Information recording / reproducing apparatus and information recording / reproducing method

Abstract

The present invention makes it possible to accurately assess a recorded or unrecorded state, even in a narrow-track state, by assessing a recorded or unrecorded track using the correlation-coefficient relationships among the channels of a divided reproduction-use optical detector.

Description

[Technical Field]

[0001] The present disclosure relates to an information recording / reproducing device and information recording / reproducing method that can correctly determine whether an information recording medium has an information recording surface on which information can be optically recorded, and whether it is in a recorded state or an unrecorded state in order to more stably achieve high-density recording. [Background technology]

[0002] Until now, DVDs, Blu-ray (registered trademark) Discs (hereinafter referred to as BDs), and other information recording media have been used to store video, data, and other information. Recently, BDs have also been used in data archivers, which store important data for the long term in highly reliable systems. Data archivers are primarily sold for business use, and there is a need for even higher density to enable the storage of larger amounts of data.

[0003] There are two types of technologies for improving recording capacity: technology for improving track density and technology for improving linear density.

[0004] One technology for improving track density is land (inter-groove)-groove (groove) recording / reproducing technology. This technology has already been used in DVD-RAM, and improves track density by recording data on both the groove and the land, instead of the conventional method of recording data only on the groove or land. Furthermore, a crosstalk cancellation technology for reducing crosstalk components from adjacent tracks has been disclosed (see Patent Document 1). This technology divides and detects reflected light from an optical disc into multiple regions, and then uses a waveform equalizer to combine the detected multiple playback signals to create a playback signal with predetermined frequency characteristics, while also reducing crosstalk components. This technology makes it possible to further improve track density.

[0005] A common technique for improving linear density is to use PRML (Partial Response Maximum Likelihood) signal processing technology. Furthermore, to ensure stable playback performance using PRML signal processing technology, PLL (Phase Locked Loop) technology, which can handle high linear density, is also used (see Patent Document 2).

[0006] These technologies are being used to improve the recording capacity of optical discs.

[0007] In order to store data on an optical disc, it is necessary to distinguish between recorded and unrecorded tracks. For example, in Patent Document 3, recorded and unrecorded tracks are distinguished by comparing the amplitude of a total light quantity signal, which is proportional to the intensity of reflected light from the optical disc, with a threshold value.

[0008] However, with this technology, in the case of optical discs with improved track density, the crosstalk component from adjacent tracks is large, and even if the track to be identified is unrecorded, the crosstalk from the adjacent tracks appears as a large playback signal amplitude, resulting in the unrecorded track being identified as recorded. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2014 / 057674 [Patent Document 2] International Publication No. 2015 / 107573 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-143175 Summary of the Invention

[0010] The present disclosure provides an information recording / reproducing apparatus and information recording / reproducing method that enable stable discrimination between recorded and unrecorded tracks on an optical disc with improved track density.

[0011] An information recording and reproducing device capable of recording and reproducing information on a track of an information recording medium, comprising: an optical head that irradiates a light beam onto the track and outputs a reproduction signal based on the detected reflected light; a decoding circuit that decodes the recorded information from the reproduction signal; and a recorded / unrecorded discrimination circuit that determines whether the track is in a recorded or unrecorded state.

[0012] The information recording and reproducing device disclosed herein is an information recording and reproducing device that can record and reproduce information on a track of an information recording medium, and includes an optical head that irradiates a light beam onto the track and outputs a reproduction signal based on the detected reflected light, a decoding circuit that decodes the recorded information from the reproduction signal, and a recorded / unrecorded discrimination circuit that determines whether the track is in a recorded or unrecorded state.

[0013] The information recording and reproducing device according to the present disclosure is effective in correctly determining whether a track is in a recorded state or an unrecorded state even for an optical disc with improved track density. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows an information recording / reproducing apparatus according to a first embodiment. [Figure 2] FIG. 1 shows a configuration of an optical head according to a first embodiment. [Figure 3] FIG. 1 is a block diagram showing the configuration of a reproduction signal decoding circuit and a recorded / unrecorded determiner according to a first embodiment. [Figure 4] FIG. 10 is a diagram showing an impulse response waveform of recorded data of a target track in a reproduced waveform; [Figure 5] FIG. 10 is a diagram showing an impulse response waveform of the recorded data on the outer track in a reproduced waveform. [Figure 6] FIG. 10 is a diagram showing an impulse response waveform of the recorded data on the inner track in the reproduced waveform. [Figure 7] A graph showing the detected correlation coefficient values ​​for recorded and unrecorded states DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0016] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0017] (Embodiment 1) 1 is a block diagram showing the configuration of an information recording / reproducing device 100 according to this embodiment. The information recording / reproducing device 100 includes an information recording medium 101 (e.g., an optical disc), an optical head 102, a laser driving circuit 107, a data modulation circuit 108, an error correction encoding circuit 109, a reproduced signal decoding circuit 103, a data demodulation circuit 104, an error correction decoding circuit 105, a system controller 110, and a recorded / unrecorded discrimination circuit 106.

[0018] The information recording and reproducing device 100 records data on the information recording medium 101 in response to a recording request from a host 111. A track is formed spirally from the inner periphery to the outer periphery on the information recording medium 101. The track consists of groove tracks formed by grooves and land tracks formed between adjacent groove tracks. Data is recorded on both the groove tracks and the land tracks.

[0019] The error correction coding circuit 109 adds parity for error correction to the recording data received from the host 111 .

[0020] The data modulation circuit 108 generates a modulated signal by modulating the recording data, including the parity added by the error correction coding circuit 109, in accordance with a predetermined modulation rule.

[0021] The laser driving circuit 107 converts the modulated signal generated by the data modulation circuit into an optical pulse, drives the optical head 102, and irradiates an optical beam based on the optical pulse. A mark is formed on the information recording medium 101 by the heat of the irradiated optical beam. In this way, data is recorded on the information recording medium 101.

[0022] On the other hand, the information recording / reproducing device 100 reproduces data recorded on the information recording medium 101 in response to a reproduction request from the host 111 .

[0023] The optical head 102 irradiates a light beam onto a track on the information recording medium 101 and detects the light reflected from the information recording medium 101. The optical head 102 generates an electrical signal based on the detected reflected light and outputs it as a reproduction signal.

[0024] The reproduced signal decoding circuit 103 decodes the reproduced signal output by the optical head 102 to generate a decoded signal. Specifically, the reproduced signal decoding circuit 103 generates the decoded signal by PRML signal processing. That is, the reproduced signal decoding circuit 103 compares the reproduced signal with an expected waveform, selects the expected waveform that is closest to the reproduced signal, and outputs the data that is the source of the expected waveform as a decoded signal.

[0025] The data demodulation circuit 104 demodulates the recorded data from the decoded signal generated by the reproduction signal decoding circuit 103 in accordance with a predetermined modulation rule.

[0026] The error correction decoding circuit 105 corrects errors in the recording data demodulated by the data demodulation circuit 104, and restores the correct recording data.

[0027] The recorded / unrecorded discrimination circuit 106 discriminates whether a track on the information recording medium 101 is in a recorded state or an unrecorded state.

[0028] 2 is a diagram showing the configuration of optical head 102. As shown in FIG. 2, optical head 102 includes objective lens 201, laser mirror 202, splitting element 203, reproducing photodetector 205, and blue semiconductor laser 206.

[0029] The blue semiconductor laser 206 emits a light beam with a wavelength of 405 nm. The light beam is reflected by the laser mirror 202, and is converged by the objective lens 201, and is then irradiated onto the track of the information recording medium 101.

[0030] The light reflected and diffracted on the track of the information recording medium 101 passes through an objective lens 201 and a laser mirror 202 in that order. A splitting element 203 splits the input light into multiple directions. A reproducing photodetector 205 receives each of the light beams split by the splitting element 203.

[0031] The dividing element 203 functions as a diffraction grating due to the fine grooves formed on its surface. The dividing element 203 has a division pattern 204 that divides the area where reflected light from the information recording medium 101 enters into six areas Ch1 to Ch6. The reflected light that passes through each area is split in different directions by the diffraction grating. The reproducing photodetector 205 has six light-receiving areas that receive each of the six reflected light beams that pass through each area of ​​the dividing element 203 and are split. The reproducing photodetector 205 generates six reproduction signals according to the amount of light received by each light-receiving area. The division pattern 204 is divided into areas Ch5 and Ch6 at both ends in the recording line direction (track direction). The division pattern 204 is also divided into areas Ch1 and Ch2 at the center and areas Ch3 and Ch4 at both ends in the radial direction, which is perpendicular to the recording line direction. Regions Ch1 and Ch2 are located on either side of the center of the dividing element 203 in the radial direction. In other words, regions Ch1 and Ch2 are one and the other regions obtained by dividing the center of the dividing element 203 into left and right halves in the recording line direction. Region Ch3 is located outside and adjacent to region Ch1 in the radial direction. Region Ch4 is located outside and adjacent to region Ch2 in the radial direction. In the following description, the reproduction signal output by the light receiving region of the reproduction photodetector 205 after receiving light that has passed through region Ch1 will be referred to as the reproduction signal of region Ch1. The same applies to reproduction signals from other regions.

[0032] These six reproduction signals generated by the reproduction photodetector 205 are combined in the reproduction signal decoding circuit 103 by performing a predetermined calculation on each reproduction signal, thereby reducing the crosstalk components contained in the reproduction signals and decoding the modulated signal recorded on the target track to generate a decoded signal.

[0033] 3 is a block diagram showing the configuration of the reproduction signal decoding circuit 103 and the recorded / unrecorded discrimination circuit 106. As shown in Fig. 3, the reproduction signal decoding circuit 103 includes an AGC (Auto Gain Control) 301, an A / D converter 302, an FIR (Finite Impulse Response) filter circuit 303, an adder circuit 304, an LMS (Least Mean Square) circuit 306, a Viterbi decoding circuit 305, a phase error detection circuit 307, a loop filter circuit 308, and a VCO (Voltage Controlled Oscillator) circuit 309. There are six AGCs 301, six A / D converters 302, and six FIR filter circuits 303, corresponding to the number of reproduction signals output by the reproduction photodetector 205.

[0034] Each of the AGCs 301 adjusts the amplitude of the six reproduced signals output from the A / D converter 302 so that the reproduced signals have a preset target amplitude.

[0035] Each of the A / D converters 302 converts each of the six reproduction signals generated by the reproduction photodetector 205 into a digital signal.

[0036] Each of the FIR filter circuits 303 performs waveform equalization on each of the six digital signals output from the A / D converter 302 .

[0037] The adder circuit 304 adds the six digital signals output from the FIR filter circuit 303 to synthesize them into one digital signal.

[0038] The Viterbi decoding circuit 305 decodes the recorded modulated signal from the combined digital signal by Viterbi decoding, and outputs the decoded signal.

[0039] The LMS circuit 306 controls the tap coefficients of each of the FIR filter circuits 303. The LMS circuit 306 controls the tap coefficients of each of the FIR filter circuits 303 so as to reduce the error between the expected waveform calculated from the decoded signal by the Viterbi decoding circuit 305 and the digital signal synthesized by the adder circuit 304.

[0040] The FIR filter circuit 303 operates as an adaptive equalization filter, which allows the reproduced signal decoding circuit 103 to synthesize a waveform-equalized digital signal from the six digital signals, reducing crosstalk components and providing frequency characteristics equal to those of the expected waveform.

[0041] The phase error detection circuit 307 detects a phase error value from the digital signal combined by the adder circuit 304 and the decoded signal, relative to the sampling phase of the ideal digital signal in the Viterbi decoding circuit 305. The loop filter circuit 308 converts the detected phase error value into a control signal that controls the frequency of the sampling clock.

[0042] The VCO circuit 309 generates a sampling clock having a frequency corresponding to the control signal output from the loop filter circuit 308. The generated sampling clock is used as a clock indicating the sampling timing of the A / D converter 302 and the operation timing of subsequent circuits.

[0043] With the above configuration, the reproduced signal decoding circuit 103 reduces noise components including crosstalk components from the digital signal, corrects the frequency characteristics of the waveform, and corrects the sampling phase to achieve optimal conditions for the decoding process of the Viterbi decoding circuit 305.

[0044] The recorded / unrecorded discrimination circuit 106 includes correlation coefficient detection circuits 310 , 311 , 312 , 313 and a discrimination circuit 314 .

[0045] The correlation coefficient detection circuit 310 detects the cross-correlation coefficient between the reproduced signal of the region Ch1 and the reproduced signal of the region Ch2 in the division pattern 204 of the dividing element 203.

[0046] The correlation coefficient detection circuit 311 detects the cross-correlation coefficient between the reproduced signal of the region Ch3 and the reproduced signal of the region Ch4 in the division pattern 204 of the dividing element 203.

[0047] The correlation coefficient detection circuit 312 detects the cross-correlation coefficient between the reproduced signal of the region Ch1 and the reproduced signal of the region Ch4 in the division pattern 204 of the dividing element 203.

[0048] The correlation coefficient detection circuit 313 detects the cross-correlation coefficient between the reproduced signal of the region Ch2 and the reproduced signal of the region Ch3 in the division pattern 204 of the dividing element 203.

[0049] A determination circuit 314 compares the cross-correlation coefficients detected by the correlation coefficient detection circuits 310, 311, 312, and 313 with a threshold value to determine whether the track being determined is recorded or unrecorded.

[0050] Fig. 4 is a diagram showing an impulse response waveform to the recorded data of a track to be distinguished, which is included in the reproduced waveform of the track to be distinguished (recorded / unrecorded). Fig. 5 is an impulse response waveform to the recorded data of an outer track, which is included as a crosstalk component in the reproduced waveform of the track to be distinguished (recorded / unrecorded). Fig. 6 is an impulse response waveform to the recorded data of an inner track, which is included as a crosstalk component in the reproduced waveform of the track to be distinguished (recorded / unrecorded).

[0051] The impulse response waveform can be obtained by performing a Fourier transform on the recorded data and the reproduced waveform, dividing the result of the Fourier transform to determine the transfer characteristics from the recorded data to the reproduced waveform, and then performing an inverse Fourier transform on the result of this division.

[0052] From Figures 4 to 6, it can be seen that the impulse responses to the recorded data of the track to be identified are in phase with the reproduced signals in areas Ch1 to Ch6 relative to the recorded data, the impulse responses to the recorded data of the outer tracks, which are crosstalk components, are in anti-phase with the reproduced signals in areas Ch1 and Ch4, and the impulse responses to the recorded data of the inner tracks, which are crosstalk components, are in anti-phase with the reproduced signals in areas Ch2 and Ch3.

[0053] FIG. 7 shows the detection values ​​of the correlation coefficient detection circuits 310, 311, 312, and 313 when the target track, outer track, and inner track are actually recorded (indicated by the symbol “◯”) or unrecorded (indicated by the symbol “-”).

[0054] When the target track is recorded, the amplitude of the impulse response shown in Figure 4 is larger than the amplitude of the crosstalk component impulse response in Figures 5 and 6, and the in-phase impulse response components shown in Figure 4 become dominant, resulting in a positive correlation in the reproduced signal. When the target track is unrecorded and one or both of the inner and outer tracks are recorded, the reproduced signals between the channels become dominantly out-of-phase, and it can be confirmed that the reproduced signal exhibits only a negative correlation, as well as both a positive and a negative correlation. Furthermore, when the target track, inner and outer tracks are all unrecorded, the reproduced signal contains only noise components, resulting in both a positive and a negative correlation.

[0055] Furthermore, since the correlation coefficient is a normalized index, it is an index that is less susceptible to the influence of the AGC 301 in the reproduced signal decoding circuit 103 .

[0056] 7, the detected values ​​of the correlation coefficient detection circuits 310, 311, 312, and 313 are subjected to threshold judgment by the judgment circuit 314, thereby making it possible to distinguish between the recorded and unrecorded states of the target track. Specifically, if there is even one negative correlation, the target track is judged to be unrecorded. If all four correlations are positive, the target track is judged to be recorded if there is a correlation of a specific value (e.g., 0.25) or greater to avoid erroneous detection.

[0057] By using the track recorded / unrecorded discrimination signal obtained from the discrimination circuit 314, it is possible to provide an information recording / reproducing device and an information recording / reproducing method that enable stable discrimination between recorded and unrecorded tracks on optical discs with improved track density. [Industrial Applicability]

[0058] The present disclosure is applicable to an information recording / reproducing device that records and reproduces data on an optical disc. [Explanation of symbols]

[0059] 100 Information recording and reproducing device 101 Information recording media 102 Optical head 103 Regenerative signal decoding circuit 104 Data demodulation circuit 105 Error correction decoding circuit 106 Recorded / unrecorded discrimination circuit 107 Laser driver circuit 108 Data Modulation Circuit 109 Error Correction Encoding Circuit 110 System Controller 111 host 201 Objective Lens 202 Laser mirror 203 Dividing element 204 division patterns 205 Reproducing photodetector 206 Blue semiconductor laser 301 AGC 302 A / D converter 303 FIR filter circuit 304 Addition Circuit 305 Viterbi Decoding Circuit 306 LMS circuit 307 Phase Error Detection Circuit 308 Loop filter circuit 309 VCO circuit 310, 311, 312, 313 Correlation coefficient detection circuit 314 Discrimination circuit

Claims

1. An information recording and reproducing apparatus capable of recording and reproducing information on a track of an information recording medium, comprising: an optical head that irradiates a light beam onto the track and outputs a reproduction signal based on the detected reflected light; a recorded / unrecorded determination circuit for determining whether the track is in a recorded state or an unrecorded state from the reproduced signal, the optical head comprises: a dividing element having a division pattern in which an area where reflected light from the information recording medium enters is divided into at least four areas Ch1 to Ch4; and a photodetector having at least four light-receiving areas that receive each of the at least four reflected light beams that are divided after passing through each of the areas Ch1 to Ch4 of the dividing element; The division pattern is divided into the region Ch1 and the region Ch2 at the center and the region Ch3 and the region Ch4 at both ends in the radial direction, which is a direction perpendicular to the recording line direction, the region Ch1 and the region Ch2 being disposed on both sides of the center of the dividing element in the radial direction, the region Ch3 being disposed adjacent to the region Ch1 outside the region Ch1 in the radial direction, and the region Ch4 being disposed adjacent to the region Ch2 outside the region Ch2 in the radial direction, The photodetector generates at least four reproduction signals in accordance with the amount of light received by the at least four light-receiving regions.

2. The optical head comprises: the splitter element receiving the reflected light and generating a plurality of diffracted light beams in a plurality of diffraction regions; the photodetector receiving the plurality of diffracted beams from the splitting element and outputting a plurality of the reproduction signals based on the light amounts of the respective diffracted beams received, the recorded / unrecorded determination circuit calculates a correlation coefficient between the plurality of reproduced signals and determines whether the track is in a recorded state or an unrecorded state based on the correlation coefficient.

2. An information recording and reproducing apparatus according to claim 1.

3. the recorded / unrecorded determination circuit determines that the track is in a recorded state when the calculated correlation coefficients are all positive.

3. An information recording and reproducing apparatus according to claim 2.

4. An information recording and reproducing method for recording and reproducing information on a track of an information recording medium by an information recording and reproducing device, comprising: The information recording and reproducing device an optical head that irradiates a light beam onto a track of the information recording medium and outputs a reproduction signal based on the detected reflected light; The information recording and reproducing method includes: determining whether the track is in a recorded state or an unrecorded state from the playback signal; the optical head comprises: a dividing element having a division pattern in which an area where reflected light from the information recording medium enters is divided into at least four areas Ch1 to Ch4; and a photodetector having at least four light-receiving areas that receive each of the at least four reflected light beams that are divided after passing through each of the areas Ch1 to Ch4 of the dividing element; The division pattern is divided into the region Ch1 and the region Ch2 at the center and the region Ch3 and the region Ch4 at both ends in the radial direction, which is a direction perpendicular to the recording line direction, the region Ch1 and the region Ch2 being disposed on both sides of the center of the dividing element in the radial direction, the region Ch3 being disposed adjacent to the region Ch1 outside the region Ch1 in the radial direction, and the region Ch4 being disposed adjacent to the region Ch2 outside the region Ch2 in the radial direction, The information recording and reproducing method generates at least four reproduction signals in accordance with the amounts of light received by at least four of the light receiving regions.

5. The optical head comprises: the splitter element receiving the reflected light and generating a plurality of diffracted light beams in a plurality of diffraction regions; the photodetector receiving the plurality of diffracted beams from the splitting element and outputting a plurality of the reproduction signals based on the light amounts of the respective diffracted beams received, The information recording and reproducing method includes: calculating a correlation coefficient between the plurality of reproduction signals; The correlation coefficient is used to determine whether the track is in a recorded state or an unrecorded state.

5. The information recording and reproducing method according to claim 4.

6. and determining that the track is in a recorded state when the calculated correlation coefficients are all positive.

6. The information recording and reproducing method according to claim 5.

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