JP5320567B2 - Reproduction equalization method and reproduction equalization circuit for optical disc - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in the reproduction of an optical disk that although compensation of a reproduction characteristic of an optical system is sufficient provided that lengths of recording marks are equal, the compensation becomes unable to exactly perform for all signals in the case of using a single reproduction equalization method due to the change in length of the mark to be recorded and the occurrence of nonlinear property having different reproduction characteristic according to the length of the mark to be recorded when a high density recording operation of actual data is performed on a super resolution medium, etc. <P>SOLUTION: In the reproduction equalization circuit for detecting one signal of the optical disk, gains of the equalizing circuits are set by separate weights applied for every length of the recording marks to be detected by using two or more equalizing circuits , optimum detection means are provided for every length of the recording mark, and outputs of a plurality of equalizing circuits are combined. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a reproduction equalization method for an optical disc that equalizes the waveform of a signal read from the optical disc. The present invention also relates to a reproduction equalization circuit for processing a signal read from an optical disc.

  In recent years, in order to improve the light beam condensing characteristics, optical discs that realize high-density recording by shortening the wavelength of the laser used or improving the condensing performance of the lens have appeared, Further improvement by these methods is becoming difficult. Therefore, a medium using super-resolution in which the optical characteristics of the medium change nonlinearly with respect to temperature has attracted attention. In an optical disc apparatus for high density recording, a signal output from an optical pickup, that is, a signal read from an optical disc is configured to pass through a reproduction equalization circuit. This reproduction equalization circuit performs signal processing based on a single waveform equalization characteristic or signal processing following the frequency of the reproduction data clock in the same medium.

  In addition, a method of reading in parallel using a plurality of light beams is known. Since five light beams pass through one objective lens in a straight line, the optical characteristics of the five light beams are different. On the other hand, separate equalization circuits are used, and one equalization circuit is used for one reproduction output.

  Furthermore, as a method of using the super-resolution medium, a method of reproducing the super-resolution medium by detecting intersymbol interference and adjusting the reproduction power is known.

  Further, a method for improving the resolution of the main lobe by utilizing optical super-resolution reproduction is known. In these methods, a light-shielding band is provided in the optical system, and only the effect due to the light-shielding band is selected by one equalizer circuit, and a method of combining the super-resolution of the optical system and the equalizer circuit is described.

It is known that a reproducing layer is provided in addition to a recording layer of an optical disc to apply a reproducing power to the reproducing layer, thereby generating a reproducing layer super-resolution action and reading a signal of the recording layer.
Japanese Patent Publication No. 2003-145266 Japanese Patent Publication No. 11-175980 Japanese Patent Publication No. 7-29203 IEICE Journal Vol. 89, no. 11, pp1000-1008,2006

  If the lengths of the recording marks are equal, it is sufficient to compensate for the reproduction characteristics of the optical system. However, when high-density recording is performed on actual data on a super-resolution medium or the like, the length of the mark to be recorded changes, and non-linear characteristics that have different reproduction characteristics depending on the length of the mark to be recorded are generated. There are cases where the circuit cannot correctly reproduce the signal.

  Even if the reproduction power is adjusted so as to improve the reproduction characteristics by detecting the intersymbol interference, two or more characteristics are averaged. There is a problem that the characteristics of the medium cannot be extracted well.

  Even if the equalization circuit is configured to compensate the reproduction optical system, a high-resolution signal can be reproduced on the super-resolution medium, so that the nonlinearity due to the medium has a great influence and the optimum equalization characteristic cannot be determined. There are challenges.

  In order to solve the above-described problems and achieve the object, the reproduction equalization method and reproduction equalization circuit for an optical disc according to the present invention are configured as follows.

The optical disk reproduction equalization method of the present invention performs an equalization process on a reproduction signal obtained by super-resolution reproduction of a plurality of recording marks on an optical disk, and then binarizes a signal corresponding to each recording mark. Reproduction equalization method, wherein a plurality of sets of equalization circuits and detection circuits are used corresponding to recording marks having different lengths, and the reproduction signal is distributed and inputted to the plurality of equalization circuits Each equalization circuit performs waveform shaping processing on the reproduction signal so that a signal having a corresponding recording mark length in the reproduction signal is correctly detected by the corresponding detection circuit. A step of performing binarization processing on the reproduction signal subjected to waveform shaping processing by the equalization circuit so that a signal having a corresponding recording mark length is detected in each detection circuit; Each detection The binarized reproduced signal road, anda step of synthesized to correspond to the reproduction signal before the waveform shaping in the respective detection circuits, binarized reproduced signal after the synthesis A signal having a falling edge or a rising edge within a time limit range set for each detection circuit from the time when the rising edge or the falling edge is detected is detected .
In the reproduction equalization method for optical discs of the present invention, a transversal filter is used for each equalization circuit, and in each equalization circuit, the gain of the tap in the transversal filter is obtained in advance using data obtained in advance. And a signal having a corresponding recording mark length is set so as to be easily detected by a corresponding detection circuit .
In the reproduction equalization method for optical discs according to the present invention, the time limit is set by a timing setting circuit provided for each detection circuit.

An optical disk reproduction equalization circuit according to the present invention performs an equalization process on a reproduction signal obtained by super-resolution reproduction of a plurality of recording marks on an optical disk, and then binarizes a signal corresponding to each recording mark. A reproduction equalization circuit for performing waveform shaping processing on the reproduction signal so that signals corresponding to recording marks of different lengths are correctly detected by the corresponding detection circuit, and the detection the sets of the circuit and multiple comprising, a means for input by distributing the reproduced signal into a plurality of said equalization circuit, said reproduction signal binarized by the respective detection circuits, waveform shaping prior to the reproduction signal Each of the equalizing circuits is configured so that a signal having a corresponding recording mark length in the reproduction signal is correctly detected in the corresponding detection circuit. To perform a waveform shaping process on the reproduced signal, each of said detection circuit, so that the signal having the length of the corresponding recording mark is detected, the binarized reproduced signal after the synthesis It is characterized in that a signal having the next falling or rising edge is detected within a time limit range set for each detection circuit from the time when the rising edge or the falling edge is detected .
In the reproduction equalization circuit for an optical disc according to the present invention, a transversal filter is used for each equalization circuit. In each equalization circuit, the gain of the tap in the transversal filter is obtained in advance from data obtained in advance. And a signal having a corresponding recording mark length is set so as to be easily detected by the corresponding detection circuit .
The reproduction equalization circuit for an optical disk according to the present invention is characterized in that a timing circuit for setting the time limit is provided for each detection circuit .

  With the configuration as described above, the conventional reproduction equalization circuit only compensates for the state of the recorded mark, but it uses medium nonlinearity at the time of reproduction. It becomes possible to compensate for non-linearity due to the difference in the recording mark length, which was impossible to compensate. Therefore, the nonlinear characteristic at the time of reproduction can be compensated according to each recording mark length, and a high-density signal can be reproduced stably.

  By capturing signals from a super-resolution optical disk recorded at high density and combining multiple equalization circuits to combine the nonlinearity of the medium, it is possible to accurately reproduce high-density signals and to store a large amount of data on the optical disk. Realize recording.

FIG. 1 shows a configuration of a circuit for detecting a signal of an optical disc according to the present invention. According to the present invention, the reproduction equalization circuit takes the reproduction signal from the optical head as input 1 and the dividing circuit 10 divides the signal into two or more equalization circuits. The divided signal is shaped by the first equalization circuit 11 so that a short recording mark can be correctly reproduced. Further, the second equalization circuit 12 shapes the signal so that a long recording mark can be correctly reproduced. A signal from the first equalization circuit 11 is input to the first detection circuit 14 and binarized. Similarly, the signal from the second equalization circuit 12 is input to the second detection circuit 16 and binarized. The outputs of the first detection circuit 14 and the second detection circuit 16 are combined by a combining circuit 17. A signal is reproduced as output 2 of the synthesis circuit 17, and a signal from the synthesis circuit 17 is input to the first timing circuit 13 and the second timing circuit 15. The first timing circuit 13 places a time limit on detection so that only the short recording mark is detected. In addition, the second timing circuit 15 detects only a long recording mark, and the second detection circuit 16 sets a time limit so that only a long recording mark can be detected. According to the present invention, in an apparatus for detecting an optical disc signal, a plurality of equalization circuits and a binarization detection circuit are provided for each recording mark length, and the output to be selected is switched depending on the detected mark length. An optical disc reproduction equalization circuit is provided.

  With reference to FIG. 2, the configuration and operation of a super-resolution optical disc as a main object of the present invention will be described. The recording portion of the optical disk is formed by forming a reflective layer 21, a protective layer 22, a reproducing layer 23, a protective layer 24, a recording layer 25, and a protective layer 26 on a substrate 20. First, recording will be described. When the light beam for recording is condensed on the recording portion of the optical disc, the recording layer 25 is heated, whereby a recording mark is formed on the recording layer 25. A good example is a material such as platinum oxide (PtOx) or silver oxide (AgOx) for the recording layer 25.

  During reproduction, the medium is irradiated with a reproduction light beam having a lower power than that during recording. In this way, near-field light is generated at the center of the light beam in the reproducing layer 23 made of silver, indium, antimony, tellurium (AgInSbTe), germanium, antimony, tellurium (GeSbTe), etc., and is recorded on the recording layer 25. It is considered that the signal can be reproduced by causing an interaction with the minute recording mark and changing the output of the reproduction light by the minute recording mark.

FIG. 3 shows the characteristics during reproduction. FIG. 3A shows a condensing state of the light beam 31 incident on the medium surface. At the center of the light beam 31, a minute effective reproduction region 32 on which near-field light from the reproduction layer of the medium acts is formed. Consider a case where the light beam 31 reproduces a recording mark recorded on the recording layer of the medium shown in FIG. In the long recording mark 33 , the reproduction output largely changes from the position where the effective reproduction area 32 is formed with the recording mark. In addition, the reproduction output changes greatly at the end position of the recording mark. On the other hand, in the short recording mark 34 , when the effective reproduction area 32 comes on the recording mark, the reproduction output changes as shown in FIG. Therefore, if the reproduction beam has a positional deviation in the track width direction (up and down direction on the paper surface) with respect to the recording mark, the reproduction waveform obtained by reproducing the long recording mark 33 does not change much, whereas the short recording mark The reproduction waveform obtained by reproducing 34 greatly fluctuates.

As described above, when the reproduction condition changes, the long recording mark 33 and the short recording mark 34 have different reproduction characteristics.

The operation of the circuit for detecting the signal of the present application will be described in detail with reference to FIG. A reproduction signal from the optical head as shown in FIG. 3 is input 1, and the dividing circuit 10 divides the signal into two or more equalization circuits. FIG. 1 shows a case where the division circuit divides the circuit into two. The divided signal is shaped by the first equalization circuit 11 so that a short recording mark can be correctly reproduced. On the other hand, the signal is shaped so that the second equalization circuit 12 can correctly reproduce the long recording mark. Such a the first equalization circuit 11 and the second equalization circuit 12 for the operation, it is possible to use a circuit of about 5 taps combining a delay circuit and a gain multiplier that transversal filters. Two equalization circuits are used separately.

  First, the first equalization circuit 11 is adjusted so as to reduce the interference received from the recording marks before and after recording when the recording mark length is short. In the other second equalization circuit 12, when the recording mark length is long, the interference received from the recording marks before and after recording is adjusted to be small. Each gain multiplier can be adjusted using prior reproduction or gain adjustment data before actual data reproduction.

  In this manner, the first equalization circuit 11 shapes the signal so that the short recording mark is correctly reproduced. Further, the second equalization circuit 12 shapes the signal so that a long recording mark can be correctly reproduced. A signal from the first equalization circuit 11 is input to the first detection circuit 14 and binarized. Similarly, the signal from the second equalization circuit 12 is input to the second detection circuit 16 and binarized.

  In the first detection circuit 14, it is a good example to binarize the signal from the first equalization circuit 11 by discriminating it at a constant level. Note that maximum likelihood determination by the Viterbi algorithm may be used for signal detection. Similarly, in the second detection circuit 16, it is a good example to binarize the signal from the second equalization circuit 12 by discriminating it at a constant level. Further, maximum likelihood determination by the Viterbi algorithm may be used for signal detection.

The outputs of the first detection circuit 14 and the second detection circuit 16 are combined by the combining circuit 17. A signal is reproduced as output 2 of the synthesis circuit 17, and a signal from the synthesis circuit 17 is input to the first timing circuit 13 and the second timing circuit 15. The first timing circuit 13 places a time limit on detection so that only the short recording mark is detected. In addition, the second timing circuit 15 detects only a long recording mark, and the second detection circuit 16 sets a time limit so that only a long recording mark can be detected. As a result, only one signal is extracted from the end of the same recording mark.

  FIG. 1 shows an example in which the image is divided into two, but an example in which recording codes 1 to 1 are recorded as recording marks using recording codes represented by 1 and 0 is shown. In this example, recording is performed from the shortest length m to the longest length n as recording marks, and there are x types of lengths. Therefore, it is a good example to divide the signal into x and use x equalization circuits.

  A good example of splitting the signal into two is shown. It is a good example to use an equalization circuit that detects only the shortest length m and an equalization circuit that detects other lengths.

  Next, an example of dividing into three optimal for high-density signal reproduction will be shown. It is a good example to use an equalization circuit for detecting the shortest length m, an equalization circuit for detecting the next length m + 1, and an equalization circuit for detecting other lengths.

  Furthermore, an example of dividing into four that can suppress the influence of the recording sensitivity at the time of recording will be shown. Separate equalization circuits are used for the two types of signals in the space between the recording marks. That is, an equalization circuit for detecting only the shortest length m of the recording mark, an equalization circuit for detecting the length of the other recording mark, an equalization circuit for detecting only the shortest length m of the space, and the same It is a good example to use an equalization circuit for detecting the length of the space other than the above.

  In addition, an example in which the influence of the recording sensitivity at the time of recording is suppressed and the image is divided into six optimum for high-density signal reproduction will be shown. Separate equalization circuits are used for the two types of signals in the space between the recording marks. That is, an equalization circuit that detects only the shortest length m of a recording mark, an equalization circuit that detects the length m + 1 of the next recording mark, and an equalization circuit that detects the length of other recording marks It is possible to use an equalization circuit that detects only the shortest length m of the space, an equalization circuit that detects the length m + 1 of the next space, and an equalization circuit that detects the length of the other space. A good example.

A reproduction equalization method will be described with reference to FIG. In the reproduction signal division 41, the reproduction signal detected from the optical disc is divided. Next, the gain of the equalization circuit is set for each reproduction signal divided into a plurality of parts. FIG. 4 shows an example of dividing into two. Setting 42 in the gain of the first equalization circuit, for adjusting the gain of the circuit combining a delay circuit and a gain multiplier that transversal filters used in the equalization circuit. Each gain multiplier is adjusted by using prior reproduction or gain adjustment data before reproducing the actual data so that the interference received from the recording marks before and after recording is reduced when the recording mark length is short. . Further, the gain setting 43 of the second equalizer circuit is adjusted so as to reduce the interference received from the recording marks before and after the recording when the recording mark length is long other than when the recording mark length is short.

  In the signal detection 44 in the first detection circuit, the signal from the first equalization circuit is discriminated at a constant level and binarized. Note that maximum likelihood determination by the Viterbi algorithm may be used for signal detection. Similarly, in the signal detection 45 in the second detection circuit, the signal from the second equalization circuit is discriminated at a constant level and binarized. Further, maximum likelihood determination by the Viterbi algorithm may be used for signal detection.

In the step 46 of selecting the output of the first detection circuit or the output of the second detection circuit, the signal from the short recording mark detected by the first detection circuit, that is , the synthesis , based on the detection signal from the synthesis circuit described later. Only a signal that has fallen or risen within a short time interval from the time when the rise or fall in the later binarized reproduction signal is detected is taken out . Similarly, based on the detection signal from the synthesis circuit, the signal from the long recording mark detected by the second detection circuit, that is , the rise or fall in the binarized reproduction signal after synthesis is detected. Only signals that fall or rise during a long time interval are extracted .

In step 47 synthesizes the detection signal in the combining circuit, the output of the first detection circuit and the second detection circuit in Synthesis circuit, the output of the combining circuit is the detection signal. In addition to the output, this detection signal is input to the first timing circuit and the second timing circuit. A time limit is provided for detection by the first detection circuit so that only the short recording mark is detected by the first timing circuit. The second timing circuit 15 is provided with a time limit so that only the long recording mark can be detected by the second detection circuit so that only the long recording mark can be detected. As a result, only one signal is extracted from the end of the same recording mark.

In step 48 of outputting a signal, the output of the synthesis circuit is output as a detection signal.

  FIG. 4 shows an example in which the signal is divided into two. However, in the case where the signal is divided into x pieces, it may be configured so that optimum signal detection can be performed for the signals assigned to each using x equalization circuits.

  A good example of splitting the signal into two is shown. It is a good example to use a process that uses an equalization circuit that detects only the shortest length m and an equalization circuit that detects other lengths.

  Next, an example of dividing into three optimal for high-density signal reproduction will be shown. It is a good example to use a process that uses an equalization circuit that detects the shortest length m, an equalization circuit that detects the next length m + 1, and an equalization circuit that detects other lengths.

  Furthermore, an example of dividing into four that can suppress the influence of the recording sensitivity at the time of recording will be shown. Separate equalization circuits are used for the two types of signals in the space between the recording marks. That is, an equalization circuit for detecting only the shortest length m of the recording mark, an equalization circuit for detecting the length of the other recording mark, an equalization circuit for detecting only the shortest length m of the space, and the same It is a good example to use a process using an equalization circuit for detecting the length of the space other than the above.

  In addition, an example in which the influence of the recording sensitivity at the time of recording is suppressed and the image is divided into six optimum for high-density signal reproduction will be shown. Separate equalization circuits are used for the two types of signals in the space between the recording marks. That is, an equalization circuit that detects only the shortest length m of a recording mark, an equalization circuit that detects the length m + 1 of the next recording mark, and an equalization circuit that detects the length of other recording marks Using an equalization circuit that detects only the shortest length m of the space, an equalization circuit that detects the length m + 1 of the next space, and an equalization circuit that detects the length of the other space A good example is to use.

  In the above embodiment, an example in which the number of divisions is determined in advance is shown. However, the number of divisions with the smallest reproduction error may be selected from the error characteristics of the reproduction signal. In this way, it is possible to suppress characteristic fluctuations due to differences in reproduction conditions.

  As described above, according to the reproduction equalization method and reproduction equalization circuit for an optical disk according to the present invention, a short recording mark and a long recording mark when reproducing a high-density signal using optical nonlinearity are used. The difference in the reproduction characteristics can be optimally detected by using different equalization circuits.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not deviate from a summary. In addition, the embodiments may be appropriately combined as much as possible, and in that case, the combined effect can be obtained. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.

  According to the present invention, the following reproduction equalization method and reproduction equalization circuit for an optical disk can be provided.

  (1) A reproduction equalization method capable of performing optimum reproduction equalization processing on a reproduction signal read from a high-density optical disc.

  (2) A reproduction equalization circuit capable of performing optimum reproduction equalization processing on a reproduction signal read from a high-density optical disc.

The figure which shows the structure of the reproduction | regeneration equalization circuit of this invention Diagram showing the structure of a super-resolution optical disc The figure which shows the reproduction method of the super resolution optical disk The figure which shows the structure of the reproduction | regeneration equalization method of this invention

Explanation of symbols

1 input 2 output 11 first equalization circuit 12 second equalization circuit 13 first timing circuit 14 first detection circuit 15 second timing circuit 16 second detection circuit 17 synthesis circuit 20 substrate 21 reflective layer 22 protective layer 23 reproduction layer 24 Protective layer 25 Recording layer 26 Protective layer 27 Light beam

Claims (6)

An optical disc reproduction equalization method for performing binarization of a signal corresponding to each recording mark after performing equalization processing on a reproduction signal obtained by super-resolution reproduction of a plurality of recording marks on the optical disc,
A plurality of equalization circuits and detection circuits are used corresponding to recording marks of different lengths,
Distributing the reproduction signal to a plurality of the equalization circuits and inputting the reproduction signal;
Each equalizing circuit performing waveform shaping processing on the reproduction signal so that a signal having a corresponding recording mark length in the reproduction signal is correctly detected by the corresponding detection circuit; ,
Performing a binarization process on the reproduction signal waveform- shaped by the equalization circuit so that a signal having a corresponding recording mark length is detected in each detection circuit;
Synthesizing the reproduction signal binarized by each of the detection circuits so as to correspond to the reproduction signal before the waveform shaping ;
Equipped with,
In each of the detection circuits, a signal that has fallen or risen within a time limit set for each detection circuit from the time when the rise or fall in the binarized reproduction signal after detection is detected. A reproduction equalization method for optical discs, characterized in that:   Each equalization circuit uses a transversal filter. In each equalization circuit, the gain of the tap in the transversal filter is calculated using the data acquired in advance, and the length of the corresponding recording mark is set. 2. The reproduction equalization method for an optical disc according to claim 1, wherein the signal is set so that the detected signal is easily detected by a corresponding detection circuit. Setting of the time limit, the optical disk for reproduction equalization method according to claim 1 or 2, characterized in that the timing setting circuit disposed for each of the detection circuit. An optical disc reproduction equalization circuit for performing binarization of a signal corresponding to each recording mark after performing an equalization process on a reproduction signal obtained by super-resolution reproduction of a plurality of recording marks on the optical disc,
In order to correctly detect signals corresponding to recording marks of different lengths in the corresponding detection circuit, a plurality of sets of equalization circuits that perform waveform shaping processing on the reproduction signal and the detection circuits are provided. ,
Means for distributing and inputting the reproduction signal to the plurality of equalization circuits;
Means for synthesizing the reproduction signal binarized by each of the detection circuits so as to correspond to the reproduction signal before waveform shaping ;
Each of the equalization circuits performs waveform shaping processing on the reproduction signal so that a signal having a corresponding recording mark length in the reproduction signal is correctly detected in the corresponding detection circuit,
Each of the detection circuits is connected to each detection circuit from the time when a rising or falling edge in the binarized reproduction signal after the synthesis is detected so that a signal having a corresponding recording mark length is detected. Detect the signal that had the next falling or rising edge within the time limit set in
A reproduction equalization circuit for an optical disc characterized by the above. Each of the equalization circuits uses a transversal filter, and in each of the equalization circuits, the gain of the tap in the transversal filter uses the data acquired in advance to calculate the length of the corresponding recording mark. 5. The reproduction equalization circuit for an optical disk according to claim 4 , wherein the signal is set so as to be easily detected by a corresponding detection circuit. 6. The optical disc reproduction equalization circuit according to claim 4, further comprising a timing circuit for setting the time limit for each detection circuit.

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