JP4218409B2 - Optical disc apparatus and seek speed control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention For optical disc The present invention relates to an optical disc apparatus capable of recording or reproducing a signal. The present invention also relates to a seek speed control method in such an optical disc apparatus.
[0002]
[Prior art]
In an optical disc apparatus capable of recording / reproducing signals to / from an optical disc, a tracking error signal obtained when a laser spot crosses a track is obtained as a traverse signal during a seek operation.
For example, by performing binarization on the basis of the zero level of such a traverse signal, a binarized signal indicating the timing at which the laser spot crosses the track is obtained.
[0003]
By obtaining the binarized signal of such a traverse signal and counting the number of edges, the number of tracks traversed by the laser spot during the seek operation can be counted. Further, the seek moving speed can be obtained by measuring the time length between the edges of the binarized signal.
In the optical disc apparatus, control for reaching the vicinity of the seek target is performed based on the information on the number of crossing tracks and the moving speed calculated in this way.
[0004]
By the way, as an optical disk, there is a wobble format in which data recording is performed by wobbling a track.
In the wobble format optical disc, a waveform on which a high-frequency component as shown in FIG. 11A is superimposed is obtained as the traverse signal as described above due to the influence of wobbling of the track.
[0005]
In this case, as can be seen from the figure, noise is superimposed on the original signal component (zero crossing period) of the traverse signal TRV. Therefore, simply detecting the zero level of the traverse signal TRV is accurate. A zero cross point cannot be detected. As a result, an accurate edge interval cannot be obtained even as the binarized signal T (FIG. 11B) of the traverse signal TRV used for controlling the seek operation described above.
[0006]
For this reason, in the conventional optical disc apparatus corresponding to such a wobble format, the zero cross point is detected after the high frequency component superimposed on the traverse signal TRV is attenuated by a low pass filter or the like as described above. It was like that.
As a result, an accurate binary signal T corresponding to the track crossing timing of the laser spot is obtained.
[Patent Literature]
JP-A-9-237423
[0007]
[Problems to be solved by the invention]
Here, in recent years, the track pitch has been extremely narrowed along with the high density recording of the optical disc. Even in such a high-density disk with an extremely narrow track pitch, there are some that adopt the wobble format as described above.
[0008]
As described above, when the wobble format is adopted for a high-density disk having an extremely narrow track pitch, the wobble width as viewed from the track pitch is larger than that of a normal disk. As a result, as the traverse signal TRV as shown in FIG. 11A, the frequency band of the signal component of the zero-cross period and the frequency band of the high-frequency signal component due to the wobbling of the track come closer.
[0009]
In this way, in a high-density disk in which the frequency band of the signal component of the zero crossing period and the frequency band of the wobble signal component are close to each other, for example, when the frequency of the traverse signal becomes high, such as during high-speed seek, It is known that a so-called “growing” phenomenon occurs.
That is, these two signal components interfere with each other by such a high-speed seek operation, and the zero cross period of the traverse signal TRV is obtained with a deviation from the track crossing timing of the actual laser spot at this time. Is.
[0010]
Thus, by obtaining the traverse signal TRV in which an error occurs in the zero cross period, even if the zero cross point is accurately detected from the traverse signal at this time, it is possible to accurately detect the crossing timing of the laser spot. A traverse signal TRV cannot be obtained.
If the accurate traverse signal TRV cannot be obtained in this way, the reliability of information on the seek movement speed, which is calculated based on the traverse signal TRV, is lowered.
As a result, when the above “beat” occurs, the seek operation performance is supposed to deteriorate.
[0011]
As a conventional related technique, for example, the above-described patent document discloses a technique for optimizing the binarization operation of the tracking error signal during the seek operation. However, the above-described “beat” occurs. In this case, even if the zero cross point is accurately detected as described above, it is not possible to obtain an accurate traverse signal TRV corresponding to the track crossing timing of the laser spot.
[0012]
[Means for Solving the Problems]
In view of the above-described problems, the present invention is configured as follows as an optical disc apparatus capable of recording or reproducing signals with respect to an optical disc on which a wobbled track is formed.
That is, while supporting an objective lens for writing or reading data with respect to the optical disc, the head means for performing laser irradiation and detection of reflected light using the objective lens as an output end, and the head means can be moved in the tracking direction. Transporting means.
The seek transfer speed when the head unit is transferred in the tracking direction by the transfer operation of the transfer unit is based on the tracking error signal generated from the reflected light detected by the head unit. Sequential Measuring means for measuring is provided, and further, averaging means for averaging the information on the seek transfer speed measured by the measuring means is provided.
In addition, control means for controlling the seek transfer speed of the head means is provided by controlling the transfer means based on at least information on the seek transfer speed averaged by the averaging means. .
[0013]
In the present invention, the seek speed control method is as follows.
In other words, the recording and reproduction of signals with respect to the optical disc on which the wobbled track is formed, and the objective lens for data writing or reading with respect to the optical disc is supported, and the laser having the objective lens as an output end are supported. A seek speed control method in an optical disc apparatus, comprising: head means for irradiating and detecting reflected light thereof; and transport means capable of transporting the head means in a tracking direction.
First, the seek transfer speed when the head unit is transferred in the tracking direction by the transfer operation of the transfer unit is based on the tracking error signal generated from the reflected light detected by the head unit. Sequential Execute the measurement procedure to be measured.
Then, an averaging procedure for averaging the information on the seek transfer speed measured by the measurement procedure is executed, and then the transfer is performed based on at least the information on the seek transfer speed averaged by the averaging procedure. By controlling the means, a control procedure for controlling the seek transfer speed of the head means was executed.
[0014]
In this way, by averaging the information on the seek transfer speed measured based on the tracking error signal, the tracking error signal is generated due to a so-called “beat” phenomenon, for example, when a high-speed seek is performed. Even when variations occur in the zero cross point, it is possible to average the variations and obtain more reliable seek transfer speed information.
Then, by controlling the seek transfer speed of the head means based on the averaged seek transfer speed information, a relatively stable seek operation can be achieved even when “beat” occurs during high-speed seek. Can be performed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The description will be made in the following order.
1. Overall configuration of optical disk device
2. Servo circuit configuration
3. Binarization circuit configuration
4). Summary and modification of embodiment
[0016]
1. Overall configuration of optical disk device
FIG. 1 shows the configuration of the optical disc apparatus 10 of this example.
First, the optical disc apparatus 10 shown in this figure can record or reproduce data corresponding to a so-called Blu-ray Disc as the disc 1 shown in the figure.
In this Blu-ray disc, for example, signal recording / reproduction is performed under the condition of a combination of a blue laser having a central emission wavelength of 405 nm and an objective lens having an NA of 0.85. Further, when the track pitch is 0.32 μm, the linear density is 0.12 μm / bit, and a data block of 64 KB (kilobyte) is used as one recording / reproducing unit and the format efficiency is about 82%, it is 23 for a disk having a diameter of 12 cm. .3 GB (gigabyte) capacity can be recorded and reproduced.
If the linear density is 0.112 μm / bit in the same format, a capacity of 25 GB can be recorded and reproduced. Furthermore, the recording layer can have a multilayer structure. For example, when the recording layer has two layers, the capacity can be about 46.6 BG or 50 GB.
[0017]
The disc 1 as such a Blu-ray disc is loaded on a turntable (not shown) and is driven to rotate at a constant linear velocity (CLV) by the spindle motor 12 during recording / reproducing operation.
The optical pickup (optical head) 11 reads data on the disk 1, that is, data by emboss pits in the case of a ROM disk and data by phase change marks in the case of a rewritable disk.
In the case of a rewritable disc, ADIP information and disc information embedded as wobbling of the groove track are read out.
When recording on a rewritable disc, the optical pickup 11 records data on the groove track as a phase change mark.
[0018]
In the optical pickup 11, a laser diode serving as a laser light source, a photodetector for detecting reflected light, an objective lens serving as an output end of the laser light, laser light is irradiated onto the disk recording surface via the objective lens, and An optical system (not shown) for guiding the reflected light to the photodetector is formed.
[0019]
In the optical pickup 11, the objective lens is held so as to be movable in the tracking direction and the focus direction by a biaxial mechanism.
The entire optical pickup 11 can be moved in the radial direction of the disk by a thread mechanism 13.
The laser diode in the optical pickup 11 is driven to emit laser light by a drive signal (drive current) from the laser driver 23.
[0020]
Reflected light information from the disk 1 is detected by a photo detector, converted into an electrical signal corresponding to the amount of received light, and supplied to the matrix circuit 14.
The matrix circuit 14 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as photodetectors, and generates necessary signals by matrix calculation processing.
For example, a high frequency signal (reproduction data signal) corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, and the like are generated.
As the tracking error signal, for example, a push-pull signal is generated when the disk 1 is a rewritable disk, and a DPD signal is generated when the disk 1 is a ROM disk.
Further, a push-pull signal is generated as a signal related to groove wobbling, that is, a signal for detecting wobbling.
The matrix circuit 14 may be formed in the optical pickup 11 in some cases.
[0021]
The reproduction data signal output from the matrix circuit 14 is supplied to the reader / writer circuit 15, the focus error signal and tracking error signal are supplied to the servo circuit 21, and the push-pull signal, which is detection information of the wobbling groove, is supplied to the wobble circuit 18, respectively. The
[0022]
The reader / writer circuit 51 performs binarization processing on the reproduction data signal, reproduction clock generation processing by PLL, etc., reproduces data read from the phase change mark or emboss spot, and supplies it to the modulation / demodulation circuit 16 To do.
The modem circuit 16 includes a functional part as a decoder during reproduction and a functional part as an encoder during recording.
At the time of reproduction, as a decoding process, a run-length limited code is demodulated based on the reproduction clock.
[0023]
The ECC / scramble circuit 17 performs ECC encoding processing for adding an error correction code during recording and scrambling processing.
At the time of reproduction, descrambling processing for scramble processing is performed and ECC decoding processing for error correction is performed.
At the time of reproduction, the data demodulated by the modem circuit 16 is taken into an internal memory, and reproduction data is obtained by performing descrambling processing and error detection / correction processing.
[0024]
Data decoded up to reproduction data by the ECC / scramble circuit 17 is read based on an instruction from the system controller 20 and transferred to an AV (Audio-Visual) system 60.
[0025]
When the disk 1 is a rewritable disk, the push-pull signal output from the matrix circuit 14 as a signal related to the wobbling of the groove is processed in the wobble circuit 18. The push-pull signal as ADIP information is demodulated in the wobble circuit 18 and supplied to the address decoder 19 as a data stream that constitutes an ADIP address.
The address decoder 19 decodes the supplied data, obtains an address value, and supplies it to the system controller 20.
The address decoder 19 generates a clock by PLL processing using the wobble signal supplied from the wobble circuit 18, and supplies it to each unit as an encode clock at the time of recording, for example.
[0026]
When the disk 1 is a ROM disk, the address decoder 19 performs frame sync synchronization processing from the reproduction data signal, and reads address information, that is, the physical sector number, from the reproduction data signal. The obtained address information is supplied to the system controller 20. In this case, as a clock for address detection, a reproduction clock by a PLL in the reader / writer circuit 15 is used.
[0027]
At the time of recording on the rewritable disc, the recording data is transferred from the AV system 60. The recording data is sent to the memory in the ECC / scramble circuit 17 and buffered.
In this case, the ECC / scramble circuit 17 performs error correction code addition, scramble processing, subcode addition, and the like as encoding processing of the buffered recording data.
The data subjected to the ECC encoding and scramble processing is subjected to RLL (1-7) PP modulation in the modulation / demodulation circuit 16 and supplied to the reader / writer circuit 15.
As described above, the clock generated from the wobble signal is used as the reference clock for the encoding process during recording.
[0028]
The recording data generated by the encoding process is subjected to a recording compensation process by the reader / writer circuit 15 and fine adjustment of the optimum recording power and adjustment of the laser drive pulse waveform with respect to the recording layer characteristics, laser beam spot shape, recording linear velocity, etc. Etc. are sent to the laser driver 23 as a laser drive pulse.
The laser driver 23 applies the supplied laser drive pulse to the laser diode in the optical pickup 11 to perform laser emission driving. As a result, pits (phase change marks) corresponding to the recording data are formed on the disc 1.
[0029]
The laser driver 23 includes a so-called APC circuit (Auto Power Control), and the laser output is monitored regardless of the temperature or the like while monitoring the laser output power by the output of the laser power monitoring detector provided in the optical pickup 11. Control to be constant. The target value of the laser output at the time of recording and reproduction is given from the system controller 20, and control is performed so that the laser output level becomes the target value at the time of recording and reproduction.
[0030]
The servo circuit 21 generates various servo drive signals for focus, tracking, and thread from the focus error signal and tracking error signal from the matrix circuit 14 and executes the servo operation.
That is, a focus drive signal and a tracking drive signal are generated according to the focus error signal and tracking error signal, and the focus coil and tracking coil of the biaxial mechanism in the pickup 51 are driven. As a result, an optical pickup 11, a matrix circuit 14, a servo circuit 21, and a tracking servo loop and a focus servo loop by a biaxial mechanism are formed.
[0031]
The servo circuit 21 turns off the tracking servo loop and outputs a jump drive signal in accordance with a track jump command from the system controller 20 to execute a track jump operation.
Further, the servo circuit 21 generates a thread drive signal based on a thread error signal obtained as a low frequency component of the tracking error signal, a seek operation control from the system controller 20, and the like, and drives the thread mechanism 13. Although not shown, the sled mechanism 13 has a mechanism including a main shaft that holds the optical pickup 11, a sled motor, a transmission gear, and the like. The sled mechanism 13 drives the sled motor according to a sled drive signal. The slide movement is performed.
The configuration of the servo circuit 21 of this example will be described later.
[0032]
The spindle servo circuit 22 performs control to rotate the spindle motor 12 by CLV.
The spindle servo circuit 22 obtains the clock generated by the PLL processing for the wobble signal as the current rotational speed information of the spindle motor 12 and compares it with predetermined CLV reference speed information to generate a spindle error signal. .
At the time of data reproduction, the reproduction clock (clock serving as a reference for decoding processing) generated by the PLL in the reader / writer circuit 15 becomes the current rotational speed information of the spindle motor 12, and this is used as a predetermined CLV. A spindle error signal can also be generated by comparing with the reference speed information.
The spindle servo circuit 22 outputs a spindle drive signal generated according to the spindle error signal, and causes the spindle motor 12 to perform CLV rotation.
The spindle servo circuit 22 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 20, and executes operations such as starting, stopping, acceleration, and deceleration of the spindle motor 12.
[0033]
Various operations of the servo system and the recording / reproducing system as described above are controlled by a system controller 20 formed by a microcomputer.
The system controller 20 executes various processes in accordance with commands from the AV system 60.
[0034]
For example, when a write command (write command) is issued from the AV system 60, the system controller 20 first moves the optical pickup 11 to an address to be written. Then, the ECC / scramble circuit 17 and the modulation / demodulation circuit 16 perform the encoding process as described above on the data transferred from the AV system 60 (for example, video data of various systems such as MPEG2 or audio data). Then, recording is executed by supplying the laser drive pulse from the reader / writer circuit 15 to the laser driver 23 as described above.
[0035]
Further, for example, when a read command for requesting transfer of certain data (such as MPEG2 video data) recorded on the disk 1 is supplied from the AV system 60, seek operation control is first performed for the instructed address. That is, a command is issued to the servo circuit 21, and the access operation of the optical pickup 11 targeting the address specified by the seek command is executed.
Thereafter, operation control necessary for transferring the data in the designated data section to the AV system 60 is performed. That is, data reading from the disk 1 is performed, decoding / buffering in the reader / writer circuit 15, the modulation / demodulation circuit 16, and the ECC / scramble circuit 17 is executed, and the requested data is transferred.
[0036]
At the time of recording or reproducing these data, the system controller 20 controls access and recording / reproducing operations using the ADIP address detected by the address decoder 19 or the address information in the reproduced data signal.
[0037]
In the example of FIG. 1, the optical disk apparatus 10 connected to the AV system 60 is used. However, the optical disk apparatus of the present invention may be connected to, for example, a personal computer.
Furthermore, there may be a form that is not connected to other devices. In that case, for example, an operation unit and a display unit may be provided so that recording and reproduction are performed according to a user operation. Also, a terminal part for inputting / outputting various data may be formed as an interface part for inputting / outputting data.
Of course, there are various other configuration examples. For example, an example of a reproduction-only device is also conceivable.
[0038]
2. Servo circuit configuration
FIG. 2 shows an internal configuration example of the servo circuit 21 shown in FIG.
First, the illustrated focus servo circuit 30 and tracking servo circuit 31 perform necessary processing such as phase compensation processing on the focus error signal FE and tracking error signal TE supplied from the matrix circuit 14 respectively, thereby performing focus servo. Signals and tracking servo signals are generated. The focus servo signal and tracking servo signal generated in this way are supplied to the focus driver 33 and the tracking driver 34, respectively.
The focus driver 33 and the tracking driver 34 are each based on the focus servo signal and the tracking servo signal supplied as described above, and a focus drive signal for driving the biaxial mechanism in the optical pickup 11 shown in FIG. FD and tracking drive signal TD are output.
Thereby, focus servo control and tracking servo control based on the focus error signal FE and the tracking error signal TE output from the matrix circuit 14 are realized.
[0039]
Based on the low frequency component of the tracking servo signal generated by the tracking servo circuit 31 as described above, the sled servo circuit 32 follows the movement of the objective lens moved in the outer peripheral direction by the tracking operation. A sled servo signal for generating the signal is generated.
Then, the sled servo signal generated in this way is supplied to the terminal t2 of the switch SW shown in the figure.
[0040]
In the switch SW, the terminal t2 is selected in response to the tracking servo being on. As a result, the thread servo signal from the thread servo circuit 32 is supplied to the thread driver 35 via the terminal t1 shown correspondingly when the tracking servo is on.
As a result, the thread driver 35 in this case drives the thread mechanism 13 by the thread drive signal SD based on the thread servo signal. When the tracking servo is on, the optical pickup 11 follows the movement of the objective lens. Thus, a state controlled to slide is obtained.
[0041]
In the switch SW, the terminal t3 is selected in response to the tracking servo being off. As a result, when the tracking servo is off, the output of the seek control circuit 40 shown in the figure is supplied to the thread driver 35 via the terminal t1.
Note that such terminal switching of the switch SW is performed based on the control of the system controller 20 described above.
[0042]
Based on the access command from the system controller 20, the seek control circuit 40 performs control for moving the optical pickup 11 to the vicinity of a predetermined address instructed by this command.
The seek control circuit 40 recognizes the number of tracks from the current track to the instructed track based on the access command, and outputs a preset pulse corresponding to the recognized number of tracks.
In the case of this example, the seek control circuit 40 sequentially compares the information on the seek movement speed of the optical pickup 11 that is moved based on the pulses thus output with the reference speed information that is preset inside. To be done. The seek speed is controlled by controlling the level of the thread drive signal SD at this time according to the comparison result. That is, by controlling the seek speed based on the result of sequentially comparing the seek movement speed and the predetermined reference speed in this way, the optical pickup 11 can be reached more precisely near the target track. Is.
Such seek speed control by the seek control circuit 40 is performed based on the value of the track counter 37 described below and information on the seek movement speed as the track period value Tcc output from the track period counter 38. It is what is said.
[0043]
The binarization circuit 36 receives the tracking error signal TE output from the matrix circuit 14 shown in FIG.
The binarization circuit 36 performs binarization processing on the tracking error signal TE (hereinafter referred to as the traverse signal TRV) under the traverse state, particularly during the seek operation, as the tracking error signal TE. Is done. Then, the binarization result is output as a binarized signal T shown in the figure.
The internal configuration of the binarization circuit 36 will be described later.
[0044]
The track counter 37 counts the number of tracks traversed by the objective lens during such a seek operation by counting the number of edges of the binarized signal T. Then, the count value is supplied as the track count value TC to the seek control circuit 40 described above.
Thus, the track count value TC supplied to the seek control circuit 40 is used, for example, when referring to the reference speed information for performing the seek speed control described above.
[0045]
The track cycle counter 38 counts the time length between the edges of the binarized signal T based on a clock with a predetermined cycle. That is, the seek movement speed of the optical pickup 11 is measured by this. The value counted in this way is output to the averaging circuit 39 as the track period value Tcc.
[0046]
The averaging circuit 39 temporarily holds the track cycle value Tcc output from the track cycle counter 38 and calculates the average value of the track cycle value Tcc held in this way for each predetermined number of tracks.
That is, for the track period value Tcc held in this way, for example, the sum of the predetermined number of tracks is divided by the value of the predetermined number of tracks, and the average value of the track period value Tcc for each predetermined number of tracks. Is what you get.
Then, the average value calculated in this way is supplied to the seek control circuit 40 described above.
[0047]
In this way, the track period value Tcc used for seek speed control in the seek control circuit 40 is averaged, so that, for example, a so-called “beat” in the case of high-speed seek is performed. Even when a variation occurs in the zero cross point of the traverse signal TRV due to the phenomenon, this variation can be averaged. As a result, even when such a “growing” phenomenon occurs, the seek control circuit 40 obtains relatively reliable speed information in which variations of such zero cross points are averaged. Is possible.
In other words, the seek control circuit 40 at this time can perform relatively stable seek speed control based on such highly reliable seek speed information.
[0048]
3. Binarization circuit configuration
Subsequently, a configuration example of the binarization circuit 36 shown in FIG. 2 will be described.
Here, prior to the description of the internal configuration of such a binarization circuit 36, first, a description will be given step by step from the problems of the conventional binarization circuit provided in the servo circuit of the optical disc apparatus. Let's go.
First, as described above, when a wobble format in which data recording is performed by wobbling a track such as the disk 1 of this example is adopted, the binarization circuit 36 is affected by the influence of such wobbling. As the input traverse signal TRV, a waveform in which a high frequency component as shown in FIG. 11A is superimposed is obtained.
As described above, one of the methods for appropriately detecting the zero cross point corresponding to this is a method of removing such a high-frequency component with a low-pass filter.
[0049]
However, in this case, like the disk 1 of this example, depending on the optical disk that employs the wobble format for the high-density disk, the wobble width as viewed from the track pitch becomes larger than that of a normal disk. As a result, as the traverse signal TRV, the frequency band of the signal component of the zero crossing period and the frequency band of the high-frequency signal component due to the wobbling of the track approach each other.
[0050]
In this way, when the frequency band of the signal component of the zero crossing period comes close to the frequency band of the high frequency signal component due to the wobbling of the track, the high frequency component is attenuated by a low-pass filter or the like as described above. It becomes difficult to detect an accurate zero cross point.
In other words, the method using such a low-pass filter is a method that uses a difference in frequency band between a signal component as a detection target and a noise component (wobble component) superimposed thereon, and thus the frequency of both signals is used in this way. When the band approaches, it becomes difficult to extract only the signal component to be detected.
[0051]
Therefore, conventionally, there is a technique using a hysteresis comparator as a technique capable of detecting a zero cross point without using such a low-pass filter.
FIG. 4 shows a circuit configuration for binarizing an input signal on which a noise component is superimposed using such a hysteresis comparator.
In this figure, the comparator 100 compares the traverse signal TRV with the comparator level cr output from the hysteresis level generation circuit 101 as shown in the figure.
In this case, the output cc of the comparator 100 is input to the hysteresis level generation circuit 101. The hysteresis level generation circuit 101 operates to switch the value of the comparator level cr to be output in accordance with the change in the level of the comparator output cc input in this way.
That is, at this time, as the value of the comparator output cc changes according to the comparison result in the comparator 100, the value of the comparator level cr input to the comparator 100 is switched.
[0052]
Such an operation by the hysteresis comparator is, for example, as shown in FIG.
First, in FIG. 7, as the above-mentioned comparison level cr, as shown in the figure, a level lower than the zero level is set corresponding to the case where the level of the traverse signal TRV is positive. The When the traverse signal TRV has a negative polarity, a level higher than the zero level is set.
That is, in this case, when the traverse signal TRV decreases from the positive polarity side and rises from the negative polarity side, it has a hysteresis level as shown in the figure with reference to the zero level (that is, the original comparison level). The two comparator levels cr are switched.
[0053]
At this time, for example, if the comparator 100 simply performs detection based on the zero level, when the noise component of the traverse signal TRV falls below the zero level as shown at time points t1 to t2 in the figure, the original zero cross point is detected. The comparator 100 will respond before the time t3. That is, this causes unnecessary chattering.
On the other hand, by setting the hysteresis level as described above, such unnecessary chattering can be prevented as can be seen from the figure. In other words, as the hysteresis level at this time, by setting a sufficient level corresponding to the amplitude level of the noise component as shown in the figure, such unnecessary chattering is prevented and the original zero cross point is accurately set. It can be detected.
[0054]
As a result, accurate edge timing corresponding to this zero cross point can be obtained as the binarized signal T in this case as shown in the figure.
From this fact, if such a hysteresis comparator is used, the traverse signal TRV can be binarized accurately without removing the noise component using the low-pass filter as described above. .
[0055]
Thus, in the hysteresis comparator as shown in FIG. 4, unnecessary chattering can be prevented by setting the hysteresis level to a sufficient level corresponding to the amplitude level of the noise component.
However, in other words, in such a hysteresis comparator, chattering cannot be effectively prevented unless the above hysteresis level is set sufficiently high.
[0056]
As described above, if the hysteresis level has to be relatively large, for example, when the traverse signal TRV is attenuated and the amplitude level cannot be sufficiently obtained, the zero-cross detection point is shifted. Become.
That is, for example, assuming that the traverse signal TRV has attenuated in the case of FIG. 7 above, in this case, a sufficient level cannot be obtained as the amplitude of the noise component in the vicinity of the time point t3 in the figure. If the level of the traverse signal TRV is not sufficiently lowered to the negative polarity side, the zero cross point is not detected.
[0057]
Therefore, in the prior art, an output correction circuit 102 as shown in FIG. 5 is provided at the subsequent stage of the hysteresis comparator so as to be able to cope with the attenuation of the traverse signal TRV while preventing unnecessary chattering. There is something that was made.
In the output correction circuit 102, the level of the traverse signal TRV is changed to the comparator level after the change in the period after the level of the output cc of the comparator 100 is changed and the comparator level cr is switched accordingly. The logic circuit is configured to determine whether or not the time exceeding cr is equal to or longer than a predetermined time length. As a result of such determination, the value of the binarized signal T is changed in accordance with a case where the time during which the level of the traverse signal TRV exceeds the comparison level cr is equal to or longer than a predetermined time length. Is.
[0058]
The operation of the hysteresis comparator provided with such an output correction circuit 102 is as shown in FIG.
First, as the hysteresis level in this case, a low level as shown in the figure is set as compared with the case of FIG. 7 so as to be able to cope with the attenuation of the input signal as described above. For this reason, unnecessary chattering occurs in the comparator output cc after time t3, and the comparator level cr flickers as shown in the figure.
[0059]
However, in this case, as described above, the output correction circuit 102 is provided at the subsequent stage of the hysteresis comparator, so that an operation for controlling the binarized output corresponding to such chattering is performed. It will be.
That is, according to the output correction circuit 102, first, after the comparison level cr (comparator output cc) changes at the time point t3 in the figure, the time length during which the level of the traverse signal TRV exceeds this level is measured. It becomes.
When the measured time length is equal to or longer than the predetermined time length as described above, the time t4 is reached, and the value of the binarized signal T is changed accordingly as shown in the figure.
That is, it is determined that the reaction is not a response to the vicinity of the peak level of the noise component based on such a predetermined time length, and chattering is removed with this.
[0060]
In this way, in the configuration of the hysteresis comparator provided with the output correction circuit 102, unnecessary chattering can be prevented while setting the hysteresis level low. In other words, this makes it possible to obtain a stable binary signal T based on a relatively accurate zero-cross detection point while corresponding to the attenuation of the traverse signal TRV.
[0061]
However, as understood from the above description, in the configuration in which the output correction circuit 102 shown in FIG. 5 is provided, a certain determination time (time point t3 in FIG. 8) for preventing chattering due to the influence of noise components To t4). This means that a corresponding delay occurs in the detection timing of the zero cross point.
[0062]
In this way, a delay occurs in the detection timing of the zero cross point, so that when the signal having a particularly high frequency is input as the traverse signal TRV, such a shift in the detection point due to the determination time becomes unacceptable. There is a risk that.
And since the deviation of the zero cross detection point becomes unacceptably large in this way, the accuracy of the binarized signal T is remarkably deteriorated, and the reliability of the seek speed information calculated based on this accuracy is also obtained. Will be significantly reduced.
As a result, in the optical disc apparatus having the hysteresis comparator having the configuration shown in FIG. 5, there is a possibility that a stable seek operation cannot be obtained when the traverse signal TRV becomes a high frequency due to, for example, high-speed seek. It was.
[0063]
Therefore, in this example, the binarization circuit 36 shown in FIG. 2 is configured as shown in FIG.
First, in FIG. 3, the traverse signal TRV shown in FIG. 2 is supplied to the inverting terminal of the comparator 41. The comparator level cr from a hysteresis level generation circuit 47 described later is input to the non-inverting terminal of the comparator 41. The comparator 41 uses a binary signal corresponding to the result of comparing the level of the traverse signal TRV and the comparison level cr input in this manner as a comparator output cc, and a binarized output correction circuit 42. Output for.
[0064]
In the binarized output correction circuit 42, a delay circuit (Z ^-1 ) 43, an output correction counter 44, a comparator 45, and a latch circuit 46.
In the binarized output correction circuit 42, the delay circuit 43 receives the comparator output cc from the comparator 41 and outputs it to the output correction counter 44 at a timing shifted by one clock. That is, according to such a delay circuit 43, the value of the comparator output cc one clock before is input to the output correction counter 44.
[0065]
The output correction counter 44 also receives the comparator output cc from the comparator 41. That is, the current value of the comparator output cc is input to the output correction counter 44 together with the value one clock before from the delay circuit 43.
Then, as a result of comparing the current comparator output cc value input in this way with the value of the comparator output cc one clock earlier, if the two inputs are equal, the count value of itself is incremented by one. If both inputs are not equal, the count value is reset to zero.
[0066]
The value of the output correction counter 44 is input to the comparator 45. Then, the latch circuit shown in the figure corresponds to the case where the count value is larger than the threshold value as a result of comparing the value of the output correction counter 44 input in this way with a predetermined threshold value set inside. For example, H level is output to 46.
The threshold value set in the comparator 45 in this way corresponds to a determination time for preventing chattering due to a noise component superimposed on the input traverse signal TRV, as will be described later. Therefore, the threshold value set in the comparator 45 is set to prevent chattering according to the frequency band of the noise component assumed in the input traverse signal TRV and the hysteresis level set at this time. A value corresponding to an appropriate time length should be set.
[0067]
The latch circuit 46 receives the comparator output cc from the comparator 41 and updates the value of the comparator output cc based on the output of the comparator 4. That is, the value of the comparator output cc is updated only in accordance with the H level output from the comparator 45.
The latch output of the latch circuit 46 is output from the binarization circuit 36 as a binarization signal T as shown in the figure. At the same time, this latch output is also input to the hysteresis level generation circuit 47 shown in the figure.
[0068]
The hysteresis level generation circuit 47 determines a comparison level cr to be input to the non-inverting terminal of the comparator 41.
That is, at this time, when the output of the latch circuit 46 (binarized output correction circuit 42) is at the H level, the hysteresis level generation circuit 47 determines the comparison level cr corresponding to the H level. To do. Further, when the output of the binarized output correction circuit 42 is at L level, the comparison level cr corresponding to this is determined.
As a result, the comparator level cr input to the comparator 41 via the hysteresis level generation circuit 47 can be switched between two different values according to the output result of the binarization output correction circuit 42. .
In addition, from such a configuration, in this case, the timing at which the comparator level cr is switched is not the timing at which the level of the comparator output cc is switched, but the timing at which the output of the binarized output correction circuit 42 is switched. It is intended to respond to.
Note that the accuracy can be improved by adding, for example, a buffer or an OP amplifier to the hysteresis level generation circuit 47.
[0069]
The operation of the binarization circuit 36 of this example will be described with reference to FIG.
First, the hysteresis level in this case is set to have a certain width with reference to the zero level, for example, as shown in the figure, by the operation of the hysteresis level generation circuit 47 as described above.
As a result, it becomes possible to remove the chattering that is apparent when the vicinity of the peak level of the high-frequency component of the traverse signal TRV falls below the zero level as shown at the time points t1 to t2.
[0070]
Then, after time t2, it is assumed that the level of the traverse signal TRV again falls below the zero level and reaches time t3 when it further falls below the comparator level cr.
Accordingly, the value of the comparator output cc changes corresponding to the comparison result of the comparator 41 at this time.
However, in this case, unlike the configuration shown in FIG. 5, since the binarized output correction circuit 42 is provided immediately after the comparator 41, the comparator level cr is immediately adjusted accordingly. Cannot be switched. That is, as the comparison level cr in this case, the value changes according to the output of the binarized output correction circuit 42 as described above. In response to this, it is made to not change immediately.
Accordingly, the comparison level cr in this case is maintained without being switched at this time point t3, as shown in FIG.
[0071]
As an operation of the binarized output correction circuit 42 after the time point t3, first, the count value of the output correction counter 44 is reset to zero in accordance with the change in the value of the comparator output cc as described above. After the count value is reset to zero in this way, the count is based on the comparison result between the value of the comparator output cc one clock before supplied from the delay circuit 43 again and the current value of the comparator output cc. The operation will be performed.
[0072]
Since the level of the traverse signal TRV is maintained below the comparator level cr as shown in the figure after the time point t3, 1 is input to the output correction counter 44 in this case. The same value is input as the comparator output cc before the clock and the current one. As a result, the count value after time t3 is gradually incremented.
[0073]
As the count value of the output correction counter 44 is thus incremented, the count value approaches the predetermined threshold set in the comparator 45.
When such a count value exceeds the threshold value, the time t4 is reached, and the comparator 45 outputs an H level to the latch circuit 46. Further, in response to this, the output level of the latch circuit 46 is updated to a value corresponding to the comparator output cc inputted at this time.
[0074]
As a result, the output of the binarized output correction circuit 42 changes, and the level of the binarized signal T shown in the figure also changes at this time t4 as shown in the figure. That is, the zero cross point is detected here.
At the same time, the comparison level cr that changes in accordance with the output of the binarized output correction circuit 42 is changed after the time t4 as shown in the figure.
[0075]
In this manner, in the binarization circuit 36 of this example, even if the level of the traverse signal TRV reaches the comparison level cr, the level is maintained without immediately switching the comparison level cr. ing. Thereafter, the time length during which the level of the traverse signal TRV exceeds the maintained comparison level cr is measured by the count operation of the output correction counter 44.
Then, as a result of comparing such a count value with a predetermined threshold value in the comparator 45, the time length during which the level of the traverse signal TRV exceeds the maintained comparison level cr continues for a predetermined time or more. In this case, the comparator output cc is latched to perform binarization output.
That is, in this example, determination for removing chattering is performed for a time length in which the level of the traverse signal TRV exceeds the maintained comparison level cr.
[0076]
With such a binarization circuit 36 of this example, the determination time for chattering removal can be made shorter than in the configuration shown in FIG.
First, depending on the configuration of FIG. 5, when the level of the traverse signal TRV reaches the comparison level cr, the comparison level cr immediately changes (time point t3 in FIG. 8). Therefore, in this case, it is necessary to take a longer determination time for chattering removal than in the case of this example.
That is, as can be seen from a comparison between FIG. 6 and FIG. 8, in the case shown in FIG. 8, the comparator level cr thus changed is a criterion for determination. The period during which the traverse signal TRV exceeds the comparison level cr (that is, the return time of the noise amplitude of the traverse signal TRV) is clearly longer than in this example in which the comparison level cr does not change.
And by targeting the return time of such a long noise amplitude, a relatively long time corresponding to the return time of the noise amplitude corresponding to the determination time for chattering removal as described above. It must be.
Therefore, depending on the present example in which the comparison level cr is not immediately changed, the determination time for chattering removal can be made shorter than that of the conventional configuration.
[0077]
In this way, depending on the configuration of the binarization circuit 36 of this example, the determination time for binarization output can be shortened compared to the conventional configuration shown in FIG. The accuracy of T can be improved as compared with the prior art.
Since the accuracy of the binarized signal T can be improved in this way, the reliability of the seek speed information calculated based on this can be improved, and a stable seek operation can be obtained. .
[0078]
Therefore, the configuration of this example shown in FIG. 3 can be suitably applied even when a high frequency is input as the traverse signal TRV, and effectively suppresses deterioration of the stability of the seek operation during high-speed seek. It is something that can be done.
[0079]
In the binarization circuit 36 of this example, since the determination for the chattering removal is performed as described above, for example, as shown in the time points t5 to t6 in FIG. Even when the vicinity of the peak level of the component exceeds the comparison level cr, unnecessary flapping of the binarized signal T can be effectively suppressed.
In other words, in the binarization circuit 36 of this example as well, the hysteresis level can be set lower than the configuration shown in FIG. 4 and the input signal is attenuated, as in the configuration shown in FIG. Also, binarization can be performed appropriately.
[0080]
4). Summary and modification of embodiment
The optical disk device 10 as the embodiment has been described above.
As described above, in the optical disc apparatus 10 of this example, the averaging circuit 39 is provided in the subsequent stage of the track cycle counter 38 in the servo circuit 21 shown in FIG. The track period value Tcc as the seek speed information is averaged.
When the track period value Tcc is averaged in this way, for example, when the high-speed seek is performed, a variation in the zero cross point of the traverse signal TRV occurs due to a so-called “beat” phenomenon. In addition, it is possible to average this variation and obtain more reliable seek speed information.
In other words, this makes it possible to effectively suppress a decrease in the reliability of seek speed information input to the seek control circuit 40 when a so-called “beat” occurs. is there.
[0081]
In this way, the reliability of seek speed control performed by the seek control circuit 40 based on the seek speed information can be improved as compared with the prior art by suppressing the decrease in the reliability of the seek speed information. can do.
As a result, depending on the optical disc apparatus 10 of this example, it is possible to effectively suppress the deterioration of the performance of seek speed control when “beat” occurs.
[0082]
Here, in the configuration of the present example, it is not expected that a value completely corresponding to the actual seek speed at this time can be obtained as the track period value Tcc averaged by the averaging circuit 39. That is, as long as the measured seek speed information is averaged, it cannot completely match the actual seek speed.
However, at this time, when the zero-cross cycle of the traverse signal TRV is sufficiently short, for example, during high-speed seek, such a deviation of the value is considered to be relatively small, and this is considered acceptable. In such a high-speed seek, since “beat” may occur as described above, averaging by the averaging circuit 39 of this example is effective.
[0083]
On the other hand, the frequency of the traverse signal TRV is relatively low immediately after the start and end of the seek operation, for example, and the above-mentioned “beat” does not occur. In this case, however, the zero-cross cycle is increased instead. Therefore, there may be a case where the deviation of the averaged track period Tcc cannot be allowed.
[0084]
Therefore, as an embodiment, as a modification, a switching circuit 70 as shown in FIG. 9 is provided, and the track period Tcc to be input to the seek control circuit 40 is averaged according to conditions. Switch between input and non-input.
First, in this case, as shown in the figure, a switch for selectively selecting the terminal t2 and the terminal t3 with respect to the terminal t1 is provided as the switching circuit 70. The terminal t1 inputs the output of the track cycle counter 38, and the terminal t2 is connected to the seek control circuit 40. The terminal t3 is connected to the averaging circuit 39.
Then, for example, when the seek speed is slower than a predetermined speed under the control of the seek control circuit 40 or the system controller 20, the terminal t2 is selected, and if it is fast, the terminal t3 is selected.
[0085]
As a result, when the seek speed is relatively high and the traverse signal TRV has a high frequency and a “beat” is generated, the seek control circuit 40 can perform seek speed control based on the averaged track period Tcc. It becomes possible. Further, when the seek speed is relatively slow and the traverse signal TRV has a low frequency, the seek speed control can be performed based on the track period Tcc that is not averaged.
That is, depending on such a modification, it is possible to stably perform the seek speed control based on the track period value Tcc that is always reliable regardless of the seek speed.
[0086]
Incidentally, as shown in FIG. 3, the optical disc apparatus 10 of this example is provided with a binarization circuit 36 by a hysteresis comparator having a binarization output correction circuit 42.
In such a binarization circuit 36 of this example, when the frequency of the traverse signal TRV is low, for example, immediately after the start or end of the seek operation, the period of the noise component is also increased. Depending on the situation, it is not unthinkable that the determination of chattering removal described with reference to FIG. 6 becomes difficult.
Therefore, in this example, as another modification example, except that the frequency of the traverse signal TRV is sufficiently high and the frequency band between the noise component and the zero-crossing period is approximated, the noise component is passed through a low-pass filter, for example. A binarization may be performed based on the attenuated traverse signal TRV.
That is, when the frequency of the traverse signal TRV is sufficiently low, it is considered that there is a sufficient difference in the frequency band between the noise component and the zero crossing period, and therefore the noise component can be attenuated by the low-pass filter. is there. From this, if there is a possibility that the binarization of this example cannot be effectively performed due to the low frequency of the traverse signal TRV as described above, the noise component is removed from the traverse signal TRV in this way. It is intended to perform the digitizing operation.
[0087]
Such a configuration as another modified example is as shown in FIG. 10, for example.
In this case, a switching circuit 80 is provided for the input line of the traverse signal TRV to the binarization circuit 36 as shown. The switching circuit 80 is configured so that the traverse signal TRV input from the terminal t1 can be alternatively output via the terminal t2 or the terminal t3 shown.
The terminal t2 is connected to the binarization circuit 36 via a low pass filter (LPF) 81, and the terminal t3 is directly connected to the binarization circuit 36.
Then, under the control of the seek control circuit 40 or the system controller 20, the terminal t2 is selected when the seek speed is slower than a predetermined speed, and the terminal t3 is selected when the seek speed is high.
[0088]
Thereby, in response to the case where the frequency of the traverse signal TRV is low, such as immediately after the start of the seek operation or immediately before the end, the binarization operation based on the traverse signal TRV from which the noise component has been removed by the low-pass filter 81 can be performed. It becomes possible. That is, by removing the noise component in this way, the binarization circuit 36 can appropriately perform the binarization operation.
Further, when the frequency of the traverse signal TRV is high and the frequency band between the noise component and the zero-crossing period approaches, binarization is effectively performed by the binarization operation of this example as shown in FIG. Is possible.
As a result, depending on the configuration of such a modification, a more stable binary signal T can be obtained regardless of the seek speed.
[0089]
In the above embodiment, a Blu-ray disc is used as an example of the disc 1, but the present invention is an optical disc adopting a wobbling format, particularly suitable for a high-density disc with a narrow track pitch. Applicable.
[0090]
【The invention's effect】
As described above, in the present invention, For optical disc Optical disc capable of recording or playing back signals apparatus A head means for supporting an objective lens for data writing or reading with respect to the optical disc, performing laser irradiation and detection of reflected light using the objective lens as an output end, and the head means can be moved in the tracking direction. Transportation means.
Then, by the transfer operation of the transfer means, the seek transfer speed when the head means is transferred in the tracking direction is measured based on the tracking error signal, and the information of the seek transfer speed thus measured is averaged. Like to do.
In addition, the seek transfer speed of the head means is controlled by controlling the transfer means based on at least the information on the seek transfer speed averaged in this way.
[0091]
In this way, by averaging the information on the measured seek transfer speed, the zero cross point of the tracking error signal varies due to the so-called “beat” phenomenon, for example, when high-speed seek is performed. Even in this case, it is possible to average the variation and obtain more reliable information on the seek transfer speed.
Then, by controlling the seek transfer speed of the head means based on such reliable information on the seek transfer speed, a stable seek operation can be performed even when “beat” occurs during high-speed seek. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an optical disc apparatus as an embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of a servo circuit provided in the optical disc apparatus according to the embodiment.
FIG. 3 is a block diagram showing an internal configuration example of a binarization circuit provided in the servo circuit.
FIG. 4 is a block diagram showing a configuration of a conventional hysteresis comparator.
FIG. 5 is a block diagram showing a configuration of a conventional hysteresis comparator including an output correction circuit.
FIG. 6 is a diagram for explaining the operation of the binarization circuit according to the embodiment;
FIG. 7 is a diagram for explaining the operation of a conventional hysteresis comparator.
FIG. 8 is a diagram for explaining an operation of a conventional hysteresis comparator including an output correction circuit.
FIG. 9 is a block diagram showing a configuration of a modified example of the embodiment.
FIG. 10 is a block diagram showing a configuration of another modified example of the embodiment.
FIG. 11 is a diagram showing a traverse signal and its binarized signal when a wobbling format is adopted.
[Explanation of symbols]
1 disk, 10 optical disk device, 11 optical pickup, 13 thread mechanism, 20 system controller, 21 servo circuit, 30 focus servo circuit, 31 tracking servo circuit, 32 thread servo circuit, 33 focus driver, 34 tracking driver, 35 thread driver, 36 binarization circuit, 37 track counter, 38 track period counter, 39 averaging circuit, 40 seek control circuit, 41 comparator, 422 binarization output correction circuit, 43 delay circuit, 44 output correction circuit, 45 comparator, 46 latch Circuit, 47 hysteresis level generation circuit, 70, 80 switching circuit, 81 low-pass filter (LPF), SW switch

Claims (3)

As an optical disc device capable of recording or reproducing a signal with respect to an optical disc on which a wobbling track is formed,
Head means for supporting an objective lens for data writing or reading with respect to the optical disc, and for performing laser irradiation and detection of reflected light using the objective lens as an output end;
Transfer means capable of transferring the head means in the tracking direction;
Measuring means for sequentially measuring a seek transfer speed when the head means is transferred in the tracking direction by a transfer operation of the transfer means, based on a tracking error signal generated from the reflected light detected by the head means; ,
Averaging means for averaging the information on the seek transfer speed measured by the measuring means;
Control means for controlling the seek transfer speed of the head means by controlling the transfer means based on at least information on the seek transfer speed averaged by the averaging means;
An optical disc apparatus comprising: The control means includes
Seek moving speed of the head means, it performs determination of whether faster than the predetermined speed,
When it is determined that the seek transfer speed is faster than the predetermined speed, the transfer means is controlled based on information on the seek transfer speed averaged by the averaging means,
The seek moving speed is, if it is determined that not faster than the predetermined speed, based on the seek moving speed of the information from the measuring means, that controls the transfer means,
The optical disc apparatus according to claim 1, wherein: Recording or reproduction of a signal to or from an optical disc on which a wobbling track is formed is supported, and an objective lens for writing or reading data to or from the optical disc is supported, and laser irradiation with the objective lens as an output end and A seek speed control method in an optical disc apparatus, comprising: head means for detecting the reflected light; and transport means capable of transporting the head means in a tracking direction.
Measurement procedure for sequentially measuring the seek transfer speed when the head means is transferred in the tracking direction by the transfer operation of the transfer means based on the tracking error signal generated from the reflected light detected by the head means When,
An averaging procedure for averaging information on the seek transfer speed measured by the measurement procedure,
A control procedure for controlling the seek transfer speed of the head means by controlling the transfer means based on at least information on the seek transfer speed averaged by the averaging procedure;
And a seek speed control method.

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