JP2006338716A - Pll circuit and optical disk drive using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive which can reproduce the recorded high density data from the beginning without errors even when the channel frequencies are changed by seeking or when there are non-recorded areas right in front. <P>SOLUTION: This drive continuously detects the frequency (Fwbl) of the 2nd signals by using an FM demodulator (6 in Fig.1), and uses the sum of the output (ΔF) of a loop filter (52 in Fig.1) and (Fwbl) as the control input signals of the local oscillator (53 in Fig.1) in the PLL circuit (5 in Fig.1) inputting the 1st signals. The phase is pulled in within a short period by controlling the center frequency of the local oscillator (53 in Fig.1) by using the 2nd signals that the frequency information can always be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention reproduces from a head recording area without error even when a channel frequency is switched or an unrecorded area exists immediately before a PLL (Phase-Locked Loop) circuit used for an optical disk or the like. The present invention relates to a PLL circuit having high-speed pull-in and stability.

  In recent years, due to advances in semiconductor process technology, advances in Internet technology, and expansion of data communication capacity, the number of scenes where individuals handle huge amounts of data has increased. Accordingly, data storage devices such as optical disk devices and hard disk devices have become widespread. An optical disk device has an advantage of a replaceable medium as compared with a hard disk device, but has more restrictions on recording and reproduction. Hereinafter, a recording / reproducing method of the optical disc apparatus will be described.

  In general, an optical disc apparatus includes a pickup having a servo mechanism that can accurately follow a rotating and spotting laser spot in a radial direction and a vertical direction with respect to a rotating disc medium, and guide grooves (grooves) on the disc. Track). Control in the vertical direction is called focusing servo, and control in the radial direction is called tracking servo.

  By increasing the light intensity of the laser beam at the time of recording, the temperature of the minute spot area condensed on the medium surface is raised, thereby causing a physical change (phase change, magnetic domain inversion, etc.) to form a minute mark. During reproduction, a beam having a light intensity that does not cause a physical change is irradiated, and a change in the amount of reflected light is detected by a photodetector. This detection signal is referred to as a reproduction RF (Radio Frequency) signal.

  In order to detect information from the reproduction RF signal, a PLL circuit is necessary for extracting a synchronous clock. FIG. 4 shows an open loop characteristic of a general PLL. Normally, in a PLL circuit that generates phase synchronization information only from a reproduced RF signal, the disk eccentricity is compressed, so that the loop characteristic is set so that the gain is greater than or equal to A1 with respect to the eccentric frequency fa. By moving the loop band to the high frequency side, the compression ratio against eccentricity increases. If it does so, since the noise band which passes PLL will increase conversely, the precision of a synchronous clock will deteriorate in the form of a clock jitter. Although the effect on noise is improved by reducing the PLL gain, the compression gain with respect to the eccentric frequency becomes A2, so that a phase shift occurs when a disk with a large eccentricity is reproduced, and the reproduction performance. Will deteriorate. FIG. 5 shows a phase error on a time axis in a general PLL. As is clear from this figure, the fluctuation due to eccentricity can be compressed at high gain, but the compression effect is reduced at low gain.

  On the other hand, when information is recorded, it is necessary to specify a geometric position (physical address) on the disk and to record an information mark having an accurate length at that position. This is mainly due to reasons such as ensuring continuity of recorded information, improving accessibility, and avoiding overwriting of recorded areas. There are two methods of embedding physical address information: a method of forming a pre-pit on an information track, and a method of modulating a groove track and embedding information therein.

  In magneto-optical disks and DVD-RAMs, a VFO area consisting of a single frequency and a pre-pit in which physical address information following the PLL are embedded in advance on the information track, and the position is obtained by reproducing this information. Identify. This pre-pit area is called a pre-pit header and is formed at the head of each sector. User information cannot be recorded in this area.

  In CD-R / RW, DVD-R / RW, and DVD + R / RW, it is necessary to reproduce the recorded disc with a ROM drive, and thus it is not possible to use prepits formed on information tracks. Therefore, a wobble track type disk wobbled in the radial direction when cutting the groove track is used. Address information is embedded in CD by wobbling frequency modulation and in DVD + R / RW by phase modulation. In DVD-R / RW, a pre-called land pre-pit in which address information is embedded is distributed and arranged on an area (land area) between a group track and an adjacent groove track in synchronization with the wobbling phase.

  The wobbling frequency needs to be higher than the tracking servo tracking band and low frequency that does not affect the reproduction RF signal. For CD, it is 1/192 of the RF channel, and for DVD-R / RW / RAM, it is RF. 1/186 of the channel frequency and 1/32 of the DVD + R / RW are selected. Wobbling can be detected from the difference in the photodetector output obtained by dividing the reflected light from the disk into two in the radial direction. This detection signal is hereinafter referred to as a “wobble signal”. The wobble signal has a low signal-to-noise ratio (SNR), but has a relatively narrow bandwidth and always obtains phase information. Therefore, a stable channel clock can be generated by the PLL. Therefore, by identifying the physical position by detecting the modulated wobble signal or reproducing the land pre-pit and recording information in synchronization with this wobble PLL clock, the correct length of information is recorded in an arbitrary area on the disc. It becomes possible to do. Therefore, the ratio between the channel frequency of the reproduction RF signal and the fundamental frequency of the wobble signal is constant even when the disk rotation speed changes.

  There are mainly two types of disk rotation control methods. The simplest is a CLV (Constant Linear Velocity) control method for controlling the spindle rotation speed so that the frequency of the wobble signal is constant. However, in the case of CLV control, the spindle rotation speed changes by about 2.4 times on the inner and outer circumferences, so that there is a spindle control waiting time during random access, and a lot of power is consumed by this. It is a problem. For this reason, an apparatus using a CAV (Constant Angular Velocity) control method is increasing. In this method, since the spindle is always rotated at a constant speed, the waiting time for rotation is ‘0’. On the other hand, since the linear velocity changes depending on the radius, it is necessary to control the recording power with respect to the radius. Further, a wobble PLL having a wide capture range and a reproduction RF signal PLL are required.

  By the way, the DVD-RAM employs a prepit header following the random accessibility of the magneto-optical disk, and there is a recording area following the unrecorded area. That is, after the reproduction PLL is removed from the unrecorded area, the PLL pull-in is completed immediately from the beginning of the recording area, and data reproduction is requested. In the unrecorded area, the output of the phase comparator in the reproduction PLL can be expected to be “0” on average, but the local oscillator frequency may be shifted in some cases. It is necessary to complete the phase pull-in in the VFO area at the beginning of the recording area. However, if the frequency greatly shifts in the unrecorded area, the phase pull-in may not be completed. This may cause a data detection error at the beginning of the recording area. In other optical disk media, processing is performed so that there is no unrecorded area in the middle of the area, so such a problem does not occur.

  One method for solving the above problem is disclosed in Patent Document 1. This is mainly for assisting the synchronization of the DVD-RAM. In this method, a selection switch is provided in the reproduction PLL input stage for generating a synchronization clock of the reproduction RF signal, and either the reproduction RF signal or the wobble synchronization clock is provided. The wobble synchronization clock is selected when the RF signal is not detected. As a result, even when the reproduction RF signal is not detected, it is possible to maintain the oscillation frequency of the reproduction RF synchronization clock so as not to deviate greatly.

  However, there is a problem that a delay occurs in order to prevent erroneous determination of the presence / absence of a reproduction RF signal due to a defect, and the VFO is equivalently shortened due to this delay. A technique for avoiding this problem is disclosed in Patent Document 2. FIG. 6 shows a configuration diagram thereof.

  The channel clock reproduction system 100 includes an optical pickup 12 that reads a recording signal recorded on an optical disc 11, an RF amplifier 14, a band pass filter 17, a wobble PLL block 16, and a data PLL block 15. The wobble PLL block 16 includes a phase comparator 161, a loop filter 162, a voltage controlled oscillator 163, and a 1/186 frequency divider 163. The data PLL block 15 includes phase comparators 155 and 156, a signal adder 154, a loop filter 152, and a voltage controlled oscillator 153.

  A recording signal recorded on the optical disk 11 is read out via the optical pickup 12. Description of disk rotation control and optical pickup servo is omitted. The output signal of the optical pickup 12 is input to the RF amplifier 14. The RF amplifier 14 outputs a reproduction RF signal and a wobble signal by a predetermined process.

  The reproduced RF signal is input to the phase comparator 155. On the other hand, the wobble signal is input to the wobble PLL block 16 after the band region filter 17 removes the header region signal and the low frequency fluctuation component. The phase comparator 161 of the wobble PLL block 16 compares the phases of the wobble signal and the 186 frequency-divided signal by the frequency divider 1164 of the wobble multiplied clock signal, which is the output signal of the voltage controlled oscillator 163, and outputs a phase error signal. . The phase comparator 161 is a phase error signal having such a polarity that the frequency of the output signal of the voltage controlled oscillator 163 becomes higher when the phase of the wobble signal is advanced with respect to the phase of the 186 frequency-divided signal of the wobble multiplied clock signal. Is output. The phase error signal is input to the loop filter 162. The output signal of the loop filter 8 is input to the voltage controlled oscillator 163 as a VCO control voltage. The voltage controlled oscillator 163 outputs a wobble multiplied clock signal having a frequency corresponding to the input VCO control voltage. This wobble multiplication clock signal has a frequency 186 times the wobble frequency in a steady state, which is a frequency corresponding to the reproduction rate of the reproduction signal including the header data. The wobble multiplied clock signal generated by the wobble PLL block 16 is input to the phase comparators 155 and 156.

  The phase comparator 155 compares the phases of the RF signal and the wobble multiplied clock signal and outputs a phase error signal. The phase comparator 155 outputs a phase error signal having such a polarity that the frequency of the output signal of the voltage controlled oscillator 153 is increased when the phase of the RF signal is advanced with respect to the phase of the wobble multiplied clock signal. On the other hand, the phase comparator 156 compares the phases of the wobble multiplied clock signal and the channel clock signal and outputs a phase error signal. The phase comparator 156 outputs a phase error signal having such a polarity that the frequency of the output signal of the voltage controlled oscillator 153 is high when the phase of the wobble multiplication clock signal is advanced with respect to the phase of the channel clock signal. .

  The phase error signal that is the output of the phase comparator 155 and the phase error signal that is the output of the phase comparator 156 are added by a signal adder 154 at a predetermined ratio. The output signal of the signal adder 154 is input to the loop filter 152. The output signal of the loop filter 152 is input to the voltage controlled oscillator 153 as a VCO control voltage. The voltage controlled oscillator 153 outputs a clock signal having a frequency corresponding to the input VCO control voltage. This clock signal is output as a channel clock signal.

  In this technique, instead of the selection switch, a method of adding the output of the phase comparator 155 between the reproduction RF signal and the wobble synchronization clock and the output of the phase comparator 156 of the wobble synchronization clock and the VCO 153 is used.

When the phase of the RF signal is φr, the phase of the wobble synchronization clock is φw, and the phase of the RF synchronization clock is φp, the phase error φ after addition is
φ = K1 (φr−φw) + K2 (φw−φp)
Furthermore, when K1 = K2 is corrected, φ becomes irrelevant to φw,
φ = K1 (φr-φp)
It becomes. Since φ is controlled by the PLL so that φ = 0, φp coincides with φr. In addition, the change-over switch is not necessary, and there is no problem due to a mistake in determining whether or not there is an RF signal.

JP 2002-298367 A JP 2001-52450 A

  By the way, the wobble signal after information recording is subjected to interference of the reproduction RF signal, and the SNR thereof is greatly reduced. Therefore, even if a reproduction channel clock is generated from such a wobble signal, it is difficult to match the phase, and an error of about several channel clocks is included with respect to the channel clock. This maximum deviation amount is taken as an N-channel clock. In this case, even when the RF synchronization clock is correctly synchronized with the RF signal, the output of the phase comparator 155 must output a phase error of 2Nπ. A normal reproduction RF signal includes many frequency components and often has a low SNR. Even if a phase frequency comparator is used, it is difficult to stably and accurately generate phase error information of 2π or more from such a signal. Therefore, the technique disclosed in Patent Document 2 is effective only when the phase difference between the wobble signal and the RF signal is sufficiently small, and is difficult to apply in an actual optical disc apparatus.

  Further, HD DVD-RW (High Definition DVD-Rewritable), which is the next generation optical disc standard, is premised on PRML (Partial Response Maximum Likelihood) detection with lower resolution of the reproduction RF signal than DVD. Therefore, the SNR of the phase error information obtained from the reproduced signal is further reduced. HD DVD-RW has only a wobble signal phase-modulated as in DVD + R / RW and does not have a prepit header, but requires random access similar to DVD-RAM. That is, it is necessary to correctly reproduce the recording part that follows the unrecorded part from the beginning. In DVD-RAM, in addition to the VFO area at the head of the recording part, there is a VFO area in the prepit header immediately before the recording part VFO, but in HD DVD-RW, there is only a 71B VFO area at the head of the recording part. is there. For this reason, when the frequency is greatly shifted, there is a possibility that even the frequency pull-in cannot be performed. In addition, since phase error information has a low SNR, PLL phase synchronization in a short time becomes a big problem as compared with a DVD-RAM having prepits. In the CAV operation, since the channel frequency varies from 100% to 240% on the inner and outer circumferences, it becomes more difficult to reproduce the first block.

  Therefore, the problem to be solved by the present invention is that a data recording area recorded at high density can be reproduced without error from the beginning even when the channel frequency is switched by seeking or when there is an unrecorded area immediately before. It is to realize a PLL having both high speed pull-in and stability. Therefore, an object of the present invention is to provide a high-throughput and highly reliable device that ensures high-speed synchronization and stability of a data reproduction PLL even when the channel frequency is switched or an unrecorded area is present immediately before. is there.

  A PLL circuit according to the present invention receives an RF signal read from an optical disk medium, generates a clock signal whose phase is synchronized with the RF signal, and is read from the optical disk medium simultaneously with the RF signal. And an FM demodulator for inputting a wobble signal and outputting a frequency signal corresponding to the frequency of the wobble signal. The PLL sets a frequency that is the center of the clock signal based on the frequency signal output from the FM demodulator.

  While the technique of Patent Document 2 uses the phase of the wobble signal, the present invention uses the frequency of the wobble signal. As described above, the wobble signal phase includes many errors. In comparison, the frequency ratio between the wobble signal and the RF signal is very accurate. Therefore, even when the RF signal is interrupted or when the linear velocity of the RF signal changes, the phase synchronization can be completed immediately after the RF signal is input by accurately following the frequency of the RF signal by the wobble signal. it can.

  For example, the frequency signal is a voltage value corresponding to the frequency of the wobble signal, and the PLL includes a voltage controlled oscillator that changes the frequency of the clock signal according to a control voltage, and the control voltage is the frequency signal. And the voltage value corresponding to the phase difference between the RF signal and the clock signal. At this time, the voltage controlled oscillator operates so as to output a clock signal that matches the frequency corresponding to the frequency of the wobble signal and that matches the phase of the RF signal.

  In other words, the optical disc apparatus according to the present invention continuously detects the frequency of the wobble signal by the FM demodulator (6 in FIG. 1). As a control input of the local oscillator (53 in FIG. 1) in the PLL circuit (5 in FIG. 1) that receives the reproduction RF signal, the loop filter (52 in FIG. 1) output (ΔF) and FM corresponding to the wobble signal frequency The sum of the demodulator output (Fwbl) is used. As a result, the PLL circuit (5 in FIG. 1) operates to cancel the error between the wobble frequency equivalent signal (Fwbl) and the channel frequency of the reproduction RF signal. In synchronization with this PLL clock, the reproduction data is detected from the reproduction RF signal.

  Even if the linear velocity changes, the frequency ratio of the wobble signal and the reproduction RF signal is constant and does not change. In some cases, a reproduced RF signal cannot be obtained, but phase information can always be detected from a wobble signal. Therefore, when the wobble signal is used, the frequency of the reproduction RF signal can be detected with high accuracy and a wide frequency range even when the reproduction RF signal cannot be obtained. By adding an FM demodulator output signal corresponding to the wobble signal frequency as a frequency offset to the local oscillator frequency of the reproduction RF PLL, it is possible to substantially match the channel frequency. However, since the detection signal corresponding to the frequency includes an error of about several channel clocks, the reproduction RF signal is used to correct this. Therefore, the timing can be generated at high speed and stably compared to the case where the phase synchronization signal is generated only from the reproduction RF signal. Therefore, the phase synchronization establishment of the recording unit after the seek or following the unrecorded unit can be realized in a short time.

  Moreover, this invention can also be comprised like following (1)-(9).

  (1). In a PLL circuit that generates a synchronization timing from a first signal, a second signal is obtained that is frequency ratio constant and substantially continuous with the channel frequency of the first signal, and the second signal is A PLL circuit having an FM demodulator as an input and setting an operation center frequency of the PLL by an output of the FM demodulator.

  (2). The PLL circuit according to (1), wherein a limiter is provided at a local oscillator control input in the PLL, and the upper and lower limits of the synchronization timing frequency are limited based on the output of the FM demodulator.

  (3). The PLL circuit according to (1) or (2), wherein the FM demodulator is configured by a second PLL.

  (4). Concentric or spiral tracks are formed on a disk-shaped recording medium, the tracks meander in a minute sine wave having a substantially constant period in the track lateral direction, and recorded information is recorded on the tracks. In the optical disk medium formed in synchronization with the optical disk medium, a pickup means for reading the recorded information from the rotating optical disk medium, a servo mechanism for controlling the reading position of the pickup means, and a record mark / space sequence obtained from the pickup Means for detecting recording information from an RF signal that is a reflected light detection signal of the above, an FM demodulator that receives a wobble signal that is a change detection signal due to the track meandering obtained from the pickup, and a synchronization timing from the RF signal. A PLL circuit that generates the PLL circuit, It sets the operating center frequency of the PLL by M demodulator output, the optical disk apparatus characterized by operating the record information detecting means by the synchronous timing of the PLL.

  (5). The optical disk apparatus according to (4), wherein a limiter is provided at a local oscillator control input in the PLL, and upper and lower limits of the synchronization timing frequency are limited based on the output of the FM demodulator.

  (6). The optical disk apparatus according to (4) or (5), wherein the FM demodulator is configured by a second PLL.

  (7). For the RF signal in which a fixed-length playback block is continuous and a single frequency signal is inserted at a specific position of the playback block, and the wobble signal in which address information for identifying the playback block is embedded, Means for detecting the address information from the wobble signal; means for estimating the single frequency domain included in the RF signal from the address information; and the PLL gain only for a period detected by the single frequency domain estimation means. The optical disc apparatus according to any one of (4) to (6), further comprising means for raising

  (8). In an optical disk medium in which prepits are arranged at equal intervals on the track with respect to concentric or spiral tracks on the disk-shaped recording medium, and recording information is formed in a region other than the prepits on the track with a constant linear density A pickup means for reading the recording information from the rotating optical disc medium, a servo mechanism for controlling the reading position of the pickup means, and an RF signal which is a reflected light detection signal of a recording mark / space column obtained from the pickup A means for detecting recording information, an FM demodulator that receives a pre-pit reproduction signal obtained from the pickup, and a PLL circuit that generates a synchronization timing from the RF signal, the PLL circuit depending on the output of the FM demodulator The operation center frequency of the PLL is set, and the P Optical disc apparatus characterized by operating the record information detecting means by the synchronous timing of the L.

  (9). The optical disk apparatus according to (8), wherein a limiter is provided at a local oscillator control input in the PLL, and upper and lower limits of the synchronization timing frequency are limited based on the output of the FM demodulator.

  According to the present invention, it is possible to improve the throughput during reproduction (first effect). The reason is that even if the reproduction RF signal is interrupted or the linear velocity is changed, the frequency can be tracked by the wobble signal, so that the phase synchronization can be completed as soon as the reproduction RF signal is input. . In addition, according to the present invention, it is possible to improve the reproduction performance (second effect). The reason is that the frequency gain due to eccentricity included in the reproduction RF signal can be compressed using the wobble signal, so that the loop gain of the reproduction PLL can be lowered.

  Next, the best first embodiment for carrying out the present invention will be described with reference to FIG. As in the case of CD-R / RW, DVD-R / RW / RAM, etc., it is assumed that the optical disk apparatus 10 records and reproduces information on a disk medium 1 in which groove tracks are formed spirally or concentrically. The groove track is formed by wobbling at a constant amplitude in the radial direction and with a period that is an integral multiple of the recording pit. The wobbling phase or frequency may be modulated by the physical address information. The rotation of the disk medium 1 is controlled by a spindle motor (not shown).

  A pickup beam 2 made up of a drive system such as a laser diode, an optical element, and an objective lens causes the focused beam spot to follow the groove track of the disk medium 1. The pickup 2 detects the vertical and radial misalignment with the disk medium 1 by the reflected light from the disk medium 1, and the actuator servo 3 controls the drive actuator of the objective lens, so that the disk surface shake and the disk eccentricity are controlled. Follow exactly.

  Reflected light from the disk medium 1 is received by a photodetector in the pickup 2, and a weak received light signal is amplified by an RF amplifier 4. The wobble signal, which is a difference signal of the detector output divided into two in the radial direction, can output the variation in the radial direction of the groove track as amplitude information. The user information is recorded as a minute mark row in the track. At this time, recording is performed in synchronization with a recording clock obtained by multiplying the wobble signal by N. N is an integer from 32 to 192, and is uniquely determined by the type of recording medium. The reproduced RF signal including user information can be extracted as the sum of the divided detector outputs, and the frequency ratio between the channel clock of the reproduced RF signal and the wobble signal is constant.

  Since the band of the wobble signal is relatively narrow, SNR can be earned by limiting the band with a BPF (Band Pass Filter) 7. A PLL is used as the FM demodulator 6 that continuously detects the frequency of the wobble signal from the output of the BPF 7. Hereinafter, in order to distinguish from the PLL 5 for the reproduction RF signal, the RF-PLL 5 and the wobble PLL 6 will be referred to. That is, the phase difference between the output signal of the BPF 7 and the output signal of the frequency divider 64 is detected by the phase comparator 61, and the oscillation frequency of the local oscillator 63 is controlled through the loop filter 62. The output signal of the local oscillator 63 is fed back to the phase comparator 61 through the frequency divider 64. Thereby, the frequency control is performed so that the output signal of the phase comparator 61 approaches “0”.

  If there is a function of multiplying the output signal of the local oscillator 63 separately, the frequency divider 64 is not necessarily required (that is, N = 1). Further, a comparator may be added between the BPF 7 and the phase comparator 61. If the SNR of the wobble signal is sufficiently high, the BPF 7 need not be passed. If the wobble PLL 6 is locked, the wobble signal frequency and the control input (Fwbl) of the local oscillator 63 correspond one to one. That is, the wobble PLL 6 operates as an FM demodulator for wobble signals. A wobble signal may be captured by an A / D converter, and a loop may be configured by a digital circuit. For example, the FM demodulator may be configured to measure the wave number of a wobble signal. Further, the input signal of the FM demodulator may not be a wobble signal but a signal such as a DVD-RAM pre-pit header. In this case, the pre-pit header interval may be measured, or the pre-pit header The VFO frequency may be detected. When pre-pit information is used, a guide groove without wobbling may be used.

  A phase comparator 51 generates a phase difference between the reproduction RF signal and the output signal of the local oscillator 53. The output signal of the phase comparator 51 is filtered through the loop filter 52 and output as ΔF. After adding this output signal ΔF and the output signal Fwbl of the wobble PLL 6 as the frequency detector, the local oscillator 53 is controlled. As a result, the local oscillator 53 is synchronized in phase with the reproduction RF signal while oscillating at the center frequency Fwbl.

  When the local oscillator 53 and the local oscillator 63 have different sensitivities, the center frequency Fwbl may be multiplied by a constant for correction. A comparator may be added between the reproduction RF signal and the phase comparator 51. An upper and lower limiter may be provided for ΔF so that the frequency does not deviate significantly when a reproduction RF signal cannot be obtained. The reproduction RF signal may be captured by an A / D converter, and the PLL may be configured by a digital circuit.

  At each extracted synchronization timing, the reproduction RF signal is binarized by the pulsing means 8 to detect reproduction data. Thereafter, ECC (Error Correction Code) correction or the like is performed by a demodulation circuit (not shown) or the like to extract information. The pulsing means 8 may be replaced with a PRML detector.

  If the disk format is such that the phase synchronization VFO area is added in front of the user information like HD DVD-RW and the physical address information can be read from the wobble signal, a detector for detecting the address information from the wobble signal is provided, Thus, a means for estimating the VFO region on the reproduction RF signal and increasing the loop gain of the RF-PLL 5 only during this VFO period may be provided. In this case, the phase pull-in time can be further shortened.

  FIG. 2 is a block diagram showing a second embodiment of the optical disc apparatus according to the present invention. The RF-PLL 5 that generates the synchronization timing from the first signal detects a phase shift between the output signal of the local oscillator 53 and the first signal by the phase comparator 51, and after filtering by the loop filter 52, Control the frequency. Here, it is assumed that a second signal having a constant channel frequency and frequency ratio of the first signal is given. This second signal is input to the FM demodulator 6 to generate information (Fwbl) corresponding to the frequency of the second signal. The output (ΔF) of the loop filter 52 and Fwbl are added by the adder 54. The center frequency of the local oscillator 53 is determined by Fwbl, and the error is absorbed by ΔF. This configuration corresponds to the PLL circuit in the first embodiment, and the above-described configuration example such as the configuration example of the FM demodulator 6 (wobble PLL 6) can be applied to the PLL circuit in the second embodiment as it is.

  Next, the operation of the optical disk device of the first and second embodiments will be described with reference to the drawings.

  FIG. 3 shows the operation when the inner periphery of the disc is reproduced by CAV control and then seeked to the outer periphery. Until just before the seek, the PLL follows the reproduction RF signal. After seeking, the linear velocity changes greatly, and the unrecorded area continues in the figure. When the channel frequency changes, it takes a long time to establish phase synchronization only from the reproduced RF signal. This is also due to the fact that the frequency band of the reproduction RF signal is relatively wide. If an unrecorded area continues, it takes time to synchronize accordingly.

  The wobble signal can obtain information almost continuously except for defects and the band is relatively narrow, and the wobble PLL 6 completes phase synchronization in a short time even if the frequency changes. Therefore, the signal Fwbl corresponding to the wobble frequency also converges in a short time. After adding Fwbl and the output signal ΔF of the loop filter 52, by controlling the frequency of the local oscillator 53, an error from the reproduced RF signal channel clock frequency is obtained while oscillating at a frequency equivalent to Fwbl on average. It operates so that ΔF corrects. Therefore, even if the linear velocity (channel frequency) is switched or an unrecorded area exists, the oscillation frequency of the reproduction PLL can be brought close to the original reproduction channel frequency. The closer the frequency deviation is, the shorter the time required for pulling in, so that the phase can be immediately synchronized with the reproduction RF data.

  The present invention has another advantage in addition to being able to realize short-time phase synchronization. That is, since the frequency deviation due to the disk eccentricity can be continuously detected by the frequency detector (wobble PLL 6) constituted by the PLL, the eccentricity can be compressed without increasing the loop gain of the RF-PLL5. Therefore, it becomes possible to make the loop characteristic low gain, and the clock jitter can be compressed, leading to improvement in the reliability of the reproduction information.

  The present invention can be used for an optical disk device such as a CD and a DVD, and is particularly suitable for CAV reproduction of an optical disk device recorded with high density.

It is a block diagram which shows 1st Embodiment in this invention. It is a block diagram which shows 2nd Embodiment in this invention. It is a timing diagram explaining operation | movement of this invention. It is an open loop characteristic figure of PLL. It is a phase error compression characteristic figure by a PLL gain. It is a block diagram of the PLL apparatus using a prior art.

Explanation of symbols

1 Disc medium 2 Pickup 3 Actuator servo 4 RF amplifier 5 RF-PLL
6 Wobble PLL (FM demodulator)
7 Band pass filter 8 Pulse generator 51, 61 Phase comparator 52, 62 Loop filter 53, 63 Local oscillator 54 Adder 64 Divider

Claims (11)

In a PLL circuit including a PLL that generates a clock signal whose phase is synchronized with an RF signal read from an optical disk medium,
An FM demodulator for inputting a wobble signal read from the optical disk medium simultaneously with the RF signal and outputting a frequency signal corresponding to the frequency of the wobble signal;
The PLL sets a frequency to be the center of the clock signal based on the frequency signal output from the FM demodulator.
A PLL circuit characterized by that. The frequency signal is a voltage value corresponding to the frequency of the wobble signal,
The PLL has a voltage controlled oscillator that changes the frequency of the clock signal according to a control voltage,
The control voltage is a sum of a voltage value of the frequency signal and a voltage value corresponding to a phase difference between the RF signal and the clock signal.
The PLL circuit according to claim 1.
In a PLL circuit including a PLL that generates synchronization timing from a first signal,
An FM demodulator for inputting a second signal in which the channel frequency and the frequency ratio of the first signal are constant and frequency information is obtained substantially continuously;
The PLL sets an operation center frequency of the PLL based on an output signal of the FM demodulator.
A PLL circuit characterized by that. On the control input side of the local oscillator in the PLL, a limiter for setting an upper limit and a lower limit of the frequency of the synchronization timing based on the output signal of the FM demodulator is provided.
The PLL circuit according to claim 3. When the PLL is a first PLL,
The FM demodulator comprises a second PLL;
The PLL circuit according to claim 3 or 4, characterized in that
Concentric or spiral tracks are formed on a disk-shaped recording medium, the tracks meander in a minute sine wave having a substantially constant period, and the recorded information on the tracks is synchronized with the meandering of the tracks. For optical disk media formed
Pick-up means for reading the recorded information from the rotating optical disc medium;
A servo mechanism for controlling the reading position of the pickup means;
Recording information detection means for detecting recording information from an RF signal which is a reflected light detection signal of a recording mark and a space row obtained from the pickup means;
An FM demodulator for inputting a wobble signal which is a change detection signal due to meandering of the track obtained from the pickup means;
A PLL circuit that sets an operation center frequency of the PLL by an output signal of the FM demodulator and generates a synchronization timing for operating the recording information detection unit from the RF signal;
An optical disc apparatus comprising: On the control input side of the local oscillator in the PLL, a limiter for setting an upper limit and a lower limit of the frequency of the synchronization timing based on the output signal of the FM demodulator is provided.
The optical disc apparatus according to claim 6. When the PLL is a first PLL,
The FM demodulator comprises a second PLL;
8. The optical disk apparatus according to claim 6, wherein In the RF signal, a fixed-length reproduction block is continuous, and a single frequency signal is inserted at a specific position of the reproduction block,
In the wobble signal, address information for identifying the reproduction block is embedded,
Detecting means for detecting the address information from the wobble signal;
Estimating means for estimating a region where the single frequency included in the RF signal is inserted from the address information detected by the detecting means;
Means for increasing the gain of the PLL circuit relative to the region estimated by the estimating means;
The optical disc apparatus according to claim 6, wherein the optical disc apparatus includes: An optical disk medium in which tracks are formed concentrically or spirally on a disk-shaped recording medium, prepits are arranged at equal intervals on the track, and recording information is formed in a region other than the prepits on the track with a constant linear density for,
Pick-up means for reading the recorded information from the rotating optical disc medium;
A servo mechanism for controlling the reading position of the pickup means;
Recording information detection means for detecting recording information from an RF signal which is a reflected light detection signal of a recording mark and a space row obtained from the pickup means;
An FM demodulator for inputting a pre-pit reproduction signal obtained from the pickup means;
A PLL circuit that sets an operation center frequency of the PLL by an output signal of the FM demodulator and generates a synchronization timing for operating the recording information detection unit;
An optical disc apparatus comprising: On the control input side of the local oscillator in the PLL, a limiter for setting an upper limit and a lower limit of the frequency of the synchronization timing based on the output signal of the FM demodulator is provided.
The optical disc apparatus according to claim 10.

Images