JP2002050042A - Optical disk recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it takes time to seek an objective track since the phase relation between a gate signal for sampling a prepit and a prepit signal is deviated from the setting state until the time a spindle motor just after starting seeking is settled to a prescribed linear velocity. SOLUTION: By a BPF 9, the frequency selection is made for a wobble signal from a push-pull signal. The signal outputted from the BPF 9 is, after being made to phase data by a phase computing element 10, formed to be phase data e and frequency data f of a signal phase-synchronized with the wobble signal by a PLL consisting of a phase comparator 11, a loop filter computing element 12 and a digital VCO 13. By a prepit gate producing device 14, the phase data e are corrected with delay phase data obtained by multiplying the frequency data f by the data showing the specified signal delay times of an A/D converter 7 and the BPF 9, then, on the basis of these phase data after correction, the gate signal c for sampling the prepit signal is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus, and more particularly to a writable optical disk in which concentric or spiral tracks meander sinusoidally in the radial direction, and prepits are formed between tracks. The present invention also relates to an optical disk recording / reproducing apparatus for recording information while reproducing the pre-pits.

[0002]

2. Description of the Related Art In an optical disk recording / reproducing apparatus, an optical signal follows a center of a concentric or spiral target track on a writable optical disk to record an information signal or reproduce a recorded information signal. The track grooves of the optical disk are formed slightly meandering compared to the track pitch. The meandering track is called a wobble, the amplitude of which is set so as not to affect tracking, and the frequency is set sufficiently higher than the tracking control band. Therefore, the light beam does not follow the wobble, but traces the track center substantially.

[0003] A light beam from the optical pickup is reflected by the above-mentioned optical disk, and the reflected light is received by a photoelectric conversion element in the optical pickup and photoelectrically converted. Here, the reflected light is photoelectrically converted by a photoelectric conversion element on the inner circumference side and a 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 band-pass filter (BPF) that passes through the wobble signal.

In a conventional optical disk recording / reproducing apparatus, a wobble signal detected by this BPF is supplied to a phase locked loop (PLL) circuit, and a spindle motor for rotating the optical disk, synchronized with the wobble signal, is driven at a constant linear velocity (C).
LV) generates a spindle control signal for control, obtains a gate signal for extracting a pre-pit signal previously formed on a land between tracks, and uses this gate signal to record a track address from a pre-pit signal extracted from a reproduction signal. Is detected (Japanese Patent Laid-Open No. 9-326138).

In this conventional optical disk recording and 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 that synchronizes with a signal obtained by binarizing the BPF output signal.

[0006]

By the way, the PPF synchronizing with the binarized signal of the BPF output wobble signal is described.
In a conventional optical disk recording / reproducing apparatus that obtains a gate signal for extracting a pre-pit signal from a VCO in an LL circuit, a wobble signal passes through a BPF, whereas a pre-pit signal does not pass through the BPF. As shown in FIG. 7A, the frequency versus gain characteristic of this BPF is such that the center frequency f0 of its pass band is set equal to the wobble signal frequency, and the frequency versus phase characteristic of the BPF is shown in FIG. As shown in the figure, the characteristic is such that the input / output signal phase of the BPF changes from a leading phase to a lagging phase before and after the center frequency f0.

For this reason, at a disk linear velocity at which the wobble signal frequency becomes the center frequency f0 of the pass band of the BPF, even if the pre-pit signal is set at the center position of the gate signal for extracting the pre-pit signal, the optical pickup is set. Immediately after the radial position changes due to the track seek operation, the spindle motor for rotating the optical disc cannot follow the operation for keeping the linear velocity constant, and the wobble signal frequency becomes the center frequency f0 of the pass band of the BPF. , And the phase relationship between the pre-pit extraction gate signal generated from the signal passing through the BPF and the pre-pit signal not passing through the BPF deviates from the above-described setting state.

In this case, the phase relationship between the pre-pit extraction gate signal and the pre-pit signal that does not pass through the BPF remains deviated from the above set state until the spindle motor stabilizes to a predetermined linear velocity. Since the prepit data cannot be reproduced, the address information of the track obtained from the prepit data cannot be read, so that it takes time to seek the target track.

[0009] The present invention has been made in view of the above points,
An object of the present invention is to provide an optical disk recording / reproducing apparatus capable of reproducing prepit data even when a linear velocity changes and a wobble signal frequency deviates from a center frequency of a BPF pass band.

It is another object of the present invention to provide an optical disk recording / reproducing apparatus capable of shortening a track seek time.

[0011]

According to the present invention, in order to achieve the above object, concentric or spiral tracks are formed slightly meandering relative to the track pitch, and pre-pit signals are recorded in advance. An optical disk recording / reproducing apparatus for recording and reproducing an information signal on / from an optical disk, a filter circuit for frequency-selecting a wobble signal based on the meandering of a track from the optical disk reproduction signal, and a predetermined threshold value for the optical disk reproduction signal And a phase-locked loop that generates a signal synchronized with the phase of the wobble signal output from the filter circuit and outputs frequency data and phase data of the signal. The circuit and the frequency data output from the phase locked loop circuit add a certain signal delay of the filter circuit. A gate that corrects phase data output from the phase locked loop circuit with delayed phase data obtained by multiplying data indicating time, and generates a gate signal for extracting a prepit signal based on the corrected phase data. The signal processing means includes a signal generating means, and a pre-pit data discriminating circuit for discriminating a pre-pit signal from a reproduction signal of the optical disc by a gate signal and outputting the pre-pit data as pre-pit data.

In the present invention, the constant signal delay time of the filter circuit is calculated as the amount of phase delay at the signal frequency of the current phase locked loop circuit phase-locked to the wobble signal, and the phase locked loop is obtained using the obtained delayed phase data. Since the phase data output from the circuit is corrected and a gate signal is generated based on the corrected phase data,
The gate signal can always have a fixed phase with respect to the wobble signal at the time of input to the filter circuit irrespective of the wobble signal frequency.

The center frequency of the pass band is set to the frequency of the wobble signal when the relative linear velocity between the optical disk and the recording / reproducing light beam is set to a predetermined value. Before the relative linear velocity is settled to a predetermined value, the pass band is set to the first value.
By setting the variable band-pass filter to be a second value wider than the value of the above, it is possible to suppress a decrease in the wobble signal component in the output signal of the filter circuit before the relative linear velocity is settled to a predetermined value. desirable.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical disk recording / reproducing apparatus according to the present invention. In FIG. 1, an optical disk 1 is a write-type optical disk in which concentric or spiral tracks meander sinusoidally in the radial direction of the disk, and prepits are previously formed between the tracks. Is done.

The recording of the information signal on the optical disk 1 and the reproduction of the recorded signal on the optical disk 1 are performed by a light beam emitted from a laser light source in the pickup 3 and a reflection obtained by reflecting the light beam on the optical disk 1. It is done by light. The pickup 3 is positioned near a target track by a pickup coarse movement motor (not shown).

The objective lens in the pickup 3 is
Positioning is performed by a focus actuator (not shown) movable in the direction of the rotation axis of the optical disc 1 (a direction orthogonal to the recording / reproducing face) so that the light beam focuses on the recording / reproducing surface on the optical disc 1. The objective lens in the pickup 3 is positioned by a tracking actuator (not shown) movable in the radial direction of the disc so as to follow a concentric or spiral recording / reproducing track on the optical disc 1.

The reflected light from the optical disk 1 passes through an optical system such as an objective lens in the pickup 3 and is respectively transmitted to the inner and outer peripheral photoelectric conversion elements in the disk radial direction in the pickup 3. The light is received and photoelectrically converted. The inner-side photocurrent output from the inner-side photoelectric conversion element is input to the current-voltage conversion circuit 4, and the outer-side photocurrent output from the outer-side photoelectric conversion element is input to the current-voltage conversion circuit 5. And converted into voltage signals.

Each output voltage signal of the current-voltage conversion circuits 4 and 5 is supplied to a push-pull signal generation circuit 6 where it is subtracted to obtain a push-pull signal a which is a difference between them. This push-pull signal a is, for example, the signal shown in FIG. 2A, and is supplied to the A / D converter 7 in FIG. 1 and is converted into a digital signal, while being supplied to the pre-pit pulse detection comparator 8. A pre-pit pulse b as shown in FIG. That is, the pre-pits previously recorded on the optical disc 1 are obtained as signals having a level equal to or higher than a predetermined threshold value in the push-pull signal a.
When the threshold value is exceeded, the signal is determined to be a pre-pit reproduction signal, and is output from the pre-pit pulse detection comparator 8 as a pre-pit pulse b.

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 a wobble signal frequency as a center frequency of a pass band, and selects a frequency of a wobble signal included in input digital data.

FIG. 3 is a block diagram showing an example of the BPF 9. As shown in the figure, the BPF 9 includes nine cascade-connected delay elements 101 to 109 each delaying by a unit time (equal to the sampling cycle of the A / D converter 7), and each delay element 1
01 to 109 are input after being branched and input to the coefficient K
Multipliers 110 to 118 for multiplying by 0 to K8 and a multiplier 119 for multiplying the output signal of delay element 109 by coefficient K9.
And an adder 120 that adds each output signal of the multipliers 110 to 119 and outputs an output signal.
It is a (non-cyclic) digital filter. Also,
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).

Returning to FIG. 1, the signal in the wobble signal frequency band extracted from the BPF 9 is supplied to a phase calculator 10 where it is converted into phase data.
It is supplied to the phase comparator 11. The phase comparator 11 receives the phase data from the phase calculator 10 and a digital V
A phase comparison is performed with digital VCO phase data e from a CO (voltage controlled oscillator) 13 to generate phase error data corresponding to the phase difference between the phase data e and the loop filter calculator 12.
To supply.

The loop filter operation unit 12 is, for example, as shown in FIG.
The phase error data output from the phase comparator 10 is added to an adder 21 and a delay element 22.
And a proportional operation amount obtained by multiplying the integrated value by a coefficient KI by a multiplier 23 and a proportional operation amount obtained by multiplying the phase error data by a coefficient KP by a multiplier 24. The VCO operation amount is calculated by the addition by the adder 25.

The VCO operation amount extracted from the loop filter calculator 12 is supplied to the digital VCO 13 shown in FIG. 1 and variably controls the output oscillation frequency. The digital VCO 13 has, for example, a configuration as shown in FIG.
A frequency operation for adding the self-running frequency data set in advance to the O operation amount by the adder 31 is performed, and the obtained data is output as the current oscillation frequency data f, and includes the adder 32 and the delay element 33. Further integration is performed by an integration circuit to generate phase data.

Since this phase data repeats 2π (rad), the arithmetic unit 34 modulates the phase data with respect to the phase data.
By performing the operation of d (2π) (addition operation modulo 2π), digital VCO phase data e is generated. The digital VCO phase data e is input to the phase comparator 11 shown in FIG. 1 and is compared with the phase data from the phase calculator 10. A loop feedback loop including the phase comparator 11, the loop filter calculator 12, and the digital VCO 13 forms a phase locked loop (PL
L), and generates and outputs signals (oscillation frequency data f and phase data e) synchronized in phase with the wobble signal.

The digital VCO phase data e output from the digital VCO 13 and the oscillation frequency data f are
Each is supplied to the pre-pit gate generator 14 of FIG. The pre-pit gate generator 14 is configured, for example, as shown in FIG. Here, the input oscillation frequency data f is frequency data for each conversion cycle of the A / D converter 7, and thus data for each sample has a variation. Therefore, in order to obtain an average frequency corresponding to the number of delay samples of the BPF 9, the pre-pit gate generator 14
The moving average calculation of the input oscillation frequency data f is performed by the frequency data moving average calculator 41 of FIG. For example, when the frequency data moving average calculator 41 sets the frequency data f of the current sample to f (n), the past eight samples f (n-7),
f (n-6), f (n-5), f (n-4), f (n-3), f (n-2), f (n-1), f
The average frequency data is generated by taking the sum of (n) and multiplying the sum by 1/8.

The pre-pit gate generator 14 inputs the above average frequency data generated by the frequency data moving average calculator 41 to the delay phase calculator 42 and multiplies it by the delay time data set beforehand. Thus, delayed phase data is obtained. The preset delay time data is data indicating a constant signal delay time from the input terminal of the A / D converter 7 to the output terminal 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.

However, even if the signal delay time is constant, the amount of phase delay changes according to the frequency of the push-pull signal a. Therefore, by multiplying 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 by the delay phase amount calculator 42, the constant signal delay The time is obtained as delay phase data indicating the amount of phase delay at the oscillation frequency of the digital VCO 13.

The pre-pit gate generator 14 then performs a mod (2π) addition operation of the above-described delayed phase data and the digital VCO phase data e from the digital VCO 13 in the phase corrector 43 of FIG. The phase data after delay correction is generated and supplied to the pre-bit gate signal generator 44 so that when the phase data passes through 0, 1
, And generates and outputs a pre-pit gate signal c which becomes 0 when passing through π.

As described above, the pre-pit gate signal c as shown in FIG. 2C taken out of the pre-pit gate generator 14 together with the pre-pit pulse b shown in FIG. The data is supplied to the pre-pit data determination circuit 15. The pre-pit data discriminating circuit 15 is as shown in FIG.
As shown in the figure, when the pre-pit pulse b exists while the pre-pit gate signal c is at the H level, the data "1" is output.
When the pre-pit pulse b does not exist during the period when the pre-pit gate signal c is at the H level, the data indicates "0", thereby outputting the pre-pit data d including the track address information and other information.

As described above, according to the present embodiment, A /
The constant signal delay time from the input terminal of the D converter 7 to the output terminal of the BPF 9 is calculated by using the current V
The delay phase amount calculator 42 calculates the phase delay amount at the CO oscillation frequency, corrects the digital VCO phase data e with the obtained delay phase data, and then generates the pre-pit gate signal c. The pre-pit gate signal c is always BPF
A constant phase is set for the wobble signal at the time of 9 inputs.

For this reason, the push-pull operation is performed even during a period immediately after the seek operation and before the relative linear velocity between the light beam and the optical disk 1 has settled to a predetermined value and the wobble signal has not reached the regular frequency f0. Prepit data can be accurately read from the signal a by the prepit gate signal c. Therefore, the address information of the track obtained from the pre-pit data can be read immediately after the seek operation, so that the time required to reach the final target track can be reduced as compared with the conventional case.

The present invention is not limited to the above-described embodiment. For example, the wobble frequency may be a BPF (BPF in the above-described embodiment) for selecting the wobble frequency.
(Equivalent to PF9) is shifted from the center frequency of the pass band.
Since the wobble signal component of the output signal of the BPF is reduced, the pass band of the BPF is widened immediately after the seek to suppress the reduction of the wobble signal component of the BPF output signal, and the relative linear velocity between the optical disk and the light beam. May be set to a predetermined value, and then the pass band of the BPF may be narrowed to a predetermined value.

As a method of changing the pass band of the BPF, for example, the coefficients K0 to K of the multipliers 110 to 119 in FIG.
9 and the like. Thus, even if the pass band of the BPF is made variable, the delay time is constant,
According to the method described in the above embodiment, the pre-pit can be positioned substantially at the center of the pre-pit gate signal.

[0034]

As described above, according to the present invention,
Since 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, the relative linear velocity between the light beam and the optical disk is settled to a predetermined value immediately after the seek operation. Even before the wobble signal has not reached the regular frequency, the gate signal can be used to accurately read the pre-pit data from the reproduced signal, so that the track obtained from the pre-pit data immediately after the seek operation is performed. , The time required to reach the final target track can be reduced as compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a timing chart for explaining an operation of a main part of FIG. 1;

FIG. 3 is a block diagram showing a configuration of an example of a BPF in FIG. 1;

FIG. 4 is a configuration diagram of an example of a loop filter calculator in FIG. 1;

FIG. 5 is a configuration diagram of an example of a digital VCO in FIG. 1;

FIG. 6 is a block diagram of an example of a pre-pit gate generator in FIG. 1;

FIG. 7 is a diagram showing a frequency-gain characteristic and a frequency-phase characteristic of a BPF for frequency-selecting a wobble signal.

[Explanation of symbols]

 Reference Signs List 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) 10 phase calculator 11 phase comparator 12 loop filter calculator 13 digital VCO (voltage controlled oscillator) 14 pre Pit gate generator 15 Pre-pit data discriminating circuit 41 Frequency data moving average calculator 42 Delayed phase calculator 43 Phase corrector 44 Pre-pit gate signal generator a Push-pull signal b Pre-pit pulse c Pre-pit gate signal d Pre-pit Data e Digital VCO phase data f Oscillation frequency data

Claims (2)

[Claims] An optical disk in which concentric or spiral tracks are formed slightly meandering relative to the track pitch and record and reproduce information signals on an optical disk on which pre-pit signals are recorded in advance. In the recording / reproducing apparatus, a filter circuit for frequency-selecting a wobble signal based on the meandering of the track from the reproduction signal of the optical disc, and comparing the reproduction signal of the optical disc with a predetermined threshold value, a pre-pit pulse based on the pre-pit 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 frequency data and phase data of the signal, and an output from the phase locked loop circuit. The frequency data obtained contains data indicating a fixed signal delay time of the filter circuit. A gate that corrects the phase data output from the phase locked loop circuit with the delayed phase data obtained by multiplying the pre-pit signal based on the corrected phase data. An optical disc recording / reproducing apparatus comprising: signal generating means; and a prepit data discriminating circuit for discriminating the prepit signal from a reproduction signal of the optical disc based on the gate signal and outputting the prepit data as prepit data. 2. The filter circuit according to claim 1, wherein a center frequency of a pass band is set to a frequency of the wobble signal when a relative linear velocity between the optical disc and the recording / reproducing light beam is set to a predetermined value, and A variable bandpass filter wherein a passband is set to a first value, and the passband is set to a second value wider than the first value before the relative linear velocity is settled to the predetermined value. 2. The method according to claim 1, wherein
An optical disk recording / reproducing apparatus according to claim 1.