JP6036798B2 - Data detection device, playback device, and data detection method - Google Patents

Description

  The present invention relates to a data detection device, a playback device, and a data detection method, and more particularly to a technique for canceling crosstalk from adjacent tracks.

Japanese Patent No. 3225611 Japanese Patent No. 2601174 Japanese Patent No. 4184585 JP 2008-108325 A

  In a reproducing apparatus for a recording medium such as an optical disk, there is a problem of deterioration of a reproduced signal due to crosstalk from another adjacent track, and there is a technique of a crosstalk canceller for improving this problem.

For example, in the above-mentioned Patent Document 1, in a CAV (Constant-Angular-Velocity) disk, the playback signals of three tracks synchronized in the radial direction of the disk using a memory or a delay element (that is, the playback track and its adjacent track) A technique for reducing crosstalk between tracks by applying an appropriate coefficient to a reproduction signal of a track) and adding the signals is shown.
In Patent Document 2 and Patent Document 3, there is a technique for automatically synchronizing the phase difference between the reproduction signals for three tracks obtained from the three-beam optical head with sufficient accuracy necessary for crosstalk calculation. It is shown.
In Patent Document 4, a memory for storing reproduction signals of two or more tracks is provided, which is synchronized by a correlation calculator and a phase interpolator (phase adjuster), and further passed through an appropriate filter to cross-talk signals. A technique for canceling crosstalk of a main reproduction signal by calculating a replica is shown.

In general, in order to perform crosstalk cancellation with high accuracy, the following (1) and (2) are problems.
(1) Synchronization of reproduction signal of adjacent (or adjacent) track with channel clock accuracy (2) Reproduction of frequency characteristics of crosstalk from adjacent (or adjacent) track to main reproduction track (that is, generation of crosstalk signal)

The prior arts described in Patent Documents 1 to 4 are all techniques for effectively canceling crosstalk. However, in Patent Document 1, the implementation is limited to a CAV disk.
In Patent Documents 2 and 3, the implementation is limited to an apparatus having a three-beam reproduction pickup.
In addition, in common with Patent Documents 1, 2, and 3, since the above (2) is not considered, sufficient effects may not be obtained.
On the other hand, in the technique of Patent Document 4, the viewpoints (1) and (2) are considered, but a high-accuracy phase error detection circuit and a phase synchronization circuit of one clock or less are provided in the previous stage of the crosstalk canceller. This is necessary and has created implementation complexity.

  It is an object of the present invention to perform reproduction data detection by performing accurate crosstalk cancellation corresponding to dynamic crosstalk component fluctuations with a simple configuration.

The data detection apparatus according to the present invention provides a reproduction information signal read from a recording medium, a reproduction information signal from a target track as a data detection target, and the target that becomes a crosstalk component with respect to the reproduction information signal from the target track. A reproduction information signal from N tracks on the inner circumference side of the track, and a reproduction information signal from M tracks on the outer circumference side of the target track, which are crosstalk components with respect to the reproduction information signal from the target track, Each of the reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the reproduction information signal from the M tracks on the outer circumference side are channel a memory unit to be read in a state of coarse synchronization with a coarse precision of synchronization state than the clock accuracy is read out at each time point from the memory unit As the reproduction information signal, the first adaptive equalizer unit to which the reproduction information signal from the target track is input and the respective reproduction information signals from the N tracks on the inner peripheral side which are roughly synchronized with the target track are input. N second adaptive equalizer units, and M third adaptive equalizer units to which respective reproduction information signals from the M tracks on the outer peripheral side roughly synchronized with the target track are input. A multi-input adaptive equalizer unit that calculates the output of each of the first, second, and third adaptive equalizer units and outputs it as an equalized signal, and binarizes the equalized signal of the multi-input adaptive equalizer unit A binarization unit for performing processing to obtain binary data, an equalization target signal obtained based on the binary detection result of the binarization unit, and an output from the multi-input adaptive equalizer unit An equalization error calculation unit that obtains an equalization error from the equalization signal and supplies the equalization error as a tap coefficient control signal for adaptive equalization to each of the adaptive equalizer units. In the adaptive equalizer unit, adaptive equalization corresponding to the binarization processing is performed by the tap coefficient calculation using the equalization error, and in each of the second and third adaptive equalizer units, the equalization error is used. With the tap coefficient calculation, the reproduction information signal from the N tracks on the inner circumference side and the reproduction information signal from the M tracks on the outer circumference side between the reproduction information signal from the target track and the reproduction information signal from the target track, respectively. Adaptive equalization for correcting the phase error is performed.
Further, the memory unit, based on the rotation synchronization signal of the recording medium, reproduces the reproduction information signal from the target track, reproduction information signals from the N tracks on the inner circumference side, and M on the outer circumference side. By reading out the reproduction information signals from the tracks, the reproduction information signals from the target track, the reproduction information signals from the N tracks on the inner circumference side, and the M tracks on the outer circumference side are read out. The reproduction information signal is input to the multi-input adaptive equalizer section in a coarsely synchronized state.
In addition, the phase difference of each reproduction information signal read from the memory unit and input to the plurality of adaptive equalizer units is detected, and the timing of reading each reproduction information signal from the memory unit based on the detected phase difference And a phase difference detection unit that outputs a correction signal for the correction.
The multi-input adaptive equalizer unit includes the first adaptive equalizer unit, one second adaptive equalizer unit, and one third adaptive equalizer unit, and the second adaptive equalizer unit. Is supplied with a reproduction information signal from a track on the inner circumference side of the target track, and a reproduction information signal from a track on the outer circumference side of the target track is inputted to the third adaptive equalizer unit.
The multi-input adaptive equalizer unit performs a partial response equalization process on the reproduction information signal from the target track, and the binarization unit performs a binarization process on the equalized signal of the multi-input adaptive equalizer unit. A maximum likelihood decoding process is performed, and the equalization error calculation unit is an equalization target signal obtained by convolution processing of the binary detection result by the maximum likelihood decoding, and an equalized signal output from the multi-input adaptive equalizer unit The equalization error is obtained by calculation using and.

  The reproducing apparatus of the present invention includes a head unit for reading information from a recording medium, a multi-input adaptive equalizer unit, a binarizing unit, an equalization error calculating unit, and the binarizing unit constituting the data detecting device of the present invention. And a demodulator that demodulates the reproduction data from the binary data obtained in (1).

In the data detection method of the present invention, as a reproduction information signal read from a recording medium, a reproduction information signal from a target track that is a data detection target and the target that becomes a crosstalk component with respect to the reproduction information signal from the target track A reproduction information signal from N tracks on the inner circumference side of the track, and a reproduction information signal from M tracks on the outer circumference side of the target track, which are crosstalk components with respect to the reproduction information signal from the target track, Are stored in the memory unit, and from the memory unit, the reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the M information from the M tracks on the outer circumference side are stored. a reproduction information signal, read out in a state of coarse synchronization in a synchronous state of coarser granularity than the channel clock accuracy, read out at each time point from the memory unit As a reproduction information signal to be reproduced, a reproduction information signal from the target track is input to a first adaptive equalizer unit, and each reproduction information signal from the N tracks on the inner peripheral side roughly synchronized with the target track is represented by N Are input to the second adaptive equalizer units, and the respective reproduction information signals from the M tracks on the outer peripheral side that are roughly synchronized with the target track are input to the M third adaptive equalizer units. The outputs of the first, second, and third adaptive equalizer units are calculated and output as equalized signals, and binarization processing is performed on the equalized signals to obtain binary data. Tap coefficient control for adaptive equalization of each adaptive equalizer unit is performed using an equalization error between the equalization target signal and the equalization signal obtained based on the binary detection result. In the first adaptive equalizer unit, adaptive equalization corresponding to the binarization processing is performed by calculating a tap coefficient using the equalization error, and in each of the second and third adaptive equalizer units, the above equalization is performed. With the tap coefficient calculation using the conversion error, the reproduction information signal from the N tracks on the inner circumference side and the reproduction information signal from the M tracks on the outer circumference side are compared with the reproduction information signal from the target track. This is a data detection method for performing adaptive equalization to correct each phase error.

In the present invention, the crosstalk component from the adjacent track at the time of reproduction is reduced by the multi-input adaptive equalizer unit, an optimum reproduction signal is obtained, and the reproduction performance is improved.
In the multi-input adaptive equalizer unit, crosstalk cancellation is performed by using both phase and amplitude characteristic optimization functions of each adaptive equalizer unit.
That is, the adaptive equalizer unit to which the reproduction information signal from the target track is input optimizes the error and phase distortion of the input signal frequency component of the reproduction information signal. Tap coefficient control for optimization is performed using an equalization error between the equalization target signal and the equalization signal.
On the other hand, in the adaptive equalizer unit to which the reproduction information signals from the adjacent tracks on the inner and outer peripheral sides are input, the equalization target signal is uncorrelated with the adjacent track signal input to the adaptive equalizer unit. For this reason, when the tap coefficient control is performed using the equalization error in the adaptive equalizer unit, a signal for canceling the crosstalk component can be obtained as the output. Therefore, by calculating the output of each adaptive equalizer unit, an equalized signal with crosstalk canceled can be obtained.
As a result, it is possible to cancel the crosstalk that can follow the dynamic crosstalk component while reducing the phase error detection and the phase adjustment that are conventionally required.

  According to the present invention, with a relatively simple configuration, it is possible to remove the crosstalk component of the adjacent track from the reproduction information signal with very high accuracy, and the reproduction data detection capability can be improved. In particular, a significant improvement in reproduction performance can be realized at the time of high density recording or narrow track pitch recording at which deterioration due to crosstalk from adjacent tracks tends to become serious.

1 is a block diagram of a disk drive device according to an embodiment of the present invention. It is a block diagram of a data detection processing unit of the first embodiment. It is a block diagram of the multi-input adaptive equalizer part of embodiment. It is a block diagram of the adaptive equalizer unit of an embodiment. It is a block diagram of the equalization error calculator of an embodiment. It is explanatory drawing of the effect by the crosstalk cancellation of embodiment. It is explanatory drawing of the tap coefficient of the adaptive equalizer unit of embodiment. It is a block diagram of the data detection process part of 2nd Embodiment. It is a block diagram of the data detection process part of 3rd Embodiment.

Embodiments of the present invention will be described below. In the embodiment, a disk drive device that performs recording / reproduction on an optical disk is given as an example of the playback device of the present invention, and a data detection processing unit provided in the disk drive device is given as an example of a data detection device. The first to third embodiments differ in the configuration of the data detection processing unit.
The description will be given in the following order.
<1. Configuration of disk drive device>
<2. Data Detection Processing Unit of First Embodiment>
<3. Data Detection Processing Unit of Second Embodiment>
<4. Data Detection Processing Unit of Third Embodiment>
<5. Modification>

<1. Configuration of disk drive device>

The configuration of the disk drive device of this embodiment will be described with reference to FIG.
The disk drive device according to the present embodiment includes a CD (Compact Disc), a DVD (Digital Versatile Disc), a Blu-ray Disc (Blu-ray Disc (registered trademark)), a read-only disc or a recordable type as a next generation disc, etc. It is assumed that playback and recording can be performed in correspondence with a disc (a write-once disc or a rewritable disc).

For example, in the case of a recordable type Blu-ray disc, recording / reproduction of a phase change mark (phase change mark) or a dye change mark is performed under the condition of a combination of a laser having a wavelength of 405 nm (so-called blue laser) and an objective lens having an NA of 0.85. Recording / reproduction is performed by using a data block of 64 KB (kilobytes) as one recording / reproduction unit (RUB) at a track pitch of 0.32 μm and a linear density of 0.12 μm / bit.
As for the read-only disc, read-only data is recorded by embossed pits having a depth of about λ / 4. Similarly, the track pitch is 0.32 μm and the linear density is 0.12 μm / bit. A 64 KB data block is handled as one reproduction unit (RUB).

The RUB, which is a recording / playback unit, is a total of 498 frames generated by adding a link area of one frame before and after, for example, an ECC block (cluster) of 156 symbols × 496 frames.
In the case of a recordable disc, a groove (groove) is formed on the disc by meandering (wobbling), and this wobbling groove is used as a recording / reproducing track. Groove wobbling includes so-called ADIP (Address in Pregroove) data. In other words, the address on the disk can be obtained by detecting the wobbling information of the groove.

In the case of a recordable disc, a recording mark by a phase change mark is recorded on a track formed by a wobbling groove. The phase change mark is an RLL (1, 7) PP modulation method (RLL; Run Length Limited, PP). : Parity preserve / Prohibit rmtr (repeated minimum transition runlength)), etc., with linear densities of 0.12 μm / bit and 0.08 μm / ch bit.
When the channel clock period is “T”, the mark length is 2T to 8T.
In the case of a read-only disc, no groove is formed, but similarly data modulated by the RLL (1, 7) PP modulation method is recorded as an embossed pit row.

Such a Blu-ray disc or an optical disc 90 such as a DVD is loaded on a turntable (not shown) when loaded in a disc drive device, and is subjected to a constant linear velocity (CLV) or a constant angular velocity by a spindle motor 2 during a recording / reproducing operation. It is rotationally driven by (CAV).
During reproduction, the mark information recorded on the track on the optical disk 90 is read by the optical pickup (optical head) 1.
When data is recorded on the optical disc 90, user data is recorded as a phase change mark or a dye change mark on a track on the optical disc 90 by the optical pickup 1.

In the inner peripheral area 91 of the optical disc 90, for example, physical information of the disc is recorded as embossed pits or wobbling grooves as reproduction-only management information, and the information is also read out by the optical pickup 1.
For further optical disk 90, the reading of the ADIP information embedded as wobbling of the groove track on the optical disc 90 by the optical pickup 1 also performed.

In the optical pickup 1, a laser diode serving as a laser light source, a photodetector for detecting reflected light, an objective lens serving as an output end of the laser light, a disk recording surface is irradiated with laser light, and An optical system or the like for guiding the reflected light to the photodetector is formed.
In the optical pickup 1, the objective lens is held so as to be movable in the tracking direction and the focus direction by a biaxial mechanism.
The entire optical pickup 1 can be moved in the radial direction of the disk by a thread mechanism 3.
The laser diode in the optical pickup 1 is driven to emit laser light when a drive current is passed by the laser driver 13.

Reflected light information from the optical disc 90 is detected by the photodetector is supplied to a matrix circuit 4 is an electric signal corresponding to the amount of received light.
The matrix circuit 4 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as photodetectors, and generates necessary signals by matrix calculation processing.
For example, a reproduction information signal (RF signal) corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, and the like are generated.
Further, a push-pull signal is generated as a signal related to groove wobbling, that is, a signal for detecting wobbling.
The reproduction information signal output from the matrix circuit 4 is supplied to the data detection processing unit 5, the focus error signal and tracking error signal are supplied to the optical block servo circuit 11, and the push-pull signal is supplied to the wobble signal processing circuit 6 , respectively.

The data detection processing unit 5 performs binarization processing of the reproduction information signal.
For example, the data detection processing unit 5 performs an A / D conversion process on the RF signal, a reproduction clock generation process using a PLL, a PR (Partial Response) equalization process, a Viterbi decoding (maximum likelihood decoding), and the like, and a partial response maximum likelihood decoding process A binary data string is obtained by (PRML detection method: Partial Response Maximum Likelihood detection method). Details will be described later.
Then, the data detection processing unit 5 supplies a binary data string as information read from the optical disc 90 to the subsequent encoding / decoding unit 7.

The encode / decode unit 7 performs demodulation of reproduction data during reproduction and modulation processing of recording data during recording. That is, data demodulation, deinterleaving, ECC decoding, address decoding, etc. are performed during reproduction, and ECC encoding, interleaving, data modulation, etc. are performed during recording.
At the time of reproduction, the binary data string decoded by the data detection processing unit 5 is supplied to the encoding / decoding unit 7. The encoding / decoding unit 7 performs demodulation processing on the binary data string to obtain reproduction data from the optical disc 90. That is, for example, demodulation processing for data recorded on the optical disc 90 after run-length limited code modulation such as RLL (1, 7) PP modulation and ECC decoding processing for error correction are performed, and then the optical disc 90 is processed. Get the playback data from.
The data decoded to the reproduction data by the encoding / decoding unit 7 is transferred to the host interface 8 and transferred to the host device 100 based on an instruction from the system controller 10. The host device 100 is, for example, a computer device or an AV (Audio-Visual) system device.

At the time of recording / reproducing with respect to the optical disc 90, processing of ADIP information is performed.
That is, the push-pull signal output from the matrix circuit 4 as a signal related to groove wobbling is converted into wobble data digitized by the wobble signal processing circuit 6. A clock synchronized with the push-pull signal is generated by the PLL process.
The wobble data is demodulated by the ADIP demodulating circuit 16 into a data stream constituting an ADIP address and supplied to the address decoder 9.
The address decoder 9 decodes the supplied data, obtains an address value, and supplies it to the system controller 10.

At the time of recording, recording data is transferred from the host device 100 , and the recording data is supplied to the encoding / decoding unit 7 via the host interface 8.
In this case, the encoding / decoding unit 7 performs error correction code addition (ECC encoding), interleaving, sub-code addition, and the like as recording data encoding processing. Further, the run-length limited code modulation such as RLL (1-7) PP method is applied to the data subjected to these processes.

  The recording data processed by the encoding / decoding unit 7 is supplied to the write strategy unit 14. In the write strategy section, as a recording compensation process, laser drive pulse waveform adjustment is performed with respect to the characteristics of the recording layer, the spot shape of the laser beam, the recording linear velocity, and the like. Then, the laser drive pulse is output to the laser driver 13.

Based on the laser driving pulse subjected to the recording compensation process, the laser driver 13 causes a current to flow through the laser diode in the optical pickup 1 to execute laser light emission driving. As a result, a mark corresponding to the recording data is formed on the optical disc 90.
The laser driver 13 includes a so-called APC circuit (Auto Power Control), and the laser output depends on temperature or the like while monitoring the laser output power by the output of the laser power monitoring detector provided in the optical pickup 1. Control to be constant.
The target value of the laser output at the time of recording and reproduction is given from the system controller 10, and control is performed so that the laser output level becomes the target value at the time of recording and reproduction.

The optical block servo circuit 11 generates various servo drive signals for focus, tracking, and thread from the focus error signal and tracking error signal from the matrix circuit 4 and executes the servo operation.
That is, a focus drive signal and a tracking drive signal are generated according to the focus error signal and the tracking error signal, and the biaxial driver 18 drives the focus coil and tracking coil of the biaxial mechanism in the optical pickup 1. Thus, a tracking servo loop and a focus servo loop are formed by the optical pickup 1, the matrix circuit 4, the optical block servo circuit 11, the biaxial driver 18, and the biaxial mechanism.
The optical block servo circuit 11 turns off the tracking servo loop in response to a track jump command from the system controller 10 and outputs a jump drive signal to execute a track jump operation.
Further, the optical block servo circuit 11, a sled error signal obtained as a low-frequency component of the tracking error signal, based on access execution control from the system controller 10 generates a sled drive signal, the sled mechanism 3 by the thread driver 15 To drive. The sled mechanism 3, although not shown, a main shaft for holding the optical pickup 1, a sled motor, a mechanism by transmission gears, etc., by driving the sled motor according to the sled drive signal of the optical pickup 1 The slide movement is performed.

The spindle servo circuit 12 performs control to rotate the spindle motor 2 at CLV.
The spindle servo circuit 12 obtains the clock generated by the PLL processing for the wobble signal as the current rotational speed information of the spindle motor 2, and compares it with predetermined CLV reference speed information to generate a spindle error signal. .
Further, at the time of data reproduction, the reproduction clock generated by the PLL in the data signal processing circuit 5 becomes the current rotational speed information of the spindle motor 2, so that the spindle is compared with predetermined CLV reference speed information. An error signal can also be generated.
The spindle servo circuit 12 outputs a spindle drive signal generated according to the spindle error signal, and causes the spindle driver 17 to execute CLV rotation of the spindle motor 2.
Further, the spindle servo circuit 12 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 10, and also executes operations such as starting, stopping, acceleration, and deceleration of the spindle motor 2.
The spindle motor 2 is provided with, for example, FG (Freqency Generator) and PG (Pulse Generator), and the output is supplied to the system controller 10. Thereby, the system controller 10 can recognize the rotation information (rotation speed, rotation angle position) of the spindle motor 2.

Various operations of the servo system and the recording / reproducing system as described above are controlled by a system controller 10 formed by a microcomputer.
The system controller 10 executes various processes in accordance with commands from the host device 100 given via the host interface 8.
For example, when a write command (write command) is issued from the host device 100 , the system controller 10 first moves the optical pickup 1 to an address to be written. Then, the encoding / decoding unit 7 causes the encoding process to be performed on the data (for example, video data, audio data, etc.) transferred from the host device 100 as described above. Recording is executed by the laser driver 13 driving to emit laser light according to the data encoded as described above.

Further, for example, when a read command for requesting transfer of certain data recorded on the optical disc 90 is supplied from the host device 100 , the system controller 10 first performs seek operation control for the instructed address. That is, a command is issued to the optical block servo circuit 11, and the access operation of the optical pickup 1 targeting the address specified by the seek command is executed.
Thereafter, operation control necessary for transferring the data in the designated data section to the host device 100 is performed. That performs data reading from the optical disc 90, to execute the reproduction processing in the data detection processing unit 5, the encoding / decoding unit 7, and transfers the requested data.

Although the example of FIG. 1 has been described as a disk drive device connected to the host device 100 , the disk drive device may not be connected to other devices. In this case, an operation unit and a display unit are provided, and the configuration of the interface part for data input / output is different from that in FIG. That is, it is only necessary that recording and reproduction are performed in accordance with a user operation and a terminal unit for inputting / outputting various data is formed. Of course, various other configuration examples of the disk drive device are possible.

<2. Data Detection Processing Unit of First Embodiment>

The configuration of the data detection processing unit 5 as the first embodiment is shown in FIG.
As described above, the data detection processing unit 5 performs binarization processing of the reproduction information signal supplied from the matrix circuit 4.
As shown in FIG. 2, the data detection processing unit 5 includes a multi-input adaptive equalizer unit 51, a binarization detector 52, a PR convolution unit 53, an equalization error calculator 54, a memory 55, an A / D converter 56, A PLL circuit 57 and a memory controller 58 are provided.

The reproduction information signal supplied from the matrix circuit 4 is converted into digital data by the A / D converter 56.
The reproduction information signal converted into digital data by the A / D converter 56 is supplied to the PLL circuit 57, and a reproduction clock is generated by PLL processing. The regenerated clock is used as a sampling clock for the A / D converter 56, and is used as a clock for processing of each circuit unit in the subsequent stage (not shown).

In the case of the present embodiment, the reproduction information signal output from the A / D converter 56 is stored in the memory 55.
The reproduction information signal stored in the memory 55 is read based on the read address ad from the memory controller 58 and supplied to the multi-input adaptive equalizer unit 51.
The memory controller 58 is supplied with a disk rotation synchronization signal SR. This is, for example, a signal supplied from the system controller 10 on the basis of the FG pulse or PG pulses of the spindle motor 2, a signal indicating the rotation angle of the optical disc 90 (rotation phase).

The memory controller 58 supplies the read address ad based on the disk rotation synchronization signal SR, so that the memory 55 reads the reproduction information signal read from the target track to be binarized at each time point, and Reproduction information signals from two adjacent tracks adjacent to the target track are simultaneously read out.
The two adjacent tracks are a track on the inner circumference side of the track by one track and a track on the outer circumference side of the disc by one track from the target track at that time. That is, the reproduction information signals from two adjacent tracks are reproduction information signals that become crosstalk components with respect to the reproduction information signal of the current target track.
In FIG. 2, the reproduction information signal of the target track read from the memory 55 is shown as a reproduction information signal Stk0, and the reproduction information signals of two adjacent tracks are shown as reproduction information signals Stk + and Stk−. For example, the reproduction information signal Stk + is a reproduction information signal for a track adjacent to the outer peripheral side, and the reproduction information signal Stk− is a reproduction information signal for a track adjacent to the inner peripheral side.

Since the reproduction information signals Stk + and Stk− are reproduction information signals serving as crosstalk components, when the laser spot from the optical pickup 1 is applied to the pit row (or mark row) of the target track, it is adjacent to both sides. A reproduction information signal from the pit row (or mark row) of the track to be played is used.
In this example, the reproduction information signals Stk + and Stk− of both adjacent pit strings are obtained simultaneously when the reproduction information signal Stk0 of the pit string of the target track to be processed is binarized. Therefore, the reproduction information signal from the A / D converter 56 is temporarily stored in the memory 55. Then, read out by coarsely synchronized state to the rotation phase of the optical disc 90.

From the memory 55, when the reproduction scanning by the laser spot in the optical pickup 1 proceeds to one outer track from the target track and the reproduction information signal of the outer track is stored in the memory 55, The reproduction information signals Stk0, Stk +, Stk− can be read out. That is, if the reproduction information signal stored at a certain time is the reproduction information signal Stk +, the reproduction information signal one round before is set as the reproduction information signal Stk0 of the target track, and the reproduction information signal before the two rounds is set as the reproduction information signal Stk−. Read it out. Such reading is controlled by the memory controller 58.
Since the reproduction information signals Stk + and Stk− are signals for canceling the crosstalk with respect to the reproduction information signal Stk0, it is originally important that the rotation phase (rotation angle position) is synchronized with high accuracy. It is. That is, it is important that the information is information on adjacent pit rows that are actually crosstalk components. However, in the case of the present embodiment, the reproduction information signals Stk + and Stk− are accurate to, for example, several tens of clocks with respect to the reproduction information signal Stk0 by performing crosstalk cancellation by the processing of the multi-input adaptive equalizer unit 51 as will be described later. As long as the synchronization state is as low as possible.

  The multi-input adaptive equalizer unit 51 performs PR adaptive equalization processing on the reproduction information signal Stk0. That is, the reproduction information signal Stk0 is equalized so as to approximate the target PR waveform. The multi-input adaptive equalizer unit 51 also performs adaptive equalization processing on the reproduction information signals Stk + and Stk− at the same time. Then, each equalized output is calculated and an equalized signal y0 is output.

The binarization detector 52 is, for example, a Viterbi decoder, and performs maximum likelihood decoding on the PR equalized signal y0 to obtain binarized data DT. The binarized data DT is supplied to the encoding / decoding unit 7 shown in FIG. 1 and reproduction data demodulation processing is performed.
The PR convolution unit 53 performs a convolution process on the binarization result to generate a target signal Zk. This target signal Zk is an ideal signal without noise since it is a convolution of the binary detection result.
The equalization error calculator 54 obtains an equalization error ek from the equalization signal y0 from the multi-input adaptive equalizer unit 51 and the target signal Zk, and controls the tap error control of the equalization error ek to the multi-input adaptive equalizer unit 51. Supply for.
FIG. 5 shows a configuration example of the equalization error calculator 54. The equalization error calculator 54 includes a subtracter 90 and a coefficient multiplier 91. The subtracter 90 subtracts the target signal Zk from the equalized signal y0. An equalization error ek is generated by multiplying the subtraction result by a predetermined coefficient by the coefficient multiplier 91.

The configuration of the multi-input adaptive equalizer unit 51 is shown in FIG.
The multi-input adaptive equalizer unit 51 includes adaptive equalizer units 71, 72, 73 and an adder 74.
The reproduction information signal Stk0 is input to the adaptive equalizer unit 72, the reproduction information signal Stk + is input to the adaptive equalizer unit 71, and the reproduction information signal Stk− is input to the adaptive equalizer unit 73.
Each of the adaptive equalizer units 71, 72, 73 has parameters of the number of FIR filter taps, its calculation accuracy (bit resolution), and the update gain of the adaptive calculation, and an optimum value is set for each.
Each of the adaptive equalizer units 71, 72, 73 is supplied with an equalization error ek as a coefficient control value for adaptive control.

The outputs y1, y2, and y3 of the adaptive equalizer units 71, 72, and 73 are added by the adder 74 and output as the equalized signal y0 of the multi-input adaptive equalizer unit 51.
The output target of the multi-input adaptive equalizer unit 51 is an ideal PR waveform in which the binary detection result is convolved with PR (partial response).

Each adaptive equalizer unit 71, 72, 73 is constituted by, for example, an FIR filter as shown in FIG.
That is, each adaptive equalizer unit 71, 72, 73 is a filter having n + 1 stages of taps including delay elements 80-1 to 80 -n, coefficient multipliers 81-0 to 81 -n, and an adder 84.
In the coefficient multipliers 81-0 to 81-n, tap coefficients C0 to Cn are multiplied for the input x at each time point, respectively.
The outputs of the coefficient multipliers 81-0 to 81-n are added by an adder 84 to become an output y.

In order to perform an adaptive equalization process, the tap coefficients C0 to Cn are controlled. For this purpose, there are provided computing units 82-0 to 82-n that perform an operation by inputting an equalization error ek and each tap input. Further, integrators 83-0 to 83-n for integrating the outputs of the respective computing units 82-0 to 82-n are provided.
In each of the calculators 82-0 to 82-n, for example, calculation of −1 × ek × x is performed. The outputs of the arithmetic units 82-0 to 82-n are integrated by integrators 83-0 to 83-n, and the tap coefficients C0 to Cn of the coefficient multipliers 81-0 to 81-n are changed and controlled according to the integration result. The The integration of the integrators 83-0 to 83-n is performed to adjust the response of the adaptive coefficient control.

  In the data detection processing unit 5 having the above configuration, the binarized data is decoded after crosstalk cancellation is performed.

The adaptive equalizer units 71, 72, 73 have the same configuration of FIG. 4 and are supplied with the same equalization error ek to perform adaptive equalization.
First, the adaptive equalizer unit 72 to which the reproduction information signal Stk0 of the track to be processed is inputted optimizes the error and phase distortion of the input signal frequency component of the reproduction information signal Stk0, that is, performs adaptive PR equalization. This is the same as a normal adaptive equalizer. That is, when the tap coefficients C0 to Cn are adjusted according to the calculation result of −1 × ek × x in each of the calculators 82-0 to 82-n, the tap coefficient C0 in a direction to eliminate the equalization error. ˜Cn is adjusted.

On the other hand, in the other two adaptive equalizer units 71 and 73, the output target is essentially uncorrelated with the reproduction information signals Stk + and Stk− of the adjacent tracks input to the adaptive equalizer units 71 and 73 . For this reason, the adaptive equalizer units 71 and 73 perform an operation to cancel the correlation component, that is, the crosstalk component.
That is, in the case of the adaptive equalizer units 71 and 73, the tap coefficients C0 to Cn are adjusted according to the calculation result of −1 × ek × x in each of the calculators 82-0 to 82-n. The tap coefficients C0 to Cn are adjusted so that the frequency characteristic in the direction in which the crosstalk component is eliminated in the addition result of the unit 74 is obtained.

  As described above, in the adaptive equalizer unit 72, the tap coefficients C0 to Cn are adaptively controlled using the equalization error ek in the direction of the target frequency characteristic, while in the adaptive equalizer units 71 and 73, the equalization error is also the same. The tap coefficients C0 to Cn are automatically controlled using ek so as to have a frequency characteristic for crosstalk cancellation. Thus, the equalized signal y0 of the multi-input adaptive equalizer unit 51 obtained by adding the outputs y1, y2, and y3 of the adaptive equalizer units 71, 72, and 73 by the adder 74 is a signal that has been crosstalk canceled. .

  Also, the adaptive equalizer units 71, 72, 73 as shown in FIG. 4 have a function of adjusting not only the amplitude component on the frequency axis but also the phase component, so that a reproduction information signal which is only roughly synchronized in the first place. The synchronization of Stk0, Stk +, Stk− is also optimally corrected within the multi-input adaptive equalizer unit 51. Therefore, it is not necessary to perform the phase adjustment with the accuracy of one channel clock, which is originally necessary for the reproduction information signals Stk0, Stk +, Stk−. Therefore, as described above, the reproduction information signals Stk0, Stk +, and Stk− may be read from the memory 55 with rough accuracy.

  According to the present embodiment, it is possible to remove the crosstalk component of the adjacent track from the reproduction information signal Stk0 with very high accuracy. For this reason, it is possible to realize a significant improvement in reproducing performance at the time of high density recording or narrow track pitch recording, in which deterioration due to crosstalk from adjacent tracks becomes serious.

FIG. 6A shows the experimental results in each radial tilt state (−0.6 °, 0 °, + 0.6 °) recorded at a high density of 33.4 GB per Blu-ray disc. This shows the effect of the form.
The comparative example here is a case where the crosstalk cancellation is not performed. In other words, the output of the A / D converter 56 in FIG. 2 is PR equalized as it is by an adaptive equalizer and Viterbi decoded by the binarization detector 52.
In the case of this comparative example, the bit error rates are 2.63 × 10 ⁻⁴ , 4.51 × 10 ⁻⁶ , and 9.54 in each state where the radial tilt is −0.6 °, 0 °, and + 0.6 °. × 10 ^-4
On the other hand, in the case of the present embodiment, the bit error rate is 6.25 × 10 ⁻⁶ , 3.13 × 10 ⁻⁶ , in each state where the radial tilt is −0.6 °, 0 °, and + 0.6 °. 3.13 × 10 ⁻⁶ .

FIG. 6B is a graph showing this numerical value, where the broken line is the comparative example and the solid line is the embodiment.
When playing a disc, crosstalk from adjacent tracks increases significantly in the presence of radial tilt, which causes degradation in playback performance. The result of playback signal processing in the comparative example shows an error rate (ECC) with an error rate of the latter stage. Even if is used, it has greatly increased to a point near the practical limit.
On the other hand, in the case of the present embodiment, it can be seen that there is almost no increase in the error rate even under the condition of radial tilt, and the reproduction performance when the crosstalk is increased is greatly increased.
The ratio (%) in FIG. 6A shows the error reduction effect of the embodiment with respect to the comparative example, and is a value obtained by dividing the error rate of the comparative example from the error rate in the embodiment. is there. The effect of improving the error rate under radial tilt in the embodiment is shown.

  In this experiment, a radial tilt was applied, but the same effect can be expected when the track pitch is narrowed. Since narrowing the track pitch directly leads to an increase in the disk capacity per recording layer, this embodiment shows that a large increase in the capacity of the recording disk can be expected.

Further, the present embodiment has the effect of optimizing the phase distortion of the crosstalk component and the amplitude component on the frequency axis. 7A and 7B show the tap coefficients after convergence of the adaptive equalizer units 71 and 73 to which the reproduction information signals Stk + and Stk− of the adjacent tracks of the multi-input adaptive equalizer unit 51 in the above-described experiment are input and their coefficient values. The frequency characteristics (amplitude) obtained from the above are shown.
In FIG. 7A, the horizontal axis represents tap stage 0 to tap stage 255 when the number of tap stages is 256, and the vertical axis represents the tap coefficient of each tap stage.
In FIG. 7B, the horizontal axis represents the normalized frequency fn normalized with the sampling frequency = 1, and the vertical axis represents the gain.
In each of FIGS. 7A and 7B, the dashed line indicates the tap coefficient of the adaptive equalizer unit 71, and the solid line indicates the tap coefficient of the adaptive equalizer unit 73.

Since radial tilt causes asymmetrical aberrations in adjacent tracks, each crosstalk component exhibits phase distortion and frequency characteristics that are difficult to predict.
To confirm this, a coefficient having a large component appears at a position that is asymmetrical and slightly shifted so as to correct the phase error, and the frequency characteristic is also shown in FIG. 7B. Thus, it is not a flat characteristic but a very complicated aspect.

The complexity of the frequency characteristics seems to reflect the effect of optical filtering due to the appearance of asymmetric side lobe components in the beam intensity due to the coma of the beam spot due to tilt.
In addition, since these change as the tilt angle changes due to disc warp or the like according to the disc rotation, in order to obtain the optimum crosstalk cancellation effect, the input signal adaptation function as in this embodiment is used. It would be difficult to achieve without using a correction mechanism.
In other words, in the present embodiment, by appropriately setting each parameter of each adaptive equalizer unit 71, 72, 73, it is possible to follow a dynamic crosstalk component, which cannot be achieved by the prior art. A stable and high-performance crosstalk removing function can be realized.

  As described above, in the present embodiment, the reproduction information signal of another adjacent track is added as an equalizer input signal to the adaptive equalizer of the reproduction information signal to be processed. And using the automatic optimization function of frequency characteristics (amplitude / phase) of adaptive equalizer, various optical aberrations such as disc tilt and focus deviation, spherical aberration deviation, track offset during recording and reproduction, and skew conditions during reproduction However, the crosstalk component from the adjacent track can be removed with high accuracy, and the reproduction performance can be improved.

In the present embodiment, the reproduction information signals of a plurality of tracks are once stored in the memory 55, and the reproduction information signals Stk0, Stk + and Stk− of the adjacent plural tracks are half-processed by a simple synchronization method such as a disk rotation synchronization signal SR. Reading is performed in a synchronized state (an error of about several to several tens of channel clocks is allowed). Then, the function of the multi-input adaptive equalizer unit 51 optimizes the phase component shift and the frequency characteristic of the crosstalk component, generates an optimum crosstalk removal signal, and improves the reproduction performance.
As a result, even a device using a simple reproduction pickup that can obtain only one track of reproduction signals at the same time does not require a complicated synchronization circuit, and high-accuracy crosstalk cancellation is realized.

<3. Data Detection Processing Unit of Second Embodiment>

The configuration of the data detection processing unit 5 of the second embodiment is shown in FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
The configuration of FIG. 8 is provided with a phase detector 59 in addition to the configuration of FIG.

The phase detection unit 59 calculates the reproduction information signals Stk + and Stk− of the adjacent tracks and the reproduction information signal Stk0 of the target track from the convergence values of Tap coefficients of the adaptive equalizer units 71, 72, and 73 of the multi-input adaptive equalizer unit 51. Find the phase difference (time difference). Then, a correction signal HD that reduces the phase difference is supplied to the memory controller 58.
The memory controller 58 adjusts the reading operation from the memory 55 according to the correction signal HD. Specifically, for example, the read address ad is increased or decreased. Thereby, the phase difference is reduced in the reproduction information signals Stk0, Stk +, Stk− from the memory 55.
At the same time, the phase detector 59 shifts the tap coefficients of the adaptive equalizer units 71 and 73 for the adjacent tracks and the integrated values of the integrators 83-0 to 83-n according to the phase correction operation.

In this way, the number of taps of each adaptive equalizer unit 71, 72, 73 can be reduced. Thereby, effects such as simplification of the equalizer configuration and reduction of the mounting area can be obtained. This is because even when the phase is dynamically changed, the phase adjustment of the reproduction information signals Stk0, Stk +, Stk- is performed so that the calculation of crosstalk cancellation can be performed within a smaller range of equalizer taps. This is because it becomes possible.
Or, when considered under the condition of a fixed number of taps, the crosstalk cancellation performance can be more stably brought out.

<4. Data Detection Processing Unit of Third Embodiment>

FIG. 9 shows the configuration of the data detection processing unit 5 according to the third embodiment. The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
The configuration of FIG. 9 is obtained by removing the memory 55 and the memory controller 58 from the configuration of FIG.

  In this case, for example, the optical pickup 1 performs three-spot laser irradiation, and when scanning the track to be processed with the main spot, also scans the tracks on both sides of the target track with the side spots on both sides. Then, by detecting each reflected light by each of the three laser spot irradiations by three photodetectors, it is possible to simultaneously obtain reproduction information signals of the target track and adjacent tracks on both sides thereof via the matrix circuit 4. .

In such a configuration, each reproduction information signal may be converted into digital data by the A / D converter 56 and supplied to the multi-input adaptive equalizer unit 51 as reproduction information signals Stk0, Stk +, Stk−.
The crosstalk cancellation operation is the same as that in the first embodiment.
When the optical pickup 1 and the matrix circuit 4 are configured to be able to read out the reproduction information signals for three tracks independently, the data detection processing unit 5 is configured as shown in FIG. The value processing can be performed, and the configuration as the data detection processing unit 5 can be simplified.

<5. Modification>

Although the embodiments have been described above, various modifications can be considered as the present invention.
For example, in the embodiment, the reproduction information signals of two tracks adjacent to the inner and outer peripheral sides of the target track are input to the multi-input adaptive equalizer unit 51 as the reproduction information signal of the adjacent track. The reproduction information signal may be input to the multi-input adaptive equalizer unit 51.
That is, two tracks that are close to the outer peripheral side and two tracks that are close to the inner peripheral side with respect to the target track are set as close tracks, respectively. The multi-input adaptive equalizer unit 51 includes five adaptive equalizer units so that the reproduction information signals of the target track and the reproduction information signals of the four adjacent tracks are input to the respective adaptive equalizer units.
For example, when the track pitch is narrowed, the reproduction information signal of the adjacent track and the next track may become a crosstalk component for the target track. In such a system, it is appropriate to perform a crosstalk cancel operation corresponding to four adjacent tracks.

On the contrary, the adjacent track may be only one track adjacent to one of the outer peripheral side and the inner peripheral side with respect to the target track. In that case, the multi-input adaptive equalizer unit 51 may be provided with two adaptive equalizer units.
In the same way, it can be considered that the adjacent tracks are three tracks, six tracks or more. In any case, according to the characteristics and operation of the playback device and recording medium, the playback information signal of the track that becomes the crosstalk component is input to the multi-input adaptive equalizer unit 51 together with the playback information signal of the target track. That's fine.

  Further, although the embodiments have been described by taking a disk drive device for an optical disk as an example, the present invention can also be applied to a reproducing device and a data detection device for an optical recording medium other than a disk, a disk type or other types of magnetic recording media. That is, the present invention is effective when tracks are formed side by side on a recording medium and crosstalk occurs from adjacent tracks.

  1 optical pickup, 4 matrix circuit, 5 data detection processing unit, 51 multi-input adaptive equalizer unit, 52 binarization detector, 53 PR convolution unit, 54 equalization error calculator, 55 memory, 56 A / D converter 57 PLL circuit, 58 memory controller, 59 phase difference detection unit, 71, 72, 73 adaptive equalizer unit, 74 adder, 80-1 to 80-n delay element, 81-0 to 81-n coefficient multiplier, 82 -0 to 82-n computing unit, 83-0 to 83-n integrator, 84 adder

Claims (7)

As reproduction information signals read from the recording medium, N pieces of reproduction information signals from the target track that are data detection targets and N pieces on the inner circumference side of the target track that are crosstalk components with respect to the reproduction information signal from the target track Each of the reproduction information signal from the track of the target track and the reproduction information signal from the M tracks on the outer periphery side of the target track, which is a crosstalk component with respect to the reproduction information signal from the target track, and The reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the reproduction information signal from the M tracks on the outer circumference side are synchronized with coarser accuracy than the channel clock accuracy. A memory unit that is read in a state of coarse synchronization that is a state;
A first adaptive equalizer unit to which a reproduction information signal from the target track is input as a reproduction information signal read at each time point from the memory unit, and the N tracks on the inner peripheral side that are roughly synchronized with the target track N second adaptive equalizer units to which the respective reproduction information signals are input and M pieces of reproduction information signals to which the respective reproduction information signals from the M tracks on the outer peripheral side roughly synchronized with the target track are input. A multi-input adaptive equalizer unit that calculates the outputs of the first, second, and third adaptive equalizer units and outputs them as equalized signals;
A binarization unit that performs binarization processing on the equalized signal of the multi-input adaptive equalizer unit to obtain binary data;
An equalization error is obtained from the equalization target signal obtained based on the binary detection result of the binarization unit and the equalization signal output from the multi-input adaptive equalizer unit, and the equalization error is calculated as An equalization error calculator that supplies the adaptive equalizer unit as a tap coefficient control signal for adaptive equalization;
With
In the first adaptive equalizer unit, adaptive equalization corresponding to the binarization processing is performed by the tap coefficient calculation using the equalization error,
In each of the second and third adaptive equalizer units, the reproduction information signal from the N tracks on the inner circumference side and the M tracks on the outer circumference side are calculated by the tap coefficient calculation using the equalization error. A data detection apparatus in which adaptive equalization is performed to correct each phase error between a reproduction information signal and the reproduction information signal from the target track. From the memory unit, based on the rotation synchronization signal of the recording medium, the reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the M pieces of information on the outer circumference side By reading out the reproduction information signal from the track, the reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the reproduction from the M tracks on the outer circumference side are read. The data detection device according to claim 1, wherein the information signal is input to the multi-input adaptive equalizer unit in a state of coarse synchronization.   The phase difference of each reproduction information signal read from the memory unit and input to the plurality of adaptive equalizer units is detected, and based on the detected phase difference, the read timing of each reproduction information signal from the memory unit is detected. The data detection apparatus according to claim 1, further comprising a phase difference detection unit that outputs a correction signal for correction. The multi-input adaptive equalizer unit includes the first adaptive equalizer unit, one second adaptive equalizer unit, and one third adaptive equalizer unit,
A reproduction information signal from the inner track of the target track is input to the second adaptive equalizer unit, and a reproduction information signal from the outer track of the target track is input to the third adaptive equalizer unit. The data detection device according to claim 1, wherein the data detection device is input. The multi-input adaptive equalizer unit performs a partial response equalization process on the reproduction information signal from the target track,
The binarization unit performs a maximum likelihood decoding process as a binarization process for the equalized signal of the multi-input adaptive equalizer unit,
The equalization error calculation unit performs an operation using an equalization target signal obtained by convolution processing of the binary detection result by the maximum likelihood decoding and an equalization signal output from the multi-input adaptive equalizer unit, etc. The data detection device according to claim 1, wherein a data error is obtained. A head unit for reading information from a recording medium;
As a reproduction information signal read from the recording medium, a reproduction information signal from a target track as a data detection target, a reproduction information signal from N tracks on the inner circumference side of the target track, and an outer circumference side of the target track Each of the reproduction information signals from the M tracks is stored, the reproduction information signal from the target track, the reproduction information signals from the N tracks on the inner circumference side, and the M pieces of reproduction information signals on the outer circumference side. A memory unit that reads a reproduction information signal from a track in a coarse synchronization state, which is a synchronization state with a coarser accuracy than the channel clock accuracy ;
A first adaptive equalizer unit to which a reproduction information signal from the target track is input as a reproduction information signal read at each time point from the memory unit, and the N tracks on the inner peripheral side that are roughly synchronized with the target track The second N adaptive equalizer units to which the respective reproduction information signals are input, and the third reproduction information signals from the M outer tracks that are roughly synchronized with the target track are input. A multi-input adaptive equalizer unit that calculates the output of each of the first, second, and third adaptive equalizer units and outputs an equalized signal;
A binarization unit that performs binarization processing on the equalized signal of the multi-input adaptive equalizer unit to obtain binary data;
An equalization error is obtained from the equalization target signal obtained based on the binary detection result of the binarization unit and the equalization signal output from the multi-input adaptive equalizer unit, and the equalization error is calculated as An equalization error calculator that supplies the adaptive equalizer unit as a tap coefficient control signal for adaptive equalization;
A demodulator that demodulates reproduction data from the binary data obtained by the binarization unit;
With
In the first adaptive equalizer unit, adaptive equalization corresponding to the binarization processing is performed by the tap coefficient calculation using the equalization error,
In each of the second and third adaptive equalizer units, the reproduction information signal from the N tracks on the inner circumference side and the M tracks on the outer circumference side are calculated by the tap coefficient calculation using the equalization error. A reproduction apparatus comprising: adaptive reproduction for correcting each phase error between the reproduction information signal and the reproduction information signal from the target track. As reproduction information signals read from the recording medium, N pieces of reproduction information signals from the target track that are data detection targets and N pieces on the inner circumference side of the target track that are crosstalk components with respect to the reproduction information signal from the target track Each of a reproduction information signal from the track and a reproduction information signal from M tracks on the outer periphery side of the target track, which is a crosstalk component with respect to the reproduction information signal from the target track, are stored in the memory unit. ,
From the memory unit, the reproduction information signal from the target track, the reproduction information signal from the N tracks on the inner circumference side, and the reproduction information signal from the M tracks on the outer circumference side are channel clock accuracy Read in the coarse synchronization state, which is the coarser synchronization state
A reproduction information signal from the target track is input to the first adaptive equalizer unit as a reproduction information signal read at each time point from the memory unit, and from the N tracks on the inner circumference side that is roughly synchronized with the target track. Are input to N second adaptive equalizer units, and the respective reproduction information signals from the M tracks on the outer peripheral side which are roughly synchronized with the target track are input to M third adaptive information units. Input to the equalizer unit, calculate the output of each of the first, second and third adaptive equalizer units and output as an equalized signal,
Binary processing is performed on the equalized signal to obtain binary data,
Tap coefficient control for adaptive equalization of each adaptive equalizer unit is performed using an equalization error between the equalization target signal obtained based on the binary detection result in the binarization processing and the equalization signal. As well as
In the first adaptive equalizer unit, adaptive equalization corresponding to the binarization processing is performed by calculating a tap coefficient using the equalization error,
In each of the second and third adaptive equalizer units, the reproduction information signal from the N tracks on the inner circumference side and the M tracks on the outer circumference side are calculated by the tap coefficient calculation using the equalization error. A data detection method for performing adaptive equalization for correcting each phase error between a reproduction information signal and the reproduction information signal from the target track.

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