JP3890888B2 - Information recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for recording information on a rotating recording medium.
[0002]
[Prior art]
CD-R (CD-Recordable) and CD-RW (CD-Rewritable) discs that record data in the CD (Compact Disc) format are used as large-capacity recording media. In addition, DVD-R (DVD-Recordable) and DVD-RW (DVD-Rewritable) discs that record data in the DVD (Digital Versatile Disc) format have begun to be used as recording media with a larger capacity. These recording media can be played back on a playback-only CD player, CD-ROM (CD-Read Only Memory) drive, or DVD player, DVD-ROM (DVD-Read Only Memory) drive. Disc is in the same form as read-only. Therefore, CLV (Constant Linear Velocity) recording is performed to keep the recording density constant. In order 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, recording is performed by wobbling the recording guide groove of the medium. is doing. This meandering frequency (wobble frequency) is set to be a constant frequency when the linear velocity is constant, and rotation control to achieve a constant linear velocity is realized by detecting this frequency.
[0003]
FIG. 6 shows the 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 the spindle motor 3 is controlled so that the wobble frequency becomes a predetermined value. The wobble signal is simultaneously input to the address demodulation circuit 11 to detect address information. Since the wobble frequency is constant under the control of the spindle motor 3, the filter circuit 20 has a narrow band pass characteristic for extracting a single center frequency and a wobble signal.
[0004]
[Problems to be solved by the invention]
As described above, CLV recording requires the rotational speed to be changed according to the recording diameter position. Therefore, in random access recording performed while arbitrarily changing the recording position, a rotational settling time is required, so a waiting time is generated. To do. Such a phenomenon becomes an obstacle when connected to a PC (Personal Computer) that exchanges data at high speed. On the other hand, the CAV (Constant Angular Velocity) recording method is known to be capable of high-speed recording because the rotational speed is always constant and no rotation settling time is generated even if random access recording is performed. Therefore, CD-R / RW media and DVD-R / RW media can improve access performance by recording in the CAV format. On the other hand, media recorded in CAV are also recorded in CAV. Therefore, it is necessary to change the recording clock frequency for each recording diameter. For that purpose, it is necessary to detect the 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 synchronized with this, but in the conventional CLV recording method, The changing wobble frequency could not be detected.
[0005]
[Means for Solving the Problems]
As a first solution, as a filter for extracting a wobble signal from a reproduction signal in order to detect a changing wobble frequency, a first band pass filter having a wide pass band and a fixed center frequency, and a center having a narrow pass band. A second bandpass filter having a variable frequency is provided.
[0006]
As a second solution, in order to detect a changing wobble frequency, a single bandpass filter having both variable passband width and center frequency is provided.
[0007]
In the first solution, the wobble signal frequency is detected through the first filter at the time of start-up and when the recording position changes greatly, and is used as the reference frequency of the subsequent circuit. The second filter is set so that the detected 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 than the second filter output. Thereafter, the frequency of the second filter output is detected, the center frequency of the second filter is changed according to the fluctuation, and the detection is performed following the change of the wobble frequency. When the subsequent circuit cannot operate correctly, it is determined that the wobble frequency and the center frequency of the second filter are shifted, and the output is switched to the first filter output. At the time of seek, the detection is switched to the first filter again. When the wobble frequency at the seek target position can be assumed, the center frequency of the second filter can be set as the target frequency for seeking.
[0008]
In the second solution, when the start position and the recording position change greatly, the passband of the filter is set to a wide band to detect the wobble signal frequency and set it as the reference frequency of the subsequent circuit. The detected wobble frequency is set to the center frequency of the filter, and the passband is set to a narrow band. If the subsequent circuit cannot operate correctly, it is determined that the center frequency of the filter is shifted from the wobble frequency, and the pass band of the filter is switched to a wide band. During seek, detection is performed by switching the pass band of the filter to a wide band. When the wobble frequency at the seek target position can be assumed, seeking can be performed by setting the center frequency of the filter as the target frequency and the pass band as a narrow band.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a first embodiment of an optical disk drive device according to the present invention. In the figure, 1 is an optical disk which is a recording medium used in the present invention, 2 is an optical pickup for recording and reproducing, 3 is a spindle motor for rotating the recording medium, and 4 is a current for converting the output current of the optical pickup into a voltage. A voltage conversion amplifier (IV amplifier), 5 an arithmetic circuit for generating a desired signal from the voltage-converted optical pickup output, 6 a demodulation circuit for restoring the reproduction signal to data, and 7 from the reproduction signal according to the present invention A first filter circuit for extracting a wobble signal, 8 is also a second filter circuit, 9 is a switching circuit, 10 is a PLL (Phase Locked Loop) circuit for generating a recording clock, and 11 is address information from the wobble signal. (ATIP) demodulating an address demodulating circuit, 12 a modulating circuit for generating a recording signal from data, 13 a frequency detecting circuit, and 14 a system controlling system. It is a device. Although there are other components as the optical disk drive device, the description and illustration are omitted because they are not related to the present invention. FIG. 2 shows the characteristics of the first filter circuit. The pass band width 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 it is located at the outermost circumference when the optical disk 1 is rotated at a predetermined rotational speed. The characteristics of the second filter circuit are shown in FIG. In this filter circuit, the setting range of the center frequency is from the wobble frequency when the optical pickup 2 is located at the innermost periphery to the wobble frequency when it is located at the outermost periphery when the optical disc 1 is rotated at a predetermined rotational speed. Although necessary, bandwidth is narrowing. Since the output of the first filter circuit passes unnecessary components wider than the wobble frequency to be extracted, it cannot be said that the signal-to-noise ratio (SN ratio) is good and has jitter. Therefore, 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 that allows only necessary frequency components to pass therethrough, the SN ratio of the output is improved and the jitter is also reduced. In order to demodulate the address information from the wobble frequency with high accuracy, a high S / N ratio is required, and the output of the second filter circuit is input to the address demodulation circuit 11. Although the wobble frequency value can be detected by the output of the filter circuit, it may be malfunctioning due to the influence of noise. Therefore, it is more stable to use a recording clock generated from the filter output. 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 captured by a control device (microcomputer) 14 and the center frequency is set. Based on the value, 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 the address information cannot be detected or when the PLL circuit 10 is out of synchronization. These determinations / controls are performed by the control device 14.
[0010]
A second embodiment according to the present invention is shown in FIG. In the figure, the same components as those in FIG. The difference between the present embodiment and the first embodiment resides 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 a single filter circuit. This eliminates the need for an external switching circuit, and the output is always input to the PLL circuit 10 and the address demodulation circuit 11. The characteristics of the filter circuit 15 in the wide band state are the same as those in FIG. 2, and the characteristics in the narrow band state are the same as those in FIG. At startup, the filter circuit 15 is set in a broadband 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 to generate the recording clock and demodulate the address information. However, since it is a wide band, the SN ratio is bad and the recording clock jitter is large. 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 are reduced. Address information is obtained. After switching to the narrow band, since 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, a stable wobble signal can always be obtained. If the reproduction wobble signal frequency deviates from the center frequency of the filter circuit 15 for some reason, the PLL 10 cannot generate the clock and the address information cannot be detected, so that it can be detected by the control device 14 and the filter 15 is switched to the broadband state. .
[0011]
A third embodiment will be described with reference to FIG. Also in this figure, the same parts as those in the first embodiment and the second embodiment are denoted by the same reference numerals and description thereof is omitted. In this embodiment, the address information detection is not demodulated from the wobble signal but in a format 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, since the pass band of the filter 15 is wide at the time of activation, 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 where there is a lot of jitter. However, if the wobble frequency is synchronized with the extracted wobble frequency even if there is a little jitter, it is determined that the wobble frequency is correctly extracted, and the center frequency of the filter circuit 15 is determined as the recording clock frequency generated by the PLL circuit 10. And set the passband to a narrow band. As a result, the SN ratio of the extracted wobble signal is improved and a recording clock with small jitter is generated. Subsequent operations are the same as those in the second embodiment. When the PLL circuit 10 becomes unable to synchronize with the output of the filter 15, it is determined that the center frequency of the filter circuit 15 is shifted from the wobble frequency. Set 15 to the broadband state and perform the pull-in operation again. As another determination means, determination can be made from the address detection state in the address demodulation circuit 16. In this embodiment, since the original signal 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, by using the recording clock generated by the PLL circuit 10 for address demodulation, the jitter amount of the recording clock is reflected in the error rate of the address information. If the address information is not demodulated correctly, it is determined that the wobble signal is not detected, and the filter circuit 15 is set to the wideband state. When the address information can be obtained with a predetermined error rate, it is determined that the wobble signal is extracted and the PLL circuit 10 is synchronized with this, and the center frequency of the filter circuit 15 is set to set the narrow band state. . As a result, the jitter of the recording clock is lowered, and the error rate of the address information is also lowered. If the error rate of the address information increases from this state, it can be assumed that the wobble frequency and the center frequency of the filter circuit 15 are starting to deviate, so that correction can be made before they completely deviate.
[0012]
【The invention's effect】
According to the present invention, when CAV recording is performed on a recording medium premised on recording by CLV, it is possible to extract wobble signals necessary for detecting address information and generating a recording clock. Recording can be realized.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of the present invention. FIG. 2 shows a pass band characteristic 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 apparatus.
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 demodulator circuit, 12. ··Control device.

Claims (2)

In an information recording apparatus for recording in the same form as recording with a constant linear velocity by rotating a recording medium on which a recording reference signal for obtaining a constant frequency when recording at a constant linear velocity is recorded in advance at a constant angular velocity,
A first band-pass filter for passing a change range frequency of a recording reference signal whose frequency changes according to a recording radius position;
A second band-pass filter having a constant bandwidth for passing a signal and narrower than the first band-pass filter, and a variable center frequency of the band;
Switching means for switching the outputs of the first and second bandpass filters;
Clock generation means for generating a recording clock based on the signal switched by the switching means;
Address detecting means for detecting address information from the output of the second bandpass filter;
Frequency detecting means for detecting a generated clock frequency of the clock generating means and setting a center frequency of the second bandpass filter;
Modulation means for modulating recording data into a recording signal by the recording clock;
Control means,
At the initial stage, the output of the first band-pass filter is selected by the switching means and supplied to the clock generation means. When a predetermined number of addresses in the address detection means are detected, the switching means is connected to the second band-pass filter. An information recording device that switches to output, generates a recording clock, and records data. In an information recording apparatus for recording in the same form as recording with a constant linear velocity by rotating a recording medium on which a recording reference signal for obtaining a constant frequency when recording at a constant linear velocity is recorded in advance at a constant angular velocity,
A first pass band for passing a change range frequency of a recording reference signal whose frequency changes according to a recording radius position;
A bandpass filter capable of setting a second passband having a constant passband width and narrower than the first passband, and capable of varying a center frequency of the second passband;
Clock generating means for generating a recording clock based on the output signal of the bandpass filter;
Address detection means for detecting address information from the bandpass filter output;
Frequency detecting means for detecting a generated clock frequency of the clock generating means and setting a center frequency of the band-pass filter;
Modulation means for modulating recording data into a recording signal by the recording clock;
Control means,
At the initial stage, the output of the first band-pass filter is selected and supplied to the clock generation means, and the switching means is switched to the output of the second band-pass filter when a predetermined number of addresses in the address detection means are detected. An information recording device that generates a recording clock and records data.

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