JP2002190167A - Signal detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a wobble signal to be extracted which is needed for the address information detection or the recorded clock generation when constant angular velocity(CAV) recording is performed to a recording medium on condition of being recorded by constant linear velocity(CLV) recording. SOLUTION: A wide band filter and a narrow-band filter are provided, the wide band filter is used while a frequency is unknown, and the narrow-band filter is used after the frequency becomes clear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording information on a rotating recording medium.

[0002]

2. Description of the Related Art As a large-capacity recording medium, a CD (Compact
CD-R (CD-Reco) to record data in Disc format
rdable) and CD-RW (CD-Rewritable) discs are used. In addition, DVD (Di-
DVD-R (DVD-Recordable) and DVD-RW (DVD-Rewritable) discs that record data in the digital versatile disc format have also begun to be used. These recording media are a read-only CD player and CD-ROM (CD-Read Only Memory).
Drive or DVD player, DVD-ROM (DVD-Rea
(d Only Memory) drive, so that the recorded disk has the same form as the read-only disk. Therefore, CLV (Co
nstant Linear Velocity) Recording is being performed. To realize CLV recording, it is necessary to change the rotation speed according to the recording diameter position, but in order to confirm that the linear velocity is correct, the recording is performed by wobbling the recording guide groove of the medium. are doing. This meandering frequency (wobble frequency) is set to be a constant frequency when the linear velocity is constant, and by detecting this frequency, rotation control to keep the linear velocity constant is realized.

FIG. 6 shows a configuration of a conventional drive device.
The reproduction signal is input to the filter circuit 20, and only the wobble frequency component is extracted. The extracted wobble signal is compared with the reference clock 21 and controls the spindle motor 3 so that the wobble frequency becomes a predetermined value. The wobble signal is input to the address demodulation circuit 11 at the same time, and the address information is detected. By controlling the spindle motor 3,
Since the wobble frequency is constant, the filter circuit 20 has a single center frequency and a narrow band pass characteristic for extracting a wobble signal.

[0004]

As described above, since the rotation speed of CLV recording needs to be changed in accordance with the recording diameter position, in random access recording performed while arbitrarily changing the recording position, the rotation settling time is set. Requires a waiting time. Such a phenomenon becomes an obstacle when connecting and using a PC (Personal Computer) that exchanges data at high speed. CAV (Constant Angular
It is known that the Velocity recording method can perform high-speed recording because the rotation number is always constant, and even if random access recording is performed, the rotation settling time does not occur. Therefore, access performance can be improved on CD-R / RW media and DVD-R / RW media by recording in the CAV format, but on the other hand, media recorded in the CAV format are also recorded in the CLV format. It is necessary to change the recording clock frequency for each recording diameter because it is necessary to make the same recording state as described above. For this purpose, it is necessary to detect a wobble frequency that changes for each recording diameter when the rotation is constant, and to generate a recording clock that changes the frequency for each diameter in synchronization with this. However, in the conventional CLV recording method, The changing wobble frequency could not be detected.

[0005]

[Means for Solving the Problems] As a first solution,
In order to detect a changing wobble frequency, a first band-pass filter having a wide pass band and a fixed center frequency is used as a filter for extracting a wobble signal from a reproduced signal, and a second band-pass filter having a narrow center and a variable center frequency is used. A band pass filter is provided.

As a second solution, a single band-pass filter having both a variable pass band width and a variable center frequency is provided to detect a changing wobble frequency.

In the first solution, at the time of start-up and when the recording position changes significantly, the wobble signal frequency is detected through the first filter and used as the reference frequency of the subsequent circuit. Second detection is performed so that this detection frequency becomes the center frequency.
And the reference frequency is switched to the second filter output when the wobble frequency can be detected more stably from the output of the second filter. Thereafter, the frequency of the output of the second filter is detected, the center frequency of the second filter is changed according to the change, and the detection is performed following the change of the wobble frequency. If the subsequent circuit cannot operate properly, it is determined that the wobble frequency and the center frequency of the second filter have shifted, and the output is switched to the first filter output. At the time of seeking, detection is performed by switching to the first filter again. If the wobble frequency at the seek target position can be assumed, the seek can be performed by setting the center frequency of the second filter to the target frequency.

In the second solution, at the time of start-up and when the recording position changes greatly, the pass band of the filter is set to a wide band, the frequency of the wobble signal is detected, and this is used as the reference frequency of the subsequent circuit. The detected wobble frequency is set to the center frequency of the filter, and the pass band is set to a narrow band. If the subsequent circuit cannot operate properly, it is determined that the center frequency of the filter has shifted from the wobble frequency, and the pass band of the filter is switched to a wide band. At the time of seek, detection is performed by switching the pass band of the filter to a wide band. If the wobble frequency at the seek target position can be assumed, the seek can be performed by setting the center frequency of the filter to the target frequency and setting the pass band to a narrow band.

[0009]

FIG. 1 shows a first embodiment of an optical disk drive according to the present invention. In the figure, 1 is an optical disk as a recording medium used in the present invention, 2 is an optical pickup for performing recording and reproduction, 3 is a spindle motor for rotating the recording medium, and 4 is a current for converting an output current of the optical pickup into a voltage. -Voltage conversion amplifier (IV amplifier),
Reference numeral 5 denotes an arithmetic circuit for generating a desired signal from the voltage-converted optical pickup output, 6 denotes a demodulation circuit for restoring a reproduced signal to data, and 7 denotes a first signal for extracting a wobble signal from the reproduced signal according to the present invention. , A second filter circuit 8, a switching circuit 9, a PLL (Phase Locked Loop) circuit 10 for generating a recording clock,
1 is an address demodulation circuit for demodulating address information (ATIP) from a wobble signal, 12 is a modulation circuit for generating a recording signal from data, 13 is a frequency detection circuit, and 14 is a control device for performing system control. Although other components are included in the optical disk drive, description and illustration thereof are omitted because they are not related to the present invention. FIG. 2 shows the first
5 shows the characteristics of the filter circuit of FIG. The pass bandwidth of this filter circuit is required from the wobble frequency when the optical pickup 2 is located at the innermost circumference to the wobble frequency when the optical pickup 2 is located at the outermost circumference when the optical disc 1 is rotated at a predetermined rotation speed. FIG. 3 shows the characteristics of the second filter circuit.
In this filter circuit, the setting range of the center frequency ranges from the wobble frequency when the optical pickup 2 is positioned at the innermost circumference to the wobble frequency when the optical pickup 2 is positioned at the outermost circumference when the optical disc 1 is rotated at a predetermined rotation speed. Necessary, but bandwidth is narrow. Since the output of the first filter circuit passes an unnecessary component wider than the wobble frequency to be extracted, the signal-to-noise ratio (S / N ratio) is not good, but has jitter. Accordingly, the recording clock generated by the PLL circuit 10 using this output as a reference signal also has jitter, and is not suitable for use in recording as it is. On the other hand, since the second filter circuit has a band through which only necessary frequency components pass, the S / N ratio of the output is improved and the jitter is reduced. In order to demodulate address information with high accuracy from the wobble frequency, a high S
An N ratio is required, and the output of the second filter circuit is input to the address demodulation circuit 11. The detection of the wobble frequency value can also be performed by the output of the filter circuit, but malfunction may be caused by the influence of noise. Therefore, it is more stable to use the recording clock generated from the filter output. Also,
In FIG. 1, the output of the frequency detection circuit is directly input to the second filter circuit to set the center frequency. However, the output of the frequency detection circuit is taken in by the control device (microcomputer) 14, and the value is obtained. Based on this, the filter circuit can be set from the control device 14. The control of the switching circuit 9 can be determined from the detection accuracy of the address information in the address demodulation circuit 11 and the stability of the generated clock in the PLL circuit 10. Switching from the filter circuit 7 to the filter circuit 8 is performed when the address information can be correctly detected. Switching from the filter circuit 8 to the filter circuit 7 is performed when address information cannot be detected or when the PLL circuit 10 is out of synchronization. These determinations and controls are performed by the control device 14.

FIG. 4 shows a second embodiment according to the present invention.
In the figure, the same components as those in FIG.
Description is omitted. The difference between this embodiment and the first embodiment lies in the filter circuit 15. The filter circuit 15 can be set by switching between a wide band state and a narrow band state with one filter circuit. Therefore, no external switching circuit is required, and the output is always output from the PLL circuit 10 and the address demodulation circuit 11.
Is input to The characteristics of the filter circuit 15 in the wide band state are the same as the characteristics in FIG. 2, and the characteristics in the narrow band state are the same as the characteristics in FIG. At startup, the filter circuit 15
Is set to a wide band state, and the wobble frequency can be detected regardless of the position of the optical pickup 2. The detected wobble signal is input to the PLL circuit 10 and the address demodulation circuit 11, where the recording clock is generated and the address information is demodulated. However, since the signal has a wide band, the SN ratio is poor, the recording clock jitter is large, and the address is large. The information also has a high error rate. Here, by setting the center frequency of the filter circuit 15 to the value of the detected wobble frequency and switching the pass band to a narrow band, the noise is reduced and the SN ratio is increased, and the recording clock with low jitter and the low error rate Address information is obtained. After switching to the narrow band, the center frequency of the filter 15 changes according to the minute fluctuation of the detected wobble frequency due to the movement of the position of the optical pickup 2, so that a stable wobble signal can always be obtained. If the reproduced wobble signal frequency deviates from the center frequency of the filter circuit 15 for some reason, the clock cannot be generated by the PLL 10 and the address information cannot be detected either. Therefore, the control device 14 can detect the address and switch the filter 15 to the broadband state. .

A third embodiment will be described with reference to FIG. Also in this figure, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.
In this embodiment, the format is such that the address information detection is not demodulated from the wobble signal but is obtained from another reproduction signal. Therefore, the output of the filter circuit 15 is supplied only to the PLL circuit 10. In this case, the switching determination between the wide band and the narrow band of the filter circuit 15 is performed by determining the stability of the PLL circuit 10.
That is, at the time of start-up, the pass band of the filter 15 is wide and the SN ratio of the extracted wobble signal is low, so that the recording clock generated by the PLL circuit 10 is also in a state of large jitter. However, if the wobble frequency is synchronized with the extracted wobble frequency, it is determined that the wobble frequency has been correctly extracted, and the center frequency of the filter circuit 15 is determined. And the pass band is set to a narrow band. Thereby, the SN ratio of the extracted wobble signal is improved, and a recording clock with small jitter is generated. The subsequent operation is the same as in the second embodiment.
When the PLL circuit 10 cannot synchronize with the output of the filter 15, it is determined that the center frequency of the filter circuit 15 and the wobble frequency have shifted, the filter circuit 15 is set to a wide band state, and the pull-in operation is performed again. . As another determination means, the determination can be made from the address detection state in the address demodulation circuit 16. In the present embodiment, since the original signal for demodulating the address information does not pass through the filter circuit 15, the signal quality does not depend on the setting state of the filter circuit. However, PL is used for address demodulation.
By using the recording clock generated by the L circuit 10, the error rate of the address information reflects the jitter amount of the recording clock. If the address information is not correctly demodulated, it is determined that the wobble signal has not been detected, and the filter circuit 15 is set to the wideband state. When address information can be obtained at a predetermined error rate, a wobble signal is extracted and it is determined that the PLL circuit 10 is synchronized with the wobble signal, and the center frequency of the filter circuit 15 is set to set a narrow band state. . As a result, the jitter of the recording clock decreases, and the error rate of the address information also decreases. If the error rate of address information increases from this state,
Since it can be assumed that the wobble frequency and the center frequency of the filter circuit 15 are starting to deviate, it is possible to correct the wobble frequency before it completely deviates.

[0012]

According to the present invention, when CAV recording is performed on a recording medium which is supposed to be recorded by CLV, detection of address information and extraction of a wobble signal necessary for generation of a recording clock are performed. And CAV recording can be realized.

[Brief description of the drawings]

FIG. 1 shows a first embodiment according to the present invention.

FIG. 2 shows pass band characteristics of a first filter circuit in the first embodiment.

FIG. 3 shows a pass band characteristic of a second filter circuit in the first embodiment.

FIG. 4 shows a second embodiment according to the present invention.

FIG. 5 shows a third embodiment according to the present invention.

FIG. 6 shows a conventional drive device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pick-up, 3 ... Spindle motor, 4 ... IV amplifier, 5 ... Operation circuit, 6 ... Demodulation circuit, 7 ... 1st filter circuit , 8 ... second filter circuit, 9 ... switching device, 10 ... PLL circuit, 11 ...
Address demodulation circuit, 12: modulation circuit, 13: frequency detection circuit, 14: control device.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D044 BC05 CC06 DE03 DE12 DE17 DE23 DE29 DE69 DE86 EF06 FG16 GM02 GM18

Claims (5)

[Claims] 1. A signal detecting apparatus for detecting a recording reference signal whose frequency changes in a time series, comprising: a first band-pass filter having a wide band for passing the entire frequency variable range;
A second band-pass filter having a band narrower than that of the band-pass filter and having a variable passing center frequency, and frequency detecting means. Is extracted, and the frequency of the extracted signal detected by the frequency detecting means is set to the center frequency of the second filter. Thereafter, frequency detection is performed by the frequency detecting means using the extracted signal of the second filter, and the detection is performed. A signal detection method for changing a center frequency of a second filter according to a result and extracting a recording reference signal. 2. A signal detecting apparatus for detecting a recording reference signal whose frequency changes in a time series, comprising: a first pass band for passing the entire frequency variable range; and a second pass band narrower than the first pass band. And a band-pass filter that has a constant second pass band width and a variable pass center frequency, and frequency detection means, and initially uses the first pass band. To extract the recording reference signal,
The extracted signal frequency detected by the frequency detecting means is used as a second
Is set to the center frequency of the pass band, and the frequency is switched to the second pass band. Thereafter, frequency detection is performed by the frequency detection means using the signal extracted by the second pass band, and the center frequency of the filter is determined based on the detection result. A signal detection method for changing and extracting a recording reference signal. 3. A recording medium on which a recording reference signal for obtaining a constant frequency when recording at a constant linear velocity is pre-recorded is rotated at a constant angular velocity, and a recording reference signal that changes according to the recording radial position is detected. A recording method for generating a recording clock that changes in accordance with the recording radius position from the changing recording reference signal, and realizing the same recording form as the constant linear velocity recording by using the changing recording clock. 4. A recording medium in which a recording reference signal for obtaining a constant frequency at the time of recording at a constant linear velocity is previously recorded is rotated at a constant angular velocity to record information in the same form as the recording at a constant linear velocity. In a recording apparatus, a first band-pass filter that passes a change range frequency of a recording reference signal whose frequency changes in accordance with a recording radius position, and a center frequency that is narrower than the first filter and variable in center frequency. A second band-pass filter, switching means for switching the output of the first and second band-pass filters, clock generating means for generating a recording clock based on a signal switched by the switching means, Address detecting means for detecting address information from the output of the second band-pass filter; detecting a clock frequency generated by the clock generating means to set a center frequency of the second band-pass filter; Frequency detecting means, a modulating means for modulating recording data into a recording signal by the recording clock, and a control means. At the initial stage, the output of the first band-pass filter is selected by the switching means and the clock generating means is selected. An information recording device for switching the switching means to the output of the second band-pass filter when a predetermined number of addresses are detected by the address detection means, generating a recording clock, and recording data. 5. A method for rotating a recording medium on which a recording reference signal capable of obtaining a constant frequency when recording at a constant linear velocity is recorded in advance at a constant angular velocity and recording in the same form as recording at a constant linear velocity. In the recording apparatus, it is possible to set a first pass band that passes a change range frequency of a recording reference signal whose frequency changes according to a recording radius position, and a second pass band that is narrower than the first pass band. A band-pass filter capable of changing the center frequency of the second pass band, clock generating means for generating a recording clock based on an output signal of the band-pass filter, and address information from the output of the band-pass filter. Address detecting means for detecting, frequency detecting means for detecting a clock frequency generated by the clock generating means and setting a center frequency of the band-pass filter, and recording by the recording clock And a control means for modulating the data into a recording signal. Initially, the output of the first band-pass filter is selected and supplied to the clock generation means. An information recording apparatus which switches the switching means to the output of the second band-pass filter at the time of completion, generates a recording clock, and records data.