the zero position by driving the VCM 68 based on the position error of the lens position detection signal E3.

  The position seek mode is lens position control by the lens actuator 64, and the beam is moved to the target track by a position error signal corresponding to the number of tracks at the current track position with respect to the target track position while the lens is held at the zero position. To control the position.

That is, with the focus servo enabled, the servo switch 156 is turned on, and the lens is locked by the lens actuator 64 to hold the lens at the zero position. In this state, when the servo switch 178 is turned on, the carriage is moved by the VCM 68 so that the error with respect to the target track position becomes zero, and the position of the beam is controlled to the target track.

2. FIG. 7 is a time chart of the tracking error signal MOXID signal and the TES data of the AD converter obtained during the on-track control in the on-track control unit 86 provided in the DSP 16 of FIG.

  7A is a tracking error signal (TES signal) obtained from the output of the amplifier 88 in FIG. 4, and FIG. 7B is a tracking error signal E1 obtained from the output of the low-pass filter 90 in FIG. 7C shows the MOXID signal E4 obtained from the read LSI circuit 24 of FIG. 2, and FIG. 7D shows the TES data sampled by the AD converter 92 of FIG.

  Since the track format of the MO medium 72 in FIG. 3 is a spiral track, the tracking error signal output from the amplifier 88 in FIG. 7A is a specified position for each rotation of the track during on-track control. Thus, a track jump returning to one track is performed, and a one-track seek waveform 300-1 is obtained by this track jump.

  Subsequently, feedback control for driving the lens actuator so as to eliminate the difference from the signal level of zero indicating the track center is performed by on-track control for the target track. The signal waveform during the on-track control has a waveform fluctuation 302-1 in which the signal waveform drops at a constant interval.

  FIG. 7B is a tracking error signal E1 input to the DSP 16 obtained from the tracking error signal waveform of FIG. 7A through the low-pass filter 90, and the high-frequency component is removed by passing through the low-pass filter 90. Then, the amplitude component of the head track jump seek waveform 300-2 decreases, and the subsequent signal fluctuation 302-2 during on-track control is also suppressed as compared with FIG. 7A.

  The tracking error signal E1 in FIG. 7B has a predetermined delay due to the low-pass filter 90 passing through the tracking error signal in FIG. The signal fluctuations 302-1 and 302-2 causing the signal drop in FIGS. 7A and 7B occur in the falling section at the L level in the MOXID signal E4 in FIG. Here, in the MOXID signal E4, the signal level obtained from the return light of the light beam irradiated to the MO area (data area) of the medium track is the H level (bit 1), and the signal from the ID portion where the embossed pits are formed. The signal level due to the return light falls to the L level (bit 0).

  Therefore, the timing at which the signal fluctuation 302-2 is generated in the tracking error signal E1 in FIG. 7B due to the falling edge of the MOXID signal E4 to the L level, that is, the correction start timing at which correction of the signal fluctuation 302-2 is started. Can be determined.

  The sampling operation of the TES data by the AD converter 92 in FIG. 7D is started when the tracking error signal E1 by the leading one-track seek becomes less than a predetermined level. The sampling frequency of the AD converter 92 is 68 kHz, for example.

  FIG. 8 shows each signal in the on-track control of FIG. In contrast to the signal fluctuation 302-1 caused by the ID region of the tracking error signal that is the output of the amplifier 88 in FIG. 8A, the signal fluctuation 302 of the tracking error signal E1 that is the output of the low-pass filter 90 in FIG. -2 is delayed in time by passing through the low-pass filter 90. The MOXID signal E4 shown in FIG. 8C is obtained almost in synchronization with the waveform fluctuation 302-1 of the tracking error signal that is the output of the amplifier 88 shown in FIG.

  The signal fluctuation 302-1 of the tracking error signal E1 by the ID portion of the medium track greatly fluctuates digitally like the data fluctuation 302-3 of the TES data obtained from the AD converter of FIG. If it is used for on-track control as it is, it is added as a disturbance to the on-track servo system, and the tracking control becomes unstable. In extreme cases, the control becomes abnormal and off-track occurs.

Therefore, in the present invention, the correction section is determined based on the falling edge of the MOXID signal E4 in FIG. 8C, and the TES data read by the AD converter 92 in FIG. By correcting over the waveform fluctuation section, adverse effects due to signal fluctuation of the tracking error signal caused by the ID portion are reduced.

3. Correction Process (1) Correction by Difference Before and After Variation FIG. 9 is a functional block diagram of the first embodiment of the correction processing unit 100 provided in the on-track control unit 86 of FIG. The first embodiment is characterized in that the TES data is corrected based on the difference immediately before and after the signal fluctuation caused in the tracking error signal due to the ID portion of the medium track.

  In FIG. 9, the correction processing unit 100 provided after the AD converter 92 and the adder 96 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction value calculation unit 200 includes a delay unit 206, an adder 208, a latch 210, and a correction value output switch 212.

  The delay unit 206 and the adder 208 obtain a difference between the TES data obtained from the AD converter 92 at the current sample point and the TES data obtained from the previous sample delayed by one sample period in the delay unit 206. . The latch 210 latches the difference value of the TES data output from the adder 208 at the correction start timing determined by the correction timing determination unit 202 as a correction value.

  The correction value output switch 212 is turned on for a predetermined period, for example, 4 sample periods 4T from the correction start timing by the correction timing determination unit 202, and outputs the correction value latched by the latch 210 to the correction adder 204. During this time, the correction value is subtracted from the TES data sampled sequentially by the AD converter 92 to correct.

  The correction timing determination unit 202 receives the MOXID signal E4 and monitors its falling edge to the L level. When the falling edge of the MOXID signal E4 to the L level is detected, the correction value obtained from the adder 208 is latched in synchronization with the sampling of the AD converter 92 immediately after that. Further, the correction value output switch 212 is turned on for a predetermined correction section, for example, 4 sample periods 4T from the latch timing at which the control signal is output to the latch 210, and the correction value held in the latch 210 is output to the correction adder 204. To correct.

  FIG. 10 is a time chart of the correction process of FIG. FIG. 10A shows a tracking error signal E1 input to the AD converter 92, which includes a signal fluctuation 302 in which the signal drops due to the ID portion on the medium track. FIG. 10B shows the MOXID signal E4, which falls from the H level to the L level at time t1, and a falling edge is detected.

  FIG. 10C shows TES data obtained by digitally converting the tracking error signal E1 of FIG. 10A by sampling at a predetermined sample period by the AD converter 92. Here, the tracking error signal E1 of FIG. The portion of the signal fluctuation 302 is extracted, for example, “... 1, 0, −1, −4, −4, −4, −2, 1, 2, 3, 3, 4. is doing.

  When the L level falling edge of the MOXID signal E4 at time t1 is detected for the TES data, the correction timing determination unit 202 in FIG. 9 latches 210 at the sample start time t2 of the first AD converter 92 immediately thereafter. A control signal is output to latch the output of the adder 208. At this time, the TES data “−4” obtained at the sample timing t2 and the TES data “−1” one sample period delayed by the delay unit 206 are input to the adder 208. Therefore, the adder 208 A difference value “−3” is output as the difference between the outputs of 208 and held in the latch 210 as a correction value.

  Then, as shown in FIG. 10D, the correction value output switch 212 of FIG. 9 is on for 4 sample periods 4T from the sample timing at time t2, so that the correction value “−3” in each of the four sample periods. Is output to the correction adder 204. The correction adder 204 subtracts the correction value “−3” held in the latch 210 for each of the TES data “−4, −4, −4, −2” obtained by four samplings from the sample timing t2. As a result, correction output values “−1, −1, −1, −1” can be obtained as shown in FIG.

  By such correction, the signal level drop caused by the ID portion of the TES data read by the AD converter 90 in FIG. 10A can be sufficiently suppressed as shown in FIG. Realize track control. FIG. 11 is a flowchart of the on-track control process including the correction process of the first embodiment of FIG. 9, and the process is repeatedly performed in synchronization with the sample clock of the AD converter 92. First, in step S1, TES data obtained by sampling of the AD converter 92 is read. In step S2, it is checked whether or not the falling edge of the MOXID signal.

  When the falling edge is detected, a correction value is calculated in step S3. In the case of the first embodiment of FIG. 9, this correction value is calculated as the difference between the TES data immediately after the falling edge and the TES data at the previous sample timing. Subsequently, in step S4, it is checked whether or not a predetermined correction end time, for example, 4 sample periods 4T.

  If the correction is under the correction end time, the TES offset set in the register 94 is subtracted from the TES data in the adder 96 in step S6, and the correction value is calculated from the TES data by the correction adder 204 in the next step S7. Correction processing for subtraction is performed, phase compensation for multiplying TES data by gain is performed in step S8, PID calculation is performed on TES data in step S9, and the result is finally converted to analog data by a DA converter 166 as shown in FIG. And a drive current is passed through the lens actuator 64.

  Further, in step S10, off-track determination by the off-track determination unit 108 to which the corrected TES data corrected by the correction adder 204 is input, that is, a predetermined offset slice level is compared with TES data, and the offset slice level is less than the offset slice level. If there is, the process is terminated. If the offset slice level is exceeded, an off-track error notification is made in step S11.

  Such a process involving a correction process for subtracting the correction value from the TES data in step S7 is repeated for each sample clock until a predetermined correction end time, for example, 4 sample periods 4T is reached in step S4. If the correction end time is reached in step S4, the process proceeds to step S5 to clear the correction value and prepare for the next correction process.

Until the next correction process, the correction value calculation process in step S3 is skipped until the falling edge of the MOXID signal is detected in step S2 for each sample period. At this time, the correction value is cleared. Therefore, even if the correction value is subtracted from the TES data in step S7, the correction value is zero, so that the TES data is not corrected, and the TES data obtained from the AD converter 92 is used as it is in step S8. Enter the gain multiplication.

(2) Correction Based on Difference between Target Value and Immediate Change FIG. 12 is a functional block diagram of the second embodiment of the correction processing unit 100 provided in the on-track control unit 86 in FIG. Is characterized in that it is corrected by the difference between the value immediately after the fluctuation of the tracking error signal caused by the ID part and a predetermined target value.

  In FIG. 2, the correction processing unit 100 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction value calculation unit 200 includes a target value register 214, an adder 208, a latch 210, and a correction value output switch 212. That is, the difference is that a target value register 214 is provided instead of the delay unit 206 of the first embodiment of FIG.

  The correction timing determination unit 202 is also the same as that in the first embodiment of FIG. 9. When the falling edge of the MOXID signal E4 is detected, a control signal is output to the latch 210 at the first sample start timing of the AD converter 92 immediately after that. Thus, the difference between the target value output from the adder 208 and the TES data corresponding to the depressed signal value sampled at that time is held as a correction value.

  The correction value held in the latch 210 is output to the correction adder 204 over the ON period of 4 sample periods 4T by the correction timing determination unit 202, and correction is performed. Here, as the target value set in the target value register 214, a value of TES data in a state where there is no signal drop by the ID section, for example, a target value “0” is used.

  FIG. 13 is a time chart of the correction process of the second embodiment of FIG. The TES signal E1 in FIG. 13A has a signal fluctuation 302 in which the signal drops corresponding to the ID portion on the medium track. The MOXID signal E4 in FIG. 13B falls from the H level to the L level at time t1, and a falling edge is detected. 9 corrects the target value “0” output from the adder 208 at the sample timing of the first AD converter 92 at time t2 immediately after the falling edge determination time t1, and the time at that time. Hold TES data difference.

  At this time, the target value is “0”, and the TES data obtained by sampling at time t 2 is “−3”. Therefore, the adder 208 outputs the difference value “−3”, which is held in the latch 210. The correction value “−3” held in the latch 210 is output to the correction adder 204 over the following four sample periods 4T as shown in FIG. 13D. As a result, as shown in FIG. The TES data “−3, −4, −4, −2” from the converter 92 is corrected to the corrected TES data “0, −1, −1, −1”, and signal fluctuation can be sufficiently reduced. .

Further, the flowchart of the on-track control process including the correction process of the second embodiment of FIG. 12 is the same as that of the first embodiment of FIG. 11 except that the target value is used for calculating the correction value in step S3. To do.

(3) Correction by previous average value FIG. 14 is a functional block diagram of the third embodiment of the correction processing unit 100 of the present invention provided in the on-track control unit 86 of FIG. In this case, the current signal fluctuation is corrected using the average value of the TES data in the signal fluctuation of the previous tracking error signal as a correction value.

  14, the correction processing unit 100 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction value calculation unit 200 includes an average processing unit 220, a storage unit 222, and a correction value output. A switch 224 is provided.

  When the correction timing determination unit 202 determines the falling edge of the MOXID signal E4, the average processing unit 220 obtains a TES obtained over a predetermined period, for example, 4 sample periods 4T from the immediately following sample start timing of the AD converter 92. The average value of the data is calculated and stored in the storage unit 222.

  The average value of the TES data of the signal variation stored in the storage unit 222 is read at the timing of the next signal variation by the correction timing determination unit 202, and over a predetermined period, for example, 4 sample periods 4T by the correction value output switch 224. The correction value is output to the correction adder 204 as a correction value, and the TES data from the AD converter 92 obtained at that time is corrected.

  Here, at the first correction timing, since the average value of the TES data obtained at the previous correction timing is not stored in the storage unit 222, the correction cannot be performed. Correction using the average value of the TES data obtained at the previous correction timing of the storage unit 222 becomes possible.

  FIG. 15 is a time chart of the third embodiment of FIG. FIG. 15A shows a tracking error signal E1 obtained during on-track control, and two signal fluctuations 302-1 and 302-2 are extracted from the signal fluctuation caused by the ID area. The MOXID signal in FIG. 15B falls from the H level to the L level at each of the times t1 and t3, and the correction start timing is determined.

  The TES data by the AD converter 92 in FIG. 15C is extracted for the first signal fluctuation 302-1 and the second signal fluctuation 302-2, and the TES data “ .., 2, 2, 1, -3, -4, -4, -4, -1, 1, 2, 3, 3 ... "and the second signal fluctuation 302-2. The TES data “..., 3, 2, 0, −3, −4, −4, −3, 0, 2, 3, 4, 4.

  FIG. 15D is a correction value calculated by the average processing unit 220 in FIG. 14, and when the falling edge of the MOXID signal E4 is determined at time t1, time t2 that is the first sample start timing immediately after that is determined. The average value “−3” of the four absolute values of the TES data “−3, −4, −4, −4” in the 4-sample period 4T is calculated and stored in the storage unit 222. In the first signal fluctuation 302-1, since the storage unit 222 has no correction value for the first time, the TES data of the AD converter is not corrected and is used as it is.

  For the next second signal fluctuation 302-2, when the MOXID signal E4 falls to the L level at time t3 and the correction start timing is determined, from the time t4 that is the sample start timing of the AD converter 92 immediately after that. Over the four-sample period 4T, as shown in the correction value of FIG. 15D, the average value “−3” stored in the storage unit 222 at the previous correction timing is output to the correction adder 204 as a correction value. Then, the TES data “−3, −4, −4, −3” obtained at that time is changed to the corrected TES data “0, −1, −1,0” like the corrected output value of FIG. Correction can be made to sufficiently reduce the signal fluctuation 302-2.

  Even at the correction timing from time t3, the average processing unit 220 calculates the average value “3” of the absolute values for the four TES data “−3, −4, −4, −3” obtained from time t4. Is calculated and stored in the storage unit 222, and the average value calculated this time at the next correction timing is used as the correction value.

The on-track control process including the correction process of the third embodiment of FIG. 14 is the same as the flowchart of the on-track control process of the first embodiment of FIG. 11, and the correction value calculation process in step S3 is the correction process of FIG. The point which becomes the processing content of the value calculation part 200 is different.

(4) Correction by previous fluctuation waveform FIG. 16 is a functional block diagram of a fourth embodiment of the correction processing unit 100 according to the present invention provided in the on-track control unit 86 of FIG. The TES data (fluctuation waveform) obtained at the previous correction timing is stored as it is and used as a correction value at the next correction timing.

  In FIG. 16, the correction processing unit 100 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction value calculation unit 200 includes a storage unit 226 and a correction value output switch 228. ing. The storage unit 226 is a memory that can simultaneously read / write at the same timing, stores TES data obtained from the AD converter 92 at the correction timing, and simultaneously reads and outputs the TES data stored at the previous correction timing as a correction value. To do.

  The correction value output switch 228 is turned on for a correction period, for example, 4 sample periods 4T, and the correction adder 204 uses the previous TES data read from the storage unit 226 in synchronization with the sample period of the AD converter 92 as a correction value. Output to.

  FIG. 17 is a time chart of the correction process of the fourth embodiment of FIG. FIG. 17A shows a tracking error signal E1 obtained during the on-track control, and shows two of the signal fluctuations 302-1 and 302-2 that are depressed corresponding to the ID region. FIG. 17B shows the MOXID signal E4, which falls from the H level to the L level at each of the times t1 and t3, whereby the correction start timing is determined.

  FIG. 17C shows the TES data of the AD converter 92 corresponding to the two signal fluctuations 302-1 and 302-2 of the tracking error signal E1, and the TES corresponding to the first signal fluctuation 302-1. Data "... 2, 2, 1, -3, -4, -4, -4, -1, 1, 2, 3, 3 ..." is obtained, and the second signal fluctuation 302-2 is obtained. TES data “..., 3, 2, 0, −3, −4, −4, −3, 0, 2, 3, 4, 4.

  In the storage unit 226 of FIG. 16, it is obtained at a 4-sample period 4T from the sample start timing at time t2 following the falling to the L level of the MOXID signal E4 at time t1 corresponding to the first signal fluctuation 302-1. TES data “−3, −4, −4, −4” to be stored is stored. The first correction is not performed because there is no previous stored data.

  Regarding the second signal fluctuation 302-2, when the MOXID signal E4 falls to the L level at the time t3 and the correction start timing is determined, 4 over the 4-sample period 4T from the sample start timing at the time t3 immediately after that. The previous TES data stored in the storage unit 226 in synchronization with the sample is output as the correction values “3, 4, 4, 4, 4” in FIG.

  The correction adder 204 stores the previous correction values “−3, −4, −4, −4” stored and read from the TES data “−3, −4, −4, −3” obtained at that time. By subtracting, the corrected TES data “0, 0, 0, 1” is corrected as in the corrected output value of FIG. 17E, and the signal fluctuation can be sufficiently reduced.

Here, the on-track control including the correction process of the fourth embodiment of FIG. 16 is the same as the on-track control flowchart of the first embodiment of FIG. 11, and the storage of FIG. 16 is performed as the correction value calculation in step S3. The difference is that the correction value stored at the previous correction timing is read and used by the unit 226.

(5) Correction by Average Value of Plural Fluctuating Waveforms FIG. 18 is a fifth embodiment of the correction processing unit 100 according to the present invention provided in the on-track control unit 86 of FIG. 4, and in this embodiment The TES data is corrected by calculating a correction value at the same sampling position at the current correction timing from each average value at the same sampling position of the TES data obtained at a plurality of past correction timings. To do.

  In FIG. 18, the correction processing unit 100 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction value calculation unit 200 is provided with a previous storage unit 230, a last-last storage unit 232, a sample average calculation unit 234, and a correction value output switch 236. The previous storage unit 230 stores, for example, four TES data obtained at the previous correction timing, for example, in four sample periods 4T.

  Similarly, the TES data of 4 sample periods 4T obtained at the correction timing of the last time is stored in the previous time storage unit 232. Specifically, the TES data stored in the previous storage unit 230 is shifted to the previous storage unit 232 at each correction timing, and at the same time, the currently obtained TES data from the AD converter 92 for 4T periods is stored in the previous time. The process memorize | stored in the part 230 is performed.

  The sample average calculation unit 234 reads the TES data at the same sample position in the previous storage unit 230 and the previous storage unit 232 for each sample period of 4 sample periods 4T at the correction timing, calculates the average value, and turns on at this time The correction value is output to the correction adder 204 via the correction value output switch 236.

  FIG. 19 is a time chart of the correction process according to the fifth embodiment of FIG. FIG. 19A shows a tracking error signal E1 obtained during on-track control, and a portion of the signal fluctuation 302 that falls corresponding to the ID area is extracted. The MOXID signal E3 in FIG. 19B falls from the H level to the L level at time t1, and the correction start timing is determined by determining the falling edge.

  The TES data obtained by the AD converter 92 in FIG. 19C is, for example, “...− 2, −2,1,0, −1, −3, −4, −4, −3,1,2 , 2 ... ". The correction value in this case is corrected TES data “−3, −3, −4, −03” as shown in FIG. The corrected TES data is calculated based on the TES data 310 and the previous TES data 312 at the previous correction timing shown on the left side.

  That is, the stored TES data at the previous correction timing is “−3, −4, −5, −4”, and the previously stored TES data 312 is “−3, −3, −3, −2”. Therefore, the correction value for the current correction is calculated by obtaining the average data “−3” of the first sample data “−3” and “−3” of the previous and previous TES data 310 and 312. Next, average data “−3” of the second TES data “−4” and “−3” is obtained. Next, average data “−4” of the third TES data “−5” and “−3” is obtained. Furthermore, the average data “−3” of the fourth TES data “−4” and “−2” is obtained.

  In this way, the corrected TES data “−3, −3, −4, −3” obtained as the average value of the TES data at the same sample position with respect to the TES data 310 and 312 at the previous and previous correction timings is currently obtained. The corrected TES data “0, −1, 0, 0” shown in the corrected output value of FIG. 19E is obtained by performing correction by subtracting the TES data “−3, −4, −4, −3”. As a result, it is possible to correct the signal fluctuation 302 sufficiently.

  Further, regarding the correction for the signal fluctuation corresponding to the ID area obtained next, as shown in the right side, the right side of FIG. 19D is calculated from the average value of the same sample position of the previous TES data 314 and the previous TES data 316. The corrected TES data shown in FIG. Here, the previous TES correction data 314 is the TES data “−3, −4, −4, −3” obtained at the correction timing at time t1, and the previous TES data 316 is shown on the left side at the correction timing at time t1. The TES data “−3, −4, −5, −4” used as the previous TES data 310 is obtained. In the same manner, the same processing is repeated for each correction timing.

  FIG. 20 is a flowchart of the on-track control process including the correction process of the fifth embodiment of FIG. First, in step S1, TES data is read from the AD converter 92, and in step S2, the presence or absence of a rising edge of the MOXID signal is determined. If it is a falling edge, the process proceeds to step S3, and the correction value is calculated by averaging the sample values at the same position of the previous time, that is, the TES data.

In step S4, the previous TES data is updated to the previous TES data, and the current TES data is updated to the previous TES data. Subsequent steps S5 to S12 are the same as steps S4 to S11 in the flowchart of the first embodiment of FIG.

(6) Determination of Optimal Correction Timing FIG. 21 shows a seventh embodiment of the correction processing unit 100 according to the present invention provided in the on-track control unit 86 in FIG. 4. In this embodiment, the rise of the MOXID signal is shown. The optimum correction timing is determined based on both the determination of the falling edge and the change amount of the tracking error signal at that time.

  In FIG. 21, the correction processing unit 100 includes a correction value calculation unit 200, a correction timing determination unit 202, and a correction adder 204. The correction timing determination unit 202 includes a falling determination unit 238, a TES change amount determination unit 240, and an AND circuit 242. The falling determination unit 238 determines a falling edge of the MOXID signal to the L level and outputs a determination signal E5 that becomes the H level to the AND circuit 242.

  The TES change amount determination unit 240 is a change amount determination signal E6 that becomes H level when the change amount as the difference between the current TES data read by the AD converter 92 and the previous TES data exceeds a predetermined value. Is output to the AND circuit 242. The AND circuit 242 outputs an H level determination signal indicating the optimal correction timing to the correction value calculation unit 200 when a determination signal that becomes H level is obtained from both the falling determination unit 238 and the TES change amount determination unit 240. To do.

  FIG. 22 is a time chart of optimum correction timing determination processing by the correction timing determination unit 202 of FIG. FIG. 22A shows a tracking error signal E1 obtained during the on-track control, and a portion of the signal fluctuation 302 that has dropped corresponding to the ID area on the medium track is extracted. The tracking error signal E1 becomes TES data read by the AD converter 92 as shown in FIG.

  FIG. 22C shows the MOXID signal E4, which has fallen from the H level to the L level at time t1, and at the sample start timing t2 in the AD converter 92 immediately after this time t1, as shown in FIG. 22D. The determination output E5 of the falling determination unit 238 rises to H level.

  The TES data in FIG. 22B after this time t2 has changed to “5, −1, −7, −8,...”, And the TES change amount determination unit 240 in FIG. .., And is compared with a predetermined value, for example, a predetermined value “4”. For this reason, the difference “6” when the TES data changes from “5” to “−1” at time t3 exceeds the predetermined value “4”, and the TES change amount determination unit 240 receives the difference as shown in FIG. Determination signal E6 rises to the H level.

  As a result, the AND circuit 242 outputs the correction timing determination signal E7 to the correction value calculation unit 200 at time t3 as shown in FIG. 22F, and the correction value calculation unit 200 performs, for example, 4 sample periods 4T from time t3. The correction value is calculated, and the correction adder 204 corrects the TES data from the AD converter 92.

  Here, if the determination process by the TES change amount determination unit 240 in FIG. 21 is not performed, the correction start timing is determined at time t2 immediately after the falling detection of the MOXID signal E4 at time t1 in FIG. Taking the correction value calculation unit 200 of the first embodiment of FIG. 9 as an example, the difference “1” between the TES data “5” at the correction start timing t2 and the previous TES data “6” is used as a correction value. 4T TES data "5, -1, -7, -8" is subtracted from the correction. In this case, the corrected TES data is "4, 0, -6, -7", and the signal fluctuation occurs because the timing is too early. Cannot be corrected sufficiently.

  On the other hand, according to the determination of the correction timing determination unit 202 of FIG. 21 in which the determination of the TES change amount is added in addition to the determination of the falling edge of the MOXID signal E4, the time t3 of FIG. 21 is determined as the correction start timing. In this case, the correction value as the difference between the TES data before and after time t3 is “6”, and the correction TES data in the 4-sample period 4T can be sufficiently corrected to “5, −1, −2, 0”. .

  FIG. 23 is a flowchart of on-track control processing including correction timing determination processing by the correction timing determination unit 202 of FIG. First, TES data is read from the AD converter 92 in step S1, and the falling edge of the MOXID signal E4 is determined in step S2.

If the falling edge is determined, the process proceeds to step S3, and the change amount of the TES data is calculated. If the amount of change is equal to or greater than the predetermined value in step S4, the process proceeds to step S5 to determine the optimum correction timing and calculate the correction value. The processing of steps S5 to S13 is the same processing corresponding to the processing of steps S3 to S11 in the on-track control processing of FIG.

(7) Compression of signal fluctuation FIG. 24 is a functional block diagram of a seventh embodiment of the correction processing unit 100 according to the present invention provided in the on-track control unit 86 of FIG. In this embodiment, the effect of the fluctuation signal is reduced by reducing the gain multiplied by the TES data sampled by the AD converter 92 at the correction timing of the signal fluctuation of the tracking error signal caused by the ID region. Features.

  In FIG. 24, the correction processing unit 100 includes a correction timing determination unit 202 and a gain switching unit 244. In addition to the phase compensator 102 having the gain G provided subsequent to the correction processing unit 100 in FIG. 4, the gain switching unit 244 has a phase in which a gain Gd lower than the gain G of the changeover switch 246 and the phase compensator 102 is set. A compensator 248 is provided so that the changeover switch 246 is switched from the illustrated phase compensator 102 to the phase compensator 248 side at the correction timing based on the falling edge detection of the MOXID signal E4 by the correction timing determination unit 202.

  Here, when the gain G of the phase compensator 102 is G = 1, the gain Gd of the phase compensator 248 that is switched at the correction timing is set to Gd = 0.5, for example.

  FIG. 25 is a time chart of the correction process in the seventh embodiment of FIG. FIG. 25A shows the tracking error signal E1, and a portion of the signal fluctuation 302 in which the signal drop is caused by the ID area during the on-track control is extracted. In the MOXID signal E4 in FIG. 25B, the falling edge from the H level to the L level is detected at time t1, and the correction start timing is determined.

  FIG. 25C shows the read value of the TES data sampled by the AD converter 92, which is extracted from the portion of the signal fluctuation 302 of the tracking error signal E1 in FIG. , 0, 0, -2, -3, -3, -2, 0, 1, 2, 2 ... ".

  24 detects the falling edge of the MOXID signal E4 to the L level at time t1, and sets the changeover switch 246 to the phase compensator at time t2, which is the sample start timing of the AD converter 92 immediately after that. The mode is switched from 102 to the phase compensator 248 side, and this switching state is maintained, for example, for 4 sample periods 4T from time t2.

  For this reason, the gain of the TES data from the AD converter 92 that passes through the gain switching unit 244 is the gain G = 1 by the phase compensator 102 until time t2, as shown in FIG. During the sample period 4T, the gain Gd of the phase compensator 248 is switched to 0.5.

  For this reason, the TES data “−2, −3, −3, −2” of the 4-sample period 4T from the time t2 passes through the phase compensator 248 and becomes like the correction output value of FIG. −1, −2, −2, −1 ”, and the signal fluctuation 302 of the tracking error signal E1 can be reduced. In FIG. 24, the case where the gain Gd of the phase compensator 248 is set to Gd = 0.5 is taken as an example, but the present invention is not limited to this. For example, Gd = 0.25 is used to further compress the signal fluctuation. You may make it raise a degree.

FIG. 26 is a flowchart of the on-track control process including the correction process of the seventh embodiment of FIG. First, TES data is read from the AD converter 92 in step S1, and subsequently, the falling edge of E4 of the MOXID signal is checked in step S2. When the falling edge is determined, the process proceeds to step S3, where the gain is changed to a lower value and held, thereby compressing the TES data of the signal fluctuation. Steps S4 to S11 are the same as steps S4 to S11 in FIG.

(8) Clip of signal fluctuation FIG. 27 is a functional block diagram of an eighth embodiment of the signal processing unit 100 according to the present invention provided in the on-track control unit 86 of FIG. In this embodiment, the signal fluctuation is reduced by clipping the signal fluctuation of the tracking error signal caused by the ID area during the on-track control using the TES data immediately before the signal fluctuation occurs. Features.

  In FIG. 27, the correction processing unit 100 includes a correction timing determination unit 202 and a clip processing unit 250. The clip processing unit 250 is provided with a latch 252 and a changeover switch 254. The correction timing determination unit 202 detects the falling edge of the MOXID signal E4 to the L level and outputs a control signal to the latch 252, and latches the TES data obtained from the AD converter 92 at that time.

  The TES data latched by the latch 252 is TES data immediately before signal fluctuation occurs. The correction timing determination unit 202 detects the falling edge of the MOXID signal E4 to the L level, latches the TES data in the latch 252, and sets the changeover switch 254 to the AD converter 92 at the first sample start timing of the AD converter 92. Is switched to the output of the latch 252, and this switching state is maintained for, for example, 4 sample periods 4T.

  As a result, during the correction period determined by the correction timing determination unit 202, the TES data immediately before the signal variation held in the latch 252 is output as the corrected TES data, and as a result, it is clipped to the TES data immediately before the signal variation. it can. FIG. 28 is a time chart of the correction process of FIG. FIG. 28A shows a tracking error signal E1 obtained during tracking control, and a portion of the signal fluctuation 302 corresponding to the ID region is extracted. FIG. 28B shows the MOXID signal E4, which falls from the H level to the L level at time t1, and at this time, the correction timing determination unit 202 outputs a control signal to the latch 252 to latch the TES data.

  FIG. 28C shows TES data sampled by the AD converter 92, which is extracted from the portion of the signal fluctuation 302 in the tracking error signal E1 in FIG. 28A. For example, “2, 1, 0, −2, -3, -4, -1, 1, 3, 3, 4, 5 ". The TES data is latched in the latch 252 when the falling edge of the MOXID signal E4 is detected at time t1, and the latched TES data becomes “0”. At time t2, which is the first sample start timing after latching the TES data “0” at time t1, the timing determination unit 202 switches the changeover switch 254 to the output side of the latch 252, and this switching state is changed from the time t2 to the four sample period. Maintain for 4T. Therefore, as shown in FIG. 28D, the latch 252 outputs the TES data “0” latched at the time t1 over the 4-sample period 4T from the time t2.

  For this reason, the TES data in the correction period from the time t2 to the four sample periods 4T is corrected from the TES data “−2, −3, −4, −1” as in the corrected output value of FIG. Clipping to “0, 0, 0, 0” can reduce the signal fluctuation 302 of the tracking error signal E1.

  FIG. 29 is a flowchart of the on-track control process including the correction process of the eighth embodiment of FIG. First, TES data sampled by the AD converter 92 is read in step S1, and the falling edge of the MOXID signal is determined in step S2. When the falling edge is determined, the TES data is latched in step S3 to obtain a clip value for correction. The processes in steps S4 to S11 are the same as those in the first embodiment shown in FIG.

  Here, in the correction timing determination unit 202 of the seventh embodiment of FIG. 24 and the eighth embodiment of FIG. 28, the falling edge from the H level to the L level of the MOXID signal E4 is determined, and the AD immediately after that is determined. The correction period of a certain period is set with the sample start timing of the converter 92 as the correction start timing. However, like the correction timing determination unit 202 of the sixth embodiment in FIG. 21, the falling edge determination of the MOXID signal E4 is performed. The correction start timing may be determined by the logical product of the determination of the change amount of the TES data.

  In the above embodiment, an apparatus including a lens actuator and a carriage actuator is taken as an example. On-track control of an apparatus that moves a light beam using only a carriage actuator without a lens actuator. Can be applied as is. This single actuator device is a device obtained by removing the driver 62, the lens actuator 64, and the lens position sensor 54 from the device of FIG.

The present invention is not limited to the above-described embodiments, and includes appropriate modifications that do not impair the objects and advantages of the present invention. Further, the present invention is not limited by the numerical values shown in the above embodiment.

Principle explanatory diagram of the present invention Block diagram of an optical disk drive according to the present invention. Illustration of the internal structure of the device loaded with the MO cartridge Functional block diagram of the servo system realized by the DSP of FIG. ON / OFF explanatory diagram of servo control mode of analog switch of FIG. Explanatory drawing of servo control mode in FIG. Time chart of track error signal, MOXID signal, and ADC read value obtained during on-track control A time chart in which the signal in Fig. 7 is expanded on the time axis FIG. 4 is a functional block diagram of the first embodiment of the correction processing unit shown in FIG. Time chart of the correction process in FIG. FIG. 9 is a flowchart of the correction process. FIG. 4 is a functional block diagram of the second embodiment of the correction processing unit of FIG. Time chart of the correction process of FIG. Functional block diagram of the third embodiment of the correction processing unit of FIG. 4 that corrects the current signal fluctuation by the average value of the previous signal fluctuation Time chart of the correction process of FIG. Functional block diagram of the fourth embodiment of the correction processing unit of FIG. 4 that stores the waveform of the previous signal fluctuation and corrects the current signal fluctuation. Time chart of the correction process of FIG. 4 is a functional block diagram of the fifth embodiment of the correction processing unit in FIG. 4 that corrects the current signal fluctuation based on the average value of the stored values of signal fluctuations of multiple times. Time chart of the correction process of FIG. Flowchart of the correction process in FIG. Functional block diagram of the sixth embodiment of the correction processing unit shown in FIG. Time chart of the determination process of FIG. The flowchart of the correction process including the determination process of FIG. Functional block diagram of a seventh embodiment of the correction processing unit of FIG. 4 that compresses signal fluctuations by gain switching. Time chart of the correction process of FIG. FIG. 24 is a flowchart of the correction process. Functional block diagram of an eighth embodiment of the correction processing unit of FIG. 4 that clips signal fluctuations with the immediately preceding TES data value Time chart of correction processing in FIG. FIG. 27 is a flowchart of the correction process.

Explanation of symbols

10: Control unit 11: Enclosure 12: MPU
14: Optical disk controller (ODC)
14-1: Formatter 14-2: ECC processor 16: DSP
17: Host interface 18: Buffer memory 20: Write LSI circuit 21: Encoder 22: Laser diode control circuit (LD control circuit)
23: Read LSI circuit 25: Read demodulation circuit 26: Frequency synthesizer 30: Laser diode unit 32: ID / MO detector 34: Head amplifier 36: Temperature sensors 38, 42, 58, 62, 66: Driver 40: Spindle motor 44 : Electromagnet 45: Detector for FES (4-part detector)
46: FES detection circuit 47: TES detector (two-divided detector)
48: TES detection circuit 50: TZC detection circuit 54: Lens position sensor 56: Carriage position sensor (PSD)
60: Focus actuator 64: Lens actuator 67: Housing 68: VCM (carriage actuator)
69: Inlet door 70: MO cartridge 72: MO medium 76: Carriage 78: Fixed optical system 80: Objective lens 84: Seek control unit 86: On-track control unit 88: Amplifier 90: Low pass fill (LPF)
92: AD converter 100: Correction processing unit 102: Phase compensation unit 104: PID calculation unit (PID filter)
106: Servo switch 108: Off-track detection unit 200: Correction value determination unit 202: Correction timing determination unit 204: Correction adder (correction unit)
206: delay unit 208, 216: adder 210, 252: latch 212, 218, 224, 228, 236: correction value output switch 214: target value register 220: average processing unit 222, 226: storage unit 230: previous storage unit 232: Last time storage unit 234: Sample average calculation unit 238: Falling determination unit 240: TES change amount determination unit 242: AND circuits 246, 254: Changeover switch 248: Low gain phase compensator 250: Clip processing unit

Claims (3)

An actuator that moves an objective lens that irradiates the medium with a light beam in a direction across the track of the medium;
A tracking error signal generating circuit that generates a tracking error signal according to a position in a direction crossing the track of the light beam based on a light reception output of the medium return light;
A seek control unit that moves the light beam to a target track under the control of the actuator;
An on-track control unit for causing a light beam to follow a target track by controlling the actuator based on the tracking error signal;
In an optical storage device comprising:
A correction timing determination unit that determines the inversion timing of a signal that is inverted when the light beam on the medium track passes from the MO region to the ID region during on-track control as the correction start timing of the tracking error signal;
A correction value determination unit that calculates an average value of the signal values of the tracking error signal sampled over a predetermined sample period from the correction start timing and determines the correction value for each correction start timing;
The correction value calculated in the previous time, an auxiliary Tadashibu correcting by subtracting from each of the signal value of the predetermined sampling period containing initially sampled signal values after the correction start timing,
An optical storage device characterized by comprising: An actuator that moves an objective lens that irradiates the medium with a light beam in a direction across the track of the medium;
A tracking error signal generating circuit that generates a tracking error signal according to a position in a direction crossing the track of the light beam based on a light reception output of the medium return light;
A seek control unit that moves the light beam to a target track under the control of the actuator;
An on-track control unit for causing a light beam to follow a target track by controlling the actuator based on the tracking error signal;
In an optical storage device comprising:
A correction timing determination unit that determines the inversion timing of a signal that is inverted when the light beam on the medium track passes from the MO region to the ID region during on-track control as the correction start timing of the tracking error signal;
A correction value determination unit that stores a signal value of a tracking error signal sampled over a predetermined sample period from the correction start timing as a correction value for each correction start timing;
A correction unit that reads out the signal value stored at the previous timing and subtracts and corrects each of the signal values for the predetermined sample period including the signal value sampled first after the correction start timing;
An optical storage device characterized by comprising:
An actuator that moves an objective lens that irradiates the medium with a light beam in a direction across the track of the medium;
A tracking error signal generating circuit that generates a tracking error signal according to a position in a direction crossing the track of the light beam based on a light reception output of the medium return light;
A seek control unit that moves the light beam to a target track under the control of the actuator;
An on-track control unit for causing a light beam to follow a target track by controlling the actuator based on the tracking error signal;
In an optical storage device comprising:
A correction timing determination unit that determines the inversion timing of a signal that is inverted when the light beam on the medium track passes from the MO region to the ID region during on-track control as the correction start timing of the tracking error signal;
For each correction start timing, a plurality of signal values of the tracking error signal sampled over a predetermined sample period from the correction start timing are stored, and the average value of the signal values at the same sample position for the predetermined number of times already stored A correction value determination unit that calculates and determines a correction value;
A correction unit that subtracts and corrects the average value of the same sample position determined by the correction value determination unit from each of the signal values for the predetermined sample period including the signal value sampled first after the correction start timing;
An optical storage device characterized by comprising:

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