JP2008102984A - Reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an influence of reproduced signals superimposed on the wobble signals with a simple configuration. <P>SOLUTION: This reproducing device has a light receiving means to receive the laser light returning from the recording track meandering on a disk recording medium and to divide it into two in the tangential direction of the record tracks to output two signals, a signal generator to detect a difference between two output signals from the light receiving means and to output wobble signals matching the meandering frequency of the track, and a changing means to find out the correlation between the difference of the two output signals from the light receiving means and their addition and to relatively change the two output signals from the light receiving means based on the correlation detection result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reproducing apparatus, and more particularly to an apparatus for reproducing a signal from a disk-shaped recording medium.

  In recent years, apparatuses for recording and reproducing digital data on a high-density recording disk such as a DVD have appeared.

  A meandering track is formed on the recording surface of a recording disk such as a DVD-R or DVD-RW. When data is recorded on these disks, a recording clock is generated by multiplying the wobble signal according to the wobble of the recording track.

  Also, land pre-pit information for detecting address information is detected from a predetermined position of the wobble signal.

  Therefore, it is important to generate a high quality wobble signal.

  When data is additionally recorded on a recorded disc, it is necessary to generate a wobble signal by irradiating a beam onto a data recorded track before the additional recording start position. At this time, the tracking of the pickup is controlled so that the beam spot follows the meandering of the recording track.

  When data is reproduced, the reflected light of the beam irradiated on the disk is received by a plurality of divided photodetectors, and the output signal is extracted.

  At this time, an output obtained by adding the outputs of the detectors is taken out as an HF signal for data detection. Since the HF signal is an addition signal of each detector, there is no possibility that errors in the reproduced data will increase remarkably even when the beam spot is off the recording track to some extent.

  For this reason, the pickup is also controlled so that the beam spot follows the track to the extent that the error in the reproduction data does not increase.

  On the other hand, since the wobble signal is generated using the difference between the beam detector outputs across the track, if the beam spot does not accurately follow the track, the HF signal is superimposed on the wobble signal as noise.

Therefore, a configuration is also conceivable in which the level of the output from each detector is detected and adjusted so that the level becomes constant, and then the difference between them is obtained (for example, see Patent Document 1).
JP 2002-117536 A

  As in Patent Document 1, it is possible to improve the quality of the wobble signal by obtaining the difference after adjusting the output level of each photodetector.

  However, this requires a plurality of level adjustment circuits (AGC circuits) to adjust the output levels of the plurality of photodetectors, leading to an increase in cost.

  An object of the present invention is to solve such problems and to provide an apparatus capable of suppressing a noise component due to an HF signal superimposed on a wobble signal with a simple configuration.

  The reproducing apparatus according to the present invention includes an irradiating means for irradiating a laser to a meandering recording track on a disk-shaped recording medium; Light receiving means for receiving light divided into two and outputting two light reception result signals; and a wobble having a frequency corresponding to the meandering frequency of the recording track by detecting a difference between the two output signals from the light receiving means A signal generating means for generating a signal, and detecting a correlation between a difference between two output signals from the light receiving means and a result of adding the two output signals from the light receiving means, and based on the correlation detection result, the light receiving means Changing means for relatively changing the values of the two output signals from the signal, and the signal generating means detects a difference between the two output signals changed by the changing means. And the.

  According to the present invention, it is possible to suppress the influence of a reproduction signal component superimposed on a wobble signal with a simple configuration.

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

  FIG. 1 is a diagram showing a configuration of a recording / reproducing apparatus as an embodiment of the present invention.

  In FIG. 1, D is an optical disk such as a DVD-R, 101 is an objective lens, 102 is a beam splitter, 103 is a light receiving sensor, 104 is a signal generation circuit, and 105 is a reproduction data processing circuit. Further, 106 is an inverting circuit, 107 and 108 are switches, 109 and 110 are A / D converters, 111 and 112 are filters, and 113 and 114 are multipliers. Reference numeral 115 denotes an RMS conversion circuit, 116 denotes a gain control circuit, 117 denotes a loop filter, 118 denotes a VCO, 119 denotes a PLL, and 120 denotes a counter. Reference numeral 121 denotes a strategy circuit, 122 denotes a recording data processing circuit, 123 denotes a laser driver, and 124 denotes a laser diode.

  In FIG. 1, at the time of recording, image and audio data added from an input terminal (not shown) to the recording data generation circuit 122 is compression-encoded according to an encoding method such as MPEG2. Further, the data is converted into a form suitable for recording and output to the strategy circuit 121. The strategy circuit 121 controls the light emission procedure of the laser diode by the laser driver 123 according to the mark length of the recording data. Then, laser light is emitted from the laser diode 124 to the disk D by the laser driver 123, and data is recorded.

  At the time of reproduction, the disk D is irradiated with a low-power laser beam from the laser diode 124. The laser light emitted from the laser diode 124 is focused on the disk D through the beam splitter 102 and the objective lens 101, and the beam is irradiated onto the recording track.

  Then, the laser light reflected by the disk D passes through the objective lens 101, is bent by the beam splitter 102, and enters the light receiving sensor 103.

  The state of the light receiving sensor 103 is shown in FIG.

  As shown in FIG. 2, in the present embodiment, the light receiving sensor A201 is composed of four light receiving sensors A201 to D204, and is arranged at the illustrated position with respect to the track 205 on the disk D. That is, the light receiving sensor A201 and the light receiving sensor D204, and the light receiving sensor B202 and the light receiving sensor C203 are arranged so as to detect the reflected light from the disk D in two in the tangential direction of the track. An output A + D obtained by adding the outputs of the sensors A201 and D204 and an output B + C obtained by adding the outputs of the sensors B202 and C203 are outputs corresponding to the reflected light divided into two.

  Each of the sensors 201 to 204 of the light receiving sensor 103 converts the incident beam into a voltage and outputs the voltage to the signal generation circuit 104. The signal generation circuit 104 sends a signal (HF signal) obtained by adding the outputs of the four sensors to the reproduction data processing circuit 105. The reproduction data processing circuit 105 detects reproduction data based on the signal from the signal generation circuit 105 and decodes it to obtain original image and audio data.

  Further, the signal generation circuit 104 generates a signal corresponding to (A + D) − (B + D) from the outputs of the four sensors shown in FIG. 2, and outputs the signal to the inverting circuit 106 and the switches 107 and 108 as a wobble signal. . The wobble signal generation processing by the signal generation circuit 104 will be described later.

  The sign inversion circuit 106 inverts the sign of the input wobble signal, generates a signal corresponding to (B + C) − (A + D), and applies the signal to one terminal of the switches 107 and 108. The switches 107 and 108 are switched according to the selection signal from the counter 120.

  The counter 120 counts 186 a recording / reproducing clock (for example, the frequency is 52.32 MHz at the time of recording / reproducing at twice the standard speed of a DVD), thereby generating a rectangular sine wave corresponding to the wobble frequency. Generate cosine wave. These sine wave and cosine wave are applied to the switches 107 and 108, respectively.

  The relationship between the wobble signal output from the signal generation circuit 104 and the rectangular sine wave and cosine wave output from the counter 120 will be described with reference to FIG.

  In FIG. 4, 401 is a wobble signal output from the signal generation circuit 104, 402 is a rectangular cosine wave output from the counter 120 and output to the switch 108, and 403 is an output of the switch 108. FIG. 4A shows a case where the input wobble signal matches the phase of the cosine wave generated by the counter 120. 4B is a diagram showing a case where the phase of the counter 120 is delayed, and FIG. 4C is a diagram showing a case where the phase of the counter 120 is advanced.

  When the phase of the counter 120 is delayed, as shown by 403b, there are many portions where the output of the switch 108 exceeds the dotted line as compared with 403a, and the average becomes positive. On the contrary, when the phase of the counter 120 is advanced as compared with the wobble signal, the positive portion exceeding the dotted line is reduced as shown by 403c, and becomes negative on average.

  In this way, the output of the switch 108 can be handled as a phase error signal between the wobble signal and the counter 120.

  Reference numeral 405 denotes a rectangular sine wave output from the counter 120 and added to the switch 107, and reference numeral 406 denotes an output of the switch 107. The waveforms 403 and 406 are, for example, the result of folding a wobble signal having a frequency of 280 kHz into a direct current on two orthogonal axes during double-speed playback of a DVD. Then, as will be described later, the amplitude value can be obtained by taking the root mean square of these two waveforms 403 and 406.

  The outputs of the switches 107 and 108 are converted into 1-bit digital data by the A / D converters 109 and 110, respectively, and added to the sampling conversion filters 111 and 112 in the subsequent stage. The sampling conversion filters 111 and 112 convert the input 1-bit digital data into multi-bit digital data having a low sampling rate by averaging in the time direction, and add the results to the multipliers 113 and 1145, respectively. .

  The outputs of the multipliers 113 and 114 are applied to the RMS conversion circuit 115. The output of multiplier 114 is also applied to loop filter 117. An RMS (Root Mean Square) conversion circuit 115 obtains an RMS value by taking the root mean square of the outputs of the multipliers 113 and 114, and outputs the result to the AGC circuit 116. The AGC circuit 116 integrates the error between the added RMS value and the reference value, and feeds back the integration result to the multipliers 113 and 114, thereby performing AGC control that keeps the gain constant.

  The loop filter 117 averages the applied phase error signal to convert it into a frequency error signal, and adds the result to the digital VCO 118. The VCO 118 generates a sine wave according to the added frequency information and applies it to the PLL 119. Here, as an example of numerical values, as a clock applied to the VCO 118, for example, a 108 MHz clock generated based on a crystal is given, and a sine wave of about 6.54 MHz is generated from the digital VCO 118.

  The PLL 119 multiplies the added sine wave near 6.54 MHz by 8 to generate a 52.32 MHz clock.

  The clock generated by the PLL 119 is added as a recording clock to the strategy circuit 121, the recording data generation circuit 122, and the counter 120.

  Next, wobble signal generation processing by the signal generation circuit 104 in the present embodiment will be described.

  FIG. 3 is a diagram illustrating a configuration of a wobble signal generation unit in the signal generation circuit 104.

  In the figure, reference numerals 301, 302, 303, and 304 denote input terminals to which outputs of the sensors A201 to D204 in FIG. 2 are supplied, and reference numerals 305, 306, 307, and 311 denote adders. Reference numeral 308 denotes a sign inverting circuit, and reference numeral 309 denotes a combining unit that combines the output of the inverting circuit 308 and the output of the adder 305. The synthesizer 309 takes the form of a resistor circuit in the figure, but can adopt a simple analog multiplier configuration. Reference numeral 310 denotes a multiplier, 311 denotes an LPF, and 312 denotes an output terminal.

  In FIG. 3, the adder 305 generates a signal corresponding to (A + D) and the adder 306 generates a signal corresponding to (B + C), and the adder 307 generates a signal corresponding to (A + B + C + D). In the sign inverting circuit 308, a signal of − (B + C) is calculated. The synthesizer 309 synthesizes the output of the adder 305 and the output from the inverting circuit 308 and outputs a signal corresponding to (A + D) − (B + C). In the present embodiment, the composition ratio α by the composition unit 309 is changed by an output from the LPF 311 as described later.

Specifically, the composition ratio α takes a value between 0 and 1, and the output of the composition unit 309 is
α × (A + D) − (1−α) × (B + C)
It is represented by

  The output of the combining unit 309 is output from the terminal 312 as a signal (A + D) − (B + C). Further, the output of the combining unit 309 is output to the multiplier 310. The signal (A + B + C + D) from the adder 307 is added to the other input of the multiplier 310. Here, (A + B + C + D) represents an HF signal.

  Multiplier 310 multiplies the output of combining section 309 and the output from adder 307 (A + B + C + D), and outputs the result to low-pass filter (LPF) 311. The LPF 311 averages the output of the multiplier 310 and sets the synthesis ratio α based on the result.

  Here, the relationship between the HF signal and the wobble signal will be described.

  In the present embodiment, four sensors are arranged as shown in FIG. The HF signal is an output of (A + B + C + D), and the wobble signal is (A + D) − (B + C), that is, a difference signal. Therefore, when the beam is accurately irradiated on the center of the track, the HF signal component is not superimposed on the (A + D)-(B + C) output, and only the wobble signal component should be detected.

  Therefore, in the present embodiment, by multiplying the (A + D)-(B + C) signal (A + B + C + D) signal, which is the output of the combining unit 309, the HF included in the (A + D)-(B + C) signal. The amount of signal component is detected.

  Here, FIG. 5A shows a case where the HF signal component included in the output of the synthesis unit 309 and the HF signal output from the adder 307 are in phase. In the figure, 501a is the output of the combining unit 309, 502a is the HF signal, and the output of the multiplier 310 has a positive average value as indicated by 503a. Here, when the average value of the inputs of the multiplier 310 is positive, the output is also positive. The output of the LPF 311 works to reduce α. As a result, the ratio of the (A + D) signal that is the in-phase component of the HF signal decreases, and the − (B + C) component that is the anti-phase component increases, thereby minimizing the leakage of the HF signal.

  FIG. 3B shows a case where the HF signal component included in the output of the combining unit 309 and the HF signal output from the adder 307 are in reverse phase. When the phase is reversed, as a result, the output of the multiplier 310 becomes negative as shown in 503b, so that the output of the LPF 311 works to increase α. As a result, the leakage of the HF signal can be minimized.

  As described above, according to the present embodiment, based on the correlation between the HF signal from the light receiving sensor and the difference signal of the light receiving sensor for generating the wobble signal, the ratio of the two signals from the light receiving sensor is calculated. It has changed relatively.

  Therefore, it is possible to suppress the influence of the HF signal on the wobble signal with a simple configuration.

  In the above-described embodiment, the multiplier 310 detects the correlation between the output of the synthesizing unit 309 and the HF signal, but it is of course possible to adopt other configurations. Further, although the correlation detection result is averaged by the LPF and the synthesis ratio is controlled, an averaged output can be obtained with another configuration.

It is a figure which shows the structure of the recording / reproducing apparatus in embodiment of this invention. It is a figure which shows the structure of a light reception sensor. It is a figure which shows the structure of a signal generation circuit. It is a figure which shows the waveform of a reproduction signal. It is a figure which shows the waveform of a reproduction signal.

Claims (6)

Irradiation means for irradiating a laser to a meandering recording track on a disk-shaped recording medium;
Light receiving means for receiving the reflected light of the laser from the disk-shaped recording medium divided into two with respect to the tangential direction of the recording track, and outputting two light reception result signals;
Signal generating means for detecting a difference between two output signals from the light receiving means and generating a wobble signal having a frequency corresponding to the meandering frequency of the recording track;
The correlation between the difference between the two output signals from the light receiving means and the addition result of the two output signals from the light receiving means is detected, and based on the correlation detection result, the values of the two output signals from the light receiving means are calculated. And a change means that changes relatively,
The signal generating means detects a difference between the two output signals changed by the changing means.   The changing unit includes a multiplying unit that multiplies a difference between the two output signals from the light receiving unit and an addition result of the two output signals from the light receiving unit. 2. The reproducing apparatus according to claim 1, wherein the values of the two output signals are relatively changed based on the values.   The signal generating unit synthesizes the sign inverting unit that inverts the sign of one of the two output signals from the light receiving unit, and the other signal of the two output signals and the output signal from the sign inverting unit. The reproducing apparatus according to claim 1, wherein the changing unit changes a combining ratio of the combining unit based on the correlation.   The changing means detects a degree of correlation between the addition output of the two output signals and the output signal from the sign inverting unit, or a degree of correlation between the addition output of the two output signals and the other signal. The combination ratio is changed so that the ratio of the output signal from the sign inverting unit decreases as the correlation between the sum output of the two output signals and the output signal from the code inverting unit increases. 4. The reproducing apparatus according to claim 3, wherein the combination ratio is changed so that the ratio of the other signal becomes lower as the correlation between the added output of the signal and the other signal becomes higher.   Based on the correlation detection result, the changing means sets the values of the two output signals relative to each other so that the added output component of the two output signals included in the difference between the two output signals from the light receiving means decreases. 2. A reproducing apparatus according to claim 1, wherein the reproducing apparatus is changed in a stepwise manner.   The changing means increases the value of the one signal with respect to the value of the other signal as the correlation between one of the two output signals from the light receiving means and the added output of the two output signals increases. The reproducing apparatus according to claim 1, wherein the reproducing apparatus is relatively small.

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