JP3785884B2 - Disk unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk device for recording and / or reproducing an exchangeable disk-shaped recording medium, and in particular, a track in which a track groove of a disk-shaped recording medium is slightly meandered (wobbled) compared to a track pitch during recording. The present invention relates to a disk device that reproduces the wobble signal.
[0002]
[Prior art]
Conventionally, in an optical disk recording / reproducing apparatus, data is recorded / reproduced by causing a light beam to follow the center of a target track. Some recordable optical disks are formed such that the track grooves meander slightly compared to the track pitch. The meandering of the track groove is called a wobble, and the amplitude of the wobble is set to an amplitude width that does not affect the tracking, and the frequency of the wobble is compared with the tracking control band so as not to affect the tracking. Is set high enough.
[0003]
Therefore, the light beam does not follow the wobble of the track and can trace the center of the track. However, the signal obtained by tracing the track with the light beam includes a signal component (wobble signal) caused by the wobble of the track groove.
[0004]
The wobble signal is a signal obtained from a photoelectric conversion element arranged corresponding to the inner peripheral side in the disk radial direction of the two-divided photoelectric conversion elements (photoelectric sensors) provided in the optical pickup and the outer peripheral side of the disk. It is detected by passing a push-pull signal obtained by taking a difference from a signal obtained from a correspondingly arranged photoelectric conversion element through a band-pass filter.
[0005]
In the optical disc recording / reproducing apparatus, the track address to be recorded is detected and the spindle motor is controlled by CLV (constant linear velocity) by the output signal of the PLL circuit (phase locked loop) that oscillates in synchronization with the output signal of the bandpass filter. The spindle control signal is obtained.
[0006]
As a conventional technique of a bandpass filter (BPF) for obtaining a wobble signal as described above, Japanese Patent Publication No. 2927315 has a digital bandpass filter configuration as a bandpass filter for extracting the wobble signal. It is described that the center frequency of the digital bandpass filter is made variable with respect to the change of the wobble frequency by obtaining the sampling clock of the bandpass filter from the oscillation frequency of the PLL circuit.
[0007]
[Problems to be solved by the invention]
By the way, according to the prior art (Patent Publication No. 2927315) in which the bandpass filter for extracting the wobble signal as described above is a digital filter, the bandpass filter output signal is substantially a sine wave signal. When the signal-to-noise ratio of the wobble signal is not sufficiently obtained in the binarization process, the jitter occurs in the pulse edge after waveform shaping due to the noise in the vicinity of the zero cross, and in the worst case, the PLL cannot be synchronized. There is a risk of becoming.
[0008]
In addition, the PLL circuit synchronized with the bandpass filter output detects a phase shift between the edges of the pulse, or makes the H (high) level time and the L (low) level time of the exclusive OR output equal. Since the phase comparator is configured, the period of the phase comparison can be performed only with the period of the wobble frequency, and the time until the PLL is synchronized is limited.
[0009]
The present invention has been made in view of the above-described problems, and can synchronize the PLL even when the signal-to-noise ratio of the wobble signal is low, and the phase comparison period is the period of the wobble frequency. The present invention is not limited to this, and an object of the present invention is to provide a disk device that can shorten (accelerate) the time until the PLL is synchronized.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the disk apparatus according to the present invention is a disk apparatus using a disk-shaped recording medium in which concentric or spiral tracks meander in the disk radial direction. A first band passing means having a frequency band of a sinusoidal meander signal corresponding to the meandering of the track as a pass band; a frequency band of a sinusoidal meandering signal corresponding to the meandering of the track being a pass band; A second bandpass means for outputting a signal having a phase difference of 90 degrees with respect to an output signal of the first bandpass means; an output signal of the first bandpass means and an output signal of the second bandpass means; A phase calculating means for calculating a phase of a sinusoidal meander signal corresponding to the meandering of the track, and a phase of the sinusoidal meander signal calculated by the phase calculating means; And a phase synchronization means constituting a phase-locked loop synchronized to the phase.
[0011]
According to a second aspect of the present invention, there is provided a disc device comprising a demodulating means for demodulating the frequency modulation data of the meandering signal from the frequency data obtained from the phase locked loop.
[0012]
That is, the disk device according to the present invention outputs a first band pass means (first band pass filter) and a signal that is 90 degrees out of phase with respect to the output signal of the first band pass means. 2 band-pass means (second band-pass filter), when the output of the first band-pass means is represented by E and the output of the second band-pass means is represented by F, for example, a sinusoidal meander The phase amount of the signal (sinusoidal wobble signal) is calculated by, for example, arctan (E / F) calculation, and a phase-locked loop (PLL) that compares the phase with the VCO (voltage controlled oscillator) output phase is configured. I am doing so.
[0013]
As a result, the signal for performing the phase comparison of the PLL is not a binarized signal but a wobble signal (sinusoidal meandering signal) that is an output of the bandpass filter (bandpass means), and therefore the phase comparison period Can be set sufficiently shorter than the period of the wobble frequency, so that the PLL synchronization pull-in can be speeded up. Further, since the phase information of the sinusoidal wobble signal is detected at all sampling times for phase comparison, the PLL can be synchronized even when the signal-to-noise ratio of the wobble signal is low.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a disk device according to the present invention will be described in detail with reference to the drawings. First, FIG. 1 shows a configuration (mainly a wobble signal playback system) of a disk recording / playback apparatus according to an embodiment of the present invention.
[0015]
In FIG. 1, an optical disk 1 is driven to rotate by a spindle motor 2. Reading and writing of data on the surface of the optical disc 1 is performed by an optical pickup 3, and the optical pickup 3 is positioned near a target track by a pickup coarse motion motor (not shown).
[0016]
The objective lens in the optical pickup 3 is positioned by a focus actuator (not shown) that can move in the disc rotation axis direction so that the light beam is focused on the recording / reproducing surface on the optical disc 1. The objective lens in the optical pickup 3 is positioned by a tracking actuator (not shown) that can move in the disc radial direction so that the light beam follows the concentric or spiral recording / reproducing track on the optical disc 1. Yes.
[0017]
Among the two-divided photoelectric sensors provided in the optical pickup 3, an output signal of a photoelectric sensor (hereinafter referred to as an inner peripheral photoelectric sensor signal A) arranged corresponding to the inner peripheral side in the disk radial direction, and the disk The output signals of the photoelectric sensors arranged corresponding to the outer peripheral side in the radial direction (hereinafter referred to as the outer peripheral photoelectric sensor signal B) output current signals proportional to the amounts of light incident on the respective photoelectric sensors. The inner peripheral photoelectric sensor signal A is input to the current-voltage conversion circuit 6, and the outer peripheral photoelectric sensor signal B is supplied to the current-voltage conversion circuit 7.
[0018]
The current-voltage conversion circuits 6 and 7 convert photoelectric sensor signals, which are supplied current signals, into voltage signals. The output signals of these current / voltage conversion circuits 6 and 7 are supplied to a push-pull signal generation circuit 8.
[0019]
The push-pull signal generation circuit is a difference signal between a voltage signal obtained by current-voltage conversion of the inner peripheral photoelectric sensor signal A and a voltage signal obtained by current-voltage conversion of the outer peripheral photoelectric sensor signal B. A push-pull signal C is generated. The push-pull signal C is supplied to an AD (analog-digital) converter 10.
[0020]
The AD converter 10 converts the input push-pull signal C into a digital signal (hereinafter referred to as push-pull digital data D). The push-pull digital data D output from the AD converter 10 is supplied to the first band pass filter 12 and the second band pass filter 13.
[0021]
The first band-pass filter 12 is a digital band-pass filter having a wobble frequency of a wobble signal included in the push-pull signal as a center frequency, and push-pull digital data D obtained by subjecting the push-pull signal C to A / D conversion. The wobble signal component is extracted from the signal and output as the first bandpass filter output signal E.
[0022]
The second band-pass filter 13 is a digital band-pass filter whose center frequency is the wobble frequency of the wobble signal included in the push-pull signal, and is wobbled from the push-pull digital data D obtained by AD converting the push-pull signal C. At the same time as extracting the signal component, the wobble signal component is output as a second bandpass filter output signal F whose phase is advanced by 90 degrees with respect to the first bandpass filter output signal E. Note that a Hilbert filter, a phase shift filter, or the like is known as such a filter that causes a phase shift of 90 degrees. The first band pass filter output signal E and the second band pass filter output signal F are supplied to the phase calculator 16.
[0023]
The phase calculator 16 will be described below with reference to FIG. In addition, since the second band pass filter output signal F is a signal with a phase advance of 90 degrees with respect to the first band pass filter output signal E, when the first band pass filter output signal E is a sin signal, The second bandpass filter output signal F can be considered as a cos signal.
[0024]
In FIG. 2, the sin signal (first bandpass filter output signal E) and the cos signal (second bandpass filter output signal F) are supplied to the absolute value calculator 24.
[0025]
The absolute value calculator 24 calculates the absolute value signal M of the sin signal (E) and the absolute value signal N of the cos signal (F) by calculation, and from the magnitude relationship between the sin signal (E) and the cos signal (F). As shown in FIG. 3, area determination is performed by dividing one cycle into four areas (e0 to e3), and the area determination signal P is output as follows.
[0026]
(1) If sin ≧ 0 and cos ≧ 0, the region discrimination signal P = e3 is output (2) If sin ≧ 0 and cos <0, the region discrimination signal P = e2 is output (3) sin <0 and cos If <0, the region determination signal P = e0 is output (4) If sin <0 and cos ≧ 0, the region determination signal P = e1 is output. This region determination signal P is supplied to the offset adder / subtractor 32. The absolute value signal M of the sin signal (E) and the absolute value signal N of the cos signal (F) are supplied to the division calculator 28.
[0027]
The division calculator 28 calculates a tan signal O that is sin / cos from the absolute value signal M of the sin signal (E) and the absolute value signal N of the cos signal (F). The tan signal O is supplied to the inverse tan table reference unit 30.
[0028]
The inverse tan table reference unit 30 obtains and outputs the arctan signal Q from the inverse tan function data that outputs from 0 [rad] to π / 2 [rad] as shown in FIG. The arctan signal Q is supplied to the offset adder / subtractor 32.
[0029]
The offset adder / subtractor 32 adds / subtracts the following offset amount to / from the arctan signal Q based on the region determination signal P from the absolute value calculator 24, and expresses the phase of the wobble signal from 0 [rad] to 2π [rad]. Input phase data G is output.
[0030]
(1) If the area determination signal P = e3, the input phase data G = arctan is output. (2) If the area determination signal P = e2, the input phase data G = π-arctan is output. (3) The area determination signal P = If e0, the input phase data G = π + arctan is output. (4) If the region discrimination signal P = e1, the input phase data G = 2π-arctan is output. In this way, the phase calculator 16 outputs the wobble signal as described above. Since the phase is calculated from the sine component and the cos component, accurate phase detection is possible without receiving the amplitude fluctuation of the wobble signal. Further, since the inverse tan table reference unit 30 is a table from 0 [rad] to π / 2 [rad] based on the region determination signal P, the scale of the reference table can be reduced. The function in FIG. 4 changes greatly with respect to the input value when the output value is near 0 [rad], but there is almost no change with respect to the input value near π / 2 [rad]. It is desirable to configure the reference table to be constant.
[0031]
The input phase data G that is the output data of the phase calculator 16 and the VCO phase data J that is the output data of a digital VCO (voltage controlled oscillator) 23 described later are supplied to the phase comparison calculator 19.
[0032]
The phase comparison calculator 19 calculates the phase difference between the input phase data G and the digital VCO phase data J, and outputs the phase error data H. The phase error data H is supplied to the loop filter calculator 21.
[0033]
The loop filter calculator 21 is configured as shown in FIG. In the loop filter calculator 21 shown in FIG. 5, the phase error data H is supplied to an adder 41 and a coefficient multiplier 42.
[0034]
Output data from the adder 41 is supplied to a coefficient multiplier 44 and a delay unit 43. The delay unit 43 delays the output data of the adder 41 by one sample and feeds it back to the adder 41. Therefore, the adder 41 adds (integrates) the supplied phase error data H and the output data of the adder 41 delayed by one sample by the delay unit 43.
[0035]
The coefficient multiplier 44 multiplies the output data of the adder 41 by a coefficient ki. The multiplication result data is supplied to the adder 45. The coefficient multiplier 42 multiplies the phase error data H by the coefficient kp. The multiplication result data is supplied to the adder 45.
[0036]
The adder 45 adds the data multiplied by the coefficient ki by the coefficient multiplier 44 and the data multiplied by the coefficient kp by the coefficient multiplier 42. The output data of the adder 45 is output as the VCO manipulated variable I of the digital VCO calculator 23 at the subsequent stage.
[0037]
That is, in the loop filter computing unit 21 shown in FIG. 5, the proportional operation amount obtained by multiplying the phase error data H by the coefficient kp by the coefficient multiplier 42 and the phase error data H by the adder 41 and the delay unit 43. The integration operation amount obtained by multiplying the integrated value by the coefficient ki by the coefficient multiplier 44 is added by the adder 45 to obtain the VCO operation amount I.
[0038]
Next, the digital VCO calculator 23 is configured as shown in FIG. In the digital VCO calculator 23 shown in FIG. 6, the VCO manipulated variable I supplied from the loop filter calculator 21 is supplied to the adder 51.
[0039]
The VCO free-running frequency data R set in advance is also supplied to the adder 51, and the adder 51 performs frequency calculation for adding the VCO manipulated variable I to the VCO free-running frequency data R. Data obtained by this frequency calculation is the current oscillation frequency data K, and the oscillation frequency data K is supplied to the frequency discriminator 35 and the adder 52 shown in FIG.
[0040]
Output data of the adder 52 is supplied to a mod (2π) calculator 54 and a delay unit 53. The delay unit 53 delays the output data of the adder 52 by one sample and feeds it back to the adder 52. The adder 52 adds (accumulates) the supplied oscillation frequency data 34 and the output data of the adder 52 delayed by one sample by the delay unit 53.
[0041]
In the mod (2π) calculation, the mod (2π) calculation is performed on the output data of the adder 52, and the calculation result is supplied as digital VCO phase data J to the phase comparison calculator 19 in FIG.
[0042]
That is, in the digital VCO computing unit 23, the adder 51 adds the VCO manipulated variable I to the free-running frequency data R to generate oscillation frequency data, and this oscillation frequency data K is further added to the adder 52 and the delay unit 53. The phase data is generated by integration, but the phase data is repeated at (2π) [rad]. Therefore, in the digital VCO computing unit 23, mod (2π) computing unit 54 further performs mod (2π) computation. The calculation result data is supplied to the phase comparison calculator 19 as digital VCO phase data J.
[0043]
The digital VCO calculator 23 operates in synchronization with the wobble signal by such a phase locked loop. In addition, in an optical disc in which the wobble signal is frequency-modulated according to, for example, track address information, the oscillation frequency data K output from the digital VCO calculator 23 is supplied to the frequency discriminator 35, and the frequency discriminator 35 concerned. By demodulating the frequency-modulated data, the track address information can be obtained from the demodulated data L.
[0044]
As is apparent from the above description, the optical disc recording / reproducing apparatus of the present embodiment has the first bandpass filter output signal E and the first bandpass filter output signal E that are 90 degrees out of phase with each other. 2 band-pass filter output signal F and the arctan (E / F) calculation using these first and second band-pass filter output signals E and F, thereby generating a phase amount (G = Arctan (E / F)) and a phase comparison is made between the phase and the VCO output phase (J).
[0045]
That is, a sine wave wobble signal extracted by a band pass filter is used as a signal for performing phase comparison of the PLL, instead of a binarized signal. For this reason, the period for performing the phase comparison can be set sufficiently shorter than the period of the wobble frequency, and the speed of PLL pull-in can be increased.
[0046]
Since the phase information of the sinusoidal wobble signal is detected at all sampling times for phase comparison, the PLL can be synchronized even when the signal-to-noise ratio of the wobble signal is low. .
[0047]
Finally, the present invention is not limited to the above-described embodiment described as an example. For example, as long as the recording medium has a wobbled recording track, the present invention is not limited to the above-described optical disk, but other disks. However, various modifications can be made in accordance with the design and the like as long as the technical idea according to the present invention does not depart from the technical idea of the present invention. Of course there is.
[0048]
【The invention's effect】
The disk device according to the first aspect of the present invention generates a sinusoidal meandering signal corresponding to a meandering track and a signal having a phase difference of 90 degrees by the first bandpass means and the second bandpass means. By calculating the phase of the sinusoidal meandering signal from the output signals of the first and second bandpass means and constructing a phase-locked loop synchronized with the phase based on the phase of the sinusoidal meandering signal PLL synchronization can be achieved even when the signal-to-noise ratio of the wobble signal is low, and the period of phase comparison is not limited to the period of the wobble frequency, and the time until the PLL is synchronized is shortened (Speeding up).
[0049]
In the disk device according to the second aspect of the present invention, when the frequency modulation data of the meandering signal is demodulated from the frequency data obtained from the phase-locked loop, for example, the track address information is recorded as the meandering signal. In addition, track address information can be obtained from the demodulated data.
[0050]
That is, according to the present invention, the phase comparison of the PLL (phase-locked loop) is performed using the sinusoidal meander signal (sine wave-like wobble signal) extracted by the bandpass means (bandpass filter). Can be set sufficiently shorter than the wobble frequency cycle, and therefore PLL synchronization can be performed at high speed.
[0051]
Further, since the present invention detects the phase information of the sinusoidal wobble signal at all sampling times for phase comparison, the PLL can be synchronized even when the signal-to-noise ratio of the wobble signal is low.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration (mainly a wobble signal reproduction system) of an optical disk recording / reproducing apparatus as an embodiment of a disk apparatus according to the present invention.
FIG. 2 is a block diagram showing a specific configuration example of a phase calculator provided in the optical disc recording / reproducing apparatus of the embodiment.
FIG. 3 is a waveform diagram used for explaining the operation of the absolute value calculator of the phase calculator provided in the optical disc recording / reproducing apparatus of the embodiment.
FIG. 4 is a diagram used for explaining the operation of the inverse tan table reference unit of the phase calculator provided in the optical disc recording / reproducing apparatus of the embodiment.
FIG. 5 is a block diagram showing a specific configuration example of a loop filter calculator provided in the optical disc recording / reproducing apparatus of the embodiment.
FIG. 6 is a block diagram showing a specific configuration example of a digital VCO calculator provided in the optical disc recording / reproducing apparatus of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor, 3 ... Optical pick-up, 6, 7 ... Current voltage conversion circuit, 8 ... Push-pull signal generation circuit, 10 ... AD converter, 12 ... 1st band pass filter, 13 ... Second band-pass filter, 16 ... phase calculator, 19 ... phase comparison calculator, 21 ... loop filter calculator, 23 ... digital VCO calculator, 24 ... absolute value calculator, 28 ... divide calculator, 30 ... reverse tan table reference device, 32 ... offset adder / subtractor, 35 ... frequency discriminator, A ... inner peripheral photoelectric sensor signal, B ... outer photoelectric sensor signal, C ... push pull signal, D ... push pull digital data, E ... first 1 band-pass filter output signal, F ... second band-pass filter output signal, G ... input phase data, H ... phase error data, I ... VCO manipulated variable, J ... digital V O phase data, K ... oscillation frequency data, L ... demodulation data, M ... sin signal absolute value signal, N ... cos signal absolute value signal, O ... tan signal, P ... region discrimination signal, Q ... arctan signal, R ... VCO free-running frequency data

Claims (2)

In a disk apparatus using a disk-shaped recording medium in which concentric or spiral tracks meander in the disk radial direction,
First band passing means having a frequency band of a sinusoidal meander signal corresponding to the meandering of the track as a pass band;
Second band pass means for setting a frequency band of a sinusoidal meander signal corresponding to the meander of the track as a pass band and outputting a signal having a phase different by 90 degrees with respect to the output signal of the first band pass means; ,
Phase computing means for computing the phase of a sinusoidal meander signal corresponding to the meandering of the track from the output signal of the first bandpass means and the output signal of the second bandpass means;
A disk apparatus comprising: a phase synchronization means that constitutes a phase locked loop synchronized with the phase based on the phase of the sinusoidal meander signal calculated by the phase calculation means. 2. The disk apparatus according to claim 1, further comprising demodulation means for demodulating frequency modulation data of the meandering signal from frequency data obtained from the phase-locked loop.

Images