JP2008257801A - Optical information recording and reproducing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform highly accurate reproduction of multi-level recording by obtaining error information indicating an offset of a reproduced signal, a variation in amplitude, and a deviation of a reproduced clock of the reproduced signal, without reducing a user area. <P>SOLUTION: An optical information recording and reproducing method records and/or reproduces multi-level information having a plurality of levels by virtually providing equally spaced cells on a track of an optical information medium on which recording and reproduction of information is performed using a light spot, and changing a width or an area of an information pit in a track direction on a cell-by-cell basis, to obtain multiple amplitude levels of the reproduced signal. The information recording and reproducing method includes obtaining a reproduced value corresponding to a combination of levels of adjacent cells by learning, storing the reproduced value as a reference value, detecting the error information of the reproduced signal based on a difference between a sampling value of the reproduced signal sampled in accordance with the reproduced clock and the reference value when information is reproduced, and correcting a phase of the reproduced signal and/or the reproduced clock based on the error information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical information recording / reproducing method and apparatus for recording or reproducing information pit levels using three or more values, and more particularly to detecting error information between a reproduced signal and an ideal state from recorded information. The present invention relates to an error information detection method and apparatus in a value level recording / reproducing system.

  In recent years, the optical memory industry has been expanding, from read-only CDs (Compact Discs) and DVDs (Digital Versatile Discs) to write-once using metal thin films and dye-based recording materials, as well as magneto-optical materials and phase change materials. The rewritable type used has been developed. Its application is also expanding from consumer to external memory of computers. Furthermore, research and development for increasing the recording capacity has been promoted, and as a technique for miniaturizing a light spot related to information recording / reproduction, the wavelength of the light source is changing from red (650 nm) to blue-violet (405 nm). is there. Also, the numerical aperture NA (Numerical Aperture) of the objective lens is about to be increased from 0.6 or 0.65 to 0.85. On the other hand, a more efficient multilevel recording / reproducing technique using the same light spot size has been proposed.

  For example, the inventor of the present application has proposed the following method as a method of the multilevel recording / reproducing technique (see Patent Document 1). According to this, multi-value information is recorded on the information track of the optical information recording medium by a combination of the width of the information pit in the track direction and the shift amount in the track direction with respect to the reproduction light spot of the information pit. When reproducing the multi-value recorded information pit, the multi-value information is reproduced from the correlation between the detection signal learned in advance and the detection signal obtained from the light spot.

  In addition, the following announcement is made at International Symposium on Optical Memory (ISOM) 2003, which is an international academic conference in research on the optical disc field (see Non-Patent Document 1). According to this, a blue-violet light source (405 nm) and an optical system in which the numerical aperture NA of the objective lens is 0.65 are used. As a result, with respect to an optical disc having a track pitch of 0.46 μm, the width in the track direction of an area for recording one information pit (hereinafter referred to as “cell”) is set to 0.26 μm, and 8-level multilevel recording is performed. Perform playback.

Further, the following proposal has been made by the present applicant (see Patent Document 2). According to this, a blue-violet light source (405 nm) and an optical system with an objective lens numerical aperture NA of 0.85 are used, the light spot is miniaturized, and adapted to the multi-value method announced at ISOM 2003, approximately 30 Gbit / Increase the density to about ² inches.

  According to this, the selection of 8-level information pits is performed, for example, by dividing the width of the cell in the track direction into 16 equal parts (16 channel bits) as shown in FIG. That is, level 0 does not record any information pits. Level 1 is a width of 2 channel bits, level 2 is a width of 4 channel bits, level 3 is a width of 6 channel bits, and level 4 is a width of 8 channel bits. Further, level 5 is 10 channel bits wide, level 6 is 12 channel bits wide, and level 7 is 14 channel bits wide.

  FIG. 9 shows the relationship between the light spot 22 and a schematic diagram when random information pits 21 are recorded on the track 20 on the optical disk. In order to increase the storage capacity, it is necessary to reduce the size of the cell, and if it is reduced, the information pits 21 of two to three cells are included in the light spot 22 as shown in FIG. That is, at the time of reproduction, the reproduction signal is expected to fluctuate due to the influence of intersymbol interference from adjacent cells. In the figure, the direction of the arrow A similarly indicates the track direction, and each cell is virtually provided with a region delimited by a broken line.

  Next, in order to know the state of the reproduction signal by this method, the result of optical simulation will be described.

  FIG. 10 shows parameters used in the optical simulation. The track pitch is 0.32 μm, the light spot size is 0.405 μm (wavelength 405 nm, the numerical aperture of the objective lens: NA 0.85), and the cell size is 0.2 μm.

  FIG. 11 shows the shape of information pits given to the respective levels shown in FIG. 8 by optical simulation using the parameters shown in FIG. Here, level 0 shall not record any information pits.

  In FIG. 12, eight types of levels are sequentially combined in three consecutive cells (all combinations are 8 × 8 × 8 = 512), and the light spot is the third cell (back) from the center of the first cell (previous cell). The reproduction signal (the amount of reflected light) when moved to the center of the cell was calculated. In the lower diagram of FIG. 12, eight combinations of levels of three cells (0, 1, 6) to (7, 1, 6) are shown as examples (all levels except for three cells are 0 level). . The positions of the three solid lines in the figure indicate the reproduction signal (cell center value) when there is a light spot at the center of each cell. It can be seen from this that, in this parameter, the cell median value of the middle cell corresponds to the level “1”, but the level of the left cell changes from “0” to “7”. It takes a value and has a width. This is the effect of intersymbol interference.

  FIG. 13 shows the distribution of the amplitude of each reproduction signal with the level of the middle cell on the horizontal axis in all combinations of levels recorded in three consecutive cells (here, the vertical axis). Indicates the relative amplitude of the reproduction signal). Distributions A to H in the figure correspond to levels 0 to 7, respectively. As can be seen from the figure, the overlapping of the distributions of the reproduction signals at adjacent levels increases, and it is difficult to identify the levels using a fixed threshold value. Therefore, in general, the reproduction signal is subjected to signal processing such as waveform equalization to increase the degree of separation of the reproduction signal distribution.

  For example, a 3-tap waveform equalization as shown in FIG. 14 is calculated. Here, T is the time during which the light spot moves from the center of one cell to the center of the adjacent cell, and a is an equalization coefficient, where a = −V1 / (1 + V1), V1 = 0.237. As calculated. Here, V1 is an amplitude value in an adjacent cell with respect to an isolated waveform of amplitude 1.

  The results are shown in FIG. In the same figure, the vertical axis similarly indicates the amplitude of the reproduction signal. A 'to H' in the figure correspond to distributions of levels 0 to 7, respectively. As can be seen from the figure, each distribution can be separated with a fixed threshold.

  FIG. 16 is obtained by re-plotting the results shown in FIG. 15 with the horizontal axis representing the number of samples (1 to 512). In the figure, the levels of three consecutive cells are x, y, and z, and the reproduction signal is S (x, y, z), and plotted using the program shown in FIG. This figure is obtained by calculation, and shows the influence of intersymbol interference from the front and rear cells and the nonlinear influence caused by the fact that the light spot shape is Gaussian and not uniform. In an actual recording / playback system, the influence of thermal interference due to heat storage of the medium, the influence of individual differences in medium sensitivity, and the like are further obtained as a result of this learning table.

  When a general multilevel recording reproduction algorithm is applied, a learning table such as that previously obtained in FIG. 16 is first obtained from the learning data.

  Next, random data is reproduced. At this time, based on the reproduction signal of random data, the median value of each cell is determined with a fixed threshold value, and the level is provisionally determined. The method of selecting a fixed threshold is, for example, averaging the values in the learning table of the central cell having the same level value (that is, averaging the values of the respective distributions A ′ to H ′, as explained in FIG. 15), This is used as a reference value for each level, and an intermediate value between adjacent reference values for levels is used as a threshold value.

  Subsequently, eight reference values (from 0 level to 7 levels) according to the reproduction value of the center cell are extracted from the learning table according to the temporarily determined values of the preceding and following cells. The eight reference values are compared with the reproduction value of the center cell, and the reference value level closest to the reproduction value is determined again as the reproduction level. For example, it is assumed that the levels of the preceding and following cells are 3 and 5 as a result of the provisional determination. In this case, from the learning table, combinations of the levels of the preceding and following cells and the center cell are (3, 0, 5), (3, 1, 5), (3, 2, 5), (3, 3, 5), The values of (3, 4, 5), (3, 5, 5), (3, 6, 5), (3, 7, 5) are extracted.

  On the other hand, a reproduction clock for sampling information generally has a configuration in which phase error information is detected by reproduction of a predetermined pattern inserted at predetermined intervals in recorded information and is generated in a PLL (phase locked loop) circuit. I'm taking it.

FIG. 18 shows a pattern insertion example for phase error detection. (I) to (Q) in the figure indicate recording information strings. (I) is a PLL pull-in pattern located at the beginning of the recording data, and this pattern is often used regardless of multi-level recording. (J) is a learning pattern for obtaining the learning table described above. (K), (M), and (O) are user information to be recorded, which are generated by performing processing such as error correction. (L), (N), and (P) are recording patterns for detecting a phase error of the reproduction clock. For example, an edge is extracted by binarization processing using a level slice, phase error information between the edge and the recovered clock is detected by a phase comparator, and is used for PLL processing of the recovered clock.
Japanese Patent Laid-Open No. 5-128530 JP 2006-236441 A ISO2003 (Write-once Disks for Multi-level Optical Recording: Proceedings Fr-Po-04)

  However, the reproduction signal of the multilevel signal is greatly affected by the reflectance unevenness of the medium, and there is a problem that the reproduction signal is erroneously read if there is an offset of the reproduction signal or amplitude fluctuation of the reproduction signal. As a solution to this, it is possible to correct the offset and amplitude fluctuation by inserting a dedicated mark for reading the offset and amplitude fluctuation of the reproduction signal and reading the mark, but this reduces the user area. There was a problem.

  Further, when the phase of the reproduction clock of the reproduction signal is deviated, there is a problem that the reproduction signal is similarly read erroneously. As a solution to this problem, there is a method of detecting a phase error by providing a phase error detection pattern. However, there is a problem that the user area is similarly reduced.

  An object of the present invention is to obtain error information indicating the offset of the reproduction signal, the amplitude variation, and the deviation of the reproduction clock of the reproduction signal without narrowing the user area, and to reproduce the multi-value recording with high accuracy. is there.

  In order to achieve the above object, an optical information recording / reproducing method according to the present invention is provided with cells at virtually constant intervals on a track of an optical information medium for recording / reproducing information using a light spot, In an optical information recording / reproducing method for recording and / or reproducing multi-level information of multiple levels by changing the width of the information pit in the track direction or the area of the information pit for each cell and making the amplitude of the reproduction signal multistage The reproduction value for the combination of adjacent cell levels is obtained by learning, the reproduction value is stored as a reference value, and the information is reproduced from the difference between the sample value of the reproduction signal sampled according to the reproduction clock and the reference value. Error information of the reproduction signal is detected, and the phase of the reproduction signal and / or the reproduction clock is corrected based on the error information.

  The error information may be information indicating an offset of the reproduction signal. In this case, the difference between the reference value and the sample value may be accumulated for a certain period, the offset of the reproduction signal may be determined according to the accumulated value, and the offset of the reproduction signal may be corrected based on the offset amount. .

  The error information may be information indicating amplitude fluctuation of the reproduction signal. In this case, the difference between the reference value and the sample value is integrated for a certain period of time when the amplitude of the reproduction signal is positive and negative, and the amplitude fluctuation of the reproduction signal is calculated according to the integrated value of both. The amplitude fluctuation of the reproduction signal may be corrected based on the amplitude fluctuation amount.

  The error information may be information indicating a phase error of the recovered clock. In this case, the difference between the reference value and the sample value is integrated for a certain period of time when the slope of the reproduction signal is positive and negative, and the phase shift of the reproduction clock is calculated according to the integrated value of both. The phase of the recovered clock may be corrected based on the amount of phase shift.

  An optical information recording / reproducing apparatus according to the present invention virtually provides cells at regular intervals on a track of an optical information medium for recording / reproducing information using a light spot, and each cell has a track direction. In an optical information recording / reproducing apparatus that records and / or reproduces multi-level information of multiple levels by changing the width of the information pit or the area of the information pit and making the amplitude of the reproduction signal multistage, the level of adjacent cells A storage means for obtaining a reproduction value for the combination by learning and storing the reproduction value as a reference value, and at the time of reproducing information, the difference between the sample value of the reproduction signal sampled according to the reproduction clock and the reference value And correction means for detecting error information and correcting the phase of the reproduction signal and / or the reproduction clock based on the error information. To.

  According to the present invention, it is possible to obtain error information indicating the offset of the reproduction signal, the amplitude fluctuation, and the deviation of the reproduction clock without narrowing the user area, and reproduction of multi-value recording with high accuracy can be performed.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of the optical information recording / reproducing apparatus according to the present embodiment. The optical information recording / reproducing apparatus 1 shown in FIG. 1 includes a control circuit 2, a spindle motor 3, an optical disk 4, an optical head 5, an optical head control circuit 6, an information recording circuit 7, an information reproducing circuit 8, a spindle motor controller 9, and An interface controller 10 is included.

  The control circuit 2 controls transmission / reception of information to / from an information processing apparatus such as an external computer, controls information recording / reproduction with respect to the optical disc 4 using the information recording circuit 7 and the information reproduction circuit 8, and other Control the moving part.

  The spindle motor 3 is controlled by the spindle motor controller 9 and drives the optical disk 4 to rotate.

The optical disk 4 is an optical information recording medium that is inserted into or ejected from the optical information recording / reproducing apparatus 1 by a mechanism (not shown). The optical disk 4 has a track pitch of 0.32 μm. In this case, if the cell length is 200 nm, approximately 30Gbit / inch ² or so, if the cell length is 160 nm, approximately 36Gbit / inch ² approximately densification aim.

  The optical head 5 optically records information on the optical disk 4 and reproduces it. For the optical head 5, for example, when the wavelength λ of the light source is 405 nm and the numerical aperture NA of the objective lens is 0.85, the value of the size of the light spot can be approximately 405 nm.

  The optical head control circuit 6 controls the position of the light spot by the optical head 5 under the control of the control circuit 2, and performs auto tracking control, seek operation control, and auto focusing control.

  The information recording circuit 7 records multi-value information on the optical disc 4 via the optical head 5 under the control of the control circuit 2.

  The information reproducing circuit 8 reproduces multi-value information from the optical disk 4 via the optical head 5 under the control of the control circuit 2. As will be described later, the information reproducing circuit 8 is equipped with the storage means and correction means of the present invention.

  The multi-value information is recorded in the same manner as shown in FIG. In other words, cells on the optical disc 4 that is an optical information medium are virtually provided with cells at regular intervals, and the width of the information pit in the track direction or the area of the information pit is changed for each cell, and This is performed so that multi-level information of a plurality of levels can be obtained by making the amplitude multistage.

  In addition to the phase change material, a magneto-optical material can be used as a recording material that can be recorded and erased on the optical disk 4. In this case, the optical information recording / reproducing apparatus 1 described above changes the shape of the information pits in cooperation with a magnetic field from a magnetic head (not shown) other than the light spot, thereby forming information pits having a plurality of reproduction levels.

  Next, a case where error information between the sample value and the reference value is detected by the optical information recording / reproducing apparatus 1 of the present embodiment will be described.

  FIG. 2 shows an example of the record information sequence. In the figure, (R) is a PLL pull-in pattern located at the beginning of the recording data, and this pattern is often employed regardless of multi-value recording. (S) is a learning pattern for obtaining a learning table described in FIG. (T) is user information to be recorded, which is generated by adding an error correction code or the like. Thus, in this embodiment, the phase error detection pattern shown in the conventional example of FIG. 17 is not used. However, the present invention can be applied even with this phase error pattern.

  First, at the start of recording, a pattern (R) used for PLL pull-in is generated. Here, with respect to the pattern (R) used for pulling in the PLL, a pattern in which frequency and phase error information is obtained by binarization and the PLL is applied as is conventionally performed. For example, regardless of the multi-value recording information sequence, the entire cell may be a mark, or a pattern having no mark in the cell may be repeated. Furthermore, in order to obtain a reproduction signal with a higher signal-to-noise ratio, a pattern in which two cells are all marked and non-marked may be used, or a pattern formed by a combination of these may be used. Of course, it may be a repetition of 0 level and 7 level.

  Next, a learning pattern (S) of an 8-level multilevel information sequence is generated, and recording data is added following the PLL pull-in pattern. In this learning pattern, all 512 patterns of 8 × 8 × 8 combinations of the center cell and the preceding and following cells may be recorded, or the number necessary for matching the learning table obtained from the calculation in advance with the actual recording / reproducing system. It may be the data.

  Finally, the received recording information is converted into 8 levels every 3 bits (where modulation, error correction code addition, etc. are performed), and user information (T) is generated and recorded. It is added as an information string.

  The recording information sequence generated as described above is received, and the multi-value information is recorded on the target track on the optical disc 4 which is an optical information medium by using the optical head 5 using the recording pulse sequence corresponding to each multi-level. To do.

  Here, recording of control information such as address information has not been described, but recording may be performed by providing a separate control area, or may be formed by wobbling the guide groove of the information recording track. .

  Next, a procedure for reproducing the multi-value information recorded in this way will be described.

  First, upon receiving an information reproduction command, the optical information recording / reproducing apparatus 1 starts a reproduction operation. As a result, the address information is reproduced from the wobble information or the like as described above, and the target track of the optical disc 4 is searched. Then, reproduction of the PLL pull-in area (R) at the head of the information recording unit is started using the optical head 5, and a reproduction clock synchronized with the reproduction signal is generated.

  Next, using the reproduction clock synchronized with the reproduction signal, the learning pattern is reproduced, the reproduction signal level for each recording pattern is sampled, and stored in the learning table. Note that, since the recovered clock at this time can maintain a state synchronized with the recovered signal by the PLL pull-in pattern, it is not particularly necessary to perform the recovered clock phase control. That is, after reproducing the PLL pull-in pattern, sufficient phase accuracy can be obtained by setting the phase error information to “zero” and maintaining the PLL state.

  Next, based on the learning result, the reproduction of the recorded information is started from the reproduction signal.

  FIG. 3 shows an ideal reproduction signal. The position of the broken line corresponds to the center of the cell, and the reproduction signal is sampled at this position. A value obtained by intersecting the solid waveform and the broken line is obtained as a sample value. Black circles are reference values on the learning table. In the vertical axis here, the center value of the maximum amplitude of an ideal signal is zero. The position of the vertical axis 0 in the following FIGS. 4 to 6 is the same as this.

  The ideal state in FIG. 3 means a state in which there is no reproduction signal offset, amplitude fluctuation, and reproduction clock phase shift, and the sample value and the reference value stored in the learning table are identical. The difference is zero.

  In FIG. 4, the solid line reproduction signal shows a case where it deviates in the positive direction from the ideal reproduction signal. That is, this is a case where an offset occurs on the positive side. It is assumed that amplitude fluctuation and phase error of the recovered clock have not occurred. As is apparent from the figure, all sample values are obtained by shifting to the positive side from the reference value. That is, all values obtained by subtracting the reference value from the sample value are positive. On the contrary, the broken line reproduction signal is a case where an offset occurs on the negative side. In this case, on the contrary, it can be easily understood that all values obtained by subtracting the reference value from the sample value are negative.

  In FIG. 5, the solid line reproduction signal shows a case where the amplitude is larger than the ideal reproduction signal. It is assumed that there is no phase error between the offset and the recovered clock. In this case, the values obtained by subtracting the reference value from the sample values of 4 to 7 levels that are larger than the vertical axis 0 are all positive, whereas the sample values of 0 to 3 levels that are smaller than the vertical axis 0 are positive. The value obtained by subtracting the reference value from is all negative. Conversely, the broken line reproduction signal is a case where the amplitude is small. In this case, the values obtained by subtracting the reference value from the 4th to 7th level sample values that are larger than the vertical axis 0 are all negative, whereas the 0th to 3rd level sample values that are smaller than the vertical axis 0. All values minus the reference value are positive.

  Further, in FIG. 6, the solid line reproduction signal shows a case where the reproduction clock is shifted to the positive side. It is assumed that the reproduction signal has no offset or amplitude fluctuation. In this case, if the slope of the reproduction signal is positive, the value obtained by subtracting the reference value from the sample value is positive. If the slope of the reproduction signal is negative, the value obtained by subtracting the reference value from the sample value is negative. Conversely, a broken line reproduction signal is a case where the reproduction clock is shifted to the negative side. In this case, if the slope of the reproduction signal is positive, the value obtained by subtracting the reference value from the sample value becomes negative. If the slope of the reproduction signal is negative, the value obtained by subtracting the reference value from the sample value becomes positive.

  As described above, as shown in FIGS. 4 to 6, the value obtained by subtracting the reference value from the sample value is divided into cases and monitored for a predetermined period (for example, a period from several cells to several tens of cells) and integrated. To do. By doing this, it is possible to individually obtain error signals of offset fluctuation, amplitude fluctuation, and reproduction clock shift of the reproduction signal.

  Next, a specific embodiment will be described with reference to the block diagram of FIG. FIG. 7 shows an embodiment of the information reproducing circuit 8 of the optical information recording / reproducing apparatus 1 of FIG.

  The information reproduction circuit 8 shown in FIG. 7 includes a PLL control circuit 12, a reproduction signal sampling circuit 13, a data reproduction circuit 14, a learning data storage unit 15, an arithmetic circuit 16, an error signal storage unit 17, and an error signal determination circuit 18. . Among these, the learning data storage unit 15 constitutes a main part of the storage unit of the present invention, and the arithmetic circuit 16, the error signal storage unit 17, and the error signal determination circuit 18 constitute a main part of the correction unit of the present invention. is doing.

  In FIG. 7, the reproduction signal 11 read by the optical head 5 enters the PLL control circuit 12 and the reproduction signal sampling circuit 13. When the frequency and phase of the reproduction clock are locked while the PLL pull-in pattern (R) is being read, the reproduction clock is supplied to the reproduction signal sampling circuit 13.

  Subsequently, when the learning pattern (S) is input, the reproduction signal sampling circuit 13 samples the learning pattern data by the reproduction clock supplied from the PLL control circuit 12 and sends the learning pattern data to the data reproduction circuit 14. The data reproduction circuit 14 performs processing such as waveform equalization, and stores learning data as learning data indicating the influence of intersymbol interference by the combination of the levels of three consecutive cells as shown in FIG. Stored in the unit 15.

  Subsequently, when the reproduction of the user information (T) starts, similarly, the reproduction signal sampling circuit 13 samples the user information using the reproduction clock supplied from the PLL control circuit 12 and sends it to the data reproduction circuit 14. . In the data reproduction circuit 14, user information is reproduced based on the data in the learning data storage unit 15, and after processing such as code decoding and error correction, the reproduced data 19 thus reproduced is sent to the control circuit 2. send.

  When reproducing the user information, the value of the determined reproduction data level is sent to the arithmetic circuit 16 where the difference from the reference value stored in the learning data storage unit 15 is calculated. The calculated result is sent to the error signal storage unit 17. In the error signal storage unit 17, as described with reference to FIGS. 4 to 6, the calculated results are integrated for each case. For example, the calculation result of 20 cells is temporarily stored, and the integration result is held. Of course, the number of cells to be temporarily stored is an appropriate number depending on the device.

  The accumulated value is sent to the error signal determination circuit 18 where the reproduction signal offset amount, reproduction signal amplitude fluctuation amount, and reproduction clock shift amount are obtained.

  That is, the error signal determination circuit 18 integrates all values obtained by subtracting the reference value from the sample value for a certain period in order to determine the variation in the offset of the reproduction signal and obtain the offset amount (correction value). As a result, when the integrated value is positive, it can be seen that the offset is generated on the positive side, and the magnitude thereof is proportional to the integrated value. On the contrary, when the integrated value is negative, it can be seen that the offset is generated on the negative side, and its magnitude is proportional to the integrated value.

  Further, the error signal determination circuit 18 determines the amplitude fluctuation of the reproduction signal and obtains the amplitude fluctuation amount (correction value), and among the values obtained by subtracting the reference value from the sample value, the value when the reference value is positive is used. A value obtained by integrating for a certain period and a value obtained by integrating a value when the reference value is negative for a certain period are used. From the integrated value of both, if the integrated value in the positive case is positive and the integrated value in the negative case is negative, it can be seen that the amplitude fluctuation occurs on the positive side, and the magnitude is the integrated value. It is proportional to Conversely, if the accumulated value in the positive case is negative and the accumulated value in the negative case is positive, it can be seen that the amplitude fluctuation is on the negative side, and its magnitude is proportional to the accumulated value. It becomes.

  Further, the error signal determination circuit 18 determines a deviation of the reproduction clock and obtains the deviation amount (correction value), and among the values obtained by subtracting the reference value from the sample value, the value when the reproduction signal slope is positive is used. A value obtained by integrating for a certain period and a value obtained by integrating a value when the slope is negative are used. From the integrated value of both, it can be seen that the integrated value when the slope of the playback signal is positive is positive, and the integrated value when the slope is negative is negative, the playback clock shift is on the positive side. The amount of deviation is proportional to the integrated value. Conversely, if the integrated value when the slope of the playback signal is positive is negative and the integrated value when the slope is negative is positive, it can be seen that the playback clock shift is on the negative side. , Which is proportional to the integrated value. In particular, when monitoring the deviation of the regenerative clock, it may be integrated by adopting only the value of the inclination larger than a predetermined magnitude.

  Of the correction values obtained by the error signal determination circuit 18, a correction value related to the amount of deviation of the recovered clock is sent to the PLL control circuit 12. Thereby, the phase shift of the reproduction clock is corrected. The corrected value is sent to the reproduction signal sampling circuit 13. By doing so, it is possible to proceed with the reproduction while sequentially correcting the phase shift of the reproduction clock according to the reproduction data.

  Further, the correction values relating to the offset amount and amplitude variation amount of the reproduction signal are sent to the reproduction signal sampling circuit 13. Thereby, the offset and amplitude of the sampled value are corrected. The corrected value is sent to the data reproduction circuit 14. By doing this, it is possible to proceed with reproduction while correcting offset fluctuation and amplitude fluctuation of the reproduction signal.

  As described above, according to the present embodiment, the reproduction accuracy is improved by correcting the offset variation, amplitude variation, and reproduction clock shift of the reproduction signal from the difference between the sample value and the reference value. Can do.

  The optical information recording / reproducing apparatus 1 and the information reproducing circuit 8 according to the above-described exemplary embodiment are not limited to the configurations of the block diagrams shown in FIGS. 1 and 7, and each means of the present invention. Any device can be applied as long as the function can be realized. For example, the circuit may be configured independently for each block function, or may be configured by integrating a plurality of functions into a single circuit. Moreover, at least a part of each function may be realized by computer processing using a program. The program in this case is included in the scope of rights of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be applied to the use of an optical information recording / reproducing method and apparatus for recording or reproducing information pit levels using three or more values.

1 is a block diagram showing an overall configuration of an optical information recording / reproducing apparatus according to an embodiment of the present invention. It is a figure which shows the learning table obtained by the learning method by the optical information recording / reproducing apparatus which concerns on one Embodiment of this invention. It is a figure explaining an ideal reproduction signal. It is a figure explaining the system which acquires the error signal when the offset by the optical information recording / reproducing apparatus concerning one Embodiment of this invention arises. It is a figure explaining the system which obtains an error signal when the amplitude fluctuation | variation by the optical information recording / reproducing apparatus concerning one Embodiment of this invention arises. It is a figure explaining the system which acquires the error signal when the shift | offset | difference of the reproduction | regeneration clock arises with the optical information recording / reproducing apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the internal structure of the information reproduction circuit used with the optical information recording / reproducing apparatus concerning one Embodiment of this invention. It is a figure explaining the width | variety of the track direction by the difference in the level of a multi-value information pit. It is a figure when a random information pit is recorded with respect to a track | truck, and the figure which shows the relationship between a light spot. It is a figure explaining the parameter of optical simulation. It is a figure explaining the shape of the information pit given by the optical simulation. It is a figure explaining the reproduction signal with respect to the combination of the information pit written in three continuous cells by the calculation result of an optical simulation. It is a figure which shows the amplitude distribution of a cell median value. It is a figure explaining the waveform equalization of 3 taps. It is a figure which shows the amplitude distribution of the cell median after waveform equalization. It is a figure which shows the learning data calculated | required by calculation. It is a figure which shows the program used in FIG. It is a figure explaining the conventional data sequence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical information recording / reproducing apparatus 2 Control circuit 3 Spindle motor 4 Optical disk 5 Optical head 6 Optical head control circuit 7 Information recording circuit 8 Information reproducing circuit 9 Spindle motor controller 10 Interface controller 12 PLL control circuit 13 Reproduction signal sampling circuit 14 Data reproduction Circuit 15 Learning data storage unit 16 Arithmetic circuit 17 Error signal storage unit 18 Error signal determination circuit 20 Track,
21 Information pit 22 Light spot

Claims (14)

On the track of an optical information medium that records and reproduces information using a light spot, virtually spaced cells are provided, and the width of the information pit or the area of the information pit in the track direction is changed for each cell. In an optical information recording / reproducing method for recording and / or reproducing multi-level information of a plurality of levels by making the amplitude of a reproduction signal multistage,
A reproduction value for a combination of adjacent cell levels is obtained by learning, and the reproduction value is stored as a reference value.
When reproducing information, error information of the reproduction signal is detected from the difference between the sample value of the reproduction signal sampled according to the reproduction clock and the reference value, and the phase of the reproduction signal and / or the reproduction clock is based on the error information. An optical information recording / reproducing method characterized by correcting the above.   2. The optical information recording / reproducing method according to claim 1, wherein the error information is information indicating an offset of the reproduction signal.   2. The optical information recording / reproducing method according to claim 1, wherein the error information is information indicating an amplitude variation of the reproduction signal.   2. The optical information recording / reproducing method according to claim 1, wherein the error information is information indicating a phase error of the reproduction clock.   The difference between the reference value and the sample value is integrated for a certain period, an offset of the reproduction signal is determined according to the integration value, and the offset of the reproduction signal is corrected based on the offset amount. Item 3. The optical information recording / reproducing method according to Item 2.   The difference between the reference value and the sample value is integrated for a certain period of time when the amplitude of the reproduction signal is positive and negative, and the amplitude fluctuation of the reproduction signal is determined according to the integrated value of both, 4. The optical information recording / reproducing method according to claim 3, wherein the amplitude fluctuation of the reproduction signal is corrected based on the amplitude fluctuation amount.   The difference between the reference value and the sample value is integrated for a certain period of time when the slope of the reproduction signal is positive and negative, and the phase shift of the reproduction clock is determined according to the integration value of both, 5. The optical information recording / reproducing method according to claim 4, wherein the phase of the reproduction clock is corrected based on the phase shift amount. On the track of an optical information medium that records and reproduces information using a light spot, virtually spaced cells are provided, and the width of the information pit or the area of the information pit in the track direction is changed for each cell. In an optical information recording / reproducing apparatus for recording and / or reproducing multi-level information of a plurality of levels by making the amplitude of a reproduction signal multistage,
A storage means for obtaining a reproduction value for a combination of adjacent cell levels by learning and storing the reproduction value as a reference value;
When reproducing information, error information of the reproduction signal is detected from the difference between the sample value of the reproduction signal sampled according to the reproduction clock and the reference value, and the phase of the reproduction signal and / or the reproduction clock is based on the error information. And an optical information recording / reproducing apparatus.   9. The optical information recording / reproducing apparatus according to claim 8, wherein the error information is information indicating an offset of the reproduction signal.   9. The optical information recording / reproducing apparatus according to claim 8, wherein the error information is information indicating an amplitude variation of the reproduction signal.   9. The optical information recording / reproducing apparatus according to claim 8, wherein the error information is information indicating a phase error of the reproduction clock.   The correction means integrates a difference between the reference value and the sample value for a certain period, determines an offset of the reproduction signal according to the integration value, and corrects the offset of the reproduction signal based on the offset amount. The optical information recording / reproducing apparatus according to claim 9.   The correction means integrates the difference between the reference value and the sample value for a certain period of time when the amplitude of the reproduction signal is positive and negative, and the amplitude of the reproduction signal according to the integrated value of both 11. The optical information recording / reproducing apparatus according to claim 10, wherein the fluctuation is determined, and the amplitude fluctuation of the reproduction signal is corrected based on the amplitude fluctuation amount.   The correction means integrates the difference between the reference value and the sample value for a certain period of time when the slope of the reproduction signal is positive and negative, and the phase of the reproduction clock according to the integration value of both 12. The optical information recording / reproducing apparatus according to claim 11, wherein a deviation amount is determined and the phase of the reproduction clock is corrected based on the phase deviation amount.

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