JP2008059713A - Processing circuit and processing method for optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing circuit in an optical disk device, improving reproduction performance of a recording area and ID reading ratio of a header area. <P>SOLUTION: The processing circuit of the optical disk device is provided with an AD converter 9, a PLL circuit 10 for synchronizing a data signal with a sampling clock of analog/digital conversion based on a signal obtained by the AD converter 9, a waveform equalizer circuit 11 for equalizing the waveform of the signal obtained by the AD converter 9, a first DC elimination circuit 13a for eliminating a DC component of the signal whose waveform has been equalized by the waveform equalizer circuit 11, a second DC elimination circuit 13b for eliminating the DC component of the signal whose waveform has been equalized by the waveform equalizer circuit 11, a switch b12b for switching output signals between the first and second DC elimination circuits 13a and 13b based on a switching signal and outputting the resulting signals, and a maximum likelihood decoding circuit 15 for applying maximum likelihood-decoding to the output signal of the switch b12b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a processing circuit of an optical disc apparatus that optically reproduces or records and reproduces a signal from a disc, and more particularly to a technique that is effective when applied to a signal processing method for improving reproduction performance and ID acquisition rate.

Conventionally, as a processing circuit of an optical disc apparatus, there has been a technique described in JP-A-2005-190618 (Patent Document 1). This is because the signal reproduced from the disk is used, the ratio of asymmetry is detected from the reproduced signal processing system, the signal processing is optimized, and even when the adaptive equalization processing and the maximum likelihood decoding method are used. Thus, the asymmetry ratio can be easily estimated, and a disk having a large asymmetry can be reproduced.
JP 2005-190618 A

  However, in the technique described in Patent Document 1, the ratio of fluctuation from the center level (asymmetry) is based on the relationship between the phase error integrated output of the PLL and the phase error threshold or the relationship between the adaptive equalization error integrated output and the equalization error threshold. Therefore, it is necessary to read the recording information on the medium for a certain period of time because the sampling timing is not changed from the center level of the read signal.

  For example, the DVD-RAM disk 50 shown in FIG. 6 has the following problems.

  The DVD-RAM disc 50 shown in FIG. 6 includes a recording area (Recording field) made of a phase change recording film and a header area (Header field) made of embossed pits in which a physical ID is embedded (preformatted). A mirror area (Mirr field) is mixed.

  Further, in this header area, the embossed pit positions are slightly shifted in the track direction in order to give addresses to both areas called “Land” and “Groove”.

  As in the format shown in FIG. 6, in the DVD-RAM, one sector is 2697 bytes, the recording area is 2567 bytes, the header area is 128 bytes, and the MIRR area is 2 bytes. As can be seen, the header area is about 1/20 shorter than the recording area.

  In reproduction of such a medium, there is a problem that fluctuations from the center level cannot be removed particularly in a header area having a short area due to the influence of each area. In addition, if the follow-up speed of the adaptive equalization means is increased in order to detect the fluctuation in the short header area, sudden fluctuations are detected in the recording area, and it is impossible to correctly determine the fluctuation ratio from the center level. There was a problem.

  The present invention provides a circuit for removing a DC component by a time constant capable of detecting a variation (DC component) from the center level of independent read signals for a recording area and a header area when reproducing a DVD-RAM disk or the like. By using the optical disk, the fluctuation (DC component) from the central level of the read signal can be removed without being affected by each area, and the reproduction performance of the recording area and the ID area reading rate of the header area can be improved. An object is to provide a processing circuit in an apparatus.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The processing circuit of the optical disk device according to the present invention is an optical disk device processing circuit that optically reproduces or records / reproduces a disk, and includes an optical pickup for focusing the laser beam on the disk. An analog-to-digital converter that performs analog-to-digital conversion of an analog input signal with a predetermined clock, and a first component that removes a DC component of the signal analog-to-digital converted by the analog-to-digital converter using a first time constant DC removing circuit, a second DC removing circuit that removes the DC component of the signal analog-to-digital converted by the analog-to-digital converter using the second time constant, and a switching signal corresponding to the structure of the disk Based on the first DC removal circuit and the second DC removal circuit. And pitch, in which a demodulation circuit for demodulating an output signal of the first switch.

  The processing circuit of the optical disc apparatus according to the present invention is a processing circuit of the optical disc apparatus that includes an optical pickup for focusing the laser beam on the disc and optically reproduces or records / reproduces the disc. An analog-to-digital converter that performs analog-to-digital conversion of the regenerated analog input signal at a predetermined clock, a waveform equalization circuit that equalizes the waveform of the analog-to-digital converted signal by the analog-to-digital converter, and waveform equalization A first DC removal circuit for removing a DC component of the signal whose waveform is equalized by the circuit using a first time constant; and a DC component of the signal whose waveform is equalized by the waveform equalization circuit. 2 based on the switching signal corresponding to the structure of the disk, the second DC removal circuit for removing using the time constant of 2, and the output signal of the first DC removal circuit and the second A first switch for outputting by switching the output signal of the flow reduction circuit, in which a demodulation circuit for demodulating an output signal of the first switch.

  The signal processing method of the optical disc apparatus is a signal processing method of the optical disc apparatus that includes an optical pickup for focusing the laser beam on the disc and optically reproduces or records / reproduces the disc. The analog input signal is converted from analog to digital with a predetermined clock, and the DC component of the analog / digital converted signal is converted into a first time constant or a second time constant based on a switching signal corresponding to the disk structure. Is used to demodulate the signal from which the DC component has been removed.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, even when a plurality of areas having different characteristics such as a recording area and a header area exist on a medium like a DVD-RAM disc, the DC component of the reproduction signal can be removed in each area. It is possible to improve the reproduction performance and the ID acquisition rate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  With reference to FIG. 1, the configuration of a processing circuit of an optical disc apparatus according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a processing circuit of an optical disc apparatus according to an embodiment of the present invention, and shows an overall configuration of the optical disc apparatus including a processing circuit of the optical disc apparatus.

  In FIG. 1, the processing circuit of the optical disk apparatus includes a signal processing circuit 7, a servo circuit 8, an analog / digital (AD) converter 9, a phase-locked circuit (hereinafter referred to as a PLL circuit) 10, a waveform, and the like. Circuit 11, switch a12a, switch b12b, switch c12c, first DC removal circuit 13a, second DC removal circuit 13b, first time constant set in first and second DC removal circuits 13a, 13b 14a, a second time constant 14b, a maximum likelihood decoding circuit 15, and a demodulation / error correction circuit 16.

  The optical disk apparatus includes a disk 1, a clamper 2a, a turntable 2b, an objective lens 3, a pickup 4, a thread motor 5, and a spindle motor 6, and is configured to read information on the disk 1.

  The overall operation of the optical disk apparatus including the processing circuit of the optical disk apparatus according to one embodiment of the present invention will be described below.

  First, the disk 1 set on the turntable 2b is fixed to the turntable 2b by a clamper 2a. The disk rotates as the spindle motor 6 rotates.

  The signal processing circuit 7 uses the signal processing circuit 7 to focus the objective lens 3 in the focus direction (perpendicular to the disc) and the tracking direction (parallel to the disc) from a signal obtained by irradiating the disc 1 with laser light from the pickup 4 and detecting the light reflected by the disc 1. Is generated, and this signal is supplied to the servo circuit 8.

  The servo circuit 8 performs feedback control using a delay compensator, a lead compensator, etc., and generates a control signal for moving the objective lens 3 in the focus direction (a direction perpendicular to the disk) and the tracking direction (a direction parallel to the disk). By this control signal, the objective lens 3 is controlled in the direction perpendicular to the disk, and the focus control of the feedback loop is realized to keep the focus point always.

  In addition, the objective lens 3 is also controlled in the tracking direction by this control signal, and tracking control of the feedback loop is realized and the on-track state always on the pit on the recording surface of the disk 1 is maintained.

  The servo circuit 8 performs feedback control using a delay compensator or a lead compensator from the tracking control state described above, and generates a control signal for controlling the sled motor 5 in accordance with the deviation of the objective lens 3 in the tracking direction. Then, the sled motor 5 is operated to move the pickup 4 itself.

  The signal processing circuit 7 performs feedback control using the rotation cycle information read from the disk 1 and generates a signal for controlling the spindle motor 6 in the servo circuit 8 based on the rotation cycle information to operate the spindle motor 6. Let

  The above is the reproduction state in which the objective lens 3 is further in the on-track position on the focal point and the focus, tracking, spindle and thread are controlled in the steady state.

  At this time, the pickup 4 irradiates the disk 1 with laser light, detects the amount of reflected light or deflection thereof, and reads information on the disk 1. The reproduction signal read by the pickup 4 is supplied to the signal processing circuit 7.

  The signal processing circuit 7 adjusts and outputs the amplitude level and frequency characteristics of the supplied reproduction signal. The adjusted reproduction signal is supplied to the AD converter 9, and the AD converter 9 converts the analog signal into a digital signal.

  The digitally converted reproduction signal is supplied to the PLL circuit 10, and the phase of the reproduction clock generated in the PLL circuit 10 is synchronized with the inputted reproduction signal.

  Here, an example of the PLL circuit 10 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the PLL circuit of the processing circuit of the optical disc apparatus according to the embodiment of the present invention.

  In FIG. 2, the PLL circuit 10 includes a phase error detection circuit 20, a loop filter 21, and a voltage controlled oscillator (hereinafter referred to as a VCO) 22.

  The phase error detection circuit 20 detects the phase error between the input reproduction signal and the reproduction clock generated by the VCO 22 and supplies the phase error to the loop filter. The loop filter 21 adjusts the gain of the input phase error signal. The phase error signal whose gain is adjusted by the loop filter 21 is supplied to the VCO 22.

  The VCO 22 oscillates a clock corresponding to the value of the phase error signal and generates it as a recovered clock. With the above configuration, the phase of the reproduction clock can be synchronized with the inputted reproduction signal.

  On the other hand, the reproduction signal digitally converted by the AD converter 9 is supplied to the waveform equalization circuit 11, which adjusts the amplitude level and frequency characteristics to equalize the waveform of the reproduction signal.

  A signal obtained by equalizing this waveform is supplied to the switch a12a. The signal supplied to the switch a12a is supplied to the first DC removal circuit 13a and the second DC removal circuit 13b.

  The first DC removing circuit 13a and the second DC removing circuit 13b remove the DC component of the signal obtained by equalizing the supplied waveform. The signals from which the DC component is removed by the first DC removal circuit 13a and the second DC removal circuit 13b are respectively supplied to the switch b12b.

  Either the signal from which the DC component has been removed by the first DC removal circuit 13a and the signal from which the DC component has been removed by the second DC removal circuit 13b supplied to the switch b12b is selected and output by the switching signal.

  As the switching signal, for example, a control signal for performing signal processing of a recording area and a header of a reproduction signal is used as a switching signal in an optical disc apparatus.

  The signal output from the switch b12b is supplied to the switch c12c. Either the output from the waveform equalization circuit 11 supplied to the switch c12c or the signal output from the switch b12b is selected and output by the ON / OFF signal.

  As the ON / OFF signal, for example, in an optical disc apparatus, a signal for switching processing is used as an ON / OFF signal depending on the stability of a reproduction signal.

  The signal output from the switch c12c is supplied to the maximum likelihood decoding circuit 15, and the maximum likelihood decoding circuit 15 decodes the reproduction signal. The decoded reproduction signal is supplied to the demodulation / error correction circuit 16, and the demodulation / error correction circuit 16 performs demodulation and error correction processing of the reproduction signal.

  Here, an example of the first DC removal circuit 13a and the second DC removal circuit 13b will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the DC removal circuit of the processing circuit of the optical disk apparatus according to one embodiment of the present invention.

  In FIG. 3, the DC removal circuits 13 a and 13 b are each composed of a zero cross detection circuit 30, subtractors 31 a and 31 b, multipliers 32 a and 32 b, an adder 33, and a delay register 34.

  Hereinafter, the operation of the DC removal circuits 13a and 13b will be described.

  First, the reproduction signal output from the waveform equalization circuit 11 is input to the zero cross detection circuit 30. The zero cross detection circuit 30 detects the difference in phase between a state where the signal output from the waveform equalization circuit 11 crosses a certain slice level and the reproduced clock at that time as amplitude information of the signal waveform.

  This state will be described with reference to FIG. FIG. 4 is an explanatory diagram for explaining the detection state of the DC removal circuit of the processing circuit of the optical disk apparatus according to the embodiment of the present invention. FIG. 4 shows an input reproduction signal and a reproduction clock generated by the PLL circuit 10.

  In FIG. 4, in the case of (A), there is no difference between the phase of the reproduction signal and the phase of the reproduction clock, that is, the reproduction signal has no DC component, and in the case of (B), the reproduction signal. There is a difference in the phase of the reproduction clock and the point that crosses the slice level, that is, a DC component remains in the reproduction signal.

  The DC component signal detected by the zero cross detection circuit 30 is input to the subtractor 31a.

  On the other hand, the output signal from the delay register 34 is input to the subtractor 31a.

  The subtractor 31a supplies the multiplier 32a with the result of subtracting the output value of the delay register 34 from the output value of the zero-cross detection circuit 30. A time constant based on the time constant 14a or the time constant 14b is set in advance in the multiplier 32a, and a result obtained by multiplying the time constant by the output value from the subtractor 31a is supplied to the adder 33.

  On the other hand, the output from the multiplier 32 b is supplied to the adder 33. The adder 33 adds the output of the multiplier 32 a and the output of the multiplier 32 b and supplies the result to the delay register 34.

  The output of the adder 33 supplied to the delay register 34 is the phase of a state where the reproduction signal output from the waveform equalization circuit 11 next to the zero cross detection circuit 30 crosses a certain slice level and the reproduction clock at that time. The output of the adder 33 is held until the difference is detected as the amplitude information of the reproduction signal waveform.

  The output of the delay register 34 is supplied to the multiplier 32b. A time constant 14a or a time constant based on the time constant 14b is set in advance in the multiplier 32b, and the result obtained by multiplying the time constant by the output value from the delay register 34 is supplied to the adder 33.

  The multiplier 32a, the adder 33, the delay register 34, and the multiplier 32b constitute a digital filter, and a low-pass filter (low-pass filter) is realized by a time constant set in the multiplier 32a and the multiplier 32b.

  By passing the DC component detected by the zero-cross detection circuit 30 through the low-pass filter, it is possible to detect only a steady DC component without detecting a wide-range noise component or a sudden DC component.

  The detected steady DC component is the output of the delay register 34, and this output is supplied to the subtractor 31b. The other input reproduction signal is supplied to the subtractor 31b.

  The subtractor 31b supplied with the output from the delay register 34 and the input reproduction signal subtracts the output from the delay register 34 from the input reproduction signal and outputs the result.

  This output signal is a signal obtained by constantly subtracting the DC component from the input signal, that is, a reproduction signal obtained by removing the steady DC component from the input reproduction signal.

  Here, the operation of the switch a12a, the switch b12b, and the switch c12c when reproducing the DVD-RAM disc will be described with reference to FIG. FIG. 5 is an explanatory diagram for explaining the operation of each switch of the processing circuit of the optical disc apparatus according to the embodiment of the present invention.

  As shown in FIG. 6 described above, a DVD-RAM disc has a recording area (Recording field) and a header area (Header field) in which a physical ID is embedded.

  At this time, for example, when the switching signal is controlled to be “HIGH” in the header area and “LOW” in the recording area, the switch a12a is on the A side when the switching signal is “HIGH” and is “LOW”. Switch to B side.

  The switch b12b is switched to the C side when the switching signal is “HIGH” and switched to the D side when the switching signal is “LOW”.

  In short, the first DC removal circuit 13a operates when the switching signal is “HIGH”, and the second DC removal circuit 13b operates when the switching signal is “LOW”.

  At this time, the value of the first time constant 14a is set so that the time constant can be reduced so that the DC component can be removed in a short time for the header area in the first DC removing circuit 13a. Can be removed.

  The second DC removal circuit 13b is set to a value that increases the second time constant 14b so that the DC component can be removed in a long time for the recording area, so that the steady DC component can be removed. Like that.

  As a result, it is possible to remove direct current having different time constant characteristics between the header area and the recording area.

  Further, in order to perform the decoding process with the output of the waveform equalization circuit 11 without using this direct current removal circuit, when the ON / OFF signal is turned OFF (“LOW”), the switch c12c becomes the F side and the waveform etc. The output of the conversion circuit 11 is supplied to the maximum likelihood decoding circuit 15 via the switch c12c.

  When the ON / OFF signal is turned ON ("HIGH"), the switch c12c is set to the E side, and the output of the switch b12b in which the output of either the first DC removal circuit 13a or the second DC removal circuit 13b is selected is the switch. The maximum likelihood decoding circuit 15 is supplied via c12c.

  As described above, according to the present embodiment, even when reproducing an optical disc having a plurality of areas having different characteristics on a medium such as a recording area and a header area like a DVD-RAM disc, By operating a direct current removing circuit having different time constants in the above region, the direct current component of the reproduction signal can be removed, and the reproduction performance and the ID acquisition rate can be improved.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the present embodiment, the configuration using the waveform equalization circuit 11 and the maximum likelihood decoding circuit 15 has been described. However, the first DC removal is performed without using the waveform equalization circuit 11 and the maximum likelihood decoding circuit 15. It is also possible to configure only the circuit 13a and the second DC removal circuit 13b.

  The present invention relates to a processing circuit of an optical disk apparatus that optically reproduces or records / reproduces a signal from a disk, and there are a plurality of areas having different characteristics on a medium such as a recording area and a header area as in a DVD-RAM disk. The present invention can be applied to a processing device for reproducing an optical disc.

It is a block diagram which shows the structure of the processing circuit of the optical disk apparatus based on one embodiment of this invention. It is a block diagram which shows the structure of the PLL circuit of the optical disk apparatus containing the processing circuit of the optical disk apparatus which concerns on one embodiment of this invention. It is a block diagram which shows the structure of the direct current | flow removal circuit of the processing circuit of the optical disk apparatus based on one embodiment of this invention. It is explanatory drawing for demonstrating the detection state of the direct current | flow removal circuit of the processing circuit of the optical disk apparatus based on one embodiment of this invention. It is explanatory drawing for demonstrating operation | movement of each switch of the processing circuit of the optical disk apparatus based on one embodiment of this invention. It is explanatory drawing for demonstrating the structure of DVD-RAM handled with the processing circuit of the optical disk apparatus based on one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Disk, 2a ... Clamper, 2b ... Turntable, 3 ... Objective lens, 4 ... Pickup, 5 ... Thread motor, 6 ... Spindle motor, 7 ... Signal processing circuit, 8 ... Servo circuit, 9 ... AD converter, 10 ... Phase synchronization circuit (PLL circuit), 11... Waveform equalization circuit, 12a... Switch a, 12b... Switch b, 12c... Switch c, 13a. 1st time constant, 14b 2nd time constant, 15 maximum likelihood decoding circuit, 16 demodulation / error correction circuit (demodulation circuit), 20 phase error detection circuit, 21 loop filter, 22 voltage control Oscillator (VCO), 30... Zero cross detection circuit, 31a, 31b... Subtractor, 32a, 32b... Multiplier, 33.

Claims (5)

A processing circuit of an optical disc apparatus that includes an optical pickup for focusing a laser beam on a disc and optically reproduces or records / reproduces the disc,
An analog-to-digital converter that performs analog-to-digital conversion of an analog input signal reproduced from the disk with a predetermined clock;
A first DC removal circuit that removes a DC component of the signal analog-to-digital converted by the analog-to-digital converter using a first time constant;
A second DC removal circuit that removes a DC component of the signal analog-digital converted by the analog-digital converter using a second time constant;
A first switch for switching and outputting an output signal of the first DC removal circuit and an output signal of the second DC removal circuit based on a switching signal corresponding to the structure of the disk;
A processing circuit for an optical disc apparatus, comprising: a demodulation circuit that demodulates an output signal of the first switch. A processing circuit of an optical disc apparatus that includes an optical pickup for focusing a laser beam on a disc and optically reproduces or records / reproduces the disc,
An analog-to-digital converter that performs analog-to-digital conversion of an analog input signal reproduced from the disk with a predetermined clock;
A waveform equalization circuit for equalizing the waveform of the signal analog-digital converted by the analog-digital converter;
A first direct current removal circuit for removing a direct current component of the signal whose waveform is equalized by the waveform equalization circuit using a first time constant;
A second DC removal circuit for removing a DC component of the signal whose waveform is equalized by the waveform equalization circuit using a second time constant;
A first switch for switching and outputting an output signal of the first DC removal circuit and an output signal of the second DC removal circuit based on a switching signal corresponding to the structure of the disk;
A processing circuit for an optical disc apparatus, comprising: a demodulation circuit that demodulates an output signal of the first switch. In the processing circuit of the optical disk device according to claim 2,
A processing circuit for an optical disc apparatus, comprising: a maximum likelihood decoding circuit that performs maximum likelihood decoding of an output signal of the first switch and outputs the signal to the demodulation circuit. In the processing circuit of the optical disk device according to claim 3,
A second switch for switching and outputting an output signal of the waveform equalization circuit and an output signal of the first switch based on an ON / OFF signal corresponding to the reproduction state of the disc;
The processing circuit for an optical disc apparatus, wherein the maximum likelihood decoding circuit performs maximum likelihood decoding on an output signal of the second switch and outputs the signal to the demodulation circuit. A signal processing method for an optical disc apparatus comprising an optical pickup for focusing a laser beam on a disc and optically reproducing or recording / reproducing the disc,
An analog input signal reproduced from the disk is converted from analog to digital with a predetermined clock, and a DC component of the analog / digital converted signal is converted into a first time constant based on a switching signal corresponding to the structure of the disk. Alternatively, the signal processing method of the optical disc apparatus, wherein the signal is removed using the second time constant and the signal from which the DC component is removed is demodulated.

Images