JP4816399B2 - Optical disk device - Google Patents

Description

  The present invention relates to an optical disc apparatus that extracts an MSK modulation component and an HMW modulation component from a wobble signal.

  In the next generation optical disc, the MSK (Minimum Shift Keying) modulation method and the HMW (Harmonic Wave) modulation method are used in combination as the addressing method of the recordable optical disc. In the MSK modulation method, a part of the fundamental frequency signal (reference carrier signal) of the wobble signal is replaced with a signal having a frequency of 1.5 times, and addressing is performed by detecting this frequency modulation unit. In the HMW modulation system, a wobble signal is sawtooth-shaped by superimposing a signal having a frequency twice that of a reference carrier signal, and addressing is performed by detecting the phase of the superimposed signal. The MSK modulation unit and the HMW modulation unit are arranged at different positions in the block, and a reference carrier signal of one cycle or more is arranged between the MSK modulation unit and the HMW modulation unit. The MSK modulation method is relatively weak against scratches and crosstalk, and the HMW modulation method has a characteristic that it is sensitive to tilt, and the reliability of addressing is improved by complementing both in combination. .

JP 2003-123249 A

  However, as a method of demodulating a wobble signal subjected to MSK modulation and HMW modulation, a heterodyne method is generally used as disclosed in the above publication, and a multiplier, an integrator, a sample hold circuit, a comparator, and the like are required. This complicates the circuit configuration.

  An object of the present invention is to provide an optical disc apparatus that can extract MSK modulation components and HMW modulation components with a simpler configuration.

  The present invention is an optical disc apparatus for recording or reproducing an optical disc in which a recording track is formed according to a wobble signal and the wobble signal is MSK modulated, and a pickup for reading out the wobble signal from the optical disc, A first filter having a passband of 1 and passing through a reference frequency component and an MSK modulation component of the wobble signal and removing an RF noise component; and a second filter having a passband of the wobble signal. A second filter that passes through and removes the MSK modulation component and the RF noise component; and a differentiator that outputs a difference between the output of the first filter and the output of the second filter.

  Further, the present invention is an optical disc apparatus for recording or reproducing an optical disc in which a recording track is formed according to a wobble signal and the wobble signal is HMW modulated, and a pickup for reading out the wobble signal from the optical disc. A first filter having a first passband, passing a reference frequency component of the wobble signal and removing an HMW modulation component and an RF noise component, and having a second passband, the reference frequency of the wobble signal A second filter that passes the component and the HMW modulation component and removes the RF noise component; and a differentiator that outputs a difference between the output of the first filter and the output of the second filter.

  Further, the present invention is an optical disc apparatus in which a recording track is formed according to a wobble signal, and the wobble signal is recorded or reproduced with respect to an optical disc on which MSK modulation and HMW modulation are performed, and the wobble signal is received from the optical disc. A pickup for reading, a first filter having a first pass band, passing a reference frequency component of the wobble signal, and removing an MSK modulation component, an HMW modulation component, and an RF noise component, and a second pass band A second filter that passes the reference frequency component and the MSK modulation component of the wobble signal and removes the HMW modulation component and the RF noise component; and a third passband, and the reference frequency component of the wobble signal and the MSK modulation component And a third filter that passes the HMW modulation component and removes the RF noise component, and the output of the first filter and the previous filter A first differentiator which outputs the difference between the output of the second filter, and having a second differentiator which outputs the difference between the outputs of the third and the second filter and the output of the filter.

  According to the present invention, it is possible to easily extract the MSK modulation component or the HMW modulation component by the configuration of the filter and the differentiator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an optical disc apparatus according to the present embodiment. An optical disk 10 such as Blu-ray is driven by a spindle motor (SPM) 12. The spindle motor SPM 12 is driven by a driver 14, and the driver 14 is servo-controlled by a servo processor 30 so as to have a desired rotation speed. The optical disk 10 has information tracks meandering in accordance with the wobble signal, and the wobble signal is subjected to MSK modulation and HMW modulation. Address information is embedded in the MSK modulation unit and the HMW modulation unit, and the address information can be obtained by extracting and demodulating the MSK modulation component and the HMW modulation component from the wobble signal. In the MSK modulation, one is set to the same frequency as the reference carrier signal, and the other is set to a signal having a frequency 1.5 times that of the reference carrier signal. That is, one of the signal waveforms used for MSK modulation is cos (ωt) or -cos (ωt), and the other is cos (1.5 ωt) or -cos (1.5 ωt). When inserting modulated data into the wobble signal using the MSK modulation method, the data stream of the modulated data is subjected to differential encoding processing in units of clocks corresponding to the wobble period to obtain precoded data. MSK modulation is performed to generate an MSK stream. Thereby, when the data string of the modulated data is “010”, for example, the signal waveform of the MSK stream is cos (ωt), cos (ωt), cos (1.5ωt), −cos (ωt) for each wobble period. ), −cos (1.5ωt), cos (ωt) (see Patent Document 1 above). In HMW modulation, sin (2ωt) and −2sin (ωt), which are second harmonics of the reference carrier signal cos (ωt), are used. When the modulated data is “1”, sin (2ωt) is used as the reference carrier signal. When the modulated data is “0”, modulation is performed by superimposing −sin (2ωt) on the reference carrier signal.

  The optical pickup 16 includes a laser diode (LD) for irradiating the optical disk 10 with laser light and a photodetector (PD) that receives reflected light from the optical disk 10 and converts it into an electrical signal, and is disposed opposite to the optical disk 10. . The optical pickup 16 is driven in the radial direction of the optical disk 10 by a sled motor 18 constituted by a stepping motor, and the sled motor 18 is driven by a driver 20. The driver 20 is servo-controlled by the servo processor 30 similarly to the driver 14. The LD of the optical pickup 16 is driven by a driver 22, and the driver 22 is controlled by an auto power control circuit (APC) 24 so that the drive current becomes a desired value. The APC 24 and the driver 22 control the light emission amount of the LD according to a command from the system controller 32. Although the driver 22 is provided separately from the optical pickup 16 in the figure, the driver 22 may be mounted on the optical pickup 16.

  When data recorded on the optical disk 10 is reproduced, a laser beam of reproduction power is irradiated from the LD of the optical pickup 16, and the reflected light is converted into an electric signal by the PD and output. A reproduction signal from the optical pickup 16 is supplied to the RF circuit 26. The RF circuit 26 generates a focus error signal and a tracking error signal from the reproduction signal and supplies them to the servo processor 30. The servo processor 30 servo-controls the optical pickup 16 based on these error signals, and maintains the optical pickup 16 in an on-focus state and an on-track state. Further, the RF circuit 26 supplies an address signal included in the reproduction signal to the address decoding circuit 28. The address decoding circuit 28 demodulates the address data of the optical disk 10 from the address signal and supplies it to the servo processor 30 and the system controller 32.

  The address signal is a wobble signal. The wobble signal is extracted from the reproduction signal and decoded to obtain address data. The demodulation of the wobble signal, more specifically, the extraction and demodulation of the MSK modulation component and the HMW modulation component from the wobble signal will be described later. Further, the RF circuit 26 supplies the reproduction RF signal to the binarization circuit 34. The binarization circuit 34 binarizes the reproduction signal and supplies the obtained signal to the encoding / decoding circuit 36. The encode / decode circuit 36 demodulates the binary signal and corrects errors to obtain reproduction data, and outputs the reproduction data to a host device such as a personal computer via the interface I / F 40. When the reproduction data is output to the host device, the encoding / decoding circuit 36 temporarily stores the reproduction data in the buffer memory 38 and outputs it.

  When recording data on the optical disk 10, data to be recorded from the host device is supplied to the encode / decode circuit 36 via the interface I / F 40. The encode / decode circuit 36 stores data to be recorded in the buffer memory 38, encodes the data to be recorded, and supplies the data to the write strategy circuit 42 as modulated data. The write strategy circuit 42 converts the modulation data into a multi-pulse (pulse train) according to a predetermined recording strategy, and supplies it to the driver 22 as recording data. Since the recording strategy affects recording quality, optimization is performed prior to data recording. That is, test data is test-written by changing the recording strategy in a predetermined test area of the optical disc 10, and the test data that has been test-written is reproduced and its signal quality is evaluated. Then, the optimum recording strategy is selected based on the evaluation result. The laser light whose power is modulated by the recording data is irradiated from the LD of the optical pickup 16 and the data is recorded on the optical disk 10. After recording the data, the optical pickup 16 reproduces the recorded data by irradiating a laser beam with a reproduction power, and supplies it to the RF circuit 26. The RF circuit 26 supplies the reproduction signal to the binarization circuit 34, and the binarized data is supplied to the encode / decode circuit 36. The encoding / decoding circuit 36 decodes the modulated data and collates it with the recording data stored in the buffer memory 38. The result of the verification is supplied to the system controller 32. The system controller 32 determines whether to continue recording data or execute a replacement process according to the result of verification. The system controller 32 controls the operation of the entire system, drives the sled motor 18 via the servo processor 30, and controls the position of the optical pickup 16.

  FIG. 2 is a block diagram showing the configuration of the address decoding circuit 28 in FIG. The address decoding circuit 28 is roughly composed of an MSK component demodulation circuit and an HMW component demodulation circuit.

  The MSK component extraction unit 28a receives the wobble signal from the RF circuit unit 26, extracts the MSK modulation component included in the wobble signal, and outputs it to the MSK binarization unit 28c. The MSK component extraction unit 28a easily extracts an MSK modulation component by a combination of two low-pass filters and one differencer.

  The MSK binarization unit 28c binarizes the MSK modulation component using the clock signal CLK generated by the PLL unit 28f, and outputs the binarized signal to the decoder 28e.

  The HMW component extraction unit 28c receives the wobble signal from the RF circuit unit 26, extracts the HMW modulation component included in the wobble signal, and outputs it to the HMW binarization / polarity determination unit 28d. The HMW component extraction unit 28b easily extracts an HMW modulation component by a combination of two low-pass filters and one differencer.

  The HMW binarization / polarity determination unit 28d binarizes the HMW modulation component using the clock signal CLK generated by the PLL unit 28f, further determines the polarity (0 or 1), and outputs it to the decoder 28e. The decoder 28e demodulates the address information from the MSK modulation component and the HMW modulation component using the clock signal CLK generated by the PLL unit 28f, and outputs the obtained address information to the system controller 32.

  FIG. 3 shows a configuration block diagram of the MSK component extraction unit 28a in FIG. The MSK component extraction unit 28a includes two low-pass filters 28a2 (LPF1) and 28a1 (LPF2) and a differentiator 28a3. LPF1 and LPF2 are connected in parallel to each other, and the wobble signal is supplied to LPF1 and LPF2.

  The LPF 1 has a cutoff frequency set between the frequency of the reference carrier signal of the wobble signal and a frequency that is 1.5 times the frequency of the reference carrier signal, and passes the reference carrier signal of the wobble signal while being MSK-modulating. Components, HMW modulation components, and RF noise components are removed. The signal B output from the LPF 1, that is, the signal including the reference carrier signal is supplied to the inverting input terminal (−) of the differentiator 28 a 3.

  LPF2 has a cutoff frequency set between 1.5 times the frequency of the reference carrier signal and twice the frequency of the reference carrier signal, while the reference carrier signal and the MSK modulation component of the wobble signal pass through, while the HMW Removes modulation components and RF noise. The signal A output from the LPF 2, that is, the signal including the reference carrier signal and the MSK modulation component is supplied to the non-inverting input terminal (+) of the differencer 28a3.

  The differentiator 28a3 can extract only the MSK modulation component by calculating the difference between the signal A and the signal B.

  FIG. 4 shows a configuration block diagram of the HMW component extraction unit 28b in FIG. The HMW component extraction unit 28b includes two low-pass filters 28b1 (LPF3) and 28b2 (LPF2) and a differentiator 28b3. LPF2 and LPF3 are connected in parallel to each other, and the wobble signal is supplied to LPF2 and LPF3.

  LPF2 is the same as LPF2 shown in FIG. 3, and passes the reference carrier signal and the MSK modulation component in the wobble signal. The signal D that has passed through the LPF 2, that is, the signal including the reference carrier signal and the MSK modulation component, is supplied to the inverting input terminal (−) of the differentiator b3.

  The LPF 3 is set to a frequency whose cutoff frequency is larger than twice the frequency of the reference carrier signal, and passes the reference carrier signal, the MSK modulation component, and the HMW modulation component in the wobble signal, while removing the RF noise component. The signal C that has passed through the LPF 3, that is, the signal including the reference carrier signal, the MSK modulation component, and the HMW modulation component is supplied to the non-inverting input terminal (+) of the differencer 28b3.

  The differentiator 28b3 can extract only the HMW modulation component by calculating the difference between the signal C and the signal D.

  FIG. 5 shows the frequency characteristics of the LPFs 1 to 3 shown in FIGS. In the figure, fW is the frequency of the reference carrier signal of the wobble signal, fM is 1.5 times the frequency of the reference carrier signal and the frequency of the MSK modulation component, and fH is the frequency twice the reference carrier signal. It is the frequency of the HMW modulation component. The LPF 1 has a band pass characteristic indicated by a characteristic 100 and passes only the reference carrier signal. The LPF 2 has a band pass characteristic indicated by a characteristic 200, and passes only the reference carrier signal and the MSK modulation component. The LPF 3 has a band pass characteristic indicated by a characteristic 300, and passes the reference carrier signal, the MSK modulation component, and the HMW modulation component. From this figure, it will be understood that the MSK modulation component is extracted by the combination of LPF1 and LPF2, and the HMW modulation component is extracted by the combination of LPF2 and LPF3.

  FIG. 6 shows the signal waveform of the MSK modulation component, which is the difference calculation result in the differentiator 28a3. In the figure, signal B from LPF1 (shown by a thin line) and signal A from LPF2 (shown by a broken line) are also shown. Since the differencer 28a3 calculates the signal A−the signal B, the MSK modulation component 400 obtained by inverting the polarity of the MSK modulation component included in the signal A is extracted. FIG. 7 shows only the MSK modulation component 400 extracted from FIG.

  FIG. 8 also shows the signal waveform of the HMW modulation component, which is the difference calculation result in the differentiator 28b3. In the figure, the signal D from the LPF 2 (shown by a broken line) and the signal C from the LPF 3 (shown by a thin line) are also combined. Show. FIG. 9 shows only the HMW modulation component 500 extracted from FIG.

  Thus, in the present embodiment, the MSK modulation component can be extracted from the wobble signal and the HMW modulation component can be extracted from the combination of two low-pass filters and one differencer. The extracted MSK modulation component and HMW modulation component may be binarized and demodulated by an arbitrary method. Hereinafter, an example of demodulation will be described, but the present invention is not limited to this.

  FIG. 10 shows the demodulation processing of the MSK modulation component. This is processing of the MSK unit binarization unit 28c in FIG. The MSK unit binarization unit 28c includes a full-wave rectifier circuit, a peak detection circuit, a slice circuit, and a latch circuit. FIG. 10A shows the clock signal CLK generated by the PLL unit 28f shown in FIG. 2, which is the reference frequency of the wobble signal. FIG. 10B shows the MSK modulation component extracted by the MSK component extraction unit 28a. FIG. 10C shows a waveform (broken line in the figure) obtained by performing peak detection after full-wave rectification of the MSK modulation component shown in FIG. 10B. This peak waveform is binarized by a slice circuit using a predetermined slice level SL1. FIG. 10D shows an output waveform binarized at the slice level SL1. FIG. 10E is a signal obtained by latching the binarized signal with the clock signal CLK of FIG. 10A, and is an MSK signal to be output.

  FIG. 11 shows a demodulation process of the HMW modulation component. This is processing of the HMW unit binarization / polarity determination unit 28d in FIG. The HMW unit binarization / polarity determination unit 28d includes a slice circuit, a latch circuit, an OR gate, and an AND gate. FIG. 11A shows the clock signal CLK generated by the PLL unit 28f, and FIGS. 10B and 10C show the second clock signal CLK2 and the third clock signal generated by dividing the clock signal CLK. CLK3. CLK2 and CLK3 are clocks having a cycle twice that of CLK, and are signals having opposite phases to each other. FIG. 10D shows the HMW modulation component extracted by the HMW component extraction unit 28b. The HMW modulation component is binarized at predetermined slice levels SL2 and SL3. SL2> SL3. FIG. 11E shows a signal HMW binarized by SL2, and FIG. 11F shows a signal binarized by SL3. FIG. 11G shows a signal obtained by latching the signal binarized by SL2 with CLK2, and FIG. 11H shows a signal obtained by latching the signal binarized by SLS3 with CLK2. FIG. 11 (h) is a signal obtained by latching the signal binarized by SL3 with CLK3, and FIG. 11 (i) is a signal obtained by latching the signal binarized by SL2 with CLK3. FIG. 11K is a logical product signal of a signal obtained by latching SL2 with CLK2 and a signal obtained by latching SL2 with CLK3, and is a signal having a polarity of “1”. FIG. 11 (m) is a signal obtained by calculating a logical product of a signal obtained by latching SL3 with CLK2 and a signal obtained by latching SL3 with CLK3, and is a signal having a polarity of “0”. Further, FIG. 11 (n) is a logical sum signal of the signal of FIG. 11 (k) and the signal of FIG. 11 (m), and is a signal output as an HMW signal. When the HMW signal is “0” or low level, there is no HMW signal, and it is determined as a reference frequency signal (so-called monotone signal) of the wobble signal.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible. For example, in the present embodiment, the case of demodulating address information from a wobble signal that has been subjected to MSK modulation and HMW modulation has been illustrated, but an MSK modulation component is extracted from a signal that is only MSK modulated, or only HMW modulation is performed. The present invention can also be applied to a case where an HMW modulation component is extracted from a signal.

1 is an overall configuration diagram of an optical disc device. It is a block diagram of an address decoding circuit. It is a block diagram of a MSK component extraction part. It is a block diagram of a HMW component extraction part. It is a characteristic view of a low-pass filter. It is extraction explanatory drawing of a MSK modulation component. It is a signal waveform diagram of an MSK modulation component. It is extraction explanatory drawing of a HMW modulation component. It is a signal waveform diagram of an HMW modulation component. It is a timing chart which shows the demodulation process of a MSK modulation component. It is a timing chart which shows the demodulation process of a HMW modulation component.

Explanation of symbols

  10 optical disk, 28 address decoding circuit, 28a MSK component extraction unit, 28b HMW component extraction unit, 400 MSK modulation component, 500 HMW modulation component.

Claims (4)

An optical disc apparatus for recording or reproducing an optical disc in which a recording track is formed according to a wobble signal and the wobble signal is MSK modulated,
A pickup for reading out the wobble signal from the optical disc;
A first filter that has a first passband, passes a reference frequency component and an MSK modulation component of the wobble signal, and removes an RF noise component;
A second filter having a second passband, passing a reference frequency component of the wobble signal and removing an MSK modulation component and an RF noise component;
A differentiator for outputting a difference between the output of the first filter and the output of the second filter;
An optical disc apparatus comprising: An optical disc apparatus for recording or reproducing an optical disc in which a recording track is formed according to a wobble signal and the wobble signal is HMW modulated,
A pickup for reading out the wobble signal from the optical disc;
A first filter having a first passband and passing a reference frequency component of the wobble signal and removing an HMW modulation component and an RF noise component;
A second filter having a second passband, passing through a reference frequency component and an HMW modulation component of the wobble signal, and removing an RF noise component;
A differentiator for outputting a difference between the output of the first filter and the output of the second filter;
An optical disc apparatus comprising: An optical disc apparatus in which a recording track is formed according to a wobble signal, and the wobble signal is recorded or reproduced on an optical disc on which MSK modulation and HMW modulation are performed,
A pickup for reading out the wobble signal from the optical disc;
A first filter having a first passband, passing a reference frequency component of the wobble signal and removing an MSK modulation component, an HMW modulation component, and an RF noise component;
A second filter having a second passband, passing a reference frequency component and an MSK modulation component of the wobble signal, and removing an HMW modulation component and an RF noise component;
A third filter having a third passband and passing through a reference frequency component, an MSK modulation component and an HMW modulation component of the wobble signal, and removing an RF noise component;
A first differentiator that outputs a difference between the output of the first filter and the output of the second filter;
A second differentiator that outputs a difference between the output of the third filter and the output of the second filter;
An optical disc apparatus comprising: The apparatus of claim 3.
The MSK modulation component has a frequency 1.5 times the reference frequency;
The HMW modulation component has a frequency twice the reference frequency,
The cutoff frequency of the first filter is set between the reference frequency and the frequency of the MSK modulation component,
The cutoff frequency of the second filter is set between the frequency of the MSK modulation component and the frequency of the HMW modulation component,
An optical disc apparatus, wherein a cutoff frequency of the third filter is set to be larger than a frequency of the HMW modulation component.

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