JP4267901B2 - Reproduction method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to reproduction of an information recording medium for recording information such as digital video information at a high density, and more specifically, a technique for reproducing the information from a high density optical disk medium in which information is included in a wobble of a track. About.
[0002]
[Prior art]
In recent years, the density of optical disc media has been increasing. In general, a track groove is formed in advance on a recordable optical disc medium, and information is recorded along the track groove, that is, on the track groove or in an area (land) sandwiched between the track grooves. The track groove is formed by meandering in a sine wave shape, and information is recorded in synchronization with a clock generated based on the meandering cycle. In addition, an address is provided along the track groove in order to record information at a predetermined position on the optical disk recording surface. The configuration of this address will be described below with an example.
[0003]
First, a first example is a technique in which a track groove in which wobbles are formed is intermittently formed locally and can be reproduced as so-called prepits (see Patent Document 1). According to this technique, an address dedicated area and a data dedicated area (for recording information) coexist on the track. The second example is a technique for describing address information (sub-information) by frequency-modulating wobble (see Patent Document 2). According to this technique, the data information is overwritten on the address information. Furthermore, the third example is a technique for forming a pre-pit between a track groove and a track groove adjacent thereto, thereby forming an address (see Patent Document 3).
[0004]
However, when considering higher density in the future, each of the above technologies has its own problems. First, in the configuration according to the first example, the data area is deleted by the amount that secures the address area (so-called overhead), and the recording capacity must be reduced accordingly.
[0005]
Next, for the second example, the groove wobble is primarily intended to generate a clock for recording information, and is preferably formed at a single frequency. This is because if the frequency is a single frequency, a recording clock signal with high accuracy can be generated by simply multiplying the wobble reproduction signal by using a phase locked loop (PLL) or the like. However, when the groove wobble includes a plurality of frequency components, the PLL follow-up band has to be lowered as compared with the case of the single wobble in order to avoid the pseudo lock of the phase lock loop. In this case, the phase lock loop cannot sufficiently follow the jitter caused by the disk motor jitter or the disk eccentricity, and as a result, the jitter may remain in the recording signal. Further, if the recording film formed on the optical disk recording surface is, for example, a phase change film, the S / N ratio of the recording film may decrease as rewriting is repeated. Even if the S / N ratio is reduced, a noise component can be removed using a narrow band-pass filter with a single wobble frequency. However, when the frequency modulation is performed and a plurality of frequencies are included, the band of the filter must be widened accordingly. In this case, noise components are mixed, and jitter is further deteriorated. From the viewpoint that the jitter margin decreases as the recording density increases, such an increase in jitter is not preferable.
[0006]
Next, in the third example, since the prepit naturally affects the adjacent track, it is difficult to make the length of the prepit sufficiently long and the number of the prepits sufficiently large. In particular, when the density is increased, there is a concern that detection errors increase.
[0007]
In view of the above problems, the present applicant has proposed an optical disc medium that gives information by indicating a wobble shape with a steep inner circumferential displacement as "1" and a wobble shape with a steep outer circumferential displacement as "0", and indicating an address. Yes. As one means for detecting the address information of the optical disk medium, there is a method of generating a carrier of, for example, a second harmonic of the wobble frequency, multiplying and integrating the reproduction signal, and determining “1” or “0” by the sign. is there. This is a technique for performing heterodyne detection on a second harmonic contained in a reproduction signal by utilizing the fact that waveforms having different rising or falling slopes are caused by the difference in phase polarity of even harmonics. . The second harmonic for multiplication can be easily generated by generating a clock by multiplying the wobble frequency by, for example, 2N (N is a rational number) using a PLL and dividing the clock by N.
[0008]
[Patent Document 1]
JP-A-6-309672
[Patent Document 2]
Japanese Patent Laid-Open No. 5-189934
[Patent Document 3]
JP 9-326138 A
[0009]
[Problems to be solved by the invention]
However, when a second harmonic reference wave is generated by a clock obtained by multiplying the wobble frequency as described above, the sensitivity of detection by heterodyne detection may be reduced. This is because the wobble itself causes a phase shift due to the interference of the wobble of the adjacent track, and the phase may shift with respect to the second harmonic in the signal to be detected.
[0010]
An object of the present invention is to always reproduce information in an optimal state during heterodyne detection. More specifically, an object of the present invention is to generate a second harmonic carrier signal for heterodyne detection.
[0011]
[Means for Solving the Problems]
  The playback method according to the present invention comprises:FirstA reference wobble block having a wobble shape ofA block mark provided in front of the reference wobble block;Reference wobble blockAfter theProvidedAnd an information wobble block including a plurality of sections, each of the sections being a reference wobble block1st wobble shapeOr the same shape as the reference wobble blockA second wobble shape different from the first wobble shapeHave either oneA reproduction method for reproducing an information recording medium,Detecting the block mark and following the block markReading the reference wobble block; reading the information wobble block; andFor each sectionWobble shape and the first wobble shape of the read reference wobble blockWhether they are the sameComparing the information wobble blockA section ofThe wobble shape isReference wobble blockIf it matches the first wobble shape, the information wobble blockThe one section ofInFirst1 emotionNewsThe information wobble block is judged to be recordedThe one section ofThe wobble shape isReference wobble blockIf it differs from the first wobble shape, the information wobble blockThe one section ofInFirstAccording to the step of judging that the information of 2 is recorded and the result of the judgment,About each sectionThe first informationOrSaid second informationNewsOutputting. This achieves the above object.
[0012]
The first wobble shape is expressed using at least a primary fundamental wave and a second harmonic in a Fourier series, and the second wobble shape is at least a primary fundamental wave and a second harmonic in a Fourier series. And the polarity of the second harmonic may be opposite to the polarity of the second harmonic of the first wobble pattern.
[0013]
The comparing step is obtained by generating a second harmonic carrier having a frequency corresponding to the second harmonic based on the period of the first wobble shape, and reading the reference wobble block. Extracting a second harmonic component from a waveform; and comparing a phase of the second harmonic carrier and a phase of the second harmonic component to detect a phase error. Further, the determining step includes a step of changing the phase of the second harmonic carrier based on the detected phase error, and a second harmonic from the waveform obtained by reading the information wobble block. A step of extracting a component, a step of generating a detection signal by heterodyne detection of the newly extracted second harmonic component and the second harmonic carrier whose phase has been changed, and a sign of the detection signal is correct. If it is determined that the wobble shape of the information wobble block matches the first wobble shape, and the sign of the detection signal is negative, the wobble shape of the information wobble block is the first wobble shape. You may judge that it was different.
[0014]
The phase error may be an average value of accumulated phase errors during the reference wobble block.
[0015]
The comparing step is obtained by generating a second harmonic carrier having a frequency corresponding to the second harmonic based on the period of the first wobble shape, and reading the reference wobble block. Extracting a second harmonic component from a waveform; and comparing a phase of the second harmonic carrier and a phase of the second harmonic component to detect a phase error. The determining step corresponds to the second harmonic based on the step of changing the phase of the second harmonic carrier based on the detected phase error and the period of the first wobble shape. Generating a second harmonic carrier having a frequency, extracting the second harmonic component from a waveform obtained by reading the reference wobble block, the second harmonic component, and the 2 Heterodyne detection of the second harmonic carrier to generate a first detection signal, a step of determining the phase polarity of the second harmonic carrier based on the first detection signal, and 2 based on the determination result Performs one of forward rotation processing and inversion processing of the second harmonic carrier, newly generates a second harmonic carrier, and reads out the information wobble block. A new second harmonic component is extracted from the obtained waveform, and the second detection is performed by heterodyne detection of the newly extracted second harmonic component and the newly generated second harmonic carrier. A step of generating a signal and a step of determining whether or not a wobble shape of the information wobble block matches the first wobble shape according to the sign of the second detection signal may be included.
[0016]
The step of detecting the phase error detects the phase error by comparing the phase of the rising edge and the falling edge of the second harmonic carrier and the phase of the rising edge and the falling edge of the second harmonic component. May be.
[0017]
  A playback device according to the present invention comprises:A reference wobble block having a first wobble shape, a block mark provided before the reference wobble block, and an information wobble block including a plurality of sections provided after the reference wobble block, and each of the sections Is a reproducing apparatus for reproducing an information recording medium having either the same shape as the first wobble shape of the reference wobble block or a second wobble shape different from the first wobble shape of the reference wobble block. Means for detecting the block mark, means for reading the reference wobble block following the block mark, means for reading the information wobble block, wobble shape of each section of the read information wobble block, and reading The first wobble shape of the reference wobble block Means for comparing whether or not they are the same, and if the wobble shape of one section of the information wobble block matches the first wobble shape of the reference wobble block, the one section of the information wobble block Determines that the first information is recorded, and if the wobble shape of the one section of the information wobble block is different from the first wobble shape of the reference wobble block, the information wobble Means for determining that the second information is recorded in the one section of the block; and means for outputting the first information or the second information for each section according to the determination result; Have This achieves the above object.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Before describing embodiments of the present invention, an example of an optical disk medium targeted by the present invention will be described first. In this specification, the same reference numerals are given to elements that perform the same configuration and operation.
[0024]
FIG. 1 is a top view of the information recording medium 3. The information recording medium 3 is an optical disk such as a DVD. A track groove 2 is formed in a spiral shape on the recording surface 1 of the information recording medium 3. In the information recording medium 3, information is recorded along the track groove. Although the track 2 is drawn very large in the drawing, the track pitch of the track 2 is, for example, 0.32 μm.
[0025]
FIG. 2 is a schematic diagram showing the structure of the main part of the track groove 2. The track groove 2 is divided into a plurality of blocks, and a reference wobble block 102 and a sub information wobble block 103 follow with the block mark 101 at the head. The sub information wobble block 103 includes a plurality of unit blocks 104 each having a predetermined length area as one unit.
[0026]
As is apparent from the figure, most of the track groove 2 is wobbled (meandering) periodically. Each unit block 104 constituting the reference wobble block 102 and the sub information wobble block 103 is continuously provided with a wobble shape. Their wobble shape is characterized for each block. Hereinafter, the blocks 101, 102, and 103 will be described in detail.
[0027]
The block mark 101 is also referred to as an identification mark, and serves as an index for specifying the head position of the block. The wobble period of the block mark 101 is shorter than the wobble period of other blocks. Thereby, it can be specified that the region where the short cycle is detected is the block mark 101. Next, the reference wobble block 102 is used as a reference for specifying information (“0” or “1”) represented by the wobble shape of the subsequent unit block 104.
[0028]
The sub information wobble block 103 is formed based on information related to a physical address in the information recording medium 3 (FIG. 1), for example, information obtained by adding scramble, interleave, error correction code, etc. to the address. .
[0029]
The unit block 104 constituting the sub information wobble block 103 uniquely represents 1-bit information of “0” or “1” (hereinafter referred to as “sub information”) according to the wobble shape. In other words, the unit block 104 is given a wobble shape representing the sub information “0” or a wobble shape representing the sub information “1”. The amount of information (number of bits) represented by one sub information wobble block 103 can be adjusted according to the number of unit blocks 104 provided. For example, four unit blocks 104 are provided, and the sub information wobble block 103 can represent 4-bit information. Alternatively, a plurality of unit blocks 104 having the same wobble shape may be provided in succession, and n-bit information may be represented by (n + 1) or more unit blocks 104. According to this configuration, even when the specific unit block 104 cannot be read, the information related to the address described above can be specified.
[0030]
When one sub-information wobble block 103 represents 4-bit information and the information related to the address uses 60 bits as one information processing unit, the block mark 101, the reference wobble block 102, and the sub-wobble block 102 described above are included. Fifteen sets of information wobble blocks 103 may be provided.
[0031]
Next, the wobble shape representing the sub information will be described more specifically. FIG. 2 shows a wobble shape representing the sub information “1” and a wobble shape representing the sub information “0”. As can be understood from the figure, the wobble shape representing the sub information “1” and the wobble shape representing the sub information “0” are both formed in a so-called sawtooth shape. The wobble shape representing the sub information “1” is configured such that the displacement of the information recording medium 3 toward the inner periphery is steep and the displacement toward the outer periphery is gentle. On the other hand, the wobble shape representing the sub information “0” is configured such that the displacement of the information recording medium 3 toward the inner periphery is gentle and the displacement toward the outer periphery is steep. Here, “inward direction” represents the upward direction when the block 101 is the left end in FIG. 2, and “outward direction” represents the opposite direction.
[0032]
Two types of wobble shapes having the above relationship can be formed as follows. That is, one wobble waveform is converted to a primary fundamental wave (sin (ω₀t)) and the nth harmonic (sin (nω₀When expressed as a Fourier series using t)), the other wobble waveform can be formed by inverting the polarity of the even harmonic. “Reversing the polarity of even harmonics” means reversing the sign of the Fourier coefficient of even harmonics, in other words, reversing the polarity of the even harmonics waveform itself, or changing the phase. This means shifting by half a cycle.
[0033]
In this specification, the wobble shape of the reference wobble block 102 is formed in the same shape as the shape of the unit block 104 having the sub information “0”. The reproducing apparatus for the information recording medium 3 to be described later compares the wobble shape of the reference wobble block 102 with the wobble shape of the unit section 104 so that the wobble shape of the unit section 104 is the same shape as the reference wobble. If detected, the unit block 104 is specified to represent the sub information “0”. Similarly, if it is detected that the wobble shape of the unit block 104 is a shape different from the reference wobble (that is, a shape with reversed polarity), the unit block 104 is identified as representing the sub information “1”. In order to perform this processing, the reproducing apparatus is preset to arrange the block mark 101, the reference wobble block 102, and the sub information wobble block 103 in this order on the information recording medium 3.
[0034]
In the above description, the wobble cycle of the block mark 101 has been described to be shorter than the wobble cycle of other blocks. However, for example, the phase may be the same and the phase may be reversed. Or you may make it combine the wobble with a short period, and the wobble which reversed the phase.
[0035]
In the above description, the plurality of unit blocks 104 of the reference wobble block 102 and the sub information wobble block 103 are provided with continuous wobble shapes. However, if the positions in the blocks can be specified, they need to be continuous. There is no.
[0036]
The reference wobble block 102 is provided with one section near the beginning of the track groove 2. For example, it is assumed that the reference wobble block 102 is composed of one unit section having the same length as the unit block 104. A plurality of units may be provided in a block such that the first unit section is a reference wobble and the subsequent four unit sections are sub information wobbles.
[0037]
Hereinafter, an optical disk reproducing apparatus of the present invention will be described with reference to the accompanying drawings. The information recording medium 3 described above is assumed to be an optical disk such as a DVD.
[0038]
(Embodiment 1)
FIG. 3 is a block diagram illustrating a configuration of the detection unit 300 that detects the sub information on the optical disc 3. Since the detection unit 300 is mounted on the optical disc playback apparatus, the configuration shown in FIG. 3 is a part of the optical disc playback apparatus. Of the configuration of the optical disc playback apparatus, the part necessary for the processing after detecting the sub information by the detection unit 300 is not directly related to the present invention. Therefore, the entire optical disk playback device is not shown.
[0039]
The detection unit 300 of the optical disk reproducing apparatus includes an optical head 301, a push-pull signal generation circuit 302, a bandpass filter 303, a clock generation circuit 304, a block mark detection circuit 305, a timing generation circuit 306, and sub information detection. Circuit 307. For reference, the optical disk 3 is shown in the figure.
[0040]
The detection unit 300 detects the wobble shape provided in the track groove 2 (FIG. 2) of the information recording medium 3 described above, and specifies the content of the sub information represented by the wobble shape. More specifically, the detection unit 300 reads a predetermined number of sets of the block mark 101, the reference wobble block 102, and the sub information wobble block 103 of the optical disc 3 described above, and the position of the block mark 101 and the start position of the reference wobble block 102 And the end position, the position of the unit block 104, the frequency of the main carrier of the unit block 104, etc. are specified. Thereafter, these blocks are read again, and the contents of the sub information represented by the wobble shape are specified.
[0041]
Each component will be specifically described below. The optical head 301 irradiates the optical disc 3 with a laser light spot and detects the reflected light. In the optical head 301 of the present specification, it is assumed that the light spot is focused and tracked on the track groove of the optical disc 3 based on control from a servo circuit (not shown). The optical head 301 detects reflected light at two light receiving elements (not shown) divided in a direction (radial direction) orthogonal to the track, and outputs a signal, respectively.
[0042]
The push-pull signal generation circuit 302 performs subtraction processing on the two signals output from the optical head 301 and outputs an electrical signal corresponding to the wobble of the track groove as a push-pull signal. The push-pull signal includes a main carrier corresponding to the wobble period. The rising displacement of the push-pull signal corresponds to the wobble-shaped inner circumferential displacement on the optical disc 3, and the falling displacement corresponds to the outer circumferential displacement. The band pass filter 303 extracts only the main carrier included in the push-pull signal and outputs it to the clock generation circuit 304.
[0043]
The clock generation circuit 304 includes a binarization circuit that binarizes the main carrier, a frequency division circuit that divides the clock by 69, and a PLL circuit, and a clock that synchronizes the binary signal of the main carrier and the frequency division signal of the clock. Is generated. This clock is a clock obtained by multiplying the frequency of the main carrier by the frequency of the frequency dividing circuit, that is, 69 times. Hereinafter, this clock is referred to as a “wobble clock”. The wobble clock is used, for example, as a reference clock for generating a recording signal or a reference clock for generating timing. In this embodiment, this wobble clock is used as a reference clock for detecting sub information in the sub information detection circuit 307.
[0044]
The block mark detection circuit 305 detects the block mark 101 (FIG. 2) that appears at a frequency different from that of the main carrier, and specifies the head position of the block. The timing generation circuit 306 generates various necessary timings as gate signals by counting the wobble clock described above from the block head position specified by the block mark detection circuit 305. In the figure, it is shown that a calibration gate signal used for the second harmonic calibration described later is output to the sub information detection circuit 307. The calibration gate signal becomes a high level at the timing when the reproduction of the reference wobble block 102 (FIG. 2) is started, and becomes a low level at the timing when the reproduction ends.
[0045]
The sub information detection circuit 307 outputs the sub information represented by each unit block 104 of the optical disc 1 based on the push-pull signal, the wobble clock generated by the clock generation circuit 304, and the gate signal generated by the timing generation circuit 306. . The sub information detection circuit 307 can calibrate during the period of the reference wobble block 102 (FIG. 2) and detect the sub information of the subsequent unit block 104 by the process described later. It can be detected.
[0046]
Hereinafter, the sub information detection circuit 307 will be described in detail with reference to FIGS. The sub information detection circuit 307 sets the second harmonic component of the push-pull signal PP as a main processing target. The reason is that the sub information “0” and “1” detected by the sub information detection circuit 307 are represented by the two types of wobble shapes of the unit block 104 (FIG. 2) as described above. This is because the difference can be determined based on the difference in polarity of even-order harmonics. Therefore, the second harmonic of the even harmonics is used.
[0047]
FIG. 4 is a block diagram showing a configuration of the sub information detection circuit 307. FIG. 5 is a diagram showing signal waveforms of the respective parts that are used and generated in the sub information detection circuit 307. Referring to FIG. 4, sub information detection circuit 307 includes bandpass filter 401, binarization circuit 402, phase comparator 403, adder 404, delay unit 405, divider 406, and phase control. The circuit 407 includes a frequency divider 408, a multiplier 409, an integrator 410, a sample hold circuit 411, a binarization circuit 412, and a counter 413.
[0048]
Hereinafter, each component of the sub information detection circuit 307 will be described. First, the band pass filter 401 extracts the second harmonic component SB from the push-pull signal PP. The binarization circuit 402 converts the second harmonic component SB into a digital signal having phase information of the second harmonic component, and outputs a binarized signal SC. That is, the binarizing circuit 402 outputs a binarized signal SC having the same phase as the second harmonic component SB. The phase comparator 403 detects the phase error between the two input signals and outputs phase error information. The adder 404 adds the phase error information to the accumulated value of the previous phase error, and outputs a new accumulated value of the phase error. The delay unit 405 holds the accumulated value of the phase error and outputs it as the accumulated value of the phase error so far. The divider 406 divides the accumulated phase error value by a counter value indicating the accumulated period, and outputs an average value of the phase error. The counter 413 counts the number of clocks and holds it as a counter value.
[0049]
The frequency divider 408 divides the wobble clock generated by multiplying the wobble period by 69 by 34.5 to generate a signal having a frequency corresponding to the second harmonic. The phase control circuit 407 changes the phase of the signal corresponding to the second harmonic based on a separately input phase value (here, an average value of phase errors). This process is called calibration, and the phase control circuit 407 outputs the calibrated second harmonic carrier SP. The multiplier 409 multiplies the second harmonic component SB and the second harmonic carrier SP and outputs the result. The integrator 410 accumulates input values. The multiplier 409 and the integrator 410 are called a heterodyne detector 420, and the processing is so-called heterodyne detection. The integrator 410 outputs the heterodyne detected value HD. The sample hold circuit 411 holds the value HD subjected to heterodyne detection. The binarization circuit 412 determines the sign of the input value and outputs it as sub information of “0” or “1”.
[0050]
Processing of the sub information detection circuit 307 performed by each element described above will be described. FIG. 6 is a flowchart showing a procedure of sub information detection processing by the sub information detection circuit 307 (FIG. 3). As described above, it is assumed that the push-pull signal generation circuit 302 (FIG. 3) has already generated the push-pull signal PP from the reflected light of the optical disc 3 (step S601). Further, based on the push-pull signal PP, the clock generation circuit 304 (FIG. 3) generates a wobble clock, and the timing generation circuit 306 (FIG. 3) generates a calibration gate signal (step S602).
[0051]
First, based on the wobble clock input to the sub information detection circuit 307, the frequency divider 408 generates a signal having a frequency corresponding to the second harmonic. Then, the phase control circuit 407 gives a predetermined phase to the generated signal, and outputs the second harmonic carrier SP (step S603). As an initial value of the phase to be given, for example, the phase is the same as that of the divided signal of the wobble clock included in the clock generation circuit 304 (FIG. 3) described above.
[0052]
When the timing for starting reproduction of the reference wobble block 102 (FIG. 2) is reached, the calibration gate GC generated by the timing generation circuit 306 (FIG. 3) rises and phase calibration of the second harmonic carrier SP starts. Is done.
[0053]
The band pass filter 401 extracts the second harmonic component SB based on the push-pull signal PP input to the sub information detection circuit 307 (step S604). Then, the binarization circuit 402 converts the second harmonic component SB extracted by the bandpass filter 401 into a binarized signal SC having phase information and outputs it.
[0054]
The phase comparator 403 detects a phase error between the binarized signal SC and the second harmonic carrier SP and outputs phase error information. The adder 404 cumulatively adds the phase error represented by the phase error information and the accumulated value of the phase error so far from the delay unit 405 for each clock edge, and outputs a phase error integrated value SI (S605). ). This phase error integrated value SI is held in the delay device 405 again. This process is continued until the calibration gate GC is at a high level, that is, at a low level (step S606). As shown in FIG. 5, the calibration gate GC is generally at a high level during reproduction of the reference wobble block 102. It is understood that the phase error integrated value SI is integrated and gradually increases while the calibration gate GC is at the high level.
[0055]
Referring to FIG. 6 again, when the calibration gate GC falls to the low level (“YES” in step S606), the cumulative addition process is terminated. The divider 406 divides the phase error integrated value SI by the counter value held by the counter 413, calculates the average value of the phase error, and outputs it (step S607).
[0056]
The phase control circuit 407 updates the phase of the second harmonic carrier SP based on the average value (average phase error) of the phase errors output from the divider 406 (step S608). For example, if the average phase error is +3 clocks, the phase control circuit 407 advances the phase of the second harmonic carrier SP by 3 clocks. By this processing, the phase of the second harmonic carrier SP inputted again to the phase comparator 403 and the phase of the binarized signal SC can be matched. Note that “aligning phases” means, for example, aligning the phases of the rising edges of two signals. Therefore, the second harmonic carrier SP and the binarized signal SC are in phase or in phase. As described above, the binarized signal SC is in phase with the second harmonic component SB extracted based on the push-pull signal PP. Therefore, the second harmonic carrier SP whose phase has been updated based on the average phase error is also in phase with the second harmonic component SB.
[0057]
Subsequently, heterodyne detection of the second harmonic carrier SP and the second harmonic component SB obtained as described above is performed. Specifically, the multiplier 409 multiplies the second harmonic carrier SP and the second harmonic component SB. The target of multiplication is a wobble signal including sub information. This is because when the phases of the two signals are aligned, the reading period of the reference wobble block 102 (FIG. 2) ends and the reading period of the unit block 104 of the sub information wobble block 103 (FIG. 2) starts. The integrator 410 integrates the multiplication results and outputs the result as a heterodyne detection signal HD (step S609). This process will be described in more detail with reference to FIG. 5. Since the second harmonic component SB and the second harmonic carrier SP are in opposite phases when the first unit block 104 is reproduced, the multiplication value is Become negative. Therefore, as the reproduction of the first unit block 104 proceeds, the heterodyne detection signal HD swings in the negative direction. When the reproduction of the block is completed, the heterodyne detection signal HD is reset. At the time of reproduction of the second unit block 104, the second harmonic component SB and the second harmonic carrier SP are in phase, so the multiplication value becomes positive. Therefore, the heterodyne detection signal HD swings in the positive direction.
[0058]
Referring to FIG. 6 again, the sample hold circuit 411 holds the heterodyne detection signal HD, the binarization circuit 412 determines its sign, and outputs a value of 0 or 1. For example, the binarization circuit 412 outputs 0 when the held heterodyne detection signal HD is positive, and outputs 1 when it is negative (step S610).
[0059]
As the correspondence between the code and the output value, the reproduction waveform of the reference wobble block 102 is used. That is, when the reproduction waveform of the unit block 104 matches the reproduction waveform of the reference wobble block 102, the value held by the sample hold circuit 411 is positive. Therefore, in this case, the binarization circuit 412 is processed so as to correspond to the same value “0” that the reference wobble block 102 represents. On the other hand, when the reproduction waveform of the unit block 104 is different (not coincident) with the reproduction waveform of the reference wobble block 102, the value held by the sample hold circuit 411 is negative. Therefore, in this case, the binarization circuit 412 is processed so as to correspond to the value “1”. This process compares the wobble shape of the reference wobble block 102 with the wobble shape of the unit section 104, and detects that the wobble shape of the unit section 104 is the same shape as the reference wobble. Represents sub-information “0”, and if it is detected that the wobble shape of the unit block 104 is different from that of the reference wobble, the process is substantially the same as the process of representing the sub-information “1”. By detecting the sub information in the sub information wobble using the reference wobble in this way, it is possible to always detect the sub information in the optimum state even when there is a phase shift of the wobble clock due to crosstalk.
[0060]
In the present embodiment, sub-information is detected using the detected phase information as it is, but a value obtained by adding a constant ratio between the current phase and the phase detected by the reference wobble is used as the detection result. You may add the effect of a low-pass filter.
[0061]
Here, the processing of the frequency divider 408 (FIG. 4) will be described. When the wobble clock generated by the clock generation circuit 304 (FIG. 3) corresponds to a multiple of exactly 4 of the wobble frequency, there is no problem for the frequency divider 408 to generate the second harmonic by frequency division. However, if this is not the case, for example, when the magnification is 69 times, a problem occurs. FIG. 7A shows a clock waveform in which the lengths of the “H” section and the “L” section are asymmetric. When the frequency divider 408 generates the second harmonic using the wobble clock, as shown in FIG. 7A, the 17T (T is the wobble clock period) interval “H”, the 17T interval “L”, and the 17T interval The lengths of the “H” section and the “L” section are different, such as “H” and 18T section “L”. When phase comparison or heterodyne detection is performed using such an asymmetric waveform, a detection error occurs. However, since the wobble clock is normally used as a recording clock, the multiplication ratio of the wobble clock cannot be a multiple of four.
[0062]
FIG. 7B is a diagram illustrating a clock waveform that cancels the asymmetry between the lengths of the “H” and “L” sections of the clock waveform. In order to avoid a detection error, four harmonics are generated for four periods, and the above asymmetry may be canceled in the two previous periods and the two subsequent periods. As a result, errors in phase detection and heterodyne detection can be totally eliminated.
[0063]
As described above, according to the optical disk reproducing apparatus of the present embodiment, even when a wobble clock phase shift occurs due to interference between adjacent tracks, heterodyne detection can always be performed in an optimum state to reproduce sub information.
[0064]
(Embodiment 2)
Next, an optical disk reproducing apparatus according to Embodiment 2 will be described. The configuration and operation of the optical disk reproducing apparatus according to the second embodiment is the same as that of the optical disk according to the first embodiment except that the sub information detecting circuit 807 shown in FIG. 8 is provided instead of the sub information detecting circuit 307 (FIG. 3). The configuration and operation of the playback apparatus (FIG. 3) are the same. Therefore, the components and operation of the sub information detection circuit 807 will be mainly described below.
[0065]
FIG. 8 is a block diagram showing a configuration of the sub information detection circuit 807 according to the second embodiment. FIG. 9 is a diagram showing signal waveforms of the respective parts that are used and generated in the sub information detection circuit 807. Referring to FIG. 8, sub information detection circuit 807 includes bandpass filter 401, binarization circuit 402, edge phase comparator 801, accumulator 802, phase error determination circuit 803, and phase polarity determination circuit. 804, a phase polarity control circuit 805, a phase control circuit 407, a frequency divider 408, a multiplier 409, an integrator 410, a sample hold circuit 411, and a binarization circuit 412. Among these, the band pass filter 401, the binarization circuit 402, the phase control circuit 407, the frequency divider 408, the multiplier 409, the integrator 410, the sample hold circuit 411, and the binarization circuit 412 are implemented. Since it has already been described in Embodiment 1, it is omitted here.
[0066]
The edge phase comparator 801 outputs the phase error between the two input signals based on the phase control gate signal. The accumulator 802 accumulates and adds phase errors as input values as needed. The phase error determination circuit 803 outputs a phase value for advancing or delaying the phase clock based on the phase error. Based on the heterodyne detection signal HD, the phase polarity determination circuit 804 determines whether the second harmonic division has converged to 0 ° or 180 °. The phase polarity control circuit 805 normally rotates or inverts the output of the phase control circuit 407 based on the phase polarity determination value. Then, the phase polarity control circuit 805 outputs the second harmonic carrier SP.
[0067]
Next, processing of the sub information detection circuit 807 performed by each element described above will be described. As a premise, it is assumed that the push-pull signal generation circuit 302 (FIG. 3) has already generated the push-pull signal PP from the reflected light of the optical disc 3. Further, it is assumed that the clock generation circuit 304 (FIG. 3) generates a wobble clock based on the push-pull signal PP.
[0068]
Similar to the first embodiment, the frequency divider 408 generates a signal having a frequency corresponding to the second harmonic based on the wobble clock, and the phase control circuit 407 gives a predetermined phase to the generated signal. The second harmonic carrier SP1 is output. The band pass filter 401 extracts the second harmonic component SB based on the push-pull signal PP input to the sub information detection circuit 807. Then, the binarization circuit 402 converts the second harmonic component SB extracted by the bandpass filter 401 into a binarized signal SC having phase information and outputs it.
[0069]
Subsequently, processing for aligning the edges of the binarized signal SC and the second harmonic carrier SP1 is performed. The edge phase comparator 801 generates a rising edge and a falling edge of the binarized signal SC based on the phase control gate signal, and a rising edge and a falling edge of the second harmonic carrier SP1 output from the phase control circuit 407. The phase error of is output. As shown in FIG. 9, the phase control gate signal is a signal that becomes high level during reproduction of the unit block 104 of the sub information wobble block 103 and becomes low level during non-reproduction. The accumulator 802 accumulates and adds the phase error output from the edge phase comparator 801 as needed.
[0070]
When the phase error cumulatively added by the accumulator 802 reaches a positive predetermined value, the phase error determination circuit 803 advances the phase of the phase control circuit 407 by one clock and resets the value of the accumulator 802 to 0. Conversely, when the phase error reaches a predetermined negative value, the phase of the phase control circuit 407 is delayed by one clock, and the value of the integrator 802 is reset to zero. These operations are performed whenever the phase control gate is “H”, that is, during reproduction of the sub information wobble, and the value of the integrator 802 is held in the interval where the phase control gate is “L”.
[0071]
The reason why the above processing is performed will be described. The phase of the second harmonic component SB of the sub information wobble is indefinite because the phase polarity is inverted based on the sub information “0” and “1”. Therefore, normal phase error detection, for example, phase error detection between rising edges cannot be performed. Therefore, by comparing the phases using both the rising edge and the falling edge, regardless of the sub information “0” and “1”, −90 ° to + 90 ° or + 90 ° to −90 ° (± 180 degrees), and the phases of the two signals can be made uniform. As a result, the phases of the two signals can be converged to 0 ° or 180 °.
[0072]
However, even if the phase of the binarized signal SC and the phase of the second harmonic carrier SP1 are aligned, it cannot be determined whether the phase has converged to 0 ° (normal rotation) or 180 ° (inversion). . That is, it cannot be determined whether the binarized signal SC and the second harmonic carrier SP1 are in phase or inverted. Therefore, in this embodiment, by detecting the phase polarity in advance using the wobble of the reference wobble block 102 (FIG. 2), it is determined whether the two signals are in phase or 180 ° out of phase.
[0073]
The phase polarity detection process using the wobble of the reference wobble block 102 is as follows. When reproduction of the reference wobble is started, the phase polarity determination gate rises, and heterodyne detection is performed in the phase state of the current second harmonic carrier SP1. At this time, the second harmonic carrier SP1 is input to the multiplier 409 as the second harmonic carrier SP2 via the phase polarity control circuit 805. As a result of the heterodyne detection in multiplier 409 and integrator 410, heterodyne detection signal HD is output and input to phase polarity determination circuit 804. Based on the heterodyne detection signal HD, the phase polarity determination circuit 804 determines whether the second harmonic carrier SP1 obtained by frequency division converges at 0 ° or 180 °. If the phase polarity control circuit 805 determines that the second harmonic carrier SP1 has converged to 0 ° based on the determination result, the phase polarity control circuit 805 performs forward rotation processing on the second harmonic carrier SP1 and converges to 180 °. If it is determined that the second harmonic carrier SP2 is generated, the inversion process is performed. The second harmonic carrier SP2 is input again to the multiplier 409, and heterodyne detection is performed with the phase polarity. Then, the sub information is output from the binarization circuit 412 based on the processing described in the first embodiment.
[0074]
In the detection of the phase polarity, if the absolute value of the detection result is small, it can be determined that the phase control in the sub information wobble described above is indeterminate or that the reference wobble has some defect. You may make it hold | maintain a state. Further, when the convergence by the phase control is completed and the track groove is continuously scanned, the detection result should not change. Therefore, the phase polarity may be determined based on the plurality of detection results by determining the continuity of the detection results, adding a plurality of detection results, or passing the low-pass filter.
[0075]
As described above, the optical disc reproducing apparatus of the second embodiment determines the phase polarity of 0 ° or 180 ° using the reference wobble, and uses the sub information wobble itself to determine the detailed phase of ± 90 °. Synchronized. As a result, finer control than in the first embodiment can be performed using a large amount of information, and further performance improvement can be achieved.
[0076]
【The invention's effect】
According to the present invention, when reproducing the sub information from the optical disc having the sub information in the phase of the harmonic, a harmonic carrier is generated in a phase state during a predetermined reference wobble period and used for detection. As a result, even when a wobble clock phase shift occurs due to interference between adjacent tracks, heterodyne detection can always be performed in an optimum state to reproduce sub information.
[Brief description of the drawings]
FIG. 1 is a top view of an information recording medium.
FIG. 2 is a schematic view showing a structure of a main part of a track groove.
FIG. 3 is a block diagram illustrating a configuration of a detection unit that detects sub-information on the optical disc 3;
FIG. 4 is a block diagram showing a configuration of a sub information detection circuit.
FIG. 5 is a diagram showing signal waveforms of the respective parts that are used and generated in the sub information detection circuit.
FIG. 6 is a flowchart showing a procedure of sub-information detection processing by a sub-information detection circuit.
FIG. 7A is a diagram illustrating clock waveforms in which the lengths of the “H” section and the “L” section are asymmetric. FIG. 6B is a diagram illustrating a clock waveform that cancels the asymmetry between the lengths of the “H” and “L” periods of the clock waveform.
FIG. 8 is a block diagram showing a configuration of a sub information detection circuit according to a second embodiment.
FIG. 9 is a diagram showing signal waveforms of each part used and generated in the sub information detection circuit.
[Explanation of symbols]
307 Sub information detection circuit
401 Band pass filter
402 Binarization circuit of second harmonic component
403 Phase comparator
404 integrator
405 delay
406 Divider
407 Phase control circuit
408 divider
409 multiplier
410 integrator
411 Sample hold circuit
412 Binarization circuit of sub information
413 counter
420 Heterodyne detector

Claims (7)

A reference wobble block having a first wobble shape, a block mark provided before the reference wobble block , and an information wobble block including a plurality of sections provided after the reference wobble block , and each of the sections Is a reproduction method for reproducing an information recording medium having either the same shape as the first wobble shape of the reference wobble block or the second wobble shape different from the first wobble shape of the reference wobble block . There,
Detecting the block mark;
Reading the reference wobble block following the block mark ;
Reading the information wobble block;
Comparing whether the wobble shape of each section of the read information wobble block is the same as the first wobble shape of the read reference wobble block;
If the wobble shape of a section of the information wobble block coincides with the first wobble shape of the reference wobble block, to the one section of the information wobble block is the first information is recorded determined that, when the wobble shape of the one section of the information wobble block is different from the first wobble shape of the reference wobble block, to the one section of the information wobble block is the Determining that the information of 2 is recorded;
Depending on the determination results, reproduction method and a step of outputting the first information and the second information for each section. The first wobble shape is represented using at least a first fundamental wave and a second harmonic wave in a Fourier series,
The second wobble shape is expressed using at least a primary fundamental wave and a second harmonic in a Fourier series, and the polarity of the second harmonic is the second harmonic of the first wobble pattern. The regeneration method according to claim 1, which is opposite in polarity to the above. The comparing step includes:
Generating a second harmonic carrier having a frequency corresponding to the second harmonic based on the period of the first wobble shape;
Extracting the second harmonic component from the waveform obtained by reading the reference wobble block;
Comparing the phase of the second harmonic carrier and the phase of the second harmonic component to detect a phase error;
The step of determining includes
Changing the phase of the second harmonic carrier based on the detected phase error;
A step of newly extracting a second harmonic component from the waveform obtained by reading out the information wobble block;
Heterodyne detection of the newly extracted second harmonic component and the second harmonic carrier whose phase has been changed, and generating a detection signal;
If the sign of the detection signal is positive, it is determined that the wobble shape of the information wobble block matches the first wobble shape. If the sign of the detection signal is negative, the wobble shape of the information wobble block The reproduction method according to claim 2, wherein it is determined that is different from the first wobble shape.   The reproduction method according to claim 3, wherein the phase error is an average value of accumulated phase errors during the period of the reference wobble block. The comparing step includes:
Generating a second harmonic carrier having a frequency corresponding to the second harmonic based on the period of the first wobble shape;
Extracting the second harmonic component from the waveform obtained by reading the reference wobble block;
Comparing the phase of the second harmonic carrier and the phase of the second harmonic component to detect a phase error;
The step of determining includes
Changing the phase of the second harmonic carrier based on the detected phase error;
Generating a second harmonic carrier having a frequency corresponding to the second harmonic based on the period of the first wobble shape;
Extracting the second harmonic component from the waveform obtained by reading the reference wobble block;
Heterodyne detection of the second harmonic component and the second harmonic carrier to generate a first detection signal;
Determining the phase polarity of the second harmonic carrier based on the first detection signal;
Performing one of normal rotation processing and inversion processing of the second harmonic carrier based on the determination result, and newly generating a second harmonic carrier;
A step of newly extracting a second harmonic component from the waveform obtained by reading out the information wobble block;
Heterodyne detection of the newly extracted second harmonic component and the newly generated second harmonic carrier to generate a second detection signal;
The method according to claim 2, further comprising: determining whether a wobble shape of the information wobble block matches the first wobble shape according to a sign of the second detection signal.   The step of detecting the phase error detects the phase error by comparing the phase of the rising edge and the falling edge of the second harmonic carrier and the phase of the rising edge and the falling edge of the second harmonic component. The reproduction method according to claim 5. A reference wobble block having a first wobble shape, a block mark provided before the reference wobble block, and an information wobble block including a plurality of sections provided after the reference wobble block, each of the sections Is a reproducing apparatus for reproducing an information recording medium having either the same shape as the first wobble shape of the reference wobble block or the second wobble shape different from the first wobble shape of the reference wobble block. There,
  Means for detecting the block mark;
  Means for reading the reference wobble block following the block mark;
  Means for reading the information wobble block;
  Means for comparing whether the wobble shape of each section of the read information wobble block is the same as the first wobble shape of the read reference wobble block;
  When the wobble shape of one section of the information wobble block matches the first wobble shape of the reference wobble block, the first information is recorded in the one section of the information wobble block. If the wobble shape of the one section of the information wobble block is different from the first wobble shape of the reference wobble block, the second section of the information wobble block includes a second wobble shape. Means for determining that the information is recorded,
  Means for outputting the first information or the second information for each section according to a result of the determination;
  A playback apparatus having

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