WO2006129478A1

WO2006129478A1 - Pll circuit and optical disc apparatus

Info

Publication number: WO2006129478A1
Application number: PCT/JP2006/309787
Authority: WO
Inventors: Hiromi Honma
Original assignee: Nec Corporation
Priority date: 2005-05-31
Filing date: 2006-05-17
Publication date: 2006-12-07
Also published as: JP2006338716A

Abstract

[PROBLEMS] To provide an optical disc apparatus wherein even when channel frequencies are switched due to a seek or even when there exists an unwritten area just before, a data recording area, in which data have been recorded at high densities, can be read from the front of the data recording area without errors. [MEANS FOR SOLVING PROBLEMS] An FM demodulator (6 of Fig.1) continuously detects the frequency of a second signal to acquire frequency information (Fwbl), and a signal, which is obtained by adding an output (ΔF) of a loop filter (52 of Fig. 1) to the frequency information (Fwbl), is used as a control input of a local oscillator (53 of Fig. 1) in a PLL loop (5 of Fig. 1) receiving a first signal as its input. A fast phase pull-in can be achieved by using the second signal, the frequency information of which can be always acquired, to control the center frequency of the local oscillator (53 of Fig. 1).

Description

Specification

PLL circuit and optical disk apparatus

Technical field

[0001] The present invention relates to a phase-locked loop (PLL) circuit used for an optical disc or the like, especially when the channel frequency is switched or there is an unrecorded area immediately before. This relates to a PLL circuit with high-speed pull-in and stability for reproduction without error.

Background art

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

[0003] In general, an optical disk device includes a pickup having a servo mechanism that can accurately follow a radial and vertical direction of a laser spot focused on the surface of a rotating disk medium. Scan the upper guide groove (groove track). Vertical control is called focus cinder servo and radial control is called tracking servo.

[0004] During recording, the temperature of the minute spot focused on the medium surface is increased by increasing the light intensity of the laser beam, thereby causing a physical change (change, magnetic domain inversion, etc.) Form. During playback, a beam with a light intensity that does not cause physical changes is irradiated, and changes in the amount of reflected light are detected by a photodetector. This detection signal is called a reproduction RF (Radio Frequency) signal.

[0005] In order to detect the reproduction RF signal power information, a PLL circuit is required for synchronous clock extraction. Figure 4 shows the open loop characteristics of a typical PLL. Normally, in a PLL circuit that generates phase synchronization information from only the reproduced RF signal, the disk eccentricity is compressed, so that the loop characteristics are 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 this happens, the noise band passing through the PLL will increase, and the accuracy of the synchronous clock will be degraded in the form of clock jitter. Although the effect on noise is improved by reducing the gain of the PLL, the compression gain for the eccentric frequency becomes A2, which causes a phase shift when playing a disc with a large amount of eccentricity. As a result, the reproduction performance deteriorates. Figure 5 shows the phase error on a time axis in a typical PLL. As is clear from Fig. 5, the force that can compress fluctuations due to eccentricity at high gains, the compression effect decreases at low gains.

[0006] On the other hand, when recording information, 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 the continuity of recorded information, improving accessibility, and avoiding overwriting of recorded areas. There are two methods for 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 in the groove track.

[0007] In a magneto-optical disk or DVD-RAM, a VFO area that also has a single frequency force for a PLL and a pre-pit in which physical address information is embedded are formed in advance on an information track, and this information is reproduced. Specify the position with. 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 the pre-pit area.

[0008] In CD-R / RW, DVD-R / RW, and DVD + RZRW, a pre-pit formed on an information track cannot be used because a recorded disc needs to be reproduced by a ROM drive. Therefore, a wobble track type disk that is wobbled in the radial direction when the groove track is cut is used. Address information is embedded in CD by wobbling frequency modulation and in DVD + RZRW by phase modulation. In DVD-R / RW, a pre-called land pre-pit in which address information is embedded is distributed over the area (land area) between the group track and the adjacent group track in synchronization with the wobbling phase.

[0009] The wobbling frequency must be higher than the tracking servo tracking band and low frequency that does not affect the playback RF signal. , 0 \ 0—1 ^ 71 ^^ 71 ^^ 1 selects 1 « ^? 1/186 channel frequency, and DVD + RZRW selects 1/32. Wobbling can detect the differential force of the output signal of a photodetector that divides the reflected light of the disk force into two in the radial direction. This detection signal is hereinafter referred to as “wobble signal”. A wobble signal has a low signal-to-noise ratio (SNR), but phase information can always be obtained with a relatively narrow bandwidth, so a stable channel clock can be generated by a PLL. Therefore, by identifying the physical position by detecting the modulated wobble signal or reproducing the land preamble, and recording the information in synchronization with this wobble PLL clock, the correct length of information is recorded in an arbitrary area on the disc. It is possible to do this. Therefore, the ratio between the channel frequency of the reproduced RF signal and the fundamental frequency of the wobble signal is constant even if the disk rotation speed changes.

[0010] There are mainly two types of disk rotation control methods. The simplest is the CLV (Constant Linear Velocity) control method, which controls the spindle speed so that the frequency of the wobble signal is constant. However, in the case of CLV control, the spindle rotation speed changes about 2.4 times on the inner and outer circumferences, so the spindle control waiting time is increased during random access, and this consumes much power. This is a problem. For this reason, CAV (Co tanttant

An increasing number of devices use the Angular Velocity control method. In this method, since the spindle is always rotated at a constant speed, the rotation waiting time 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. In addition, a wobble PLL with a wide cap challenge and a PLL for playback RF signals are required.

[0011] By the way, in DVD-RAM, a pre-pit header is adopted following the random accessibility of the magneto-optical disk, and there is a recording area following the unrecorded area. That is, after the playback PLL is disconnected in the unrecorded area, the PLL pull-in is completed immediately from the beginning of the recording area, and data playback is requested. In the unrecorded area, the output of the phase comparator in the playback PLL can be expected to be “0” on average, but the local oscillator frequency may shift in some cases. Phase pull-in must be completed in the VFO area at the beginning of the recording area, but phase pull-in does not complete if the frequency shifts significantly in the unrecorded area Can be considered. 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.

[0012] One technique for solving the above problem is disclosed in Patent Document 1. Mainly DVD

This system is intended to assist RAM synchronization. In this method, a selection switch is provided in the reproduction PLL input stage for generating the synchronized clock of the reproduced RF signal, and either the reproduced RF signal or the wobble synchronization clock power is shifted. When the RF signal is not detected, sometimes select the double sync clock. 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.

[0013] However, there is a problem that a delay occurs in order to prevent erroneous determination of the presence or absence of a reproduction RF signal due to a differential, and the VFO is equivalently shortened due to this delay. A technique for avoiding this problem is disclosed in Patent Document 2. Figure 6 shows the configuration.

The channel clock reproduction system 100 includes an optical pickup 12 that reads a recorded signal recorded on an optical disc 11, an RF amplifier 14, a bandpass 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 frequency divider 163 of 1Z186. 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 disc 11 is read out via the optical pickup 12. Explanation 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 header region signal and the low frequency fluctuation component are removed by the band pass filter 17. The phase comparator 161 of the wobble PLL block 16 is a frequency divider of a wobble signal and a wobble double clock signal which is an output signal of the voltage controlled oscillator 163. Compares the phase with the divided signal of 186 by 64 and outputs a phase error signal. The phase comparator 1601 has 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. The phase error 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 double clock signal having a frequency corresponding to the input VCO control voltage. This wobble double clock signal has a frequency 186 times the wobble frequency in the steady state, which is a frequency corresponding to the reproduction rate of the reproduction signal including the header data. The wobble double 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 double clock signal, and outputs a phase error signal. This phase comparator 155 outputs a phase error signal having a polarity that increases the frequency of the output signal of the voltage controlled oscillator 153 when the phase of the RF signal is advanced with respect to the phase of the double clock signal. . On the other hand, the phase comparator 156 compares the phases of the doubled clock signal and the channel clock signal and outputs a phase error signal. This phase comparator 156 outputs a phase error signal having a polarity that increases the frequency of the output signal of the voltage controlled oscillator 153 when the phase of the wobble double clock signal is advanced with respect to the phase of the channel clock signal. To do.

[0018] The phase error signal, which is the output of the phase comparator 155, and the phase error signal, which is the output of the phase comparator 156, are added at a predetermined ratio in the signal adder 154. 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.

[0019] 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 between the wobble synchronization clock and the VC0153 Take.

[0020] Then, the phase of the RF signal is φr, the phase of the wobble synchronization clock is φw, and the RF synchronization clock If the phase of φ is φ P, the phase error φ after addition is

φ = K1 (r- w) + K2 (w- p)

Furthermore, when K1 = K2 is corrected, φ becomes irrelevant to φw,

φ = Κ1 (Γ-ρ)

It becomes. Since it is controlled by the PLL so that φ = 0, (! ^ Is !!). Moreover, the switching switch is not necessary, and there is no problem due to an RF signal judgment error.

Patent Document 1: JP 2002-298367 A

Patent Document 2: JP 2001-52450 A

Disclosure of the invention

Problems to be solved by the invention

[0022] By the way, the wobble signal after information recording is subject to the interference of the reproduced RF signal, and its SNR is very low. Therefore, even with such a wobble signal power, it is difficult to match the phase even if the reproduction channel clock is generated, and an error of about several channel clocks is included with respect to the channel clock. This maximum deviation is the channel clock. In that case, the output of the phase comparator 155 must output a phase error of 2ππ even if the RF synchronization clock is correctly synchronized to the RF signal. Ordinary playback RF signals often contain many frequency components and have a low SNR. It is difficult to stably and accurately generate phase error information of 2π or more from such a signal even if a phase frequency comparator is used. 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.

[0023] HD, the next-generation optical disc standard

DVD-RW (High Definition DVD-Rewritable) has a lower resolution of playback RF signals than DVD, and PRML (Partial

Response Maximum Likelihood) is assumed. Therefore, the SNR of the phase error information obtained by the reproduction signal power is further reduced. HD

DVD-RW, like DVD + RZRW, has only a phase-modulated wobble signal and no preamble header, but requires random access similar to DVD-RAM. In other words, it is necessary to correctly play back the recorded portion that follows the unrecorded portion. DVD-R In AM, in addition to the VFO area at the beginning of the recording part, there is a VFO area in the prepit header immediately before the recording part VFO.

DVD-RW only has 71B VFO area at the beginning of the recording part. For this reason, if the frequency is greatly shifted, even the frequency pull-in may not be possible. In addition, because phase error information is low SNR, PLL phase synchronization in a shorter time than DVD-RAM with pre-pits is a major issue. In CAV operation, the channel frequency changes from 100% to 240% on the inner and outer circumferences, making it more difficult to play back the first block.

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. There is.

Means for solving the problem

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). The control input of the local oscillator (53 in Fig. 1) in the PLL loop (5 in Fig. 1) that receives the reproduction RF signal is equivalent to the output (AF) of the loop filter (52 in Fig. 1) and the wobble signal frequency. Use the sum of the FM demodulator output (Fwbl). As a result, the PLL loop (5 in Fig. 1) operates to cancel the error between the wobble frequency equivalent signal (Fwbl) and the channel frequency of the reproduced RF signal. Synchronized with this PLL clock, the reproduction data is detected from the reproduction RF signal.

[0026] Even if the linear velocity changes, the frequency ratio of the wobble signal and the reproduction RF signal is constant and does not change. The reconstructed RF signal can always detect the phase information from the force wobble signal that may not be obtained in some cases. 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 the output signal of the FM demodulator corresponding to this wobble signal frequency as a frequency offset to the local oscillator frequency of the regenerative RF PLL, it is possible to make it almost coincide with the channel frequency. As a method of adding the output signal of the FM demodulator as a frequency offset, either a method of presetting frequency values at regular intervals or a method of always counting as a frequency offset may be employed. Since the detection signal corresponding to the frequency includes an error of about several channel clocks, the reproduced RF signal is used to correct this. Therefore, the timing can be generated more quickly and stably than when the phase synchronization signal is generated only from the reproduced RF signal. Therefore, it is possible to establish the phase synchronization of the recording part after seeking or following the unrecorded part in a short time.

[0027] The PLL circuit according to the present invention includes a first PLL loop that generates a synchronization timing signal based on a first signal, and a second signal that has a constant channel frequency and frequency ratio of the first signal. And an FM demodulator for acquiring frequency information,

The first PLL loop sets an operation center frequency based on the frequency information output from the FM demodulator.

The PLL circuit according to the present invention can be applied to an optical disc apparatus as one application example. The technique of Patent Document 2 uses the phase of a wobble signal, whereas in the present invention, the frequency of a wobble signal can be used as the second signal. As described above, the phase of the wobble signal includes many errors. Compared to this, 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 is completed as soon as the RF signal is input by accurately tracking the frequency of the RF signal with the wobble signal. Can do.

For example, the frequency signal is a voltage value corresponding to the frequency of the wobble signal, and the PLL has a voltage controlled oscillator that changes the frequency of the clock signal according to a control voltage, and the control voltage is It is the sum of the voltage value of 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.

[0030] The present invention can also be configured as follows.

That is, the PLL circuit according to the present invention can obtain frequency information with a constant frequency ratio and substantially continuously with the channel frequency of the first signal in the PLL circuit that generates the synchronization timing from the first signal. The second signal is given and FM recovery is performed using the second signal as input. This is a simple configuration that has a modulator and sets the operation center frequency of the PLL according to the output of the FM demodulator.

In addition, the PLL circuit of the present invention may be configured such that a limiter is provided on the local oscillator control input side in the PLL and the upper and lower limits of the synchronization timing frequency are limited based on the output of the FM demodulator. Is. The FM demodulator may be constituted by a second PLL.

[0033] In addition, the optical disc apparatus according to the present invention has concentric or spiral tracks formed on a disc-shaped recording medium, and the tracks meander in a minute sine wave shape having a substantially constant period in the track lateral direction. In an optical disk medium in which recorded information is formed on the track in synchronism with the track meandering! Next, 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 a reflected light detection signal of the recording mark Z space row obtained by the pickup force. RF signal force Consists of means for detecting recorded information, an FM demodulator that receives a wobble signal that is a change detection signal due to the track meandering obtained by the pickup force, and a PLL circuit that generates the RF signal force synchronization timing The PLL circuit may be configured such that the operation center frequency of the PLL is set by the output of the FM demodulator and the recording information detection means is operated by the synchronization timing of the PLL.

[0034] Further, the optical disc apparatus of the present invention may be provided with a limiter on the local oscillator control input side in the PLL so as to limit the upper and lower limits of the synchronization timing frequency based on the output of the FM demodulator. Is. In this case, the FM demodulator may be constituted by a second PLL.

[0035] Further, the optical disc apparatus of the present invention includes the RF signal in which a certain fixed-length reproduction block is continuous and a single frequency signal is inserted at a specific position of the reproduction block, and the reproduction block. Means for detecting the address information from the wobble signal, and means for estimating the single frequency region included in the RF signal from the wobble signal with respect to the wobble signal embedded with identifying address information; The PLL frequency gain may be increased only during the period detected by the single frequency domain estimation unit. It is a thing.

[0036] Further, in the optical disc apparatus of the present invention, prepits are arranged on the track at equal intervals with respect to the concentric or spiral track on the disc-shaped recording medium, and recording is performed in an area other than the prepit on the track. Pickup means for reading the recorded information from the rotating optical disk medium to an optical disk medium in which information is formed with a constant linear density, a servo mechanism for controlling the reading position of the pickup means, and the pickup Obtained recording mark Z means to detect RF signal force recording information that is reflected light detection signal of space column, FM demodulator that receives the pick-up force obtained pre-pit reproduction signal, and generate RF signal force synchronization timing The PLL circuit is connected to the center of operation of the PLL by the output of the FM demodulator. Set the number is a good casting be configured for operating said recording information detection means by the synchronous timing of the PLL.

[0037] Further, a limiter may be provided on the local oscillator control input side in the PLL, and the upper and lower limits of the synchronization timing frequency may be limited based on the FM demodulator output. The invention's effect

[0038] As described above, according to the present invention, it is possible to improve the throughput during reproduction. 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. .

[0039] Further, according to the present invention, the reproduction performance can be improved. The reason is that the frequency fluctuation due to eccentricity included in the reproduction RF signal can be compressed using the wobble signal, and the loop gain of the reproduction PLL can be lowered.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1]

A PLL circuit according to the present invention will be described as a first embodiment. As shown in FIG. 2, the PLL circuit according to the first embodiment of the present invention generates a synchronization timing signal using the first signal as an input, and a reproduction RF (Radio Frequency) PLL loop 5 and the second signal are input. As the second signal of And an FM demodulator 6 for generating information (Fwbl) corresponding to the frequency. The reproduction RF PLL loop is expressed as RF-PLL.

The RF-PLL 5 includes a phase comparator 51, a loop filter 52, a calorie calculator 54, and a local oscillator 53. The phase comparator 51 has a function of detecting a phase shift between the first signal and the output signal of the local oscillator 53. The loop filter 52 has a function of filtering the signal φ 1 output from the phase comparator 51 and outputting a signal AF. The adder 54 adds the information (F wbl) output from the FM demodulator 6 and the signal AF output from the phase comparator 51, and outputs the addition signal to the local oscillator 53. It has a function to do. The local oscillator 53 has a function of outputting the synchronization timing signal Frf based on the signal output from the adder 54. A part of the signal from the local oscillator 53 is feed knocked to the phase comparator 51.

[0043] The FM demodulator 6 functions as a frequency detector that continuously detects the frequency of the second signal and generates information (Fwbl) corresponding to the frequency of the second signal. Here, the relationship between the first signal and the second signal will be described. As the second signal, a signal having a constant channel frequency and frequency ratio of the first signal is given.

The operation of the PLL circuit according to the first embodiment of the present invention shown in FIG. 2 will be described. When a first signal and a second signal having a constant frequency ratio are input, the first signal is input to the RF-PLL 5, and the second signal is input to the FM demodulator 6.

[0045] The phase comparator 51 of the RF-PLL5 receives the first signal and the output signal of the local oscillator 53 as inputs, and detects a phase shift between the first signal and the output signal of the local oscillator 53 Then, the detection signal φ 1 is output to the loop filter 52. The loop filter 52 filters the detection signal φ 1 and outputs an output signal A F to the adder 54.

[0046] FM demodulator 6 receives the second signal, generates information (Fwbl) corresponding to the frequency of the second signal, and outputs the information (Fwbl) to adder 54.

[0047] The adder 54 adds the output signal AF output from the loop filter 52 and the frequency information (Fwbl) generated by the FM demodulator 6, and the added signal is used as frequency offset information. To the local oscillator 53. The local oscillator 53 in the PLL loop 5 transmits based on the addition signal output from the adder 54 and outputs a synchronization timing signal Frf. The center frequency of the local oscillator 53 is determined by the frequency information (Fwbl) output from the FM demodulator 6, and the frequency error is absorbed by the signal AF output from the loop filter 52.

[Embodiment 2]

Next, an example in which the PLL circuit according to Embodiment 1 of the present invention shown in FIG. Note that the application example of the PLL circuit according to the first embodiment of the present invention shown in FIG. 2 is not limited to the optical disc apparatus shown in FIG. 1, but can be applied to other than the optical disc apparatus.

An optical disk device 10 shown in FIG. 1 is used for writing record information on the disk medium 1 or reproducing information recorded on the disk medium 1. As the disk medium 1, CD-RZRW, DVD-RZRWZRAM, or the like is used. In the disk medium 1, concentric or spiral tracks are formed on a disk-shaped recording medium, the tracks meander in a minute sine wave having a period in the track lateral direction, and recorded information is recorded on the tracks. Use a structure that is recorded in synchronization with the meandering track. Alternatively, in the disk medium 1, concentric or spiral tracks are formed on the disk-shaped recording medium, blits are arranged on the tracks at equal intervals, and recording information is recorded in a linear density on the track other than the bullets. A structure with a fixed and recorded structure may be used. Furthermore, an optical disk medium having a structure in which a groove track is formed in a spiral shape or a concentric shape on the recording surface of the disk-shaped recording medium may be used. The groove track is formed by wobbling at a constant amplitude in the radial direction and a period that is an integral multiple of the recording pit. The wobbling phase or frequency of the disk medium 1 may be modulated by physical address information. The disk medium 1 is rotationally controlled by a spindle motor (not shown).

As shown in FIG. 1, the optical disk apparatus according to Embodiment 2 of the present invention includes a pickup 2, an actuator servo 3, an RF (Radio Frequency) amplifier 4, a bandpass filter (BPF) 7, 2 has a PLL circuit (5, 6) shown in FIG. [0052] The pickup 2 is composed of a drive system such as a laser diode, an optical element, and an objective lens, and causes the condensed beam spot to follow the groove track of the disk medium 1. The pickup 2 detects vertical and radial misalignment with the disk medium 1 by reflected light from the disk medium 1, and the actuator servo 3 serves as a driving actuator for the objective lens of the pickup 2. By controlling, the pickup 2 is caused to follow the disc surface deviation and disc eccentricity of the disc medium 1 accurately. The pickup 2 receives reflected light from the disk medium 1 with a photodetector and outputs a weak received light signal to the RF amplifier. Further, the photodetector of the pickup 2 is divided into two in the radial direction and receives the reflected light from the disk medium 1, and the pickup 2 outputs a difference signal from the photodetector as a wobble signal. The wobble signal includes fluctuations in the radial direction of the groove track as amplitude information.

Further, the pickup 2 records user information as a minute mark row in a track on the recording surface of the disk medium 1. The recording is performed in synchronization with a recording clock obtained by multiplying the wobble signal by N times. N is an integer from 32 to 192, and is uniquely determined by the type of recording media. The reproduction RF signal including user information can be extracted as the sum of the output signals from the divided photodetectors of the pickup 2, and the frequency ratio between the channel clock and the wobble signal of the reproduction RF signal is constant.

The RF amplifier 4 amplifies a weak received light signal from the pickup 2 and separates the amplified received light signal reproduction RF signal and wobble signal, and the reproduction RF signal described later RF-PLL 5 And a function of outputting the wobble signal to a wobble PLL (phase locked loop) 6 which will be described later. The BPF (Band Pass Filter) 7 has a function of limiting the band of the wobble signal output from the RF amplifier 4. Since the band of the wobble signal is relatively narrow, SNR can be earned by limiting the band with BPF7.

As shown in FIG. 1, a PLL loop is used as the FM demodulator 6 that continuously detects the frequency of the wobble signal from the output power of the BPF 7 in the PLL circuit shown in FIG. In Fig. 1, in order to distinguish the PLL loop 5 for the regenerative RF signal and the PLL loop 6 as the FM demodulator 6, they are hereinafter referred to as RF-PLL5 and wobble PLL6. [0056] The RF-PLL5 in FIG. 1 has the same configuration as the RF-PLL5 shown in FIG. The wobble PLL (6) as the FM demodulator 6 applied to FIG. 1 is constructed to include a phase comparator 61, a loop filter 62, a local oscillator 63, and a frequency divider 64.

The phase comparator 61 has a function of detecting a phase difference between the wobble signal and the output signal from the frequency divider 64. The loop filter 62 has a function of filtering the detection signal from the phase comparator 61 and outputting the output signal to the adder 54 of the RF-PLL 5 and the local oscillator 63. The local oscillator 63 has a function of controlling a transmission frequency based on an output signal from the loop filter 62, outputting a recording clock signal, and feeding back a part of the signal to the frequency divider 64. ing. The frequency divider 64 has a function of dividing the output signal from the local oscillator 63 and outputting the divided signal to the phase comparator 61. Since the output signal of the local oscillator 63 is fed back to the phase comparator 61 through the frequency divider 64, the frequency of the local oscillator 63 is controlled so that the output signal of the phase comparator 61 approaches '0'. .

[0058] If there is a function of multiplying the output signal of the local oscillator 63, the frequency divider 64 is not necessarily provided (ie, N = l). 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 wobble signal may be input directly to the wobble PLL 6. If the wobble PLL 6 is locked, the wobble signal frequency and the control input (Fwbl) of the local oscillator 63 have a one-to-one correspondence. That is, the wobble PLL 6 operates as an FM demodulator of a wobble signal. The wobble PLL 6 may be composed of a digital circuit in order to perform analog / digital conversion of the wobble signal with an AZD converter and to digitally process the converted digital signal. The FM demodulator 6 may be configured to measure the wave number of a wobble signal, for example. In addition, the input signal of the FM demodulator 6 may be a signal such as a DVD-RAM prep header, not a wobble signal. In this case, the FM demodulator 6 may measure the pre-pit header interval or pre- The VFO frequency in the pit header may be detected. When pre-pit information is used, a guide groove without wobbling may be used.

[0059] The phase comparator 51 generates a phase difference between the reproduction RF signal and the output signal of the local oscillator 53. To do. The output signal of the phase comparator 51 is filtered through the loop filter 52 and output as ΔF. After adding this output signal AF 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 reproduced 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 to correct it. A comparator may be added between the RF amplifier that outputs the reproduction RF signal and the phase comparator 51. An upper / lower limiter for limiting the upper and lower limits of the output signal A F may be provided in the loop filter 52 so that the frequency does not deviate greatly when a reproduction RF signal cannot be obtained. Further, the RF-PLL 5 may be constituted by a digital circuit in order to perform analog / digital conversion of the reproduction RF signal output from the RF amplifier 4 by an AZ D converter and to digitally process the converted digital signal. The configuration of the RF-PLL 5 and the wobble PLL 6 described based on FIG. 1 may be applied to the configuration of the RF-PLL 5 and the FM demodulator 6 in the PLL circuit shown in FIG.

[0061] Furthermore, the pulse forming means 8 is provided. The pulsing means 8 binarizes the reproduction RF signal output from the RF amplifier 4 at every timing of the synchronization timing signal extracted by the RF-PLL 5, detects reproduction data, and outputs the reproduction data It has a function. The reproduction data is subjected to processing such as ECC (Error Correction Code) correction by a demodulation circuit (not shown) and the like, and information is extracted based on the reproduction data. Retrieve information. The pulsing means 8 may be replaced with a PRML detector. The PRML detector decodes the same signal as the bit information on the disc as data from a reproduced waveform distorted by waveform interference.

Response) After waveform processing, ML (Maximum Likelihood) selects the most probable playback waveform and outputs the playback data.

[0062] HD DVD—When the disk format is such that the phase synchronization VFO area is added before the user information, such as RW, and the physical address information can be read out by the wobble signal power, the address information from the wobble signal can be read. It is also possible to provide a detector for detecting the noise, thereby estimating the VFO region on the reproduction RF signal and increasing the loop gain of the RF-PLL 5 only during the VFO period. In this case, the phase pull-in time can be further shortened. Next, the operation of the optical disc device 10 according to Embodiment 2 of the present invention will be described. Pickup 2 receives the reflected light from disk medium 1 with a built-in photo disc, and outputs the weak received signal to RF amplifier 4. When the RF amplifier 4 receives a weak received light signal from the pickup 2, it amplifies the received light signal, separates it into a wobble signal and a reproduced RF signal, and outputs the reproduced RF signal to the RF-PLL 5. The wobble signal is output to BPF 10.

When receiving the wobble signal from the RF amplifier 4, the BPF 10 limits the band, obtains a wobble signal having a good SNR, and outputs the wobble signal to the wobble PLL 6.

The phase comparator 61 of the wobble PLL 6 detects the phase difference between the output signal of the BPF 7 and the output signal of the frequency divider 64 and outputs the detection signal to the loop filter 62. The loop filter 62 filters the detection signal and then outputs the output signal to the adder 54 of the RF-PLL 5 and the local oscillator 63 of the wobble PLL 6. The local oscillator 63 receives the signal from the loop filter 62, controls its oscillation frequency, and outputs a recording clock (CLK) signal. The output signal of the local oscillator 63 is fed back to the phase comparator 61 through a frequency divider 64. As a result, the frequency control is performed so that the output signal of the phase comparator 61 approaches “0”.

[0066] When the reproduction RF signal from the RF amplifier 4 is input to the RF—PLL 5, the phase comparator 51 of the RF—PLL 5 detects the phase difference between the reproduction RF signal and the output signal of the local oscillator 53. The detection signal is output to the loop filter 52. The loop filter 52 outputs the output signal A F to the adder 54 after filtering the detection signal. The adder 54 adds the output signal AF output from the loop filter 52 and the output signal Fwbl output from the loop filter 62 of the wobble PLL 6, and adds the added signal to the local oscillator of the RF-PLL 5 Output to 53. The local oscillator 53 is controlled based on the addition signal output from the adder 54. The local oscillator 53 oscillates at the center frequency Fwbl and is phase-synchronized with the reproduction RF signal, thereby generating an RF synchronization clock (CLK) signal. Is output.

[0067] The pulsing means 8 receives the reproduction RF signal output from the RF amplifier 4 and the synchronization timing signal Frf output from the local oscillator 53 of the RF-PLL5 as input, and for each extracted synchronization timing, The reproduction RF signal is binarized and the reproduction data is detected. In the playback data For this purpose, ECC (Error Correction Code) correction or the like is performed by a demodulation circuit (not shown) or the like, and information is extracted.

Next, features of the optical disc device according to Embodiment 1 of the present invention shown in FIG. 2 will be described with reference to FIG.

FIG. 3 shows an operation when data recorded in the inner peripheral area of the disk medium 1 is reproduced and then seeked to the outer peripheral area under CAV control. In FIG. 3, immediately before seeking, that is, during the period in which the data recorded in the inner peripheral area of the disk medium 1 is being reproduced, the RF-PLL5 and the wobble PLL6 are applied to the reproduction RF signal being reproduced by the pickup 2. Is following.

[0070] After the playback area from the disk medium 1 seeks to the inner peripheral area force outer peripheral area, as is apparent from FIG. 3, the linear velocity changes greatly, and the unrecorded area continues to the recording surface of the disk medium 1. Exist. In this case, when the channel frequency is changed, it takes a long time to establish the phase synchronization of the PLLs 5 and 6 by the reproduction RF signal output from the RF amplifier 4. This is also due to the relatively wide frequency band of the reproduced RF signal. If an unrecorded area continues, time will be spent on the phase synchronization accordingly.

[0071] The wobble signal output from the RF amplifier 4 can obtain information almost continuously except the differential and the band may be relatively narrow. The wobble PLL 6 is phase-synchronized in a short time even if the frequency changes. Is completed. Therefore, the signal Fwbl corresponding to the wobble frequency also converges in a short time.

In the optical disc device 10 according to Embodiment 1 shown in FIG. 2, the signal Fwbl output from the wobble PLL 6 and the output signal AF output from the loop filter 52 of the RF-PLL 5 are added and the addition is performed. The frequency of the local oscillator 53 is controlled based on the signal. Therefore, in the optical disc apparatus 10 according to the embodiment of the present invention, the local oscillator 53 oscillates at a frequency equivalent to the signal Fwbl on average, and the phase comparator 51 outputs the synchronization timing output from the local oscillator 53. An error between the signal Frf and the reproduction RF signal channel clock frequency output from the RF amplifier 4 is detected, and the word difference is filtered by the loop filter 52 so that the output signal AF is corrected. Therefore, even if the linear velocity (channel frequency) is switched or there is an unrecorded area on the recording surface of the disk medium 1, R The oscillation frequency of F—PLL (reproduction PLL) 5 can be close to the original reproduction channel frequency. The closer the frequency deviation is, the shorter the time required for pull-in, so it is possible to immediately synchronize the phase with the reproduced RF data.

[0073] The embodiment of the present invention has another advantage in addition to being able to realize short-time phase synchronization. In other words, since the frequency shift caused by the disk eccentricity can be detected continuously by the frequency detector (wobble PLL 6) composed of the PLL, the eccentricity can be compressed without increasing the loop gain of the RF-PLL5. Therefore, it is possible to make the loop characteristic low gain, and the clock jitter can be compressed, which leads to an improvement in the reliability of reproduced information. Industrial applicability

The present invention described above 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.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of an optical disc apparatus according to Embodiment 2 of the present invention.

FIG. 2 is a block diagram showing a configuration of a PLL circuit according to Embodiment 1 of the present invention.

FIG. 3 is a timing diagram illustrating features of the optical disc device according to Embodiment 2 of the present invention.

[Fig. 4] A diagram showing the characteristics of the open norape of the PLL.

FIG. 5 is a phase error compression characteristic diagram based on PLL gain.

FIG. 6 is a block diagram of a PLL device using conventional technology.

Explanation of symbols

[0076] 1 disc media

2 Pickup

3 Actuator servo

4 RF amplifier

5 RF-PLL

6 wobble PLL (FM demodulator)

7 Bandpass filter

8 Pulsed means , 61 phase comparator, 62 loop filter, 63 local oscillator adder

Divider

Claims

The scope of the claims

[1] a first PLL loop that generates a synchronization timing signal based on the first signal;

An FM demodulator that acquires frequency information based on a second signal having a constant frequency ratio and a channel frequency of the first signal;

The PLL circuit according to claim 1, wherein the first PLL loop sets an operation center frequency based on the frequency information output from the FM demodulator.

[2] On the control input side of the local oscillator that oscillates at the operation center frequency in the first PLL loop, the upper and lower limits of the frequency of the synchronous timing signal on the basis of the frequency information output from the FM demodulator The PLL circuit according to claim 1, further comprising a limiter for setting

[3] The FM demodulator includes a second PLL loop configured to acquire frequency information as a frequency offset for setting an operation center frequency of the first PLL loop. The PLL circuit described.

[4] Optical disk medium power pickup means for reading recorded information;

A servo mechanism for controlling the reading position of the pickup means;

A first PLL loop that generates a synchronization timing signal based on the RF signal obtained by the pickup means force;

Recording information detecting means for detecting recording information from the RF signal based on the synchronization timing signal;

An FM demodulator that obtains frequency information based on the wobble signal obtained by the pickup means power;

The optical disk apparatus according to claim 1, wherein the first PLL loop sets an operation center frequency based on the frequency information output from the FM demodulator.

[5] Within the first PLL loop, on the control input side of the local oscillator that oscillates at the operation center frequency, the upper and lower limits of the frequency of the synchronization timing signal on the basis of the frequency information output from the FM demodulator 5. The optical disc device according to claim 4, further comprising a limiter for setting

[6] To set the operating center frequency of the first PLL loop as the FM demodulator 5. The optical disk device according to claim 4, wherein a second PLL loop for acquiring frequency information as a frequency offset of the second PLL loop is configured.

[7] The RF signal is a signal in which a fixed-length reproduction block is continuous and a single frequency signal is inserted at a specific position of the reproduction block.

Detection means for detecting the address information based on the wobble signal in which address information for identifying the reproduction block is embedded;

From the address information detected by the detection means, estimation means for estimating a region where the single frequency included in the RF signal is inserted;

7. The optical disc apparatus according to claim 6, further comprising gain control means for increasing the gain of the first PLL loop only during a period detected by the estimation means.

[8] In the optical disk medium, a concentric or spiral track is formed on the disk-shaped recording medium, the track meanders in a minute sine wave having a period in the track lateral direction, and recorded information is recorded on the track. 7. The optical disc apparatus according to claim 6, wherein the recording is performed in synchronization with the meandering of the track.

[9] In the optical disk medium, tracks are formed concentrically or in a spiral shape on the disk-shaped recording medium, prepits are arranged at equal intervals on the track, and recorded information is recorded in an area other than the prepit on the track. 7. The optical disc apparatus according to claim 6, wherein recording is performed with a constant linear density.

[10] The FM demodulator receives an RF signal read from the optical disc medium and a wobble signal read from the optical disc medium force, and outputs a frequency signal corresponding to the frequency of the wobble signal. 2. The optical disk device according to claim 1, wherein

[11] The frequency signal is a voltage value corresponding to the frequency of the wobble signal,

The first PLL loop has a voltage controlled oscillator that changes a frequency of a clock signal whose phase is synchronized with the RF signal by a control voltage,

The optical control signal according to claim 10, wherein 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. Equipment.

[12] An information acquisition step of acquiring frequency information based on a second signal having a constant channel frequency and frequency ratio of the first signal;

Based on the frequency information acquired in the information acquisition step !, a setting step for setting the operation center frequency of the PLL loop;

A phase synchronization method comprising: generating a synchronization timing signal based on the first signal by causing oscillation in the PLL loop based on the set operation center frequency.

13. The phase synchronization method according to claim 12, wherein upper and lower limits of the frequency of the synchronization timing signal are set based on the frequency information.

[14] An information acquisition step of acquiring frequency information based on the wobble signal among the RF signal and the wobble signal obtained from the information power read from the optical disc medium;

A setting step for setting an operation center frequency of the PLL loop based on the frequency information; and

Generating in the PLL loop based on the set operation center frequency, and generating a synchronization timing signal based on the RF signal;

An information processing method comprising: executing a detection step of detecting the RF signal force recording information based on the synchronization timing signal.

15. The information processing method according to claim 14, wherein upper and lower limits of the frequency of the synchronization timing signal are set based on the frequency information.