JP2008165941A - Optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise method for adjusting servo gain for an optical disk having periodical header area on tracks and an optical disk unit having stable servo performance by using the method for adjusting servo gain. <P>SOLUTION: An adjusting reference signal applied to a servo loop when adjusting the loop gain sets the phase and period of the adjusting reference signal to have a desired phase relation at timing of passing through the header area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus having a servo gain adjustment function.

  As background art in this technical field, for example, there is JP-A-2004-47011. This publication describes that “the closed loop phase characteristic is detected from the output of the averaging process performed on the disturbance signal and the one-round signal, and the gain is adjusted”.

  As background art in this technical field, there is, for example, Japanese Patent Laid-Open No. 3-296806. In this publication, “the ratio of peak values detected by the first and second detection means is calculated, and the loop gain is varied so that this ratio becomes a predetermined value, thereby making the sensitivity of each element constituting the closed loop. It corrects the fluctuation of the loop gain due to the change, thereby stabilizing the servo system and preventing malfunction due to abnormal control signals. "

JP 2004-47011 A JP-A-3-296806

  An optical disc apparatus that reproduces or records information on an optical disc includes a focus servo mechanism that causes the focal point of the laser beam to follow the optical disc recording surface, and a tracking servo mechanism that causes the focal point of the laser beam to follow a track formed on the recording surface. Is provided. The servo gain in the tracking servo and the focus servo varies due to the influence of the reflectance of the optical disk and the individual difference of the optical disk apparatus. If the servo gain is significantly different from the design value, the phase margin and gain margin will decrease and the servo control will become unstable, and not only accurate information recording / reproduction will be possible, but also the recorded data on adjacent tracks may be destroyed. is there. In view of this, a technique for adjusting the servo gain every time an optical disk whose servo characteristics are likely to change is replaced is disclosed.

  As a servo gain adjustment method, a method called loop gain adjustment is disclosed in which a servo gain is adjusted to a desired characteristic from the characteristic of a response signal obtained by injecting an adjustment reference signal having a predetermined frequency into a servo loop.

  A method for adjusting the loop gain of the servo system will be described. By monitoring the response signal of the servo loop with respect to the adjustment reference signal and passing this signal through a band pass filter, only the frequency component of the adjustment reference signal is extracted. The output signal of the bandpass filter is called a monitor signal. In the loop gain adjustment, it is determined whether the servo gain has a desired characteristic by measuring the amplitude ratio or phase difference of the monitor signal with respect to the adjustment reference signal. The servo gain is adjusted to a desired characteristic by adjusting the variable gain provided in the servo loop so that the amplitude ratio or the phase difference is within the adjustment range.

  It is assumed that information is recorded or reproduced on an optical disc having a header area such as a CAPA (Complementary Allocated Pit Address) format in a DVD-RAM disc. When the laser spot follows the track and passes through the header area, the servo error signal fluctuates due to the influence. Therefore, when the loop gain adjustment is performed on the optical disc having the header area such as the CAPA area, there arises a problem that the adjustment accuracy is lowered due to the fluctuation of the servo error signal. Hereinafter, this problem will be described.

  For example, as disclosed in Patent Document 1, loop gain adjustment using phase difference measurement detects a point at which each waveform zero-crosses with respect to the adjustment reference signal and the monitor signal, and calculates the time difference. Measure and do. Specifically, since the frequencies of the adjustment reference signal and the monitor signal are known, the phase difference is calculated from the time difference, and a variable provided in the servo loop so that the calculated phase difference is within the adjustment range. The servo gain is adjusted to a desired characteristic by adjusting the gain.

  However, Patent Document 1 does not consider the fluctuation of the servo error signal when passing through the header area such as the CAPA area. If the servo error signal fluctuates when passing through the header area, the fluctuation remains in the monitor signal after passing through the band-pass filter, so that the waveform of the monitor signal is distorted when passing through the header area. Therefore, when the timing at which the monitor signal crosses zero and the timing at which the header region passes overlap, the zero cross point of the monitor signal moves due to the passage through the header region, making accurate phase difference measurement difficult. Therefore, there is a problem that the loop gain adjustment accuracy is lowered.

  Next, problems of loop gain adjustment using amplitude ratio measurement will be described. As a method of adjusting the loop gain by measuring the amplitude ratio, for example, as disclosed in Patent Document 2, the amplitude of the adjustment reference signal and the monitor signal is measured, and the amplitude ratio is calculated. Specifically, each signal is input to the peak value detection unit, the respective amplitudes are measured, the amplitude ratio is calculated from the measured amplitude values, and the calculated amplitude ratio falls within the adjustment range. The variable gain provided in the servo loop is adjusted to adjust the servo gain to a desired characteristic.

  However, Patent Document 2 does not consider the fluctuation of the servo error signal when passing through the header area such as the CAPA area. For example, when the amplitude is measured by detecting the peak value, but the point where the monitor signal takes the maximum value and the timing of passing the header area overlap, the maximum value of the monitor signal is a value that is larger by the fluctuation of the header area passing. Therefore, accurate amplitude ratio measurement becomes difficult. Therefore, there is a problem that the loop gain adjustment accuracy is lowered.

  Therefore, the present invention was invented to reduce the deterioration of the servo gain adjustment accuracy due to the fluctuation of the servo error signal when passing through the header area such as the CAPA area. Provided is an optical disc apparatus capable of performing stable servo gain adjustment and stably recording or reproducing information.

  An object of the present invention is to provide an optical disc apparatus capable of performing servo gain adjustment with high accuracy.

  The object of the present invention can be achieved by adjusting the servo gain in consideration of the header area as an example.

  According to the present invention, it is possible to provide an optical disc apparatus capable of performing servo gain adjustment with high accuracy.

  Embodiments of an optical disk recording / playback apparatus according to the present invention will be described below with reference to the drawings.

  The present invention can be applied to both tracking servo and focus servo. Here, the tracking servo is described as an example.

  A DVD-RAM disk will be described as an example, and the header area is called a CAPA area. In the DVD-RAM disc, since the CAPA area exists for each sector, the CAPA area passes through every sector period.

  Example 1 of the present invention will be described below.

  FIG. 1 is a block diagram showing an optical disk apparatus of the present embodiment.

  Reference numeral 101 denotes an optical disk having a CAPA area, and information is read, erased, or written by irradiation with laser light.

  Reference numeral 102 denotes an objective lens, which focuses the laser beam on the recording surface of the optical disc 101 by condensing the laser beam.

  Reference numeral 103 denotes an optical pickup, which includes a tracking actuator. In addition, a photodetector (not shown) that detects reflected light from the optical disc 101 and outputs an electrical signal corresponding to the amount of reflected light is provided.

  Reference numeral 104 denotes a spindle motor, which rotates the optical disc 101 at a predetermined speed.

  Reference numeral 105 denotes a tracking error signal generation circuit which generates and outputs a tracking error signal 201 from the output signal of the photodetector in the optical pickup 103.

  Reference numeral 106 denotes a variable gain circuit that receives the tracking error signal 201 and adjusts the servo gain in accordance with an instruction from a loop gain adjustment control circuit 116 described later.

  Reference numeral 107 denotes an adder that adds an adjustment reference signal 202 output from an adjustment reference signal generation circuit 113 described later to the output signal of the variable gain circuit 106.

  Reference numeral 108 denotes a tracking control circuit that performs phase and gain compensation on the output signal of the adder 107. Note that the output signal level of the adjustment reference signal 202 output from the adjustment reference signal generation circuit 113 described later is zero except during the loop gain adjustment period, and the output signal of the adder 107 is a tracking error signal except during the loop gain adjustment period. 201.

  Reference numeral 109 denotes a driver circuit that amplifies the output signal of the tracking control circuit 108 and supplies the amplified signal to the tracking actuator in the optical pickup 103.

  Reference numeral 110 denotes an RF signal generation circuit that generates an RF signal, which is a reproduction signal of information, from the output signal of the photodetector in the optical pickup 103.

  Reference numeral 111 denotes a CAPA area detection circuit, which detects the CAPA area of the optical disc 101 from the RF signal. The CAPA area detection signal 203 is set to the High level only during the period passing through the CAPA area, and is set to the Low level during the other periods. Generate.

  Reference numeral 112 denotes an adjustment reference signal control circuit, which outputs a control signal for controlling the adjustment reference signal generation circuit 113 described later so that the output of the adjustment reference signal 202 is started at a predetermined phase at a predetermined timing. .

  Reference numeral 113 denotes an adjustment reference signal generation circuit, which starts output of the adjustment reference signal 202 having a predetermined frequency from a predetermined phase based on a control signal from the adjustment reference signal control circuit 112.

  Reference numeral 114 denotes a bandpass filter, which extracts a component having the same frequency as the frequency of the adjustment reference signal from the output signal of the variable gain circuit 106. In the configuration of this embodiment, the adjustment reference signal is added by the adder 107 installed immediately after the variable gain circuit 106 in the servo loop. Therefore, the output signal of the variable gain circuit 106 becomes a response signal of the tracking servo loop with respect to the adjustment reference signal, and the signal after passing this signal through the band-pass filter 114 becomes the monitor signal 204.

  Reference numeral 115 denotes a phase difference measurement circuit which receives the adjustment reference signal 202 and the monitor signal 204 as input, calculates the phase difference by measuring the time difference between the two signals, and outputs the measurement result.

  Reference numeral 116 denotes a loop gain adjustment control circuit that acquires a phase difference from the phase difference measurement circuit 115 and issues an instruction to the adjustment reference signal control circuit 112 and the variable gain circuit 106. The servo gain is adjusted to a desired characteristic by changing the gain of the variable gain circuit 106 so that the calculated phase difference is within the adjustment range.

  FIG. 3 is a waveform diagram of signals at various parts relating to the present embodiment. 3A shows a CAPA area detection signal, FIG. 3B shows an adjustment reference signal, and FIG. 3D shows a monitor signal. 3C is a signal obtained by binarizing the adjustment reference signal (b), and FIG. 3E is a signal obtained by binarizing the monitor signal (d).

  In the phase difference measuring method in the phase difference measuring circuit 115 of this embodiment, the adjustment reference signal (b) and the monitor signal (d) are binarized, and the binarized signals (c) and (e) fall. An edge time difference T1 is measured. Since the frequencies of the adjustment reference signal and the monitor signal are known, the phase difference can be calculated from the time difference T1.

  The operations of the loop gain adjustment control circuit 116 and the adjustment reference signal control circuit 112 in this embodiment will be described below according to the loop gain adjustment flowchart shown in FIG.

  When the loop gain adjustment is started (step S401), the adjustment reference signal control circuit 112 detects the fall of the CAPA area detection signal 203 (step S402), and the phase of the adjustment reference signal 202 and the phase of the CAPA area detection signal 203 are predetermined. After waiting for a predetermined time from the falling edge of the CAPA area detection signal 203 so as to satisfy the phase difference relationship (step S403), the adjustment reference signal generation circuit 113 is instructed to start outputting the adjustment reference signal 202 (step S403). S404).

  The loop gain adjustment control circuit 116 acquires the phase difference between the monitor signal 204 output from the bandpass filter 114 and the adjustment reference signal 202 from the phase difference measurement circuit 115 (step S405). The phase difference measured when the tracking servo characteristic is the designed transfer characteristic is called a target phase difference. If the phase difference measured by the phase difference measurement circuit 115 is close to the target phase difference, it can be determined that the servo gain has a desired characteristic. Therefore, the loop gain adjustment control circuit 116 determines whether or not the loop gain adjustment is necessary by determining whether or not the difference between the phase difference measured by the phase difference measuring circuit 115 and the target phase difference is within the allowable adjustment range ( Step S406).

  If it is determined that loop gain adjustment is necessary (YES in step S406), the gain of the variable gain circuit 106 is changed by a predetermined change amount (step S407). The variable gain change (step S407), the phase difference acquisition (step S405), and the loop gain adjustment necessity determination (step S406) are repeated, and are repeated until the difference between the measured phase difference and the target phase difference falls within the allowable adjustment range. However, if the difference between the measurement phase difference and the target phase difference does not fall within the allowable adjustment range even if the gain of the variable gain circuit 106 is changed a predetermined number of times, the adjustment result when the difference becomes the minimum is obtained. Adopted as an adjustment value.

  As a result of changing the gain of the variable gain circuit 106, when the difference between the measured phase difference and the target phase difference falls within the allowable adjustment range, the loop gain adjustment control circuit 116 indicates that the servo gain has a desired characteristic. Judgment is made (in the case of NO in step S406), the adjustment reference signal control circuit 112 is instructed to stop the output of the adjustment reference signal 202 (step S408), and the loop gain adjustment is completed as described above (step S409).

  Next, the effect of the adjustment reference signal control circuit 112 in this embodiment will be described with reference to FIG. The adjustment reference signal control circuit 112 controls the output of the adjustment reference signal (b) to start from a predetermined phase after a predetermined time D1 after passing through the CAPA region. Here, as the waiting time D1 after passing the CAPA area and the output start phase of the adjustment reference signal (b), the zero cross point Z1 of the monitor signal (d) overlaps with the period when the CAPA area detection signal (a) becomes High. Set a value that satisfies the condition of not. FIG. 3 shows the case where the output start phase of the adjustment reference signal (b) is 0 °, but the output start phase may be set to a value other than 0 ° as long as the above condition is satisfied. In FIG. 3, since the passage timing of the CAPA region and the zero cross timing Z1 of the monitor signal are shifted, the time difference T1 can be accurately measured. Therefore, it is possible to adjust the loop gain with high accuracy.

  With the above operation, the optical disc apparatus according to the present embodiment can avoid the overlap of the phase difference measurement timing and the monitor signal fluctuation caused by passing through the CAPA region in the loop gain adjustment for the optical disc having the CAPA region. The phase difference can be measured well. Therefore, accurate loop gain adjustment can be performed.

  A second embodiment of the present invention will be described below.

  A block diagram showing the optical disk apparatus of the present embodiment is common with FIG. 1 which is a block diagram of the first embodiment.

  Further, the flowchart of this embodiment is common to FIG. 4 which is the flowchart of the first embodiment.

  The effect of the adjustment reference signal control circuit 112 in this embodiment will be described with reference to FIG. In this embodiment, the adjustment reference signal (b) is output from a predetermined phase other than 0 ° at the same time as the CAPA region passing timing instead of using the waiting time D1 in FIG. To start. The output start phase of the adjustment reference signal (b) is set so as to satisfy the condition that the zero cross point Z1 of the monitor signal (d) does not overlap with the period during which the CAPA area detection signal (a) is High. Thereby, the phase difference between the adjustment reference signal (b) and the CAPA area detection signal (a) can be made the same as in the case of FIG. Therefore, similarly to the case of FIG. 3, the time difference T1 can be accurately measured by shifting the passage timing of the CAPA region and the zero cross timing Z1 of the monitor signal (d). Therefore, it is possible to adjust the loop gain with high accuracy.

  A third embodiment of the present invention will be described below.

  FIG. 2 is a block diagram showing an optical disc apparatus according to Embodiment 3 of the present invention. The difference between FIG. 1 which is a block diagram of the first embodiment and FIG. 2 is that the phase difference measurement circuit 115 in FIG. 1 is changed to an amplitude ratio measurement circuit 117, and the components common to FIG. Are denoted by common reference numerals, and description thereof is omitted.

  FIG. 6 is a waveform diagram of signals at various parts relating to the present embodiment. FIG. 6A shows a CAPA area detection signal, FIG. 6B shows an adjustment reference signal, and FIG. 6D shows a monitor signal. 6C shows a signal obtained by passing the adjustment reference signal (b) through the first top hold circuit, and FIG. 6E shows a signal obtained by passing the monitor signal (d) through the second top hold circuit. .

  The amplitude ratio measuring method in the amplitude ratio measuring circuit 117 of the present embodiment is such that the half amplitude (amplitude from the center value) L1 of the adjustment reference signal (b) from the first top hold circuit and the monitor signal from the second top hold circuit. The amplitude ratio L2 / L1 is measured by obtaining the half amplitude L2 of (d) and inputting each to the divider.

  The operations of the loop gain adjustment control circuit 116 and the adjustment reference signal control circuit 112 in this embodiment will be described below according to the loop gain adjustment flowchart shown in FIG. 4 that is the flowchart of the first embodiment described above, except that the index for determining that the servo gain has a desired characteristic is an amplitude ratio instead of a phase difference. Steps similar to those in FIG. 4 are denoted by common reference numerals, and description thereof is omitted.

  The process up to step S404 is the same as in the case of FIG. 4 which is the flowchart of the first embodiment. The adjustment reference signal control circuit 112 waits for a predetermined time from the fall of the CAPA area detection signal 203 so that the phase of the adjustment reference signal 202 and the phase of the CAPA area detection signal 203 satisfy a predetermined phase difference relationship described later. (Step S403), the adjustment reference signal generation circuit 113 is instructed to start output of the adjustment reference signal 202 (Step S404).

  The loop gain adjustment control circuit 116 acquires the amplitude ratio between the monitor signal 204 output from the bandpass filter 114 and the adjustment reference signal 202 from the amplitude ratio measurement circuit 117 (step S410). The amplitude ratio measured when the tracking servo characteristic is the designed transfer characteristic is called a target amplitude ratio. The loop gain adjustment control circuit 116 determines whether or not the loop gain adjustment is necessary by determining whether or not the difference between the measured amplitude ratio and the target amplitude ratio is within the adjustment allowable range by the amplitude ratio measuring circuit 117 (step S411). .

  If it is determined that loop gain adjustment is necessary (YES in step S411), the gain of the variable gain circuit 106 is changed by a predetermined change amount (step S407). The variable gain change (step S407), the amplitude ratio acquisition (step S410), and the loop gain adjustment necessity determination (step S411) are repeatedly performed until the difference between the measured amplitude ratio and the target amplitude ratio falls within the allowable adjustment range. . However, if the difference between the measurement phase difference and the target phase difference does not fall within the allowable adjustment range even if the gain of the variable gain circuit 106 is changed a predetermined number of times, the adjustment result when the difference becomes the minimum is obtained. Adopted as an adjustment value.

  As a result of changing the gain of the variable gain circuit 106, when the difference between the measured amplitude ratio and the target amplitude ratio falls within the allowable adjustment range (NO in step S411), the flowchart in FIG. The loop gain adjustment is terminated in the same procedure as in the case (steps S408 to S409).

  Next, the effect of the adjustment reference signal control circuit 112 in this embodiment will be described with reference to FIG. The adjustment reference signal control circuit 112 controls the output of the adjustment reference signal (b) to start from a predetermined phase after a predetermined time D2 after passing through the CAPA region. Here, as the waiting time D2 after passing the CAPA area and the output start phase of the adjustment reference signal, the point M1 where the monitor signal (d) takes the maximum value overlaps with the period during which the CAPA area detection signal (a) is High. Set a value that satisfies the condition of not. Although FIG. 6 shows the case where the output start phase of the adjustment reference signal (b) is 0 °, the output start phase may be set to a value other than 0 ° as long as the above condition is satisfied. In FIG. 6, since the passage timing of the CAPA region and the point M1 at which the monitor signal (d) takes the maximum value are shifted, the half amplitude L2 of the monitor signal can be accurately measured, and the amplitude ratio L2 / L1 is expressed as Accurate measurement. Therefore, it is possible to adjust the loop gain with high accuracy.

  In the above description, an example is shown in which the amplitude ratio is measured using the level of the maximum value detected using the top hold circuit, but the minimum value detected using the bottom hold circuit is used instead of the maximum value. The amplitude ratio may be measured, or the amplitude ratio may be measured using both the maximum value and the minimum value.

  Further, as shown in FIG. 5 which is a waveform diagram of the second embodiment, it is possible to start the output of the adjustment reference signal from a predetermined phase simultaneously with the timing of passing the CAPA region.

  By the above operation, the optical disc apparatus according to the present embodiment can avoid the overlap of the fluctuation of the monitor signal due to the timing of the amplitude ratio measurement and the passage of the CAPA region in the loop gain adjustment for the optical disc having the CAPA region. The phase difference can be measured well. Therefore, accurate loop gain adjustment can be performed.

  A fourth embodiment of the present invention will be described below.

  From the viewpoint of improving the accuracy of loop gain adjustment, it is preferable to perform phase difference measurement or amplitude ratio measurement a plurality of times and determine whether the servo gain has a desired characteristic using the average value. Therefore, in this embodiment, an embodiment will be described that considers the case where the loop gain adjustment accuracy is improved by performing phase difference measurement or amplitude ratio measurement a plurality of times.

  This embodiment can be applied to both Example 1 for measuring a phase difference and Example 2 for measuring an amplitude ratio. Here, description will be made using the first embodiment for measuring the phase difference.

  A block diagram showing an optical disk device according to the fourth embodiment is common to FIG. 1 which is a block diagram of the first embodiment.

  The operations of the loop gain adjustment control circuit 116 and the adjustment reference signal control circuit 112 in this embodiment will be described below according to the loop gain adjustment flowchart shown in FIG. The steps other than the averaging step are the same as those in FIG. 4 which is the flowchart of the first embodiment, and the same steps as those in FIG.

  The process up to step S405 is the same as that in the case of FIG. 4 which is the flowchart of the first embodiment. The adjustment reference signal control circuit 112 waits for a predetermined time from the fall of the CAPA area detection signal 203 so that the phase of the adjustment reference signal 202 and the phase of the CAPA area detection signal 203 satisfy a predetermined phase difference relationship described later. (Step S403), the adjustment reference signal generation circuit 113 is instructed to start output of the adjustment reference signal 202 (Step S404).

  The loop gain adjustment control circuit 116 repeats the phase difference acquisition (step S405) from the phase difference measurement circuit 115 N times (N: number of times of averaging) (step S412), and then calculates the average value (step S413). It is determined whether or not the loop gain adjustment is necessary by determining whether or not the difference between the measured average value of the phase differences and the target phase difference is within the allowable adjustment range (step S414).

  If it is determined that loop gain adjustment is necessary (YES in step S414), the gain of the variable gain circuit 106 is changed by a predetermined change amount (step S407). Variable gain change (step S407), phase difference acquisition (step S405), N measurement completion checks (step 512), average value calculation (step S413), loop gain adjustment necessity determination (step S414) are repeatedly performed, It repeats until the difference between the average value of the measurement phase difference and the target phase difference falls within the allowable adjustment range. However, if the difference between the measurement phase difference and the target phase difference does not fall within the allowable adjustment range even if the gain of the variable gain circuit 106 is changed a predetermined number of times, the adjustment result when the difference becomes the minimum is obtained. Adopted as an adjustment value.

  As a result of changing the gain of the variable gain circuit 106, when the difference between the average value of the measured phase difference and the target phase difference is within the adjustment allowable range (NO in step S414), the flowchart in the first embodiment. The loop gain adjustment is completed in the same procedure as in FIG. 4 (steps S408 to S409).

  In this embodiment, the period of the adjustment reference signal 202 is determined so that the time obtained by multiplying the period of the adjustment reference signal 202 by an integer is equal to the sector period.

  FIG. 8 shows a waveform diagram when the period P2 of the adjustment reference signal is determined so that the sector period P1 is equal to the time obtained by doubling the period P2 of the adjustment reference signal. FIG. 8A shows the state of tracks before and after the CAPA area, and C800, C801, and C802 are CAPA areas. 8B is a CAPA area detection signal, FIG. 8C is an adjustment reference signal, FIG. 8E is a monitor signal, and FIG. 8D is a signal obtained by binarizing the adjustment reference signal (c). FIG. 8 (f) is a signal obtained by binarizing the monitor signal (e). In this embodiment, phase difference measurement is performed at the falling edge of the binarized signal. That is, phase difference measurement is performed once during one period of the adjustment reference signal.

  FIG. 8 shows a waveform diagram when the output of the adjustment reference signal is started from a predetermined phase after a predetermined time D3 after passing through the CAPA region C800. As shown in FIG. 8, the phase of the CAPA area passing timing in the monitor signal is always a constant phase. For this reason, as the waiting time D3 after passing the CAPA area and the output start phase of the adjustment reference signal, pay attention to the timing of passing the first CAPA area C801 after the start of the output of the adjustment reference signal (c). A value is set so that the period during which the CAPA area detection signal (a) is high and the falling edge of the binarized signal (f) do not overlap. With this setting, even in the CAPA area after the CAPA area C801, it is ensured that the period in which the CAPA area detection signal (a) is High and the falling edge of the binarized signal (f) do not overlap, and the time difference T801 ~ T804 can be accurately measured. Therefore, even when the phase measurement is performed many times, it is possible to avoid the fall of the binarized signal (f) from overlapping with the fluctuation of the monitor signal when passing through the CAPA region, and the loop gain adjustment with high accuracy can be performed. Is possible.

  Here, the case where the sector period is equal to the time obtained by doubling the period of the adjustment reference signal has been described. However, the case where the sector period is equal to the time obtained by multiplying the period of the adjustment reference signal by an arbitrary integer is also described above. Thus, since the phase of the CAPA region passing timing in the monitor signal is always a constant phase, the present invention can be similarly applied.

  A fifth embodiment of the present invention will be described below.

  A block diagram showing the optical disk apparatus of the present embodiment is common with FIG. 1 which is a block diagram of the first embodiment. Further, the flowchart of the present embodiment is common to FIG. 9 which is the flowchart of the fourth embodiment.

  In this embodiment, the period of the adjustment reference signal 202 is determined so that the time obtained by multiplying the period of the adjustment reference signal 202 by a first integer is equal to the time obtained by multiplying the sector period by a second integer.

  FIG. 10 shows a waveform diagram when the period P3 of the adjustment reference signal is determined so that the time obtained by quadrupling the period P3 of the adjustment reference signal is equal to the time obtained by multiplying the sector period P1 by three. FIG. 10A shows the state of tracks before and after the CAPA area, and C100 to C106 are CAPA areas. 10B is a CAPA area detection signal, FIG. 10C is an adjustment reference signal, FIG. 10E is a monitor signal, and FIG. 10D is a signal obtained by binarizing the adjustment reference signal (c). FIG. 10 (f) is a signal obtained by binarizing the monitor signal (e). In this embodiment, phase difference measurement is performed at the falling edge of the binarized signal. That is, phase difference measurement is performed once during one period of the adjustment reference signal.

  FIG. 10 shows a waveform diagram when output of the adjustment reference signal is started from a predetermined phase after a predetermined time D4 after passing through C100. In FIG. 10, the phase of the passage timing of the CAPA region C101 in the monitor signal (e) is equal to the phase of the passage timing of the CAPA region C104 in the monitor signal (e). Similarly, the phase of the passage timing of the CAPA region C102 in the monitor signal (e) is equal to the phase of the passage timing of the CAPA region C105 in the monitor signal (e), and the phase of the passage timing of the CAPA region C103 in the monitor signal (e). Is equal to the phase of the passage timing of the CAPA region C106 in the monitor signal (e). As shown in FIG. 10, when the period of the adjustment reference signal is set to be 3/4 times the sector period, there are three types of CAPA region passage timing phases in the monitor signal (e).

  Therefore, the waiting time D4 after passing the CAPA area and the output start phase of the adjustment reference signal are CAPA in three CAPA areas C101, C102 and C103 that pass continuously after the output of the adjustment reference signal (c) starts. A value is set such that the period in which the area detection signal (a) is High and the falling edge of the binarized signal (f) do not overlap. With this setting, even in the CAPA area after the CAPA area C103, it is guaranteed that the binarized signal (f) does not fall in the vicinity of the period in which the CAPA area detection signal (a) becomes High, and the time difference T101 to T108. Can be measured accurately. As a result, accurate loop gain adjustment is possible.

  Here, the case where the time obtained by multiplying the period of the adjustment reference signal by 4 is equal to the time obtained by multiplying the sector period by 3 is described. However, the time obtained by multiplying the period of the adjustment reference signal by an arbitrary first integer is Even when the time is equal to an arbitrary second integer multiple, the phase of the CAPA region passage timing in the monitor signal is a finite number of types as described above, and therefore the present invention can be similarly applied.

  A sixth embodiment of the present invention will be described below.

  A block diagram showing the optical disk apparatus of the present embodiment is common with FIG. 1 which is a block diagram of the first embodiment. Further, the flowchart of the present embodiment is common to FIG. 9 which is the flowchart of the fourth embodiment.

  The sixth embodiment is a modification of the fifth embodiment. In the fifth embodiment, the time obtained by multiplying the period of the adjustment reference signal 202 by the first integer multiple is equal to the second integer multiple of the sector period, but it may not be a perfect integer multiple. In other words, in this embodiment, the period of the adjustment reference signal 202 is determined so that the time obtained by multiplying the period of the adjustment reference signal 202 by the first integer is substantially equal to the time obtained by multiplying the sector period by the second integer.

  For example, consider a case where the frequency of the adjustment reference signal is 4.1 kHz with respect to a sector frequency of 2.0 kHz. FIG. 11 is a waveform diagram when the sector period Ps and the adjustment reference signal period Pa have the above values (Ps = 1/2000 = 0.5 [ms], Pa = 1 / 4100≈0.244 [ms]). Further, it is assumed that the time width Pc at which the CAPA area detection signal becomes High is 30 μs. 11A shows a CAPA area detection signal, FIG. 11B shows a monitor signal, and FIG. 11C shows a signal obtained by binarizing the monitor signal. Further, a point corresponding to the falling edge of the signal (c) obtained by binarizing the monitor signal on the monitor signal (b) is indicated by a black circle (●). This point is called phase difference measurement timing. Points A to F are phase difference measurement timings indicated by arrows in the drawing.

  When the frequency of the adjustment reference signal is exactly 4.0 kHz, two adjustment reference signals are included in one sector period, and the phase of the CAPA area passing timing in the monitor signal is passed through all CAPA areas. Are in the same phase. However, in FIG. 11, the adjustment reference signal enters 2.05 periods in one sector period, and the phase of the CAPA area passing timing in the monitor signal (b) gradually moves every time it passes through the CAPA area. However, since 4.1 kHz is a value close to 4.0 kHz, the degree of movement of the phase of the CAPA region passing timing in the monitor signal (b) is small, and the relative amount of movement in the sector period is expressed by the following equation.

Ps-2 * Pa [s] (Equation 1)
FIG. 11 shows that the CAPA region detection signal (a) is high at the phase difference measurement timing A and the phase difference measurement timing overlap, and the phase difference cannot be measured accurately. A state in which (a) is High and the phase difference measurement timing do not overlap each other are shown. For this reason, the adjustment reference signal is controlled so that the phase relationship is such that the phase difference measurement is started from the phase difference measurement timing B, and the phase difference measurement is performed a plurality of times. As described above, the phase of the CAPA region passage timing in the monitor signal (b) shifts, but the time when the CAPA region detection signal (a) is high and the phase difference measurement timing overlap again is the phase difference measurement timing. F.

As can be seen from FIG. 11, the CAPA region passage timing moves in the direction in which the phase on the monitor signal (b) increases. Assuming that the zero-cross point of the phase difference measurement timing C and the rising edge of the CAPA area detection signal (a) completely coincide with each other, the CAPA area passage timing is relatively relative to the monitor signal (b).
Pa-Pc [s] (Equation 2)
And the phase difference measurement timing again overlaps the period in which the CAPA area detection signal (a) is High. This corresponds to the phase difference measurement timing F in FIG.

  Since the monitor signal (b) actually fluctuates during the period of passing through the CAPA region, the zero-cross point of the phase difference measurement timing C and the rising edge of the CAPA region detection signal (a) are completely completed as assumed above. If the fluctuation amount of the monitor signal (b) is large, accurate phase difference measurement cannot be performed at the phase difference measurement timing C. In order to perform the calculation in consideration of the fluctuation of the monitor signal (b), the CAPA area detection signal (a) is generated by predicting the CAPA area detection signal waveform one sector period before, and the monitor signal (b) After estimating the amount of variation, it may be assumed that the CAPA region detection signal is generated as a signal that remains high for, for example, 5 μs before and after the CAPA region passage period. Thereby, the change of the monitor signal (b) can be taken into consideration only by changing the variable Pc. In the following description, it is assumed that the above-mentioned assumption that “the time width Pc = 30 μs when the CAPA region detection signal is High” is a number in consideration of the above.

(Pa-Pc) / (Ps-2 * Pa) = 17.54 (Equation 3)
Therefore, the phase difference measurement timing D is the 17th CAPA region counted from the phase difference measurement timing C. The phase difference can be accurately measured from the phase difference measurement timing B to the phase difference measurement timing E. The number of phase difference measurement timings existing between them is expressed by the following equation.

2 * Int {(Pa-Pc) / (Ps-2 * Pa)}-1 + 2 = 35 (Equation 4)
(However, Int () is a function that returns the largest integer that does not exceed that value.)
That is, the average value can be calculated using 35 consecutive accurate phase difference measurement data, and the loop gain adjustment accuracy can be improved.

As a result, in the period until the loop gain adjustment is completed, it is possible to avoid the overlap of the fall of the signal obtained by binarizing the monitor signal and the fluctuation of the monitor signal when passing through the CAPA region, or to reduce the number of times of overlap. There is. That is, phase difference measurement can be performed while minimizing the influence of passing through the CAPA region, and the accuracy of loop gain adjustment is improved.
In the fourth to sixth embodiments, since the sector period depends on the rotation speed of the spindle motor, the period of the adjustment reference signal is appropriately set according to the rotation speed of the spindle motor.

  In the fourth to sixth embodiments, the phase difference measurement used in the first embodiment has been described. However, it is obvious that the present invention can be similarly applied to the amplitude ratio measurement used in the third embodiment.

  In the case of measuring the phase difference described above (Embodiments 1, 2, 4, 5 and 6 in the present invention), the phase difference is measured at the falling edge of the signal obtained by binarizing the adjustment reference signal and the monitor signal. However, the phase difference may be measured at the rising edge of each binarized signal, or the falling edge and the rising edge may be used in combination.

  In the above embodiments, the header area is called the CAPA area. However, the present invention was invented with respect to an optical disc in which a header area in which a servo error signal fluctuates when passing periodically exists on a track. The disk format of the header area is not limited to the CAPA format.

  In the above embodiment, when determining whether the open loop gain has a desired characteristic, the two input signals added by the adder 107 are monitored and the phase difference or the amplitude ratio is measured. The signal to be performed is not limited to this. For example, the adjustment reference signal and the adder output signal may be monitored for measurement. As described above, any configuration may be used as long as the adjustment reference signal is injected into the servo loop, the response of the servo system to the adjustment reference signal is detected, and the phase difference or the amplitude ratio is measured. Absent.

  Furthermore, although the above embodiment has been described using the tracking servo, the present invention can be similarly applied to the focus servo.

It is a block diagram which shows Example 1 of this invention. It is a block diagram which shows Example 3 of this invention. It is a wave form diagram explaining Example 1 of this invention. It is a flowchart of Example 1 of this invention. It is a wave form diagram explaining Example 2 of this invention. It is a wave form diagram explaining Example 3 of this invention. It is a flowchart of Example 3 of the present invention. It is a wave form diagram explaining Example 4 of this invention. It is a flowchart of Example 4 of the present invention. It is a wave form diagram explaining Example 5 of this invention. It is a wave form diagram explaining Example 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Optical disk which has CAPA area | region 102 ... Objective lens, 103 ... Optical pick-up, 104 ... Spindle motor, 105 ... Tracking error generation circuit, 106 ... Variable gain circuit, 107 ... Adder, 108 ... Tracking control circuit, 109 ... Driver Circuit 110 110 RF signal generation circuit 111 CAPA region detection circuit 112 adjustment reference signal control circuit 113 adjustment reference signal generation circuit 114 band pass filter 115 phase difference measurement circuit 116 loop gain adjustment Control circuit, 117, amplitude ratio measuring circuit, 201, tracking error signal, 202, adjustment reference signal, 203, CAPA area detection signal, 204, monitor signal

Claims (9)

An optical disc apparatus for recording or reproducing information on an optical disc having a header area periodically on a track,
Light detection means for outputting an electrical signal corresponding to the amount of light reflected from the optical disc;
Servo error signal generating means for generating a servo error signal from the output signal of the light detecting means;
Drive signal generating means for generating a drive signal for driving the servo actuator from the servo error signal;
RF signal generation means for generating an RF signal from the output of the light detection means;
Header area detection means for detecting a header area from the RF signal and generating a header area detection signal;
Adjustment reference signal generation means for generating an adjustment reference signal for servo gain adjustment of a predetermined frequency;
Adding means for adding the adjustment reference signal to the servo loop to be gain adjusted;
Signal comparison means for comparing the adjustment reference signal with a response of the servo loop to the adjustment reference signal;
Servo gain adjustment instruction means for instructing servo gain adjustment according to the comparison result of the signal comparison means;
Servo gain adjusting means for adjusting the servo gain in accordance with instructions of the servo gain adjustment instruction means;
Adjustment reference signal control means for controlling the output start timing and output start phase of the adjustment reference signal,
The adjustment reference signal control means controls the adjustment reference signal generation means so that the phase of the adjustment reference signal has a predetermined phase difference with respect to the phase of the header area detection signal.   2. An optical disc apparatus according to claim 1, wherein information is recorded in a CAPA format in the header area.   2. The optical disk apparatus according to claim 1, wherein the servo error signal is a tracking error signal, and the adjustment reference signal is added to a tracking servo loop.   2. The optical disk apparatus according to claim 1, wherein the servo error signal is a focus error signal, and the adjustment reference signal is added to a focus servo loop.   2. The optical disc apparatus according to claim 1, wherein the adjustment reference signal control means starts output of the adjustment reference signal from a predetermined phase after a predetermined time has elapsed after passing through the header area.   2. An optical disc apparatus according to claim 1, wherein a time obtained by multiplying a cycle of the adjustment reference signal according to claim 1 by a first integer is substantially equal to a time obtained by multiplying a cycle between headers by a second integer.   The optical disk apparatus according to claim 1, wherein a period between headers is substantially equal to an integral multiple of a period of the adjustment reference signal.   2. The optical disc apparatus according to claim 1, wherein the signal comparison unit detects a phase difference between the adjustment reference signal and a response signal of the servo loop with respect to the adjustment reference signal.   2. The optical disc apparatus according to claim 1, wherein the signal comparison unit detects an amplitude ratio between the adjustment reference signal and a response signal of the servo loop with respect to the adjustment reference signal.

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