JP3797071B2 - Optical disc recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk recording / reproducing apparatus, and particularly reproduces the above prepits on a writable optical disk in which concentric or spiral tracks meander in a sine wave shape in the radial direction and prepits are formed in advance between the tracks. The present invention relates to an optical disc recording / reproducing apparatus that records information while recording information.
[0002]
[Prior art]
In an optical disc recording / reproducing apparatus, a light beam is caused to follow the center of a target track that is concentric or spiral on a writable optical disc, and an information signal is recorded or a recorded information signal is reproduced. The track groove of the optical disk is formed to meander slightly compared to the track pitch. This meandering track is called a wobble, and its amplitude is set to be sufficiently higher than the tracking control band so that its amplitude does not affect tracking. For this reason, the light beam does not follow the wobble and traces almost the center of the track.
[0003]
The light beam from the optical pickup is reflected by the optical disc, and the reflected light is received by a photoelectric conversion element in the optical pickup and subjected to photoelectric conversion. Here, the reflected light is photoelectrically converted by the photoelectric conversion element on the inner circumference side and the photoelectric conversion element on the outer circumference side with respect to the radial direction of the optical disc, and a push-pull signal obtained by taking a difference between these signals is converted into a wobble frequency. Is passed through a bandpass filter (BPF) that passes through the wobble signal.
[0004]
In a conventional optical disc recording / reproducing apparatus, the wobble signal detected by the BPF is supplied to a phase-locked loop (PLL) circuit, and the optical disc rotating spindle motor synchronized with the wobble signal is controlled at a constant linear velocity (CLV). For generating a spindle control signal, and obtaining a gate signal for extracting a pre-pit signal formed in advance between lands between tracks, and detecting the track address to be recorded from the pre-pit signal extracted from the reproduction signal with this gate signal. (Japanese Patent Laid-Open No. 9-326138).
[0005]
In this conventional optical disc recording / reproducing apparatus, a gate signal for extracting a pre-pit signal formed in advance on a track of an optical disc is obtained from a voltage controlled oscillator (VCO) in a PLL circuit synchronized with a binarized signal of a BPF output signal.
[0006]
[Problems to be solved by the invention]
By the way, in a conventional optical disc recording / reproducing apparatus that obtains a gate signal for extracting a prepit signal from a VCO in a PLL circuit synchronized with a binarized signal of such a BPF output wobble signal, the wobble signal passes through the BPF. On the other hand, the pre-pit signal does not pass through the BPF. As shown in FIG. 7A, the frequency-gain characteristic of the BPF is such that the center frequency f0 of the pass band is set equal to the wobble signal frequency, and the frequency-phase characteristic of the BPF is the same as that shown in FIG. As shown in FIG. 3, the BPF input / output signal phase changes from a leading phase to a lagging phase before and after the center frequency f0.
[0007]
Therefore, at the disc linear velocity at which the wobble signal frequency becomes the center frequency f0 of the pass band of the BPF, the radial position of the optical pickup is set even if the prepit signal is set at the center position of the gate signal for extracting the prepit signal. Immediately after the change in the track seek operation, the spindle motor for rotating the optical disc cannot follow the operation to keep the linear velocity constant, and the wobble signal frequency is shifted from the center frequency f0 of the pass band of the BPF. Thus, the phase relationship between the prepit extraction gate signal generated from the signal passing through the BPF and the prepit signal not passing through the BPF deviates from the above set state.
[0008]
In this case, the phase relationship between the prepit extraction gate signal and the prepit signal that does not pass through the BPF remains deviated from the above set state until the spindle motor is set to a predetermined linear velocity. Therefore, since the track address information obtained from the prepit data cannot be read, it takes time to seek the target track.
[0009]
The present invention has been made in view of the above points, and provides an optical disc recording / reproducing apparatus capable of reproducing prepit data even when the linear velocity changes and the wobble signal frequency deviates from the center frequency of the pass band of the BPF. With the goal.
[0010]
Another object of the present invention is to provide an optical disc recording / reproducing apparatus capable of shortening a track seek time.
[0011]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides an information signal to an optical disc in which concentric or spiral tracks are formed to meander slightly compared to the track pitch and a pre-pit signal is recorded in advance. In an optical disc recording / reproducing apparatus for recording and reproducing, a filter circuit for selecting a frequency of a wobble signal based on a meandering track from a reproduction signal of the optical disc and a reproduction signal of the optical disc are compared with a predetermined threshold value, A comparator that outputs pit pulses, a phase-locked loop circuit that generates a signal synchronized with the phase of the wobble signal output from the filter circuit, and outputs the oscillation frequency data and phase data of the signal from the VCO, and a phase-locked loop the oscillation frequency data which is output from the VCO in the circuit, slow constant signal of the filter circuit A delay phase amount calculating circuit for generating a delayed phase data by multiplying the data indicating the time, the delay phase data, by correcting the phase data outputted from the VCO of the phase locked loop circuit, a delay corrected phase data A phase corrector to generate, a prepit gate signal generator to generate a gate signal for extracting a prepit signal based on phase data after delay correction , and a prepit by discriminating a prepit signal from an optical disc reproduction signal by the gate signal It has a configuration having a pre-pit data discrimination circuit for outputting as data.
[0012]
In this invention, the constant signal delay time of the filter circuit is calculated as the phase delay amount at the signal frequency of the current phase-locked loop circuit that is phase-locked to the wobble signal, and the obtained delay phase data is output from the phase-locked loop circuit Since the phase data is corrected and the gate signal is generated based on the corrected phase data, the gate signal always has a constant phase with respect to the wobble signal when the filter circuit is input, regardless of the wobble signal frequency. Can be.
[0013]
Further, the filter circuit is configured such that the center frequency of the pass band is set to the frequency of the wobble signal when the relative linear velocity between the optical disc and the recording / reproducing optical beam is set to a predetermined value, and the pass band is It is set to a value of 1, and before the relative linear velocity is settled to a predetermined value, a variable band filter in which the pass band is set to a second value wider than the first value is used. This is desirable because it is possible to suppress a decrease in the wobble signal component in the output signal of the filter circuit before settling to a value.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of an optical disk recording / reproducing apparatus according to the present invention. In the figure, an optical disk 1 is a writable optical disk in which concentric or spiral tracks meander in a sine wave shape with respect to the radial direction of the disk and pre-pits are formed in advance between the tracks. Is done.
[0015]
Recording of an information signal to the optical disc 1 and reproduction of a recording signal of the optical disc 1 are performed by a light beam emitted from a laser light source in the pickup 3 and reflected light obtained by reflecting the light beam on the optical disc 1. Done. The pickup 3 is positioned near the target track by a pickup coarse motion motor (not shown).
[0016]
In addition, the objective lens in the pickup 3 is a focus actuator (see FIG. 5) that can move in the rotation axis direction of the optical disc 1 (direction orthogonal to the recording / reproduction surface) so that the light beam is focused on the recording / reproduction surface on the optical disc 1. (Not shown). The objective lens in the pickup 3 is positioned by a tracking actuator (not shown) that can move in the disc radial direction so as to follow a concentric or spiral recording / reproducing track on the optical disc 1.
[0017]
The reflected light from the optical disc 1 passes through an optical system such as an objective lens in the pickup 3 and is received by the photoelectric conversion element on the inner peripheral side in the disc radial direction and the photoelectric conversion element on the outer peripheral side in the pickup 3. It is photoelectrically converted. The inner peripheral photocurrent output from the inner peripheral photoelectric conversion element is input to the current-voltage conversion circuit 4, and the outer peripheral photocurrent output from the outer peripheral photoelectric conversion element is input to the current-voltage conversion circuit 5. And converted into voltage signals, respectively.
[0018]
The output voltage signals of the current-voltage conversion circuits 4 and 5 are supplied to the push-pull signal generation circuit 6 and subtracted to obtain a push-pull signal a that is the difference between them. The push-pull signal a is, for example, a signal shown in FIG. 2A, which is supplied to the A / D converter 7 of FIG. 1 and converted into a digital signal, while being supplied to the prepit pulse detection comparator 8. A pre-pit pulse b as shown in FIG. 2 (B) is obtained depending on whether or not it is equal to or greater than a predetermined threshold value. That is, pre-pits recorded in advance on the optical disc 1 are obtained as signals having a level equal to or higher than a predetermined threshold in the push-pull signal a. When this predetermined threshold is exceeded, a pre-pit reproduction signal is obtained. Is output from the pre-pit pulse detection comparator 8 as the pre-pit pulse b.
[0019]
The digital data of the push-pull signal a output from the A / D converter 7 is supplied to the BPF 9. The BPF 9 is a digital filter that uses the wobble signal frequency as the center frequency of the pass band, and selects the frequency of the wobble signal included in the input digital data.
[0020]
FIG. 3 shows a configuration diagram of an example of the BPF 9. As shown in the figure, the BPF 9 has 9 stages cascaded, delay elements 101 to 109 each delaying by unit time (equal to the sampling period of the A / D converter 7), and inputs of the delay elements 101 to 109. Multipliers 110 to 118 for which signals are branched and inputted and multiplied by coefficients K0 to K8, a multiplier 119 for multiplying the output signal of the delay element 109 by a coefficient K9, and output signals of the multipliers 110 to 119 are added. Thus, an FIR (non-recursive) digital filter composed of an adder 120 for outputting an output signal is provided. In this BPF 9, the coefficients K0 to K9 are oddly symmetric with respect to the coefficient K5 (K9 = −K0, K8 = −K1, K7 = −K2, K6 = −K3, K5 = −K4), or even symmetric ( K9 = K0, K8 = K1, K7 = K2, K6 = K3, K5 = K4).
[0021]
Returning to FIG. 1 again, the wobble signal frequency band signal extracted from the BPF 9 is supplied to the phase calculator 10, converted into phase data, and then supplied to the phase comparator 11. The phase comparator 11 performs phase comparison between phase data from the phase calculator 10 and digital VCO phase data e from a digital VCO (Voltage Controlled Oscillator) 13 described later, and phase error data corresponding to the phase difference. Is supplied to the loop filter calculator 12.
[0022]
The loop filter computing unit 12 is configured as shown in FIG. 4, for example, and the phase error data output from the phase comparator 10 is integrated by an integrating circuit including an adder 21 and a delay element 22, and the integrated value is obtained. Is added by the adder 25 to the integration manipulated variable obtained by multiplying the multiplier 23 by the coefficient KI and the proportional manipulated variable obtained by multiplying the phase error data by the coefficient KP by the multiplier 24. Calculate the quantity.
[0023]
The VCO manipulated variable extracted from the loop filter computing unit 12 is supplied to the digital VCO 13 of FIG. 1 to variably control its output oscillation frequency. The digital VCO 13 is configured as shown in FIG. 5, for example, and performs a frequency calculation in which an adder 31 adds preset free-running frequency data to the VCO manipulated variable extracted from the loop filter calculator 12. The obtained data is output as the current oscillation frequency data f, and further integrated by an integrating circuit including an adder 32 and a delay element 33 to generate phase data.
[0024]
Since this phase data repeats 2π (rad), the computing unit 34 performs mod (2π) operation (addition operation modulo 2π) on the phase data, so that the digital VCO phase data e is obtained. Generated. The digital VCO phase data e is input to the phase comparator 11 shown in FIG. 1 and phase-compared with the phase data from the phase calculator 10. A loop feedback loop comprising the phase comparator 11, the loop filter arithmetic unit 12 and the digital VCO 13 constitutes a phase locked loop (PLL), and a signal (oscillation frequency data f and phase data e) synchronized with the wobble signal. ) Is generated and output.
[0025]
The digital VCO phase data e and the oscillation frequency data f output from the digital VCO 13 are respectively supplied to the pre-pit gate generator 14 in FIG. The pre-pit gate generator 14 is configured as shown in FIG. 6, for example. Here, since the input oscillation frequency data f is frequency data for each conversion cycle of the A / D converter 7, the data for each sample varies. Therefore, in order to obtain an average frequency corresponding to the number of delayed samples of the BPF 9, the prepit gate generator 14 performs a moving average calculation of the input oscillation frequency data f by the frequency data moving average calculator 41 of FIG. For example, when the frequency data f of the current sample is set to f (n), the frequency data moving average calculator 41 has the past 8 samples f (n-7), f (n-6), f (n-5), Average frequency data is obtained by taking the sum of f (n-4), f (n-3), f (n-2), f (n-1), and f (n) and multiplying the sum by 1/8. Is generated.
[0026]
The pre-pit gate generator 14 inputs the above-described average frequency data generated by the frequency data moving average calculator 41 to the delay phase amount calculator 42, and multiplies it by the preset delay time data. To obtain delayed phase data. The preset delay time data is data indicating a constant signal delay time from the input end of the A / D converter 7 to the output end of the BPF 9 in FIG. 1, and this signal delay time is A / D. It is constant regardless of the frequency of the push-pull signal a input to the converter 7.
[0027]
However, even if the signal delay time is constant, the phase delay amount changes according to the frequency of the push-pull signal a. Therefore, the delay phase amount calculator 42 multiplies the delay time data indicating the constant signal delay time by the average frequency data of the oscillation frequency data f from the digital VCO 13 to thereby obtain the constant signal delay. The time is obtained as delay phase data indicating the phase delay amount at the oscillation frequency of the digital VCO 13.
[0028]
Subsequently, the pre-pit gate generator 14 performs a mod (2π) addition operation on the delay phase data and the digital VCO phase data e from the digital VCO 13 in the phase corrector 43 of FIG. Phase data is generated and supplied to the prebit gate signal generator 44 to generate and output a prepit gate signal c that becomes 1 when the phase data passes 0 and becomes 0 when it passes π. .
[0029]
In this way, the prepit gate signal c as shown in FIG. 2C extracted from the prepit gate generator 14 is combined with the prepit pulse b shown in FIG. It is supplied to the discrimination circuit 15. As shown in FIG. 2D, the prepit data discriminating circuit 15 indicates data “1” when the prepit pulse b exists during the period when the prepit gate signal c is at the H level, and the prepit gate signal c When the pre-pit pulse b does not exist during the H level period, data “0” is indicated to output pre-pit data d including track address information and other information.
[0030]
As described above, according to this embodiment, the constant signal delay time from the input end of the A / D converter 7 to the output end of the BPF 9 is phase-shifted at the current VCO oscillation frequency in phase synchronization with the wobble signal. In the delay phase amount calculator 42, the digital VCO phase data e is corrected with the obtained delay phase data and then the prepit gate signal c is generated. Therefore, the prepit gate is not dependent on the wobble signal frequency. The signal c always has a constant phase with respect to the wobble signal when the BPF 9 is input.
[0031]
For this reason, the push-pull signal a is used even in a period in which the wobble signal does not reach the normal frequency f0 before the relative linear velocity between the light beam and the optical disc 1 is set to a predetermined value immediately after the seek operation. Prepit data can be accurately read by the prepit gate signal c. Accordingly, since the track address information obtained from the pre-pit data can be read immediately after the seek operation, the time to reach the final target track can be shortened as compared with the prior art.
[0032]
The present invention is not limited to the above embodiment. For example, if the wobble frequency deviates from the center frequency of the pass band of the BPF for selecting the wobble frequency (corresponding to BPF 9 in the above embodiment). Since the wobble signal component of the output signal of the BPF is reduced, the passband of the BPF is widened immediately after seeking to suppress the reduction of the wobble signal component of the BPF output signal, and the relative line between the optical disc and the light beam. The pass band of the BPF may be narrowed to a predetermined value after the speed has settled to a predetermined value.
[0033]
As a method of changing the pass band of the BPF, for example, there is a method of switching the coefficients K0 to K9 of the multipliers 110 to 119 of FIG. Thus, even if the pass band of the BPF is variable, the delay time is constant, so that the prepit can be positioned substantially at the center of the prepit gate signal by the method described in the above embodiment.
[0034]
【The invention's effect】
As described above, according to the present invention, the gate signal is always in a constant phase with respect to the wobble signal when the filter circuit is input without depending on the wobble signal frequency. Even during the period when the wobble signal does not reach the normal frequency before the relative linear velocity with the optical disk is set to a predetermined value, the pre-pit data can be accurately read from the reproduction signal by the gate signal. Since the track address information obtained from the pre-pit data can be read immediately after the seek operation, the time to reach the final target track can be shortened as compared with the prior art.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of the present invention.
2 is a timing chart for explaining the operation of the main part of FIG. 1; FIG.
FIG. 3 is a block diagram showing a configuration of an example of a BPF in FIG.
4 is a configuration diagram of an example of a loop filter calculator in FIG. 1. FIG.
5 is a block diagram of an example of a digital VCO in FIG.
6 is a block diagram of an example of a prepit gate generator in FIG. 1. FIG.
FIG. 7 is a diagram showing frequency vs. gain characteristics and frequency vs. phase characteristics of a BPF that frequency-selects a wobble signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk 3 Pickup 6 Push pull signal generation circuit 8 Pre-pit pulse detection comparator 9 Wobble signal frequency selection bandpass filter (BPF)
DESCRIPTION OF SYMBOLS 10 Phase calculator 11 Phase comparator 12 Loop filter calculator 13 Digital VCO (voltage controlled oscillator)
14 Prepit gate generator 15 Prepit data discrimination circuit 41 Frequency data moving average calculator 42 Delay phase amount calculator 43 Phase corrector 44 Prepit gate signal generator a Push-pull signal b Prepit pulse c Prepit gate signal d Pre-pit data e Digital VCO phase data f Oscillation frequency data

Claims (2)

In an optical disc recording / reproducing apparatus that records and reproduces an information signal with respect to an optical disc in which concentric or spiral tracks are slightly meandered compared to the track pitch, and a pre-pit signal is recorded in advance,
A filter circuit for frequency-selecting a wobble signal based on the meandering of the track from the reproduction signal of the optical disc;
Comparing a reproduction signal of the optical disc with a predetermined threshold, and outputting a prepit pulse based on the prepit signal,
A phase-locked loop circuit that generates a signal synchronized with the phase of the wobble signal output from the filter circuit and outputs the oscillation frequency data and phase data of the signal from the VCO ;
A delay phase amount calculation circuit that generates delay phase data by multiplying the oscillation frequency data output from the VCO in the phase-locked loop circuit by data indicating a certain signal delay time of the filter circuit ;
A phase corrector that corrects the phase data output from the VCO in the phase-locked loop circuit with the delayed phase data, and generates phase data after delay correction ;
A pre-pit gate signal generator for generating a gate signal for extracting the pre-pit signal based on said delay corrected phase data,
An optical disc recording / reproducing apparatus comprising: a prepit data discriminating circuit that discriminates the prepit signal from the reproduction signal of the optical disc by the gate signal and outputs the prepit data as prepit data.   In the filter circuit, the center frequency of the pass band is set to the frequency of the wobble signal when the relative linear velocity between the optical disc and the recording / reproducing optical beam is set to a predetermined value, and the pass band is first. And a variable band filter in which the pass band is set to a second value wider than the first value before the relative linear velocity is set to the predetermined value. The optical disk recording / reproducing apparatus according to claim 1.

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