JP7774201B2 - Information recording/reproducing apparatus and information recording/reproducing method - Google Patents

Description

This disclosure relates to an information recording/reproducing device and information recording/reproducing method that can accurately distinguish between recorded and unrecorded states of an information recording medium having an information recording surface on which information can be optically recorded, in order to more stably achieve high-density recording.

To date, 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 using highly reliable systems. Data archivers are products sold primarily for business use, and there is a need for even higher density to enable the storage of larger amounts of data.

There are two technologies that improve recording capacity: technology that improves track density and technology that improves linear density.

One technology for improving track density is land (inter-groove)-groove (groove) recording and playback technology. This technology is already used in DVD-RAM, and improves track density by recording data that was previously recorded only on the groove or land on both the groove and the land. Furthermore, crosstalk cancellation technology that reduces 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 combines the detected multiple playback signals using a waveform equalizer to create a playback signal with specified frequency characteristics while also reducing crosstalk components. This technology makes it possible to further improve track density.

PRML (Partial Response Maximum Likelihood) signal processing technology is commonly used to improve linear density. 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).

These technologies are intended to improve the recording capacity of optical discs.

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 the total light signal, which is proportional to the intensity of reflected light from the optical disc, with a threshold value.

However, this technology had the problem that, in the case of optical discs with improved track density, the crosstalk component from adjacent tracks was large, and even if the track being identified was unrecorded, the crosstalk from adjacent tracks appeared as a large playback signal amplitude, resulting in the unrecorded track being identified as recorded.

International Publication No. 2014/057674 International Publication No. 2015/107573 JP 2013-143175 A

This disclosure provides an information recording and reproduction device and information recording and reproduction method that enable stable discrimination between recorded and unrecorded tracks on optical discs with improved track density.

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 the track with a light beam 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.

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 is equipped with 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.

The information recording and playback device disclosed herein is effective in accurately determining whether a track is in a recorded or unrecorded state, even for optical discs with improved track density.

FIG. 1 shows an information recording and reproducing apparatus according to a first embodiment. FIG. 1 shows a configuration of an optical head according to a first embodiment. 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. FIG. 10 is a diagram showing an impulse response waveform of recorded data of a target track in a reproduced waveform; FIG. 10 is a diagram showing an impulse response waveform of the recorded data on the outer track in a reproduced waveform. FIG. 10 is a diagram showing an impulse response waveform of the recorded data on the inner track in the reproduced waveform. A graph showing the detected correlation coefficient values for recorded and unrecorded states

The following describes the embodiments in detail, with reference to the drawings as appropriate. However, more detailed explanations than necessary may be omitted. For example, detailed explanations of matters that are already well known or duplicate explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to make it easier for those skilled in the art to understand.

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.

(Embodiment 1)
1 is a block diagram showing the configuration of an information recording and reproducing apparatus 100 according to this embodiment. The information recording and reproducing apparatus 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.

Information recording and playback device 100 records data on information recording medium 101 in response to a recording request from host 111. Tracks are formed spirally on information recording medium 101 from the inner periphery to the outer periphery. The tracks consist 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.

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

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, according to a predetermined modulation rule.

The laser driver circuit 107 converts the modulated signal generated by the data modulation circuit into an optical pulse, drives the optical head 102, and emits an optical beam based on the optical pulse. The heat from the emitted optical beam forms a mark on the information recording medium 101. In this way, data is recorded on the information recording medium 101.

On the other hand, the information recording and playback device 100 plays back data recorded on the information recording medium 101 in response to a playback request from the host 111.

The optical head 102 irradiates a light beam onto a track on the information recording medium 101 and detects the reflected light 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 playback signal.

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 using 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 basis of the expected waveform as a decoded signal.

The data demodulation circuit 104 demodulates the recorded data from the decoded signal generated by the playback signal decoding circuit 103 according to a predetermined modulation rule.

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.

The recorded/unrecorded discrimination circuit 106 determines whether a track on the information recording medium 101 is in a recorded or unrecorded state.

Figure 2 shows the configuration of the optical head 102. As shown in Figure 2, the optical head 102 comprises an objective lens 201, a laser mirror 202, a splitting element 203, a playback photodetector 205, and a blue semiconductor laser 206.

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, focused by the objective lens 201, and irradiated onto the track of the information recording medium 101.

The reflected light reflected and diffracted on the track of the information recording medium 101 passes through the objective lens 201 and then the laser mirror 202. The splitting element 203 splits the input light into multiple directions. The playback photodetector 205 receives each of the light beams split by the splitting element 203.

The dividing element 203 functions as a diffraction grating due to the fine grooves formed on its surface. The dividing element 203 has a dividing 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 reproduction 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 reproduction photodetector 205 generates six reproduction signals according to the amount of light received by each light-receiving area. The dividing pattern 204 is divided into areas Ch5 and Ch6 at both ends in the recording line direction (track direction). Furthermore, the dividing pattern 204 is 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 splitting element 203 in the radial direction. In other words, regions Ch1 and Ch2 are one and the other regions obtained by dividing the central portion of the splitting 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.

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

Figure 3 is a block diagram showing the configuration of the playback signal decoding circuit 103 and the recorded/unrecorded discrimination circuit 106. As shown in Figure 3, the playback 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, each corresponding to the number of playback signals output by the playback photodetector 205.

Each AGC 301 adjusts the amplitude of the six playback signals so that they match the predetermined target amplitude of the playback signal output from the A/D converter 302.

Each A/D converter 302 converts each of the six playback signals generated by the playback photodetector 205 into a digital signal.

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

The addition circuit 304 adds the six digital signals output from the FIR filter circuit 303 and combines them into one digital signal.

The Viterbi decoding circuit 305 decodes the recorded modulated signal from the synthesized digital signal using Viterbi decoding and outputs the decoded signal.

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 obtained from the decoded signal by the Viterbi decoding circuit 305 and the digital signal synthesized by the addition circuit 304.

The FIR filter circuit 303 operates as an adaptive equalization filter. This allows the playback signal decoding circuit 103 to synthesize a waveform-equalized digital signal from the six digital signals, reducing crosstalk components and achieving frequency characteristics equal to the expected waveform.

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

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

With the above configuration, the playback 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 create optimal conditions for the decoding process of the Viterbi decoding circuit 305.

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

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

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

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

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

The discrimination circuit 314 determines whether the track being discriminated is recorded or unrecorded by comparing the cross-correlation coefficient detected by the correlation coefficient detection circuits 310, 311, 312, and 313 with a threshold value.

Figure 4 shows the impulse response waveform for the recorded data of the track to be distinguished, which is included in the playback waveform of the track to be distinguished (recorded/unrecorded). Figure 5 shows the impulse response waveform for the recorded data of the outer track, which is included as a crosstalk component in the playback waveform of the track to be distinguished (recorded/unrecorded). Figure 6 shows the impulse response waveform for the recorded data of the inner track, which is included as a crosstalk component in the playback waveform of the track to be distinguished (recorded/unrecorded).

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 that division.

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.

Figure 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 "-").

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

In addition, since the correlation coefficient is a normalized index, it is an index that is less affected by the AGC 301 in the playback signal decoding circuit 103.

As shown in Figure 7, the detected values of correlation coefficient detection circuits 310, 311, 312, and 313 are subjected to threshold judgment by discrimination circuit 314, 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 determined to be unrecorded. If all four correlations are positive, the target track is determined to be recorded if there is a correlation of a specific value (for example, 0.25) or greater to avoid erroneous detection.

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 information recording/reproducing method that enable stable discrimination between recorded and unrecorded tracks on optical discs with improved track density.

This disclosure is applicable to information recording and playback devices that record and play back data on optical discs.

100 Information recording and reproducing device 101 Information recording medium 102 Optical head 103 Reproduction signal decoding circuit 104 Data demodulation circuit 105 Error correction decoding circuit 106 Recorded/unrecorded discrimination circuit 107 Laser driving circuit 108 Data modulation circuit 109 Error correction coding circuit 110 System controller 111 Host 201 Objective lens 202 Laser mirror 203 Splitting element 204 Split pattern 205 Reproduction photodetector 206 Blue semiconductor laser 301 AGC
302 A/D converter 303 FIR filter circuit 304 Adder 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 (6)

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 . The optical head comprises:
the splitting 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. 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. 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 . The optical head comprises:
the splitting 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. 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.