Optical disk drive

Abstract

The optical disk device of the present disclosure is characterized in that a signal obtained by extracting an adjacent track component from a playback signal of a target track is generated and phase error is detected from mutual correlation with a playback signal of the adjacent track, whereby resampling is performed so that the playback signal of the target track and the playback signal of the adjacent track take on adjacent signal waveforms at the same angular position.

Description

Technical Field

[0001] The present disclosure relates to an optical disc apparatus that records and reproduces data on an optical disc.

Background Art

[0002] Currently, many types of optical discs such as DVDs or Blu-ray (registered trademark) discs (hereinafter referred to as BDs) are used as information recording media for storing videos, data, etc. From the viewpoint of space efficiency during data storage, as technologies for improving the recording capacity per unit volume without increasing the cost of optical discs, there are a technology for improving the linear density and a technology for improving the track density.

[0003] As a technology for improving the linear density, a Partial Response Most Likelihood (hereinafter referred to as PRML) signal processing technology is widely used. On the track of an optical disc, a binary signal represented by marks and spaces is recorded. When reproducing this binary signal, due to the frequency characteristics of detection with an optical beam, the detected reproduction signal is band-limited to low frequencies. This is caused by multiple marks and spaces being read out simultaneously according to the size of the diffraction limit of the optical beam, and is called inter-symbol interference. The PRML signal processing technology is composed of an adaptive equalization circuit that equalizes the reproduction signal waveform so as to approach an expected waveform assuming inter-symbol interference, and a maximum likelihood decoding circuit that estimates the recorded binary signal by comparing and selecting between the equalized reproduction signal waveform and the expected waveform. As the linear density is improved, a PRML signal processing technology with an extended inter-symbol interference width has been used.

[0004] As a technology for improving the track density, there is a land (between grooves)-groove recording and reproduction technology. This technology has already been used in DVD-RAM, and improves the track density by recording data that was previously recorded only on grooves or lands on both grooves and lands. Furthermore, a crosstalk cancellation technology for reducing crosstalk components from adjacent tracks has been disclosed.

[0005] As a crosstalk cancellation technique, a reproduction signal waveform from a target track to be reproduced and reproduction signal waveforms from adjacent tracks on both sides are simultaneously input to an adaptive equalization circuit of a PRML signal processing technique, thereby obtaining an equalized reproduction signal waveform in which a crosstalk component from an adjacent track that becomes noise is canceled. This is a multi-track crosstalk cancellation technique (Patent Document 3).

[0006] Also, there is a single-track crosstalk cancellation technique in which a light beam of reflected light from a target track to be reproduced is divided into a plurality of regions for detection, and these detected reproduction signal waveforms are simultaneously input to an adaptive equalization circuit of a PRML signal processing technique, thereby obtaining an equalized reproduction signal waveform in which a crosstalk component is canceled (Patent Document 4).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0008] The present disclosure provides an optical disk apparatus that enables stable reproduction of data recorded on an optical disk with a high track density.

[0009] The optical disc drive in the present disclosure is an optical disc drive that has a groove-shaped track and records and reproduces recorded data on an optical disc capable of recording the recorded data on the land portions and groove portions of the groove, irradiates a track on the optical disc with a laser having a wavelength λ through an objective lens with an aperture number N, and divides the reflected light reflected and diffracted by the optical disc into light fluxes in at least four or more regions of an outer end portion, an outer central portion, an inner central portion, and an inner end portion in the radial direction of the optical disc, receives each of the divided light fluxes individually, and outputs an outer end portion light amount signal, an outer central portion light amount signal, an inner central portion light amount signal, and an inner end portion light amount signal corresponding to the light amount; a reproduction signal detection circuit that outputs the outer end portion light amount signal, the outer central portion light amount signal, the inner central portion light amount signal, and the inner end portion light amount signal as an outer end portion reproduction signal, an outer central portion reproduction signal, an inner central portion reproduction signal, and an inner end portion reproduction signal sampled respectively; a memory circuit that stores each first reproduction signal detected from a target track that is a target for reproducing recorded data, each second reproduction signal detected from an inner adjacent track of the target track, and each third reproduction signal detected from an outer adjacent track of the target track by the optical pickup and the reproduction signal detection circuit; a resampling circuit that reads out each first reproduction signal, each second reproduction signal, and each third reproduction signal from the memory circuit and corrects the sampling timing of each second reproduction signal and each third reproduction signal based on each first reproduction signal; and a decoding circuit that decodes the recorded data recorded on the target track from each first reproduction signal, each second resampled reproduction signal resampled by the resampling circuit, and each third resampled reproduction signal.When the target track is a groove portion, the resampling circuit obtains correction conditions using a first cross-correlation value between a difference signal between the first inner central reproduction signal and the first outer end reproduction signal and a sum signal of each of the second reproduction signals, and resamples each of the second reproduction signals. The resampling circuit obtains correction conditions using a second cross-correlation value between a difference signal between the first outer central reproduction signal and the first inner end reproduction signal and a sum signal of each of the third reproduction signals, and resamples each of the third reproduction signals. When the target track is a land portion, the resampling circuit obtains correction conditions using a third cross-correlation value between a difference signal between the first outer central reproduction signal and the first inner end reproduction signal and a sum signal of each of the second reproduction signals, and resamples each of the second reproduction signals. The resampling circuit obtains correction conditions using a fourth cross-correlation value between a difference signal between the first inner central reproduction signal and the first outer end reproduction signal and a sum signal of each of the third reproduction signals, and resamples each of the third reproduction signals.

[0010] Also, when the target track is a groove portion, the resampling circuit may obtain correction conditions such that the first cross-correlation value is maximized and resample each of the second reproduction signals, obtain correction conditions such that the second cross-correlation value is maximized and resample each of the third reproduction signals. When the target track is a land portion, the resampling circuit may obtain correction conditions such that the third cross-correlation value is maximized and resample each of the second reproduction signals, obtain correction conditions such that the fourth cross-correlation value is maximized and resample each of the third reproduction signals.

[0011] Further, the resampling circuit includes an inner phase correction filter that corrects the phase of each of the second reproduction signals, and calculates a first inner cross-correlation value from the waveform of the first difference signal obtained from two predetermined ones of the first reproduction signals from time Ts to time Te and the waveform of the sum signal of the inner phase-corrected reproduction signals output from the inner phase correction filter from time Ts to time Te, calculates a second inner cross-correlation value from the waveform of the sum signal of the inner phase-corrected reproduction signals from time Ts-1 to time Te-1, and calculates a third inner cross-correlation value from the waveform of the sum signal of the inner phase-corrected reproduction signals from time Ts+1 to time Te+1. An inner cross-correlation circuit, an inner phase error detection circuit that calculates a phase error between the first difference signal and the sum signal of the inner phase-corrected reproduction signals from the first inner cross-correlation value, the second inner cross-correlation value, and the third inner cross-correlation value, and an inner phase control circuit that controls the phase correction value of the inner phase correction filter based on the phase error detected by the inner phase error detection circuit, an outer phase correction filter that corrects the phase of each of the third reproduction signals, and calculates a first outer cross-correlation value from the waveform of the second difference signal obtained from two predetermined ones of the first reproduction signals from time Ts to time Te and the waveform of the sum signal of the outer phase-corrected reproduction signals output from the outer phase correction filter from time Ts to time Te, calculates a second outer cross-correlation value from the waveform of the sum signal of the outer phase-corrected reproduction signals from time Ts-1 to time Te-1, and calculates a third outer cross-correlation value from the waveform of the sum signal of the outer phase-corrected reproduction signals from time Ts+1 to time Te+1. An outer cross-correlation circuit, an outer phase error detection circuit that calculates a phase error between the second difference signal and the sum signal of the outer phase-corrected reproduction signals from the first outer cross-correlation value, the second outer cross-correlation value, and the third outer cross-correlation value, and an outer phase control circuit that controls the phase correction value of the outer phase correction filter based on the phase error detected by the outer phase error detection circuit.

[0012] The optical disc device in the present disclosure enables stable reproduction of data recorded on an optical disc with a high track density.

Brief Description of Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, a more detailed description than necessary may be omitted. For example, a detailed description of well-known matters and a redundant description of substantially the same configuration may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art.

[0015] Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and it is not intended to limit the subject matter described in the claims thereby.

[0016] (Embodiment 1) [1. Configuration] FIG. 1 is a configuration diagram of an optical disc drive 10 in the present Embodiment 1. As shown in FIG. 1, the optical disc drive 10 includes an optical head 101, a spindle motor 102, a servo controller 103, a laser drive circuit 104, a modulation circuit 105, an error correction coding circuit 106, a reproduction signal detection circuit 107, a resampling circuit 108, a PRML circuit 109, a demodulation circuit 110, an error correction decoding circuit 111, an I / F circuit 112, a memory circuit 113, a system controller 114, and a ROM (Read Only Memory) 115.

[0017] The optical disk drive 10 records and plays back user data on the optical disk 100. On the optical disk 100, tracks are formed in a spiral shape from the inner circumference to the outer circumference. The tracks consist of groove tracks formed by grooves and land tracks formed between adjacent groove tracks. User data can be recorded on either the groove tracks or the land tracks.

[0018] The spindle motor 102 rotates the optical disk 100. The optical head 101 irradiates the optical disk 100 with a light beam to record user data on the optical disk 100 and play back user data from the optical disk 100.

[0019] The servo controller 103 controls the optical head 101 and the spindle motor 102, and performs control to condense and scan the light beam irradiated from the optical head 101 onto the tracks provided on the optical disk 100, and movement control to access the target track. The servo controller 103 controls the position of the optical head 101 and the rotation speed of the spindle motor 102 so that the optical head 101 scans the optical disk 100 at a predetermined linear velocity.

[0020] The I / F circuit 112 receives user data to be recorded on the optical disk 100 from the host 116 and stores it in the memory circuit 113. Also, the I / F circuit 112 sends the user data reproduced from the optical disk 100 and stored in the memory circuit 113 to the host 116. The I / F circuit 112 also sends out the user data stored in the memory circuit 113 to other internal blocks, and conversely, stores the user data received from other internal blocks in the memory circuit 113.

[0021] The error correction coding circuit 106 adds a parity code for error correction to the user data received from the I / F circuit 112 to generate encoded data.

[0022] The modulation circuit 105 receives the encoded data from the error correction encoding circuit 106 and generates a modulated signal modulated according to a predetermined modulation code. This modulated signal is recorded on the track on the optical disc 100.

[0023] The laser drive circuit 104 converts the modulated signal into an optical pulse to accurately form a mark on the optical disc 100 and drives the blue semiconductor laser 207 (described later) of the optical head 101. Due to the heat of the irradiated optical beam, a mark is formed on the optical disc 100.

[0024] On the other hand, the user data recorded on the optical disc 100 is reproduced by the reproduction signal detection circuit 107, resampling circuit 108, PRML circuit 109, demodulation circuit 110, and error correction decoding circuit 111.

[0025] The optical head 101 irradiates the optical disc 100 with an optical beam and detects the reflected light from the optical disc 100. The optical head 101 outputs a light amount signal based on the detected reflected light.

[0026] The reproduction signal detection circuit 107 outputs a reproduction signal obtained by sampling the light amount signal by an A / D converter and stores the reproduction signal data in the memory circuit 113 through the I / F circuit 112.

[0027] The resampling circuit 108 reads the reproduction signal data stored in the memory circuit 113 regarding the track on the optical disc 100 where the user data is to be reproduced, and the inner adjacent track and the outer adjacent track thereof, and performs resampling processing so that the reproduction signals at the same angular position on each track are obtained.

[0028] The PRML circuit 109 decodes each resampled reproduction signal to generate a decoded signal. Specifically, by simultaneously inputting each resampled reproduction signal into the adaptive equalization circuit, the PRML signal processing is performed to select the expected value waveform closest to the equalized reproduction signal obtained with the crosstalk component canceled, from the comparison between the equalized reproduction signal and the expected value waveform, and output the pattern signal that is the source of the expected value waveform as the decoded signal. The characteristics of the expected value waveform are assumed to take into account the influence of the band limitation due to the frequency characteristics of detection with the optical beam.

[0029] The demodulation circuit 110 demodulates the encoded data from the decoded signal according to a predetermined modulation code.

[0030] The error correction decoding circuit 111 corrects the errors in the demodulated encoded data and restores the user data.

[0031] The ROM 115 is composed of a flash memory. The ROM 115 stores a program for the system controller 114 to control the entire optical disk device 10.

[0032] The system controller 114 reads and executes the program stored in the ROM 115 to control each circuit and the communication with the host 116. In FIG. 1, for convenience, the arrows indicating the control from the system controller 114 to each component are omitted. The system controller 114 of the optical disk device 10 in the present embodiment controls the operations of each circuit related to the recording and reproduction of user data.

[0033] Using FIG. 2, the detailed configuration of the optical head 101 corresponding to the crosstalk cancellation technology will be described.

[0034] FIG. 2 is a diagram showing the configuration of the optical head 101. The optical head 101 includes an objective lens 201, a collimator lens 202, a laser mirror 203, a beam splitter 204, an objective lens controller 205, a collimator lens controller 206, a blue semiconductor laser 207, a control photodetector 208, a splitting element 209, and a reproduction photodetector 211.

[0035] The blue semiconductor laser 207 emits an optical beam having a wavelength of 405 nm. The optical beam is reflected by the laser mirror 203 and enters the collimator lens 202. The optical beam is converted into parallel light through the collimator lens 202 and is focused by the objective lens 201 and irradiated onto the track of the optical disk 100.

[0036] The reflected light reflected and diffracted on the track of the optical disk 100 passes through the objective lens 201, the collimator lens 202, and the laser mirror 203. The beam splitter 204 splits the reflected light transmitted through the laser mirror 203 into two directions. That is, the beam splitter 204 reflects a part of the reflected light and transmits the rest. The control photodetector 208 receives the light reflected by the beam splitter 204. The splitting element 209 splits the light transmitted through the beam splitter 204 into a plurality of directions. The reproduction photodetector 211 receives each of the lights split by the splitting element 209.

[0037] Servo controller 103 generates a focus error signal and a tracking error signal based on the electrical signal output by control photodetector 208. The focus error signal and the tracking error signal are an example of signals indicating the amount of deviation of the irradiation position of the optical beam with respect to the track. Servo controller 103 uses the focus error signal and the tracking error signal to generate a focus control signal and a tracking control signal so that each error becomes small. Objective lens controller 205 performs a focusing operation and a tracking operation by driving objective lens 201 based on these control signals. In addition, collimator lens controller 206 suppresses spherical aberration in the condensing state with respect to the track of optical disc 100 by driving collimator lens 202 based on these control signals and adjusting the position.

[0038] The splitting element 209 acts as a diffraction grating by having fine grooves formed on its surface. The splitting element 209 has a splitting pattern 210 that divides the area where the reflected light from the optical disc 100 enters into six areas Ch0 to Ch5. The reflected light that has passed through each area is split in different directions by the diffraction grating. The reproducing photodetector 211 has six light-receiving areas that receive each of the six reflected lights split by passing through each area of the splitting element 209. The reproducing photodetector 211 generates six light quantity signals according to the amount of light received by each light-receiving area. In the splitting pattern 210, both ends in the recording line direction (recording track direction) are respectively split as area Ch4 and area Ch5. Also, in the radial direction, which is perpendicular to the recording line direction, the central part of the splitting pattern 210 is split as area Ch0 and area Ch1, and both ends are respectively split as area Ch2 and area Ch3. Area Ch0 and area Ch1 are respectively arranged on both sides of the center of the splitting element 209 in the radial direction. In other words, area Ch0 and area Ch1 are one area and the other area that split the central part of the splitting element 209 to the left and right with respect to the recording line direction. Area Ch2 is arranged adjacent to area Ch0 on the outside of area Ch0 in the radial direction. Area Ch3 is arranged adjacent to area Ch1 on the outside of area Ch1 in the radial direction. In the following description, the light quantity signal output when the light-receiving area of the reproducing photodetector 211 receives the light that has passed through area Ch0 is referred to as the light quantity signal of area Ch0. The same applies to the light quantity signals of other areas.

[0039] The reproduction signal detection circuit 107 outputs a reproduction signal sampled by an A / D converter with respect to these six light quantity signals generated by the reproducing photodetector 211, and stores the reproduction signal data in the memory circuit 113 through the I / F circuit 112. After that, it has a configuration corresponding to crosstalk cancellation technology by the resampling circuit 108 and the PRML circuit 109.

[0040] The detailed configuration of the resampling circuit 108 will be described with reference to FIG. 4.

[0041] The resampling circuit 108 reads out the track on the optical disc 100 for which user data is to be reproduced, and the reproduction signal data stored in the memory circuit 113 regarding the inner adjacent track and the outer adjacent track thereof, and performs resampling processing so as to obtain reproduction signals at the same angular position on each track. The resampling circuit 108 includes a target track difference signal generation circuit 401, an inner phase correction filter 402, an inner cross-correlation circuit 403, an inner phase error detection circuit 404, and an inner phase control circuit 405. By these components, the inner track reproduction signal read from the memory circuit 113 is resampled to obtain an inner track resampled reproduction signal that becomes a reproduction signal at the same angular position on the track as the target track reproduction signal also read from the memory circuit 113, and is output. Also, the resampling circuit 108 includes an outer phase correction filter 406, an outer cross-correlation circuit 407, an outer phase error detection circuit 408, and an outer phase control circuit 409. By these components, the outer track reproduction signal read from the memory circuit 113 is resampled to obtain an outer track resampled reproduction signal that becomes a reproduction signal at the same angular position on the track as the target track reproduction signal also read from the memory circuit 113, and is output.

[0042] When the target track is a groove, the target track difference signal generation circuit 401 outputs the difference signal between the Ch0 reproduction signal and the Ch3 reproduction signal of the target track reproduction signal read from the memory circuit 113 to the inner cross-correlation circuit 403, and outputs the difference signal between the Ch1 reproduction signal and the Ch2 reproduction signal to the outer cross-correlation circuit 407. When the target track is a land, the target track difference signal generation circuit 401 outputs the difference signal between the Ch1 reproduction signal and the Ch2 reproduction signal to the inner cross-correlation circuit 403, and outputs the difference signal between the Ch0 reproduction signal and the Ch3 reproduction signal to the outer cross-correlation circuit 407.

[0043] The inner phase correction filter 402 is composed of an FIR filter whose filter coefficients are controlled so that the sampling timing of the input signal waveform is corrected according to the phase control value output by the inner phase control circuit 405. It outputs an inner track resampled reproduction signal obtained by correcting the phases of the reproduction signals from Ch0 to Ch5 of the inner track reproduction signal, and outputs an inner track sum signal obtained by adding these signals at a predetermined ratio to the inner cross-correlation circuit 403.

[0044] The inner cross-correlation circuit 403 calculates the cross-correlation between the difference signal output by the target track difference signal generation circuit 401 and the inner track sum signal output by the inner phase correction filter 402. Three cross-correlation values are calculated, including those shifted by ±1 time.

[0045] The inner phase error detection circuit 404 calculates the phase error between the difference signal of the target track and the inner track sum signal from the three cross-correlation values output by the inner cross-correlation circuit 403.

[0046] The inner phase control circuit 405 calculates a phase control value by integrating the phase error output by the inner phase error detection circuit 404.

[0047] The outer phase correction filter 406 is composed of an FIR filter whose filter coefficients are controlled so that the sampling timing of the input signal waveform is corrected according to the phase control value output by the outer phase control circuit 409. It outputs an outer track resampled reproduction signal obtained by correcting the phases of the reproduction signals from Ch0 to Ch5 of the outer track reproduction signal, and outputs an outer track sum signal obtained by adding these signals at a predetermined ratio to the outer cross-correlation circuit 407.

[0048] The outer cross-correlation circuit 407 calculates the cross-correlation between the difference signal output by the target track difference signal generation circuit 401 and the outer track sum signal output by the outer phase correction filter 406. Three cross-correlation values are calculated, including those shifted by ±1 time.

[0049] The outer phase error detection circuit 408 calculates the phase error between the difference signal of the target track and the outer track sum signal from the three cross-correlation values output by the outer cross-correlation circuit 407.

[0050] The outer phase control circuit 409 calculates a phase control value by integrating the phase error output by the outer phase error detection circuit 408.

[0051] [2. Operation] Next, the operation of the optical disc apparatus 10 in the present embodiment will be described.

[0052] The I / F circuit 112 acquires the recording data transmitted from the host 116 and the logical address of the recording destination on the optical disc 100. The I / F circuit 112 divides the recording data into data blocks of a predetermined unit and sends each data block to the error correction coding circuit 106.

[0053] The error correction coding circuit 106 adds a parity code for correcting errors during reproduction to the recording data in data block units. The modulation circuit 105 modulates the recording data with the added parity code into a modulation signal according to a predetermined modulation rule. The laser drive circuit 104 converts the modulation signal into a recording pulse waveform in order to accurately form a recording mark on the optical disc 100, and outputs it to the blue semiconductor laser 207 of the optical head 101 as a drive signal for driving the blue semiconductor laser 207. The blue semiconductor laser 207 of the optical head 101 irradiates a laser pulse corresponding to the drive signal at a position on the optical disc 100 corresponding to the logical address of the recording destination. Thereby, a mark corresponding to the modulation signal is recorded on the track of the optical disc 100.

[0054] The system controller 114 controls the above-described recording operation. Based on the logical address of the recording destination acquired by the I / F circuit 112, the system controller 114 determines the position to record on the optical disk 100, and controls the servo controller 103 to move the optical head 101 to the target position. Before the optical head 101 reaches the track where the target position is located, the system controller 114 operates the error correction encoding circuit 106, and when the target position is reached, operates the modulation circuit 105 and the laser drive circuit 104 to perform recording.

[0055] Next, the playback operation of the optical disk apparatus 10 in the present embodiment will be described.

[0056] The I / F circuit 112 acquires the logical address of the playback destination on the optical disk 100 transmitted from the host 116. The system controller 114 controls each circuit in order to play back the user data of the requested logical address. FIG. 3 shows the control of the operation of storing the playback signal data in the memory circuit 113 and the operation of reading it out among the controls of the playback operation.

[0057] In FIG. 3, the logical address for which the user data is to be played back is on the target group section 302. The system controller 114 controls the servo controller 103 to move the optical head 101 to the target group section 302. The optical head 101 irradiates the target group section 302 with a laser, and outputs six light amount signals from Ch0 to Ch5 from the reflected light. The playback signal detection circuit 107 outputs a playback signal obtained by sampling the six light amount signals by an A / D converter. The system controller 114 designates the memory address for storing the playback signal of the target group section 302, and controls the operation of storing the playback signal of the target group section 302 in the memory circuit 113 through the I / F circuit 112.

[0058] Next, the system controller 114 controls the servo controller 103 to move the optical head 101 to the inner land portion 301 located adjacent to the inside of the target groove portion 302. Similarly, an optical amount signal corresponding to the inner land portion 301 is output from the optical head 101, and the reproduction signal detection circuit 107 outputs a reproduction signal obtained by sampling the optical amount signal. The inner land portion 301 and the outer land portion 303 are spirally connected. When the optical disc 100 makes one rotation, the optical head 101 scans the outer land portion 303 as it is. The system controller 114 designates a memory address for storing the reproduction signal of the inner land portion 301, and controls the operation of storing the reproduction signal from the inner land portion 301 to the outer land portion 303 in the memory circuit 113 through the I / F circuit 112.

[0059] By the above operations, the reproduction signals of the inner land portion 301, the target groove portion 302, and the outer land portion 303 are stored in the memory circuit 113. After all the reproduction signals are ready, the system controller 114 designates the memory addresses where the respective reproduction signals are stored so that the respective reproduction signals corresponding to the same angular positions of the inner land portion 301, the target groove portion 302, and the outer land portion 303 can be simultaneously input to the resampling circuit 108, and controls the operation of reading out the respective reproduction signal data from the memory circuit 113.

[0060] Each of the reproduction signal data read from the memory circuit 113 is input to the resampling circuit 108 through the I / F circuit 112. As shown in FIG. 4, the target track reproduction signal is input to the target track difference signal generation circuit 401, the inner track reproduction signal is input to the inner phase correction filter 402, and the outer track reproduction signal is input to the outer phase correction filter 406.

[0061] The inner phase correction filter 402 is composed of an FIR filter whose filter coefficients are controlled so that the sampling timing of the input signal waveform is corrected according to the phase control value output by the inner phase control circuit 405. As the filter coefficients, for example, those following a sinc function can be used. The inner phase correction filter 402 outputs inner track resampled reproduction signals obtained by correcting the phases of the reproduction signals from Ch0 to Ch5 of the inner track reproduction signal, and outputs an inner track sum signal obtained by adding these signals at a predetermined ratio to the inner cross-correlation circuit 403.

[0062] The inner cross-correlation circuit 403 calculates the cross-correlation between the difference signal output by the target track difference signal generation circuit 401 and the inner track sum signal output by the inner phase correction filter 402. FIG. 5 shows the relationship for calculating the cross-correlation. The cross-correlation value Ca is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the inner track sum signal from time Ts-1 to time Te-1. The cross-correlation value Cb is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the inner track sum signal from time Ts to time Te. The cross-correlation value Cc is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the inner track sum signal from time Ts+1 to time Te+1. When the target track is the target groove portion 302, in each reproduction signal detected through the division pattern 210, the crosstalk component due to the recording marks recorded on the inner land portion 301 is largely included in the difference signal between Ch0 and Ch3 of the target track reproduction signal. Therefore, adjacent positions at the same angle can be detected based on the cross-correlation value between the difference signal of the target track and the inner land portion. When the target track is a land, the crosstalk component due to the recording marks recorded on the inner groove portion is largely included in the difference signal between Ch1 and Ch2 of the target track reproduction signal, and similarly, adjacent positions at the same angle can be detected based on the cross-correlation value.

[0063] The inner phase error detection circuit 404 obtains the phase error between the inner track sum signal and the difference signal of the target track. The timing at which the cross-correlation value becomes maximum can be calculated by the least squares method of a quadratic function from the three cross-correlation values Ca, Cb, and Cc with shifted times. As described below, the calculated timing becomes the phase error between the current phase control value by the inner phase control circuit 405 and the target track reproduction signal. Phase error = {-3(Ca + Cb) - (Ca + Cb + Cc)} / {2(Ca - Cc)} The inner phase control circuit 405 calculates the phase control value in the inner phase correction filter 402 by integrating the phase error output from the inner phase error detection circuit 404.

[0064] The same applies to the reproduction signal of the outer land portion 303.

[0065] The outer phase correction filter 406 is composed of an FIR filter whose filter coefficient is controlled so that the sampling timing of the input signal waveform is corrected according to the phase control value output from the outer phase control circuit 409. As the filter coefficient, for example, one according to the sinc function can be used. The outer track resampled reproduction signal with the phases of each reproduction signal from Ch0 to Ch5 of the outer track reproduction signal corrected is output, and the outer track sum signal obtained by adding these signals at a predetermined ratio is output to the outer cross-correlation circuit 407.

[0066] The outer cross-correlation circuit 407 calculates the cross-correlation between the difference signal output by the target track difference signal generation circuit 401 and the outer track sum signal output by the outer phase correction filter 406. Similar to the inner cross-correlation circuit 403, the cross-correlation value Ca is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the signal waveform of the outer track sum signal from time Ts-1 to time Te-1. The cross-correlation value Cb is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the signal waveform of the outer track sum signal from time Ts to time Te. The cross-correlation value Cc is calculated between the signal waveform of the difference signal of the target track from time Ts to time Te and the signal waveform of the outer track sum signal from time Ts+1 to time Te+1. When the target track is the target groove section 302, in each reproduction signal detected through the division pattern 210, the crosstalk component due to the recording marks recorded on the outer land section 303 is largely included in the difference signal between Ch1 and Ch2 of the target track reproduction signal. Therefore, adjacent positions at the same angle can be detected based on the cross-correlation value between the difference signal of the target track and the outer land section. When the target track is a land, the crosstalk component due to the recording marks recorded on the outer groove section is largely included in the difference signal between Ch0 and Ch3 of the target track reproduction signal, and adjacent positions at the same angle can be detected in the same way based on the cross-correlation value.

[0067] The outer phase error detection circuit 408 obtains the phase error of the outer track sum signal with respect to the difference signal of the target track. The timing at which the cross-correlation value becomes maximum can be calculated by the least squares method of a quadratic function from the three cross-correlation values Ca, Cb, and Cc with shifted times. The calculated timing becomes the phase error between the current phase control value by the outer phase control circuit 409 and the target track reproduction signal.

[0068] Through the above operations of the resampling circuit 108, an inner track resampling signal and an outer track resampling reproduction signal that are resampled with high precision so as to be reproduction signals at adjacent same-angle positions with respect to the target track reproduction signal are obtained.

[0069] The PRML circuit 109 receives 18 reproduced signals that are resampled to have high-precision reproduced signals at adjacent same angular positions. By simultaneously inputting each resampled reproduced signal to the adaptive equalization circuit, the equalized reproduced signal obtained with the crosstalk component canceled is compared with the expected value waveform, and the expected value waveform closest to it is selected, and PRML signal processing is performed to output the pattern signal that is the source of the expected value waveform as the decoded signal.

[0070] The demodulation circuit 110 demodulates the encoded data from the decoded signal according to a predetermined modulation code.

[0071] The error correction decoding circuit 111 corrects the errors in the demodulated encoded data, and the result of restoring the user data is obtained in the memory circuit 113.

[0072] The system controller 114 controls to send the reproduced user data obtained in the memory circuit 113 to the host 116 through the I / F circuit 112, thereby completing the reproduction operation.

[0073] [3. Effects, etc.] As described above, in the first embodiment, according to the optical disk 100 and the optical disk apparatus 10, stable reproduction of data recorded on an optical disk with a high track density is enabled.

[0074] In the conventional crosstalk cancellation technology that uses the reproduction signals of three tracks, namely the target track, the inner track, and the outer track, there is no splitting of the light amount signal such as the splitting pattern 210, and the phase error with respect to the target track reproduction signal is obtained from the cross-correlation of the reproduction signals detected one by one for each track. In this case, the reproduction signal of the target track reproduction signal is a mixture of the crosstalk component due to the recording marks of the adjacent tracks and the component of the recording marks of the target track. With respect to the cross-correlation values with the reproduction signals of the inner track and the outer track, the component of the recording marks of the target track becomes an external disturbance, and the maximum value of the cross-correlation value, that is, the phase error cannot be accurately calculated. As a result, an error occurs in the phase relationship of each reproduction signal input to the PRML circuit, deteriorating the accuracy of the adaptive equalization circuit and reducing the crosstalk cancellation performance. That is, there is a limit to the performance of increasing the track density.

[0075] According to the first embodiment, by using the difference signal of the target track so that the component of the recording marks of the target track is suppressed to be small, the phase error can be calculated with high accuracy, and the crosstalk cancellation performance in the PRML circuit 109 can be maximally exerted.

Industrial Applicability

[0076] The present disclosure is applicable to an optical disc apparatus that performs data recording and reproduction.

Explanation of Signs

[0077] 10 Optical disc apparatus 100 Optical disc 101 Optical head 102 Spindle motor 103 Servo controller 104 Laser drive circuit 105 Modulation circuit 106 Error correction coding circuit 107 Reproduction signal detection circuit 108 Resampling circuit 109 PRML circuit 110 Demodulation circuit 111 Error correction decoding circuit 112 I / F circuit 113 Memory circuit 114 System controller 115 ROM 116 Host 201 Objective lens 202 Collimator lens 203 Laser mirror 204 Beam splitter 205 Objective lens controller 206 Collimator lens controller 207 Blue semiconductor laser 208 Control photodetector 209 Splitting element 210 Splitting pattern 211 Reproduction photodetector 301 Inner land portion 302 Target groove portion 303 Outer land portion 401 Target track difference signal generation circuit 402 Inner phase correction filter 403 Inner cross-correlation circuit 404 Inner phase error detection circuit 405 Inner phase control circuit 406 Outer phase correction filter 407 Outer cross-correlation circuit 408 Outer phase error detection circuit 409 Outer phase control circuit

Claims

【Claim 1】 An optical disk apparatus for recording and reproducing recorded data on an optical disk having a groove-shaped track and capable of recording the recorded data on the land portion and the groove portion of the groove, comprising: A laser with a wavelength λ is irradiated onto the track on the optical disk through an objective lens with a numerical aperture N, and the reflected light reflected and diffracted by the optical disk is divided into light fluxes in at least four or more regions including an outer end portion, an outer central portion, an inner central portion, and an inner end portion in the radial direction of the optical disk, and the light fluxes are received individually to output an outer end portion light amount signal, an outer central portion light amount signal, an inner central portion light amount signal, and an inner end portion light amount signal corresponding to the light amount. An optical pickup; A reproduction signal detection circuit that outputs an outer end portion reproduction signal, an outer central portion reproduction signal, an inner central portion reproduction signal, and an inner end portion reproduction signal generated by sampling the outer end portion light amount signal, the outer central portion light amount signal, the inner central portion light amount signal, and the inner end portion light amount signal respectively; A memory circuit that stores each first reproduction signal detected from a target track to be reproduced with the recorded data by the optical pickup and the reproduction signal detection circuit, each second reproduction signal detected from an inner adjacent track of the target track, and each third reproduction signal detected from an outer adjacent track of the target track; A resampling circuit that reads out each first reproduction signal, each second reproduction signal, and each third reproduction signal from the memory circuit and corrects the sampling timing of each second reproduction signal and each third reproduction signal based on each first reproduction signal; A decoding circuit that decodes the recorded data recorded on the target track from each first reproduction signal, each second resampled reproduction signal resampled by the resampling circuit, and each third resampled reproduction signal; The resampling circuit is configured to: When the target track is a groove portion: A correction condition is obtained using a first cross-correlation value between a difference signal between the first inner central portion reproduction signal and the first outer end portion reproduction signal and a sum signal of each second reproduction signal, and each second reproduction signal is resampled; A correction condition is obtained using a second cross-correlation value between a difference signal between the first outer central portion reproduction signal and the first inner end portion reproduction signal and a sum signal of each third reproduction signal, and each third reproduction signal is resampled; When the target track is a land portion: A correction condition is obtained using a third cross-correlation value between a difference signal between the first outer center reproduction signal and the first inner end reproduction signal and a sum signal of each of the second reproduction signals, and each of the second reproduction signals is resampled. An optical disc apparatus, characterized in that a correction condition is obtained using a fourth cross-correlation value between a difference signal between the first inner center reproduction signal and the first outer end reproduction signal and a sum signal of each of the third reproduction signals, and each of the third reproduction signals is resampled. **Claim 2** The resampling circuit When the target track is a groove portion A correction condition is obtained so that the first cross-correlation value is maximized, and each of the second reproduction signals is resampled. A correction condition is obtained so that the second cross-correlation value is maximized, and each of the third reproduction signals is resampled. When the target track is a land portion A correction condition is obtained so that the third cross-correlation value is maximized, and each of the second reproduction signals is resampled. The optical disc apparatus according to claim 1, characterized in that a correction condition is obtained so that the fourth cross-correlation value is maximized, and each of the third reproduction signals is resampled. **Claim 3** The resampling circuit An inner phase correction filter that corrects the phase of each of the second reproduction signals An inner cross-correlation circuit that calculates a first inner cross-correlation value from the waveform of the sum signal of the inner phase-corrected reproduction signals output from the inner phase correction filter with respect to the waveform from time Ts to time Te of a first difference signal obtained from two predetermined ones of the first reproduction signals, calculates a second inner cross-correlation value from the waveform from time Ts - 1 to time Te - 1 of the sum signal of the inner phase-corrected reproduction signals, and calculates a third inner cross-correlation value from the waveform from time Ts + 1 to time Te + 1 of the sum signal of the inner phase-corrected reproduction signals An inner phase error detection circuit that calculates a phase error between the first difference signal and the sum signal of the inner phase-corrected reproduction signals from the first inner cross-correlation value, the second inner cross-correlation value, and the third inner cross-correlation value An inner phase control circuit that controls the phase correction value of the inner phase correction filter based on the phase error detected by the inner phase error detection circuit An outer phase correction filter that corrects the phase of each of the third reproduction signals A first outer cross-correlation value is calculated from the waveform of the sum signal of the outer phase-corrected reproduction signals from time Ts to time Te with respect to the waveform from time Ts to time Te of a second difference signal obtained from two predetermined ones of the first reproduction signals. A second outer cross-correlation value is calculated from the waveform of the sum signal of the outer phase-corrected reproduction signals from time Ts−1 to time Te−1. A third outer cross-correlation value is calculated from the waveform of the sum signal of the outer phase-corrected reproduction signals from time Ts+1 to time Te+1. An outer cross-correlation circuit is provided for this purpose. An outer phase error detection circuit calculates a phase error between the second difference signal and the sum signal of the outer phase-corrected reproduction signals from the first outer cross-correlation value, the second outer cross-correlation value, and the third outer cross-correlation value. An outer phase control circuit controls a phase correction value of the outer phase correction filter based on the phase error detected by the outer phase error detection circuit. The optical disc apparatus according to claim 2 includes the outer phase control circuit.

Images