JP3607014B2 - Tracking method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tracking method and apparatus for tracking two light beams to a group and a land, respectively, using an optical recording medium whose side walls of a tracking groove meander.
[0002]
[Prior art]
Conventionally, in order to perform tracking, a method for recording address information or recording rotation control information by meandering a groove on an optical disk or meandering only one side wall of the groove is known. It has been.
[0003]
For example, Japanese Patent Laid-Open No. 5-314538 discloses an optical disc that records address information by meandering only one of the grooves. An optical disc has also been developed in which address information is recorded by meandering the side walls on both sides of the groove. In these examples, the tracking servo system is not affected by the meandering frequency by setting the meandering frequency to be higher than the tracking frequency of the tracking servo system during reproduction.
[0004]
Further, as a method for tracking the groove or land as described above, there is a so-called push-pull method disclosed in Japanese Patent Publication No. 55-26529.
[0005]
When the push-pull method is applied to the optical disk having the meandering groove, the obtained tracking error detection signal is output in a form including the meandering frequency. From this tracking error detection signal, for example, only a meander frequency component is extracted by using a band pass filter or the like, and address information is reproduced or rotation control is performed.
[0006]
[Problems to be solved by the invention]
However, in the push-pull method, the light beam irradiation position is controlled by using a photodetector divided into two in the track traveling direction so that the difference in signal level obtained from the left and right photodetectors becomes zero, and tracking is performed. However, for example, if the deviation from the neutral position of the objective lens or the tilt of the disk occurs, the zero level will be shifted. Therefore, even if the signal level difference is controlled to be zero, tracking is performed. However, there is a problem in that tracking is performed in a track offset state in which the light beam cannot be eliminated and the light beam is DC-shifted from the center of the track.
[0007]
If the light beam deviates from the center of the recording mark due to this track offset, an error in the reproduction data occurs. Therefore, a method of removing the track offset in the push-pull method has been desired.
[0008]
For example, as a method of eliminating the optical axis deviation, a method of moving the entire optical system as integral as possible by feeding back the amount of movement of the objective lens to the other optical system, or a method of moving the objective lens and the beam splitter integrally However, in this case, since the weight of the portion that moves at high speed increases, the power consumption increases and the access speed decreases.
[0009]
There is also a method of detecting the amount of movement of the objective lens and canceling the signal for the offset predicted based on this amount of movement. In this case, the optical axis deviation actually occurring in the optical system is eliminated. It is not a fundamental solution.
[0010]
The above is disclosed in detail in, for example, P85 to P91 of “Optical Disc Technology” (Radio Technology Co., Ltd.).
[0011]
The object of the present invention is toOne ofIt is an object of the present invention to provide a tracking method and apparatus for removing a track offset generated when tracking is performed by applying a push-pull method to an optical recording medium having meandering side walls.
[0012]
[Means for Solving the Problems]
The tracking method of the present inventionA track is provided on both the groove and the land, and when an optical recording medium in which one of the side walls shared by the groove and the land is formed in a meandering shape, the light beam for scanning the track is tracked. A first light beam is scanned on the groove without deviation, and the second light beam is scanned on the land without deviation. Relative relationship between the first amplitude value of the first meandering signal obtained by scanning the light beam and the second amplitude value of the second meandering signal obtained by scanning the land with the second light beam. Therefore, the irradiation positions of the first light beam and the second light beam are controlled so that the first light beam and the second light beam are respectively controlled during tracking. A clock for generating a first clock synchronized with one of the first meandering signal and the second meandering signal and irradiating the groove and land sharing the meandering side wall. A generating step, a delay step of delaying a phase difference between the first meandering signal and the second meandering signal and outputting a second clock synchronized with the other meandering signal, the first clock and the second clock A / D conversion step of sampling the corresponding meandering signal based on the clock and converting each meandering signal into a digital value.It is a feature.
[0013]
According to the above configuration, the first meander signal is obtained by tracking the first light beam to the groove, and at the same time, the second meander signal is obtained by tracking the land with the second light beam. At this time, for example, when the first light beam is tracked from the side of the meandering side wall in the groove, the first meandering signal obtained by the first light beam is applied to the desired position of the first light beam. The first amplitude value is larger than the desired first amplitude value because it is greatly affected by the meandering side wall.
[0014]
On the other hand, if the positional relationship between the second light beam and the first light beam is fixed, the second meandering signal obtained by the second light beam is tracked from the side wall side that does not meander. It will be. Therefore, since the influence from the meandering side wall becomes smaller than in the case where the second light beam is irradiated at a desired position, the second amplitude value becomes smaller than the desired second amplitude value.
[0015]
Therefore, the relative relationship between the first amplitude value and the second amplitude value (for example, the first amplitude value and the first amplitude value) when the first and second light beams are tracing on the center line in the tracking direction of the groove and land, respectively. If the irradiation positions of the first and second light beams are controlled so that the two amplitude values are equal, tracking is performed so that the center line in the tracking direction of the grooves and lands coincides with the center of the light beam. Since the position is corrected, tracking can be performed correctly.
[0016]
The tracking device of the present inventionTracks are provided for both the grooves and lands, and the optical beam is scanned when the tracks are scanned on an optical recording medium in which one of the side walls shared by the grooves and lands is formed in a meandering shape. And a first meander by causing the groove to track the first light beam, and an optical head including first and second light sources that respectively emit the first and second light beams. First signal detecting means for outputting a signal; second signal detecting means for outputting a second meandering signal by causing the land to track the second light beam; and amplitude detecting means for detecting the amplitude value of the meandering signal; Comparing means and control means for performing tracking are provided, and the control means includes a first amplitude value of the first meandering signal obtained by the amplitude detecting means, and The relative relationship obtained by comparing the second amplitude value of the two meandering signals with the comparison means is that when the first light beam and the second light beam are scanned on the groove and land tracks without deviation, respectively. A tracking signal is output in a direction coinciding with the relative relationship between the first amplitude value and the second amplitude value, and the control means performs tracking of the optical head based on the tracking signal. Sometimes, the first light beam and the second light beam are respectively designed to irradiate the groove and land sharing the meandering side wall, and one of the first meander signal and the second meander signal. Clock generating means for generating a first clock synchronized with one of the preceding meandering signals, and the first clock for delaying the phase difference between the first and second meandering signals. A delay means for outputting a second clock synchronized with the meandering signal and A / D conversion for sampling the meandering signal corresponding to the first clock and the second clock and converting each meandering signal into a digital value. Means are providedIt is characterized by that.
[0017]
According to the above configuration, the first meandering signal is output by the first signal detecting means by the first light beam that tracks the groove of the optical recording medium, and is input to the amplitude detecting means. The amplitude detection means detects the first amplitude value of the first meander signal generated in the first meander signal, and the value is input to the comparison means. Further, the second meandering signal is outputted by the second signal detecting means by the second light beam tracking the land, and inputted to the amplitude detecting means. The amplitude detection means detects the second amplitude value of the second meander signal generated in the second meander signal and inputs it to the comparison means.
[0018]
The comparison means compares the first amplitude value with the second amplitude value, and shows that the first light beam and the second light beam are scanned on the groove and land tracks without deviation. When the relative relationship between the first amplitude value and the second amplitude value is different (for example, the first amplitude value and the second amplitude value are equal), a tracking signal is output so as to match the relative relationship, The control means corrects the first or second meandering signal based on the tracking signal. As a result, the center lines in the tracking direction of the grooves and lands are corrected so as to coincide with the centers of the first and second light beams, respectively, so that tracking can be performed correctly.
[0019]
As the first and second meandering signals, a so-called tracking error signal in the push-pull method or a total signal may be used.
[0020]
Also,According to the above configuration, since the two light beams are applied to the groove and the land sharing the meandering side wall, the frequency of the meander signal obtained from the groove matches the frequency of the meander signal obtained from the land. Accurate tracking can be done.
[0021]
Also,According to the above configuration, since the two light beams are respectively irradiated on the groove and the land sharing the meandering side wall, the frequency of the meandering signal obtained from the groove matches the frequency of the meandering signal obtained from the land. Therefore, by adjusting the timing at which the meandering amplitude is detected by the delay means, the second amplitude value of the second meandering signal corresponding to the same position as the meandering side wall where the first meandering signal is detected is sampled. A clock is obtained. That is, since the clock generation means for generating the clock from the second meandering signal is not necessary, the circuit configuration can be simplified.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
[0023]
First, the optical recording medium applied to the tracking device of the present embodiment and the concept of tracking in the tracking device will be described.
[0024]
As shown in FIGS. 1A and 1B, the optical recording medium is composed of a groove 1 and lands 2 formed between the grooves 1 and 1 by side walls 1a and 1b constituting the groove 1. In addition, a high density is realized by forming a track 3 a for recording information in both the groove 1 and the land 2. And only one side wall 1a among the side walls shared between the groove 1 and the land 2 meanders. Thus, for example, spot α that traces groove 1 during playback.₁Spot α that traces land 2₂In the read signal obtained from the light beam reflected at, a recording information signal read from the track 3a and a signal component (hereinafter referred to as a meander signal) obtained by meandering of the side wall 1a are superimposed.
[0025]
Further, the meandering signal includes a rotation synchronization signal and an address information signal, and only the meandering signal is extracted from the read signal by a filter. Based on the obtained rotation synchronization signal and address information signal, an optical recording medium is recorded. It is possible to arbitrarily access the recorded information. In this embodiment, the push-pull method is applied to the recording information signal extracted from the read signal to obtain a track error signal, and basic tracking control is performed. The grooves 1 and lands 2 are formed on an optical recording medium such as an optical disk, an optical card, and an optical tape. FIGS. 1A and 1B show partial grooves 1 and lands 2. Although shown, it is needless to say that many grooves 1 and lands 2 are actually arranged in the same direction in the direction perpendicular to the tracks 3a.
[0026]
In the above, as shown in FIG.₁Center and spot α₂The position of the semiconductor laser that emits the light beam is adjusted in advance so that the distance from the center of the laser beam coincides with the track pitch between the groove 1 and the land 2.₁And spot α₂As can be seen from the positions, when tracking control of one light beam is performed, tracking control of the other light beam is also performed simultaneously.
[0027]
So, first, spot α₁Consider a case in which tracking is performed with a deviation from the center of the groove 1 toward the land 2 sharing the side wall 1a.
[0028]
At this time, spot α that traces groove 1₁Is closer to the side wall 1a, so the spot α₁In the meandering signal obtained from the above, the influence from the side wall 1a becomes large, while the spot α tracing the land 2₂Is away from the side wall 1a, so that the spot α₂In the meandering signal obtained from the above, the influence from the side wall 1a is reduced. Accordingly, as shown in FIGS. 1B and 1C, the spot α₁The meander signal E obtained from the light beam reflected by (solid line)₁Amplitude value V₁(First amplitude value) is the spot α₁Serpentine signal E when (dotted line) traces center of groove 1₁'Reference amplitude value V₁It becomes larger than ′, and spot α₂The meander signal E obtained from the light beam reflected by (solid line)₂Amplitude value V₂(Second amplitude value) is the spot α₂Meandering signal E when (dotted line) traces center of land 2₂'Reference amplitude value V₂It becomes smaller than ′.
[0029]
Conversely, spot α₂When tracking is performed with a deviation from the center of the land 2 in the direction of the groove 1 sharing the meandering side wall 1a, the side wall 1a has a meandering signal E.₁Influence on the meandering signal E₂The amplitude value V₁Is the reference amplitude value V₁The amplitude value V becomes smaller than₂Is the reference amplitude value V₂It turns out that it becomes larger than ′.
[0030]
The meander signal E₁, E₂Since the meandering frequency band is set so as not to overlap the tracking servo band, the tracking does not follow the meandering. And the meander signal E₁, E₂Each amplitude value V₁, V₂Each spot α₁, Α₂Can be detected. However, in the above, the reference amplitude value V₁'= V₂'. That is, the amplitude value V₁= V₂When the spot α₁, Α₂Are set to trace the centers of the groove 1 and the land 2, respectively.
[0031]
Therefore, the amplitude value V₁And amplitude value V₂If the tracking control signal of the optical head is corrected so as to be equal to each other, the light beam A₁, A₂It is possible to eliminate the direct current offset in.
[0032]
Next, the tracking device according to the present embodiment will be described. In the tracking device of the present embodiment, the adjacent laser beams and lands on the optical recording medium are individually and simultaneously irradiated with the light beams by the two laser semiconductors, and the read signals from the reflected light beams are compared. Tracking information is obtained.
[0033]
Hereinafter, the configuration of the tracking device will be described assuming that an optical disk is used as the optical recording medium.
[0034]
As shown in FIG. 2, the tracking device 10 according to the present embodiment traces on the groove, and the spot α₁Light beam A forming (FIG. 1 (b))₁Trace over the land and above spot α₂Light beam A forming (FIG. 1 (b))₂The two light beams are emitted and also reflected by the grooves and lands on the optical disc 3, respectively.₁, B₂, And the detection signal C₁, C₂, D₁, D₂Is provided.
[0035]
As shown in FIG. 3, the optical head 4 includes semiconductor lasers 11a and 11b, a beam splitter 12, an objective lens 13, an objective lens actuator 14, and two-divided photodetectors 15a and 15b, and is emitted from the semiconductor laser 11a. Light beam A₁Is transmitted through the beam splitter 12 and focused on the groove on the optical disk 3 by the objective lens 13, and the optical beam 3 contains the information signal B.₁As reflected. This light beam B₁Is reflected by the beam splitter 12, guided to the two-divided photodetector 15a, and detected signal C by the two-divided photodetector 15a.₁, D₁Is converted to Similarly, the light beam A emitted from the semiconductor laser 11b.₂Is transmitted through the beam splitter 12 and condensed on the land on the optical disk 3 by the objective lens 13, and the optical beam 3 containing the information signal is transmitted by the optical disk 3.₂As reflected. Light beam B₂Is reflected by the beam splitter 12, guided to the two-divided photodetector 15b, and detected signal C by the two-divided photodetector 15b.₂, D₂Is converted to
[0036]
Further, the description of the tracking device 10 will be continued.
[0037]
In FIG. 2, the detection signal C detected by the optical head 4 as described above.₁, D₁, C₂, D₂Is provided to the tracking correction device 5a, and the tracking correction device 5a₁, D₁, C₂, D₂Based on the above, the tracking position correction data signal G is output to the optical head 4. Further, the linear motor 6 that drives the optical head 4 in the radial direction, the access device 7 that outputs a drive signal H to the linear motor 6, and the tracking operation command I is output to the tracking correction device 5 a. Is provided with a control unit 8 for outputting an access signal J.
[0038]
Although not shown, tracking control information obtained based on the push-pull method is also input to the optical head 4 and the linear motor 6, and the spot α₁, Α₂This position is finally determined by the tracking control information and the correction data signal G. However, as described in the prior art, the push-pull method is a general technique and will not be described again.
[0039]
In the above, the light beam A₁And light beam A₂Since the feed accuracy of the linear motor 6 is lower than the control accuracy of the objective lens on the optical head 4 when the optical head 4 is moved so as to irradiate the target groove and land on the optical disc 3, respectively. It is necessary to shift the objective lens by that amount so that accurate tracking is performed. This is a cause of the direct current deviation of tracking, but this deviation is corrected by the tracking device 10 of the present embodiment. Can do.
[0040]
The above correction operation will be described as follows based on the flowchart shown in FIG.
[0041]
When the groove tracking control is started, first, the light beam A₁The groove is tracked by the meandering signal E₁Is output (S1) and the meander signal E₁Meander amplitude value V included in each₁Is detected (S2). At the same time, light beam A₂Tracking of the land by the meandering signal E₂Is output (S3) and the meander signal E₂Meander amplitude value V included in each₂Is detected (S4).
[0042]
In S5, the amplitude value V₁And amplitude value V₂As a difference, a correction signal K is obtained. If this correction signal K is not 0, it means that the tracking is shifted, so that the meandering signal E is based on the correction signal K.₁And a correction data signal G is output (S7). Next, the process proceeds to S8 to determine whether or not the tracking control is finished. If it is finished, the tracking correction is finished. If the tracking control is finished, the process returns to S1 and S3 again, and the correction data signal Repeat generation of G. On the other hand, if the correction signal K is 0 in S6, it means that the tracking is correct, so the process proceeds to S8, and the rest is as described above.
[0043]
As described above, the amplitude value V₁And amplitude value V₂Meander signal E if₁A correction signal K is added to the amplitude value V₁And amplitude value V₂If is equal, keep it as it is. Thus, the correction operation is repeated until the amplitude values of the meandering signals at the groove and the land become equal, and the light beam A₁, A₂The tracking position is corrected to the center of the groove and land, respectively, and correct tracking becomes possible.
[0044]
Further, as described above, the light beam A₁And light beam A₂Is adjusted to coincide with the track pitch, so that the light beam A₂Similarly, tracking control for the land 2 can be performed while correcting the track offset.
[0045]
The tracking device 10 can also correct an offset that occurs when the optical disk 3 is tilted.
[0046]
Next, the configuration and operation of the tracking correction device 5a will be briefly described.
[0047]
As shown in FIG. 5, the tracking correction device 5a is provided with four differential amplifiers 21 to 24 and envelope detectors 25 and 26. As the envelope detectors 25 and 26, for example, a peak hold circuit can be used.
[0048]
Detection signal C input to the tracking correction device 5a₁, D₁, C₂, D₂Among them, the detection signal C detected by the two-divided photodetector 15a₁, D₁Are input to the plus side and the minus side of the differential amplifier 21, respectively, and then the meander signal E is filtered by a filter (not shown).₁Is output only. On the other hand, the detection signal C detected by the two-divided photodetector 15b.₂, D₂Are inputted to the plus side and the minus side of the differential amplifier 22 respectively, and then the meander signal E is filtered by a filter (not shown).₂Is output only. This meander signal E₁Is input to the envelope detector 25, the difference between the peak value and the bottom value of the meander is detected, and the amplitude value V of the meander is detected.₁Similarly, the meander signal E₂Amplitude value V₂Is obtained by the envelope detector 26.
[0049]
The amplitude value V₁And amplitude value V₂Are input to the differential amplifier 23 as a comparison means and compared, and the amplitude value V₁And amplitude value V₂The correction signal K is output so that the difference between and is zero.
[0050]
The positive side of the differential amplifier 24 has an output from the differential amplifier 21, that is, a meander signal E₁Is input, the correction signal K is input to the minus side, and the differential amplifier 24 receives the meander signal E.₁Based on the correction signal K, the correction data signal G is output. In the above description, when there is no tracking deviation, the correction signal K becomes zero, so that the meander signal E₁Is amplified as it is and output as the correction data signal G.
[0051]
The correction data signal G is used to feed back the spot position on the optical disk and correct the actuator drive signal of an objective lens (not shown), thereby correcting the track offset. As a result, the light beam A₁It becomes possible to perform accurate tracking control to the groove. Even if the correction signal K is used as it is for the tracking control in place of the correction data signal G, it is possible to perform tracking without causing an offset similarly.
[0052]
Further, the tracking correction device 5a described above may be replaced with a tracking correction device 5b shown in FIG. The tracking correction device 5b shown in FIG. 6 includes differential amplifiers 21, 23, 24, envelope detectors 27, 28, and adders 29a, 29b. The detection signal output from the two-divided photodetector 15a. C₁, D₁Is input to the adder 29a and the meander signal T for correcting tracking through a filter (not shown).₁Is output, while the detection signal C output from the two-divided photodetector 15b₂, D₂Is input to the adder 29b and the meander signal T for correcting tracking through a filter (not shown).₂Is output. And meander signal T₁And meander signal T₂Are input to the envelope detectors 25 and 26, respectively, and the amplitude value v₁, V₂And the amplitude value v is obtained by the difference amplifier 23.₁, V₂From this, the correction signal K ′ is obtained.
[0053]
That is,Tracking correction device 5aThen, the meandering signal obtained by taking the difference is obtained by adding in the tracking correction device 5b. However, even in this case, when tracking is completed, the amplitude value output from the adder 29a matches the amplitude value output from the adder 29b, and the correction signal K ′ from the differential amplifier 23 becomes zero. That is, the tracking control may be corrected so that the correction signal K ′ becomes zero. Similarly to the above, even if the correction signal K ′ is used as it is for the tracking control in place of the correction data signal G, tracking without generating an offset can be performed.
[0054]
In addition, as shown in FIG.₁, Α₂Even if the groove 1 and the land 2 to be traced face the meandering side wall and share the side wall 1b formed parallel to the trace direction, the amplitude value V₁And amplitude value V₂However, for example, when the CLV method is adopted for a disk-shaped optical recording medium, each track (in the case of the present optical recording medium) is detected. Are different for each side wall 1a), and if the rotation speed is the same, the meandering frequency is shifted between the outer peripheral side and the inner peripheral side, so that it becomes impossible to detect the meandering signal. . Even in the case of the CAV method, there is a problem that accurate tracking becomes difficult if there is a slight deviation in the amplitude of the meandering of the two side walls.
[0055]
Therefore, when the two light beams shown in FIG. 1B irradiate the groove 1 and the land 2 sharing the meandering side wall 1a, it is possible to cope with the CLV system and at the same time, tracking is easy. It can be said that it is preferable in that it can be performed.
[0056]
In the tracking device 10 shown in FIG. 2, the tracking correction device 5a may be replaced with a tracking correction device 5c shown in FIG.
[0057]
As shown in FIG. 8, the tracking correction device 5c includes A / D converters 30 and 31, comparators 32 and 33, PLL (Phase Locked Loop) circuits 34 and 35 as first and second amplitude detection means, and a comparison. A CPU 36, a D / A converter 37, and a differential amplifier 38 are provided as means.
[0058]
The output terminals of the differential amplifiers 21 and 22 are connected to the input sides of the A / D converters 30 and 31, respectively, the outputs of the A / D converters 30 and 31 are input to the CPU 36, and the output of the CPU 36 is the D / A converter. 37. The output terminal of the differential amplifier 21 is also connected to the plus terminal of the comparator 32, and a voltage having a predetermined threshold is applied to the minus terminal of the comparator 32. The output terminal of the comparator 32 is connected to the input side of the PLL circuit 34, and the output of the PLL circuit 34 is input to the A / D converter 30. Similarly, the output terminal of the differential amplitude device 22 is connected to the plus terminal of the comparator 33, and a voltage having a predetermined threshold is applied to the minus terminal of the comparator 33. The output terminal of the comparator 33 is connected to the PLL circuit 35 on the input side, and the output of the PLL circuit 35 is input to the A / D converter 31. Further, the output of the differential amplifier 21 is connected to the plus side of the differential amplifier 38 and the output of the D / A converter 37 is connected to the minus side.
[0059]
In the above configuration, the A / D converter 30 includes the meander signal E₁The amplitude value V included in₁The timing clock L described later₁The digital amplitude value M₁And input to the CPU 36. Similarly, the A / D converter 31 generates a meander signal E₂The amplitude value V included in₂The timing clock L described later₂The digital amplitude value M₂And input to the CPU 36. In the CPU 36, the digital amplitude value M₁And digital amplitude value M₂And the amplitude value V₁And amplitude value V₂And a correction value N is obtained. The correction value N is sent to the D / A converter 37 where the correction signal P converted into an analog value is input to the differential amplifier 38.
[0060]
As described above, the meander signal E₁And the correction data signal G can be obtained. Then, by feeding back the correction data signal G to an actuator that drives an objective lens (not shown), tracking servo can be performed. In addition, even when the correction signal P is used as it is for tracking control instead of the correction data signal G in the above, it is possible to perform tracking without causing an offset similarly.
[0061]
The timing clock L₁Is a meander signal E given to the comparator 32₁Binarized signal Q obtained by comparing the threshold voltage with₁Is converted by the PLL circuit 34 to thereby meander signal E₁Obtained as a signal synchronized with the timing clock L₂Similarly, the binarized signal Q obtained by the comparator 33₂Is converted by the PLL circuit 35 and the meander signal E₂It is obtained as a signal synchronized with the.
[0062]
Here, the timing clock L₁And digital amplitude value M₁A method for obtaining the above will be described with reference to FIG. Timing clock L₂And digital amplitude value M₂In this case, the timing clock L can be considered similarly.₁And digital amplitude value M₁Only will be described.
[0063]
As shown in FIG. 9, in the comparator 32 (FIG. 8), the meander signal E which is an analog value.₁And the threshold voltage, the binarized signal Q binarized as the magnitude information₁Is obtained. This binary signal Q₁Is input to the PLL circuit 34, whereby the binary signal Q₁Timing clock L synchronized with₁Is obtained. Therefore, in the A / D converter 30, the timing clock L₁Meander signal E at the rise of₁If this value is converted into a digital value, the peak value and the bottom value of the meandering signal can be obtained. As a result, the meander signal E₁Digital amplitude value M₁Can be obtained. Similarly, the digital amplitude value M₂Can be obtained.
[0064]
When using the tracking correction device 5c, unlike using the tracking correction device 5a,Comparison of amplitude value with digital amplitude value M₁, M₂In this case, there are the following merits.
[0065]
For example, as shown in FIG. 9, when there is a defect or the like on the disk, the meander signal E₁Sharp noises called spikes indicated above by reference X may occur.In FIG.When the envelope detectors 25 and 26 shown are constituted by analog peak hold circuits, the peak of the spike X is recognized as a peak value and output. Therefore, the measured amplitude value V₁Will greatly deviate from the actual amplitude value, and the correction value for tracking is apologized and the offset cannot be corrected correctly, and correct tracking cannot be performed.
[0066]
But,Using tracking correction device 5cTiming clock L like tracking device 10₁When the amplitude value is sampled based on the above, since the possibility of sampling at the timing when the spike X occurs is very low, the correction value is not easily shifted by the spike X, and more accurate tracking can be performed.
[0067]
Further, in the tracking device 10 shown in FIG. 2, the tracking correction device 5a may be replaced with the tracking correction device 5d shown in FIG.This tracking correction device 5dThe figureThe tracking correction device 5c shown in FIG. 8 is further simplified.
[0068]
thisIn the tracking correction device 5d, as shown in FIG. 10, the first and second amplitude detection means are shared by a single A / D converter 30, a comparator 32, and a PLL circuit 34. Instead, the meander signal E₁, E₂Switch circuit 41 for switching between and the first clock K₁Delay the second clock K₂And a switch circuit 43 for switching between the two clocks.
[0069]
In the figure, the outputs of the differential amplifiers 21 and 22 are input to the switch circuit 41 and output to the A / D converter 30 while switching based on a switching command R from the CPU 36. The output of the A / D converter 30 is input to the CPU 36, and the output of the CPU 36 is input to the D / A converter 37. The output of the differential amplifier 21 is connected to the plus terminal of the comparator 32, while a predetermined threshold voltage is applied to the minus terminal. The output terminal of the comparator 32 is connected to the input side of the PLL circuit 34, and the output of the PLL circuit 34 is input to one terminal of the switch circuit 43 and the delay circuit 42. Further, the output of the delay circuit 42 is input to the other terminal of the switch circuit 43, switched based on a switching command R from the CPU 36, and output to the A / D converter 30.
[0070]
In the above configuration, first, when the switching command R of the CPU 36 is at a high level, the meander signal E₁Is output to the A / D converter 30 and a timing clock L described later.₁To meander amplitude value V₁Is the digital amplitude value M₁And is input to the CPU 36. When the switching command R is at a low level, the meander signal E₂Is output to the A / D converter 30 and a timing clock L described later.₂To meander amplitude value V₂Is the digital amplitude value M₂And is input to the CPU 36. In the CPU 36, the digital amplitude value M₁And digital amplitude value M₂And the amplitude value V₁And amplitude value V₂And a correction value N is obtained. The correction value N is sent to the D / A converter 37, where the correction signal P converted into an analog value is input to the differential amplitude device 38.
[0071]
As described above, the meander signal E₁And the correction data signal G can be obtained. Then, tracking servo can be performed by feeding back the correction data signal G to an actuator that drives an objective lens (not shown). In addition, even when the correction signal P is used as it is for the tracking control in place of the correction data signal G in the above, tracking without occurrence of an offset can be similarly performed.
[0072]
The timing clock L₁Meander signal E given to the comparator 32 by switching of the switch circuit 41.₁Binarized signal Q obtained by comparing the threshold voltage with₁Is converted by the PLL circuit 34 to thereby meander signal E₁It is obtained as a signal synchronized with the. In addition, the spot α₁And spot α₂The interval between them is constant, that is, the phase difference between them is constant in the case of the CLV system, and in the CAV system, it is proportional to the rotation radius.₂Timing clock L₂Is the timing clock L₁For the above relationship, ie, meander signal E₁And meander signal E₂Are obtained by delaying so that the positions of the amplitudes when the same meandering part is detected coincide with each other.
[0073]
Here, the timing clock L₁And timing clock L₂In relation to the digital amplitude value M₁, M₂A method for obtaining the above will be described with reference to FIGS.
[0074]
First, as shown in FIG. 11, in the comparator 32 (FIG. 10), the meander signal E which is an analog value.₁(FIG. 11 (a)) and the threshold voltage, by comparing the threshold voltage, the binarized signal Q binarized as the magnitude information₁(FIG. 11B) is obtained. This binary signal Q₁Is input to the PLL circuit 34, whereby the binary signal Q₁Timing clock L synchronized with₁(FIG. 11C) is obtained.
[0075]
By the way, as described above, the spot α in FIG.₁And spot α₂Means that the spot α₁And spot α₂Meander signal E obtained from₁And meander signal E₂There is a phase difference between the two, but since both are meandering signals obtained from the same meandering side wall, the periods are the same.₁And spot α₂Timing clock L for a time dt corresponding to the distance between₁Delays the timing clock L₂Will be obtained. Then, as shown in FIGS. 11D to 11F, the meandering signal E flowing through the A / D converter 30 in response to the switching of the switching signal R between the high level and the low level.₁, E₂And timing clock L₁, L₂And the timing clock L₁Meander signal E at the rise of₁Is sampled, the meander signal E₁Peak value and bottom value are obtained, and the timing clock L₂Meander signal E at the rise of₂Is sampled, the meander signal E₂The peak value and the bottom value are obtained. Based on the peak value and the bottom value, the meander signal E₁, E₂Digital amplitude value M₁, M₂Can be obtained.
[0076]
A tracking correction device 5d is provided.In the tracking device 10,When using the tracking correction device 5cUnlike meander signal E₁And meander signal E₂And the fact that there is a phase difference and the timing clock obtained from one meander signal by the delay circuit is used in common, and the configuration for obtaining the timing clock is halved. At the same time, meander signal E₁And meander signal E₂By utilizing the fact that the sampling timing of the A / D converters is different, the number of A / D converters is halved by using the A / D converters 30 in a time-division manner by the switch circuits 41 and 43. Since the tracking device 10 can be manufactured at a lower cost.
[0077]
【The invention's effect】
The tracking method of the present inventionA track is provided on both the groove and the land, and when the optical recording medium in which one of the side walls shared by the groove and the land is formed in a meandering shape, the light beam for scanning the track is tracked. A first light beam is scanned on the groove without deviation, and the second light beam is scanned on the land without deviation. Relative relationship between the first amplitude value of the first meandering signal obtained by scanning the light beam and the second amplitude value of the second meandering signal obtained by scanning the land with the second light beam. Therefore, the irradiation positions of the first light beam and the second light beam are controlled so that the first light beam and the second light beam are respectively controlled during tracking. A clock for generating a first clock synchronized with either one of the first meandering signal and the second meandering signal while irradiating the groove and land sharing the meandering side wall. A generating step, a delay step of delaying a phase difference between the first meandering signal and the second meandering signal and outputting a second clock synchronized with the other meandering signal, and the first clock and the second clock. And A / D conversion step of sampling each corresponding meandering signal and converting each meandering signal into a digital value.
[0078]
As in the above configuration, the relative relationship between the first amplitude value and the second amplitude value is maintained when the first and second light beams are traced on the center line in the tracking direction of the groove and land, respectively. In addition, since the irradiation positions of the first and second light beams are controlled, the tracking position can be correctly corrected, and the center line of the tracking direction of the grooves and lands can be matched with the center of the light beam. There is an effect that can be done.
[0079]
In addition, what is necessary is just to use what is called a tracking error signal in a push pull method, and a total signal as said 1st and 2nd meander signal.
[0080]
The tracking device of the present inventionTracks are provided for both the grooves and lands, and the optical beam is scanned when the tracks are scanned on an optical recording medium in which one of the side walls shared by the grooves and lands is formed in a meandering shape. And a first meander by causing the groove to track the first light beam, and an optical head including first and second light sources that respectively emit the first and second light beams. First signal detecting means for outputting a signal; second signal detecting means for outputting a second meandering signal by causing the land to track the second light beam; and amplitude detecting means for detecting the amplitude value of the meandering signal; Comparing means and control means for performing tracking are provided, and the control means includes a first amplitude value of the first meandering signal obtained by the amplitude detecting means, The relative relationship obtained by comparing the second amplitude value of the two meandering signals with the comparison means is that when the first light beam and the second light beam are scanned on the groove and land tracks without deviation, respectively. A tracking signal is output in a direction coinciding with the relative relationship between the first amplitude value and the second amplitude value, and the control means performs tracking of the optical head based on the tracking signal. Sometimes, the first light beam and the second light beam are respectively designed to irradiate the groove and land sharing the meandering side wall, and one of the first meander signal and the second meander signal. Clock generating means for generating a first clock synchronized with one of the preceding meandering signals, and the first clock for delaying the phase difference between the first and second meandering signals. A delay means for outputting a second clock synchronized with the meandering signal and A / D conversion for sampling the meandering signal corresponding to the first clock and the second clock and converting each meandering signal into a digital value. Means.
[0081]
As in the above configuration, the result of comparing the amplitude value of the first meandering signal detected by the first signal detecting means and the second amplitude value of the second meandering signal detected by the second signal detecting means by inputting to the comparing means However, the relative relationship between the first amplitude value and the second amplitude value when the first light beam and the second light beam are scanned on the groove and land tracks without deviation (for example, the first light beam and the second light beam). If the amplitude value is different from the second amplitude value), a tracking signal is output so as to match the relative relationship, and the control means corrects the first or second meandering signal based on the tracking signal. As a result, the tracking and the center line in the tracking direction of the land are corrected so as to coincide with the centers of the first and second light beams, respectively.
[0082]
Also,Since the frequency of the meandering signal obtained from the groove matches the frequency of the meandering signal obtained from the land, there is an effect that accurate tracking can be performed.
[0083]
Also,Since the frequency of the meandering signal obtained from the groove matches the frequency of the meandering signal obtained from the land, a clock for detecting the amplitude of the meandering signal by the delay means is used as a phase difference between the first meandering signal and the second meandering signal, In other words, if the delay is made according to the distance between the light beams, a clock for sampling the second amplitude value of the second meandering signal corresponding to the same position as the meandering side wall where the first meandering signal is detected is obtained. be able to. That is, there is no need for a clock generating means for generating the clock from the second meandering signal, so that the circuit configuration can be simplified.
[Brief description of the drawings]
FIG. 1 shows the characteristics of an optical recording medium according to an embodiment of the present invention. FIG. 1 (a) is a partial sectional view of a recording surface, and FIG. 1 (b) is a partial plan view of the recording surface. FIG. 3C is an explanatory diagram showing the amplitude state of the meandering signal obtained when the light beam is irradiated to the groove and the land.
FIG. 2 is a block diagram showing an outline of a tracking device according to an embodiment of the present invention.
3 is a block diagram showing an outline of the optical head in FIG. 2. FIG.
FIG. 4 is a flowchart showing a tracking correction procedure in the present embodiment.
5 is a block diagram showing an example of the configuration of the tracking device shown in FIG.
6 is a block diagram showing another configuration example of the tracking device shown in FIG. 2. FIG.
FIGS. 7A and 7B show an example in which the optical recording medium of FIG. 1 is irradiated with different light beams. FIG. 7A is a partial sectional view of the recording surface, and FIG. 7B is a partial plane of the recording surface. FIG.
[Fig. 8]Tracking correction device that can be provided in the tracking device shown in FIG.FIG.
FIG. 9 is a timing chart of signals related to the tracking device shown in FIG. 8;
FIG. 10Tracking correction device that can be provided in the tracking device shown in FIG.FIG.
11A and 11B show signals related to the tracking device shown in FIG. 10, in which FIG. 11A is a timing chart of a detected meander signal, FIG. 11B is a timing chart of a binarized signal, and FIG. (C) is a timing chart of the timing clock, (d) is a timing chart of the switching signal, and (e) and (f) are timing charts of the meander signal and timing clock flowing through the A / D converter, respectively. It is.
[Explanation of symbols]
1 groove
1a side wall
2 Land
3 Optical disc (optical recording medium)
3a truck
4 Optical head
5a to d Tracking correction device
8 Control unit (control means)
10 Tracking device
11a Semiconductor laser (first light source)
11b Semiconductor laser (second light source)
21. Differential amplifier (first signal detection means)
22 Differential amplifier (second signal detection means)
23 Differential amplifier (comparison means)
25-28 Envelope detector (amplitude detection means)
29a Adder (first signal detection means)
29b Adder (second signal detection means)
30 A / D converter (A / D conversion means)
31 A / D converter (A / D conversion means)
42 Delay circuit (delay means)
A₁  Light beam (first light beam)
A₂  Light beam (second light beam)
E₁  Meander signal (first meander signal)
E₂  Meander signal (second meander signal)
G Correction data signal (tracking signal)
L₁  Timing clock (first clock)
L₂  Timing clock (second clock)
M₁  Digital amplitude value (first amplitude value / digital value)
M₂  Digital amplitude value (second amplitude value / digital value)
T₁  Meander signal (first meander signal)
T₂  Meander signal (second meander signal)
V₁・ V₁  Amplitude value (first amplitude value)
V₂・ V₂  Amplitude value (second amplitude value)

Claims (4)

Tracking with tracks in any of the grooves and lands are provided, hand side wall and the groove and the land is shared, when using an optical recording medium comprising formed in a serpentine shape, a light beam scanning the track A tracking method for
When the first light beam scans on the groove without deviation and the second light beam scans on the land without deviation, the first light beam is obtained by causing the groove to scan with the first light beam. The first amplitude value of the first meandering signal and the second amplitude value of the second meandering signal obtained by causing the land to scan with the second light beam are maintained so that the relative relationship is maintained. The irradiation position of the first light beam and the second light beam is controlled ,
At the time of tracking, the first light beam and the second light beam irradiate the groove and land sharing the meandering side wall, respectively,
A clock generating step for generating a first clock synchronized with one of the preceding meandering signals of the first meandering signal and the second meandering signal;
A delaying step of delaying a phase difference between the first meandering signal and the second meandering signal to output a second clock synchronized with the other meandering signal;
A tracking method comprising: an A / D conversion step of sampling a corresponding meandering signal based on the first clock and the second clock and converting each meandering signal into a digital value . With track is provided to both the groove and the land, the light beam when the hand of the side wall and the groove and the land is shared, the optical recording medium comprising formed in a meandering shape, scanning the tracks A tracking device for tracking,
An optical head having first and second light sources that respectively emit first and second light beams, and first signal detection means for outputting a first meander signal by causing the groove to track the first light beam. A second signal detecting means for outputting a second meander signal by causing the land to track the second light beam, an amplitude detecting means for detecting the amplitude value of the meander signal, a comparing means, and a control means for performing tracking And is provided,
The control means has a relative relationship obtained by comparing the first amplitude value of the first meandering signal obtained by the amplitude detecting means and the second amplitude value of the second meandering signal by the comparing means, and the first light beam and A tracking signal is output in a direction that coincides with the relative relationship between the first amplitude value and the second amplitude value when the second light beam scans the groove and land tracks without deviation, and The control means is adapted to track the optical head based on the tracking signal ,
During tracking, the first light beam and the second light beam are respectively designed to irradiate the groove and land sharing the meandering side wall,
Clock generating means for generating a first clock synchronized with either one of the first meandering signal and the second meandering signal, and the phase of the first meandering signal and the second meandering signal. Delay means for delaying the difference and outputting a second clock synchronized with the other meandering signal, and sampling the corresponding meandering signal based on the first clock and the second clock, and converting each meandering signal into a digital value A tracking device comprising: A / D conversion means for conversion . An optical recording medium is used to scan a groove track in which one side wall meanders with the first light beam, and scan a land track sharing the meandering side wall with the second light beam. A beam tracking method,
An amplitude detection step of detecting an amplitude value of the first meandering signal obtained by the reflected light of the first light beam and an amplitude value of the second meandering signal obtained by the reflected light of the second light beam;
A comparison step for obtaining an amplitude difference which is a difference between two amplitude values obtained in the amplitude detection step;
The irradiation positions of the first and second light beams are controlled so that the amplitude difference matches the amplitude difference obtained when both the first and second light beams are scanned on the track without deviation. Control process,
The amplitude detection process described above
A clock generation step of generating a first clock synchronized with the preceding one of the first and second meandering signals;
Delaying the first clock by the phase difference between the two meandering signals to output a second clock synchronized with the other meandering signal;
A / D conversion step of sampling the corresponding meandering signal based on the first and second clocks and converting each meandering signal into a digital value;
The tracking method characterized by including. An optical recording medium is used to scan a groove track in which one side wall meanders with the first light beam, and scan a land track sharing the meandering side wall with the second light beam. A beam tracking method,
Amplitude detecting means for detecting the amplitude value of the first meandering signal obtained by the reflected light of the first light beam and the amplitude value of the second meandering signal obtained by the reflected light of the second light beam;
A comparison means for obtaining an amplitude difference which is a difference between two amplitude values obtained by the amplitude detection means;
The irradiation positions of the first and second light beams are controlled so that the amplitude difference matches the amplitude difference obtained when both the first and second light beams are scanned on the track without deviation. Control means,
The amplitude detecting means is
Clock generating means for generating a first clock synchronized with the preceding one of the first and second meandering signals;
Delay means for delaying the first clock by a phase difference between both meandering signals to output a second clock synchronized with the other meandering signal;
A / D conversion means for sampling the corresponding meandering signal based on the first and second clocks and converting the amplitude value of each meandering signal into a digital value;
A tracking device comprising:

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